Phase II trial of BXCL701 and pembrolizumab in patients with metastatic pancreatic ductal adenocarcinoma (EXPEL-PANC): Preliminary findings.
Authors: Benjamin Adam Weinberg, Alexander Lekan, Allison Fitzgerald, Zoe Malchiodi, Martin Gutierrez, Anteneh A. Tesfaye, Ming Tony Tan, Marcus Smith Noel, Aiwu Ruth He, Reetu Mukherji, John Marshall, Princess Jones, Pascal Borderies, Vincent O'Neill, Louis M. Weiner
Journal: Journal of Clinical Oncology (2024)

LBA4132 Background: Pancreatic ductal adenocarcinoma (PDAC) has limited therapeutic options and is thought to be a “cold” tumor that does not respond to immunotherapy, due to a tumor microenvironment (TME) consisting of a desmoplastic stroma and poor T cell infiltrate. BXCL701 is an oral synthetic dipeptide that competitively inhibits dipeptidyl peptidases DPP4, DPP8, DPP9 and fibroblast activation protein (FAP). BXCL701 exerts antitumor activity via inhibition of DPP8/9, which is associated with induction of proinflammatory cytokines, as well as inhibition of FAP, which disrupts tumor-stromal interactions. Preclinical xenograft models demonstrate synergy between BXCL701 and PD-1 blockade, reducing tumor growth and promoting an increase in intratumoral CD4 + and CD8 + T cells, macrophages and NK cells, with induction of host-protective immunity. Methods: This is a phase II trial of BXCL701 in patients with metastatic PDAC (mPDAC) following progression on 1 line of treatment for advanced disease and amenable to serial biopsies. BXCL701 is administered at 0.2 mg PO BID days 1-7 and 0.3 mg BID days 8-14 during cycle 1 (21 days) followed by 0.3 mg BID days 1-14 every 21 days in all other cycles, given with pembrolizumab 200 mg IV every 21 days (all cycles). The primary objective is to determine the 18-week progression-free survival rate (PFS 18weeks ). We estimate that historical 2 nd -line PFS 18weeks is 30% or less; using a Simon’s two-stage (minimax) design, a type I error rate of 0.05 and power of 80% if the true rate is 50%, we will need 19 patients in stage 1 and 20 in stage 2 (39 total). There is a safety lead-in phase of 6 patients. We plan to enroll 43 patients to account for a predicted 10% drop out of unevaluable patients. Correlative pharmacodynamic studies include imaging mass cytometry to examine 36 markers of the PDAC TME in tissue biopsies, as well as blood-based analyses of KRAS circulating tumor DNA, circulating markers of fibrosis, and IL-6. Enrollment began in Q3 2023 (NCT05558982). Results: Six patients have enrolled, 3 women and 3 men, median age 57.5 (range 37-80). One patient was progression-free at 18 weeks and 1 patient had stable disease (SD) at 9 weeks, not yet evaluable for the 18-week landmark. Objective response rate is 16% and disease control rate is 50% (RECIST: 1 partial response, -41%, and 2 patients with SD, -18% and 0%). Three patients had significant reductions in CA19-9 from baseline (-100%, -73%, and -97%). Median PFS and overall survival have not been reached (NR, 95% CI 1.45 months-NR and 0.92 months-NR, respectively). There have been no serious treatment-related safety events. The safety lead-in will complete after the next patient completes the 6-week safety window (1 patient was unevaluable). Conclusions: BXCL701 plus pembrolizumab is well-tolerated and shows early signs of potential clinical activity in patients with mPDAC refractory to chemotherapy. Clinical trial information: NCT05558982 .