Transcenta Holding Limited (06628.HK), a clinical stage biopharmaceutical company with fully-integrated capabilities in discovery, research, development and manufacturing of antibody-based therapeutics, announced that interim safety and efficacy data of dose expansion cohort from the phase I/II study of TST001 (Osemitamab), a humanized ADCC-enhanced anti-Claudin18.2 monoclonal antibody, in combination with Capecitabine and Oxaliplatin (CAPOX) as a first line treatment of locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) cancer was presented in a poster at the European Society for Medical Oncology (ESMO) Congress 2022.In first line treatment of advanced or metastatic G/GEJ cancer, early interim data of the first 15 patients with measurable disease receiving the combination of TST001 with CAPOX demonstrated a partial response rate of 73.3% and a disease control rate of 100% per RECIST1.1. Based on these encouraging data, the TST001 program is further accelerated and Health Authority consultations are being initiated. A global phase III clinical program of TST001 (Osemitamab) for the first line treatment of locally advanced or metastatic Claudin18.2 positive G/GEJ cancer is currently being planned.
1. Claudin18.2 is expected to be the most shining star target in gastric cancer
The European Society for Medical Oncology (ESMO) Congress 2022 was held in person in Paris and virtually between 9-13 September 2022. Around 2000 abstracts and late-breaking abstracts were presented during the congress days. Transcenta's poster with the dose expansion cohort interim data from the TST001 in combination with chemotherapy in first line treatment of locally advanced or metastatic G/GEJ cancer patients with Claudin18.2 expression was presented on Sept 12, 2022.
Data shows that as of August 4, 2022, 51 patients were enrolled and dosed including 36 patients treated with TST001 plus CAPOX at 6mg/kg Q3W in the expansion phase. Among the 15 patients with measurable disease and at least one post-treatment tumor assessment, 11 (73.3%) achieved partial response and four (26.7%) achieved stable disease. All 51 enrolled patients were evaluated for safety and tolerability. Treatment-emergent adverse events regardless of causality were mostly grade 1-2. Twelve (23.5%) patients experienced dose delay, five (9.8%) experienced dose reduction and no patient experienced discontinuation due to treatment related adverse events. In this study, TST001 also demonstrated a clear dose proportional pharmacokinetic profile, is consistent with those observed with TST001 monotherapy and in US patients. These data suggest that TST001 combined CAPOX is well tolerated and with promising efficacy in a broad gastric cancer patient population with tumors expressing Claudin18.2, including medium and high expressors. Furthermore, Transcenta has also developed a proprietary IHC assay to select patients with Claudin18.2 expressing tumors for registration enabling studies.
Despite progresses in the treatment of advanced gastric cancer with HER2, VEGF, VEGFR, or PD-1/PD-L1 targeted therapies, outcomes remain poor for 1st line patients with median overall survival of around 14 months. Claudin18.2 expression is observed at various levels in 50%-70% of gastric cancer patients, and at relatively high percentage in a variety of tumors including pancreatic, cholangiocarcinoma, ovarian and lung cancer. It is one of the hottest targets in cancer treatment.
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