Abstract CT016: MEDI5752, a novel PD-1/CTLA-4 bispecific checkpoint inhibitor for advanced solid tumors: First-in-human study
Authors: Tran Ben , Voskoboynik Mark , Kim Sang-We , Lemech Charlotte , Carcereny Enric , Rha Sun Young , Ahn Myung-Ju , Felip Enriqueta , Lee Ki H. , Alvarez Eduardo C. , Yang James Chih-Hsin , Ascierto Paolo A. , Pulla Mariano P. , Freeman Dan , Song Xuyang , Gainer Shelby D. , Mitchell Patrick , Achour Ikbel , Subramaniam Deepa S. , Im Seock-Ah 
Published: June 2022

Background: MEDI5752 is a monovalent bispecific antibody targeting PD-1 and CTLA-4. The bispecific format is engineered to preferentially inhibit these two checkpoints on activated T cells in tumors, where co-expression is particularly abundant. This may maximize tumor-specific response and reduce the peripheral toxicity that is common when targeting these checkpoints independently. Here we present dose-escalation data from a phase I, open-label, multicenter study in advanced solid tumors (NCT03530397).

Methods: Eligible patients (pts) were ≥18 years old (ECOG PS 0-1) with tumors not amenable to standard therapy. Pts were treated at 10 dose levels from 2.25-2500 mg IV Q3W until progression or unacceptable toxicity. Primary objectives were safety and identification of maximum tolerated dose (MTD). Secondary objectives included preliminary antitumor activity by RECIST v1.1, PK and immunogenicity. Exploratory objectives included evaluation of pharmacodynamic (PD) biomarkers.

Results: At data cutoff (Sept 30, 2021), 86 pts (median age, 60.5 years; male, 75.6%; Asian, 57.0%) were enrolled. The most common tumor types were RCC (22.1%), NSCLC (16.3%), and head and neck cancer (8.1%); 95.2% had received prior systemic therapy and 90.7% were immunotherapy-naïve. MEDI5752 showed dose-dependent PK and sustained peripheral PD-1 receptor occupancy (&gt;90%) at doses &gt;225 mg. Dose-dependent increases in peripheral T cell proliferation (Ki67+) and activation (ICOS+) plateaued at doses ≥500 mg and demonstrated CTLA-4 specific blockade in the range of tremelimumab 6-10 mg/kg. At doses ≥500 mg, MEDI5752 significantly expanded new and existing T-cell clones, likely broadening the tumor antigen-driven T-cell response. Across all doses, objective responses were seen in 19.8% of pts (n=17, 1 complete and 16 partial [PR]). Median duration of response was 17.5 months. Molecular response (defined as ≥50% reduction in ctDNA) occurred in 36.5%. Doses ≥1500 mg (n=53) were poorly tolerated with Grade (G) 3/4 treatment-related AEs (TRAEs) in 50.9%; discontinuations due to TRAEs in 45.3%, and death in 1 (at 2000 mg). However, doses &lt;1500mg (n=33) had improved tolerability with G 3/4 TRAEs in 18.2% and discontinuations due to TRAEs in 9.1%. An MTD was not reached by protocol-defined DLT criteria. Immune-related AEs were also less common at doses &lt;1500 mg than at ≥1500 mg (G 3/4 in 18.2% vs 49.1%, respectively).

Conclusions: MEDI5752 showed encouraging antitumor activity with durable clinical benefit. Doses &lt;1500 mg were better tolerated than doses ≥1500 mg. Treatment led to robust dual checkpoint blockade, evidence of T-cell activation and expansion of new and existing T-cell clones at pharmacodynamic levels that exceeded what is clinically feasible with dosing of conventional anti-PD-1 plus anti-CTLA-4 antibodies. MEDI5752 is now being explored at doses &lt;1500 mg in multiple expansion cohorts.

Citation Format: Ben Tran, Mark Voskoboynik, Sang-We Kim, Charlotte Lemech, Enric Carcereny, Sun Young Rha, Myung-Ju Ahn, Enriqueta Felip, Ki H. Lee, Eduardo C. Alvarez, James Chih-Hsin Yang, Paolo A. Ascierto, Mariano P. Pulla, Dan Freeman, Xuyang Song, Shelby D. Gainer, Patrick Mitchell, Ikbel Achour, Deepa S. Subramaniam, Seock-Ah Im. MEDI5752, a novel PD-1/CTLA-4 bispecific checkpoint inhibitor for advanced solid tumors: First-in-human study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT016.