A New Star at SABCS 2025: BioNTech–BMS’s Pumitamig Redefines Next-Gen Immunotherapy 

A New Star at SABCS 2025: BioNTech–BMS’s Pumitamig Redefines Next-Gen Immunotherapy 

Dec 11, 2025

The 2025 San Antonio Breast Cancer Symposium (SABCS), the world’s leading forum for breast cancer research, highlights cutting-edge progress across the full spectrum of breast cancer, from prevention and molecular biology to new therapies and survivorship. This year’s focus includes several emerging strategies to reduce toxicity and improve outcomes in HER2-positive, HER2-negative, and triple-negative breast cancer (TNBC)

TNBC, accounting for about 10–15% of invasive breast cancers, remains a difficult subtype due to the absence of hormone receptors and HER2 expression, limiting targeted options. SABCS 2025 spotlights advances aimed at addressing these gaps and improving care across disease stages. According to DelveInsight’s TNBC Market Insight, Epidemiology and Market Forecast ꟷ 2034, TNBC accounts for approximately 105,000 cases in the 7MM in 2024, underscoring the continued need for therapeutic advancement.

Leading biopharma companies, including AstraZeneca, Novartis, Pfizer, and Daiichi-Sankyo, are driving key scientific updates at SABCS 2025. Among the highlights, BioNTech and Bristol Myers Squibb drew strong attention with new interim data on pumitamig. The two companies entered a global strategic partnership in June 2025 to co-develop and co-commercialize this next-generation bispecific antibody across multiple solid tumors.

Why are investors interested in this next-generation bispecific immunotherapy, Pumitamig (BNT327/BMS986545)?

  • Targets a genetically defined population: Pumitamig is a bispecific antibody that inhibits both PD-L1 and VEGF-A, targeting a genetically defined patient population: MTAP-detected cancers. MTAP deletion occurs in 10-15% of all solid tumors, creating a significant opportunity in this patient population.
  • Designed to overcome resistance with current PD-L1 therapies:  It is being assessed in a global randomized Phase II trial evaluating pumitamig plus chemotherapy in patients with locally advanced or metastatic TNBC, irrespective of PD-L1 expression.
  • Encouraging Early clinical data: Following promising Phase Ib/II treatment-naive results shared at SABCS 2024 (China Phase I/II trial: mPFS 13.4 months, 0RR 74%, cutoff date: Sept 2024), the new SABCS 2025 data reinforce its strong antitumor activity and manageable safety profile across both first- and second-line settings. These findings support its advancement into the pivotal Phase III (ROSETTA BREAST-01) trial and further highlight the growing momentum behind bispecific immunotherapies aimed at addressing the limitations of current checkpoint inhibitors.

Key Takeaways from the Phase II trial

Efficacy data: The interim analysis (data cut: October 1) included 74 patients treated in the first- or second-line setting for locally advanced or metastatic TNBC. In Cohort 1, 39 patients were evaluable for efficacy across both 1L and 2L therapy.

MeasureResult
Confirmed ORR (cORR)61.5%
Unconfirmed ORR (uORR)71.8%
Disease control rate (DCR)92.3%
uORR: 15 mg/kg63.2%
uORR: 20 mg/kg80.0%
uORR: PD-L1 CPS ≥10 and PD-L1 CPS <10Comparable uORRs were seen in both PD-L1 subgroups, 70.6%
uORR: 1L and 2L76.5% and 68.2%
9-month PFS59.3%

Safety data:

  • Pumitamig plus chemotherapy demonstrated a manageable safety profile across both cohorts.
  • Grade ≥3 treatment-related adverse events (TRAEs) occurred in 42.54% of Cohort 1 and 38.2% of Cohort 2, with no pumitamig-related deaths reported.

Pumitamig is expanding across 20+ clinical trials in 10+ solid tumors

Pumitamig is gaining attention as a next-wave bispecific immunotherapy, showing meaningful activity in advanced TNBC irrespective of PD-L1 expression, a hurdle that limits current checkpoint inhibitors. Supported by the first global TNBC dataset and expanding rapidly across 20+ clinical trials in 10+ solid tumors, the agent is also advancing through the ROSETTA program in multiple lung cancer settings, with two mid-stage SCLC studies reporting positive outcomes this year. 

ProgramIndicationMilestones in 2025 and Beyond*
Pumitamig1L/2L SCLCGlobal Phase II dose optimization data
1L/2L TNBCGlobal Phase II dose optimization data
*According to BioNTech’s 3rd Quarter 2025 presentation.

Momentum for this class is rising, following the rise of PD-L1/VEGF bispecifics such as ivonescimab, which drew industry attention after outperforming KEYTRUDA in lung cancer and prompted Merck’s USD 588 million upfront acquisition of LaNova Medicines’ LM-299. Despite advances in PD-L1 + chemotherapy mainly for PD-L1–high patients, many still relapse, and PD-L1–negative tumors remain heavily underserved, with chemotherapy as the default standard of care. 

What’s next? 

Apart from expansion in multiple indications, in the newly launched global phase III Rosetta Breast-01 trial, researchers are now focusing on patients with PD-L1 levels under 10%, effectively avoiding Merck’s Keytruda, which is only approved in the U.S. for use with chemotherapy in patients whose PD-L1 expression is 10% or higher. Interestingly, BioNTech and Bristol have chosen not to challenge Keytruda in the high PD-L1 expressor population with the Biotheus-originated program.

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