FPT155-001: A phase Ia/Ib study of FPT155 (CD80-FC) in patients with advanced solid tumors.

Abstract

TPS42 Background: Despite recent advances in immunotherapy, many patients with advanced solid tumors are refractory to available therapies or eventually relapse. Novel immune therapies are needed with differentiated mechanisms of action that result in improved response rates and durability across a broad range of tumors. FPT155 is a first-in-class therapeutic being developed to meet this need. FPT155 is a recombinant fusion protein composed of the extracellular domain of human CD80 fused with the Fc domain of human immunoglobulin G1. It is designed to act as a potent stimulator of anti-tumor immunity through CD28 and thereby co-stimulate T cell responses only in the presence of antigenic T cell receptor (TCR) signaling. FPT155 alone does not induce spontaneous cytokine release by primary human immune cells, in contrast to a CD28 superagonist antibody that exerts TCR stimulus-independent activity. FPT155 also blocks CTLA-4 from competing for endogenous CD80, allowing CD28 signaling to prevail in T cell activation. A murine surrogate of FPT155 is a potent inhibitor of tumor growth that induces complete tumor regression in multiple tumor models, including models that are insensitive to anti-PD1 or anti-CTLA4. Methods: The FPT155-001 study is a Phase 1a/1b open-label, multicenter, dose escalation and expansion study to evaluate the safety and tolerability of FPT155 monotherapy. Phase 1a dose escalation includes an accelerated titration design followed by a standard 3+3 design until the recommended dose for Phase 1b is determined by evaluation of all available safety, pharmacokinetic (PK), and pharmacodynamic (PD) data. Eligible patients with advanced solid tumors who are refractory to all standard therapy for their malignancy will be enrolled in Phase 1a. Phase 1b dose expansion will enroll patients with select tumor types. The primary endpoint is safety in both phases. Key secondary endpoints in Phase 1a include characterization of the FPT155 PK profile and immunogenicity. Key secondary endpoints in Phase 1b include objective response rate, duration of response, progression free survival, and disease control rate. The FPT155-001 trial opened for enrollment in October 2018 and is in progress. Clinical trial information: Submitted - awaiting registration number.