FPA150 (B7-H4 antibody) phase I update in advanced solid tumours: Monotherapy and in combination with pembrolizumab

Abstract

Background: FPA150 is a fully human antibody against B7-H4 (a transmembrane protein of the B7 family) blocking negative regulatory function in T cells. FPA150 additionally exhibits enhanced antibody-dependent cell-mediated cytotoxicity and in vivo synergizes with anti-PD1 agents. We initiated a phase Ia/Ib evaluation of safety, toler-ability, pharmacokinetics (PK), pharmacodynamics (PD) and activity in monotherapy (mono) and with anti-PD1 (combo). A current update of this ongoing trial is provided. Methods: Trial design (see table). Results: At 3/15/2019 data snapshot, 29 pts with solid tumors (12 ovarian, 7 GI, 3 GYN, 3 head/neck, 2 GU, and 2 other) received FPA150 in dose escalation (n ¼ 21) and dose exploration (n ¼ 8). FPA150 demonstrated $ dose-proportional exposure at doses !0.3 mg/kg and half-life of 1-2 weeks. To date, no dose-limiting toxicities, treatment-related serious adverse events or treatment-related adverse events (TRAEs) leading to drug discontinuation have been identified (1 Grade 3 TRAE of decreased lymphocyte count); others were Grade 1-2, with most common being diarrhea (16.7%), and fatigue (13.8%). Enrollment to phase Ib mono and phase Ia combo is ongoing. Expanded safety, PD and activity from phase Ib mono and phase Ia combo will be presented. Conclusions: FPA150 RD for phase Ib mono identified as 20 mg/kg (Sachdev, ASCO 2019). Mono appears well tolerated during dose escalation/exploration allowing evaluation in combination therapy. Sachdev, J et al. Phase Ia/1b study of first-in-class B7-H4 antibody, FPA150, as monotherapy in patients with advanced solid tumors. Proc Am.