A first-in-human phase I study of the PD-1 inhibitor, retifanlimab (INCMGA00012), in patients with advanced solid tumors (POD1UM-101)

BACKGROUND

Retifanlimab is a humanized, hinge-stabilized immunoglobulin G4κ monoclonal antibody against human programmed cell death protein 1 (PD-1). This first-in-human, phase I study assessed the safety and efficacy of retifanlimab in patients with advanced solid tumors and identified optimal dosing.

PATIENTS AND METHODS

POD1UM-101 was conducted in two parts: (i) dose escalation-evaluated retifanlimab [1 mg/kg every 2 weeks (q2w), 3 or 10 mg/kg q2w or every 4 weeks (q4w)] in patients with relapsed/refractory, unresectable, locally advanced or metastatic solid tumors; (ii) cohort expansion-biomarker-unselected tumor-specific cohorts [endometrial, cervical, sarcoma, non-small-cell lung cancer (NSCLC)] received retifanlimab 3 mg/kg q2w, and tumor-agnostic cohorts received flat dosing [375 mg every 3 weeks (q3w), or 500 and 750 mg q4w]. Primary objectives were safety and tolerability; secondary objective was efficacy in selected tumor types.

RESULTS

Thirty-seven patients were enrolled in dose escalation, 134 in PD-1 therapy-naïve tumor-specific cohort expansion (endometrial, n = 29; cervical, NSCLC, soft tissue sarcoma, each n = 35), and 45 in flat dosing (375 mg q3w, 500 and 750 mg q4w, each n = 15). No dose-limiting toxicities occurred during dose escalation; maximum tolerated dose was not reached and 3-mg/kg q2w expansion dose was selected based on safety and pharmacokinetic data. Immune-related adverse events were experienced by 40 patients (30%) in tumor-specific cohorts (most frequently hypothyroidism, hyperthyroidism, colitis, nephritis) and 6 (13%) in flat dosing (most frequently hypothyroidism, hyperthyroidism). Objective response rate (95% confidence interval) was 14% (4.8 to 30.3), 14% (3.9 to 31.7), 20% (8.4 to 36.9), and 3% (0.1 to 14.9) in advanced NSCLC, endometrial, cervical, and sarcoma tumor-specific cohorts that progressed after multiple prior systemic therapies.

CONCLUSIONS

Retifanlimab demonstrated clinical pharmacology, safety, and antitumor activity consistent with the programmed death (ligand)-1 inhibitor class. POD1UM-101 results support further exploration of retifanlimab as monotherapy and backbone immunotherapy in combination treatments, with recommended doses of 500 mg q4w and 375 mg q3w.

Pharmacokinetics and immunogenicity of eftozanermin alfa in subjects with previously-treated solid tumors or hematologic malignancies: results from a phase 1 first-in-human study

PURPOSE

Eftozanermin alfa is a second-generation tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor agonist that enhances death receptor 4/5 clustering on tumor cells to induce apoptosis. We report the pharmacokinetics and immunogenicity of eftozanermin alfa administered intravenously to 153 adults with previously-treated solid tumors or hematologic malignancies from the first-in-human, open-label, dose-escalation and dose-optimization study.

METHODS

Dose escalation evaluated eftozanermin alfa monotherapy 2.5-15 mg/kg on Day 1 or Days 1/8 of a 21-day cycle. Dose optimization evaluated eftozanermin alfa monotherapy or combination therapy with either oral venetoclax 400-800 mg daily (eftozanermin alfa 1.25-7.5 mg/kg Days 1/8/15 of a 21-day cycle) or chemotherapy (eftozanermin alfa 3.75 or 7.5 mg/kg Days 1/8/15/22 of a 28-day cycle and FOLFIRI regimen [leucovorin, 5-fluorouracil, and irinotecan] with/without bevacizumab on Days 1/15 of a 28-day cycle).

RESULTS

Systemic exposures (maximum observed concentration [Cmax] and area under the concentration-time curve [AUC]) of eftozanermin alfa were approximately dose-proportional across the entire dose escalation range with minimal to no accumulation in Cycle 3 versus Cycle 1 exposures. Comparable exposures and harmonic mean half-lives (35.1 h [solid tumors], 31.3 h [hematologic malignancies]) were observed between malignancy types. Exposures (dose-normalized Cmax and AUC) in Japanese subjects were similar to non-Japanese subjects. Furthermore, eftozanermin alfa/venetoclax combination therapy did not have an impact on the exposures of either agent. Treatment-emergent anti-drug antibodies were observed in 9.4% (13/138) of subjects.

CONCLUSIONS

The study results, including a pharmacokinetic profile consistent with weekly dosing and low incidence of immunogenicity, support further investigation of eftozanermin alfa.

TRIAL REGISTRATION ID

NCT03082209.

First-in-Human Study with Preclinical Data of BCL-2/BCL-xL Inhibitor Pelcitoclax in Locally Advanced or Metastatic Solid Tumors

PURPOSE

B-cell lymphoma-extra-large (BCL-xL) regulates apoptosis and is an attractive anticancer therapeutic target. However, BCL-xL inhibition also kills mature platelets, hampering clinical development. Using an innovative prodrug strategy, we have developed pelcitoclax (APG-1252), a potent, dual BCL-2 and BCL-xL inhibitor. Aims of this study were to characterize the antitumor activity and safety of pelcitoclax and explore its underlying mechanisms of action (MOA).

PATIENTS AND METHODS

Cell line-derived xenograft and patient-derived xenograft (PDX) models were tested to evaluate antitumor activity and elucidate MOA. Subjects (N = 50) with metastatic small-cell lung cancer and other solid tumors received intravenous pelcitoclax once or twice weekly. Primary outcome measures were safety and tolerability; preliminary efficacy (responses every 2 cycles per RECIST version 1.1) represented a secondary endpoint.

RESULTS

Pelcitoclax exhibited strong BAX/BAK‒dependent and caspase-mediated antiproliferative and apoptogenic activity in various cancer cell lines. Consistent with cell-based apoptogenic activity, pelcitoclax disrupted BCL-xL:BIM and BCL-xL:PUMA complexes in lung and gastric cancer PDX models. Levels of BCL-xL complexes correlated with tumor growth inhibition by pelcitoclax. Combined with taxanes, pelcitoclax enhanced antitumor activity by downregulating antiapoptotic protein myeloid cell leukemia-1 (MCL-1). Importantly, pelcitoclax was well tolerated and demonstrated preliminary therapeutic efficacy, with overall response and disease control rates of 6.5% and 30.4%, respectively. Most common treatment-related adverse events included transaminase elevations and reduced platelets that were less frequent with a once-weekly schedule.

CONCLUSIONS

Our data demonstrate that pelcitoclax has antitumor activity and is well tolerated, supporting its further clinical development for human solid tumors, particularly combined with agents that downregulate MCL-1.

Abstract P3-08-05: Correlation of Trop2 expression with in vivo sensitivity to sacituzumab govitecan in a panel of breast XPDX models

Background: Sacituzumab govitecan (SG) is an antibody-drug conjugate targeting Trop2 with an SN-38 payload recently approved for pretreated patients with locally advanced or metastatic triple-negative breast cancer (TNBC). The XenoSTART Patient-Derived Xenograft (XPDX) breast cancer platform includes over 180 models spanning all subtypes characterized with immunohistochemistry (IHC) including ER, PR, and HER2 protein levels, genomic and transcriptomic sequencing, and in vivo drug sensitivity. To better understand potential benefit of SG in breast cancers other than TNBC and further annotate our platform, Trop2 protein levels were determined in all breast models by IHC. We evaluated tumor growth inhibition by SG in 125 of our XPDX breast models and compared protein expression with agent activity. Methods: 180 breast XPDX models were evaluated for Trop2 expression (AF650, R&D Systems) and 125 were evaluated in vivo against SG; responses were grouped by ER and Trop2 status (+/-). Models were grown subcutaneously in female athymic nude mice and ER+ models supplemented with estradiol. Models were also characterized for PR, HER2, and AR protein expression by IHC and profiled using WES and RNAseq. For in vivo studies, SG was administered by intravenous injection biweekly for two cycles at 1 mg, flat; endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C< 0%) versus Day 0 tumor volume was also reported. Results: 180 breast models were examined by IHC with 75/180 (42%) classified as ER+ and 105/180 (58%) ER-. In ER+ models 38/75 (51%) were Trop2+ and 37/75 (49%) Trop2-, and in ER- models 41/105 (39%) were Trop2+ and 64/105 (61%) Trop2-. In vivo, 20% of ER+/Trop2+ models reported sensitivity to SG, most notably models from patients with acquired resistance to CDK4/6 inhibitors, including STM001 and ST4316B. Interestingly, >70% of ER+/HER2+/Trop2+ models were insensitive to SG, including ST225 and ST340. Of 41 ER-/Trop2+ models, approximately 40% reported some response to SG with 50% of these sensitive to therapy, including ST5954 established from a patient who began treatment with SG following sample collection and is currently in remission. >75% of Trop2- models were insensitive to SG regardless of ER status. Conclusion: We screened 180 models in our XPDX breast cancer platform for Trop2 expression and compared expression with in vivo SG efficacy in 125 models. Analysis is underway to correlate receptor and molecular profiles with SG sensitivity in breast models and we are expanding expression and in vivo testing to additional indications.

Citation Format: Alyssa Simonson, Johnnie Flores, Ebony Anderson, Crystal Moreno, George Plasko, Kyriakos P. Papadopoulos, Amita Patnaik, Drew Rasco, Gladys Rodriguez, Amy Lang, Muralidhar Beeram, Luis Rodriguez, Ronald Drengler, Steven Abbate, Hanni Salih, Lon Smith, Maryam Elmi, Brittany DeBerry, Arthur Rosenthal, Tatiana Hernandez, Nehal Lakhani, Manish Sharma, Michael Wick. Correlation of Trop2 expression with in vivo sensitivity to sacituzumab govitecan in a panel of breast XPDX models [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 P3-08-05.

Abstract P4-01-35: A Phase 1 Study of the Oral CDK7 Inhibitor XL102 as a Single Agent and in Combination Therapy in Patients With Advanced Solid Tumors (QUARTZ-101): Initial Results From the Dose-Escalation Stage

Background: Cyclin-dependent kinase 7 (CDK7) plays a significant role in the cell cycle via activation of CDKs 1, 2, 4, and 6, and regulates transcription via phosphorylation of RNA polymerase II and the estrogen receptor. CDK7 overexpression has been reported in several tumor types, including hormone receptor-positive breast cancer (HR+ BC), triple-negative BC (TNBC), small-cell lung cancer, and epithelial ovarian cancer (EOC). In all major BC subtypes, CDK7 overexpression is associated with poor prognosis. XL102 is a potent, orally bioavailable, highly selective covalent CDK7 inhibitor. QUARTZ-101 is a first-in-human, open-label trial (NCT04726332) evaluating the safety, tolerability, and optimal dose of XL102 as a single agent and in combination regimens in patients with solid tumors, with expansion in subsequent tumor cohorts of advanced HR+ BC, TNBC, EOC, and metastatic castration-resistant prostate cancer (mCRPC). Presented here are initial results from the dose-escalation stage for single-agent XL102 (cohort A). Methods: In the single-agent dose-escalation stage, patients received XL102 orally at multiple dose levels (DLs) using a modified interval 3+3 design: once daily at 20 mg (DL A1), 40 mg (DL A2), 80 mg (DL A3), and 120 mg (DL A4); and twice daily at 40 mg (DL A5). Eligible patients had confirmed inoperable, locally advanced, metastatic, or recurrent solid tumors and ECOG performance status (PS) of 0 or 1; any CNS disease must have been adequately treated and stable for ≥4 weeks. Patients with previous exposure to XL102 or other selective CDK7 inhibitors were excluded, as were patients with uncontrolled, significant intercurrent or recent illness. Prior use of CDK4/6 inhibitors was allowed. The primary objective of dose escalation was to determine the maximum tolerated dose (MTD) and/or recommended dose (RD) of XL102; secondary objectives included safety and tolerability, pharmacokinetics (PK), and drug-drug interactions. Results: At data cutoff of May 13, 2022, twenty patients with various advanced solid tumors (100% stage IV) were enrolled in dose-escalation stage cohort A and treated with single-agent XL102 (DL A1 n=3; A2 n=3; A3 n=7; A4 n=4; A5 n=3). Median age was 67 (range 43–84) years, 85% were female, and 75% had an ECOG PS of 1. Six patients remained on XL102 including 2 treated for >6 months with stable disease, both had received prior CDK4/6 inhibitors (HR+BC and liposarcoma). There were no dose-limiting toxicities at any DL, and MTD/RD has not been determined. Treatment-emergent adverse events (TEAEs) occurred in 95% of patients, with 4 (20%) grade 3 and 0 grade 4 TEAEs; there were no grade 5 treatment-related AEs. Treatment discontinuations were mostly due to radiographic progression (n=8); longest treatment duration was 6.7+ months and ongoing. XL102 demonstrated rapid absorption with a Tmax of approximately 1–2 h and elimination half-life of 5– 8 h. Target occupancy was exposure-dependent and prolonged relative to XL102 PK, consistent with covalent binding to CDK7. Conclusions: Single-agent XL102 was well tolerated at the DLs tested. Updated data, as well as PK results, will be presented. Expansion cohorts in HR+BC, TNBC, EOC, and mCRPC will be initiated once a recommended dose for the expansion-cohort stage is determined.

Citation Format: Amita Patnaik, Minal Barve, Manali Bhave, Vivek Subbiah, Drew Rasco, Aarohi Bhatt, Jing Li, Svetlana Andrianova, Geoffrey Shapiro. A Phase 1 Study of the Oral CDK7 Inhibitor XL102 as a Single Agent and in Combination Therapy in Patients With Advanced Solid Tumors (QUARTZ-101): Initial Results From the Dose-Escalation Stage [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 P4-01-35.

Abstract P1-13-22: Establishment and characterization of two ER+/HER2- XPDX models developed sequentially before and after acquired resistance to the CDK4/6 inhibitor palbociclib from a patient with metastatic breast cancer

Background: Several CDK4/6 inhibitors have recently been approved in combination with letrozole or fulvestrant in hormone receptor-positive breast cancer. Although this combination therapy has been found effective in some patients, resistance often develops. To aid in developing new therapies for CDK4/6i-resistant breast cancer and better understand potential resistance mechanisms, we established two XenoSTART Patient-Derived Xenograft (XPDX) models representing ER+/HER2- breast cancer from tissue samples collected seventeen months apart from the same patient before and after palbociclib therapy. These models designated ST4887 and ST4887B were developed and characterized for receptor expression, genomic alterations, and in vivo drug sensitivities toward multiple chemotherapies and targeted agents, including CDK4/6i and fulvestrant. Methods: Models ST4887 and ST4887B were established from metastatic samples collected from a Caucasian female with ER+/HER2- metastatic breast cancer; ST4887 was collected at age 38 from a femur mass biopsy following several treatment regimens including paclitaxel/doxorubicin/cyclophosphamide, radiation and tamoxifen. ST4887B was collected at age 39 from a liver biopsy following treatment with palbociclib/letrozole then palbociclib/fulvestrant, and finally ixabepilone/capecitabine. Both were grown subcutaneously in female athymic nude mice supplemented with exogenous estradiol. The resulting models were passaged, and receptor expression confirmed immunohistochemically; genomic analysis, including WES and RNAseq, was performed to further characterize models. For in vivo studies, both models were evaluated using several chemotherapy and targeted agents alone and in combination including cisplatin, docetaxel, CDK4/6i, fulvestrant, letrozole, olaparib, niraparib, and sacituzumab. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C=< 0) versus Day 0 tumor volume was also reported. Results: ST4887 and ST4887B retained comparable receptor expression (ER=3+/HER2=1+) over tested passages with similar histology compared to archival clinical samples. DNA/RNA sequencing identified several conserved variants including a somatic BRCA2 truncation (BRCA2Y2660*); transcriptomic analysis revealed upregulation of several related genes but no notable fusions. In vivo, both models were insensitive to cisplatin or docetaxel, however ST4887 but not ST4887B was sensitive to fulvestrant or CDK4/6i therapies, although abemaciclib demonstrated some activity toward ST4887B. PARP inhibitors were active toward ST4887 and to a lesser extent ST4887B, while sacituzumab did not have a significant effect on either model. Conclusion: We established and characterized two XPDX models from the same patient before and after acquired resistance to the CDK4/6i palbociclib. Both models were found to retain receptor status and drug sensitivities similar to the patient at the time of sample collection. These models can be utilized as a valuable tool in better understanding acquired resistance to palbociclib.

Citation Format: Ashwin Varma, Johnnie Flores, Alyssa Simonson, Anna Stackpole, Kyriakos P. Papadopoulos, Amita Patnaik, Drew Rasco, Muralidhar Beeram, Marisa Sandera, Michael Wick. Establishment and characterization of two ER+/HER2- XPDX models developed sequentially before and after acquired resistance to the CDK4/6 inhibitor palbociclib from a patient with metastatic breast cancer [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 P1-13-22.

Abstract 1092: Correlation of platinum sensitivity with donor patient treatment status in a panel of breast, ovary, uterine, and lung XPDX models

Background: First-line treatment for some cancer types includes platinum-based therapy. While the rate of initial response to treatment is high, most patients develop platinum-resistant disease. Current salvage therapy provides benefit to some patients, demonstrating the need for additional effective therapies. To assist in identifying new therapies, we have established XenoSTART patient-derived xenograft (XPDX) models representing breast, ovary, uterine, and lung cancers. Each model was characterized by DNA/RNA analysis, sensitivity to platinum treatment, and annotated with donor patient treatment status at the time of sample collection.

Methods: 210 XPDX models were evaluated in this screen including 66 breast, 56 ovary, 36 uterine, and 52 lung xenografts. WES and RNAseq were performed on each model and patient treatment history and outcome annotated. For in vivo studies, models were implanted into female nudes and administered (IP; q7dx3) 3 m/k cisplatin or 60 m/k carboplatin. Study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive.

Results: Study results are summarized below in Table 1:

Sequencing identified several variants in resistant, chemo-naïve models including point mutations in RAS/RAF/MET/PIK3CA genes and others, while sensitive models lacked common driver mutations.

Conclusion: We have characterized 210 XPDX models. Uterine models were most often resistant to platinum, while almost 1/2 of ovary and 1/3 of breast models were sensitive, regardless of treatment status. Only 15% of lung models were sensitive to platinum; cancer driver variants were found in several models. Overall, we report differential platinum sensitivity in a panel of diverse models useful in understanding mechanisms of resistance and for development of effective therapies in platinum-resistant cancers.

Table 1. Type Breast Ovary Uterine Lung Total 66 56 36 52 # Sensitive 25 25 9 8 % 38% 45% 25% 15% Naïve 11 16 8 5 % 44% 64% 89% 63% P-1st 6 6 1 2 % 24% 24% 11% 25% P-2nd+ 6 3 0 1 % 24% 12% 0% 13% # Insensitive 41 31 27 44 % 62% 55% 75% 85% Naïve 11 9 20 21 % 27% 29% 74% 48% P-1st 14 10 5 13 % 34% 32% 19% 30% P-2nd+ 16 12 2 10 % 39% 39% 7% 23% Naïve=No Prior Treatment; P-1st=Post 1st Line Therapy; P-2nd=Post 2nd+ Line Therapy

Citation Format: Alyssa Simonson, Johnnie Flores, Lizette Firova, Christian Hernandez, Morgan Harris, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Allan White, Lon Smith, Ronald Drengler, Amy Lang, Murali Beeram, Michael J. Wick. Correlation of platinum sensitivity with donor patient treatment status in a panel of breast, ovary, uterine, and lung XPDX models [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 1092.

Abstract 412: Correlation of drug sensitivity to clinical response in XPDX models established from patients treated with KRAS-G12C-inhibitor therapy

Background: We previously reported (RAS AACR 2022) a preclinical screen testing KRASG12C-inhibitors (KRASG12C-i) in 13 colorectal and 13 lung KRASG12C XPDX models; all tested models were from patients naïve to KRASG12C-i. To better understand mechanisms of resistance in this agent class, we established three lung XPDX models designated ST5185B, ST5431B, and ST5489 from patients before therapy with a KRASG12C-i. We also established one colorectal XPDX, designated ST4859, post therapy. Once established these models were molecularly characterized, in vivo sensitivity to sotorasib and adagrasib determined, and results compared with clinical response. Ex vivo cultures and 3D-XPDX࣪ studies were also performed evaluating both compounds comparing drug sensitivity.

Methods: Lung: ST5185B was established from a pretreated 68-year-old male; ST5431B was established from a chemo-naïve 67-year-old male; additional samples were collected during and after progression on KRASG12C-i and are currently in development. ST5489 was established from a pretreated 64-year-old female. CRC: ST4859 was established from a 57-year-old female pretreated with a KRASG12C-i; all patients received at least one cycle of KRASG12C-i therapy. Models were WES and RNA sequenced and sotorasib and adagrasib sensitivity determined. For each study, agents were dosed PO once daily at 100 mg/kg; study endpoints included tumor volume and time from treatment initiation with %T/C values reported at study completion; a %T/C of ≤ 20% was considered sensitive.

Results: In all models sequencing confirmed KRASG12C and other variants previously identified with clinical studies. In vivo studies identified ST5185B as resistant to sotorasib (%T/C=70%) and adagrasib (%T/C=86%); this donor patient progressed after six weeks on KRASG12C-i therapy. ST5431B reported sensitivity to both therapies; this donor patient had a partial response (50% decrease) for six months prior to progression. ST5489 reported sensitivity to sotorasib (%T/C=14%) and adagrasib (%T/C=8%); this donor patient interrupted dosing due to KRASG12C-i intolerance and discontinued therapy, with disease progression after five weeks. ST4859 reported resistance to both drugs; this donor patient had stable disease on KRASG12C-i therapy for approximately seven months prior to progression. Ex vivo cultures and 3D-XPDX࣪ studies from all models reported sensitivity to both agents similar to in vivo studies.

Summary: We developed, evaluated, and correlated in vivo sensitivity of sotorasib and adagrasib in a panel of four XPDX models established from patients receiving KRASG12C-i therapy. Studies are underway to generate drug-resistant clones of sensitive models and to elucidate mechanisms of drug resistance in ST4859.

Citation Format: Johnnie Flores, Alyssa Simonson, Peter Forofontov, Anna Stackpole, Drew Rasco, Amita Patnaik, Kyriakos Papadopoulos, Teresa DesRochers, Natalie Williams, Ronald Drengler, Lon Smith, Michael J. Wick. Correlation of drug sensitivity to clinical response in XPDX models established from patients treated with KRAS-G12C-inhibitor therapy [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 412.

Abstract CT152: Phase I study of MT-6402, a novel engineered toxin body (ETB) targeting PD-L1, in patients with PD-L1 expressing advanced solid tumors

This is the first-in-human study of MT-6402, a unique, first-in-class potent PD-L1-targeted engineered toxin body (ETB) capable of direct killing of PD-L1 expressing cells via rapid PD-L1-mediated internalization of a fused Shiga-like toxin A subunit (SLTA) resulting in permanent ribosomal inactivation. MT-6402 also delivers an HLA-A*02 restricted pp65 cytomegalovirus (CMV) antigen into PD-L1 expressing tumor cells leading to MHC-I presentation to existing CMV-specific cytotoxic T cells (antigen seeding). MT-6402 functions by targeting tumor and inhibitory immune cells directly and altering tumor immunophenotype to re-direct antiviral cytotoxic T cells into the tumor microenvironment. MT-6402 shows picomolar cytotoxic activity across several PD-L1 expressing cancer cell lines and treatment of human PBMCs results in selective depletion of PD-L1 positive cells. MT-6402 was well tolerated in non-human primates at doses above those which induce pharmacodynamic (PD) effect (reduction of CD14+ monocytes) in humans.

This first-in-human study in patients with PD-L1-expressing advanced solid tumors will employ a modified toxicity probability interval design to determine MTD and will then enroll additional subjects at the MTD, to further explore safety and efficacy and determine RP2D. Results of the first dose cohort (16 micrograms/kg) are presented.

Six patients received MT-6402. A significant and sustained reduction in CD14+ monocytes starting in cycle 2 was observed in patients on therapy beyond one cycle and was maintained with each MT-6402 administration, indicating HLA-independent PD effect consistent with preclinical observations. One HLA-A*02 and CMV+ patient with osseous metastases from NSCLC showed marked CMV-specific T-cell extravasation at day 8 and serum cytokine signatures consistent with antigen dependent responses and T cell mobilizations, suggesting engagement of MT-6402 antigen seeding. This patient has reduced intensity of metastatic bone lesions with 3/4 lesions resolving; the remaining lesion showing reduced uptake. Two patients had cytokine elevations at day 15, manifested by transient (1-12h), grade 2 infusion-related reactions and grade 2 cytokine release syndrome, which were subsequently prevented by steroid premedication. These results describe a novel approach to checkpoint modulation, leveraging direct PD-L1 cell kill and antigen seeding technology by the ETB. The results support further dose escalation and hold promise for development of MT-6402 for solid tumors, including in the R/R setting.

Citation Format: David R. Spigel, Eugene Ahn, Herbert L. Duvivier, Drew Rasco, Agnes Rethy, Chris Moore, Amy Yuet, Sandra Hankins, Swati Khanna, Joseph Dekker, Brian Van Tine. Phase I study of MT-6402, a novel engineered toxin body (ETB) targeting PD-L1, in patients with PD-L1 expressing advanced solid tumors [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 CT152.

Abstract 3109: Establishment and characterization of a panel of castrate-resistant prostate cancer XPDX models with differential enzalutamide response

Background: Preclinical models of prostate cancer are challenging to develop and maintain, especially those that grow in a castrated setting while maintaining receptor and antigen expression. To this end, we have established and characterized a panel of XenoSTART patient-derived (XPDX) prostate models using both intact and castrated athymic nude mice. These models, designated ST1273, ST2347, ST4017, and ST4420, were characterized for receptor expression, genomic alterations, and in vivo drug sensitivity to relevant therapies.

Methods: XPDX models representing prostate cancer were established from primary (ST1273) or metastatic (ST2347, ST4017, ST4420) biopsy samples implanted into intact athymic nude mice supplemented with exogenous testosterone. Resulting models were passaged and further developed in both intact and castrated athymic nudes until growth stabilization. Resulting models were characterized using genomic analysis, including WES and RNAseq, receptor expression, and in vivo drug sensitivity studies. Models found sensitive to enzalutamide were conditioned to resistance in vivo by chronic drug administration and resulting models (designated STxxxx/EZR) were characterized and compared with parent lines. For in vivo studies, activity of relevant treatments were benchmarked including enzalutamide administered once daily by oral gavage at 50 mg/kg and docetaxel administered by intravenous injection once weekly at 10 mg/kg. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive.

Results: Each model developed in a castrate or conditioned setting retained similar receptor expression to the parent model including positive AR (2+/3+) and PSMA (2+/3+) staining. Genomic characterization identified a PIK3CA mutation in ST1273 models (PIK3CAE545A), AR mutations in ST2347 (ART878A) and ST4017 (ARH875Y), and a TMPRSS2:ERG fusion in ST4420. In vivo, the ST1273 parent model was found sensitive to enzalutamide (%T/C=11%) but insensitive in castrated mice (%T/C=76%) and the ST1273/EZR model was resistant to enzalutamide in intact (%T/C=56%) or castrated (%T/C=100%) mice. The ST2347 parent model was also found sensitive to enzalutamide (%T/C=19%) but insensitive in castrated mice (%T/C=50%). ST4017 and ST4420 studies in intact and castrated mice are currently underway. All models were sensitive to docetaxel.

Conclusion: We have established and characterized a panel of prostate XPDX models using both intact and castrated athymic nude mice and conditioned resistance to enzalutamide by chronic drug administration. These models can be utilized as a valuable tool in better understanding castrate-resistant prostate cancer and in developing novel therapies for enzalutamide-resistant patients.

Citation Format: Johnnie Flores, Alyssa Simonson, Dustin Kneifel, Alejandra Diaz, Morgan Harris, Kyriakos Papadopoulos, Amita Patnaik, Drew Rasco, Scott Ulmer, Michael J. Wick. Establishment and characterization of a panel of castrate-resistant prostate cancer XPDX models with differential enzalutamide response [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 3109.

Abstract 353: Establishment and characterization of neuregulin-1 (NRG1) fusion driven XPDX models

Background: Neuregulin-1 (NRG1) rearrangements drive cancers by binding to ERBB3/ERBB2 heterodimers and activating downstream signaling. NRG1 fusion proteins have recently been identified in several cancer types including lung and ovary. To better understand the role of NRG1 fusions in cancer we established three XenoSTART patient-derived xenograft (XPDX) models driven by NRG1 rearrangements including two CD74-NRG1 lung models designated ST2891 and ST3204 and one SARAF-NRG1 ovary model designated ST2476. These models were established in athymic nude mice and characterized for receptor expression, genomic alterations, and in vivo drug sensitivity.

Methods: ST2891 was established from an excision biopsy collected from a 68-year-old male with NSCLC following treatment with carboplatin/paclitaxel and carboplatin/pemetrexed. ST3204 was established from a lymph node biopsy collected from a 63-year-old female with NSCLC following treatment with cisplatin/pemetrexed. ST2476 was established from primary tissue collected from a chemo naïve 61-year-old female with ovarian cancer. The resulting models were passaged and characterized using immunohistochemical and genomic analysis including WES and RNAseq. In vivo studies were performed testing various chemotherapy and targeted agents; study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C<0) versus Day 0 tumor volume was also reported.

Results: All models reported ERBB2 and ERBB3 staining in evaluated passages with similar histology compared with archival clinical samples. WES analysis of the three models did not identify any variants in EGFR/ERBB2-4/RAS/RAF genes. RNA sequencing revealed CD74-NRG1 or SARAF-NRG1 gene fusions independently confirmed using molecular studies. In vivo, both lung models were resistant to weekly cisplatin or T-DM1 and daily palbociclib (50 mg/kg) or daily afatinib up to 10 mg/kg. ST3204 was found sensitive to weekly pertuzumab (1 mg/kg). Both lung models were resistant to trastuzumab (1 mg/kg). The ST2476 ovary XPDX was found resistant to endocrine therapies and reported some sensitivity to weekly cisplatin.

Conclusion: We have established and characterized a panel of three XPDX models driven by NRG1 rearrangements including two CD74-NRG1 lung models and one SARAF-NRG1 ovary model. These models are valuable tools for further developing therapies targeting NRG1-driven cancers.

Citation Format: Alyssa Simonson, Johnnie Flores, Crystal Moreno, Justine Hruzek, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Ronald Drengler, Allan White, Jun Ma, Michael J. Wick. Establishment and characterization of neuregulin-1 (NRG1) fusion driven XPDX models [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 353.

Abstract P5-01-06: Establishment and characterization of luminal A breast XPDX models from patients with acquired resistance to CDK 4/6 inhibitors

Background: Several CDK 4/6 inhibitors have recently been approved in combination with letrozole or fulvestrant in hormone receptor-positive breast cancer. Although this combination therapy has been found effective in some patients, resistance often develops. To aid in developing new therapies for CDK4/6 inhibitor-resistant breast cancer and better understand potential resistance mechanisms, we established a panel of nine XPDX models from eight female patients with luminal A breast cancer at time of progression following acquired resistance to CDK4/6 inhibitor therapy. These models, designated ST940C, ST2056, ST3164B, ST3164B/PBR, ST3932, ST4316B, ST4378, STF160, and STM001B were developed in athymic nude mice and characterized for receptor expression, genomic alterations, and in vivo drug sensitivity. Methods: STF160 was established from a primary biopsy and ST3932 from a metastatic soft tissue lesion; the remaining models were established from malignant fluid samples collected at various stages of treatment post CDK4/6 inhibitor response and progression. The resulting models were passaged and challenged with CDK4/6 inhibitors to confirm resistance and fulvestrant to assess sensitivity. Receptor expression was determined immunohistochemically. Genomic analysis, including WES and RNAseq, were performed to characterize models and identify mechanisms of resistance. For in vivo studies, palbociclib and abemaciclib were dosed by oral administration once daily at 50 mg/kg and fulvestrant by subcutaneous administration once weekly at 2.5 mg. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C<0) versus Day 0 tumor volume was also reported. Results: All models retained ER expression in evaluated passages with similar histology compared with archival clinical samples; HER2 positivity was also confirmed in ST940C which was established from a clinically ER+/HER2+ patient. DNA/RNA sequencing identified several model-specific variants including the ESR1Y537S mutation in ST940C and ST2056 and the ESR1-CCDC170 fusion in ST3164B and ST3164B/PBR; BRCA2Q1089Sfs*10 was identified in ST4316B and PIK3CAE545G in ST4378. In vivo, seven models including ST3164B, ST3164B/PBR, ST3932, ST4316B, ST4378, STF160, and STM001B were found resistant (%T/C>20) to palbociclib or abemaciclib and single agent fulvestrant. ST940C and ST2056 were sensitive (%T/C≤20) to tested CDK4/6 inhibitors but resistant to fulvestrant. Conclusion: We have established and characterized a panel of nine XPDX models from eight female patients with luminal A breast cancer at time of progression following acquired resistance to CDK4/6 inhibitor therapy, seven of which were found resistant to single agent palbociclib and abemaciclib and all nine to fulvestrant. This panel can be utilized as a valuable tool in better understanding CDK4/6 inhibitor resistance and in developing novel therapies for CDK4/6 inhibitor-resistant patients.

Citation Format: Tatiana Hernandez, Dustin Kneifel, Alyssa Simonson, Johnnie R Flores, Sarah Quick, April Cabang, Alexandra Ulmer, Kyriakos Papadopoulos, Amy Lang, Gladys Rodriguez, Murali Beeram, Drew Rasco, Amita Patnaik, Scott Ulmer, Michael J Wick. Establishment and characterization of luminal A breast XPDX models from patients with acquired resistance to CDK 4/6 inhibitors [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-01-06.

Abstract P5-01-11: Nonclinical activity of fulvestrant in a panel of ER+ breast XPDX models representing clinically acquired and innate resistance to endocrine therapies

Background: Fulvestrant is a selective estrogen receptor modulator (SERM) approved as a single agent for estrogen receptor positive, HER2 negative breast cancer patients at various stages of disease and in combination with CDK4/6 inhibitors following endocrine therapy failure. Although this agent requires intramuscular injection, it has demonstrated superior activity and fewer side effects versus some oral endocrine treatments however, resistance to fulvestrant often develops. To better understand fulvestrant resistance and its utility in patients who have failed other endocrine therapies, we evaluated the agent in a panel of ER+ breast models established from patients at various stages of disease representing endocrine-sensitive and -resistant disease. Methods: Sixty-five previously developed ER+ breast XPDX models were evaluated in this study. Models were grown subcutaneously in female athymic nude mice supplemented with estradiol in drinking water when necessary. All models were characterized at early and late passages for estrogen receptor expression by immunohistochemistry and profiled using WES and RNAseq. For in vivo studies, fulvestrant was administered by subcutaneous injection at 2.5 or 5 mg per dose once weekly until study completion. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C<0) versus Day 0 tumor volume was also reported. Models were grouped by patient clinical treatment prior to sample collection and model establishment including chemo-naïve, endocrine therapies other than fulvestrant, non-endocrine therapies, and fulvestrant. Results: All models retained ER expression in evaluated passages with similar histology compared with archival clinical samples. DNA/RNA sequencing identified several model-specific variants including ESR1 point mutations and fusions. In this study, 22% of models represented chemo-naïve patients, 24% were from patients treated with non-endocrine therapies, 20% were from patients treated with fulvestrant and the remaining 34% from patients treated with endocrine therapies other than fulvestrant. In vivo, 40% of the chemo-naïve group reported sensitivity to fulvestrant including several models with tumor regressions. Activity of fulvestrant was reported in 25% of models in the non-endocrine therapies group and in 20% of models from patients treated with either fulvestrant or endocrine therapies other than fulvestrant. Several models resistant to fulvestrant from chemo-naïve or patients treated with non-endocrine therapies harbored driver mutations including ESR1, PIK3CA, and AKT1 variants or were HER2+. In models from patients pretreated with fulvestrant, those who had also received a CDK4/6 inhibitor were particularly resistant. Conclusion: We evaluated fulvestrant in a panel of ER+ breast XPDX models representing endocrine-sensitive and -resistant disease from both chemo-naïve and pretreated patients, and identified models responsive and resistant to fulvestrant therapy. This panel can be utilized as a valuable tool in better understanding fulvestrant and endocrine therapy resistance and in developing novel therapies for patients resistant to currently available hormonal therapies.

Citation Format: April Cabang, Crystal Moreno, Johnnie R Flores, Jenna Boedeker, Alyssa Simonson, Jun Ma, Amy Lang, Gladys Rodriguez, Arthur Rosenthal, Kyriakos Papadopoulos, Amita Patnaik, Drew Rasco, Lon Smith, Murali Beeram, Ronald Drengler, Luis Rodriguez, Steven Abbate, Scott Ulmer, Michael J Wick. Nonclinical activity of fulvestrant in a panel of ER+ breast XPDX models representing clinically acquired and innate resistance to endocrine therapies [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-01-11.

Abstract P5-01-09: Establishment and characterization of two simultaneously developed T-DM1-resistant, ER+/HER2+ XPDX models from the same patient with differential in vivo sensitivity to trastuzumab deruxtecan (DS-8201a)

Background: Trastuzumab deruxtecan (DS-8201a) is an antibody-drug conjugate (ADC) consisting of an anti-HER2 (human epidermal growth factor receptor 2) antibody linked to a topoisomerase I inhibitor payload using a cleavable tetrapeptide-based linker and was recently approved for unresectable or T-DM1-refractory HER2+ breast cancer. While some mechanisms for clinical T-DM1 resistance have been identified, less is known about acquired or innate resistance to DS-8201a. We established two XPDX models of ER+/HER2+ breast cancer from tissue and fluid samples collected simultaneously from the same patient. These models designated ST4480B and ST4480C were developed and characterized for receptor expression, genomic alterations, and in vivo drug sensitivities toward multiple chemotherapies and targeted agents including DS-8201a and T-DM1. Methods: ST4480B and ST4480C were established from a 70-year-old Caucasian female with ER+/HER2+ metastatic breast cancer pretreated with chemotherapy and targeted agents including T-DM1 for nine months followed by capecitabine/trastuzumab/tucatinib combination for one year prior to sample collections. ST4480B was established from a lymph node biopsy and ST4480C from a fluid sample collected the same day; both were grown subcutaneously in female athymic nude mice supplemented with estradiol. The resulting models were passaged and receptor expression confirmed immunohistochemically; genomic analysis, including WES and RNAseq, was performed to further characterize models. For in vivo studies, both models were evaluated with several chemotherapy and targeted agents alone and in combination including: trastuzumab, pertuzumab, T-DM1, DS-8201a, neratinib, tucatinib, alpelisib, everolimus, and irinotecan. In vivo study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20 versus control was considered sensitive. Tumor regression (%T/C=—<0) versus Day 0 tumor volume was also reported. Results: ST4480B and ST4480C retained comparable receptor expression (ER=2+/HER2=2+) over tested passages with similar histology compared with archival clinical samples. DNA/RNA sequencing identified several conserved variants including PIK3CAE545K and TP53Q192* mutations and an ESR1-CCDC170 fusion. However, two variants identified only in ST4480C sequences included PIK3CAG1007R and PTENS287L. In vivo, ST4480B and ST4480C were found resistant to T-DM1 up to 10 mg/kg weekly with an average %T/C of 46 and 100, respectively. However, DS-8201a treatment at 3 mg/kg weekly resulted in partial tumor regressions in ST4480B (%T/C=-68) while ST4480C was found resistant to the therapy up to 10 mg/kg weekly (%T/C=84%). Both models were found resistant to trastuzumab, pertuzumab, neratinib, tucatinib, and irinotecan but sensitive to both alpelisib and everolimus. Conclusion: We established two XPDX models representing T-DM1-resistant, ER+/HER2+ breast cancer from both tissue and fluid samples collected simultaneously from the same patient which were found differentially responsive to DS-8201a. These models can be utilized as a valuable tool in better understanding innate resistance to DS-8201a.

Citation Format: Johnnie R Flores, Anna Stackpole, Abimael Garza, Alexandra Ulmer, Alyssa Simonson, Kyriakos Papadopoulos, April Cabang, Jun Ma, Amita Patnaik, Drew Rasco, Amy Lang, Gladys Rodriguez, Murali Beeram, Michael J Wick. Establishment and characterization of two simultaneously developed T-DM1-resistant, ER+/HER2+ XPDX models from the same patient with differential in vivo sensitivity to trastuzumab deruxtecan (DS-8201a) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-01-09.

First-in-Class Anti-immunoglobulin-like Transcript 4 Myeloid-Specific Antibody MK-4830 Abrogates a PD-1 Resistance Mechanism in Patients with Advanced Solid Tumors

PURPOSE

In this first-in-human study (NCT03564691) in advanced solid tumors, we investigated a novel first-in-class human IgG4 monoclonal antibody targeting the immunoglobulin-like transcript 4 (ILT4) receptor, MK-4830, as monotherapy and in combination with pembrolizumab.

PATIENTS AND METHODS

Patients with histologically/cytologically confirmed advanced solid tumors, measurable disease by RECIST v1.1, and evaluable baseline tumor sample received escalating doses of intravenous MK-4830 every 3 weeks as monotherapy (parts A and B) and in combination with pembrolizumab (part C). Safety and tolerability were the primary objectives. Pharmacokinetics, objective response rate per RECIST v1.1, and molecular biomarkers were also evaluated.

RESULTS

Of 84 patients, 50 received monotherapy and 34 received combination therapy. No dose-limiting toxicities were observed; maximum tolerated dose was not reached. MK-4830 showed dose-related target engagement. Eleven of 34 patients in the dose-escalation phase who received combination therapy achieved objective responses; 5 previously had progressive disease on anti-PD-1/PD-L1 therapies. Exploratory evaluation of the association between response and pretreatment gene expression related to interferon-gamma signaling in tumors suggested higher sensitivity to T-cell inflammation with combination therapy than historically expected with pembrolizumab monotherapy, with greater response at more moderate levels of inflammation.

CONCLUSIONS

This first-in-class MK-4830 antibody dosed as monotherapy and in combination with pembrolizumab was well tolerated with no unexpected toxicities, and demonstrated dose-related evidence of target engagement and antitumor activity. Inflammation intrinsic to the ILT4 mechanism may be facilitated by alleviating the myeloid-suppressive components of the tumor microenvironment, supporting the target of ILT4 as a potential novel immunotherapy in combination with an anti-PD-1/PD-L1 agent.

First-in-human phase 1 study of the anti-TIGIT antibody vibostolimab as monotherapy or with pembrolizumab for advanced solid tumors, including non-small cell lung cancer

BACKGROUND

In this first-in-human phase 1 study, we investigated the safety and efficacy of the anti-TIGIT antibody vibostolimab as monotherapy or in combination with pembrolizumab.

METHODS

Part A enrolled patients with advanced solid tumors and part B enrolled patients with non-small cell lung cancer (NSCLC). Patients received vibostolimab 2.1-700 mg alone or with pembrolizumab 200 mg in part A and vibostolimab 200 mg alone or with pembrolizumab 200 mg in part B. Primary end points were safety and tolerability. Secondary end points included pharmacokinetics and objective response rate (ORR) per RECIST v1.1.

RESULTS

Part A enrolled 76 patients (monotherapy, 34; combination therapy, 42). No dose-limiting toxicities were reported. Across doses, 56% of patients receiving monotherapy and 62% receiving combination therapy had treatment-related adverse events (TRAEs); grade 3-4 TRAEs occurred in 9% and 17% of patients, respectively. The most common TRAEs were fatigue (15%) and pruritus (15%) with monotherapy and pruritus (17%) and rash (14%) with combination therapy. Confirmed ORR was 0% with monotherapy and 7% with combination therapy. In part B, 39 patients had anti-PD-1/PD-L1-naïve NSCLC (all received combination therapy) and 67 had anti-PD-1/PD-L1-refractory NSCLC (monotherapy, 34; combination therapy, 33). In patients with anti-PD-1/PD-L1-naive NSCLC: 85% had TRAEs-the most common were pruritus (38%) and hypoalbuminemia (31%); confirmed ORR was 26%, with responses occurring in both PD-L1-positive and PD-L1-negative tumors. In patients with anti-PD-1/PD-L1‒refractory NSCLC: 56% receiving monotherapy and 70% receiving combination therapy had TRAEs-the most common were rash and fatigue (21% each) with monotherapy and pruritus (36%) and fatigue (24%) with combination therapy; confirmed ORR was 3% with monotherapy and 3% with combination therapy.

CONCLUSION

Vibostolimab plus pembrolizumab was well tolerated and demonstrated antitumor activity in patients with advanced solid tumors, including patients with advanced NSCLC.

478 COM701 in combination with BMS-986207 (anti-TIGIT antibody) and nivolumab – preliminary results of safety, tolerability and pharmacokinetics in patients with advanced solid tumors (NCT04570839)

Background

COM701, a novel first-in-class immune checkpoint inhibitor (ICI) binds to poliovirus receptor related immunoglobulin domain containing (PVRIG) leading to enhanced activation of T and NK-cells. COM701 in combination with nivolumab has a favorable safety profile, is well tolerated and demonstrates antitumor activity.1 We hypothesized that the addition of BMS-986207 as a triplet thereby inhibiting the DNAM axis will have an acceptable safety/tolerability profile. We present preliminary results on safety/tolerability and pharmacokinetics (PK) parameters.

Methods

Using an accelerated titration and 3+3 study design we enrolled 14 patients (pts) with advanced solid tumors. Doses of COM701 were 0.3, 1, 3, 10 or 20 [mg/kg IV Q4 wks]; in combination with nivolumab and BMS-986207 (both 480 mg IV Q4 wks). Key objectives were to evaluate the safety and tolerability, to determine the recommended dose for expansion (RDFE) and to characterize preliminary pharmacokinetic parameters. Key inclusion criteria: Age ≥ 18 yrs, histologically confirmed locally advanced or metastatic solid malignancy and has exhausted all available standard treatments. Key exclusion criteria: history of immune-related toxicities on prior immunotherapy treatment leading to discontinuation.

Results

In the safety population [N=14], 12 pts reported treatment emergent adverse events (TEAEs). The most frequent TEAES [≥3 pts] were fatigue 5 pts (36%), pyrexia 3 pts (21%), vomiting 3 pts (21%). No DLTs were reported in any of the dose levels. The most frequent tumor types enrolled: CRC (n=3), and prostate, melanoma and OVCA/primary peritoneal cancer (n=2 each). Median number of prior therapies was 10 (range 1–19). Four pts had received prior immunotherapy. Serious adverse events [≥2 pts] were 2 pts (14%) with G3 abdominal pain, 2 pts (14%) with vomiting (1pt with G1/2 vomiting, 1 pt with G3 vomiting) all assessed by the investigator as unrelated to study drug. Preliminary PK profiles of COM701 were generally dose proportional.

Conclusions

COM701 in combination with BMS-986207 and nivolumab demonstrates a favorable safety, tolerability and PK profiles. COM701 20 mg/kg has been selected as the RDFE in combination with BMS-986207 and nivolumab (both 480 mg) all administered IV Q4 wks. The expansion cohorts are enrolling pts with platinum resistant ovarian cancer and endometrial cancer. Data cutoff 28 Jun 2021.

Acknowledgements

This study is in collaboration with Bristol Myers Squibb.

Trial Registration

NCT04570839

References

Vaena, DA, Fleming GF et al. COM701 with or without nivolumab: Results of an ongoing phase 1 study of safety, tolerability and preliminary antitumor activity in patients with advanced solid malignancies (NCT03667716). J Clin Oncol 2021;39: (suppl 15; abstr 2504).

Ethics Approval

The study obtained ethics approval form all the participating sites. All study participants gave informed consent before taking part.- 0002: START2020.15- 0003: 20210109- 0005: IRB20-1549- 0006: 21-060- 0007: IRB-AAAT4904- 0012: 2020-0755- 0013: STMW2020.16- 0015: 20210109

477 COM902 (Anti-TIGIT antibody) monotherapy – preliminary evaluation of safety, tolerability, pharmacokinetics and receptor occupancy in patients with advanced solid tumors (NCT04354246)

Background

COM902 is an IgG4 fully human high-affinity monoclonal antibody, inhibitor of TIGIT (T cell Ig and immunoreceptor tyrosine-based inhibitory motif [ITIM] domain) binding to poliovirus receptor (PVR). TIGIT blockade by COM902 was shown to enhance anti-tumor immunity in pre-clinical models. We hypothesized that COM902 as monotherapy will have an acceptable safety and tolerability profile in subjects with advanced solid tumors.

Methods

Utilizing an accelerated titration and 3+3 study design we enrolled 18 patients (pts) at the following COM902 doses 0.01, 0.03, 0.1, 0.3, 1, 3 and 10 mg/kg IV Q3 wks. Key primary objectives were to evaluate the safety, tolerability (CTCAE v5.0), to characterize the pharmacokinetics (PK) and to select a recommended dose for expansion (RDFE). An exploratory objective was evaluation of peripheral receptor occupancy (RO). Key inclusion criteria: Age ≥18 yrs, histologically/cytologically confirmed advanced malignancy who have exhausted all available standard therapy or not a candidate for standard therapy. Patients with performance status ECOG 0-1, prior ICI permissible. Dose-limiting toxicities (DLTs) were evaluated within a 21-day window in the 1st cycle of dose escalation.

Results

In the safety population [N=18], 12 pts reported treatment emergent adverse events (TEAEs). The most frequent TEAES [≥2pts] were fatigue 7 pts (39%) all G1/2, diarrhea 3 pts (17%) all G1/2. Two pts reported DLTs deemed related to study drug, a pt with G2 nausea (single pt cohort, 0.01 mg/kg) and a pt with G3 atrial fibrillation (1 mg/kg). Serious adverse events were reported in 2 pts, 1 pt with atrial fibrillation (deemed by the investigator as possibly related to COM902) and 1 pt with spinal cord compression (deemed by the investigator as unrelated to COM902, related to disease). Preliminary PK profiles were generally dose proportional and peripheral RO above 90% was reported from 0.1 mg/kg dose.

Conclusions

COM902 has an acceptable safety, tolerability and PK profiles. A COM902 3 mg/kg IV Q3 wks is the RDFE. Enrollment into combination cohort (COM902 + COM701), for evaluation of safety/tolerability at the RDFE of both study drugs, combination dose expansion (COM902 + COM701) in pts with HNSCC, NSCLC and CRC-MSS and COM902 monotherapy dose expansion (pts with multiple myeloma) all at the RDFE of study drug(s) are planned. Data cut June 28, 2021.

Trial Registration

NCT04354246

Ethics Approval

The study obtained approval from IRBs of the participating clinical trial sites. The study participants gave informed consent before taking part.o 0002: MOD01006350 (START)o 0003: 20202320 (West Cancer Center)o 0012: 2020–0195 (MDACC)o 0013: MOD01006350 (START midwest)o 0014: 20202320 (OSU)

472 BDB001, a toll-like receptor 7 and 8 (TLR7/8) agonist, can be safely administered intravenously in combination with atezolizumab and shows clinical responses in advanced solid tumors

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 trial. Here, we report on the safety and efficacy of BDB001 in combination with atezolizumab in a Phase I dose escalation/expansion trial in advanced solid tumors (NCT04196530).

Methods

BDB001-102 is a Phase 1, open label, dose escalation/expansion trial of BDB001 (IV, Q1W) in combination with an anti-PD-L1 antibody, atezolizumab (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

Forty-one subjects with 17 different tumor types were enrolled across 4 dose levels. Fifty-nine percent were female, median age was 67 years (range, 32–80), median number of prior therapies was 3 (range, 0–8), and 63% of tumors had progressed on prior anti-PD-(L)1 therapy. Overall, BDB001 in combination with atezolizumab was well tolerated and 13 (31.7%) subjects did not experience any treatment related adverse events (TRAEs). No dose-limiting toxicities were observed. Common TRAEs were transient Grade 1 or 2 fatigue (31.7%), fever (26.8%) and chills/rigor (26.8%). Only 3 (7.3%) subjects experienced Grade 3 TRAEs of fatigue and nausea. There were no Grade 4 or 5 TRAEs and no new safety concerns. Pharmacodynamic evaluation of plasma cytokine levels showed robust increases in interferon gamma and interferon inducible protein-10 (IP-10) at BDB001 Dose Level 4. IP-10 induction was associated with clinical responses. Preliminary efficacy evaluation of the 19 subjects at Dose Level 4 showed durable and deep clinical responses in 3 (16%) subjects, 2 with urothelial carcinoma and 1 with anti-PD-1 mAb refractory NSCLC. All responders remain on treatment, with a duration of response ranging from 7.1+ to 34.1+ weeks. Ten (53%) subjects had stable disease (DCR 68%), 3 of whom had a reduction in tumor burden and were on treatment for over 18 weeks (up to 56 weeks).

Conclusions

Intravenous BDB001 in combination with atezolizumab is well tolerated. Deep and durable clinical responses were observed in PD-1 refractory and naive patients, supported by robust systemic immune activation. BDB001 in combination with atezolizumab is a promising therapeutic option for patients with advanced solid tumors. A phase 2 trial (NCT03915678) of BDB001 in combination with atezolizumab and radiotherapy is currently enrolling patients.

Ethics Approval

This study was approved by the institutional review boards at the five participating institutions. All subjects signed informed consent before enrolling in the clinical trial.

Abstract CT108: A first-in-human, Phase 1 study of ASTX029, a dual-mechanism inhibitor of ERK1/2, in relapsed/refractory solid tumors

Background: The RAS-RAF-MEK-ERK pathway is commonly upregulated in human cancers. This is an open-label Phase 1 study of ASTX029, a dual-mechanism extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, in subjects with relapsed/refractory solid tumors (NCT03520075). Methods: The primary objectives are to identify a maximum tolerated dose and/or recommended Phase 2 dose. ASTX029 was administered orally daily of 21-day cycles as powder-in-bottle (PiB, Cohort 1/10mg) and tablet formulation (beginning with Cohort 6/80 mg) under fed conditions, and as tablet formulation under fasting conditions (beginning with Cohort 8/40 mg). Dose escalation occurred according to a “3+3 design” based on dose-limiting toxicity (DLT) events. Disease response was evaluated according to RECIST v1.1 and exploratory indicators, including tumor variant allele frequency changes detected by cell-free DNA (cfDNA) quantitation. Results: 56 subjects were treated with at least one dose of ASTX029 in Phase 1A (dose escalation). Of 46 subjects with data, 35 (76%) had any RAS mutations and 4 (9%) had BRAF mutations; 1 subject had both. At the 200 mg dose level (Cohort 5, PiB/fed), one of six evaluable subjects developed a DLT (grade 3 maculopapular rash). At the 280 mg dose level (Cohort 12, tablet/fasting), two subjects experienced grade 2 central serous retinopathy adverse events (CSR AEs) within a few days of dosing. These were the only CSR AEs noted and one event was declared a DLT. Both subjects recovered to baseline within days of dose interruption. One cohort level below this dose was expanded (Cohort 11/200 mg, tablet/fasting); this dose level was deemed safe (without a DLT or grade ≥2 visual AE in 7 subjects) and was selected for Phase 1B dose expansion. Mean pharmacokinetic (PK) exposure was 151% of target exposure, which is defined as the level expected to have biological activity based on animal studies. The most frequent grade ≥2 AEs assessed as drug-related included nausea (4 subjects, grade 2) and transaminitis (4 subjects: 3 grade 2, 1 grade 3). The grade 3 transaminitis occurred in a subject with metastatic sarcoma involving the liver. There was one serious AE of malaise considered related to study drug. Two subjects, one with KRAS-G12A and BRAF-D549N non-small cell lung cancer (120 mg) and one with KRAS-G12D metastatic pancreatic cancer (200 mg), achieved partial responses (cycle 15/ongoing and cycle 3/ongoing, respectively). In 2 subjects with stable disease as the best response, longitudinal cfDNA sequencing showed a decrease of tumor variant allele frequencies after 2 cycles of ASTX029, followed by a return to baseline levels before disease progression. The most common reason for ASTX029 discontinuation was disease progression. Conclusions: This Phase 1A study of the ERK1/2 inhibitor ASTX029 has identified a dose level of 200 mg daily of a 21-day cycle for investigation in the Phase 1B portion of the study. Pharmacokinetic and pharmacodynamic data suggest target exposures are achieved with preliminary clinical activity.

Citation Format: Patricia LoRusso, Drew Rasco, Geoffrey Shapiro, Filip Janku, Alain Mita, Nilofer Azad, Marcia Toguchi, Chris Hindley, Shannon Bradley, Danna Chan, Harold Keer, Kim-Hien Dao, Ryan J. Sullivan, Alexander Spira. A first-in-human, Phase 1 study of ASTX029, a dual-mechanism inhibitor of ERK1/2, in relapsed/refractory solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT108.

Lenvatinib plus pembrolizumab in patients with either treatment-naive or previously treated metastatic renal cell carcinoma (Study 111/KEYNOTE-146): a phase 1b/2 study

BACKGROUND

Despite advances in the first-line treatment of metastatic renal cell carcinoma (RCC), there is an unmet need for options to address disease progression during or after treatment with immune checkpoint inhibitors (ICIs). Pembrolizumab and lenvatinib are active as monotherapies in RCC; thus, we aimed to evaluate the combination of lenvatinib plus pembrolizumab in these patients.

METHODS

We report results of the metastatic RCC cohort from an open-label phase 1b/2 study of lenvatinib plus pembrolizumab in patients aged at least 18 years with selected solid tumours and an Eastern Cooperative Oncology Group performance status of 0-1. Oral lenvatinib at 20 mg was given once daily along with intravenous pembrolizumab at 200 mg once every 3 weeks. Patients remained on study drug treatment until disease progression, development of unacceptable toxicity, or withdrawal of consent. Efficacy was analysed in patients with clear cell metastatic RCC receiving study drug by previous therapy grouping: treatment naive, previously treated ICI naive (previously treated with at least one line of therapy but not with an anti-PD-1 or anti-PD-L1 ICI), and ICI pretreated (ie, anti-PD-1 or anti-PD-L1) patients. Safety was analysed in all enrolled and treated patients. The primary endpoint was the objective response rate at week 24 per immune-related Response Evaluation Criteria In Solid Tumors (irRECIST) by investigator assessment. This trial is registered with ClinicalTrials.gov (NCT02501096) and with the EU Clinical Trials Register (EudraCT2017-000300-26), and is closed to new participants.

FINDINGS

Between July 21, 2015, and Oct 16, 2019, 145 patients were enrolled in the study. Two patients had non-clear cell RCC and were excluded from the efficacy analysis (one in the treatment-naive group and one in the ICI-pretreated group); thus, the population evaluated for efficacy comprised 143 patients (n=22 in the treatment-naive group, n=17 in the previously treated ICI-naive group, and n=104 in the ICI-pretreated group). All 145 enrolled patients were included in the safety analysis. The median follow-up was 19·8 months (IQR 14·3-28·4). The number of patients with an objective response at week 24 by irRECIST was 16 (72·7%, 95% CI 49·8-89·3) of 22 treatment-naive patients, seven (41·2%, 18·4-67·1) of 17 previously treated ICI-naive patients, and 58 (55·8%, 45·7-65·5) of 104 ICI-pretreated patients. Of 145 patients, 82 (57%) had grade 3 treatment-related adverse events and ten (7%) had grade 4 treatment-related adverse events. The most common grade 3 treatment-related adverse event was hypertension (30 [21%] of 145 patients). Treatment-related serious adverse events occurred in 36 (25%) patients, and there were three treatment-related deaths (upper gastrointestinal haemorrhage, sudden death, and pneumonia).

INTERPRETATION

Lenvatinib plus pembrolizumab showed encouraging antitumour activity and a manageable safety profile and might be an option for post-ICI treatment of metastatic RCC.

FUNDING

Eisai and Merck Sharp & Dohme.

Abstract OT-03-02: Phase 1/2 study of a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), BDC-1001, as a single agent and in combination with an immune checkpoint inhibitor in patients with advanced HER2-expressing solid tumors

Background: To date, no immune-based therapies beyond anti-HER2 monoclonal antibodies are approved for treating patients (pts) with HER2-driven or -expressing cancers. However, pts still develop progressive disease, and new treatment options that could achieve durable antitumor efficacy are needed. Recent studies indicate that intratumoral delivery of immunostimulatory adjuvants such as toll-like receptor (TLR) 7/8 agonists can activate tumor resident antigen-presenting cells (APCs), driving uptake, processing, and presentation of tumor neoantigens to T cells that mediate antitumor immunity. To overcome limitations associated with intratumoral delivery while leveraging superior preclinical biology, BDC-1001, a novel, systemically delivered ISAC was developed. BDC-1001 consists of an investigational biosimilar of the humanized monoclonal antibody trastuzumab that is chemically conjugated to a TLR 7/8 agonist (payload) with an intervening non-cleavable linker. BDC-1001 activates human myeloid APCs while retaining antibody-mediated effector functions such as antibody-dependent cellular cytotoxicity/phagocytosis (ADCC/ADCP). Xenograft and syngeneic tumor resistant models indicate that trastuzumab ISACs elicit potent and durable immune-mediated antitumor efficacy including complete tumor regression in a TLR- and Fc receptor-dependent manner (Ackerman et al. Cancer Res. 2019:79 [13 Suppl]; Ackerman et al. J Immunother Cancer. 2019;7:283). Importantly, BDC-1001 did not induce interstitial lung disease, cytokine release syndrome, or thrombocytopenia in non-human primate studies. A four-part phase 1/2, first-in-human study has been initiated that evaluates BDC-1001 with or without (+/-) an immune checkpoint inhibitor targeting PD-1 in pts with HER2-expressing or HER2-amplified advanced/metastatic solid tumors.

Study Description: This phase 1/2 dose-escalation and dose-expansion study is enrolling up to 390 pts with advanced solid tumors that are HER2-expressing (IHC2+ or 3+ protein irrespective of gene amplification) or HER2-amplified (by in situ hybridization or next-generation sequencing) and ineligible for approved anti-HER2 treatments. The primary objectives of the dose-escalation phase are to define safety and tolerability and to determine the recommended phase 2 dose of BDC-1001 as monotherapy (Part 1) and in combination with an immune checkpoint inhibitor (Part 2). Primary endpoints of Parts 1 and 2 include incidence of 1) adverse events and severe adverse events graded according to NCI CTCAE v5.0; 2) dose-limiting toxicities within a 3+3 design; and 3) potential immune-related toxicities. BDC-1001 is administered IV over 60 min q3w at increasing doses. Once safety data are available for BDC-1001, initiation of the immune checkpoint inhibitor combination is planned. The dose-expansion phase 2 portion of the trial will evaluate preliminary antitumor activity of BDC-1001 alone (Part 3) and in combination with an immune checkpoint inhibitor (Part 4) using RECIST v1.1 and iRECIST. The primary endpoint of this dose-expansion phase is overall response rate, with secondary endpoints of duration of response, disease control rate, and progression-free survival. Exploratory objectives will evaluate pharmacokinetic parameters and pharmacodynamic biomarkers associated with drug exposure. These exploratory studies will help elucidate the mechanism of action and seek to identify biomarkers to improve selection of pts most likely to benefit from treatment with BDC-1001 +/- immune checkpoint inhibitor. This global study is currently recruiting pts. For further information, visit ClinicalTrials.gov (NCT04278144).

Citation Format: Ecaterina Ileana Dumbrava, Manish R. Sharma, Richard D. Carvajal, Daniel Catenacci, Leisha A. Emens, Shirish M. Gadgeel, Glenn J. Hanna, Dejan Juric, Yoon-Koo Kang, Jeeyun Lee, Keun-Wook Lee, Bob T. Li, Kathleen Moore, Mark D. Pegram, Paula R. Pohlmann, Drew Rasco, Alexander Spira, Antoinette R. Tan, Shelley E. Ackerman, Heidi LeBlanc, David Dornan, Marcin Kowanetz, Michael N. Alonso, Edith A. Perez. Phase 1/2 study of a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), BDC-1001, as a single agent and in combination with an immune checkpoint inhibitor in patients with advanced HER2-expressing solid tumors [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-03-02.

The LEAP program: lenvatinib plus pembrolizumab for the treatment of advanced solid tumors

Tumor progression and immune evasion result from multiple oncogenic and immunosuppressive signals within the tumor microenvironment. The combined blockade of VEGF and inhibitory immune checkpoint signaling has been shown to enhance immune activation and tumor destruction in preclinical models. The LEAP clinical trial program is evaluating the safety and efficacy of lenvatinib (a multikinase inhibitor) plus pembrolizumab (a PD-1 inhibitor) across several solid tumor types. Preliminary results from ongoing trials demonstrate robust antitumor activity and durable responses across diverse tumor types with a manageable safety profile. Thus, lenvatinib plus pembrolizumab is anticipated to be an important potential new regimen for several solid cancers that currently have limited therapeutic options.

Clinical trial registration: NCT03884101 , NCT03713593 , NCT03820986 , NCT03776136 , NCT03797326 , NCT03829319 , NCT03829332 , NCT03976375 , NCT04428151 , NCT04199104 , NCT03898180 , NCT04246177 (ClinicalTrials.gov).

Model Informed Dosing Regimen and Phase I Results of the Anti-PD-1 Antibody Budigalimab (ABBV-181)

Budigalimab is a humanized, recombinant, Fc mutated IgG1 monoclonal antibody targeting programmed cell death 1 (PD‐1) receptor, currently in phase I clinical trials. The safety, efficacy, pharmacokinetics (PKs), pharmacodynamics (PDs), and budigalimab dose selection from monotherapy dose escalation and multihistology expansion cohorts were evaluated in patients with previously treated advanced solid tumors who received budigalimab at 1, 3, or 10 mg/kg intravenously every 2 weeks (Q2W) in dose escalation, including Japanese patients that received 3 and 10 mg/kg Q2W. PK modeling and PK/PD assessments informed the dosing regimen in expansion phase using data from body‐weight‐based dosing in the escalation phase, based on which patients in the multihistology expansion cohort received flat doses of 250 mg Q2W or 500 mg every four weeks (Q4W). Immune‐related adverse events (AEs) were reported in 11 of 59 patients (18.6%), of which 1 of 59 (1.7%) was considered grade ≥ 3 and the safety profile of budigalimab was consistent with other PD‐1 targeting agents. No treatment‐related grade 5 AEs were reported. Four responses per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 were reported in the dose escalation cohort and none in the multihistology expansion cohort. PK of budigalimab was approximately dose proportional and sustained > 99% peripheral PD‐1 receptor saturation was observed by 2 hours postdosing, across doses. PK/PD and safety profiles were comparable between Japanese and Western patients, and exposure‐safety analyses did not indicate any trends. Observed PK and PD‐1 receptor saturation were consistent with model predictions for flat doses and less frequent regimens, validating the early application of PK modeling and PK/PD assessments to inform the recommended dose and regimen, following dose escalation.

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 (> 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 > 1 mg/kg. Plasma CSF1 and IL-34 concentrations increased with treatment and remained elevated at all doses > 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 >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 CT031: COM701 demonstrates preliminary antitumor activity as monotherapy and in combination with nivolumab in patients with advanced solid tumors

Introduction: COM701 is a novel first-in-class Immune checkpoint inhibitor (ICI) that binds with high affinity to poliovirus receptor related immunoglobulin domain containing (PVRIG) blocking its interaction with its ligand, PVRL2 and regulating the activity of T/NK cells through the DNAM/TIGIT axis. In preclinical experiments inhibition of PVRIG alone and in combination with anti-PD1 and/or TIGIT leads to tumor growth inhibition and activation of T-cells in the microenvironment generating an antitumor response. Methods: A total of 28 pts (Arm A/B 16/12) with a variety of cancer types were enrolled. Hybrid accelerated (1st 4 dose cohorts in Arm A) and 3+3 study design (cohorts 5-8 in Arm A and all cohorts in Arm B). Patients with performance status ECOG 0-1 and advanced or metastatic solid tumors who failed standard of care tx were eligible. Prior ICIs were permissible. In Arm A pts received COM701 monotherapy 0.01, 0.03, 0.1, 0.3, 1, 3, 10mg/kg (all IV Q 3 weeks (wks)) and 20 mg/kg (IV Q 4 wks). In Arm B, pts received COM701 at 0.3, 1 or 3mg/kg plus nivolumab 360mg IV q3 wks (3 pts/dose cohort) and 3 pts received 10mg/kg plus nivolumab 480mg IV q4 wks. Treatment emergent adverse events (TEAEs) were reported per CTCAE v4.03 and responses per RECIST v1.1. Dose-limiting toxicities (DLTs) were evaluated within a 21-day or 28-day window (for 3- or 4-wks dosing schedule respectively). Data cutoff date was January 23, 2020. Results: The median number of prior anticancer therapies were: Arm A, 7 (range 2-15), Arm B, 5 (range 2-9). No DLTs have been reported in any of the dose cohorts. Tx was well tolerated with no subjects discontinuing tx due to toxicity, the most frequent TEAEs in Arm A were fatigue (46%), nausea (31%) and anxiety (23%) - all G1-2. In Arm B ≥4 pts - anemia, lower extremity edema, rash and fatigue the majority being grade 1-2 (88%). In Arms A+B: partial response (PR) + stable disease (SD) was 57% (16/28). Of note: Arm A (COM701 20mg/kg IV q4 wks): confirmed PR in a pt with primary peritoneal cancer ongoing on tx > 15 weeks. Arm B: unconfirmed PR in a pt with MSS-CRC on COM701 0.3mg/kg plus nivolumab 360mg IV q3 wks, ongoing on tx >34 wks). Overall 11/28 pts remain on study tx including 3 pts who have not reached 1st imaging assessment. Conclusion: COM701 is well tolerated as monotherapy and in combination with nivolumab in a variety of heavily pretreated pts with advanced or metastatic solid tumors. COM701 demonstrates encouraging preliminary antitumor activity with objective responses as monotherapy and in combination with nivolumab in hard to treat tumor types (primary peritoneal and MSS-CRC).

Citation Format: Ryan Sullivan, Drew Rasco, Emerson Lim, Manish Sharma, Dale Shepard, Amita Patnaik, Erika Hamilton, Gini Fleming, Kyri Papadopoulos, Adam ElNaggar, Adeboye Henry Adewoye, Bartosz Chmielowski, Ecaterina Dumbrava, Dan Vaena. COM701 demonstrates preliminary antitumor activity as monotherapy and in combination with nivolumab in patients with advanced 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 CT031.

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 > 1mg/kg. Treatment led to elevations of plasma concentrations of CSF1R ligands, CSF1 and IL-34, which remained above pre-dose levels at doses > 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.

Phase I Escalation and Expansion Study of Bemarituzumab (FPA144) in Patients With Advanced Solid Tumors and FGFR2b-Selected Gastroesophageal Adenocarcinoma

PURPOSE

To evaluate the safety, pharmacokinetics, and preliminary activity of bemarituzumab in patients with FGFR2b-overexpressing gastric and gastroesophageal junction adenocarcinoma (GEA).

PATIENTS AND METHODS

FPA144-001 was a phase I, open-label, multicenter trial consisting of the following 3 parts: part 1a involved dose escalation in patients with recurrent solid tumors at doses ranging from 0.3 to 15 mg/kg; part 1b involved dose escalation in patients with advanced-stage GEA; and part 2 involved dose expansion in patients with advanced-stage GEA that overexpressed FGFR2b at various levels (4 cohorts; high, medium, low, and no FGFR2b overexpression) and 1 cohort of patients with FGFR2b-overexpressing advanced-stage bladder cancer.

RESULTS

Seventy-nine patients were enrolled; 19 were enrolled in part 1a, 8 in part 1b, and 52 in part 2. No dose-limiting toxicities were reported, and the recommended dose was identified as 15 mg/kg every 2 weeks based on safety, tolerability, pharmacokinetic parameters, and clinical activity. The most frequent treatment-related adverse events (TRAEs) were fatigue (17.7%), nausea (11.4%), and dry eye (10.1%). Grade 3 TRAEs included nausea (2 patients) and anemia, neutropenia, increased AST, increased alkaline phosphatase, vomiting, and an infusion reaction (1 patient each). Three (10.7%) of 28 patients assigned to a cohort receiving a dose of ≥ 10 mg/kg every 2 weeks for ≥ 70 days reported reversible grade 2 corneal TRAEs. No TRAEs of grade ≥ 4 were reported. Five (17.9%; 95% CI, 6.1% to 36.9%) of 28 patients with high FGFR2b-overexpressing GEA had a confirmed partial response.

CONCLUSION

Overall, bemarituzumab seems to be well tolerated and demonstrated single-agent activity as late-line therapy in patients with advanced-stage GEA. Bemarituzumab is currently being evaluated in combination with chemotherapy in a phase III trial as front-line therapy for patients with high FGFR2b-overexpressing advanced-stage GEA.

Abstract P1-03-10: Establishment and characterization of paired palbociclib-sensitive and resistant luminal A breast PDX models

Background: Palbociclib is one of three CDK 4/6 inhibitors approved in combination with an aromatase inhibitor for treatment of hormone receptor-positive breast cancer. Although this combination therapy has been found effective in some patients, resistance often develops. To aid in developing new therapies for CDK4/6-resistant breast cancer and better understand resistance mechanisms, we established a PDX model, designated ST1799, from a patient with luminal A breast cancer which was responsive to palbociclib in vivo and then conditioned the model with chronic drug administration until resistant. The resistant model, designated ST1799/PBR, and the parent were characterized for receptor expression, genomic alterations and in vivo drug sensitivity. Methods: ST1799 was established from an axillary lymph node FNA taken from a 66-year-old woman pretreated with various chemo and hormone therapies. The resulting model was passaged and a cohort challenged with chronic palbociclib treatment to produce drug resistance. The parent ST1799 and resistant ST1799/PBR were subjected to various comparative analyses including receptor expression, NGS and RNAseq and response to various relevant therapies. Results: Both models retained high ER staining (3+) expression and demonstrated comparable histopathology. DNA-based analysis of the parent model confirmed variants concordant with clinical mutation analysis. Comparison of the parent and resistant clone using RNAseq identified several alterations in variants and expression. In vivo palbociclib reported significant (p<0.0001) activity towards ST1799 (T/C=11%) while ST1799/PBR was resistant towards the therapy (T/C=80%). Tamoxifen or fulvestrant treatment of ST1799 resulted in partial tumor regressions while activity in ST1799/PBR was less pronounced. Activity of abemaciclib or ribociclib was greater in ST1799/PBR compared with palbociclib treatment. Conclusion: We have established and characterized paired palbociclib-sensitive and resistant breast PDX models which can be utilized as valuable tools in better understanding CDK4/6i resistance and in developing new therapies for CDK4/6 inhibitor resistant patients.

Citation Format: Lizette Gamez, Alyssa Moriarty, Tomoyuki Mashimo, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Michael J Wick. Establishment and characterization of paired palbociclib-sensitive and resistant luminal A breast PDX models [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-03-10.

Phase IB/II Trial of Lenvatinib Plus Pembrolizumab in Patients With Advanced Renal Cell Carcinoma, Endometrial Cancer, and Other Selected Advanced Solid Tumors

PURPOSE

Modulation of vascular endothelial growth factor–mediated immune suppression via angiogenesis inhibition may augment the activity of immune checkpoint inhibitors. We report results from the dose-finding and initial phase II expansion of a phase Ib/II study of lenvatinib plus pembrolizumab in patients with selected advanced solid tumors.

METHODS

Eligible patients had metastatic renal cell carcinoma (RCC), endometrial cancer, squamous cell carcinoma of the head and neck (SCCHN), melanoma, non–small-cell lung cancer (NSCLC), or urothelial cancer. The primary objective of phase Ib was to determine the maximum tolerated dose (MTD) for lenvatinib plus pembrolizumab (200 mg intravenously every 3 weeks). In the preplanned phase II cohort expansion, the primary objective was objective response rate at week 24 (ORR_{week 24}) at the recommended phase II dose.

RESULTS

Overall, 137 patients were enrolled during phase Ib (n = 13) and the initial phase II expansion (n = 124). Two dose-limiting toxicities (DLTs; grade 3 arthralgia and grade 3 fatigue) were reported in the initial dose level (lenvatinib 24 mg/d plus pembrolizumab). No DLTs were observed in the subsequent dose–de-escalation cohort, establishing the MTD and recommended phase II dose at lenvatinib 20 mg/d plus pembrolizumab. ORR_week24 was as follows: RCC, 63% (19/30; 95% CI, 43.9% to 80.1%); endometrial cancer, 52% (12/23; 95% CI, 30.6% to 73.2%); melanoma, 48% (10/21; 95% CI, 25.7% to 70.2%); SCCHN, 36% (8/22; 95% CI, 17.2% to 59.3%); NSCLC, 33% (7/21; 95% CI, 14.6% to 57.0%); and urothelial cancer 25% (5/20; 95% CI, 8.7% to 49.1%). The most common treatment-related adverse events were fatigue (58%), diarrhea (52%), hypertension (47%), and hypothyroidism (42%).

CONCLUSION

Lenvatinib plus pembrolizumab demonstrated a manageable safety profile and promising antitumor activity in patients with selected solid tumor types.

Abstract A008: PDX-based screen to evaluate and compare approved CDK4/6 inhibitors in breast cancer and determine palbociclib efficacy in additional tumor types

Background: FDA-approved CDK 4/6 inhibitors (CDK4/6i) including palbociclib, abemaciclib, and ribociclib have demonstrated clinical benefit in treating hormone receptor-positive (HR+) breast cancer. However, whether there is differential sensitivity to each therapy in vivo is unknown. In addition, whether these inhibitors demonstrate activity towards other tumor types is unclear. To better understand potential differences in CDK4/6i activity, we compared activity of each in a panel of 100 HR+/- breast cancer PDX models. To identify additional tumor types sensitive to CDK4/6i, we screened single agent palbociclib in an additional panel of 350 PDX models representing solid and hematologic malignancies. FFPE samples were collected from control and treatment groups in all studies at endpoint, and %T/C values in each model were calculated and in breast studies compared. Methods: START PDX models were established and validated as previously described and further characterized using IHC, WES, RNAseq, and drug sensitivity studies. For each CDK4/6i study, models were implanted SC in immune-deficient mice and studies initiated at 200-300 mm3 (n=1-3/grp). CDK4/6i agents were administered orally once daily at 50-75 mg/kg for a minimum of twenty-eight days or until study completion. Models tested with palbociclib included breast, lung, ovary, pancreas, head/neck, renal, gastric, uterine, colorectal, melanoma, and various hematologic malignancies. Study endpoints included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20% versus control was considered sensitive. Partial tumor regression (PR) (%PR=1-99%) and complete tumor regression (CR) (%CR=100%) values versus Day 0 tumor volume of treated groups were also reported. Results: HR+/- breast models demonstrated variable sensitivity to the three CDK4/6i with HR+ models established from chemo-naïve patients reporting greatest tumor growth inhibition (TGI). Two of four HR+ ESR1 mutant models reported modest sensitivity to CDK4/6i (ST941Y537S and ST2535D538G), while ST2177Y537S was sensitive and ST2056Y537S refractory to the three therapies. Evaluation of palbociclib in additional indications reported notable TGI versus control in several indications with the following percentage of tested models reporting sensitivity: Lung: 10%, Ovary: 15%, Pancreas: 30%, Head/Neck: 35%, Renal: 45%, Gastric: 60%, Uterine: 20%, Colorectal: 45%, Melanoma: 40% and Hematologic: 15%. In addition, several indications reported tumor regressions including one CR (lung: ST1748) and partial responses in ovary, pancreas, head/neck, renal, colorectal, and melanoma. Conclusion: We evaluated and compared three FDA-approved CDK4/6i therapies in a panel of HR+/- breast PDX models and identified models with differential responses. In addition, we screened single agent palbociclib in a panel of 350 PDX models representing solid and hematologic malignancies and identified several sensitive models in multiple indications, including some with partial or complete tumor regressions.

Citation Format: Lizette Gamez, Tomoyuki Mashimo, Alyssa Moriarty, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Amy Lang, Ronald Drengler, Lon Smith, Michael J Wick. PDX-based screen to evaluate and compare approved CDK4/6 inhibitors in breast cancer and determine palbociclib efficacy in additional tumor types [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 A008. doi:10.1158/1535-7163.TARG-19-A008

Abstract A017: Development and characterization of HER2+ T-DM1-resistant breast PDX models in athymic nude mice

Background: Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate (ADC) approved for treatment of HER2 positive (HER2+), trastuzumab-resistant breast cancers. While this agent is initially effective, resistance often develops. To aid in developing new therapies for HER2+, T-DM1-resistant breast cancer and better understanding resistance mechanisms, we established PDX models designated ST340, ST1339, and ST2167 from three patients with trastuzumab-resistant HER2+ breast cancer and sensitive to T-DM1 treatment in vivo. A cohort of each model was conditioned in vivo with chronic T-DM1 treatment to generate drug resistance. These models, designated ST340/TDR, ST1339/TDR, and ST2167/TDR were subjected to characterization and efficacy studies, and the results compared with parent models. Methods: ST340, ST1339, and ST2167 were established from patients who responded then progressed on trastuzumab and other therapies. The models were passaged, and cohorts were challenged with chronic T-DM1 treatment to produce drug resistance. The parent and resistant models were subjected to various comparative analyses including receptor expression, RNAseq, and response to various relevant therapies. Results: T-DM1-resistant models retained high HER2 expression and demonstrated receptor staining and histopathology comparable to respective parent lines. Comparison of parent and resistant clones using RNAseq identified several alterations in variants and expression. In vivo T-DM1 reported significant activity towards ST340: %T/C=3%, ST1339: %T/C=-40% and ST2167: %T/C=13% versus control, including tumor regressions in ST1339. T-DM1-resistant models reported the following values following treatment: ST340/TDR: %T/C=65%, ST1339/TDR: %T/C=58% and ST2167/TDR: T/C=91%. Conclusion: We have established and characterized three paired T-DM1-sensitive and resistant breast PDX models, which can be utilized as valuable tools in developing new therapies for T-DM1-resistant patients.

Citation Format: Alyssa Moriarty, Lizette Gamez, Tomoyuki Mashimo, Kyriakos Papadopoulos, Amita Patnaik, Drew Rasco, Amy Lang, Ronald Drengler, Michael J Wick. Development and characterization of HER2+ T-DM1-resistant breast PDX models in athymic nude mice [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 A017. doi:10.1158/1535-7163.TARG-19-A017

Abstract CT168: Phase I study of COM701 (a novel checkpoint inhibitor of PVRIG) in patients with advanced solid tumors

Background: A high unmet medical need exists for the treatment of patients who are unresponsive to or relapse following treatment with checkpoint inhibitors. Therefore, novel checkpoint inhibitors that can demonstrate clinical activity in this patient population are urgently needed. COM701 is a novel first-in-class humanized IgG4 monoclonal antibody that binds with high affinity to PVRIG (poliovirus receptor related immunoglobulin domain containing) blocking its interaction with its ligand, PVRL2. Both PVRIG and PVRL2 are part of the DNAM axis. In nonclinical experiments using in vitro and animal models we have demonstrated that inhibition of PVRIG leads to enhanced activation of T and NK cells, and that knockout of PVRIG results in tumor growth inhibition in mouse tumor models. We hypothesize that COM701 will be safe and tolerable and demonstrate antitumor activity in pts with advanced solid tumors.

Methods: NCT03667716 is an ongoing open-label first-in-human phase 1 study in pts with advanced solid tumors. The initial part of this study (Arm A) will evaluate the safety and tolerability of escalating doses of COM701 monotherapy IV Q3 weekly. Dose-limiting toxicities will be assessed within 21 days in cycle 1 of administration of COM701. Key Inclusion Criteria: Age ≥18 yrs, histologically or cytologically confirmed, locally advanced or metastatic solid malignancy and has exhausted all the available standard therapy or is not a candidate for the available standard therapy, ECOG performance status 0-1, prior anti-PD-1, anti-PD-L1, anti-CTLA-4, OX-40, CD137. Key Exclusion Criteria: Active autoimmune disease requiring systemic therapy in the last 2 years prior to the first dose of COM701, symptomatic interstitial lung disease or inflammatory pneumonitis, untreated or symptomatic central nervous system metastases. Primary outcome measures are the incidence of adverse events and dose-limiting toxicities (21-day DLT window), pharmacokinetics of COM701 and to identify the maximum tolerated dose and/or the recommended dose for expansion. Secondary outcome measures are to characterize the immunogenicity and preliminary antitumor activity of COM701. Study Design: Single subject dose cohorts in initial 4 dose cohorts and 3+3 study design for subsequent cohorts.

Statistical Considerations: Adverse events graded as per CTCAE v4.03, responses as per RECIST v1.1. The analyses of all study objectives will be descriptive and hypothesis generating. As of the date of this submission no DLTs have been reported in the initial 4 dose cohorts. Enrollment in cohort 5 is ongoing.

Citation Format: Dan Vaena, Amita Patnaik, Erika Hamilton, Judy Olweny, John Hunter, Adeboye Henry Adewoye, Adam ElNaggar, Drew Rasco. Phase I study of COM701 (a novel checkpoint inhibitor of PVRIG) in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT168.

A Phase 1b/2 Study of the Bruton Tyrosine Kinase Inhibitor Ibrutinib and the PD-L1 Inhibitor Durvalumab in Patients with Pretreated Solid Tumors

BACKGROUND

Ibrutinib, a first-in-class, once-daily inhibitor of Bruton's tyrosine kinase, is approved in the United States for the treatment of various B-cell malignancies. Preclinical data suggest synergistic antitumor activity of ibrutinib with programmed death-ligand 1 (PD-L1) inhibitors in solid tumors. This study evaluated ibrutinib plus durvalumab, a PD-L1-targeting antibody, in patients with relapsed/refractory solid tumors.

METHODS

This open-label, multicenter, phase 1b/2 study enrolled previously treated patients with stage III/IV pancreatic adenocarcinoma, breast cancer, or non-small cell lung cancer (NSCLC). Phase 1b determined the recommended phase 2 dose (RP2D). In phase 2, patients were treated at the RP2D to evaluate the safety and antitumor activity of ibrutinib plus durvalumab.

RESULTS

The RP2D was identified as ibrutinib 560 mg p.o. daily and durvalumab 10 mg/kg i.v. every 2 weeks, with 122 patients treated at the RP2D. Median age was 61 years, and the majority of patients (94%) had stage IV disease. Overall response rates (complete or partial responses) were 2% for pancreatic cancer, 3% for breast cancer, and 0% for NSCLC. Median progression-free survival was 1.7, 1.7, and 2.0 months in the pancreatic cancer, breast cancer, and NSCLC cohorts, respectively. Median overall survival was 4.2, 4.2, and 7.9 months in the pancreatic cancer, breast cancer, and NSCLC cohorts, respectively. The safety profiles observed across tumor types were consistent with the known safety profiles for ibrutinib and durvalumab. Grade ≥3 adverse events in ≥5% of all patients were hyponatremia (10%), dyspnea (7%), maculopapular rash (7%), pneumonia (7%), anemia (6%), and diarrhea (6%).

CONCLUSIONS

The combination of ibrutinib 560 mg daily and durvalumab 10 mg/kg every 2 weeks had an acceptable safety profile. The antitumor activity of the ibrutinib-durvalumab combination was limited in our study population.

Lenvatinib plus pembrolizumab in patients with advanced endometrial cancer: an interim analysis of a multicentre, open-label, single-arm, phase 2 trial

BACKGROUND

Lenvatinib is a multikinase inhibitor of VEGFR1, VEGFR2, and VEGFR3, and other receptor tyrosine kinases. Pembrolizumab, an antibody targeting PD-1, has moderate efficacy in biomarker-unselected endometrial cancer. We aimed to assess the combination of lenvatinib plus pembrolizumab in patients with advanced endometrial carcinoma, after establishing the maximum tolerated dose in a phase 1b study.

METHODS

In this open-label, single-arm, phase 2 study done at 11 centres in the USA, eligible patients were aged 18 years or older and had metastatic endometrial cancer (unselected for microsatellite instability or PD-L1), had an Eastern Cooperative Oncology Group performance status of 0 or 1, had received no more than two previous systemic therapies, had measurable disease according to the immune-related Response Evaluation Criteria In Solid Tumors (irRECIST), and had a life expectancy of 12 weeks or longer. Patients received 20 mg oral lenvatinib daily plus 200 mg intravenous pembrolizumab every 3 weeks. Treatment continued until disease progression, development of unacceptable toxic effects, or withdrawal of consent. The primary endpoint of this interim analysis was the proportion of patients with an objective response at week 24 as assessed by investigators according to irRECIST in the per-protocol population. This trial is registered with ClinicalTrials.gov, number NCT02501096.

FINDINGS

Between Sept 10, 2015, and July 24, 2017, 54 patients were enrolled, 53 of whom were included in the analysis. At the cutoff date for anti-tumour activity data (Dec 15, 2017), median study follow-up was 13·3 months (IQR 6·7-20·1). 21 (39·6% [95% CI 26·5-54·0]) patients had an objective response at week 24. Serious treatment-related adverse events occurred in 16 (30%) patients, and one treatment-related death was reported (intracranial haemorrhage). The most frequently reported any-grade treatment-related adverse events were hypertension (31 [58%]), fatigue (29 [55%]), diarrhoea (27 [51%]), and hypothyroidism (25 [47%]). The most common grade 3 treatment-related adverse events were hypertension (18 [34%]) and diarrhoea (four [8%]). No grade 4 treatment-related adverse events were reported. Five (9%) patients discontinued study treatment because of treatment-related adverse events.

INTERPRETATION

Lenvatinib plus pembrolizumab showed anti-tumour activity in patients with advanced recurrent endometrial cancer with a safety profile that was similar to those previously reported for lenvatinib and pembrolizumab monotherapies, apart from an increased frequency of hypothyroidism. Lenvatinib plus pembrolizumab could represent a new potential treatment option for this patient population, and is being investigated in a randomised phase 3 study.

FUNDING

Eisai and Merck.

First-in-Human, First-in-Class Phase I Trial of the Anti-CD47 Antibody Hu5F9-G4 in Patients With Advanced Cancers

PURPOSE

To evaluate the safety, pharmacokinetics, and pharmacodynamics of Hu5F9-G4 (5F9), a humanized IgG4 antibody that targets CD47 to enable phagocytosis.

PATIENTS AND METHODS

Adult patients with solid tumors were treated in four cohorts: part A, to determine a priming dose; part B, to determine a weekly maintenance dose; part C, to study a loading dose in week 2; and a tumor biopsy cohort.

RESULTS

Sixty-two patients were treated: 11 in part A, 14 in B, 22 in C, and 15 in the biopsy cohort. Part A used doses that ranged from 0.1 to 3 mg/kg. On the basis of tolerability and receptor occupancy studies that showed 100% CD47 saturation on RBCs, 1 mg/kg was selected as the priming dose. In subsequent groups, patients were treated with maintenance doses that ranged from 3 to 45 mg/kg, and most toxicities were mild to moderate. These included transient anemia (57% of patients), hemagglutination on peripheral blood smear (36%), fatigue (64%), headaches (50%), fever (45%), chills (45%), hyperbilirubinemia (34%), lymphopenia (34%), infusion-related reactions (34%), and arthralgias (18%). No maximum tolerated dose was reached with maintenance doses up to 45 mg/kg. At doses of 10 mg/kg or more, the CD47 antigen sink was saturated by 5F9, and a 5F9 half-life of approximately 13 days was observed. Strong antibody staining of tumor tissue was observed in a patient at 30 mg/kg. Two patients with ovarian/fallopian tube cancers had partial remissions for 5.2 and 9.2 months.

CONCLUSION

5F9 is well tolerated using a priming dose at 1 mg/kg on day 1 followed by maintenance doses of up to 45 mg/kg weekly.