Transcenta has revealed results showing that Osemitamab (TST001) plus Nivolumab and CAPOX improved progression-free survival (PFS) in patients with HER2-negative metastatic gastric or gastroesophageal (G/GEJ) adenocarcinoma in a Phase I/IIa trial.

The TranStar102 study (NCT04495296) investigated osemitamab in combination with Opdivo (nivolumab) and CAPOX in 82 patients in cohort G.

Patients benefitted from a median PFS of 12.6 months in the patients with high or medium CLDN18.2 expression (H/M), 8.5 months in patients with low expression (L) and 6.7 months in the rest patients (R).

The confirmed response rate was 68%, 61.1% and 50% respectively.

The safety profile of the triple combination therapy is generally consistent with the previously evaluated osemitamab and CAPOX combination. The main toxicities are on-target-off-tumour effects, including nausea, hypoalbuminemia, and vomiting, mostly grade 1 or 2.

Transcenta will present the results on June 1 at the American Society of Clinical Oncology (ASCO) 2024 annual meeting in Chicago, US.

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Transcenta chief medical officer Dr Caroline Germa said: “In this population, the triple combo treatment delivered significantly better PFS benefits than that of the doublet combinations of checkpoint inhibitor/chemo or CLDN18.2 targeted antibody plus chemo.”

Germa added that the data further validates a global Phase III trial (NCT06093425) of the combination, which received US Food and Drug Administration (FDA) clearance in October 2023.

Osemitamab is a high-affinity humanised anti-CLDN18.2 monoclonal antibody that has shown potent anti-tumour activity. It acts by killing CLDN18.2 expressing tumour cells through antibody-dependent cellular cytotoxicity (ADCC).

G/GEJ cancer landscape

The G/GEJ cancer market across the eight major markets (8MM: US, France, Germany, Italy, Spain, UK, Japan, and South Korea) was valued at $1.12bn in 2019, a GlobalData report states, with the marker forecast to reach $4.72bn by 2029.

Growth is set to be driven by sales of Opdivo and Keytruda in the first-line metastatic setting, with immunotherapies expected to dominate the G/GEJ market.

GlobalData is the parent company of the Clinical Trials Arena.