ESMO: Jazz HER2 Bispecific Achieves 59% Survival at 30 Months in Gastric Cancer

Jazz Pharmaceuticals has unveiled new phase 2 clinical data for its HER2-targeted bispecific antibody, zanidatamab, at the European Society for Medical Oncology conference in Barcelona, Spain. The data indicates a 59% survival rate for patients with metastatic gastroesophageal cancer (mGEA) over at least 30 months when the antibody is administered in combination with chemotherapy. This follows an earlier 18-month data release at the start of 2023, which showed an overall survival (OS) rate of 84%.

Dr. Robert Iannone, Jazz’s Global Head of R&D, emphasized that the updated results reinforce zanidatamab's potential as a foundational treatment for HER2-positive mGEA. He noted that the 30-month data provides additional insights into the drug's efficacy, including a confirmed objective response rate (cORR) of 84%, up from 79% in the previous 18-month data. The median duration of response (DoR) was reported at 18.7 months, while the median progression-free survival (PFS) stood at 15.2 months. One more patient achieved a complete response since the 18-month data, bringing the total to four out of 37 response-evaluable patients.

Iannone stated that while direct comparisons with other oncology treatments are not possible due to the lack of head-to-head trials, the metrics for ORR, DoR, PFS, and OS for zanidatamab are favorable when compared to the front-line standard of care involving Herceptin combined with chemotherapy. The potential of HER2-targeted treatment for GEA was initially demonstrated in 2010, when adding Roche’s Herceptin to chemotherapy extended overall survival from 11.1 months to 13.8 months.

The 30-month data also revealed that there were no treatment-related deaths, and treatment-related adverse events led to discontinuation in only two out of 46 evaluable patients. However, 63% of patients experienced a grade 3 or higher adverse event, with diarrhea being the most common, affecting 35% of patients. According to Iannone, the safety and tolerability profile of zanidatamab combined with chemotherapy has remained manageable, and no new safety signals have been identified compared to previous analyses.

Jazz Pharmaceuticals is continuing patient enrollment for a phase 3 trial of zanidatamab combined with chemotherapy and BeiGene’s Tevimbra as a first-line treatment for HER2-positive mGEA. The company anticipates topline results in the second quarter of 2025. Additionally, Jazz is awaiting the FDA’s decision on approving zanidatamab for treating previously treated, unresectable, locally advanced or metastatic HER2-positive biliary tract cancer. If approved in November, the Zymeworks-partnered bispecific antibody would become the first HER2-targeted treatment specifically for this indication.