NovaBridge Reports Mature Phase 1b Data for Givastomig

ROCKVILLE, Md. — October 25, 2026

Petosemtamab Combination Shows Antitumor Activity

As of May 15, 2026, the combination arm reported a median OS of 28.2 months, with a 12-month OS rate of 79%. Median PFS was 9.0 months (95% confidence interval [CI], 5.2–12.9), and the 12-month PFS rate was 40%. The ORR was 63%, including complete responses in 19% of efficacy-evaluable patients. Median DOR had not been reached at the data cutoff, and the estimated proportion of responders maintaining a response at 24 months was 55%. These endpoints provide different perspectives on treatment activity: OS measures time until death, PFS measures time until disease progression or death, ORR captures the proportion of patients with a defined tumor response, and DOR assesses how long responses persist. The reported results indicate that some patients experienced sustained responses, while the median PFS shows that disease progression remained a concern during follow-up. Clinical activity was observed across PD-L1 CPS and p16 subgroups, including HPV-positive and HPV-negative disease. These findings may be relevant because HNSCC includes biologically distinct tumors and patient outcomes can vary by disease characteristics. Nevertheless, subgroup observations from a small Phase 2 cohort should be interpreted cautiously and are not sufficient to establish consistent efficacy across all patient groups. The study included 45 treated patients in the first-line combination arm, while the headline efficacy measures were reported for 43 efficacy-evaluable patients. Patients received petosemtamab at 1,500 mg every two weeks plus pembrolizumab at 400 mg every six weeks until disease progression or unacceptable toxicity. The study is ongoing and evaluates petosemtamab both as monotherapy and in combination with pembrolizumab across HNSCC and other solid tumors. The current results provide a clinical rationale for continued investigation but require confirmation in larger, controlled Phase 3 studies.

Safety Profile and Potential Biological Mechanisms

The combination’s safety findings were described as manageable in the reported Phase 2 population. The most common treatment-emergent adverse events (TEAEs), including all grades and Grade 3–4 events, were asthenia at 51% and 7%, acneiform dermatitis at 51% and 7%, and rash at 49% and 2%, respectively. Infusion-related reactions occurred in 38% of patients, with Grade 3–4 reactions reported in 7%. All reported infusion-related reactions resolved. Genmab reported no Grade 5 adverse events and no treatment-related deaths in the combination arm. These results provide an initial overview of tolerability as follow-up becomes more mature, although they do not replace a complete assessment of treatment risks or establish how the combination compares with other treatment options. The frequency of skin-related adverse events and infusion reactions is relevant to clinical monitoring, and ongoing studies will provide additional information about the safety profile with longer exposure and larger patient populations. Petosemtamab, also known as GEN1158, is an investigational human IgG1-based bispecific antibody designed to target both epidermal growth factor receptor (EGFR) and leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5). Its proposed mechanisms include inhibiting EGFR-mediated signaling, promoting EGFR degradation in cancer stem-like cells expressing both EGFR and LGR5, and supporting innate immune-mediated activity through interactions with macrophages and natural killer cells. Genmab describes this combination of mechanisms as a potential way to address tumor growth and cells associated with recurrence. These mechanisms remain under clinical investigation, and their contribution to the observed patient outcomes has not been independently established by the reported Phase 2 results. Petosemtamab is not approved for marketing and should be considered an investigational treatment.

FDA Engagement and Phase 3 Planning Advance Givastomig

NovaBridge said its FDA interactions have informed important elements of the planned registrational strategy, including the intended patient population, dose and primary endpoints. The company reported alignment with the FDA on a global Phase 3 study protocol, although this does not constitute approval of givastomig or confirmation that future trial results will support marketing authorization. Givastomig has received Fast Track Designation for previously untreated HER2-negative advanced or metastatic gastroesophageal adenocarcinoma in combination with nivolumab and chemotherapy, as well as Orphan Drug Designation. These designations can support regulatory development and communication but do not establish efficacy or guarantee approval. The company is also evaluating givastomig in a global randomized Phase 2 study, identified as NCT07432295 in the announcement, following the Phase 1b program. Its potential development scope includes other CLDN18.2-positive gastrointestinal malignancies, such as biliary tract cancer and pancreatic ductal adenocarcinoma, although these remain investigational opportunities. NovaBridge plans to host an investor webcast on November 2, 2026, at 8:00 a.m. Eastern Time to discuss the updated clinical data, the selection of the 8 mg/kg dose and the pathway toward registrational development. The event is expected to feature Samuel J. Klempner, M.D., of Massachusetts General Hospital, alongside company management. The updated dataset provides a stronger basis for continued investigation by adding longer follow-up, response durability data and a defined dose for the next development stage. Ultimately, the clinical value of givastomig will depend on confirmation of its efficacy and safety in later-stage studies and assessment by regulators.

Source:Genmab ,Press release