The Board of Directors of Transcenta Holding Limited announced the results from the Phase I/IIa Cohort-G data for Osemitamab (TST001) plus Nivolumab and CAPOX as the first-line treatment of patients with advanced G/GEJ cancer. The study, which enrolled patients regardless of their CLDN18.2 and PD-L1 CPS expression, indicated encouraging efficacy data for the triple combination, especially in patients with high or medium (H/M) CLDN18.2 expression, regardless of their PD-L1 CPS value. The results showed that median progression-free survival (mPFS) reached 12.6 months in patients with H/M CLDN18.2 expression, any PD-L1 CPS, as well as in the 80% of patients with PD-L1 CPS<5. Using the group of patients with very low/no CLDN18.2 expression as surrogate control, the HR for the triple combination is 0.443 (95%CI, 0.205-0.958) in favor of the H/M expressors and in these patients, the confirmed overall response rate was 68%.

The majority (approximately 80%) of CLDN18.2 positive patients are PD-L1 CPS<5. Previous studies have found that the combination of Zolbetuximab+CAPOX in CLDN18.2 positive patients, regardless of the PD-L1 status, leads to an improvement in PFS from 6.80 to 8.21 months (HR = 0.687 (95% CI, 0.544-0.866) (Source: Shah, Manish A et al. Nature Medicine 2023 Aug. 29 (8): 2133-2141).

However, Nivolumab plus chemotherapy treatment in patients whose PD-L1 CPS is less than 5 produces very little benefit in PFS (median 7.5 vs 8.2 months with an HR of 0.93). (Source: Checkmate-649 study.) This Phase I/IIa Cohort-G data shows that the efficacy from the triple combo therapy of Osemitamab (TST001) plus Nivolumab and CAPOX compares very favorably with the historical data of Nivolumab plus CAPOX combination or Zolbetuximab plus CAPOX combination, including in patients with PD-L1 CPS<5. The first-line Osemitamab (TST001) plus Nivolumab and CAPOX for advanced G/GEJ cancer results of Cohort G Phase I/IIa data will be featured as a poster presentation (Abstract # 4048) on June 1, 2024 at the ASCO 2024 Annual Meeting in Chicago, IL USA.