MEDIPLEX: A phase 1 study of durvalumab (D) combined with pexidartinib (P) in patients (pts) with advanced pancreatic ductal adenocarcinoma (PDAC) and colorectal cancer (CRC).

Abstract

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Background: Targeting tumor associated macrophages is an emerging strategy to increase the responsiveness of PDAC and CRC to anti-PD(L)1. Pexidartinib (P) is an orally active, small-molecule kinase inhibitor that targets the colony-stimulating factor-1 receptor (CSF1R) on macrophages. Methods: Adult pts with advanced/ metastatic PDAC or CRC were treated with a fixed dose of D (1500mg q4w, IV) and ascending doses of P (400, 600, 800 and 1000mg/d, orally). Dose escalation was conducted according to a Likelihood Continual Reassessment Method with a 28-day window to evaluate dose-limiting toxicity (DLT), a stopping rule advised dose escalation termination in case of a high probability ( > 90%) for the next 6 pts to be assigned to the same dose. Following the determination of RP2D, 14 pts with PDAC and 14 pts with CRC who consented to serial tumor biopsies were enrolled in expansion cohorts to assess preliminary anti-tumor activity and biomarkers. Results: 19 pts (12M, 7F, median age, 56 y [range, 43-76y]) were enrolled in 4 dose escalation cohorts (P 400, 600 and 800mg/d: 3 pts each and P 1000mg/d: 10 pts). Pharmacokinetic analysis showed dose-dependent increase in the exposure of P from 400 to 1000 mg. Two DLTs (AST/ALT elevations including one with bilirubin increase) were seen at dose level P 1000mg/d. The most frequent ( > 2pts) related (to either D, P or both) AEs were: fatigue, maculopapular rash/pruritus/dry skin, hair color changes, anorexia, edema (periorbital, limbs or face), AST/ALT increases, bilirubin increases, nausea, vomiting and diarrhea. The most frequent (≥2pts) Grade ≥ 3 AEs related to P were: AST/ALT increase, ALP increase, neutrophil or white blood cell count decrease, and fatigue. Clinical benefit rate at 2 months was 21% (4 SD /19pts), 2 pts with MSI-H CRC had SD for more than 6 months including 1 pt still receiving single agent D after > 18 months. The RP2D for the combination was P 800mg/d + D 1500mg q4w. Enrolment in the expansion cohorts was completed in January 2019. Conclusions: Toxicity was consistent with the expected profiles of the individual drugs and no unexpected events were seen with the combination. Updated data will be presented at the meeting. Clinical trial information: NCT02777710.