Hernandez‐Aya, Leonel F.

9508 Background: Outcomes for pts with mMEL remain sobering despite access to available immunotherapies as the majority of pts are resistant or become refractory to checkpoint blockade with no approved treatments. CXCR1 and CXCR2 (CXCR1/2) signaling mediate myeloid immunosuppression and MEL growth, inversely correlating with anti-PD-1 response and pt survival. SX-682 is an oral allosteric inhibitor of CXCR1/2. As a single agent, SX-682 increases tumor CD8+ T cell infiltration and inhibits tumor growth in mouse MEL. Methods: This phase 1 dose-escalation with expansion trial (NCT03161431) evaluated pem and escalating doses of SX-682 (25 - 400 mg orally BID) in pts with mMEL in a 21-day cycle. Pts must have had progressive disease (PD) on prior anti-PD-1. Mucosal MEL and asymptomatic brain metastases were allowed. Escalation cohorts had a 21-day SX-682 monotherapy (MONO) run-in. Response assessment by RECIST 1.1 was every 2 cycles during combination (COMBO) treatment. Primary endpoint was safety: adverse events (AEs), dose-limiting toxicity (DLT) and maximally-tolerated dose (MTD). Secondary endpoints included objective response rate (ORR; complete [CR] + partial [PR] response), disease control rate (DCR; CR + PR + stable disease [SD]) and overall survival (OS). Results: As of October 2023, 51 pts were enrolled and treated; median age of 65 (range 24-91), 55% male, 61% elevated LDH, 39% BRAF mutated. All pts received prior anti-PD-1, 37 (73%) received combined anti-PD-1 and anti-CTLA-4, and 23 (45%) had ≥ 3 prior therapies. Steady-state blood SX-682 was dose-proportional. No MONO DLT or MTD was identified. The 200 mg dose cohort was expanded in COMBO based on safety and pharmacodynamics: mg BID dose (n) = 25 (3), 50 (3), 100 (6), 150 (8), 200 (31). Any grade and grade 3/4 treatment-related AEs (TRAEs) occurred in 75% and 43%, respectively, and discontinuation (DC) due to TRAEs in 20% (when uncomplicated neutropenia, a permitted effect from CXCR2 inhibition on bone-marrow trafficking, was excluded there were 25% grade 3/4 TRAEs and 12% DC [rash, transaminitis]). There was no infectious signal. At the 200 mg dose, the ORR was 21% in 19 evaluable pts (4 PR + 0 CR) and the DCR was 63% (8 SD + 4 PR). DCR significantly depended on SX-682 dose ( P vs. ≤100 mg): 0% (0/9) at ≤100 mg, 50% (3/6) at 150 mg ( P = 0.0440) and 63% (12/19) at 200 mg ( P = 0.0028). All 15 pts with disease control had progressed on anti-PD-1 and anti-CTLA-4. Median OS was longer in pts in the 200 mg cohort (14.7 months; 95% CI, 10.5 – NR [not reached], n = 31) than in pts treated with ≤100 mg SX-682 (7.4 months; 95% CI, 5.0 – NR; n = 10). Conclusions: SX-682 combined with pem had a tolerable safety profile and activity reflected by objective responses and clinically meaningful disease control in heavily pretreated mMEL pts with progression on anti-PD-1 and anti–CTLA-4. Clinical trial information: NCT03161431 .

Abstract Background: Cemiplimab is the first treatment approved in the US (as cemiplimab-rwlc) for patients with metastatic basal cell carcinoma (mBCC) or locally advanced disease (laBCC) after hedgehog inhibitor (HHI) treatment or for whom an HHI is not appropriate. Cemiplimab provided substantial clinical benefit and an acceptable safety profile in patients with laBCC who discontinued HHI therapy due to progressive disease (PD), intolerance, or no better than stable disease (SD) after 9 months (NCT03132636). Here, we present the primary analysis of the mBCC cohort. Methods: Patients with mBCC (nodal or distant) post-HHI treatment received cemiplimab 350 mg intravenously every 3 weeks for up to 93 weeks or until PD. The primary endpoint was objective response rate (ORR) by independent central review (ICR). Key secondary endpoints included safety and tolerability, ORR per investigator (INV) assessment, duration of response (DOR), progression-free survival (PFS), overall survival (OS), and complete response (CR) rate (data cutoff date: May 20, 2021). Results: Fifty-four patients were enrolled (70.4% male; median age 63.5 years [range, 38−90]; Eastern Cooperative Oncology Group performance status 0 [66.7%] and 1 [33.3%]). Median duration of follow-up was 8.4 months (range 1.5-36.2). ORR per ICR was 24.1% (95% confidence interval [CI], 13.5-37.6); with 1 CR and 12 partial responses (PRs). ORR per INV was 25.9% (95% CI, 15.0-39.7), with 2 CRs and 12 PRs. Among responders, median time to response per ICR was 4.0 months (range, 2.0−10.5). Estimated median DOR per ICR was 16.7 months (95% CI, 9.8-not evaluable). Disease control rate was 63.0% (95% CI, 48.7-75.7) per ICR and 70.4% (95% CI, 56.4-82.0) per INV. Median OS was not reached. Median PFS per ICR was 8.3 months (95% CI, 4.2-15.9). The most common treatment-related adverse events were fatigue (37.0%), diarrhea (14.8%), pruritus (13.0%), hyperthyroidism (9.3%), and arthralgia (9.3%) as well as hypothyroidism, asthenia, constipation, and maculo-papular rash (7.4% each). There were no treatment-related deaths. Conclusions: Cemiplimab provided clinically meaningful antitumor activity, including durable responses, and an acceptable safety profile in patients with mBCC who had progressed on or were intolerant to HHI therapy. Citation Format: Karl Lewis, Ketty Peris, Aleksander Sekulic, Alexander J. Stratigos, Lara Dunn, Zeynep Eroglu, Anne Lynn S. Chang, Michael R. Migden, Suk-Young Yoo, Kosalai Mohan, Ebony Coates, Emmanuel Okoye, Timothy Bowler, Jean-François Baurain, Oliver Bechter, Axel Hauschild, Marcus O. Butler, Leonel Hernandez-Aya, Lisa Licitra, Rogerio I. Neves, Emily S. Ruiz, Frank Seebach, David M. Weinreich, George D. Yancopoulos, Israel Lowy, Priscila Goncalves, Matthew G. Fury. Primary analysis of phase 2 results for cemiplimab in patients with metastatic basal cell carcinoma who progressed on or were intolerant to hedgehog inhibitors [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 CT165.

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.

Glembatumumab vedotin (CDX-011, GV) is a fully human Immunoglobulin G2 monoclonal antibody directed against glycoprotein NMB coupled via a peptide linker to monomethyl auristatin E (MMAE), a potent cytotoxic microtubule inhibitor. This phase II study evaluated the overall response rate and safety of GV, glycoprotein NMB (GPNMB) expression, and survival in patients with metastatic uveal melanoma. Eligible patients with metastatic uveal melanoma who had not previously been treated with chemotherapy received GV 1.9 mg/kg every three weeks. The primary endpoint was the objective response rate (ORR). Secondary endpoints included GPNMB expression, progression-free survival (PFS), overall survival (OS), and toxicity analysis. GPNMB expression was assessed pre- and post-treatment via immunohistochemistry for patients with available tumor tissue. Out of 35 patients who received treatment, two patients had confirmed partial responses (PRs; 6%), and 18 patients had a stable disease (SD; 51%) as the best objective response. 38% of the patients had stable disease >100 days. The grade 3 or 4 toxicities that occurred in two or more patients were neutropenia, rash, hyponatremia, and vomiting. The median progression-free survival was 3.1 months (95% CI: 1.5–5.6), and the median overall survival was 11.9 months (95% CI 9.0–16.9) in the evaluable study population. GV is well-tolerated in metastatic uveal melanoma. The disease control rate was 57% despite a low objective response rate. Exploratory immune correlation studies are underway to provide insight into target saturation, combination strategies, and antigen release.

10017 Background: Seviprotimut-L is a vaccine prepared from antigens of 3 human melanoma cell lines, administered with alum. Prior formulations induced T cell and antibody responses and improved survival in a small phase II clinical trial. Part B1 of MAVIS (Melanoma Antigen Vaccine Immunotherapy Study, a three part, Phase III clinical program), was a multicenter, double-blind, placebo-controlled trial to assess efficacy of seviprotimut-L, with the primary endpoint of relapse-free survival (RFS). The goal of Part B1 was to guide design of the pivotal Part B2. Methods: Patients with AJCC v7 stage IIB-III cutaneous melanoma, after surgical resection, age 18-75, ECOG PS 0-1, were randomized 2:1 to seviprotimut-L 40 mcg or placebo, injected subcutaneously every 2 weeks x 5, then monthly x 4, then every 3 months x 9. Patients were stratified by stage (IIB/C, IIIA, IIIB/C). Target enrollment was 325. The study was powered for assessment of RFS, with target hazard ratio (HR) of 0.625, one-sided alpha of 0.10, and power 80%. Final data are presented. Results: 347 patients were randomized. Arms were well-balanced. Treatment-related adverse events (AEs) led to discontinuation in 0.4% and 0%, respectively, for vaccine and placebo arms. There were no treatment-related SAEs. By intent-to-treat (ITT) analysis, RFS was not significantly longer for seviprotimut-L in the full study population but trended toward benefit (HR 0.88). Subgroup analysis based on planned stratification revealed the hazard ratio (HR) for the Stage IIB/IIC subset (randomization stratum, n=111) to be 0.65 (95% CI [0.37, 1.17]), favoring seviprotimut-L. Age can decrease immune competence: RFS was longer with vaccine for patients age <60 overall (N = 191, HR = 0.64 [0.38, 1.08]) and among Stage IIB/C patients (N = 52, HR = 0.32 [0.12, 0.86]). The effect modification interaction p value for age for stage IIB/IIC patients was 0.056. In a multivariable RFS model, for IIB/IIC patients <60 with ulceration (n=38), HR = 0.209 [0.07,0.61]. For overall survival, for patients < 60, HR = 0.41 [0.33,1.14] (n=191, 19 deaths) and for those ≥60, HR = 0.92 [0.39,2.12] (n = 156, 24 deaths). Conclusions: Seviprotimut-L is very well-tolerated. Subgroup efficacy analyses identified populations who may benefit from Seviprotimut-L: those with Stage IIB/IIC melanoma and those under age 60. These data support design of the definitive part B2 of the MAVIS phase III trial to test seviprotimut-L for stage IIB/C patients, with stratification by age and ulceration. Clinical trial information: NCT01546571.

Abstract Purpose: PD-1/L1 axis–directed therapies produce clinical responses in a subset of patients; therefore, biomarkers of response are needed. We hypothesized that quantifying key immunosuppression mechanisms within the tumor microenvironment by multiparameter algorithms would identify strong predictors of anti–PD-1 response. Experimental Design: Pretreatment tumor biopsies from 166 patients treated with anti–PD-1 across 10 academic cancer centers were fluorescently stained with multiple markers in discovery (n = 24) and validation (n = 142) cohorts. Biomarker-positive cells and their colocalization were spatially profiled in pathologist-selected tumor regions using novel Automated Quantitative Analysis algorithms. Selected biomarker signatures, PD-1/PD-L1 interaction score, and IDO-1/HLA-DR coexpression were evaluated for anti–PD-1 treatment outcomes. Results: In the discovery cohort, PD-1/PD-L1 interaction score and/or IDO-1/HLA-DR coexpression was strongly associated with anti–PD-1 response (P = 0.0005). In contrast, individual biomarkers (PD-1, PD-L1, IDO-1, HLA-DR) were not associated with response or survival. This finding was replicated in an independent validation cohort: patients with high PD-1/PD-L1 and/or IDO-1/HLA-DR were more likely to respond (P = 0.0096). These patients also experienced significantly improved progression-free survival (HR = 0.36; P = 0.0004) and overall survival (HR = 0.39; P = 0.0011). In the combined cohort, 80% of patients exhibiting higher levels of PD-1/PD-L1 interaction scores and IDO-1/HLA-DR responded to PD-1 blockers (P = 0.000004). In contrast, PD-L1 expression was not predictive of survival. Conclusions: Quantitative spatial profiling of key tumor-immune suppression pathways by novel digital pathology algorithms could help more reliably select melanoma patients for PD-1 monotherapy. Clin Cancer Res; 24(21); 5250–60. ©2018 AACR.