FPA150 in Patients With Advanced Solid Tumors

This is a Phase 1a/1b open-label, multicenter study to evaluate the dosing, safety, tolerability, PK, pharmacodynamics, and preliminary efficacy of FPA150 as monotherapy and in combination with pembrolizumab, an anti-PD1 antibody, in patients with advanced solid tumors. This study includes a Phase 1a FPA150 Monotherapy Dose Escalation, Phase 1a Monotherapy Dose Exploration, Phase 1a combination Safety Lead-in (FPA150 + pembrolizumab), a Phase 1b FPA150 Monotherapy Dose Expansion, and a Phase 1b combination Dose Expansion (FPA150 + pembrolizumab). The Phase 1a Monotherapy Dose Escalation will include an initial accelerated titration design followed by a standard 3+3 dose escalation design until the MTD and/or RD for Phase 1b is determined. The Phase 1a combination Safety Lead-In will start enrolling once the FPA150 monotherapy RD is identified in Phase 1a monotherapy dose escalation and will continue until the FPA150 MTD/RD in combination is identified. Phase 1a FPA150 monotherapy Dose Exploration may include cohorts that may enroll beyond 3 patients whose tumors express high levels of B7-H4 protein and/or have varying levels of B7H4 expression including low (\<10% IHC 2+ or 3+ scores) or no expression on their tumor cells (up to 20 additional patients across all dose levels) to further evaluate safety, PK, pharmacodynamics, and clinical activity at that dose (to be conditional upon the dose level clearing DLT criteria). Phase 1b will be the Dose Expansion (monotherapy and combination) portion of the study. Enrollment into Phase 1b Dose Expansion will begin after identification of the MTD and/or RD in Phase 1a (monotherapy and Safety Lead-in). Preliminary efficacy will be evaluated in Phase 1b in planned expansion cohorts that include patients with specific tumor types that are B7-H4+ advanced solid tumors.