BioNTech and Bristol Myers Squibb have reported encouraging results from a Phase II trial of their next-generation cancer immunotherapy pumitamig (BNT327/BMS986545) in patients with extensive-stage small cell lung cancer (ES-SCLC). The investigational bispecific antibody targeting PD-L1 x VEGF-A achieved a 76.3% confirmed objective response rate when combined with standard chemotherapy in previously untreated patients.
Phase II Trial Results Show Strong Efficacy
The interim data, presented at the IASLC 2025 World Conference on Lung Cancer in Barcelona, demonstrated robust antitumor activity across multiple endpoints. Among 43 patients who received pumitamig in combination with standard of care chemotherapy, the treatment achieved a 100% disease control rate and a median progression-free survival of 6.8 months.
The trial evaluated 38 participants who qualified for the interim analysis, with the bispecific antibody showing its dual mechanism of action by both activating the immune system and cutting tumors off from their blood supply. This approach represents a significant advancement over traditional single-target immunotherapies.
Safety Profile Supports Continued Development
Pumitamig demonstrated a manageable safety profile with no new safety concerns identified during the trial. The discontinuation rate remained low at 14%, indicating good tolerability among patients. Pumitamig-related treatment-emergent adverse events of Grade ≥3 were reported in only one patient at dose level 1 and five patients at dose level 2.
The favorable safety data supports the drug's advancement to Phase III development, where it will face direct comparison with established treatments in the extensive-stage small cell lung cancer setting.
Major Investment Reflects High Expectations
Bristol Myers Squibb's commitment to this collaboration is substantial, with the company agreeing in June to pay up to $11.1 billion to partner with BioNTech on pumitamig development. This investment reflects the potential for the bispecific antibody to compete with established immunotherapies, particularly Merck's best-selling drug Keytruda.
The partnership positions both companies to challenge the current treatment landscape in small cell lung cancer, a particularly aggressive form of the disease with limited therapeutic options.
Phase III Trial Underway
Building on these promising Phase II results, a global randomized Phase III trial called ROSETTA LUNG-01 (NCT06712355) is currently ongoing. This pivotal study will evaluate the efficacy and safety of pumitamig plus chemotherapy versus atezolizumab plus chemotherapy as a first-line treatment in patients with untreated extensive-stage small cell lung cancer.
The companies express optimism that pumitamig could establish a new standard of care for first-line ES-SCLC treatment and potentially extend benefits to other solid tumor types. Several rival companies are pursuing similar dual-mechanism approaches, indicating the competitive landscape for next-generation cancer immunotherapies continues to intensify.
