Enhertu Granted Breakthrough Therapy Designation for Unresectable/Metastatic Breast Cancer Treatment

The Food and Drug Administration (FDA) granted a breakthrough therapy designation to Enhertu (trastuzumab deruxtecan) for the treatment of certain patients with unresectable or metastatic breast cancer.

The breakthrough therapy designation, which will speed up the development and FDA’s review of the drug, is for adults who have unresectable or metastatic HER2-low breast cancer who underwent prior systemic therapy for metastatic disease or who experience recurrence during or within six months of finishing adjuvant (post-surgical) chemotherapy. If patients have hormone receptor- (HR) positive disease, they need to have received or be ineligible for endocrine therapy to be treated with Enhertu.

The FDA based its decision on findings from the global, randomized phase 3 DESTINY-Breast04 clinical trial, which compared Enhertu with physician’s choice of chemotherapy (capecitabine, eribulin, gemcitabine, paclitaxel or nab-paclitaxel) in patients with HR-positive, HR-negative and HER2-low unresectable and/or metastatic breast cancer who had previously undergone one or two prior lines of chemotherapy.

The main goal of DESTINY-Breast04 was to see if Enhertu bested chemotherapy when it came to progression-free survival (time from treatment until disease worsens) in patients with HR-positive, HER2-low metastatic breast cancer. The secondary goal was to see if progression-free survival could be improved in HER2-low metastatic breast cancer, regardless of HR status, as well as overall survival.

“Historically, only patients with HER2-positive metastatic breast cancer were shown to benefit from HER2-directed therapy. DESTINY-Breast04, in which Enhertu showed a clinically meaningful survival benefit in patients with HER2-low metastatic breast cancer, is the first trial to demonstrate that selecting patients for treatment based on low expression of HER2 has the potential to change the diagnostic and treatment paradigms for these patients,” said Ken Takeshita, global head, R&D, Daiichi Sankyo, one of the pharmaceutical companies that is developing Enhertu, along with AstraZeneca, in a press release.

The release cited the positive high-level results seen from DESTINY-Breast04, which showed that Enhertu led to a meaningful improvement in progression-free survival and overall survival in patients with HER2-low unresectable and/or metastatic breast cancer in all randomized patients with HR-positive and HR-negative disease. Additionally, there were no new side effects that were observed from the drug.

More detailed data from DESTINY-Breast04 will be presented at an upcoming medical meeting, according to the release.

Chemotherapy is the only treatment that is currently available for patients with HR-positive disease who progressed on hormone therapy, and there are few targeted treatments available for those with HR-negative breast cancer, highlighting the unmet need that Enhertu could potentially fill.

“Enhertu continues to show transformative potential, and this milestone represents an important advance for patients with HER2-low metastatic breast cancer who are in urgent need of new treatment options and better outcomes,” Susan Galbraith, executive vice president, Oncology R&D, AstraZeneca said in the release.

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