Jazz Pharmaceuticals has posted fresh phase 2 data on zanidatamab that show the HER2-targeted bispecific antibody kept 59% of people with metastatic gastroesophageal cancer (mGEA) alive for at least 30 months when given in combination with chemotherapy.
The latest data cut, which Jazz presented at the European Society for Medical Oncology conference in Barcelon, Spain on Monday morning, follows the release of 18-month data from the same phase 2 trial at the start of 2023. At that timestamp, the overall survival (OS) rate was 84%.
Jazz’s Global Head of R&D Robert Iannone, M.D., told Fierce Biotech ahead of ESMO that today’s updated results “reaffirm zanidatamab’s potential as a foundational treatment for patients with HER2-positive mGEA and showcase the promise of this HER2-targeted bispecific antibody to treat HER2-expressing cancers.”
The 30-month data unveiled at ESMO gave other insights into zanidatamab’s efficacy, including a confirmed objective response rate (cORR) of 84%, which Iannone noted was a 5% increase on the 79% cORR reported in the 18-month data last year.
Today’s data also showed a median duration of response (DoR) of 18.7 months and median progression-free survival (PFS) of 15.2 months. One additional patient achieved a complete response since the 18-month readout, bringing the total number of patients who achieved this to four out of 37 response-evaluable patients.
When asked by Fierce how this data lines up against other oncology players, Iannone said he can’t draw direct comparisons as Jazz hasn’t placed zanidatamab in head-to-head trials against other cancer treatments.
“However, we think the data with ORR, DoR, PFS and OS compare favorably with what would be expected for the front-line standard of care with Herceptin [plus] chemotherapy,” he told Fierce.
The potential to treat GEA by targeting HER2 was confirmed in 2010 when researchers showed that adding Roche’s Herceptin to chemotherapy extended OS from 11.1 months to 13.8 months.
There were no treatment-related deaths in today’s 30-month data and discontinuations due to treatment-related adverse events affected two out of 46 evaluable patients. A total of 63% of patients experienced an adverse event of grade 3 or above, with diarrhea being the most common, affecting 35% of patients.
“With additional follow-up, the safety and tolerability profile of zanidatamab plus chemotherapy in all patients assessed remained manageable with no new safety signals identified compared to the previous analysis,” Iannone said.
The biotech is continuing to enroll patients in a phase 3 trial of zanidatamab in combinations with chemotherapy and BeiGene’s Tevimbra as a first-line treatment for HER2-positive mGEA. A topline readout is expected in the second quarter of 2025.
In the meantime, Jazz is awaiting the FDA’s decision on the approval of zanidatamab to treat previously treated, unresectable, locally advanced or metastatic HER2-positive biliary tract cancer. If the regulator gives the nod in November, the Zymeworks-partnered bispecific antibody would be the first HER2-targeted treatment specifically for the indication.