Gastrointestinal is next for pumitamig

After acquiring half of the rights to pumitamig, BioNTech’s PD-L1 x VEGF bispecific antibody, for $1.5bn up front, Bristol Myers Squibb is set to advance two pivotal trials, one in colorectal and the other in gastric/GEJ cancers.

These trials mark a shift from BioNTech’s earlier strategy. Instead of first testing the bispecific antibody in a phase 2 single-arm exploratory trial, the asset will go straight into phase 2/3, with ORR as the primary endpoint in phase 2, and either PFS, or PFS and OS, as primaries in phase 3.

The first of the two studies, Rosetta CRC-203, will enrol first-line colorectal cancer patients who are negative for dMMR, MSI-H and BRAF V600E mutations, and evaluate pumitamig plus chemo, versus Avastin and chemo.

The design echoes broader interest in the space, with Summit recently disclosing plans to start Harmoni-GI3, a global phase 3 study of its Akeso-partnered project ivonescimab in first-line microsatellite-stable colorectal cancer. In the Chinese phase 2 AK112-206 study in the same setting, ivonescimab plus chemo produced an 82% ORR at ESMO 2024.

Meanwhile, the Rosetta Gastric-204 trial will test pumitamig plus chemo against Opdivo and chemo in untreated gastric, oesophageal and GEJ cancers. The leap into this indication is somewhat surprising given the absence of disclosed data so far; BioNTech hinted during its Q3 earnings call that “emerging data” supported the move, though no specific figures were revealed.

The trials are expected to begin in March 2026. The deal, signed in June, therefore looks set to make it to at least its first anniversary, which will trigger another milestone from Bristol. The anniversary payments total $2bn, spread over three years, with the only apparent condition that the agreement remains in place until 2028. BioNTech gained full rights to pumitamig through its $800m acquisition of Biotheus around a year ago.

Selected pumitamig pivotal studies

Source: OncologyPipeline