First-in-Human Study of the Ataxia Telangiectasia and Rad3-Related (ATR) Inhibitor Tuvusertib (M1774) as Monotherapy in Patients with Solid Tumors

PURPOSE

Tuvusertib (M1774) is a potent, selective, orally administered ataxia telangiectasia and Rad3-related (ATR) protein kinase inhibitor. This first-in-human study (NCT04170153) evaluated safety, tolerability, maximum tolerated dose (MTD), recommended dose for expansion (RDE), pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of tuvusertib monotherapy.

PATIENTS AND METHODS

Ascending tuvusertib doses were evaluated in 55 patients with metastatic or locally advanced unresectable solid tumors. A safety monitoring committee determined dose escalation based on PK, PD, and safety data guided by a Bayesian 2-parameter logistic regression model. Molecular responses (MR) were assessed in circulating tumor DNA samples.

RESULTS

Most common grade ≥3 treatment-emergent adverse events were anemia (36%), neutropenia, and lymphopenia (both 7%). Eleven patients experienced dose-limiting toxicities, most commonly grade 2 (n = 2) or 3 (n = 8) anemia. No persistent effects on blood immune cell populations were observed. The RDE was 180 mg tuvusertib QD (once daily), 2 weeks on/1 week off treatment, which was better tolerated than the MTD (180 mg QD continuously). Tuvusertib median time to peak plasma concentration ranged from 0.5 to 3.5 hours and mean elimination half-life from 1.2 to 5.6 hours. Exposure-related PD analysis suggested maximum target engagement at ≥130 mg tuvusertib QD. Tuvusertib induced frequent MRs in the predicted efficacious dose range; MRs were enriched in patients with radiological disease stabilization, and complete MRs were detected for mutations in ARID1A, ATRX, and DAXX. One patient with platinum- and PARP inhibitor-resistant BRCA wild-type ovarian cancer achieved an unconfirmed RECIST v1.1 partial response.

CONCLUSIONS

Tuvusertib demonstrated manageable safety and exposure-related target engagement. Further clinical evaluation of tuvusertib is ongoing.

Datopotamab Deruxtecan in Advanced or Metastatic HR+/HER2- and Triple-Negative Breast Cancer: Results From the Phase I TROPION-PanTumor01 Study

PURPOSE

Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized antitrophoblast cell-surface antigen 2 (TROP2) monoclonal antibody linked to a potent, exatecan-derived topoisomerase I inhibitor payload via a plasma-stable, selectively cleavable linker.

PATIENTS AND METHODS

TROPION-PanTumor01 (ClinicalTrials.gov identifier: NCT03401385) is a phase I, dose-escalation, and dose-expansion study evaluating Dato-DXd in patients with previously treated solid tumors. The primary study objective was to assess the safety and tolerability of Dato-DXd. Secondary objectives included evaluation of antitumor activity and pharmacokinetics. Results from patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC) or triple-negative BC (TNBC) are reported.

RESULTS

At data cutoff (July 22, 2022), 85 patients (HR+/HER2- BC = 41, and TNBC = 44) had received Dato-DXd. The objective response rate by blinded independent central review was 26.8% (95% CI, 14.2 to 42.9) and 31.8% (95% CI, 18.6 to 47.6) for patients with HR+/HER2- BC and TNBC, respectively. The median duration of response was not evaluable in the HR+/HER2- BC cohort and 16.8 months in the TNBC cohort. The median progression-free survival in patients with HR+/HER2- BC and TNBC was 8.3 and 4.4 months, respectively. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 100% and 41.5% of patients with HR+/HER2- BC and 100% and 52.3% of patients with TNBC. Stomatitis was the most common TEAE (any grade, grade ≥3) in both HR+/HER2- BC (82.9%, 9.8%) and TNBC (72.7%, 11.4%) cohorts.

CONCLUSION

In patients with heavily pretreated advanced HR+/HER2- BC and TNBC, Dato-DXd demonstrated promising clinical activity and a manageable safety profile. Dato-DXd is currently being evaluated in phase III studies.

A phase I study to evaluate the safety, pharmacokinetics, and pharmacodynamics of PF-06939999 (PRMT5 inhibitor) in patients with selected advanced or metastatic tumors with high incidence of splicing factor gene mutations

BACKGROUND

Protein arginine methyltransferase 5 (PRMT5) methylates multiple substrates dysregulated in cancer, including spliceosome machinery components. PF-06939999 is a selective small-molecule PRMT5 inhibitor.

PATIENTS AND METHODS

This phase I dose-escalation and -expansion trial (NCT03854227) enrolled patients with selected solid tumors. PF-06939999 was administered orally once or twice a day (q.d./b.i.d.) in 28-day cycles. The objectives were to evaluate PF-06939999 safety and tolerability to identify maximum tolerated dose (MTD) and recommended part 2 dose (RP2D), and assess pharmacokinetics (PK), pharmacodynamics [changes in plasma symmetric dimethylarginine (SDMA) levels], and antitumor activities.

RESULTS

In part 1 dose escalation, 28 patients received PF-06939999 (0.5 mg q.d. to 6 mg b.i.d.). Four of 24 (17%) patients reported dose-limiting toxicities: thrombocytopenia (n = 2, 6 mg b.i.d.), anemia (n = 1, 8 mg q.d.), and neutropenia (n = 1, 6 mg q.d.). PF-06939999 exposure increased with dose. Steady-state PK was achieved by day 15. Plasma SDMA was reduced at steady state (58%-88%). Modulation of plasma SDMA was dose dependent. No MTD was determined. In part 2 dose expansion, 26 patients received PF-06939999 6 mg q.d. (RP2D). Overall (part 1 + part 2), the most common grade ≥3 treatment-related adverse events included anemia (28%), thrombocytopenia/platelet count decreased (22%), fatigue (6%), and neutropenia (4%). Three patients (6.8%) had confirmed partial response (head and neck squamous cell carcinoma, n = 1; non-small-cell lung cancer, n = 2), and 19 (43.2%) had stable disease. No predictive biomarkers were identified.

CONCLUSIONS

PF-06939999 demonstrated a tolerable safety profile and objective clinical responses in a subset of patients, suggesting that PRMT5 is an interesting cancer target with clinical validation. However, no predictive biomarker was identified. The role of PRMT5 in cancer biology is complex and requires further preclinical, mechanistic investigation to identify predictive biomarkers for patient selection.

Phase I Study of GS-3583, a FLT3 Agonist Fc Fusion Protein, in Patients with Advanced Solid Tumors

PURPOSE

GS-3583, a FMS-like tyrosine kinase 3 (FLT3) agonist Fc fusion protein, expanded conventional dendritic cells (cDCs) in the periphery of healthy volunteers, suggesting potential for GS-3583 to increase cDCs in the tumor microenvironment and promote T cell-mediated antitumor activity in cancer patients. This phase Ib open-label study assessed GS-3583 in adults with advanced solid tumors.

PATIENTS AND METHODS

Multiple escalating doses of GS-3583 (standard 3+3 design) were administered intravenously on days 1 and 15 of cycle 1 and day 1 of each subsequent 28-day cycle for up to 52 weeks. Dose-limiting toxicity (DLT) was evaluated during the first 28 days of GS-3583 at each dose level.

RESULTS

Thirteen participants enrolled in 4 dose-escalation cohorts, after which the study was terminated following safety review. Median (range) age was 71 (44-79), and 7 (54%) participants were male. There were no DLTs. Seven participants had grade ≥3 AEs; 2 participants had grade 5 AEs, including a second primary malignancy (acute myeloid leukemia) considered treatment-related. Dose-dependent increase in GS-3583 serum exposure was observed in the dose range of 2-20 mg with GS-3583 accumulation at higher dose levels. Expansions of cDCs occurred at all 4 doses with a dose-dependent trend in the durability of the cDC expansion.

CONCLUSIONS

GS-3583 was relatively well tolerated and induced dose-dependent expansion of cDCs in the periphery of patients with advanced solid tumors. However, development of a second primary malignancy provides a cautionary tale for the FLT3 agonist mechanism.

First-in-Human, Phase I Dose-Escalation and Dose-Expansion Study of Trophoblast Cell-Surface Antigen 2-Directed Antibody-Drug Conjugate Datopotamab Deruxtecan in Non-Small-Cell Lung Cancer: TROPION-PanTumor01

PURPOSE

This first-in-human, dose-escalation and dose-expansion study evaluated the safety, tolerability, and antitumor activity of datopotamab deruxtecan (Dato-DXd), a novel trophoblast cell-surface antigen 2 (TROP2)-directed antibody-drug conjugate in solid tumors, including advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Adults with locally advanced/metastatic NSCLC received 0.27-10 mg/kg Dato-DXd once every 3 weeks during escalation or 4, 6, or 8 mg/kg Dato-DXd once every 3 weeks during expansion. Primary end points were safety and tolerability. Secondary end points included objective response rate (ORR), survival, and pharmacokinetics.

RESULTS

Two hundred ten patients received Dato-DXd, including 180 in the 4-8 mg/kg dose-expansion cohorts. This population had a median of three prior lines of therapy. The maximum tolerated dose was 8 mg/kg once every 3 weeks; the recommended dose for further development was 6 mg/kg once every 3 weeks. In patients receiving 6 mg/kg (n = 50), median duration on study, including follow-up, and median exposure were 13.3 and 3.5 months, respectively. The most frequent any-grade treatment-emergent adverse events (TEAEs) were nausea (64%), stomatitis (60%), and alopecia (42%). Grade ≥3 TEAEs and treatment-related AEs occurred in 54% and 26% of patients, respectively. Interstitial lung disease adjudicated as drug-related (two grade 2 and one grade 4) occurred in three of 50 patients (6%). The ORR was 26% (95% CI, 14.6 to 40.3), and median duration of response was 10.5 months; median progression-free survival and overall survival were 6.9 months (95% CI, 2.7 to 8.8 months) and 11.4 months (95% CI, 7.1 to 20.6 months), respectively. Responses occurred regardless of TROP2 expression.

CONCLUSION

Promising antitumor activity and a manageable safety profile were seen with Dato-DXd in heavily pretreated patients with advanced NSCLC. Further investigation as first-line combination therapy in advanced NSCLC and as monotherapy in the second-line setting and beyond is ongoing.

Results of an open-label phase 1b study of the ERK inhibitor MK-8353 plus the MEK inhibitor selumetinib in patients with advanced or metastatic solid tumors

AIM

We evaluated MK-8353 (small molecule inhibitor of extracellular signal-regulated kinase 1/2) plus selumetinib (mitogen-activated extracellular signal-regulated kinase 1/2 inhibitor) in patients with advanced solid tumors.

METHODS

This phase 1b, open-label, dose-escalation study (NCT03745989) enrolled adults with histologically/cytologically documented, locally advanced/metastatic solid tumors. MK-8353/selumetinib dose combinations were intended to be investigated in sequence: 50/25, 100/50, 150/75, 200/75, 200/100, and 250/100. Each agent was administered orally BID 4 days on/3 days off in repeating cycles every 21 days. Primary objectives were safety and tolerability and to establish preliminary recommended phase 2 doses for combination therapy.

RESULTS

Thirty patients were enrolled. Median (range) age was 61.5 (26-78) years and 93% had received previous cancer therapy. Among 28 patients in the dose-limiting toxicities [DLT]-evaluable population, 8 experienced DLTs: 1/11 (9%) in the MK-8353/selumetinib 100/50-mg dose level experienced a grade 3 DLT (urticaria), and 7/14 (50%) in the 150/75-mg dose level experienced grade 2/3 DLTs (n = 2 each of blurred vision, retinal detachment, vomiting; n = 1 each of diarrhea, macular edema, nausea, retinopathy). The DLT rate in the latter dose level exceeded the prespecified target DLT rate (~30%). Twenty-six patients (87%) experienced treatment-related adverse events (grade 3, 30%; no grade 4/5), most commonly diarrhea (67%), nausea (37%), and acneiform dermatitis (33%). Three patients (10%) experienced treatment-related adverse events leading to treatment discontinuation. Best response was stable disease in 14 patients (n = 10 with MK-8353/selumetinib 150/75 mg).

CONCLUSION

MK-8353/selumetinib 50/25 mg and 100/50 mg had acceptable safety and tolerability, whereas 150/75 mg was not tolerable. No responses were observed.

Abstract P6-10-03: Datopotamab Deruxtecan (Dato-DXd) in Advanced Triple-Negative Breast Cancer (TNBC): Updated Results From the Phase 1 TROPION-PanTumor01 Study

Background: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate (ADC) consisting of a humanized anti-TROP2 IgG1 mAb covalently linked to a highly potent topoisomerase I (Topo I) inhibitor payload via a stable, tumor selective, tetrapeptide-based cleavable linker. Dato-DXd has previously shown encouraging activity in heavily pretreated patients (pts) with metastatic TNBC (Krop, SABCS 2021). Here we report updated results from the TROPION-PanTumor01 study in pts with advanced/metastatic TNBC. Methods: TROPION-PanTumor01 (NCT03401385) is a phase 1, multicenter, open-label, 2-part dose-escalation/expansion study evaluating Dato-DXd in previously treated pts with solid tumors. Based on previous clinical and exposure-response results from pts with NSCLC, Dato-DXd 6 mg/kg IV Q3W is being evaluated in pts with advanced TNBC that relapsed/progressed on standard therapies; 2 pts received 8 mg/kg prior to selection of 6 mg/kg. The primary objectives were safety and tolerability. Tumor responses, including objective response rate (ORR; complete response [CR] + partial response [PR]) and disease control rate (DCR; CR + PR + stable disease [SD]), were assessed per RECIST v1.1 by blinded independent central review. Results: As of April 29, 2022, 44 pts received Dato-DXd (median follow-up, 16.6 mo [range, 13-22]) at the time of data cutoff. The primary cause of treatment discontinuation was disease progression (86%; PD or clinical progression), and 4 pts are still receiving therapy. Median age was 53 y (range, 32-82); 32% had de novo metastatic disease. Pts were heavily pretreated with a median of 3 (range, 1-10) prior regimens in the metastatic setting. Prior treatments included taxanes (91%), anthracyclines (75%), capecitabine (61%), platinum (52%), immunotherapy (43%), Topo I inhibitor–based ADC therapy (32%), and PARPi (18%). Treatment-emergent adverse events (TEAEs; all cause) occurred in 100% (any grade) and 50% (grade ≥3) of pts, respectively. Most common TEAEs (any grade, grade ≥3) were stomatitis (73%, 11%), nausea (66%, 2%), vomiting (39%, 5%), fatigue (34%, 7%), and alopecia (36%, 0%). One pt had grade 3 decreased neutrophil count; no cases of interstitial lung disease (ILD) or grade ≥3 diarrhea were observed. Serious TEAEs were reported in 9 pts (20%); no deaths associated with adverse events (AEs) were observed. Dose reductions occurred in 8 pts (18%) due to stomatitis (n=3), fatigue (n=2), dry eye (n=1), retinal exudates (n=1), and dysgeusia (n=1); 12 pts (27%) delayed treatment due to stomatitis (n=5), dry eye (n=1), keratitis (n=1), blurred vision (n=1), fatigue (n=1), bronchitis (n=1), skin infection (n=1), musculoskeletal chest pain (n=1), dysgeusia (n=1), chronic obstructive pulmonary disease (n=1), and dyspnea (n=1; >1 AE per pt). One pt (2%) discontinued treatment due to grade 1 pneumonitis (which was centrally adjudicated as not ILD). ORR in all pts was 32% (1 CR, 13 PRs), DCR was 80% (35/44), and clinical benefit rate (CR + PR + SD ≥6 mo) was 34% (15/44). Median duration of response was not yet reached; median progression-free survival (mPFS) was 4.3 mo (95% CI, 3.0-7.3), and median overall survival (mOS) was 12.9 mo (95% CI, 10.1-14.7). In the subset of pts without prior Topo I inhibitor–based ADC therapy and with measurable disease at baseline, ORR was 44% (12/27). Among all pts without prior Topo I inhibitor–based ADC therapy (n=30), mPFS was 7.3 mo (95% CI, 3.0-NE), and mOS was 14.3 mo (95% CI, 10.5-NE). Conclusions: Dato-DXd continues to demonstrate encouraging and durable antitumor activity, along with a manageable safety profile, in heavily pretreated pts with metastatic TNBC. Based on these findings, the phase 3 randomized TROPION-Breast02 (NCT05374512) trial comparing Dato-DXd vs chemotherapy as 1L therapy for pts with metastatic TNBC is currently underway.

Citation Format: Aditya Bardia, Ian Krop, Funda Meric-Bernstam, Anthony W. Tolcher, Toru Mukohara, Aaron Lisberg, Toshio Shimizu, Erika Hamilton, Alexander I. Spira, Kyriakos P. Papadopoulos, Jonathan Greenberg, Wen Gu, Fumiaki Kobayashi, Hong Zebger-Gong, Yui Kawasaki, Rie Wong, Takahiro Kogawa. Datopotamab Deruxtecan (Dato-DXd) in Advanced Triple-Negative Breast Cancer (TNBC): Updated Results From the Phase 1 TROPION-PanTumor01 Study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-10-03.

Phase 1 first-in-human study of dalutrafusp alfa, an anti-CD73-TGF-β-trap bifunctional antibody, in patients with advanced solid tumors

BACKGROUND

Cluster of differentiation (CD)73-adenosine and transforming growth factor (TGF)-β pathways are involved in abrogated antitumor immune responses and can lead to protumor conditions. This Phase 1 study (NCT03954704) evaluated the safety, pharmacokinetics, pharmacodynamics, and efficacy of dalutrafusp alfa (also known as GS-1423 and AGEN1423), a bifunctional, humanized, aglycosylated immunoglobulin G1 kappa antibody that selectively inhibits CD73-adenosine production and neutralizes active TGF-β signaling in patients with advanced solid tumors.

METHODS

Dose escalation started with an accelerated titration followed by a 3+3 design. Patients received dalutrafusp alfa (0.3, 1, 3, 10, 20, 30, or 45 mg/kg) intravenously every 2 weeks (Q2W) up to 1 year or until progressive disease (PD) or unacceptable toxicity.

RESULTS

In total, 21/22 patients received at least one dose of dalutrafusp alfa. The median number of dalutrafusp alfa doses administered was 3 (range 1-14). All patients had at least one adverse event (AE), most commonly fatigue (47.6%), nausea (33.3%), diarrhea (28.6%), and vomiting (28.6%). Nine (42.9%) patients had a Grade 3 or 4 AE; two had Grade 5 AEs of pulmonary embolism and PD, both unrelated to dalutrafusp alfa. Target-mediated drug disposition appears to be saturated at dalutrafusp alfa doses above 20 mg/kg. Complete CD73 target occupancy on B cells and CD8+ T cells was observed, and TGF-β 1/2/3 levels were undetectable at dalutrafusp alfa doses of 20 mg/kg and higher. Free soluble (s)CD73 levels and sCD73 activity increased with dalutrafusp alfa treatment. Seventeen patients reached the first response assessment, with complete response, partial response, stable disease, and PD in 0, 1 (4.8%), 7 (33.3%), and 9 (42.9%) patients, respectively.

CONCLUSIONS

Dalutrafusp alfa doses up to 45 mg/kg Q2W were well tolerated in patients with advanced solid tumors. Additional evaluation of dalutrafusp alfa could further elucidate the clinical utility of targeting CD73-adenosine and TGF-β pathways in oncology.

Trial in progress: A phase 1, first-in-human, open-label, multicenter, dose-escalation and dose-expansion study of ASP3082 in patients with previously treated advanced solid tumors and KRAS G12D mutations

TPS764

Background: Kirsten rat sarcoma (KRAS) G12D is a point mutation observed in various cancer types including pancreatic ductal cancer, colon adenocarcinoma, and lung cancers. ASP3082 is a novel small-molecule proteolysis-targeting chimeric degrader that binds to, and selectively targets, the KRAS G12D-mutated protein for degradation via recruitment of E3 ubiquitin ligase proteins. In preclinical studies, ASP3082 selectively degraded the KRAS G12D-mutated protein and showed growth inhibitory activity in KRAS G12D-mutated cancer cells but not in KRAS -wildtype cancer cells. Notable antitumor effects of ASP3082 have been demonstrated when intravenously administered weekly in mice xenografted with KRAS G12D-mutated cancer cells. Methods: This first-in-human, open-label, multicenter, phase 1 study evaluates the safety and tolerability of ASP3082 in patients with pancreatic cancer, colorectal cancer, non-small cell lung cancer or other solid tumors. Participants with unresectable, locally advanced, or metastatic solid tumor malignancy with documented KRAS G12D mutation are eligible for enrollment. Part 1 consists of dose-escalation cohorts of 3−12 patients receiving intravenous administration of ASP3082 in a 21-day cycle. Part 2 consists of random assignment of ≤20 patients into 2 cohorts with different ASP3082 dose levels to determine the recommended phase 2 dose. Additional tumor-specific expansion cohorts may enroll ≤20 participants per tumor type. Primary endpoints will evaluate safety and tolerability as noted by dose-limiting toxicities, adverse events, serious adverse events, laboratory test results, electrocardiograms, vital signs, physical exams, and Eastern Cooperative Oncology Group performance status. Secondary endpoints will evaluate objective response rate, duration of response, disease control rate per Response Evaluation Criteria in Solid Tumors version 1.1, pharmacokinetics of single and repeated doses of ASP3082, and changes in KRAS G12D in tumor samples. Exploratory objectives will evaluate potential biomarkers that may correlate with treatment outcomes. Tumor assessment follow-up will continue for ≤45 weeks or until progressive disease. Enrollment in Cohort 1 is complete, and enrollment to Cohort 2 began in September 2022. Clinical trial information: NCT05382559 .

Efficacy and safety of the MDM2–p53 antagonist BI 907828 in patients with advanced biliary tract cancer: Data from two phase Ia/Ib dose-escalation/expansion trials

543

Background: Standard-of-care treatment for advanced biliary tract cancer (BTC) is chemotherapy and outcomes remain poor; hence, there is a clinical need for effective targeted treatments. As MDM2 is a negative regulator of the tumor suppressor p53, blocking the MDM2–p53 interaction is a potential antitumor strategy. Further, preliminary data indicate that MDM2 amplification is a negative prognostic marker in BTC. The MDM2–p53 antagonist BI 907828 has shown preclinical antitumor activity in a range of malignancies and is currently being assessed in two phase Ia/Ib dose-escalation/expansion trials in patients with advanced solid tumors: as monotherapy (NCT03449381) and in combination with an anti-PD-1 antibody, ezabenlimab (NCT03964233). Here, we present data for patients with advanced BTCs in these trials. Methods: Patients in the monotherapy trial received escalating doses of BI 907828 on day 1 of 21-day cycles (q3w). Patients in the combination trial received escalating doses of BI 907828 and 240 mg ezabenlimab q3w (doublet); one patient also received the anti-LAG-3 antibody BI 754111 (a drug that has since been discontinued; triplet). Results: A total of 8 patients with BTC were enrolled in the 2 trials, 4 in the monotherapy trial and 4 in the combination trial. In the monotherapy trial, 2 patients had ampullary carcinoma (both received BI 907828 45 mg q3w), and 2 had cholangiocarcinoma (CC; 1 received BI 907828 45 mg q3w and 1 with intrahepatic CC [iCC] received 80 mg q3w). In the combination trial, 3 patients with iCC received 30 mg/45 mg BI 907828 doublet or 45 mg triplet, and 1 with gallbladder carcinoma (GBC) received BI 907828 45 mg doublet. Across both trials, 5 patients achieved PR, 2/4 in the monotherapy trial and 3/4 in the combination trial. In the monotherapy trial, the responding patients had iCC (80 mg q3w; MDM2-amplified; 73% tumor shrinkage; PFS event at 404 days) and ampullary adenocarcinoma (45 mg q3w; MDM2-amplified; 51% tumor shrinkage; ongoing, PFS censored at 255 days). In the combination trial, all 3 responding patients had MDM2-amplified biliary tract adenocarcinoma (2 iCC, 1 GBC); tumor shrinkage was 49–54%; PFS was 162–241 days. A further 2 patients (1 in each trial) achieved stable disease (SD). In the monotherapy trial, most common grade ≥3 treatment-related AEs (TRAEs) were thrombocytopenia, decreased white blood cell (WBC) count and neutropenia (2 patients each). In the combination trial, most common grade ≥3 TRAEs were anemia and decreased WBC count (3 patients each), neutropenia and thrombocytopenia (2 patients each). Conclusions: The MDM2–p53 antagonist BI 907828 has shown a manageable safety profile and encouraging preliminary efficacy in patients with BTC, with 5 PRs and 2 SD in 8 patients. A phase IIa/IIb trial of BI 907828 (45 mg q3w) in patients with BTC is planned to start recruitment at the end of 2022 (NCT05512377). Clinical trial information: NCT03449381 and NCT03964233 .

Antibody drug conjugates: The dos and don'ts in clinical development

Antibody Drug Conjugates (ADCs) entered clinical trials in the mid 1990s to selectively deliver cytotoxic chemotherapy to cancer cells with the goal to increase the antitumor activity and decrease normal tissue toxicity. Over nearly 30 years of development the ADC platform has become established with now 11 approved agents and many more in the pipeline. This review is designed to highlight some of the problems and solutions encountered in clinical development as well as provide practical instruction to both clinical investigators on the efficient protocol design for ADCs and the lessons learned.

Abstract CT029: Safety and clinical activity of single-agent ZN-c3, an oral WEE1 inhibitor, in a phase 1 trial in subjects with recurrent or advanced uterine serous carcinoma (USC)

Introduction: ZN-c3 is a selective, orally bioavailable small molecule inhibitor of WEE1, a crucial component of the G2/M cell cycle checkpoint, which prevents cells from entering mitosis to allow repair of DNA damage. ZN-c3 has demonstrated significant in vitro antitumor activity in multiple cell lines and xenograft models.

Methods: ZN-c3-001 (NCT04158336) is an open label, multicenter, Phase I dose escalation and expansion study evaluating the safety and clinical activity of ZN-c3 in subjects with advanced or metastatic solid tumors, refractory to standard therapy or for whom no standard therapy is available. Oral, daily ZN-c3 dosing was escalated from 25 mg to 450 mg once daily (QD), with a recommended phase 2 dose of 300 mg QD. Here we report preliminary safety and efficacy results for subjects with USC who received ZN-c3 at doses ≥300 mg QD.

Results: As of October 28, 2021, a total of 78 subjects were enrolled across all tumor types. For USC, there were 12 subjects who received ZN-c3 at doses ≥300 mg QD and were evaluated for safety. Median duration of treatment was 12 weeks (range, 2 - 33 weeks). The safety profile for this subgroup is comparable to the overall patient population with 11 of 12 subjects reporting at least one treatment-related adverse event (TRAE). TRAEs grades 1-4 occurring in ≥3 subjects, by decreasing frequency, included nausea, vomiting, fatigue, diarrhea, decreased appetite, dehydration, and anemia. Grade ≥3 TRAEs occurring in ≥2 subjects included anemia and thrombocytopenia. These hematologic events were limited to 2 subjects each. Nine of the 12 subjects had measurable disease and at least 1 post-baseline tumor assessment; 3 subjects (33.3%) had confirmed partial response and 5 (55.6%) had stable disease as their best overall response. Disease control rate, defined as those with complete response, partial response, and stable disease, was 88.9%. One subject with partial response achieved complete response at subsequent tumor assessment.

Conclusions: ZN-c3 appears to be safe and well-tolerated as a single agent at oral doses ≥300 mg QD and demonstrated clinical activity in subjects with recurrent or advanced USC. Safety results in these subjects were consistent with those of the full study population. The ongoing dose expansion study is enrolling USC patients. The preliminary efficacy signal will be confirmed in a dedicated phase 2 study (ZN-c3-004, NCT04814108) in this patient population.

Citation Format: Funda Meric-Bernstam, Pavani Chalsani, Hirva Mamdani, Cheng Zheng, Marcus Viana, Ruth Lambersky, Philippe Pultar, Anthony W. Tolcher. Safety and clinical activity of single-agent ZN-c3, an oral WEE1 inhibitor, in a phase 1 trial in subjects with recurrent or advanced uterine serous carcinoma (USC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT029.

A phase 1/2 dose escalation/expansion study of OR2805 alone or in combination in subjects with advanced solid tumors

TPS2693

Background: M2-like macrophages are thought to promote an immunoinhibitory environment and prevent activation and proliferation of T cells, leading to resistance to checkpoint inhibitor (CPI) therapy. OR2805 is a fully human monoclonal antibody identified in a patient who had an exceptional response to CPI. OR2805 recognizes CD163, an immunosuppressive scavenger receptor highly expressed on M2 tumor-associated macrophages (TAMs). OR2805 treatment reprograms M2 macrophages to take on an immunostimulatory, M1-like phenotype. In macrophage/T cell coculture assays, OR2805 treatment relieved the suppressive effect of M2c macrophages as demonstrated by increased T-cell proliferation and stimulation of IFN-γ and perforin release. OR2805 restored the IFN-γ production of exhausted T cells and showed a synergistic effect on cocultures treated in combination with CPI. OR2805 monotherapy demonstrated significant anti-tumor activity in lung cancer xenograft models in NSG-SGM3 mice. Relieving the immune suppression of CD163-expressing TAMs by OR2805 to improve anti-tumor T-cell responses will be evaluated alone and in combination with CPI therapy. Methods: This phase 1/2, open-label, multicenter, dose-escalation/expansion study is assessing the safety, tolerability and preliminary activity of OR2805 alone and in combination with anti-PD-1 or chemotherapy in up to 325 adults (≥18 years) with histologically or cytologically confirmed metastatic or locally advanced solid tumors. The study is divided into 3 parts. Part A will enroll subjects with advanced solid tumors of any histology to describe the preliminary safety profile of OR2805 and determine the recommended phase 2 dose (RP2D) of OR2805 alone and in combination with an anti-PD-1 monoclonal antibody. Part B will further characterize the safety and preliminary antitumor activity of OR2805 either alone or in combination with an anti-PD-1 or chemotherapy in previously treated non-small cell lung cancer (NSCLC), melanoma and liposarcoma, as well as in previously untreated NSCLC in combination with an anti-PD-1 antibody. Part C will evaluate OR2805 monotherapy in relapsed squamous cell carcinoma of the head and neck and other tumor types with an emphasis on correlative biomarker analysis. OR2805 will be infused on Day 1 of 21-day cycles. Primary endpoints are adverse events, laboratory abnormalities, dose-limiting toxicities, and dose-level safety and activity. Secondary endpoints are objective response rates, duration of response, complete response, progression-free survival, overall survival, PK, and antidrug antibodies. Exploratory biomarkers of OR2805-mediated pharmacodynamic effects and immune stimulation will be explored. The study was opened September 2021 and is enrolling at sites in the United States with planned expansion within the US and to Europe. Clinical trial information: Clinical trial information: NCT05094804.

A phase 1/2 study of DCC-3116 as a single agent and in combination with trametinib in patients with advanced or metastatic solid tumors with RAS or RAF mutations

TPS3178

Background: Autophagy, a catabolic process to resupply nutrients and recycle damaged organelles, is activated by cancer cells to survive hypoxia, limited nutrients, or chemotherapy. The RAS family of oncoproteins are the most commonly mutated oncoproteins in human cancer and require autophagy for tumor growth and survival. RAS activates signaling through the mitogen-activated protein kinase (MAPK) pathway that is responsible for regulating cell survival. ULK1/2 are kinases that receive and process input from nutrient and stress sensors to initiate autophagy. Inhibition of the MAPK pathway releases tonic inhibition of ULK1/2 and triggers autophagy as a survival mechanism, suggesting that ULK1/2 may provide a promising therapeutic target. DCC-3116 is a potent and selective ULK inhibitor that showed preclinical antitumor activity in combination with the MAPK kinase inhibitor trametinib (Smith et al. 2019 AACR-NCI-EORTC Poster). Here, we describe the Phase 1 study of DCC-3116 monotherapy and combination therapy with trametinib in patients with RAS or RAF mutant advanced or metastatic solid tumors. Methods: This is a Phase 1/2, multicenter, open-label, first-in-human study evaluating safety, tolerability, clinical activity, pharmacokinetics, and pharmacodynamics of DCC-3116 as a single agent and in combination with trametinib (NCT04892017). The study consists of single agent and combination dose escalation cohorts and expansion of combinations with demonstrated safety. Single-agent oral DCC-3116 will be administered twice daily (BID) in escalating cohorts in 28-day cycles until the recommended Phase 2 dose (RP2D) is determined. Subsequently, the single-agent RP2D or one level below the maximum tolerated dose (MTD) will be administered in combination with trametinib. Participants in the dose escalation phase must be ≥18 years with a histologically confirmed diagnosis of advanced or metastatic solid tumor with a documented RAS or RAF mutation, have progressed despite standard therapies, and have received ≥1 prior anticancer therapy. In the dose expansion phase, DCC-3116 will be given BID with trametinib in 28-day cycles to participants with pancreatic ductal adenocarcinoma, non-small cell lung cancer, colorectal cancer, or melanoma (Cohorts 1–4, respectively). Primary outcomes are incidence of adverse events, identification of MTD, and objective response rate per RECIST v1.1. Secondary outcomes include duration of response, clinical benefit rate, time to response, progression-free survival, and pharmacokinetic/pharmacodynamic attributes. Participants in dose expansion cohorts must be ≥18 years and meet cohort-specific criteria including histologically confirmed diagnoses, documented mutation status, and number of prior lines of systemic therapy. This study is recruiting and plans to enroll up to 130 participants. Clinical trial information: NCT04892017.

A phase 1, first-in-human study of IK-930, an oral TEAD inhibitor targeting the Hippo pathway in subjects with advanced solid tumors

TPS3168

Background: The transcriptional enhanced associate domain (TEAD) family of proteins are key transcription factors in the Hippo signaling pathway and play a critical role in cell proliferation, migration, angiogenesis, and apoptosis. Published literature demonstrates that approximately 10% of all solid tumors present with a dysregulated Hippo pathway and subsequent constitutive activation of TEAD, which drives gene expression involved in cell growth and pro-survival signaling. Deficiencies in neurofibromin 2 (NF2), a key regulator of the Hippo pathway, can be found in over 40% of cases of malignant pleural mesothelioma (MPM). NF2 deficiency also occurs at high incidence in meningiomas, cholangiocarcinomas, thymoma, and schwannoma. Gene fusions in in Yes1 associated transcriptional regulator (YAP1) or WW domain containing transcription regulator 1 (TAZ/WWTR1) are also indicative of high TEAD activation and can be seen in solid tumors including epithelioid hemangioendothelioma (EHE) where >90% of cases are associated with TAZ-CAMTA1 gene fusion and the other 10% of cases have YAP1/TFE3 gene fusion. IK-930 is a novel, selective, small molecule inhibitor of TEAD that prevents palmitate binding and thereby disrupts aberrant TEAD-dependent transcription. In preclinical models, IK-930 demonstrates antitumor activity in mouse xenograft models with Hippo pathway genetic alterations. IK-930 is under clinical investigation as an oral agent in patients with advanced solid tumors. Methods: This is a phase 1, first-in-human, open-label, multicenter dose escalation and dose expansion study to evaluate the safety and tolerability of IK-930 as monotherapy, and to determine the recommended phase 2 dose (RP2D) and/or maximum tolerated dose (MTD) using the Bayesian Optimal Interval Design (BOIN). Eligible participants in dose escalation include adult patients with advanced or metastatic solid tumors for whom there is no available therapy known to confer clinical benefit. Patients will receive escalating doses of IK-930 starting at 25mg daily. IK-930 will be administered initially in a 28-day cycle and will progress to a 21-day cycle when evaluated as safe and well-tolerated. A dose expansion phase will follow with four genetically defined cohorts of solid tumors, including: NF2-deficient MPM (Cohort 1), other NF2-deficient solid tumors agnostic to tumor type (Cohort 2), EHE with TAZ-CAMTA1 or YAP1-TFE3 gene fusions (Cohort3), and solid tumors with YAP1/TAZ gene fusions agnostic to tumor type (Cohort 4). Primary endpoints include evaluation of dose-limiting toxicities and treatment-emergent adverse events and determination of RP2D and/or MTD. Secondary objectives include evaluation of preliminary antitumor activity by RECIST 1.1 and pharmacokinetic (PK) parameters. The study began in January 2022 and is currently enrolling. Clinical trial information: NCT05228015.

Phase 1b study of GS-3583, a novel FLT3 agonist Fc fusion protein, in patients with advanced solid tumors

2566

Background: We have previously shown that systemic administration of GS-3583, a Fms-like tyrosine kinase 3 (FLT3) agonist Fc fusion protein leads to expansion of conventional dendritic cells (cDC), both subtype 1 (cDC1) and subtype 2 (cDC2), in the periphery of healthy volunteers (Rajakumaraswamy N, et al. J Clin Oncol. 2021;39[suppl_15]:2559.). This mechanism may increase cDC in the tumor microenvironment and promote T cell mediated antitumor activity in patients with solid tumors. Methods: This ongoing, Phase 1b, open label study is investigating the safety, tolerability, immunogenicity, pharmacokinetics, and pharmacodynamics of escalating multiple doses of GS-3583 monotherapy in adult patients with advanced solid tumors using a standard 3 + 3 design. GS-3583 was administered intravenously on Days 1 and 15 of Cycle 1 and on Day 1 of each subsequent 28-day cycle for up to 52 weeks or until progressive disease or unacceptable toxicity. Dose-limiting toxicity (DLT) was evaluated during the first 28 days of GS-3583 therapy at each dose level. Results: At the time of the Dec 3, 2021 data cut-off, 9 patients have enrolled in 3 dose escalation cohorts. Median (range) age was 71 (44-79); 4 (44%) patients were male. Tumor types were pancreatic (n=3), ovarian (n=4), and rectal (n=2). To date, no DLTs or discontinuation due to adverse events (AE) have been observed. Three patients had Grade ≥3 AEs which were also recorded as serious AEs, none of which were considered related to GS-3583. Dose dependent increase in GS-3583 exposure was observed in the evaluated dose range 2 to 12 mg with target-mediated drug disposition appearing to be saturated at doses above Dose Level 2. GS-3583 accumulation was observed at higher dose levels. GS-3583 treatment resulted in expansions of cDC1 and cDC2 at all 3 doses (Table); a dose-dependent trend in the magnitude and the durability of cDC expansion was observed. At the highest dose evaluated, GS-3583 produced ≥100-fold expansion of both cDC1 and cDC2 at multiple time points. Dose escalation on the study is still ongoing. Conclusions: GS-3583 was safe and well tolerated and induced dose-dependent expansion of cDCs in the periphery in patients with advanced solid tumors up to doses of 12 mg. These findings support further dose escalation and clinical development of GS-3583 in combination with agents that would stimulate the expanded cDCs to produce anti-tumor responses. Clinical trial information: NCT04747470. [Table: see text]

Newly updated activity results of alrizomadlin (APG-115), a novel MDM2/p53 inhibitor, plus pembrolizumab: Phase 2 study in adults and children with various solid tumors

9517

Background: Alrizomadlin restores TP53 function, activating p53-mediated apoptosis in tumor cells with wild-type TP53 and/or MDM2 amplification. Alrizomadlin also functions as a host immunomodulator and may restore antitumor activity in pts with cancers that progressed on PD-1/PD-L1 inhibitors. Methods: This US/Australian multicenter trial evaluated alrizomadlin, an investigational MDM2-selective, small-molecule inhibitor, combined with pembrolizumab, in pts with unresectable/metastatic melanoma that progressed on I-O drugs; pts with malignant peripheral nerve sheath tumor (MPNST), well-differentiated/dedifferentiated liposarcoma, non-small cell lung cancer (NSCLC), or solid tumors with ATM mutations that progressed on available standard therapy; or pts for whom therapy was unavailable. Eligible pts had ECOG performance status of 0-2 and, if present, stable brain metastases. Alrizomadlin 150 mg PO was administered QOD for 2 consecutive weeks, with 1 week off, and pembrolizumab 200 mg IV over 30 minutes on Day 1 of a 21-day cycle. Results: As of November 3, 2021, preliminary and interim results are reported for 130 pts in 6 cohorts: melanoma (n = 44), NSCLC (n = 26), ATM mutation (n = 18), liposarcoma (n = 17), urothelial (n = 13), and MPNST (n = 12). In the melanoma cohort, confirmed ORR by RECIST, (PR + CR) was 13% (2 CRs + 3 PRs/38 efficacy evaluable [EE] pts). In cutaneous and uveal melanoma subcohorts, confirmed ORR was 24% (2 CRs + 2 PRs/17 EE pts) and 9% (1 PR/11 EE pts), respectively. In the MPNST cohort, the clinical benefit rate, defined by confirmed ORR + SD of > 4 cycles, was 40% (4 SDs/10 EE pts). Additional confirmed PRs were reported in NSCLC, urothelial, and liposarcoma cohorts (1 each). Common treatment (alrizomadlin or pembrolizumab)-related adverse events (TRAEs; ≥ 10%) were nausea (62%), thrombocytopenia (39%), vomiting (38%), fatigue (38%), decreased appetite (29%), diarrhea (25%), neutropenia (15%), and anemia (12%). Grade 3+ TRAEs (≥ 5%) included thrombocytopenia (23%), neutropenia (10%), and anemia (7%). A total of 16 pts discontinued treatment due to AEs; 6 were treatment related, including grade 4 thrombocytopenia (n = 3), grade 2 vomiting (n = 1), grade 2 fatigue (n = 1), and grade 2 posterior reversible encephalopathy syndrome (PRES; n = 1). A total of 10 pts reported treatment-related SAEs: 1 each of abdominal pain, asthenia, colitis, febrile neutropenia, hypophysitis, peripheral edema, overdose, PRES, pulmonary embolism, pyrexia, and thrombocytopenia. Conclusions: Alrizomadlin, combined with pembrolizumab, is well tolerated and demonstrates preliminary antitumor activity in multiple tumor types and may restore antitumor effects in pts with cancer resistant or intolerant to I-O drugs. Internal study identifiers: APG-115-US-002; Keynote MK-3475-B66. Clinical trial information: NCT03611868.

Phase 1 first-in-human study of anti–ILT3 mAb MK-0482 as monotherapy and in combination with pembrolizumab in advanced solid tumors: Dose escalation results

2505

Background: Immunoglobulin-like transcript 3 (ILT3) is an inhibitory receptor associated with immune tolerance and T-cell suppression within the tumor microenvironment. MK-0482, a novel humanized IgG4 mAb targeting ILT3, is undergoing phase 1 evaluation ± pembrolizumab (pembro) in advanced solid tumors (NCT03918278; MK-0482-001). Dose escalation data are presented. Methods: Eligible patients with advanced solid tumors were enrolled into sequentially escalating dose cohorts of MK-0482 monotherapy (0.2-2250 mg) or MK-0482 (7.5-2250 mg) + pembro 200 mg; both were administered IV Q3W for up to 35 cycles or until progressive disease (PD), unacceptable toxicity, death, or withdrawal. Patients receiving MK-0482 monotherapy could cross over to MK-0482 + pembro after PD. Primary objectives were safety, tolerability, and determination of the recommended phase 2 dose (RP2D). Secondary and exploratory objectives included assessing pharmacokinetics (PK), blood receptor occupancy (RO), anti–drug antibodies (ADA), and objective response rate (ORR) per RECIST v1.1 by investigator assessment. Results: Seventy-five patients were enrolled (n = 29, MK-0482 monotherapy; n = 46, MK-0482 + pembro); 8 patients crossed over to receive the combination. Median age was 63 years (range, 34-86); 73% had ECOG PS 1, 72% received ≥2 lines of prior anticancer therapy, and 32% received prior PD-1/PD-L1 inhibitors. Treatment-related AEs (TRAEs; any-grade/grade 3 or 4) were reported in 34%/7% of patients with MK-0482 monotherapy, 67%/4% with MK-0482 + pembro, and 50%/13% in those who crossed over. The most common TRAEs (≥10% of all patients) were pyrexia (10%) with MK-0482 monotherapy; fatigue (24%) and arthralgia, diarrhea, hyperthyroidism, hypothyroidism, and pruritus (11% each) with MK-0482 + pembro; and arthralgia (25%), hyperthyroidism and hypothyroidism (13% each) for patients who crossed over. Dose-limiting toxicities occurred in 2 patients who received MK-0482 + pembro: 1 grade 5 myositis (MK-0482 750 mg; the only TRAE leading to death) and 1 grade 2 myositis (MK-0482 2250 mg). Preliminary PK and blood RO data suggested that target-mediated drug disposition of MK-0482 was likely saturated in blood mononuclear cells at doses ≥75 mg. ADA to MK-0482 was observed in ̃20% of patients, but no clear impact on MK-0482 PK was observed. A confirmed ORR of 15% (8 PR) was observed in patients who received MK-0482 + pembro, including patients who crossed over; no confirmed responses were observed in patients who received MK-0482 monotherapy. MK-0482 750 mg + pembro was selected as the RP2D based on the totality of data. Conclusions: MK-0482 ± pembro was generally well tolerated, and combination therapy provided modest antitumor activity in patients with heavily pretreated advanced solid tumors. The RP2D of MK-0482 + pembro is under further evaluation in tumor-specific cohorts. Clinical trial information: NCT03918278.

A phase Ia/Ib, dose-escalation/expansion study of BI 907828 in combination with BI 754091 (ezabenlimab) and BI 754111 in patients (pts) with advanced solid tumors

3095

Background: Preclinical data show that combining a murine double minute 2–tumor protein 53 (MDM2–p53) antagonist with immune checkpoint inhibitors produces anti-tumor effects in multiple tumor types. This Phase Ia/Ib study (NCT03964233) is assessing BI 907828, a MDM2–p53 antagonist, combined with immune checkpoint inhibitors in TP53 wild-type cancers. Methods: In Phase Ia (dose escalation), pts with advanced/metastatic solid tumors received escalating doses of BI 907828 guided by a Bayesian Logistic Regression Model (starting dose 10 mg orally) plus ezabenlimab 240 mg (anti-PD-1 antibody) and BI 754111 600 mg (anti-LAG-3 antibody) every 21 days (q3w). Primary endpoint was the maximum tolerated dose (MTD) of BI 907828 based on the number of pts with dose-limiting toxicities (DLTs) during cycle one. During Phase Ia, other studies indicated a lack of added efficacy when BI 754111 was combined with ezabenlimab; therefore, the study design was updated to switch the dose escalation to the doublet combination of BI 907828 plus ezabenlimab. Results: A total of 11 pts received the triplet combination at 10/20/30/45 mg dose levels (DL; n = 3/3/3/2 respectively); all have discontinued treatment. No DLTs were reported in cycle one; MTD was not reached. As of 20th January 2022, 15 pts have received the doublet combination at 30/45 mg DLs (n = 10/5 respectively). One pt (45 mg) had a DLT during cycle one: G2 neutropenia. Four DLTs were reported after cycle one: G3 anemia (30 mg); G2 thrombocytopenia (45 mg); and G3 neutropenia and G4 thrombocytopenia (45 mg). G≥3 adverse events occurred in eight pts; most commonly anemia (n = 6), thrombocytopenia (n = 4) and lymphopenia (n = 3). There were no notable safety findings with BI 907828 45 mg q3w, the recommended dose for expansion (RDE) for BI 907828 monotherapy. Nine of the 15 pts who received doublet therapy were evaluable for response; four had a confirmed partial response (PR; 30 mg, n = 1; 45 mg, n = 3), two biliary tract carcinoma, one urothelial carcinoma, and one myxoid liposarcoma; one had an unconfirmed PR (30 mg) with adenocarcinoma (primary site intrahepatic cholangiocarcinoma). Four pts with liposarcoma and gastric cancer had stable disease. MTD will be reported. In Phase Ib, pts will receive the RDE of BI 907828 plus 240 mg ezabenlimab (q3w). Pts will be recruited to two cohorts: soft tissue sarcomas (liposarcoma, undifferentiated pleomorphic sarcoma, myxofibrosarcoma, synovial sarcoma and leiomyosarcoma) and selected MDM2-amplified tumors (NSCLC, gastric adenocarcinoma, urothelial carcinoma, and biliary tract carcinoma). Primary endpoints are progression-free survival and objective response (RECIST 1.1). Conclusions: The doublet combination of BI 907828 plus ezabenlimab showed a manageable safety profile and early signs of anti-tumor activity. Eleven pts remain on treatment; recruitment is ongoing. Clinical trial information: NCT03964233.

Phase 1 study of ADG126, a novel masked anti-CTLA-4 SAFEbody, that combines tumor-localized activation with strong Treg depletion and soft ligand blocking in patients with advanced solid tumors

e17601

Background: SAFEbody ADG126, a masked version of NEObody ADG116 (ESMO IO Conference Abstract #394, NCT04501276), targets a unique species-conserved CTLA-4 epitope with preclinical safety and efficacy profiles superior to ipilimumab, an approved anti-CTLA-4 immune checkpoint inhibitor known to cause treatment-related irAEs in ̃70% of patients. ADG126 is designed to unlock the great potential of anti-CTLA-4 immunotherapy in 4 key ways: 1) improving safety through masking to limit on-target off-tumor irAEs in normal tissues, 2) widening the therapeutic window through selective activation in tumor microenvironment (TME), 3) maximizing anti-tumorigenic effects through prolonged exposure and steady accumulation of activated ADG126 in TME, 4) enhancing antitumor potency relative to ipilimumab via a higher Teff/Treg ratio achieved by combining T cell activation and strong ADCC-mediated Treg depletion in TME. We present interim results from our ongoing Phase 1 study of ADG126 (NCT04645069). Methods: ADG126 monotherapy [0.1, 0.3, 1, 3, 10 mg/kg (mpk)] was given to patients with advanced solid tumors Q3W IV. Primary endpoints are safety and tolerability. Secondary endpoints are PK, ORR per RECIST v1.1, and PFS. Results: For 16 patients treated in dose escalation cohorts (≤10 mpk), the median age was 65 years with 31% receiving >3 prior lines of therapies, and 31% progressed from immuno-oncology (IO) therapy. ADG126 was well-tolerated with no DLTs observed, nor was the MTD reached. Only Grade 1 TRAEs were reported, with fatigue (19%) and pruritis (13%) being most common. Plasma PK was approximately linear with a 1.7-fold increase in the mean t1/2z for the total drug over the intact ADG126, suggesting the activated ADG126 accumulated steadily with > 2 fold accumulation at Ctrough during repeat dosing, resulting in saturating target engagement at 10 mpk. Stable disease was seen in 5/16 patients with 1/5 surpassing > 24 weeks. One ovarian cancer, and 1 uveal melanoma patient who progressed on nivolumab/ipilimumab, showed > 20% durable reductions in target lesions by CT, and increased CD8+ T cells post-dosing. In the same ovarian cancer patient, a 77% reduction in CA-125 occurred after 7 treatment cycles at 1 mpk. Conclusions: ADG126 demonstrated excellent tolerability and safety for continuous dosing beyond 4 cycles at 10 mpk and for more than 8 cycles at 1 mpk. Compared to ADG116, its non-masked parental Ab, ADG126 exhibited superior PK and early efficacy signals correlated with increased peripheral CD8+ T cells, in general. ADG126 may offer better safety and efficacy profile than ipilimumab, which could help realize the full potential of blocking the CTLA-4 pathway. Combination studies of ADG126 with anti-PD-1Ab(s) have been initiated to determine their safety and efficacy in IO-sensitive and resistant cancer types. Clinical trial information: NCT04645069.

First-in-human study of PC14586, a small molecule structural corrector of Y220C mutant p53, in patients with advanced solid tumors harboring a TP53 Y220C mutation

3003

Background: The p53 tumor suppressor protein is a transcription factor that acts to maintain genome stability in response to cellular stress. Spontaneous mutation of the TP53 gene leading to inactivation of the p53 protein is the most common mutational event across all human cancers. PC14586 is a novel, small molecule structural corrector that binds selectively to p53 Y220C mutant protein and restores the p53 wildtype conformation and transcriptional activity, resulting in potent preclinical antitumor activity. This Phase 1 multicenter dose escalation study assesses PC14586 safety, pharmacokinetics (PK), pharmacodynamics (PD) and preliminary efficacy in patients (pts) with advanced solid tumors that harbor the TP53 Y220C mutation. Methods: Eligible adult pts with locally advanced or metastastic TP53 Y220C mutant solid tumors received increasing doses of oral PC14586 using the modified Toxicity Probability Interval design to estimate toxicity and to determine maximum tolerated dose and recommended phase 2 dose. Plasma PK was characterized using standard methods. Preliminary efficacy was assessed by RECIST v1.1. Reporting of interim results was approved by the study’s Safety Review Committee. Results: As of 08 Feb 2022, 29 pts (62% female, median age 62 years) with a variety of TP53 Y220C mutant solid tumor types (median number of prior lines of therapy 3; range 1 to 8) were treated in 7 dose cohorts of PC14586: 150 mg QD (3 pts), 300 mg QD (3 pts), 600 mg QD (4 pts), 1150 mg QD (5 pts), 2000 mg QD (7 pts), 2500 mg QD (4 pts) and 1500 mg BID (3 pts). PC14586 was generally well-tolerated; treatment-related AEs were observed in 79% of pts that were all Grade 1/2 in severity except 2 Grade 3 AEs (alanine aminotransferase increased and neutrophil count decreased). The most common AEs (≥15% of pts) were nausea (34%), vomiting (24%), fatigue (21%), and aspartate aminotransferase increased (17%). There were no dose limiting toxicities and enrollment continues. PK analysis showed dose proportional increases in Cmax and AUC. Amongst 21 efficacy evaluable pts, PRs were observed in 5 pts: 1 small cell lung and 1 breast with confirmed PR (cPR), both ongoing; 1 colorectal with unconfirmed PR (uPR), and 2 prostate with uPR and ongoing. In the 3 highest dose cohorts (total daily dose 2000 to 3000 mg), there were 3 PRs (2 uPR, 1cPR) and 7 SD out of 10 efficacy evaluable pts (all ongoing). Observations of decreasing p53 Y220C circulating tumor DNA and decreasing numbers of circulating tumor cells in pts further support on-target anti-tumor activity of PC14586. Conclusions: Enrollment to a Phase 1 study is feasible in a TP53 mutation selective population. PC14586 is safe and tolerated up to 3000 mg daily. Preliminary efficacy was achieved in heavily pretreated pts. Additional safety, PK, PD and efficacy data will be reported at the annual meeting. Clinical trial information: NCT04585750.

ELU-FRα-1: A study to evaluate ELU001 in patients with solid tumors that overexpress folate receptor alpha (FRα)

TPS3158

Background: ELU001 is a novel, first-in-class, new molecular entity described as a C’Dot Drug Conjugate (CDC). ELU001 consists of ̃12 folic acid targeting moieties and ̃22 exatecan topoisomerase-1 inhibitor payloads on Cathepsin-B cleavable linkers covalently bound to the surface of each silicon core/polyethylene glycol C’Dot nanoparticle. CDCs are small in size (̃6 nm), have a greater ability to penetrate into and through tumors as compared to ADCs, and are rapidly eliminated by the kidneys. The rapid systemic elimination is expected to lead to less toxicity than is observed with targeting platforms like ADCs that have a longer half-life in circulation. ELU001’s high avidity is believed to promote internalization into FRα overexpressing cancer cells, selectively delivering it’s ̃22 molecules of payload. The first-in-human clinical trial, ELU-FRα-1, is currently recruiting patients that have advanced, recurrent or refractory FRα overexpressing tumors considered to be topoisomerase 1 inhibitor-sensitive based on the literature, and, in the opinion of the Investigator, have no satisfactory therapeutic options available. Methods: This is a Phase 1 / 2 multicenter, open label clinical trial with two parts: Part 1 Dose Escalation and Part 2 Tumor Group Expansion Cohort(s). In Part 1, patients with cancer types with a high likelihood of having FRα overexpressing tumors based on historical data, (specifically, ovarian, endometrial, colorectal, gastric, gastroesophageal junction, triple negative breast, or non-small cell lung cancers, or cholangiocarcinoma), will be enrolled to the study. Patients will receive ELU001 on a weekly dose regimen (QW) (once a week for 3 weeks, 1 week rest) or every other week dose regimen (Q2W, with no rest between cycles). Retrospective analysis of FRα expression will be determined. Part 2 uses a Simon’s Two-Stage design to evaluate 4-6 tumor group expansion cohorts, each consisting of patients with specific tumor types (to be identified based on emerging data) that overexpress FRα (prospectively determined prior to enrollment). The primary objective for Part 1 is to identify the MTD/RP2D and for Part 2 is ORR. Dose Escalation will recruit about 25 patients per dose regimen (QW or Q2W). Dose Expansion will recruit about 15 patients per tumor group expansion cohort. Secondary objectives are anti-tumor activity (DOR, PFS, TFST, PFS2, OS), frequency, severity and tolerability of adverse events, PK, ADA, and FRα expression assessments. The study is actively enrolling in the US – Cohorts 1-2 have been completed without DLT. Enrollment to Cohort 3 began in December 2021. Clinical trial information: NCT05001282 .

Phase Ib/II study of BCL-2 inhibitor lisaftoclax (APG-2575) safety and tolerability when administered alone or combined with a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in patients with estrogen receptor-positive (ER+) breast cancer or advanced solid tumors

TPS1122

Background: Various cancers evade apoptosis by overexpressing BCL-2 proteins. Investigational agent lisaftoclax (APG-2575) is a novel, potent, selective BCL-2 inhibitor, while palbociclib inhibits cyclin-dependent kinases (CDK) 4 and 6. In preclinical studies, palbociclib decreased proliferation of ER+ breast cancer cell lines by arresting them in the G1 cycle phase. Preclinical data demonstrate favorable, complementary effects of palbociclib when combined with a BCL-2 inhibitor and support this combination in patients with ER+/ human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer. Methods: This global multicenter open-label dose escalation and dose expansion study is assessing the safety of lisaftoclax monotherapy in patients with histologically or cytologically confirmed advanced solid tumors that have progressed on standard therapy or when combined with CDK4/6 inhibitor palbociclib in physiologically postmenopausal women with ER+/ HER2- metastatic breast cancer that has progressed or relapsed after treatment with a CDK4/6 inhibitor. This trial consists of 2 parts: a phase Ib dose escalation phase using a standard 3+3 design to determine the maximum tolerated dose (MTD) of lisaftoclax as a single agent in patients with solid tumors, as well as both the MTD and recommended phase 2 (RP2D) dose of lisaftoclax when combined with palbociclib in women with ER+/ HER2- metastatic breast cancer. Phase II of this study is a signal-seeking expansion of lisaftoclax at RP2D when combined with palbociclib in women with ER+/HER2- metastatic breast cancer. This phase is being conducted using Simon’s Minimax two-stage design. The primary objective for phase II is to determine clinical benefit response, and secondary efficacy endpoints include overall response rate, duration of response, time to response, and progression-free survival. Lisaftoclax is being administered orally once daily in a 28-day cycle at the assigned dose. Clinical trial information: NCT04946864.

First-in-human trial exploring safety, antitumor activity, and pharmacokinetics of Sym013, a recombinant pan-HER antibody mixture, in advanced epithelial malignancies

PURPOSE

 Sym013 contains six humanized monoclonal antibodies that bind to non-overlapping epitopes on three human epidermal growth factor receptors (HER1-3). Preclinical studies suggested Sym013 strongly suppresses growth of multiple epithelial tumors. This is a first-in-human study exploring safety and efficacy of Sym013 in patients with advanced epithelial malignancies.

METHODS

 Dose escalation used single-patient cohorts until the stopping rule was met, followed by 3 + 3 design. Dose levels planned were: 1, 2, 4, 6, 9, 12, 15, and 18 mg/kg. Treatment cycles were 28 days with imaging every eight weeks. Serum samples were collected at multiple time points for assessment of pharmacokinetics and development of anti-drug antibodies.

RESULTS

 Thirty-two patients were enrolled with multiple solid tumors, most common being colorectal cancer (CRC; 10/32, 31%). Due to mucositis, rash, and diarrhea at 4 mg/kg once-weekly, dosing was changed to biweekly (Q2W). Mandatory prophylaxis was added due to Grade 3 infusion-related reaction and oral mucositis at 9 mg/kg Q2W. The 15 mg/kg Q2W cohort was enrolling when the study was terminated for business reasons. Most common adverse events were skin (81%) and gastrointestinal (75%) disorders, including dermatitis/rash, stomatitis, and diarrhea. One patient with CRC achieved a partial response; 12 patients with varied malignancies had stable disease.

CONCLUSION

 During the conduct of the study, management of frequent infusion-related reactions, skin toxicities, and mucosal disorders, which are indicative of HER inhibition, necessitated multiple protocol amendments. The investigators, in concert with the Sponsor, agreed that achieving a tolerated regimen with acceptable target saturation was unlikely.

TRIAL REGISTRY

www.clinicaltrials.gov ; NCT02906670 (September 20, 2016).

A Phase I Study of an MPS1 Inhibitor (BAY 1217389) in Combination with Paclitaxel Using a Novel Randomized Continual Reassessment Method for Dose Escalation

PURPOSE

Monopolar spindle 1 (MPS1) kinase inhibitor, BAY 1217389 (BAY) synergizes with paclitaxel. This phase I study assessed the combination of BAY with paclitaxel using a novel randomized continuous reassessment method (rCRM) to improve dose determination.

PATIENTS AND METHODS

Patients with solid tumors were randomized to receive oral BAY (twice daily 2-days-on/5-days-off) with weekly paclitaxel (90 mg/m²) or paclitaxel monotherapy in cycle 1. Dose escalation was guided by CRM modeling. Primary objectives were to assess safety, establish the MTD of BAY, and to evaluate the pharmacokinetic profiles for both compounds. Simulations were performed to determine the contribution of the rCRM for dose determination.

RESULTS

In total, 75 patients were enrolled. The main dose-limiting toxicities were hematologic toxicities (55.6%). The MTD of BAY was established at 64 mg twice daily with paclitaxel. Inclusion of a control arm enabled the definitive attribution of grade ≥3 neutropenia to higher BAY exposure [AUC_0-12 (P< 0.001)]. After determining the MTD, we included 19 patients with breast cancer at this dose for dose expansion. Other common toxicities were nausea (45.3%), fatigue (41.3%), and diarrhea (40.0%). Overall confirmed responses were seen in 31.6% of evaluable patients. Simulations showed that rCRM outperforms traditional designs in determining the true MTD.

CONCLUSIONS

The combination of BAY with paclitaxel was associated with considerable toxicity without a therapeutic window. However, the use of the rCRM design enabled us to determine the exposure-toxicity relation for BAY. Therefore, we propose that the rCRM could improve dose determination in phase I trials that combine agents with overlapping toxicities.

First-in-Human Study of PF-06647020 (Cofetuzumab Pelidotin), an Antibody-Drug Conjugate Targeting Protein Tyrosine Kinase 7, in Advanced Solid Tumors

PURPOSE

We investigated safety, tolerability, pharmacokinetics, and antitumor activity of the protein tyrosine kinase 7 (PTK7)-targeted, auristatin-based antibody-drug conjugate (ADC) PF-06647020/cofetuzumab pelidotin (NCT02222922).

PATIENTS AND METHODS

Patients received PF-06647020 intravenously every 3 weeks at 0.2-3.7 mg/kg or every 2 weeks at 2.1-3.2 mg/kg, in sequential dose escalation, following a modified toxicity probability interval method. In dose expansion, pretreated patients with advanced, platinum-resistant ovarian cancer, non-small cell lung cancer (NSCLC), or triple-negative breast cancer (TNBC) received PF-06647020 2.8 mg/kg every 3 weeks.

RESULTS

The most common, treatment-related adverse events for PF-06647020 administered every 3 weeks were nausea, alopecia, fatigue, headache, neutropenia, and vomiting (45%-25%); 25% of patients had grade ≥ 3 neutropenia. Two patients experienced dose-limiting toxicities (grade 3 headache and fatigue) at the highest every 3 weeks dose evaluated. The recommended phase II dose was 2.8 mg/kg every 3 weeks. The overall safety profile observed with PF-06647020 administered every 2 weeks was similar to that of the every 3 weeks regimen. Systemic exposure for the ADC and total antibody generally increased in a dose-proportional manner. Antitumor activity was observed in treated patients with overall objective response rates of 27% in ovarian cancer (n = 63), 19% in NSCLC (n = 31), and 21% in TNBC (n = 29). Responders tended to have moderate or high PTK7 tumor expression by IHC.

CONCLUSIONS

This PTK7-targeted ADC demonstrated therapeutic activity in previously treated patients with ovarian cancer, NSCLC, and TNBC at a dose range of 2.1-3.2 mg/kg, supporting further clinical evaluation to refine dose, schedule, and predictive tissue biomarker testing in patients with advanced malignancies.

BDB001, an intravenously administered toll-like receptor 7 and 8 (TLR7/8) agonist, in combination with pembrolizumab in advanced solid tumors: Phase 1 safety and efficacy results

2512

Background: BDB001 is an intravenously administered TLR 7/8 dual agonist immune modulator capable of reprogramming dendritic cells to produce antitumor activities. BDB001 monotherapy has demonstrated favorable tolerability and robust systemic immune activation leading to durable clinical responses in a phase I dose escalation trial. Here, we report on the safety and efficacy of BDB001 in combination with pembrolizumab in a phase I dose escalation trial in advanced solid tumors (NCT03486301). Methods: BDB001-101 is a phase 1, open label, dose escalation/expansion trial of BDB001 (IV, Q1W) in combination with pembrolizumab (IV, Q3W) in patients with advanced solid tumors. The primary endpoint was safety and tolerability. Secondary endpoints included efficacy, pharmacokinetics and pharmacodynamic profiling of immune activation. Results: Twenty-three subjects with 13 different tumor types were enrolled across 4 dose levels. Sixty one percent were female, median age was 63 years (range, 33-86), median number of prior therapies was 3 (range, 1-8), and 48% of tumors had progressed on prior anti-PD-(L)1 therapy. Overall, BDB001 in combination with pembrolizumab was well tolerated and dose-limiting toxicities were not observed. The most common treatment related adverse events (TRAEs) were fever (39.1%), fatigue (39.1%), chills/rigor (34.8%), pruritus/rash (21.7%), and nausea (13.0%). Most of these TRAEs were grade 1 or 2 and transient. Only 3 (13.0%) subjects experienced grade 3 TRAEs of fatigue, rash, stomatitis, and alkaline phosphatase elevation. There were no grade 4 or 5 TRAEs. Pharmacodynamic evaluation of plasma cytokine levels showed robust increases in interferon gamma and interferon inducible protein-10 (IP-10) at BDB001 Dose Level 3 and 4. Preliminary efficacy evaluation of the 14 subjects treated at Dose Level 3 and 4 showed durable and deep clinical responses in 4 (29%) subjects with anti-PD-(L)1 mAb refractory melanoma, hepatocellular carcinoma, cholangiocarcinoma, and platinum-resistant ovarian carcinoma. The responses were observed by the initial efficacy assessment at 9-weeks, with some seen as early as 4-weeks. In addition, 4 (29%) subjects had stable disease for a disease control rate of 57%. To date, median time on treatment is 14.4 weeks (range, 6.0 – 42.1+) with 3 subjects still active on treatment. Conclusions: Intravenously administered BDB001 in combination with pembrolizumab is well tolerated. Rapid and deep clinical responses were observed, supported by robust systemic immune activation. BDB001 in combination with pembrolizumab is a promising novel therapeutic option for patients with advanced solid tumors and is being evaluated in an ongoing dose expansion trial. Clinical trial information: NCT03486301.

A first-in-human phase I study of ATR inhibitor M1774 in patients with solid tumors

TPS3153

Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response by sensing and responding to DNA replication stress, and by inducing cell cycle arrest to prevent aberrant replication and mitotic catastrophe. Based on extensive preclinical and limited clinical evidence, ATR inhibition is a promising treatment strategy as monotherapy for patients with advanced tumors harboring synthetically lethal conditions, such as alternative lengthening of telomeres (ALT) and inactivating mutations in ARID1A and ATM. M1774 is a potent, selective, orally administered ATR inhibitor that has been shown to exert antitumor activity in patient-derived xenograft tumors and acute myeloid leukemia xenograft tumors that express the ATR inhibition sensitizing mixed lineage leukemia fusion protein. This study (NCT04170153) aims to evaluate the safety and tolerability, maximum tolerated dose, recommended dose for expansion (RDE) and pharmacokinetics (PK) of M1774 (part A1), the effect of food on M1774 PK (part A2), and the efficacy of M1774 in patients with tumors harboring selected mutations (part A3). An additional objective is to assess the pharmacodynamics of M1774 by measuring relative changes in baseline p-CHK1 and γ-H2AX expression in paired tumor biopsies and serial blood samples. Methods: Patients aged ≥18 years, with an Eastern Cooperative Oncology Group performance status ≤1, adequate baseline hematological, renal and hepatic function, and with locally advanced or metastatic disease refractory to standard therapy are eligible. Patients with tumors bearing loss-of-function (LoF) mutations (determined by site testing or a central trial assay) in ARID1A, ATM, or ATRX and/or DAXX as ALT status surrogate markers; and measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, will be enrolled in part A3. In the dose escalation phase (part A1 [open]), 18–24 patients are due to receive M1774 at a starting dose of 5 mg once daily. Dose escalation is determined by the safety monitoring committee and guided by a Bayesian 2-parameter logistic regression model. The preliminary food assessment (part A2) will follow a randomized two-sequence two-period crossover design in which ≤12 patients will be randomized (1:1) to receive a single dose of M1774 on Day –7 at the RDE (determined in part A1) in either a fed or fasted condition. After the food assessment, patients will subsequently receive M1774 according to the part A1 dosing schedule. In the preliminary efficacy study (part A3), patients (n = 20–24 for each of the three planned cohorts) with tumors harboring LoF mutations in the genes for ARID1A, ATM, ATRX and/or DAXX, will receive M1774 at the RDE. The primary efficacy endpoint is overall response (RECIST). The study is open and currently recruiting. Patients have been enrolled to seven cohorts in part A1 with no DLTs observed; dose escalation is ongoing. Clinical trial information: NCT04170153.

NBE-002: A novel anthracycline-based antibody-drug conjugate (ADC) targeting ROR1 for the treatment of advanced solid tumors—A phase 1/2 clinical trial

TPS1108

Background: The receptor tyrosine kinase-like orphan receptor 1 (ROR1) is highly expressed during embryonic development, but is minimally present or absent on post-partum healthy tissues. ROR1 is expressed in a variety of hematological and solid tumors and is associated with aggressive cancer phenotype and poor clinical outcomes. NBE-002 is an ADC targeting ROR1, obtained by site-specific, enzymatic conjugation of the anthracycline-derivative PNU-159682, modified with a non-cleavable linker to a humanized recombinant IgG1 monoclonal antibody, based on a novel anti-human ROR1 monoclonal antibody XBR1-402 (Peng et al. (2017) J. Mol. Biol. 429: 2954-73). Direct anti-tumor activity of NBE-002 was evaluated in immunodeficient, ROR1 expression-low/-intermediate/-high PDX models of several carcinoma and sarcoma subtypes. The most pronounced anti-tumor effect was achieved in triple-negative breast cancer (TNBC), at doses as low as 0.033 mg/kg, suggesting a best-in-class therapeutic index in light of the high tolerability in preclinical toxicology models. Administration in a fully immune competent setting (EMT6/ROR1 orthotopic breast cancer model) led to a strong anti-tumor response and a long-lasting anti-tumor immune protection dependent on CD8 T cells. Methods: NBE-002-01 (NCT04441099) is a first-in-human, open-label, multi-center, phase (Ph) 1/2 study of NBE-002 in adult patients with advanced solid tumors. Ph 1 of the study consists of a Dose Escalation Cohort (DEC), utilizing an accelerated titration design, followed by a traditional 3+3 design, and an optional Safety Expansion Cohort (SEC). Ph 2 will include two parallel Expansion Cohorts (EC), enrolling patients with advanced TNBC (EC1) or other solid tumors (EC2), with Simon’s two-stage design. Key eligibility criteria include Eastern Cooperative Oncology Group performance status of 0-2 (Ph 1) or 0-1 (Ph 2), adequate organ function defined as: hemoglobin ≥9.0 g/dL, neutrophils ≥1500 /µL, platelets ≥100000/µL, aspartate and alanine aminotransferases ≤2.5x the upper limit of normal (ULN), total bilirubin ≤1.5x ULN, creatinine ≤1.5x ULN, left ventricular ejection fraction ≥50%. The primary objectives are to assess safety and tolerability and to establish the recommended dose for further development (Ph 1), and to evaluate anti-tumor activity of (Ph 2). Secondary and exploratory objectives include characterization of immunogenicity as well as pharmacokinetic and pharmacodynamic profiles. NBE-002 is given intravenously once every three weeks until disease progression, unacceptable toxicity, withdrawal of consent, or other protocol-specific criteria are met. Ph 1 dose escalation was initiated on 17 JULY 2020 and is still recruiting in the US. Ph 2 is planned to be initiated in 2022. Clinical trial information: NCT04441099 .

A first-in-human study of mirzotamab clezutoclax as monotherapy and in combination with taxane therapy in relapsed/refractory solid tumors: Dose escalation results

3015

Background: Mirzotamab clezutoclax (ABBV-155) is a first-in-class antibody drug conjugate comprised of a BCL-XL (B-cell lymphoma - extra long) inhibitor, solubilizing linker, and a monoclonal anti-B7H3 antibody. Methods: Patients (pts) with relapsed and/or refractory (R/R) solid tumors were administered mirzotamab clezutoclax with or without paclitaxel. Dose escalation of mirzotamab clezutoclax was guided by Bayesian continual reassessment. Primary outcomes were to determine the maximum tolerated dose (MTD) and the recommended phase 2 dose (RP2D). Secondary outcomes: safety, pharmacokinetics, and overall response rate per RECIST v1.1. Results: As of November 6, 2020, 31 pts received mirzotamab clezutoclax monotherapy (monoTx) and 28 pts received combination therapy with paclitaxel (comboTx). Overall demographics: median age 62 years (range 25–79); 61% female; 86% white; 24% ECOG 0, 76% ECOG 1; 51% had > 3 prior systemic therapies. The median duration of mirzotamab clezutoclax exposure was 3 cycles (range 1–14) for monoTx and 5 cycles (range 1–14) for comboTx. There were no dose limiting toxicities (DLT) reported with monoTx. In comboTx, 2 pts experienced a DLT: Grade 4 neutrophil count decreased and Grade 3 lymphocyte count decreased considered related to paclitaxel. 97% of all pts had adverse events (AEs). The most common AEs (in ≥20% of pts) overall were fatigue (39%), nausea (25%), diarrhea and arthralgia (22% each), vomiting and hypokalemia (20% each). AEs in ≥5 pts related to mirzotamab cleuzutoclax were fatigue (27%), diarrhea (12%), and nausea (9%). Related Grade 3/4 AEs overall (in > 1 patient) included anemia, lymphocyte count decreased, fatigue, and diarrhea (3% each). One patient on monoTx experienced a fatal cardiac arrest. No fatal AEs occurred on comboTx. Responses were observed with comboTx as shown in the Table. Conclusions: Mirzotamab clezutoclax as monotherapy and with paclitaxel demonstrates a tolerable safety profile (MTD not reached) with anti-tumor activity in R/R solid tumors. Further investigation in prospectively-selected B7H3 positive tumors as monoTx in pts with R/R small cell lung cancer and with paclitaxel in pts with R/R breast cancer and docetaxel in pts with R/R non-small cell lung cancer in the dose expansion phase is ongoing. Clinical trial information: NCT03595059. [Table: see text]

Preliminary results of a phase II study of alrizomadlin (APG-115), a novel, small-molecule MDM2 inhibitor, in combination with pembrolizumab in patients (pts) with unresectable or metastatic melanoma or advanced solid tumors that have failed immuno-oncologic (I-O) drugs

2506

Background: Alrizomadlin (APG-115) restores TP53 function, activating p53-mediated apoptosis in tumor cells with wild-type TP53 and/or MDM2 amplification. Alrizomadlin also functions as a host immunomodulator and hence may restore antitumor activity in pts with cancers failing PD-1/PD-L1 blockade. Methods: This US multicenter trial assessed alrizomadlin combined with pembrolizumab in pts with unresectable/metastatic melanoma or advanced solid tumors that had failed I-O drugs; or pts with malignant peripheral nerve sheath tumor (MPNST), liposarcoma, or ATM mutant solid tumors that had failed any standard therapy. Eligible pts had ECOG performance status of 0-2 and no CNS metastases. The phase II study cohorts included pts with melanoma, NSCLC, solid tumor with ATM mutation, well-differentiated/dedifferentiated liposarcoma, urothelial carcinoma, and MPNST. Alrizomadlin was administered orally at 150 mg once every other day for 2 consecutive weeks with 1 week off and pembrolizumab at 200 mg via IV infusion for 30 minutes on Day 1 of a 21-day cycle. Results: As of December 25, 2020, 84 pts had been treated in 6 cohorts: melanoma (n = 26), NSCLC (n = 23), ATM mutation (n = 9), liposarcoma (n = 14), urothelial (n = 9), and MPNST (n = 3). In the PD-1/PD-L1 inhibitor-failed melanoma cohort, there was 1 confirmed partial response (PR) out of 5 pts with uveal melanoma, 2 PR (1 confirmed and 1 unconfirmed) of 5 pts with mucosal melanoma, and 1 confirmed PR of 11 pts with cutaneous melanoma. ORR in the melanoma cohort was 17.4% (4/23 evaluable pts), and the disease control rate was 60.9% (14/23). In the MPNST cohort, 1 of 3 pts had an unconfirmed ongoing PR. In I-O drug-failed NSCLC (n = 14 evaluable) and urothelial (n = 5 evaluable) cohorts, each reported 1 confirmed PR. Common treatment (alrizomadlin or pembrolizumab)-related adverse events (TRAEs) (≥ 10%) were nausea (63.1%), thrombocytopenia (36.9%), vomiting (33.3%), fatigue (31.0%), decreased appetite (27.4%), diarrhea (21.4%), neutropenia (15.4%), and anemia (11.9%). Grade ≥ 3 TRAEs (≥ 5%) included thrombocytopenia (20.2%), neutropenia (14.2%), and anemia (8.3%). Eleven pts discontinued treatment due to AEs: 5 were treatment related, including 2 grade 4 thrombocytopenia, and 1 each of grade 2 vomiting, grade 2 fatigue, and grade 2 posterior reversible encephalopathy syndrome (PRES). Three treatment-related SAEs were PRES, pyrexia, and asthenia. Conclusions: Alrizomadlin combined with pembrolizumab is well tolerated and may restore antitumor effects in pts with cancer resistant to or intolerant of I-O drugs, as suggested by preliminary antitumor activities in multiple tumor types. Internal study identifiers: APG-115-US-002; Keynote MK-3475-B66. Clinical trial information: NCT03611868.

PF-06939999, a potent and selective PRMT5 inhibitor, in patients with advanced or metastatic solid tumors: A phase 1 dose escalation study

3019

Background: Protein arginine methyltransferase 5 (PRMT5) methylates multiple substrates known to be dysregulated in cancer, including components of the spliceosome machinery. PF-06939999 is a selective small-molecule inhibitor of PRMT5. Here we report the safety, PK, PD, and preliminary activity of PF-06939999 in patients (pts) with selected advanced/metastatic solid tumors. Methods: This phase 1 dose escalation trial (NCT03854227) enrolled pts with solid tumor types marked by potential frequent splicing factor mutations, including advanced/metastatic endometrial cancer, head and neck squamous cell carcinoma (HNSCC), non-small cell lung cancer (NSCLC), urothelial cancer, cervical cancer, or esophageal cancer. PF-06939999 monotherapy was continuously administered orally QD or BID in 28-day cycles. A Bayesian Logistic Regression Model was used to inform dose level decisions. Primary objectives were to assess dose limiting toxicities (DLTs), AEs and laboratory abnormalities. Tumor response was assessed using RECIST v1.1. PK and PD were assessed by determining PF-06939999 plasma concentration after dosing and changes in plasma levels of symmetric di-methyl arginine (SDMA), the product of PRMT5 enzymatic activity. Results: 28 pts received PF-06939999 at doses from 0.5-12 mg daily (QD or BID) during dose escalation. Median number of cycles was 2 (range, 1-13). Most were female (54%) with a median age of 61.5 (range, 32-84) y. Median number of prior therapies was 4. Overall, 4/24 (17%) pts reported DLTs: thrombocytopenia (n=2, 6 mg BID); anemia (n=1, 8 mg QD); and neutropenia (n=1, 6 mg QD). Treatment-related AEs occurred in 24 (86%) pts. Most common (≥20%) treatment-related AEs across all cycles were anemia (43%), thrombocytopenia (32%), dysgeusia, fatigue and nausea (29% each). Grade ≥3 treatment-related AEs included anemia (25%), thrombocytopenia (21%), fatigue, neutropenia and lymphocyte count decreased (4% each). One pt (6mg BID) had Grade 4 treatment-related thrombocytopenia. All cytopenias were dose-dependent and reversible with dose modification. No pts discontinued treatment for treatment-related toxicity. There were no treatment-related deaths. Exposure to PF-06939999 increased with doses in the dose range tested. Plasma SDMA was reduced at steady state (58.4-87.5%), indicating robust PD target inhibition. Two pts had confirmed partial response (HNSCC and NSCLC). 6 mg QD was identified as the recommended monotherapy dose for expansion. Conclusions: PF-06939999 showed dose-dependent and manageable toxicities in this phase 1 dose escalation study. Objective tumor responses were observed in pts with HNSCC and NSCLC. Analysis of archival tissue for the presence of splicing factor mutations and other potential predictive biomarkers is ongoing. Enrollment to part 2 dose expansion is ongoing in pts with NSCLC, HNSCC and urothelial cancer. Clinical trial information: NCT03854227.

Phase 1b dose escalation study to evaluate the safety, tolerability, pharmacokinetics, and preliminary efficacy of GS-3583, a FLT3 agonist Fc fusion protein, in patients with advanced solid tumors

TPS3147

Background: Productive antitumor immune responses in nonclinical models depend on a type of dendritic cell (DC), conventional DC subtype 1 (cDC1), which in the context of cancer, primes tumor-reactive T cells through presentation of tumor-derived antigens. FMS-related tyrosine kinase 3 ligand (FLT3L) is a hematopoietic growth factor that binds to and activates FLT3 on terminally differentiated DCs. Activated FLT3 promotes proliferation, inhibits cell death, and is required for the differentiation, expansion, and maintenance of DCs in peripheral and lymphoid organs. GS-3583 is a fusion protein composed of the extracellular domain of recombinant human FLT3L fused to an engineered fragment crystallizable (Fc) region of human immunoglobulin G4. GS-3583 has PK properties that support sustained cDC in patients and potential combination with established immunotherapies. This phase 1b, open-label, multicenter, dose-finding study will evaluate safety, tolerability, PK, and preliminary efficacy of GS-3583 monotherapy in patients with advanced solid tumors (NCT04747470). Methods: Approximately 33 adults aged ≥18 years with a histologically or cytologically confirmed locally advanced or metastatic malignant solid tumor that is refractory to or intolerant of standard therapy or for which no standard therapy is available will be enrolled. The study employs a 3+3 dose escalation design in which GS-3583 is administered intravenously for up to 52 weeks or until progressive disease or unacceptable toxicity. Up to five dose escalation cohorts have been planned. The maximum tolerated dose is the highest dose with incidence of DLT in < 33% of 6 or more patients in the first 28 days of GS-3583 dosing; recommended phase 2 dose will be determined. Assessments include safety, PK, pharmacodynamics including cDCs, immunogenicity, and efficacy by RECIST 1.1 in CT/MRI imaging conducted every 8 weeks. Accrual at approximately 3-4 centers in the US is ongoing. Clinical trial information: NCT04747470.

Initial results from a phase 1b study of ORIC-101, a glucocorticoid receptor antagonist, in combination with nab-paclitaxel in patients with advanced solid tumors

2553

Background: ORIC-101 is a potent and selective, orally bioavailable, small molecule antagonist of the glucocorticoid receptor (GR). Preclinical studies have demonstrated that activation of GR signaling leads to decreased responsiveness to chemotherapeutics (eg, taxanes) and antiandrogens across multiple tumor types. Mechanistically, ORIC-101 inhibits GR transcriptional activity and blocks the prosurvival signals mediated by the activated nuclear hormone receptor. Methods: A 3+3 dose escalation design was used to assess safety, pharmacokinetics (PK), pharmacodynamics (PD), and select the Recommended Phase 2 Dose (RP2D) of ORIC-101 in combination with nab-paclitaxel (nab-pac; NCT03928314). ORIC-101 doses ranging from 80 to 240 mg once daily, given either intermittently or in a continuous dosing regimen, were evaluated in combination with weekly nab-pac at 75 or 100 mg/m2. Plasma PK and PD biomarkers were assessed on day 1 and after repeat dosing. PD modulation in blood-derived peripheral blood mononuclear cells (PBMCs) was assessed by RT-qPCR for GR target genes. Antitumor activity was assessed by RECIST v1.1. Results: 21 patients with 10 different solid tumors, with and without a prior taxane, were treated in 5 cohorts. ORIC-101 exposure increased with dose, with no evidence for drug-drug interaction with nab-pac. In the initial cohort at 240 mg ORIC-101 and 100 mg/m2 nab-pac, 2 patients experienced dose limiting toxicities (DLTs) of Grade 3 fatigue and Grade 4 neutropenia/thrombocytopenia, respectively. No further DLTs were observed in subsequent cohorts and the RP2D was established as 160 mg ORIC-101 dosed once daily continuously for 21 days with nab-pac 75 mg/m2 given on days 1, 8, and 15 of each 28-day cycle, without requirement for prophylactic granulocyte colony-stimulating factor (G-CSF). The most common (> 15%), all grade treatment-related adverse events (AEs) were nausea (38%), diarrhea (33%), fatigue (29%), leukopenia (29%), neutropenia (29%), anemia (24%), and 19% of patients had increased liver function tests and alopecia. Biomarker data demonstrated ORIC-101-induced reduction in GR target gene expression in PBMCs, indicating PD modulation at all dose levels of ORIC-101. Preliminary antitumor activity was observed in 3 taxane-refractory patients with breast, endometrial, and pancreatic cancers. Conclusions: The combination of ORIC-101 and nab-paclitaxel demonstrated an acceptable tolerability profile and does not require prophylactic G-CSF. PK and PD showed no evidence of drug-drug-interaction and demonstrated GR target inhibition. Preliminary antitumor activity was observed in patients with solid tumors that previously progressed on a taxane-containing regimen. Dose expansion is ongoing at the RP2D in dedicated pancreatic, ovarian, triple negative breast cancers, and tissue-agnostic cohorts. Clinical trial information: NCT03928314.

Initial findings of the first-in-human phase I study of AGEN2373, a conditionally active CD137 agonist antibody, in patients (pts) with advanced solid tumors

2634

Background: CD137 is a member of the tumor necrosis factor receptor superfamily that functions as a potent co-stimulator of both adaptive and innate immune cells, thus making it an attractive target for cancer immunotherapy. The development of first-generation anti-CD137 antibodies has been hampered by limited clinical activity or dose-limiting hepatotoxicity. AGEN2373 is a novel, conditionally active CD137 agonist antibody designed to selectively enhance tumor immunity while mitigating side effects associated with systemic activation of CD137. Here we report the initial findings from the first-in-human evaluation of AGEN2373 in pts with advanced solid cancers. Methods: Pts received AGEN2373 on day 1 of a 28-day cycle (Q4W dosing), with cycles repeated until progression, intolerable toxicity or investigator/patient decision. Dose-escalation followed a standard 3+3 scheme, with planned dosing of 0.03, 0.06, 0.3, 1.0, 2.0, and 3.0 mg/kg. The primary objective was to determine the safety, tolerability, and dose-limiting toxicity (DLT) of AGEN2373 as monotherapy. Secondary objectives included pharmacokinetics (PK) and preliminary clinical activity. Adverse events (AEs) were reported per CTCAE v5.0 and DLTs evaluated within a 28-day window. For PK analyses, serum AGEN2373 concentrations determined using a validated bioanalytical assay and simultaneously analyzed by an NLME model. Antitumor activity was assessed using RECIST v1.1. Results: As of January 21 2021, 19 pts (median age 54.4 years, range 33-74; 11 men, 8 women; 7 with prior immunotherapy) have been treated with AGEN2373 Q4W at escalating doses from 0.03 – 2.0 mg/kg across 5 cohorts. Eleven pts (57.9%) experienced treatment-related AEs; none were grade 3 or higher. The most common events were fatigue (4 pts, 21.1%) and nausea (2 pts, 10.6%). No DLTs have been observed. Importantly, no drug-related elevations in liver transaminases (ALT, AST) or bilirubin beyond 1 grade have been seen. AGEN2373 PK were consistent with linear elimination. Prolonged disease stabilization as best response occurred in 5 pts (26.3%; range, 6-41 weeks); three of which were seen in heavily pretreated pts with metastatic leiomyosarcoma, including one who had progressed on prior combination checkpoint immunotherapy. Enrollment into the 3.0 mg/kg cohort is continuing. Conclusions: AGEN2373 demonstrates good tolerability in pts with advanced solid tumors, with a safety profile characterized by a lack of hepatotoxicity frequently observed with CD137-targeting antibodies. These findings underscore the suitability of AGEN2373 as a potential partnering agent for other immunomodulatory agents, including planned expansion as combination therapy with balstilimab (anti-PD-1). Clinical trial information: NCT04121676.

Phase I study of ABBV-428, a mesothelin-CD40 bispecific, in patients with advanced solid tumors

BACKGROUND

CD40 agonist immunotherapy can potentially license antigen-presenting cells to promote antitumor T-cell activation and re-educate macrophages to destroy tumor stroma. Systemic administration of CD40 agonists has historically been associated with considerable toxicity, providing the rationale for development of tumor-targeted immunomodulators to improve clinical safety and efficacy. This phase I study assessed the safety, tolerability, preliminary antitumor activity, and preliminary biomarkers of ABBV-428, a first-in-class, mesothelin-targeted, bispecific antibody designed for tumor microenvironment-dependent CD40 activation with limited systemic toxicity.

METHODS

ABBV-428 was administered intravenously every 2 weeks to patients with advanced solid tumors. An accelerated titration (starting at a 0.01 mg/kg dose) and a 3+3 dose escalation scheme were used, followed by recommended phase II dose cohort expansions in ovarian cancer and mesothelioma, tumor types associated with high mesothelin expression.

RESULTS

Fifty-nine patients were treated at doses between 0.01 and 3.6 mg/kg. The maximum tolerated dose was not reached, and 3.6 mg/kg was selected as the recommended phase II dose. Seven patients (12%) reported infusion-related reactions. Treatment-related grade ≥3 treatment-emergent adverse events were pericardial effusion, colitis, infusion-related reaction, and pleural effusion (n=1 each, 2%), with no cytokine release syndrome reported. The pharmacokinetic profile demonstrated roughly dose-proportional increases in exposure from 0.4 to 3.6 mg/kg. Best response was stable disease in 9/25 patients (36%) treated at the recommended phase II dose. CD40 receptor occupancy >90% was observed on peripheral B-cells starting from 0.8 mg/kg; however, no consistent changes from baseline in intratumoral CD8+ T-cells, programmed death ligand-1 (PD-L1+) cells, or immune-related gene expression were detected post-ABBV-428 treatment (cycle 2, day 1). Mesothelin membrane staining showed greater correlation with progression-free survival in ovarian cancer and mesothelioma than in the broader dose escalation population.

CONCLUSIONS

ABBV-428 monotherapy exhibited dose-proportional pharmacokinetics and an acceptable safety profile, particularly for toxicities characteristic of CD40 agonism, illustrating that utilization of a tumor-targeted, bispecific antibody can improve the safety of CD40 agonism as a therapeutic approach. ABBV-428 monotherapy had minimal clinical activity in dose escalation and in a small expansion cohort of patients with advanced mesothelioma or ovarian cancer.

TRIAL REGISTRATION NUMBER

NCT02955251.

KRYSTAL-2: A phase I/II trial of adagrasib (MRTX849) in combination with TNO155 in patients with advanced solid tumors with KRAS G12C mutation

TPS146

Background: KRAS is the most frequently mutated oncogene in cancer and a key mediator of the RAS/MAPK signaling cascade that promotes cellular growth and proliferation. KRAS G12C tumor mutations occur in approximately 14% of patients with lung adenocarcinoma and 3-4% of colorectal adenocarinoma. SHP2 is a phosphatase that acts as a key mediator of signaling from receptor tyrosine kinases (RTKs) to downstream RAS/MAPK pathways. Adagrasib (MRTX849) is a specific small-molecule investigational inhibitor of KRAS G12C that covalently binds to and locks mutant KRAS in its GDP-bound inactive form. Adagrasib has been optimized for a long half-life and extensive tissue distribution to enable inhibition throughout the entire dosing interval. Preliminary results from a Phase 1/2 study of adagrasib demonstrated promising antitumor activity and tolerability across multiple KRAS G12C tumor types. TNO155 is a selective inhibitor of SHP2 with demonstrated inhibition of RTK signaling and significant antitumor activity in preclinical models. Preclinical studies have shown that resistance to KRAS G12C inhibition may be mediated by SHP2-dependent feedback loops. Because KRAS G12C retains some level of cycling between GTP- and GDP-bound states, KRAS G12C that is not bound by inhibitor can activate downstream signaling. Active SHP2 functions to increase the active state of RAS proteins (including mutant KRAS) and also increases ERK pathway activation. Therefore, the addition of TNO155 to adagrasib may augment antitumor activity and overcome resistance by inhibiting cycling to GTP-bound KRAS and/or through inhibition of feedback activation and more comprehensively inhibiting downstream ERK signaling. In KRAS G12C human tumor models, adagrasib combined with a SHP2 inhibitor demonstrated greater activity compared to each agent alone. These data provide support for clinical evaluation of this combination in KRAS G12C tumors. Methods: KRYSTAL-2 is a multicenter Phase 1/2 study evaluating adagrasib and TNO155 in patients with advanced solid tumors harboring a KRAS G12C mutation. Overall objectives of the trial include evaluating safety, tolerability, and PK. The Phase 1 portion will evaluate adagrasib and TNO155 utilizing a modified Toxicity Probability Interval dose escalation design to identify maximum tolerated dose and recommended Phase 2 dose. The Phase 2 portion utilizes a Simon's optimal two-stage design to evaluate the clinical activity of adagrasib with TNO155 in 2 cohorts of up to 108 patients—CRC (54 patients) and NSCLC (54 patients). Efficacy endpoints include Objective Response Rate (RECIST 1.1), Duration of Response (DOR), Progression-free Survival (PFS), and Overall Survival (OS). The study is currently enrolling and patients will receive study treatment until disease progression, unacceptable adverse events, patient withdrawal, or death. Clinical trial information: NCT04330664.

The Evolution of Antibody-Drug Conjugates: A Positive Inflexion Point

In 2019, an important inflection point occurred when the U.S. Food and Drug Administration approved three new antibody-drug conjugates (ADCs) for the treatment of malignancies, including urothelial cancer (enfortumab vedotin-ejfv), diffuse large B-cell lymphoma (polatuzumab vedotin-piiq), and HER2 breast cancer (fam-trastuzumab deruxtecan-nxki), and expanded the indication for ado-trastuzumab emtansine to early breast cancer. This near doubling in the number of approved ADCs within 1 year validates the ADC platform and represents a successful evolution over the past 30 years. ADCs were born in an era when systemic therapy for cancer was largely cytotoxic chemotherapy. Many of the investigational cytotoxic agents were determined to be too toxic for oral and intravenous use. The agents were especially potent, with inhibitory concentrations that inhibited 50% of cells in the nanomolar and picomolar range but had poor therapeutic indexes when administered systemically. Now, over the last 30 years, we have seen an evolution of the many aspects of this complex platform with better antigen target selection, more sophisticated chemistry for the linkers, a growing diversity of payloads from cytotoxic chemotherapy to targeted therapies and immunostimulants, and, with the recent series of regulatory approvals, a buoyed sense of optimism for the technology. Nonetheless, we have not fully realized the full potential of this platform. In this review, the many components of ADCs will be discussed, the difficulties encountered will be highlighted, the innovative strategies that are being used to improve them will be assessed, and the direction that the field is going will be considered.

Abstract CT149: SNDX-6352-0502 - A phase 1, open-label, dose escalation trial to investigate the safety, tolerability, pharmacokinetics and pharmacodynamic activity of SNDX-6352 monotherapy in patients with unresectable, recurrent, locally-advanced, or metastatic solid tumors

Background: Immunosuppressive tumor associated macrophages (TAMs) have been shown to correlate with poor prognosis. SNDX-6352 is a humanized, high-affinity monoclonal IgG4 antibody that blocks dual ligand activation of colony stimulating factor- 1 receptor (CSF-1R), which regulates monocyte migration, proliferation and differentiation into TAMs. By inhibiting and reducing TAM numbers, SNDX-6352 may slow tumor growth and enhance anti-tumor immunotherapeutic approaches.

Methods: SNDX-6352-0502 was a multi-center Phase 1 study consisting of Phase 1a (monotherapy) and Phase 1b (combination with durvalumab) in patients with pretreated, advanced solid tumors. The primary objective was determining the MTD and RP2D of SNDX-6352 alone and in combination with durvalumab. Dose regimens of 1, 2, 3 and 6 mg/kg bi-weekly (q2wks) and 6 mg/kg once monthly (q4wks) were administered in 1a, and 1, 2, and 3 mg/kg bi-weekly in 1b. Drug pharmacokinetics (PK) and pharmacodynamic (PD) biomarkers were measured.

Results: Thirty-two patients with advanced solid tumors were enrolled with a median age of 61. The median number of prior therapies was 5 (range 2-12) and 72% of patients had ECOG performance status of 1. Median exposure in terms of cycles was 2, maximum was 10. Three patients had SD greater than 4 months. Most common (&gt; 10%) treatment-related AEs were fatigue (31%), periorbital edema (31%) aspartate aminotransferase increased (22%), blood creatinine phosphokinase increased (22%) nausea (13%) and decreased appetite (13%). Grade 3/4 related AEs were observed in 12 patients (38%) with ≥ 2 events in CPK (5), amylase (3), AST (3) and lipase (2). One possibly related SAE of pneumonitis at 6 mg/kg q2wks was reported. DLTs reported in two subjects were G3 fatigue at 2 mg/kg and G3 pneumonitis at 6 mg/kg q2wks. Laboratory abnormalities included increases in blood creatinine phosphokinase, ALT, AST, amylase, and lipase. These abnormalities were all asymptomatic and are consistent with the known class effect of CSF-1Ri. There was no evidence of hepatocellular toxicity. Plasma concentrations of SNDX-6352 increased in a dose-proportional manner with drug accumulation observed at &gt; 1 mg/kg. Plasma CSF1 and IL-34 concentrations increased with treatment and remained elevated at all doses &gt; 1 mg/kg. CSF1 receptor occupancy was saturated at 4 hours post-dose in all treatment cohorts. Circulating non-classical monocytes (CD14+CD16hi) were ablated at all dose levels within 24 hrs and remained suppressed at all doses &gt;1 mg/kg.

Conclusion: SNDX-6352 demonstrates tolerability at the highest dose level evaluated (6 mg/kg) with robust PD biomarker modulation at doses as low as 1 mg/kg. A RP2D of 6mg/kg q4wks will be explored in future solid tumor studies.

Citation Format: Nilo Azad, Drew Rasco, Sunil Sharma, Matthew Taylor, Christine Quaranto, David L. Tamang, Robert Nordness, Michael L. Meyers, Serap Sankoh, Peter Ordentlich, Anthony W. Tolcher. SNDX-6352-0502 - A phase 1, open-label, dose escalation trial to investigate the safety, tolerability, pharmacokinetics and pharmacodynamic activity of SNDX-6352 monotherapy in patients with unresectable, recurrent, locally-advanced, or metastatic solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT149.

Abstract 4538: A safe and potent agonist ADG106 targeting a unique epitope of CD137 with novel mechanism of actions

Antagonist antibodies targeting immune checkpoint co-inhibitory receptor such as PD-1/PD-L1 have achieved great clinical success in cancer immunotherapy. However, agonistic antibodies targeting the co-stimulatory T cell receptors in the TNFR superfamily, and CD137 in particular, has suffered significant setback due to either dose-dependent severe liver toxicity by Urelumab, or modest clinical anti-tumor activity by Utomilumab. ADG106, a safe and potent antibody targeting a unique epitope of CD137, is shown to hold the great promise to achieve much better efficacy and safety profile for immunotherapy in preclinical and phase 1 studies. ADG106, a fully human agonistic anti-CD137 IgG4 mAb, binds to a unique and conserved epitope with multiple cross-species reactivity, and overlaps with CD137 ligand binding site. This unique antibody acts in a novel mechanism with the following attributes: 1) it agonizes CD137 in a natural ligand-like fashion; 2) it blocks ligand to disable its reverse signaling; 3) it exhibits strong but specific Fc receptor mediated crosslinking in comparison with Utomilumab. ADG106 shows robust dose-dependent single agent anti-tumor activity in multiple syngeneic mouse tumor models and induces durable antigen-specific memory immunity that protects animals from the same re-challenged tumor cells. Consistent with the preclinical observations, ongoing phase I trial shows that the same antibody, ADG106, is well-tolerated in cancer patients in dose escalation from 0.03 to 3 mg/kg; and it also shows single agent activity on circulating T cell activation and clonal expansion in anti-tumor activity. Furthermore, ADG106 has also induced complete remission of the liver metastatic lesion in a lymphoma patient at 1mg/kg dose. Preclinical studies demonstrate that ADG106 enhances activation and inflammatory cytokine release of primed T cells alone or together with other immunomodulatory agents in vitro, as well as exhibits synergistic in vivo anti-tumor activity in combination with variety of other cancer therapies, including checkpoint inhibitors, chemotherapies and targeted agents. Mechanistic analyses suggest that ADG106 stimulates tumor infiltration and expansion of CD4+ and CD8+ T cells, thereby promoting the antitumor responses. These findings support that ADG106-boosted immune response could offer an effective but alternative solution for cancer immunotherapy in single and combination therapies, especially for non-responders to current PD-1/PD-L1 based immunotherapies.

Citation Format: Guizhong Liu, Felix Du, Xiaohong She, Yi Zhu, Anthony W. Tolcher, Peter Luo. A safe and potent agonist ADG106 targeting a unique epitope of CD137 with novel mechanism of actions [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4538.

Abstract CT242: SNDX-6352-0502: A phase 1, open-label, dose escalation trial to investigate the safety, tolerability, pharmacokinetics and pharmacodynamic activity of SNDX-6352 in combination with durvalumab in patients with unresectable, recurrent, locally-advanced, or metastatic solid tumors

Background: Tumor associated macrophages have been proposed to suppress the anti-tumor immune responses potentiated by immune checkpoint blockade. CSF1 receptor (CSF-1R) blockade enhances anti-PD1 or PD-L1 anti-tumor efficacy in various tumor models. SNDX-6352 is a high affinity, humanized monoclonal antibody against CSF1R. This Phase 1 study was designed to identify a recommended phase 2 dose for the combination of SNDX-6352 and the anti-PD-L1 antibody, durvalumab.

Methods: Study SNDX-6352-0502 was a multi-center Phase 1 study consisting of Phase 1a (monotherapy) and Phase 1b (combination with durvalumab). The primary objective of 1b was to define MTD or RP2D of the combination as evaluated by the incidence of DLTs. The 1b cohorts included 1, 2, and 3 mg/kg administered q2wk in combination with a fixed dose of 1500 mg durvalumab q4wk. The RP2D was determined based on safety, drug exposure, and PD biomarker changes.

Results: 12 patients with advanced solid tumors were treated with durvalumab and SNDX-6352 (3 at 1 mg/kg, 3 at 2 mg/kg, and 6 at 3 mg/kg). Median number of prior therapies was 6.5 (range 2-13). Median age at enrollment was 67 years (range 34-74), and 75% of patients had ECOG performance status of 1. Median exposure in terms of cycles was 2 (range 2-4). Nine SAEs occurred in 5/12 (42%) patients. All SAEs were assessed as unrelated to study drug and generally reflected co-morbidity in this population of patients with advanced cancer.

Most common treatment-related AEs were edema peripheral (33%), fatigue (25%), periorbital edema (25%), and hypothyroidism (25%). Grade 3 or higher treatment-related AEs were reported in 4 patients (33%). One patient had two events (anemia and pericardial effusion); amylase increased, diarrhea, and rash occurred in 1 patient each. Elevations in circulating enzymes were consistent with the known effect of the class on Kupffer-cell mediated clearance of circulating enzymes. No objective responses have been reported to date.

Plasma concentrations of SNDX-6352 increased in a dose-proportional manner with drug accumulation observed at &gt; 1mg/kg. Treatment led to elevations of plasma concentrations of CSF1R ligands, CSF1 and IL-34, which remained above pre-dose levels at doses &gt; 1 mg/kg. CSF1 receptor occupancy was saturated at 4 hours post-dose in all treatment cohorts. Circulating non-classical monocytes (CD14+CD16hi) were depleted at all dose levels after one day.

Conclusion: SNDX-6352 is a potent CSF1R antagonist that demonstrates tolerability and robust PD biomarker modulation in combination with durvalumab. The recommended phase 2 dose of 3 mg/kg administered q2wk in combination therapy will be explored in future studies.

Citation Format: Anthony W. Tolcher, Drew Rasco, Sunil Sharma, Matthew Taylor, Christine Quaranto, David L. Tamang, Robert Nordness, Michael L. Meyers, Serap Sankoh, Peter Ordentlich, Nilo Azad. SNDX-6352-0502: A phase 1, open-label, dose escalation trial to investigate the safety, tolerability, pharmacokinetics and pharmacodynamic activity of SNDX-6352 in combination with durvalumab in patients with unresectable, recurrent, locally-advanced, or metastatic solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT242.

A phase Ia/Ib, dose-escalation/expansion study of BI 907828 in combination with BI 754091 and BI 754111 in patients (pts) with advanced solid tumors

TPS3660

Background: Preclinical data show that the combination of a murine double minute 2–tumor protein 53 (MDM2–TP53) antagonist with anti-PD-1 and anti-LAG3 antibodies produces an anti-tumor effect in multiple tumor types. This Phase Ia/Ib study aims to determine the safety, recommended dose for expansion (RDE), and preliminary efficacy of BI 907828, a MDM2–TP53 antagonist, with BI 754091, an anti-PD-1 antibody, and BI 754111, an anti-LAG-3 antibody, in a variety of TP53 wild-type cancers. Methods: In Phase Ia (dose escalation), ~30 pts with a confirmed diagnosis of any unresectable, advanced/metastatic solid tumor, irrespective of TP53 mutation status, will be enrolled. Pts will receive one dose of BI 907828 every 21 days (Q3W), at a starting dose of 10 mg orally, plus BI 754091 and BI 754111 (240 mg and 600 mg, respectively, Q3W, intravenously). Dose escalation will be guided by a Bayesian Logistic Regression Model with overdose control. The primary endpoint is the maximum-tolerated dose of BI 907828 based on dose-limiting toxicities (DLTs) during the first treatment cycle. Secondary endpoints include pharmacokinetics and DLTs in the treatment period (to determine the RDE). In Phase Ib (dose expansion), pts with previously treated, unresectable, advanced/metastatic TP53 wild-type tumors with ≥1 measurable target lesion will be enrolled into four expansion cohorts (1: NSCLC; 2: melanoma; 3: well-differentiated/dedifferentiated liposarcoma or undifferentiated pleomorphic sarcoma; 4: hepatocellular carcinoma). The RDE of BI 907828 will be administered with fixed doses of BI754091 and BI 754111 (Q3W). In the NSCLC cohort only, pts will be randomized to one of three arms: RDE of BI 907828 + 240 mg BI 754091 + 600 mg BI 754111 (arm A, 32 pts); 240 mg BI 754091 + 600 mg BI 754111 (arm B, 32 pts); RDE of BI 907828 + 240 mg BI 754091 (arm C, 16 pts). The primary endpoint is objective response (OR, per RECIST 1.1). Secondary endpoints include OR (per iRECIST), disease control (per RECIST 1.1 and iRECIST), progression-free survival (PFS), PFS rate at 12 and 24 weeks (cohort 3), and safety. Phase Ib will include at least 140 evaluable pts (80 pts in cohort 1 and 20 pts each in cohorts 2–4). Clinical trial information: NCT03964233 .

Trial in progress: A phase I/II, open-label, dose-escalation, safety and tolerability study of NC318 in subjects with advanced or metastatic solid tumors

TPS3166

Background: Siglec-15 (S15) is a member of the Siglec family (Sialic acid-binding Immunoglobulin Lectins), a distinct subgroup of immunoglobulin (Ig) superfamily proteins involved in discriminating self from non-self-immune regulation (Macauley MS et al. 2014). Nonclinical models demonstrate S15 mediates suppression of T cell proliferation and negatively regulates T cell function. NC318 is a first-in-class monoclonal antibody that blocks S15-mediated immune suppression and prevents tumor growth by normalizing T cell function and restoring anti-tumor immunity in the tumor microenvironment (Wang J et al. 2019). The clinical hypothesis of this study is that NC318 targeting of S15 can improve anti-tumor immune response and provide benefit in multiple oncology indications. Methods: This is a multi-center, first in human, phase 1/2, open-label, non-randomized study to determine the safety and tolerability, define maximum tolerated dose and/or pharmacologically active dose, assess preliminary efficacy, and explore predictive and pharmacodynamic biomarkers of NC318 in subjects with advanced or metastatic solid tumors. Key eligibility criteria included measurable disease based on RECIST v1.1 and consent for collection of biopsies at screening and on treatment (optional for phase 1). Phase 1 used a 3+3 dose escalation design to determine the recommended phase 2 dose (RP2D) and schedule of NC318 while identifying drug related toxicities (DLTs). Phase 2 enrollment is limited to non-small cell lung, ovarian, head and neck, and triple negative breast cancer subjects with PD-L1 tumor proportion scores <50% (additional tumor types are being evaluated for inclusion). Ongoing exploratory analyses include the assessment of predictive biomarkers associated with treatment benefit, and pharmacodynamic markers associated with study drug activity (e.g. evaluation of tumor biopsies and peripheral markers of inflammation). Phase 1 enrollment began October 2018 and completed in August 2019. The RP2D was defined and the phase 2 opened to enrollment October 2019. Clinical trial information: NCT03665285 .

Phase I expansion study of XMT-1536, a novel NaPi2b-targeting antibody-drug conjugate (ADC): Preliminary efficacy, safety, and biomarker results in patients with previously treated metastatic ovarian cancer (OC) or non-small cell lung cancer (NSCLC)

3549

Background: XMT-1536 is a first-in-class ADC targeting the sodium-dependent phosphate transport protein NaPi2b, broadly expressed in NSCLC and ovarian cancer. XMT-1536 utilizes the Dolaflexin platform to deliver 10-12 DolaLock auristatin payload molecules per antibody. In the dose-escalation portion of the Phase I study (NCT03319628), XMT-1536 showed clinical activity at doses >20mg/m2 with confirmed responses and prolonged stable disease in heavily pretreated OC and NSCLC patients, without preselection for NaPi2b expression. XMT-1536 was generally well-tolerated without the severe toxicities observed with other ADC platforms such as neutropenia, peripheral neuropathy, or ocular toxicity (Tolcher et al., ASCO 2019; Richardson et al., SGO 2020). Here, we report on the expansion (EXP) cohort, which included patients with fewer prior lines of therapy, in the ongoing Phase I study. Methods: Doses administered intravenously every 4 weeks (q4w) of 36 and 43 mg/m2 were evaluated in two cohorts (1) high grade serous ovarian, fallopian tube, or primary peritoneal cancer (OC) with up to 4 prior lines of therapy and (2) NSCLC adenocarcinoma; prior treatment with a platinum-based therapy, immune checkpoint inhibitor, and TKI, if indicated. Archival tumor tissue and tissue from a new tumor biopsy were required for retrospective evaluation of NaPi2b expression. Results: As of 10 February 2020, 23 patients (19 OC and 4 NSCLC) were enrolled in the EXP cohort: 16 dosed at 36 mg/m2 and 7 dosed at 43 mg/m2. Adverse events were generally similar to those previously reported, including transient AST elevation, fatigue, nausea, and pyrexia. Clinical responses and stable diseases have been observed. Efficacy data (objective response rate) and initial correlation of NaPi2b score with clinical response will be reported. Available data from all patients with data cutoff in May 2020 will be included. Conclusions: Overall, XMT-1536 treatment demonstrated clinical activity in high grade serous ovarian cancer and NSCLC adenocarcinoma and was generally well-tolerated with no new safety signal trends identified in the EXP. Clinical efficacy and the relevance of NaPi2b expression for treatment with XMT-1536 will be presented. Clinical trial information: NCT03319628 .

Phase Ib study of a novel, small-molecule MDM2 inhibitor APG-115 combined with pembrolizumab in U.S. patients with metastatic solid tumors

3512

Background: APG-115 activates p53-mediated apoptosis in tumor cells retaining wild-type TP53. It also functions as a host immune modulator and enhances antitumor activities when combined with PD-1 blockade preclinically. MDM2 amplification is associated with hyperprogression in patients treated with checkpoint inhibitors. Methods: The Phase Ib / II study was designed to evaluate APG-115 combined with pembrolizumab in patients with metastatic solid tumors (NCT03611868). APG-115 was administered orally every other day for 2 weeks, at dose ranging from 50 mg – 200 mg, with pembrolizumab at 200 mg IV on Day 1 of a 21-day cycle. Study objectives were to assess safety including dose-limiting toxicity (DLT), serious adverse events (SAEs), treatment-related AEs (TRAEs), pharmacokinetics (PK), pharmacodynamics (PD), and efficacy (assessed by RECIST v1.1), to determine recommended phase 2 dose (RP2D). Results: As of December 25, 2019, the enrollment of phase 1b study was completed. Total 19 patients had been treated in four APG-115 cohorts: 50 mg (n = 3), 100 mg (n = 3), 150 mg (n = 6), and 200 mg (n = 7). No DLT was observed, The TRAEs (≥15%) were nausea (47.4%), fatigue (36.8%), decreased platelet count (26.3%), and decreased appetite (21.1%), as well as diarrhea, vomiting, decreased neutrophil or white blood cell count, and hypothyroidism in 15.8% each. Grade > 3 TRAEs included decreased neutrophil and thrombocytopenia in 15.8% each. Two SAEs were treatment related: G3 febrile neutropenia and G3 adrenal insufficiency. No new safety finding from combination with Pembrolizumab. The RP2D of APG-115 was 150 mg. One patient with ovarian cancer has a CR lasting for 15 months, 2 patients had PR for 8-9 months: one NSCLC failed IO therapy, another with appendix cancer, and 7 had SD for 1.5-7 months. The objective response rate was 15.8%, and the disease control rate (DCR) was 52.6%. PK data indicated an approximately dose-proportional increase in APG-115 exposure over the range of 50-200 mg on Day 1. PD-PK analyses showed that serum macrophage inhibitory cytokine-1 (MIC-1) increase was time and dose dependent, the MIC-1 elevation correlated with APG-115 exposure, indicating p53 activation in these patients. Conclusions: APG-115 in combination with pembrolizumab is well tolerated. Encouraging antitumor effects were observed in several tumor types. The phase II study is ongoing in the cancer patients with specific bio-marker profiling. Clinical trial information: NCT03611868 .

Phase I dose-escalation trial of the oral AKT inhibitor uprosertib in combination with the oral MEK1/MEK2 inhibitor trametinib in patients with solid tumors

PURPOSE

This study aimed to determine the safety, tolerability, and recommended phase II doses of trametinib plus uprosertib (GSK2141795) in patients with solid tumors likely to be sensitive to MEK and/or AKT inhibition.

METHODS

This was a phase I, open-label, dose-escalation, and dose-expansion study in patients with triple-negative breast cancer or BRAF-wild type advanced melanoma. The primary outcome of the expansion study was investigator-assessed response. Among 126 enrolled patients, 63 received continuous oral daily dosing of trametinib and uprosertib, 29 received various alternative dosing schedules, and 34 were enrolled into expansion cohorts. Doses tested in the expansion cohort were trametinib 1.5 mg once daily (QD) + uprosertib 50 mg QD.

RESULTS

Adverse events (AEs) were consistent with those reported in monotherapy studies but occurred at lower doses and with greater severity. Diarrhea was the most common dose-limiting toxicity; diarrhea and rash were particularly difficult to tolerate. Overall, 59% and 6% of patients reported AEs with a maximum severity of grade 3 and 4, respectively. Poor tolerability prevented adequate delivery of uprosertib with trametinib at a concentration predicted to have clinical activity. The study was terminated early based on futility in the continuous-dosing expansion cohorts and a lack of pharmacological or therapeutic advantage with intermittent dosing. The objective response rate was < 5% (1 complete response, 5 partial responses).

CONCLUSIONS

Continuous and intermittent dosing of trametinib in combination with uprosertib was not tolerated, and minimal clinical activity was observed in all schedules tested.

Abstract A088: Novel anti-EGFR antibody-drug conjugate AVID100: A phase 2a trial in patients with EGFR-overexpressing advanced solid tumors

Background: Currently, no therapies are approved specifically for EGFR-overexpressing tumors. AVID100 is a novel anti-EGFR antibody drug conjugate (ADC, DM1 payload) that was rationally designed for anti-tumor efficacy without accompanying on-target, off-tumor toxicity by employing an EGFR function-blocking antibody moiety. Although EGFR is overexpressed in a multitude of malignancies including squamous non-small cell lung cancer (sqNSCLC), head and neck carcinoma (HNSCC) and triple-negative breast cancer (TNBC), historically limited activity has been reported for EGFR monoclonal antibodies or EGFR TKIs in unselected patients. This emphasizes the need to develop novel and more efficacious agents targeting EGFR, and for biomarker- directed approaches to enrich for patients likely to respond. In pre-clinical models, AVID100 showed potent anti-tumour efficacy and a Phase 1 dose-escalation study in patients with advanced solid malignancies concluded that AVID100 was well tolerated at doses expected to be therapeutically active. An RP2D of 220 mg/m2 (~6 mg/kg) was established. Methods: This open-label, multicenter, multicohort, prospective Phase 2a study (NCT03094169) is designed to further evaluate the safety, tolerability, and preliminary efficacy of AVID100 when administered at 6 mg/kg Q3W per iv infusion in patients with locally advanced/unresectable or metastatic solid tumor malignancies of epithelial origin, and with documented EGFR over-expression. Additional endpoints include PK profiling and exploratory biomarkers. sqNSCLC and HNSCC patients with EGFR IHC of 3+ as well as mTNBC patients whose EGFR IHC shows 3+ intensity in ≥ 50% of tumor cells, or ≥ 2+ intensity in ≥ 75% of tumor cells, are eligible to enroll. Patients must have measurable disease according to RECIST v1.1 at enrolment and disease status is assessed radiographically every 6 weeks. EGFR over-expression positivity is established by a validated IHC assay (DAKO EGFRpharmDX) conducted by a central laboratory. Initial validation of the EGFR IHC was carried out retrospectively on archival tissue microarrays (US Biomax, Derwood, MD) from advanced sqNSCLC, HNSCC and TNBC patients. Results Initial validation of the EGFR IHC assay conducted with archival tissue samples yielded EGFR 3+ positivity in ≥ 50% of tumor cells for 30% (32 out of 105 samples tested) of sqNSCLC and 22% (31 out of 140) of HNSCC samples. Among TNBC samples tested, 6% were EGFR 3+ in ≥ 50% of tumor cells and 25% EGFR 2 or 3+ in ≥ 50% of tumor cells (16 and 62 out of 249, respectively). The prospective Phase 2a trial assessing AVID100 in patients selected for EGFR overexpression was is actively accruing and one sqNSCLC, four SCCHN and three TNBC patients had been enrolled at time of writing. Conclusions A significant proportion of retrospectively assessed sqNSCLC, HNSCC and TNBC patient samples were found to overexpress the EGFR. The prospective Phase 2a trial assessing AVID100, a novel growth factor receptor function-blocking anti-EGFR ADC, remains ongoing and updated results will be presented at the meeting.

Citation Format: Jason Melear, Nehal Lakhani, Joyce A O'Shaughnessy, Sharon T Wilks, Saad Khan, Sree R Chandana, Anthony W Tolcher, Kyri P Papadopoulos, Yvette Cole, Karla Rivas, Ria Ghosh, Sandra Sinclair, Robert Lutz, Paul I Nadler, Debra L Wood, Barbara Burtness. Novel anti-EGFR antibody-drug conjugate AVID100: A phase 2a trial in patients with EGFR-overexpressing advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A088. doi:10.1158/1535-7163.TARG-19-A088

Abstract A086: Phase Ib study of a novel MDM2 inhibitor APG-115, in combination with pembrolizumab in patients with metastatic solid tumors in U.S

Keywords: MDM2; Immuno-oncology; PD-1 Background APG-115 is an orally active small-molecule MDM2 inhibitor that potently binds MDM2 protein, restores TP53 function, and activates p53 - mediated apoptosis in tumor cells retaining wild-type p53. Preclinical studies demonstrated that APG-115 promoted the production of proinflammatory cytokines in T cells, enhanced CD4+ T cell activation, and increased PD-L1 expression on tumor cells. Enhanced antitumor activity was demonstrated in syngeneic tumor models after APG-115 combined with PD-1 blockade. Retrospective clinical analyses suggested that MDM2 amplification is associated with hyper-progression in the patients treated with check point inhibitors. Keywords: MDM2; Immuno-oncology; PD-1 In general, by targeting MDM2-p53 pathway, APG-115 in combination with PD-1/PD-L1 blockade may provide a novel strategy to reverse immunosuppression and/or enhance antitumor immunity in the cancer patients who were either failed to standard therapies or resistant to IO therapies. Methods This dose escalation study (NCT03611868) combines APG-115 with pembrolizumab for the treatment of patients with metastatic solid tumors. Four dose levels of APG-115 have been tested: 50, 100, 150, and 200mg. APG-115 is administrated orally every other day (QOD) for consecutive 2 weeks of a 21-day-cycle with pembrolizumab at 200mg IV on day1 of a 21-day-cycle. Results Through June 15, 2019, a total of 14 patients have been treated in 4 cohorts of APG-115 in combination with pembrolizumab IV q3weeks. No cycle 1 DLTs have been observed up to and including 200 mg APG-115 at total doses of APG115 that are equivalent to the single agent MTD of APG-115 alone. Eleven patients experienced at least 1 TEAE. The most common TRAEs (≥10%) were nausea (42.9%), neutrophil count decreased (21.4%), vomiting (14.3%), decreased appetite (14.3%), diarrhea (14.3%), platelet count decreased (14.3%), white blood cell count decreased (14.3%), and fatigue (14.3%). Four patients experienced at least 1 grade 3 or higher TRAE beyond course 1 including neutrophil count decreased (21.4%). Five SAEs occurred in 3 patients, but only one grade 3 febrile neutropenia was treatment related. One patient with advanced ovarian cancer with a germline ATM mutation, refractory to 6 prior lines of therapy, has a sustained “confirmed CR” that continues beyond 12 cycles at the 100mg cohort. A patient with advanced NSCLC in 100mg cohort has received “confirmed PR” (still ongoing) after failed prior 5 lines of therapies including 3 months’ nivolumab treatment; 5 patients had SD after two cycle treatments, 2 of them ongoing. PK analyses indicates an approximately dose proportional increase in exposure across dose levels from 50 to 100 mg with plasma concentrations that exceed those that portend MDM2 inhibition. Preliminary pharmacodynamic (PD) results showed that the serum macrophage inhibitory cytokine-1 (MIC-1) levels are elevated in the APG-115 treated patients, suggesting a potential p53 activation in patients. Conclusion APG-115 in combination with pembrolizumab is well tolerated. The MTD has not been exceeded at full doses of APG-115. Promising anti-tumor effects have been seen in several tumor types when in combination with pembrolizumab. Expansion cohorts in molecularly selected patients is planned.

Citation Format: Anthony W Tolcher, Raghad Karim, Yuefen Tang, Jiao Ji, Hengbang Wang, Lichuang Meng, Angela Kaiser, Jennifer Coe, Eric Liang, Christina Rosas, Dajun Yang, Yifan Zhai. Phase Ib study of a novel MDM2 inhibitor APG-115, in combination with pembrolizumab in patients with metastatic solid tumors in U.S. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A086. doi:10.1158/1535-7163.TARG-19-A086