Zanidatamab Trial Marks Major Advance in Treatment of Metastatic Breast Cancer

Jazz Pharmaceuticals' Phase 2a trial of zanidatamab, presented at SABCS 2023, shows promising results in treating HER2+/HR+ metastatic breast cancer. The trial, demonstrated a 67% progression-free survival rate at six months with a combination of zanidatamab, palbociclib, and fulvestrant, offering potential for a new, effective chemotherapy-free treatment option.

In a pivotal development for breast cancer treatment, Jazz Pharmaceuticals' recent Phase 2a trial results, unveiled at the 2023 San Antonio Breast Cancer Symposium (SABCS), highlight the efficacy of zanidatamab. This innovative HER2-targeted bispecific antibody, when combined with palbociclib and fulvestrant, achieved a 67% progression-free survival at 6 months and a median of 12 months in patients with advanced HER2+/HR+ metastatic breast cancer. The data from the trial suggest a potential shift towards chemotherapy-free treatments in this area.

Implications for Patients

Dr. Santiago Escrivá-de-Romani, the primary trial investigator at VH Institute of Oncology, emphasizes significance of this therapy, stating, 

"Metastatic breast cancer is a particularly aggressive and devastating disease, and patients whose cancer has progressed despite numerous therapeutic interventions are in dire need of additional treatment options – particularly chemotherapy-free options. Targeting both the HER2 and hormone receptor pathways can be a promising approach for applicable patients, and the durable responses seen in this study signal the potential for this combination to fill a persistent and much needed treatment gap among these patients."

Trial Highlights

The trial involved 51 patients with HER2+/HR+ mBC, all of whom had undergone multiple prior treatments. Remarkably, the combination of zanidatamab, palbociclib, and fulvestrant achieved a 67% progression-free survival rate at six months, with a median progression-free survival of 12 months. The objective response rate stood at 35%, and the duration of response averaged 15 months, highlighting the treatment's potential to provide a durable reprieve from this aggressive cancer.

"We are encouraged by the meaningful clinical benefit seen in this trial, and we look forward to continuing to advance our broader clinical development program for zanidatamab in breast cancer and other HER2-expressing solid tumors, with the goal of addressing some of the greatest unmet needs in cancer with HER2 expression," said Dr. Rob Iannone, Executive Vice President of Jazz Pharmaceuticals.

The Science Behind Zanidatamab

Zanidatamab targets two different areas of the HER2 protein, a unique approach that enhances its ability to combat tumor cells. This dual targeting not only blocks HER2 signaling but also promotes the removal of HER2 from cell surfaces and triggers immune-mediated destruction of cancer cells.

Regulatory Recognition

Recognizing its potential, the U.S. Food and Drug Administration (FDA) has granted zanidatamab several designations aimed at expediting its development, including Breakthrough Therapy designation for certain cancers and Fast Track designations for others. These recognitions underscore the importance of this therapy in addressing unmet needs in cancer treatment. The results from the Phase 2a trial of zanidatamab are not just statistics; they represent a beacon of hope for those battling HER2+/HR+ mBC.