BMS and BioNTech's Pumitamig Shows Promise in Small Cell Lung Cancer

Bristol Myers Squibb (BMS) and BioNTech have reported encouraging results from a Phase II study of their investigational bispecific antibody, pumitamig (BNT327), in small cell lung cancer (SCLC). The data, presented at the 2025 World Conference on Lung Cancer, mark the first global readout for this anti-PD-L1/VEGF therapy and demonstrate consistent efficacy across different patient populations.

Impressive Response Rates in Phase II Trial

In the Phase II study, pumitamig, administered alongside standard-of-care chemotherapy, achieved a confirmed overall response rate (ORR) of 76.3% in 38 evaluable patients with extensive-stage SCLC. The treatment also demonstrated a remarkable 100% disease control rate, with 56.7% of patients experiencing tumor shrinkage. Nearly 90% of participants saw early tumor shrinkage, indicating rapid onset of action.

The median progression-free survival was reported at 6.8 months, although overall survival data were not yet mature at the time of the readout. These results align closely with earlier data from a Chinese patient population, where pumitamig showed a confirmed ORR of 85.4% and a disease control rate of 97.9%.

Advancing to Phase III

Building on these promising results, BioNTech and BMS have initiated a global Phase III study for pumitamig, named ROSETTA-LUNG01. This trial aims to evaluate the bispecific antibody plus chemotherapy as a first-line treatment option for extensive-stage SCLC. The study is expected to complete in September 2029, with analysts anticipating a potential launch in 2028.

Truist Securities, in a note to investors, highlighted the significance of this development, stating that BMS and BioNTech "are leading the race among the PD-(L)1 x VEGF bispecifics in SCLC." The firm projects that a successful launch could unlock a $1.4-billion revenue opportunity for the partners.

Mechanism of Action and Development History

Pumitamig's dual mechanism of action targets two fundamental cancer pathways. By blocking both PD-L1 and VEGF, the bispecific antibody prevents cancer cells from evading the immune response while also suppressing the formation of new blood vessels that sustain tumor growth.

The drug's development journey includes significant investments from both BioNTech and BMS. BioNTech acquired the original developer, Biotheus, in November 2024 for $800 million upfront and up to $150 million in milestones. Subsequently, in June 2025, BMS committed $11 billion to jointly develop the asset, underscoring the industry's confidence in pumitamig's potential.