Phase I safety and preliminary efficacy of PM1009, a bispecific antibody targeting TIGIT and PVRIG, in patients with advanced solid tumors.

Abstract

e14695 Background: PM1009 is an anti-TIGIT x PVRIG bispecific antibody containing a fully human anti-TIGIT IgG1 fused with a fully human anti-PVRIG scFv at the C terminus. PM1009 can potently block the TIGIT/CD155/CD112 and PVRIG/CD112 signaling pathways, and supports the depletion of TIGIT-positive Treg cells in the tumor microenvironment through FcγR engagement. This leads to the enhancement of T cell and NK cell activity towards the killing of tumor cells. PM1009 showed robust in vitro and in vivo efficacy with good safety in preclinical studies. Methods: This is the first-in-human study of PM1009, which includes a dose escalation stage (accelerated titration & 3+3 design) followed by dose expansion. In the dose escalation stage, PM1009 was administered as flat doses of 120, 300, 600 and 1200 mg for DLT evaluation after 3 weeks followed by administration Q2W. Primary endpoints were safety and tolerability, and the secondary endpoints were PK, ORR and DCR (per RECIST 1.1). Results: As of February 1, 2024, a total of 12 patients were enrolled for dose escalation and received at least one dose of PM1009, with 3 patients in each of the 120, 300, 600 and 1200 mg dose-levels. Median number of prior therapies was 5 lines (range 1- 9). No DLTs were observed up to 1200 mg. Any-grade TRAEs occurred in 11 patients (91.7%), and ≥ Grade 3 TRAEs occurred in 2 patients (16.7%). Any-Grade irAEs occurred in 7 patients (58.3%), and ≥ Grade 3 irAEs occurred in 1 patient (8.3%). Treatment interruption due to TRAE occurred in 2 patients (16.7%), with infusion related reaction (the main symptom was nausea, and the single infusion was eventually completed), and neutrophil count decrease respectively. Treatment discontinuation due to TRAE occurred in 2 patients (16.7%), with acute myocardial infarction, and neutrophil count decrease respectively. The most common TRAEs were ALP elevation (33.3%) and AST elevation (25.0%). 12 patients completed at least one tumor evaluation. The DCR per RECIST 1.1 by investigator was 33.3% (4/12; 95% CI: 9.92 - 65.11), best overall response was SD. Pharmacokinetics were dose-proportional with a terminal half-life of 5.2-7.4 days across the dose range of 120-1200 mg. Conclusions: PM1009 was well-tolerated up to 1200 mg with signs of anti-tumor activity. These findings support further clinical investigation of PM1009 especially for the combination with chemotherapy or PD-1/L1-based checkpoint inhibitors. Clinical trial information: NCT05607563 .