Phase I/II safety and preliminary efficacy of PM1022, a bispecific antibody targeting PD-L1 and TIGIT, in patients with advanced solid tumors.

e14694 Background: PM1022 is an anti-PD-L1 × TIGIT bispecific antibody that is engineered with a fully human IgG targeting TIGIT in an IgG1 wild type Fc backbone, fused to a VHH at the c-terminus targeting PD-L1. The potential MOA includes releasing T cell inhibition by blocking both the PD-L1/PD-1 and CD155/CD112/TIGIT pathways, as well as depleting Treg cells in the tumor microenvironment and engaging FcγRs to activate myeloid cells. PM1022 showed robust in vitro and in vivo efficacy in preclinical studies, and this is the first in human study. Methods: This phase Ⅰ/Ⅱ study consists of a standard 3+3 dose escalation and dose expansion part. PM1022 was administered intravenously as monotherapy on Day 1 of 21-day cycle. The primary objectives were to assess safety, tolerability and pharmacokinetics in patients with advanced solid tumors. Results: As of January 28, 2024, a total of 15 patients in dose escalation part have received at least 1 dose of PM1022, with 3 patients in each of the 100, 200, 400, 800 and 1200 mg dose levels respectively. No DLT was observed up to 1200 mg. Of the 15 patients, TRAEs occurred in 8 patients (53.3%), ≥ Grade 3 TRAEs occurred in 1 patient with platelet count decreased. No patients were discontinued from PM1022 due to TRAE. The most common TRAEs were rash (20%) and aspartate transaminase increased (20%). 14 patients completed at least one tumor evaluation. The median duration of PM1022 exposure was 6.1 weeks (range, 5.0-48.0 weeks). The ORR per RECIST 1.1 was 7.1% with a DCR of 35.7%. Preliminary antitumor activity has been observed in 1 patient with NSCLC (1200 mg, still on treatment) with previous PD-L1 TPS 100% who was enrolled after previous 3 lines therapy, including chemotherapy and anti-PD-1 treatment, and had a partial response in target lesion with 56.8% reduction. Another patient with esophageal cancer had been on PM1022 for total of 48 weeks until initiation of new anti-cancer therapy. Pharmacokinetics were dose-proportional with a terminal half-life of 7-13 days across the dose range of 100-1200 mg. Conclusions: PM1022 was safe and well-tolerated up to 1200 mg Q3W with preliminary anti-tumor activity. These findings could support further exploration of PM1022 in advanced solid tumors. Clinical trial information: NCT05867771 .