Jazz Pharmaceuticals Presents Updated Phase 2 Data for Zanidatamab Demonstrating Increased mPFS in HER2-Positive Metastatic Gastroesophageal Adenocarcinoma at ESMO 2024

Phase 2 updated results for zanidatamab in HER2-positive mGEA included a confirmed objective response rate (cORR) of 84%, duration of response (DoR) of 18.7 months, median progression-free survival (mPFS) of 15.2 months and a Kaplan-Meier–estimated overall survival (OS) of 59% at 30 months

DUBLIN, Sept. 16, 2024 /PRNewswire/ -- Jazz Pharmaceuticals plc (Nasdaq: JAZZ) today announced updated data, including median progression-free survival (mPFS) and overall survival (OS) findings, from the Phase 2 trial of zanidatamab, an investigational dual HER2-targeted bispecific antibody, in combination with chemotherapy as first-line treatment for patients with HER2-expressing advanced or metastatic gastroesophageal adenocarcinoma (mGEA).

Data from 41 patients with HER2-positive mGEA who were treated with zanidatamab in combination with physician's choice of chemotherapy treatment demonstrated a mPFS of 15.2 [95% CI: 9.5, 33.4] months. After a median duration of follow-up of 41.5 (range, 23.0-52.7) months, the median OS was not mature, a Kaplan-Meier–estimated 24-month OS was 65% [95% CI: 48.0, 78.0] and the 30-month overall survival was 59% [95% CI: 41.0, 73.0].

"Gastroesophageal adenocarcinoma (GEA) represents one of the most common tumor types worldwide; however, developing effective treatment options for GEA patients has been challenging," said Dr. Elena Elimova, lead trial investigator and a medical oncologist at Princess Margaret Cancer Centre, Toronto, Canada. "Despite recent advancements for patients, the sustained clinical antitumor activity seen in this trial demonstrates the potential for zanidatamab to address a significant unmet patient need in HER2-positive GEA."

"The updated results from this Phase 2 trial 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," said Rob Iannone, M.D., M.S.C.E., executive vice president, global head of research and development, and chief medical officer of Jazz Pharmaceuticals. "We look forward to continuing to advance our broader clinical development program for zanidatamab in GEA, including the Phase 3 first-line clinical trial HERIZON-GEA-01 that is expected to read out in the second quarter of 2025, and other HER2-expressing solid tumors, with the goal of supporting more patients with HER2-positive cancers."

Phase 2 mGEA Trial ResultsThe data include efficacy and tolerability findings from an ongoing, open-label Phase 2 study (NCT03929666) evaluating zanidatamab in combination with chemotherapy as first-line treatment for patients with HER2-expressing mGEA, which comprises gastric, esophageal and gastroesophageal junction (GEJ) adenocarcinomas. Patients had not received prior HER2-targeted agents nor systemic treatment for mGEA. A total of 46 patients with HER2-expressing mGEA (41 patients with HER2-positive mGEA) were enrolled from 15 sites across the United States, Canada and South Korea, and patients were administered zanidatamab with physician's choice of chemotherapy treatment. Currently, chemotherapy-based regimens are the standard first-line combination therapy for 1L mGEA. 

The longer-term data (median duration of follow-up of 41.5 [range, 23.0-52.7] months) demonstrates the promising antitumor activity of zanidamatab combined with chemotherapy as a first-line therapy for HER2-positive mGEA.

• Treatment with zanidatamab resulted in a cORR of 84% [95% CI: 68.0, 94.0], an increase of 5% from the cORR previously reported, and one additional patient achieved a complete response for a total of four patients achieving complete response among 37-response evaluable patients.
• The median duration of response was 18.7 months [95% CI: 8.3-NE] with 10 patients having an ongoing response at the time of data cutoff.
• The mPFS was 15.2 [95% CI: 9.5, 33.4] months.
• The Kaplan-Meier–estimated 24-month OS was 65% [95% CI: 48.0, 78.0] with a 30-month overall survival of 59% [95% CI: 41.0, 73.0].

With additional follow-up, the safety and tolerability profile of zanidatamab plus chemotherapy remained manageable with no new safety signals identified. Diarrhea was the most common Grade 3-4 treatment-related adverse events (TRAEs) (35%); the incidence of Grade 3-4 diarrhea was