US-based Merrimack Pharmaceuticals has started the Phase II HERMIONE trial of MM-302, a HER2-targeted nanoliposomal encapsulation of doxorubicin, in combination with trastuzumab (Herceptin) to treat patients with HER2-positive locally advanced or metastatic breast cancer.
The global, open-label, randomised trial incorporates inputs from the US Food and Drug Administration (FDA) to support a potential accelerated approval application.
MM-302 is the company's new antibody-drug conjugated liposomal doxorubicin that targets and binds to HER2, a protein that when overexpressed can lead to the development and aggressive progression of breast cancer.
Merrimack Development vice-president and MM-302 project team leader Thomas Wickham said: "While there have been new therapies approved in the HER2-positive setting, there is no standard of care for patients whose cancer progresses despite treatment with trastuzumab, T-DM1 and pertuzumab.
"In our experience to date, MM-302 has shown promising clinical activity and an acceptable safety profile in patients with metastatic breast cancer who have progressed on HER2-directed therapies.
"We are moving this trial forward with a goal of transforming the standard of care for this population."
The company is pursuing the Phase II trial based on positive results from an ongoing Phase I trial showing a median progression-free survival (PFS) benefit of 5.7 months in a heavily pretreated population of 47 patients receiving a therapeutic dose of MM-302 (30mg/m² or greater) alone or in combination with trastuzumab.
About 250 patients will be enrolled in the HERMIONE trial and they will be randomised (1:1) to receive either MM-302 and trastuzumab (Herceptin) or chemotherapy of their physician's choice (capecitabine, gemcitabine or vinorelbine) and trastuzumab.
According to the company, eligible patients for the HERMIONE trial must have received prior treatment with trastuzumab in any setting, and pertuzumab (Perjeta) and ado-trastuzumab emtansine (T-DM1, Kadcyla) in the locally advanced or metastatic setting, but have not been treated with an anthracycline-based regimen.
The trial's primary endpoint is PFS and secondary endpoints include overall survival, objective response rate, safety and tolerability.
The company intends to carry out the trial at about 60 sites in the US, Canada and Western Europe, and initial trial sites are now open to screen patients in the US.