Abstract A004: A Phase 1B/2 trial of second line immunotherapy with pepinemab and avelumab for patients with metastatic pancreatic adenocarcinoma

Abstract Background: Pancreatic adenocarcinoma (PDAC) is a leading cause of cancer-related mortality with poor prognosis despite maximal therapy and is recalcitrant to approved immunotherapies. In PDAC, Semaphorin 4D (SEMA4D) expression is prognostic in patients who have undergone surgical resection and correlates with tumor infiltration of activated CD8+ T-cells. Furthermore, preclinical studies suggest that monoclonal blockade of SEMA4D supports CD8+T cells tumoral infiltration and activation, sensitizing PDAC to immune checkpoint blockade (ICB). Thus, we hypothesized that a humanized anti-SEMA4D antibody (pepinemab) may improve disease control and responsiveness to ICB in patients with PDAC. Methods: We designed a phase Ib/II single-arm clinical trial to evaluate the safety, tolerability, and efficacy of pepinemab with anti-PD-L1 (avelumab) in patients with chemotherapy-refractory PDAC (NCT05102721). The study follows a dose de-escalation schema starting at a dose combination of 20mg/kg pepinemab and 800mg avelumab every two weeks. Patient accrual for phase 1b utilizes the Bayesian Optimal Interval design targeting a dose-limiting toxicity rate of 30% or less. After 16 subjects receive a given combination dose, a Simon’s two stage assessment of futility will be undertaken with expansion to phase 2 if 2 or more subjects demonstrate response. Treatment response is assessed via RECIST 1. 1 criteria with surveillance CT prior to enrollment and after completion of two cycles (8 weeks). Baseline and on-treatment tumor biopsies (after completion of one cycle, 4 weeks) are performed to analyze changes in immune, stromal, and genomic profiles to elucidate mechanisms of treatment response and failure. Patient reported outcomes are incorporated (FACT-Hep and FAACT subdomains) to assess disease-specific symptoms. Results: A total of 14 patients have been enrolled to date. Three subjects withdrew from the study prior to completing the evaluable period (four weeks of treatment) and nine subjects terminated treatment due to disease progression. Two subjects continue to receive combination treatment pending evaluation of tumor response. Baseline and on-treatment biopsies have been obtained and stored for correlative analysis from 8 evaluable subjects. One treatment-related adverse event occurred though the patient was able to complete treatment without further events. No treatment-related toxicities have been encountered. Conclusions: Combining pepinemab with avelumab appears to be safe and tolerable to date. Nine of eleven patients demonstrated disease progression, though 1 of these 9 demonstrated mixed response with some lesions showing radiologic partial and even complete response. Overall treatment response, survival data, and correlative science forthcoming. Citation Format: Luis I Ruffolo, Matthew Byrne, Bailey Hilty, Brian A Belt, Yatee Dave, Paul Burchard, Terrence Fisher, Elizabeth E. Evans, Crystal Mallow, Megan Boise, Darren Carpizo, Jen Jen Yeh, David C Linehan, Daniel Mulkerin. A Phase 1B/2 trial of second line immunotherapy with pepinemab and avelumab for patients with metastatic pancreatic adenocarcinoma abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84 (17 Suppl₂): Abstract nr A004.