Transcenta Holding Limited ("Transcenta") (HKEX: 06628), a clinical stage biopharmaceutical company with fully-integrated capabilities in discovery, research, development and manufacturing of antibody-based therapeutics, announces that the enrollment of first-line (1L) CLDN18.2 expressing Gastric / Gastro-esophageal Junction (G/GEJ) adenocarcinoma patients in cohorts C and G for the China Phase II study (Transtar-102, NCT04495296) of its high affinity humanized ADCC-enhanced anti-CLDN18.2 monoclonal antibody Osemitamab (TST001) has been completed. Cohort G evaluates Osemitamab (TST001) in combination with Nivolumab plus Capecitabine and Oxaliplatin (CAPOX). Cohort C explores Osemitamab (TST001) in combination with CAPOX. Studies are ongoing in the U.S.

Transtar-102 (NCT04495296) is an ongoing Phase I/II, open-label, multi-cohort, multi-center clinical study in China to evaluate the safety, tolerability and efficacy of Osemitamab (TST001) as single agent or in combination in several different indications. Cohort G evaluates Osemitamab (TST001) at the dose of 3 or 6 mg/kg Q3W in combination with Nivolumab plus CAPOX in 1L non-resectable locally advanced or metastatic G/GEJ adenocarcinoma with various level of CLDN18.2 expression: a total of 82 patients have been enrolled. Preliminary data show the absence of unexpected safety findings; efficacy is immature. Full results from this cohort will be reported in future medical conferences.

Cohort C evaluates Osemitamab (TST001) in combination with CAPOX as 1L treatment of non-resectable locally advanced and metastatic G/GEJ cancer. Enrollment was completed by the end of 2022 and updated efficacy data including duration of response and median progression free survival will be presented in upcoming medical conferences.

These cohorts support the upcoming global Phase III pivotal trial to be initiated in the second half of 2023.

At ESMO 2022, Transcenta released encouraging interim safety and efficacy data for cohort C including anti-tumor activities in medium and low CLDN18.2 expressing G/GEJ tumors. Osemitamab (TST001) is designed to have higher affinity to bind CLDN18.2 on the tumor cells and enhanced NK cell mediated ADCC activity via fucose reduction. In preclinical models, Osemitamab (TST001) elicits potent in vitro and in vivo anti-tumor activities in CLDN18.2 low expressing gastric cancer tumors.

Gastric cancer (GC) remains the 4th leading cause of cancer death worldwide, accounting for about 7.7% of all cancer related mortality. Combinations of platinum and fluoropyrimidine are the preferred 1L chemotherapy regimen for patients with HER2 negative advanced gastric cancer. Nivolumab was approved in combination with chemotherapy for 1L treatment of patients with advanced or metastatic gastric cancer. Preclinical studies have demonstrated synergistic anti-tumor activities between Osemitamab (TST001) and PD-1 antibody in CLDN18.2 expressing tumor models. Osemitamab (TST001)in combination with Nivolumab plus chemotherapy could become a transformative treatment option for patients with gastric cancer.

"The completion of enrollment of these cohorts marks an important milestone for Transcenta. These clinical data lay the foundation of our Phase III and comply with dose optimization requirements from Health Authorities. They also provide important information related to the predictive role of CLDN18.2 expression on Osemitamab (TST001) associated outcomes, particularly in the medium and low expressors. We look forward to releasing these data in the very near future." said Dr. Caroline Germa, Transcenta's Executive Vice President, Global Medicine Development and Chief Medical Officer.