Phase I Trial of M7824 (MSB0011359C), a Bifunctional Fusion Protein Targeting PD-L1 and TGFβ, in Advanced Solid Tumors

Purpose: M7824 (MSB0011359C) is an innovative first-in-class bifunctional fusion protein composed of a monoclonal antibody against programmed death ligand 1 (PD-L1) fused to a transforming growth factor-beta (TGF-beta) trap. Experimental Design In the 3+3 dose-escalation component of this phase 1 study (NCT02517398), eligible patients with advanced solid tumors received M7824 at 1, 3, 10, or 20 mg/kg once-every-2-weeks until confirmed progression, unacceptable toxicity, or trial withdrawal; additionally, a cohort received an initial 0.3 mg/kg dose to evaluate pharmacokinetics/pharmacodynamics (PK/PD), followed by 10 mg/kg dosing. The primary objective is to determine the safety and maximum tolerated dose (MTD); secondary objectives include PK, immunogenicity, and best overall response. Results: Nineteen heavily pretreated patients with ECOG 0-1 have received M7824. Grade >= 3 treatment-related adverse events occurred in 4 patients (skin infection secondary to localized bullous pemphigoid, asymptomatic lipase increase, colitis with associated anemia, and gastroparesis with hypokalemia). The MTD was not reached. M7824 saturated peripheral PD-L1 and sequestered any released plasma TGF-beta 1, -beta 2, and -beta 3 throughout the dosing period at >1 mg/kg. There were signs of efficacy across all dose levels, including 1 ongoing confirmed complete response (cervical cancer), 2 durable confirmed partial responses (PRs; pancreatic cancer; anal cancer), 1 near-PR (cervical cancer), and 2 cases of prolonged stable disease in patients with growing disease at study entry (pancreatic cancer; carcinoid). Conclusions: M7824 has a manageable safety profile in patients with heavily pretreated advanced solid tumors. Early signs of efficacy are encouraging and multiple expansion cohorts are ongoing in a range of tumors. (C) 2018 AACR.