Longitudinal SARS-CoV-2 mRNA Vaccine-Induced Humoral Immune Responses in Patients with Cancer

Longitudinal studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine-induced immune responses in patients with cancer are needed to optimize clinical care. In a prospective cohort study of 366 (291 vaccinated) patients, we measured antibody levels [anti-spike (IgG-(S-RBD) and anti-nucleocapsid immunoglobulin] at three time points. Antibody level trajectories and frequency of breakthrough infections were evaluated by tumor type and timing of treatment relative to vaccination. IgG-(S-RBD) at peak response (median = 42 days after dose 2) was higher (P = 0.002) and remained higher after 4 to 6 months (P = 0.003) in patients receiving mRNA-1273 compared with BNT162b2. Patients with solid tumors attained higher peak levels (P = 0.001) and sustained levels after 4 to 6 months (P < 0.001) compared with those with hematologic malignancies. B-cell targeted treatment reduced peak (P = 0.001) and sustained antibody responses (P = 0.003). Solid tumor patients receiving immune checkpoint inhibitors before vaccination had lower sustained antibody levels than those who received treatment after vaccination (P = 0.043). Two (0.69%) vaccinated and one (1.9%) unvaccinated patient had severe COVID-19 illness during follow-up. Our study shows variation in sustained antibody responses across cancer populations receiving various therapeutic modalities, with important implications for vaccine booster timing and patient selection. SIGNIFICANCE: Long-term studies of immunogenicity of SARS-CoV-2 vaccines in patients with cancer are needed to inform evidence-based guidelines for booster vaccinations and to tailor sequence and timing of vaccinations to elicit improved humoral responses.

Immunotherapy of cancer in the era of checkpoint inhibitor

Application of immunotherapy has revolutionized treatment of number of malignancies. We present a review of immunotherapy approaches, early-phase data of number of new immunotherapeutic targets in melanoma, cutaneous squamous cell carcinoma, Merkel cell cancer, and non-small cell lung cancer.

Abstract P239: Safety and efficacy of copanlisib in combination with nivolumab: A phase Ib study in patients with advanced solid tumors

Introduction: Copanlisib (C) is a pan-class I PI3K inhibitor, with predominant activity against the PI3K-α and -δ isoforms, approved for patients (pts) with relapsed follicular lymphoma. The PD-1 inhibitor nivolumab (N) is approved for several advanced or metastatic solid tumors. Following preclinical demonstration of the immunomodulatory activity of C (Glaeske et al. AACR 2018), we report Phase Ib results evaluating the safety and efficacy of C+N in pts with advanced solid tumors (NCT03735628). Methods: PD-1 inhibitor-naive adult pts with advanced solid tumors received C 45 mg or 60 mg i.v. (days 1, 8, and 15; 28-day cycle) and N 240 mg (day 15 of cycle 1 and days 1 and 15 of subsequent cycles). The primary objective was determination of the recommended Phase II dose (RP2D) of C in combination with N. Secondary endpoints were safety/tolerability, pharmacokinetics (PK), and efficacy. Exploratory real-time evaluation of 77 pharmacodynamic and predictive immune cell biomarkers by flow cytometry on whole blood was performed. Results: 16 pts were treated (C 45 mg + N 240 mg, n=5; C 60 mg + N 240 mg, n=11). Median age was 65 years (range 37–89), 12 pts (75%) were male, and 8 pts (50%) had stage IV disease at diagnosis; the most common tumor types were head and neck squamous cell carcinoma (HNSCC; 7 pts) and bladder cancer (BC; 4 pts). No dose-limiting toxicities were reported. The RP2D of C+N 240 mg was 60 mg. As of 13 May 2020, 4 pts remain on treatment. The most common treatment-emergent adverse events (TEAEs) of any grade were hypertension and diarrhea (7 pts [44%] each, ≤ grade [G] 3) and maculo-papular rash and fatigue (6 pts [38%] each, ≤G3). C-related TEAEs were reported in 88% of pts, all ≤G3. AEs leading to C dose interruption/reduction were reported in 31%/19% of pts; TEAEs led to C discontinuation in 1 pt (60 mg; hematuria). Serious AEs occurred in 5 pts (31%). One G5 TEAE occurred (45 mg; general physical health deterioration, unrelated to C or N). No PK interactions were observed between C and N. Two pts had a partial response: 1 in the C 45 mg group (HNSCC) and 1 in the 60 mg group (BC; benefit sustained after 19 cycles). Stable disease was seen in 10 pts and disease progression in 3 pts; disease control rate (DCR) was 75%. Maximum decrease in circulating monocytic myeloid-derived suppressor cells (M-MDSCs; p&lt;0.05) from baseline occurred on day 2 after C, returning to baseline on day 8. A significant increase in activated (HLA-DR+ and CD38+) natural killer and CD8+ T cells was seen 2 weeks post-treatment with C+N. Lower baseline levels of CD8+ Teffector memory (TEM) subset CD45RA-/CCR7- (CD3+/CD8+) seemed to associate with higher DCR. Conclusions: C+N showed acceptable safety and preliminary efficacy in pts with advanced solid tumors. The immunomodulatory effect of C on M-MDSCs was seen 2 days post-treatment, and lower TEM subset levels seemed to associate with better disease control. These results support further investigation of C+N in pts with advanced solid tumors. Funding: Bayer AG. Writing support: Complete HealthVizion.

Citation Format: Benedito A. Carneiro, Robert Jotte, Nashat Gabrail, Omid Hamid, Funan Huang, Shalini Chaturvedi, Matthias Herpers, Lidia Mongay Soler, Barrett H. Childs, Aaron Hansen. Safety and efficacy of copanlisib in combination with nivolumab: A phase Ib study in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P239.

Long-term outcomes of patients with active melanoma brain metastases treated with combination nivolumab plus ipilimumab (CheckMate 204): final results of an open-label, multicentre, phase 2 study

BACKGROUND

Combination nivolumab plus ipilimumab was efficacious in patients with asymptomatic melanoma brain metastases (MBM) in CheckMate 204, but showed low efficacy in patients with symptomatic MBM. Here, we provide final 3-year follow-up data from the trial.

METHODS

This open-label, multicentre, phase 2 study (CheckMate 204) included adults (aged ≥18 years) with measurable MBM (0·5-3·0 cm in diameter). Asymptomatic patients (cohort A) had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 and no neurological symptoms or baseline corticosteroid use; symptomatic patients (cohort B) had an ECOG performance status of 0-2 with stable neurological symptoms and could be receiving low-dose dexamethasone. Nivolumab 1 mg/kg plus ipilimumab 3 mg/kg was given intravenously every 3 weeks for four doses, followed by nivolumab 3 mg/kg every 2 weeks for up to 2 years, until disease progression or unacceptable toxicity. The primary endpoint was intracranial clinical benefit rate (complete responses, partial responses, or stable disease lasting ≥6 months) assessed in all treated patients. Intracranial progression-free survival and overall survival were key secondary endpoints. This study is registered with ClinicalTrials.gov, NCT02320058.

FINDINGS

Between Feb 19, 2015, and Nov 1, 2017, 119 (72%) of 165 screened patients were enrolled and treated: 101 patients were asymptomatic (cohort A; median follow-up 34·3 months [IQR 14·7-36·4]) and 18 were symptomatic (cohort B; median follow-up 7·5 months [1·2-35·2]). Investigator-assessed intracranial clinical benefit was observed in 58 (57·4% [95% CI 47·2-67·2]) of 101 patients in cohort A and three (16·7% [3·6-41·4]) of 18 patients in cohort B; investigator-assessed objective response was observed in 54 (53·5% [43·3-63·5]) patients in cohort A and three (16·7% [3·6-41·4]) patients in cohort B. 33 (33%) patients in cohort A and three (17%) patients in cohort B had an investigator-assessed intracranial complete response. For patients in cohort A, 36-month intracranial progression-free survival was 54·1% (95% CI 42·7-64·1) and overall survival was 71·9% (61·8-79·8). For patients in cohort B, 36-month intracranial progression-free survival was 18·9% (95% CI 4·6-40·5) and overall survival was 36·6% (14·0-59·8). The most common grade 3-4 treatment-related adverse events (TRAEs) were increased alanine aminotransferase and aspartate aminotransferase (15 [15%] of 101 patients each) in cohort A; no grade 3 TRAEs occurred in more than one patient each in cohort B, and no grade 4 events occurred. The most common serious TRAEs were colitis, diarrhoea, hypophysitis, and increased alanine aminotransferase (five [5%] of each among the 101 patients in cohort A); no serious TRAE occurred in more than one patient each in cohort B. There was one treatment-related death (myocarditis in cohort A).

INTERPRETATION

The durable 3-year response, overall survival, and progression-free survival rates for asymptomatic patients support first-line use of nivolumab plus ipilimumab. Symptomatic disease in patients with MBM remains difficult to treat, but some patients achieve a long-term response with the combination.

FUNDING

Bristol Myers Squibb.

538 Updated survival of patients with previously treated metastatic uveal melanoma who received tebentafusp

Background

Tebentafusp, a bispecific fusion protein consisting of an affinity-enhanced T cell receptor fused to an anti-CD3 effector that can redirect T cells to target gp100+ cells, has shown an overall survival benefit for patients with untreated metastatic uveal melanoma (mUM) in a Ph3 trial (NCT03070392). Metastatic uveal melanoma (mUM) is a historically treatment-refractory tumor with 1-year (yr), 2-yr and 3-yr OS rates of 37%, 15% and 9%, respectively, and median OS of 7.8 months in 2L+ patients.1 In the primary analysis of the phase 2 IMCgp100–102 study (NCT02570308) enrolling patients with previously treated mUM, the 1-year overall survival (OS) rate was 62% with median OS of 16.8 months.2 We present updated OS and safety after 2-year follow-up.

Methods

127 HLA-A*02:01+ 2L+ mUM patients were dosed weekly with tebentafusp following intra-patient dose escalation: 20mcg dose 1, 30mcg dose 2 and 68mcg dose 3+. Primary objective was ORR and secondary objectives included safety, OS and PFS. Here we present the updated OS and safety (data cut-off 31 Mar 2021).

Results

Median follow-up was 29.9 mos (range 1.8 – 59.9 mos). With extended follow-up, the 1-yr, 2-yr and 3-yr OS rates were 61%, 37% and 24%, respectively (figure 1). Median OS remained unchanged at 16.8 mos (95% CI, 12.8 – 22.5 mos).Mean and median duration of treatment were 9.5 mos and 5.6 mos (0 – 47.4 mos), respectively. As previously reported, most treatment-related AEs (TRAEs) occurred early on treatment. Beyond 6 months, no TRAE led to treatment discontinuation. No new safety signals, changes in the type or treatment-related deaths were reported. Beyond 12 months, there were a total of 7 Grade (G) 3 or 4 events in 3 (7%) patients, all were temporally related to tumor progression and majority included lab abnormalities. Episodes of rash, a common tebentafusp-related AE early on-treatment, were infrequent after 6 months, with no Grade 3 or 4 events.

Abstract 538 Figure 1

Kaplan-Meier estimate of overall survival at 2-yr follow-up of IMCgp100-102

Conclusions

This study provides the longest follow-up of OS and safety of a soluble TCR therapeutic to date. Tebentafusp continued to show promising survival for 2L+ mUM patients with estimated 2-yr OS rate of 37%. Tebentafusp’s safety profile was as expected and consistent with primary analysis showing that most adverse events occur early on treatment with incidence and severity decreasing with prolonged exposure.

Trial Registration

NCT02570308

References

Rantala ES, Hernberg M, Kivela TT. Overall survival after treatment for metastatic uveal melanoma: a systematic review and meta-analysis. Melanoma Res 2019;29:561–568.

Sacco JJ, Carvajal R, Butler MO, et al. A phase (ph) II, multi-center study of the safety and efficacy of tebentafusp (tebe) (IMCgp100) in patients (pts) with metastatic uveal melanoma (mUM). Ann Oncol 2020;31: S1442–S1143.

Ethics Approval

The institutional review board or independent ethics committee at each center approved the trial. The trial was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines.

546 Results from Phase Ib study of tebentafusp (tebe) in combination with durvalumab (durva) and/or tremelimumab (treme) in metastatic cutaneous melanoma (mCM)

Background

Tebe, a T cell receptor fused to an anti-CD3 effector, can redirect T cells to target gp100+ cells and in Ph3, demonstrated overall survival (OS) benefit as monotherapy in metastatic uveal melanoma. In Ph2, any tumor shrinkage (44% of patients) was a better predictor of OS than response rate. In Ph1, Tebe had monotherapy activity in mCM, also a gp100+ tumor, with 1-year OS ~74% in PD-1 naïve mCM. A Ph1 dose escalation of tebe with durva (anti-PD-L1) and/or treme (anti-CTLA4) was conducted in pre-treated mCM [NCT02535078], with nearly all patients having prior PD1-treatment, and where recently reported therapies have 1-yr OS of ~55%.

Methods

Heavily pre-treated HLA-A2+ mCM patients received weekly IV tebe alone (Arm 4) or with increasing doses of durva and/or treme (Arm 1–3) administered IV monthly starting day 15 of each cycle. Primary objective was to identify RP2D of combination therapy. Secondary objectives included adverse events (AE) and efficacy.

Results

112 pts received ≥1 tebe dose. Median age was 59, 77% were ECOG 0, and 37% were BRAFm (of which 71% received prior BRAFi/MEKi). 91% of pts were 2L+, while 74% were 3L+. 103 (92%) received prior PD-1 inhibitor, of which 87% also received prior ipilimumab. 43 pts received tebe + durva (Arm 1), 13 received tebe + treme (Arm 2), 29 received triplet therapy (Arm 3), and 27 received tebe alone (Arm 4). Maximum target doses of tebe (68 mcg) + durva (20 mg/kg) and treme (1 mg/kg) were tolerated. MTD was not formally identified for any arm. Two DLTs occurred: prolonged grade 3 rash (Arm 1) and grade 2 diarrhea leading to treatment delay (Arm 2). Related AEs that were Grade ≥3 or led to discontinuations were: 44%/0% (Arm 1), 23%/0% (Arm2), 38%/7% (Arm3), 26%/4% (Arm 4). There were no treatment-related deaths.In prior PD-1 pts, tumor shrinkage occurred in 36% and 1-yr OS was 68%. Of 51 evaluable PD-1 resistant pts (best response CR/PR/SD to prior PD1), tumor shrinkage occurred in 28% and 1-yr OS was 73% (figure 1). In 35 evaluable PD-1 refractory pts (prior best response PD), tumor shrinkage occurred in 49% and 1-yr OS was 61%. For 38 prior PD-1 pts who received ≥10mg/kg durva, 1-yr OS was 81%.

Abstract 546 Figure 1

% tumor change from baseline in evaluable patients with known response to prior PD1 exposure

Conclusions

Tebe with anti-PD-L1 and/or anti-CTLA4 had an acceptable safety profile. Tebe + durva demonstrated durable tumor shrinkage and promising 1-yr OS rates in prior-PD1 treated mCM relative to recent reports.

Trial Registration

NCT02535078

Ethics Approval

The institutional review board or independent ethics committee at each center approved the trial. The trial was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines.

490 Clinical benefit through Siglec-15 targeting with NC318 antibody in subjects with Siglec-15 positive advanced solid tumors

Background

Siglec-15 (S15) is a member of the Siglec family of immunoglobulin superfamily proteins involved in immune regulation. NC318 is a first-in-class humanized IgG1κ monoclonal antibody that blocks S15-mediated immune suppression.

Methods

The Phase 1 dose-escalation study was a classical 3+3 design in 15 tumor types (n=49). Phase 2 (n=47) was conducted at 400 mg q2w in 4 tumor types. Inclusion criteria included subjects with advanced/metastatic solid tumors refractory or resistant to currently available therapies with a TPS PD-L1 score <50%. The median number of previous therapies was ≥3, including checkpoint inhibitors (figure 1).

Results

NC318 was well tolerated with no novel immunologic or safety signals observed. Disease control rate amongst evaluable population (n=83) is 38% {1 CR, 3 PR and 28 SD (stable disease)}. Median duration of disease control is 24 weeks (16–48 weeks) amongst 20 subjects achieving a minimal 16-week duration of stable disease. Two NSCLC subjects (1CR and 1PR) are still on therapy over 2 years. We observed an increase in a soluble form of Siglec-15 (sS15) in all patients receiving NC318 treatment that was dose-dependent. sS15 serves as a pharmacodynamic marker for NC318 activity. PK/PD modeling of NC318 from this Phase1/2 study using sS15 as a PD marker suggested increasing the dose of NC318 to 800 mg q1w to enhance overall exposure of NC318. Development of an S15 specific IHC assay allowed us to do post-hoc analysis by immuno-histochemistry (IHC) from screening biopsies amongst subjects who showed disease control (CR, PR and SD) compared to subjects with progressive disease. S15 expression on tumor cell membrane was a predictor for stable disease, longer duration on therapy when compared to progressive disease {H score ≥ 1 (p=0.046), including NSCLC subjects}, as well as for progression-free survival (PFS) (figures 2 and 3). There was no correlation with the outcome whether PD-L1 was positive or negative. Together, development of a predictive indicator of S15 staining coupled with the NC318 PK/PD data, resulted in a protocol amendment to prospectively enroll subjects with Siglec-15+ adenocarcinoma lung, squamous H&N, and breast cancers at 800 mg q1w. Soluble S15, immunophenotyping, cytokine and chemokine levels and neutrophil-lymphocyte ratio will be presented at the meeting.

Abstract 490 Figure 1

NC318: study schema

Abstract 490 Figure 2

Tumor membrane S15 H score≥1 and progression-free survival. A) All Individuals with available H-Scores>=1 were stratified into two groups (Progressive disease (PD) and Stable disease (SD)) based on the RECIST criteria and their plasma membrane H-scores were compared using Wilcoxon test. Significant differences among H-scores were observed between the groups with a p-value of 0.046; B) Survival analysis was performed by stratifying individuals with H-Scores>=1 into two groups (PD or SD). Statistical analysis was performed by Log-rank (Mantel-Cox) and Hazard Ratio (Mantel-Haenszel) test.

Abstract 490 Figure 3

Tumor membrane S15 H score and PFS (SD vs. PD). A) All Individuals with available H-Scores were stratified into two groups (Progressive disease (PD) and Stable disease (SD)) based on the RECIST criteria and their plasma membrane H-scores were compared using Wilcoxon test. Significant differences among H-scores were observed between the groups with a p-value of 0.046. All individuals with H-score>=1 are above the dashed red horizontal line; B) Survival analysis was performed by stratifying as CR or PR, SD at week 16, SD at week 8 and PD at week 16, SD at week 8 and did not reach week 16, and PD by RECIST criteria. P value is generated by Log-rank (Mantel-Cox) test between groups of SD (all three subsets combined) vs. PD. Analysis indicates differences in median survival rates with better survival attributed to individuals with response in the above specified order

Conclusions

NC318 shows promising early evidence of disease control in subjects with Siglec-15 positive advanced or metastatic solid tumors in phase 1 & 2 studies, prompting evaluation of S15 expression as a predictive biomarker in the prospective study at 800mg q1w dosing.

Trial Registration

NCT03665285

Ethics Approval

This study has been approved by the IRB of all the participating institutions, and all participants have given informed consent before taking part in the study.

Consent

Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

Development and Validation of a Modified Pathologic Nodal Classification System for Cutaneous Melanoma

Importance

Given the evolving patterns of lymph node evaluation for cutaneous melanoma, it is unclear whether the current nodal classification system will continue to accurately reflect prognosis in the modern era. Existing nodal staging for cutaneous melanoma was developed primarily for patients undergoing completion lymph node dissection (CLND) for node-positive disease and does not produce groups with continuously increasing mortality.

Objective

To develop and validate a modified nodal classification system for cutaneous melanoma.

Design, Setting, and Participants

This retrospective cohort analysis included 105 785 patients with cutaneous melanoma undergoing surgery and nodal evaluation from January 1, 2004, to December 31, 2015, in the National Cancer Database. Extent of lymph node dissection was available for patients diagnosed in 2012 and onward. Multivariable models were generated with number of positive lymph nodes modeled using restricted cubic splines. A modified nodal classification system was derived using recursive partitioning analysis (RPA). The proposed lymph node classification system was validated in 85 499 patients from the Surveillance, Epidemiology, and End Results (SEER-18) database. Data were analyzed from April 9, 2020, to May 28, 2021.

Main Outcomes and Measures

Overall survival.

Results

Among the 105 785 patients included in the analysis (62 496 men [59.1%]; mean [SD] age, 59.9 [15.5] years), number of positive lymph nodes (hazard ratio [HR] per lymph node for 0 to 2 positive lymph nodes, 2.48 [95% CI, 2.37-2-61; P < .001]; HR per lymph node for ≥3 positive lymph nodes, 1.10 [95% CI 1.07-1.13; P < .001]), clinically detected metastases (HR, 1.35; 95% CI, 1.27-1.42; P < .001), and in-transit metastases (HR, 1.48; 95% CI, 1.34-1.65; P < .001) were independently associated with mortality. An RPA-derived system using these variables demonstrated continuously increasing mortality for each proposed lymph node classification group, with HRs of 1.83 (95% CI, 1.76-1.91) for N1a, 2.72 (95% CI, 2.58-2.86) for N1b, 3.79 (95% CI, 3.51-4.08) for N2a, 4.56 (95% CI, 4.22-4.92) for N2b, 6.15 (95% CI, 5.59-6.76) for N3a, and 8.25 (95% CI, 7.64-8.91) for N3b in the proposed system (P < .001). By contrast, the current American Joint Committee on Cancer (AJCC) nodal classification system produced a more haphazard mortality profile, with HRs of 1.83 (95% CI, 1.76-1.91) for N1a, 3.81 (95% CI, 3.53-4.12) for N1b, 2.59 (95% CI, 2.30-2.93) for N1c, 2.71 (95% CI, 2.56-2.87) for N2a, 4.51 (95% CI, 4.17-4.87) for N2b, 3.44 (95% CI, 2.60-4.55) for N2c, 6.06 (95% CI, 5.51-6.67) for N3a, 8.15 (95% CI, 7.54-8.81) for N3b, and 6.90 (95% CI, 5.60-8.49) for N3c. As a sensitivity analysis, the proposed system continued to accurately stratify patients when excluding those undergoing CLND for microscopic lymph node metastases. This system was validated for overall survival and cause-specific mortality in SEER-18. Last, a new overall staging system for node-positive patients was developed by RPA and demonstrated improved concordance vs the AJCC, 8th edition system (C statistic, 0.690 [95% CI, 0.689-0.691] vs 0.666 [95% CI, 0.666-0.668]).

Conclusions and Relevance

The findings of this cohort study suggest that a modified nodal classification system can accurately stratify mortality risk in cutaneous melanoma in an era of increasing use of sentinel lymph node biopsy without CLND and should be considered for future staging systems.

488 Phase 1 trial of first-in-class anti-CD96 monoclonal antibody inhibitor, GSK6097608, monotherapy and combination with anti–PD-1 monoclonal antibody, dostarlimab, in advanced solid tumors

Background

The CD226 axis plays an important role in natural killer (NK)- and T-cell biology and cancer immune surveillance.1–4 CD226 is an immune costimulatory molecule expressed on T and NK cells, which binds to its ligands, CD155 and CD112, on tumors and antigen-presenting cells to stimulate an immune response. The immune checkpoints TIGIT, CD96, and PVRIG compete with CD226 binding to CD155 and CD112 to suppress immune activation. Combinations of agents that target these checkpoints and PD(L)1 could augment CD226-mediated antitumor activity. Inhibition or deletion of CD96 resulted in antitumor activity in syngeneic mouse tumor models alone and in combination with PD-1 inhibition.5 6 GSK6097608 is a monoclonal antibody that blocks CD96, enhancing CD155-CD226 NK/T-cell activation.7 Based on these results, GSK6097608 is being explored alone and in combination with the anti–PD-1 monoclonal antibody, dostarlimab, in a phase 1, dose-escalation trial.8

Methods

Adults (≥18 years of age) with histological or cytological documentation of locally advanced, recurrent, or metastatic solid malignancy that has progressed after standard therapy for the specific tumor type are eligible. Prior anti–PD-1 therapy is allowed. Other key inclusion criteria include Eastern Cooperative Oncology Group performance status 0–1, adequate organ function, and life expectancy of ≥12 weeks. Patients with prior bone marrow or solid organ transplant, uncontrolled central nervous system metastases, or active autoimmune disease are ineligible. In this open label, nonrandomized, sequential assignment trial (N≈100; NCT04446351), patients will receive intravenous infusion GSK6097608 every 3 weeks as monotherapy alone or in combination with intravenous dostarlimab (every 3 weeks for 4 doses and every 6 weeks thereafter). Based on the safety, pharmacokinetics, and pharmacodynamics of monotherapy, the combination arm will be opened. The primary endpoints are dose-limiting toxicities and adverse events. Secondary endpoints include abnormal laboratory values, cardiac parameters, and vital signs; dose reduction, dose delay, or withdrawal due to adverse events; overall response rate per Response Evaluation Criteria in Solid Tumors version 1.1; and antidrug antibodies against and pharmacokinetic parameters of GSK6097608 and dostarlimab. The trial is actively recruiting patients.

Acknowledgements

The authors thank the participating patients, families, investigators, site staff, and colleagues at GlaxoSmithKline (GSK) and 23andMe. Funding for the study was provided by GSK (study 212214). Writing and editorial support, funded by GSK (Waltham, MA, USA) and coordinated by Hasan H. Jamal, of GSK, was provided by MediTech Media.

Trial Registration www.ClinicalTrials.gov, NCT04446351

References

Georgiev H, Ravens I, Papadogianni G, Bernhardt G. Coming of age: CD96 emerges as modulator of immune responses. Front Immunol 2018;9:1072.

Torphy RJ, Schulick RD, Zhu Y. Newly emerging immune checkpoints: promises for future cancer therapy. Int J Mol Sci 2017;18:2642.

Sanchez-Correa B, Valhondo I, Hassouneh F, et al. DNAM-1 and the TIGIT/PVRIG/TACTILE axis: novel immune checkpoints for natural killer cell-based cancer immunotherapy. Cancers (Basel) 2019;11:877.

Qin S, Xu L, Yi M, et al. Novel immune checkpoint targets: moving beyond PD-1 and CTLA-4. Mol Cancer 2019;18:155.

Blake SJ, Stannard K, Liu J, et al. Suppression of metastases using a new lymphocyte checkpoint target for cancer immunotherapy. Cancer Discov 2016;6:446–459.

Harjunpää H, Blake SJ, Ahern E, et al. Deficiency of host CD96 and PD-1 or TIGIT enhances tumor immunity without significantly compromising immune homeostasis. Oncoimmunology 2018;7:e1445949.

Sun H. Update on the next generation of immune-oncology treatments: discovery of an anti-CD96 mAb as a novel check point inhibitor in solid tumors. Oral presentation at: 17th Annual PEGS Boston Virtual Conference & Expo; May 11–13, 2021.

Study of the safety and effectiveness of GSK6097608 in participants with advanced solid tumors. National Institutes of Health. Clinical Trials.gov. Accessed May 20, 2021. https://clinicaltrials.gov/ct2/show/NCT04446351

Ethics Approval

The study was reviewed and approved by the institutional review board and independent ethics committee before the study sites were initiated.

489 TWT-101: a phase 1 study of the novel HPK1 inhibitor CFI-402411 in patients with advanced cancer

Background

CFI-402411 is an orally available small molecule potent inhibitor of HPK1 (Hematopoietic progenitor kinase 1). T-cells are negatively-regulated at different junctures of cancer-immunity cycle by this regulatory kinase. HPK1, (also mitogen activated protein kinase kinase kinase kinase 1 (MAP4K1)) is a protein serine/threonine kinase predominantly expressed in hematopoietic cells. In T-cells, following T-cell receptor activation, HPK1 is recruited to the plasma membrane where it phosphorylates the adapter protein SH2 domain-containing leukocyte protein of 76 kDa (SLP-76), down-regulating signaling events required for T cell activation and proliferation. Selected for development based on its pharmacologic properties and preclinical activity in a variety of syngeneic cancer models and assays, with an IC50 = 4.0±1.3 nM, CFI-402411 is expected to relieve HPK1-mediated inhibition of T and B cells, facilitating an anti-tumor immune response.

Methods

Phase 1, 3 + 3 design in patients. Patients have acceptable laboratory, other parameters for study entry. Single agent dose daily oral escalation cohort (A1) in advanced tumors, then dose expansion (A3) with biomarker backfill (A2) in select advanced tumors; combination with PD-1 Inhibitor (pembrolizumab) (B1, pembrolizumab eligible tumors with no prior grade >=3 related to CPI)) and expansion (B2, PD-1/PD-L1 naïve pembrolizumab eligible tumors). DLT defined as any grade >=3 toxicity in first cycle of therapy (21d cycles). Standard assessments for response per RECIST v1.1 or iRECIST. The starting dose level was 80mg.

Results

At 10 June 2021 data is available for 12 patients from A1. Median age 61.5 years (range 33–73), 8 patients female, and 10 white. Diagnoses were pancreatic cancer, colorectal (3 pts), ovarian, basal cell, cholangiocarcinoma, sigmoid, salivary and breast cancer (1 pt). Six patients (50%) had 4 prior therapies, 1 patient (basal cell) had prior treatment with immune checkpoint inhibitor, pembrolizumab. Four doses studied: 80, 120, 180 and 270mg. TEAEs across all CTCAE grades, (in >2 patients) were diarrhea (6 patients), nausea (4 patients), dyspepsia (3 patients), fatigue (3 patients). No related grade 3–5 events, one immune related event (grade 1, weight loss). 3 grade 3 events all unrelated to study drug - pleural effusion, rash, thromboembolic event. Discontinuation due to disease progression was main reason (7 patients). PK and PD assessments will be updated at time of presentation.

Conclusions

CFI-402411 is a potent inhibitor of HPK1 that is well tolerated with a manageable adverse event profile and dose escalations continue. Further safety and efficacy results will be presented at the meeting including additional cohorts if available.

Acknowledgements

Treadwell Therapeutics thanks all sites, importantly their patients and their families.

Trial Registration

ClinicalTrials.

gov Identifier: NCT04521413

Ethics Approval

This study obtained has obtained ethics approvals at multiple institutions globally including;USAWCG IRB - Western Institutional Review Board - MOD00002618 (Submission ID)IntegReview Institutional Review Board - N/AAdvarra Central IRB - SSU00130103IntegReview Institutional Review Board N/AAdvarra Central IRB - SSU00137751Advarra Central IRB - SSU00143275The University of Texas MD Anderson Cancer Center Institutional Review Board - 2020–0678 (IRB ID Number)Hong KongJoint Chinese University of Hong Kong - New Territories East Cluster Clinical Research Ethics Committee - 2020.367 (Ref Number)CanadaOntario Cancer Research Ethics Board - 3320 (Project ID)Health Research Ethics Board of Alberta, HREBA Cancer Committee - HREBA.CC-20–0504 (Ethics ID Number)South KoreaimCORE - Seoul National University Hospital Institutional Review Board - H-2012-094-1182 (IRB Number)National Cancer Institute Review Board - 2020–0525–0001 (Receipt Number)All participants gave informed consent before taking part in this clinical trial.

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.

544 DELTA-1: A global, multicenter phase 2 study of ITIL-168, an unrestricted autologous tumor-infiltrating lymphocyte (TIL) cell therapy, in adult patients with advanced cutaneous melanoma

Background

Patients with advanced cutaneous melanoma and persistent disease after checkpoint inhibitor therapy have poor outcomes and limited treatment options, highlighting a significant unmet medical need.1 Autologous TIL cell therapies have shown promise in this population attributable, in part, to their intrinsic and patient-specific antitumor activity2; however, no such therapies are approved. Made from each patient‘s digested and cryopreserved tumor, ITIL-168 is an autologous TIL cell therapy manufactured to offer an unrestricted T-cell receptor repertoire. A single-center compassionate use clinical series demonstrated the feasibility and clinical utility of an earlier version of ITIL-168.3 DELTA-1 is a global, multicenter phase 2 study to evaluate efficacy and safety of ITIL-168. DELTA-1 will enroll patients with melanoma relapsed after or refractory to PD-1 inhibitors (PD-1i), patients intolerant to PD-1i, and patients whose best response to PD-1i was stable disease.

Methods

Patients aged ≥18 years with histologically confirmed advanced cutaneous melanoma, ECOG performance status 0–1, and adequate organ function will be enrolled in 1 of 3 cohorts. Cohort 1 (n≈80) will include patients who relapsed after or were refractory to ≥1 prior line of systemic therapy, including a PD-1i and, if BRAF-mutated, a BRAFi ± MEKi. Cohorts 2 and 3 (n≈25 each) will include patients intolerant to PD-1i and those with stable disease after ≥4 doses of PD-1i, respectively. After tumor resection for TIL harvest, patients must have ≥1 remaining measurable lesion per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Patients with uveal, acral, or mucosal melanoma, prior allogeneic transplant or cell therapy, and with central nervous system (CNS) disorder or symptomatic and/or untreated CNS metastases are ineligible. Patients will receive 5 days of lymphodepleting chemotherapy (cyclophosphamide ×2 days overlapping with fludarabine ×5 days) followed by a single ITIL-168 infusion (≥5×109 cells) and supportive short course high-dose IL-2. The primary endpoint is objective response rate (ORR) per central review. Key secondary endpoints include duration of response, progression-free survival, overall survival, disease control rate, TIL persistence, and safety. Hypothesis testing of ORR will be performed for cohort 1. Two interim analyses will occur after 20 patients in cohort 1 have been followed for ≥28 days (safety) and evaluated for response ≥3 months after ITIL-168 infusion (futility). The primary analysis will occur when all patients in the cohort 1 modified intent-to-treat population have been followed for ≥6 months after the first posttreatment disease assessment.

Acknowledgements

Medical writing support was provided by Christopher Waldapfel, PharmD, of Instil Bio, Inc, and Phylicia Aaron, PhD, of Nexus GG Science, with funding from Instil Bio, Inc.

References

Schadendorf D, van Akkoi ACJ, Berking C, et al. Melanoma. Lancet 2018;392(10151):971–984.

Borch TH, Anderson R, Ellebaek E, et al. Future role for adoptive T-cell therapy in checkpoint inhibitor-resistant metastatic melanoma. J Immunother Cancer 2020;8(2):e000668.

Hawkins RE, Jiang Y, Lorigan PC, et al. Clinical feasibility and treatment outcomes with unselected autologous tumor infiltrating lymphocyte therapy in patients with advanced cutaneous melanoma. Cancer Res 2021;81(13):LB150.

Ethics Approval

All patients will provide written informed consent. The study will be approved by the Institutional Review Board/Independent Ethics Committee at each site and conducted in accordance with the Good Clinical Practice Guidelines of the International Conference on Harmonisation.

Consent

N/A; the abstract does not contain sensitive or identifiable patient information.

Avelumab in patients with previously treated metastatic Merkel cell carcinoma (JAVELIN Merkel 200): updated overall survival data after >5 years of follow-up

BACKGROUND

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that has a poor prognosis in patients with advanced disease. Avelumab [anti-programmed death-ligand 1 (PD-L1)] became the first approved treatment for patients with metastatic MCC (mMCC), based on efficacy and safety data observed in the JAVELIN Merkel 200 trial. We report long-term overall survival (OS) data after >5 years of follow-up from the cohort of patients with mMCC whose disease had progressed after one or more prior lines of chemotherapy.

PATIENTS AND METHODS

In Part A of the single-arm, open-label, phase II JAVELIN Merkel 200 trial, patients with mMCC that had progressed following one or more prior lines of chemotherapy received avelumab 10 mg/kg by intravenous infusion every 2 weeks until confirmed disease progression, unacceptable toxicity, or withdrawal. In this analysis, long-term OS was analyzed.

RESULTS

In total, 88 patients were treated with avelumab. At data cut-off (25 September 2020), median follow-up was 65.1 months (range 60.8-74.1 months). One patient (1.1%) remained on treatment, and an additional patient (1.1%) had reinitiated avelumab after previously discontinuing treatment. Median OS was 12.6 months [95% confidence interval (CI) 7.5-17.1 months], with a 5-year OS rate of 26% (95% CI 17% to 36%). In patients with PD-L1+ versus PD-L1- tumors, median OS was 12.9 months (95% CI 8.7-29.6 months) versus 7.3 months (95% CI 3.4-14.0 months), and the 5-year OS rate was 28% (95% CI 17% to 40%) versus 19% (95% CI 5% to 40%), respectively (HR 0.67; 95% CI 0.36-1.25).

CONCLUSION

Avelumab monotherapy resulted in meaningful long-term OS in patients with mMCC whose disease had progressed following chemotherapy. These results further support the role of avelumab as a standard of care for patients with mMCC.

Multicenter, double-blind, placebo-controlled trial of seviprotimut-L polyvalent melanoma vaccine in patients with post-resection melanoma at high risk of recurrence

BACKGROUND

Most patients with advanced melanomas relapse after checkpoint blockade therapy. Thus, immunotherapies are needed that can be applied safely early, in the adjuvant setting. Seviprotimut-L is a vaccine containing human melanoma antigens, plus alum. To assess the efficacy of seviprotimut-L, the Melanoma Antigen Vaccine Immunotherapy Study (MAVIS) was initiated as a three-part multicenter, double-blind, placebo-controlled phase III trial. Results from part B1 are reported here.

METHODS

Patients with AJCC V.7 stage IIB-III cutaneous melanoma after resection were randomized 2:1, with stage stratification (IIB/C, IIIA, IIIB/C), to seviprotimut-L 40 mcg or placebo. Recurrence-free survival (RFS) was the primary endpoint. For an hypothesized HR of 0.625, one-sided alpha of 0.10, and power 80%, target enrollment was 325 patients.

RESULTS

For randomized patients (n=347), arms were well-balanced, and treatment-emergent adverse events were similar for seviprotimut-L and placebo. For the primary intent-to-treat endpoint of RFS, the estimated HR was 0.881 (95% CI: 0.629 to 1.233), with stratified logrank p=0.46. However, estimated HRs were not uniform over the stage randomized strata, with HRs (95% CIs) for stages IIB/IIC, IIIA, IIIB/IIIC of 0.67 (95% CI: 0.37 to 1.19), 0.72 (95% CI: 0.35 to 1.50), and 1.19 (95% CI: 0.72 to 1.97), respectively. In the stage IIB/IIC stratum, the effect on RFS was greatest for patients <60 years old (HR=0.324 (95% CI: 0.121 to 0.864)) and those with ulcerated primary melanomas (HR=0.493 (95% CI: 0.255 to 0.952)).

CONCLUSIONS

Seviprotimut-L is very well tolerated. Exploratory efficacy model estimation supports further study in stage IIB/IIC patients, especially younger patients and those with ulcerated melanomas.

TRIAL REGISTRATION NUMBER

NCT01546571.

Long-term outcomes in patients with advanced melanoma who had initial stable disease with pembrolizumab in KEYNOTE-001 and KEYNOTE-006

Objective:

Patients with melanoma and early stable disease (SD) with pembrolizumab have unclear prognosis. We present post hoc analyses of long-term outcomes for patients with early SD, partial response (PR) or complete response (CR) with pembrolizumab.

Patients and methods:

Patients who received pembrolizumab in the KEYNOTE-001 and KEYNOTE-006 studies and had SD, PR or CR at weeks 12 or 24 were included.

Results:

Of 294 patients in the week 12 analysis, 107 (36.4%) had SD at week 12, of whom 7 (6.5%) had a best overall response of CR, 43 (40.2%) had PR and 57 (53.3%) had SD. Forty-eighte–month overall survival (OS) rates were 95.2%, 73.0% and 47.7%, respectively, for patients with CR, PR and SD at week 12. Similar results were observed in the 241 patients in the week 24 analysis. Forty-eight–month OS rates were 72.1% for patients with SD at week 12 followed by subsequent response and 75.0% for patients with PR at week 12 followed by no change in response or progression. Thirty-six–month and 48-month OS rates were 11.6% and not reached, respectively, for patients with SD at week 12 followed by progression before week 24.

Conclusions:

A substantial proportion of patients (46.7%) with early (week 12) SD with pembrolizumab achieved subsequent PR or CR. Patients with SD at week 12 and subsequent CR/PR had similar survival to those who maintained PR. In contrast, patients with SD at week 12 and subsequent progression had poor survival outcomes. These findings may guide treatment decisions for patients achieving early SD.

Trial registration:

Clinicaltrials.gov: NCT01295827 (KEYNOTE-001); NCT01866319 (KEYNOTE-006).

Overall Survival Benefit with Tebentafusp in Metastatic Uveal Melanoma

BACKGROUND

Uveal melanoma is a disease that is distinct from cutaneous melanoma, with a low tumor mutational burden and a 1-year overall survival of approximately 50% in patients with metastatic uveal melanoma. Data showing a proven overall survival benefit with a systemic treatment are lacking. Tebentafusp is a bispecific protein consisting of an affinity-enhanced T-cell receptor fused to an anti-CD3 effector that can redirect T cells to target glycoprotein 100-positive cells.

METHODS

In this open-label, phase 3 trial, we randomly assigned previously untreated HLA-A*02:01-positive patients with metastatic uveal melanoma in a 2:1 ratio to receive tebentafusp (tebentafusp group) or the investigator's choice of therapy with single-agent pembrolizumab, ipilimumab, or dacarbazine (control group), stratified according to the lactate dehydrogenase level. The primary end point was overall survival.

RESULTS

A total of 378 patients were randomly assigned to either the tebentafusp group (252 patients) or the control group (126 patients). Overall survival at 1 year was 73% in the tebentafusp group and 59% in the control group (hazard ratio for death, 0.51; 95% confidence interval [CI], 0.37 to 0.71; P<0.001) in the intention-to-treat population. Progression-free survival was also significantly higher in the tebentafusp group than in the control group (31% vs. 19% at 6 months; hazard ratio for disease progression or death, 0.73; 95% CI, 0.58 to 0.94; P = 0.01). The most common treatment-related adverse events in the tebentafusp group were cytokine-mediated events (due to T-cell activation) and skin-related events (due to glycoprotein 100-positive melanocytes), including rash (83%), pyrexia (76%), and pruritus (69%). These adverse events decreased in incidence and severity after the first three or four doses and infrequently led to discontinuation of the trial treatment (2%). No treatment-related deaths were reported.

CONCLUSIONS

Treatment with tebentafusp resulted in longer overall survival than the control therapy among previously untreated patients with metastatic uveal melanoma. (Funded by Immunocore; ClinicalTrials.gov number, NCT03070392; EudraCT number, 2015-003153-18.).

Abstract CT141: A phase 1 trial of RTX-240, an allogeneic engineered red blood cell with cell -surface expression of 4-1BBL and trans-presented IL-15, in patients with advanced solid tumors

Short title: RTX-240 phase 1 in solid tumorsA phase 1 trial of RTX-240, an allogeneic engineered red blood cell with cell -surface expression of 4-1BBL and trans-presented IL-15, in patients with advanced solid tumorsBackground: T cell checkpoint inhibition has revolutionized the treatment of cancer, however the key challenge in cancer immunotherapy is the development of resistant disease. Immune agonists and cytokines are promising approaches, but have shown limited success in the clinic. RTX-240 is an allogeneic cellular therapy genetically engineered to express high-copy numbers of trimeric 4-1BBL and IL-15/IL-15R fusion proteins on the cell surface. RTX-240 is designed to activate and expand CD8+ memory T cells and NK cells, and is restricted to the normal biodistribution of red blood cells to mitigate toxicity. Safety, pharmacodynamic (PD) effects, pharmacokinetics and preliminary efficacy of RTX-240 were assessed in a phase 1 study in patients (pts) with solid tumors. Methods: Pts with relapsed/refractory solid tumors not eligible for standard therapy were treated in dose escalating cohorts with RTX-240 Q4 or Q6W until disease progression or unacceptable toxicity. An exploratory cohort of IV and intratumoral (IT) dosing was enrolled (QW IV and IT x3 in cycle 1 and Q4W IV in subsequent cycles). Results: As of 11 Dec 2020, 14 pts (median age 55) were treated across 4 dose levels (1x108 to 1x1010 cells) administered IV or IV/IT. Pts had received a median of 3.5 therapies (range, 1-10); 10 pts had received prior PD-1/PD-L1 inhibitor therapy. Common tumor types include colorectal or other GI cancers (n=5) and melanoma (n=5). No patients experienced DLTs and no related grade (gr) &gt;3 AE were observed. The most common related AE (gr 1-2) were fatigue (4 pts); chills, decreased appetite, arthralgia (3 pts each); and fever, myalgia, dysgeusia, nausea and hyperhidrosis (2 pts each). Additional irAE include gr 2 pneumonitis (n=1) and gr 1 elevated ALT/AST (n=1); the majority of irAE were observed in cycle 2 and beyond. RTX-240 was detected at the end of infusion sample in a dose dependent manner. Five pts (Q4W IV dosing) were evaluable for response by RECIST v1.1. A confirmed partial response (PR) was observed in 1 pt with anal cancer. Disease control, including stable disease or PR, occurred in 4/5 pts. PD studies in peripheral blood from all pts indicated increased numbers of NK cells in 12/14 pts (change from baseline, range 1.1-3 fold) and memory CD8+ T cells in 10/14 pts (change from baseline, range 1.2-3.3 fold). Activation of both NK and memory CD8+ T cells was observed by increased HLA-DR expression in 11/14 and 14/14 pts, respectively. Optional on-treatment biopsies are collected and preliminary data in one pt suggests infiltration of activated NK and T cells into the tumor microenvironment following dosing with RTX-240. Conclusions: RTX-240 is tolerable and leads to activation, expansion and trafficking of memory CD8+ T cells and NK cells, with preliminary evidence of anti-tumor activity. Exploration of the dose and schedule are ongoing in this study (NCT04372706).

Citation Format: Omid Hamid, Jason Luke, Alexander Spira, Geoffrey M. Kuesters, Iga Sienczylo, Gilad Gordon, Melissa L. Johnson. A phase 1 trial of RTX-240, an allogeneic engineered red blood cell with cell -surface expression of 4-1BBL and trans-presented IL-15, in patients with advanced 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 CT141.

Abstract CT173: Sunitinib (S) in patients (pts) with metastatic breast cancer (mBC) with FGFR1 mutations or amplifications: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study

Background: TAPUR is a phase II basket study evaluating anti-tumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. S is an oral multi-kinase inhibitor that inhibits Fibroblast Growth Factor Receptor family members 1-4 (FGFR1-4) in biochemical and cellular assays and is FDA approved in several tumor types. Results in a cohort of mBC pts with FGFR1 mutations (mut) or amplifications (amp) treated with S are reported.

Methods: Eligible pts had mBC, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was performed in CLIA-certified, CAP-accredited site selected labs. Pts received S 50 mg orally daily for four weeks followed by two weeks off, until tumor progression. Simon 2-stage design tested the null disease control (DC) - defined as partial (PR), complete response (CR) or stable disease at 16+ weeks (SD 16+) - rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 have DC, 18 more pts are enrolled. If ≥7 of 28 pts have DC, the null DC rate is rejected. Secondary endpoints are progression-free survival (PFS), overall survival (OS) and safety.

Results: Thirty pts with mBC with FGFR1 mut (1 pt), amp (28 pts), or both (1 pt) were enrolled from Oct 2016 to June 2019. 3 were not evaluable and excluded from efficacy analyses. Demographics and outcomes are summarized in Table 1. Two partial responses (PR) and 5 SD16+ (FGFR1 amp only) were observed for DC and OR rates of 29% (95% CI: 13%, 42%) and 7% (95% CI: 1%, 24%), respectively, and the null DC rate of 15% was rejected (p=0.09). S related grade 3-5 TAEs (Table 1) were consistent with the product label for S except encephalopathy.

Conclusions: Monotherapy S showed modest anti-tumor activity and clinically significant TAEs in heavily pre-treated pts with mBC with FGFR1 amplification.

Table 1.Demographics, Efficacy (N=27) and Toxicity Outcomes (N=30)Median age, yrs (range)61 (28, 81)Female, %97ECOG PS, %047137217Prior systemic regimens, %1-210≥390Hormone Receptor (HR) & HER2 Status, %HR (+) HER2 (-)77HR (-) HER2(-)13HR (+) HER2 (+)7Not reported3DC rate, % (OR or SD16+) (95% CI)29 (13, 42)OR rate, % (95% CI)7 (1, 24)Median PFS, wks (95% CI)8.7 (8.1, 15.7)Median OS, wks (95% CI)33.9 (23.0, 49.0)Number of Pts with Treatment-related AEs/SAEs (TAEs, maximum grade reported)Grade 211Grade 329Grade 4321Skin infection (SAE)2Cytopenia, encephalopathy (SAE), febrile neutropenia (SAE), increased alkaline phosphatase, Palmar-plantar erythrodysesthesia syndrome, vomiting3Cytopenia, hypertension

Citation Format: Carmen Calfa, Michael Rothe, Pam K. Mangat, Elizabeth Garrett-Mayer, Eugene Ahn, Keerthi Gogineni, Nitin Rohatgi, Monika L. Burness, Anu Gaba, Omid Hamid, Tareq Albaghdadi, Alison Conlin, Philip Gold, Jordi Rodon, Ramya Thota, Richard L. Schilsky. Sunitinib (S) in patients (pts) with metastatic breast cancer (mBC) with FGFR1 mutations or amplifications: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study [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 CT173.

Abstract CT002: Phase 3 randomized trial comparing tebentafusp with investigator's choice in first line metastatic uveal melanoma

Background: Metastatic uveal melanoma (mUM) has a poor prognosis with a 1-yr OS rate of 52%. No systemic treatment has proven an OS benefit in randomized trials. Tebentafusp (tebe), a bispecific consisting of an affinity-enhanced T cell receptor (TCR) fused to an anti-CD3 effector that can redirect T cells to target gp100+ cells, has shown promising activity in previously treated mUM pts. Here, we report the primary analysis of overall survival (OS) in the intention-to-treat population (ITT) of a Ph3 trial of tebe vs. investigator's choice (IC) as first line (1L) therapy in pts with mUM [NCT03070392].

Materials and Methods: In this randomized, open-label, Ph3 trial, 1L HLA-A*02:01+ pts with mUM were randomized 2:1 to receive tebe or IC of pembrolizumab, ipilimumab or dacarbazine, stratified by LDH. The primary endpoint was OS, defined as the time from randomization to death from any cause. Dual primary objectives were to evaluate 1) OS in the ITT population by comparing all tebe-randomized pts to all IC-randomized pts; and 2) OS in tebentafusp-treated patients with rash during week 1 versus all IC-treated patients. Secondary endpoints included safety and RECIST-defined overall response rate (ORR), progression free survival (PFS) and disease control rate (DCR). Here we present the OS in the ITT population. The study was unblinded by an independent data monitoring committee at the first pre-specified interim analysis. Investigator-reported radiographic-based endpoints were not mature at the first interim analysis. This analysis was conducted on the first interim analysis (data extracted Nov 2020).

Results: 378 pts were randomized to tebe (252) or IC, including pembrolizumab (103), ipilimumab (15) or dacarbazine (7). Tebe significantly prolonged OS compared to IC (HR 0.51; 95% CI 0.36-0.71; P&lt;0.0001) in the ITT population, with estimated 1-yr OS rate of 73.2% (95% CI 66.3-78.9) vs 57.5% (95% CI 47.0-66.6), respectively. The OS benefit of tebe was observed in pre-specified subgroups, including by stratification variable of LDH&gt;ULN and versus pembrolizumab IC. Most common TRAEs were skin-related (gp100+ melanocytes) or cytokine-mediated (T cell activation) and included pyrexia, pruritus, and rash. These AEs decreased in frequency and severity after the first 3-4 doses and were generally manageable with standard interventions. In the tebe arm, the rate of treatment discontinuation due to TRAEs was low (&lt;4%), and there were no treatment-related deaths.

Conclusions: In 1L treatment of mUM pts, tebe monotherapy significantly improved OS compared to IC; the first investigational therapy to improve OS in pts with mUM. Tebe had a predictable and manageable AE profile with a low rate of related discontinuation. Tebe is the first TCR therapeutic to demonstrate an OS benefit.

Citation Format: Sophie Piperno-Neumann, Jessica C. Hassel, Piotr Rutkowski, Jean-Francois Baurain, Marcus O. Butler, Max Schlaak, Ryan J. Sullivan, Sebastian Ochsenreither, Reinhard Dummer, John M. Kirkwood, Anthony M. Joshua, Joseph J. Sacco, Alexander N. Shoushtari, Marlana Orloff, Richard D. Carvajal, Omid Hamid, Shaad E. Abdullah, Chris Holland, Howard Goodall, Paul Nathan. Phase 3 randomized trial comparing tebentafusp with investigator's choice in first line metastatic uveal melanoma [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 CT002.

CX-072 (pacmilimab), a Probody PD-L1 inhibitor, in combination with ipilimumab in patients with advanced solid tumors (PROCLAIM-CX-072): a first-in-human, dose-finding study

BACKGROUND

Probody® therapeutics are antibody prodrugs designed to be activated by tumor-associated proteases. This conditional activation restricts antibody binding to the tumor microenvironment, thereby minimizing 'off-tumor' toxicity. Here, we report the phase 1 data from the first-in-human study of CX-072 (pacmilimab), a Probody immune checkpoint inhibitor directed against programmed death-ligand 1 (PD-L1), in combination with the anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) antibody ipilimumab.

METHODS

Adults (n=27) with advanced solid tumors (naive to PD-L1/programmed cell death protein 1 or CTLA-4 inhibitors) were enrolled in the phase 1 combination therapy dose-escalation portion of this multicenter, open-label, phase 1/2 study (NCT03013491). Dose-escalation pacmilimab/ipilimumab followed a standard 3+3 design and continued until the maximum tolerated dose (MTD) was determined. Pacmilimab+ipilimumab was administered intravenously every 3 weeks for four cycles, followed by pacmilimab administered every 2 weeks as monotherapy. The primary objective was identification of dose-limiting toxicities and determination of the MTD. Other endpoints included the rate of objective response (Response Evaluation Criteria In Solid Tumors v.1.1).

RESULTS

Twenty-seven patients were enrolled in pacmilimab (mg/kg)+ipilimumab (mg/kg) dose-escalation cohorts: 0.3+3 (n=6); 1+3 (n=3); 3+3 (n=3); 10+3 (n=8); 10+6 (n=6); and 10+10 (n=1). Dose-limiting toxicities occurred in three patients, one at the 0.3+3 dose level (grade 3 dyspnea/pneumonitis) and two at the 10+6 dose level (grade 3 colitis, grade 3 increased aspartate aminotransferase). The MTD and recommended phase 2 dose was pacmilimab 10 mg/kg+ipilimumab 3 mg/kg administered every 3 weeks. Pacmilimab-related grade 3-4 adverse events (AEs) and grade 3-4 immune-related AEs were reported in nine (33%) and six (22%) patients, respectively. Three patients (11%) discontinued treatment because of AEs. The overall response rate was 19% (95% CI 6.3 to 38.1), with one complete (anal squamous cell carcinoma) and four partial responses (cancer of unknown primary, leiomyosarcoma, mesothelioma, testicular cancer). Responses lasted for >12 months in four patients.

CONCLUSIONS

The MTD and recommended phase 2 dose of pacmilimab (10 mg/kg)+ipilimumab (3 mg/kg) every 3 weeks is active and has a favorable tolerability profile.