A phase I study of MM-302, a HER2-targeted liposomal doxorubicin, in patients with advanced, HER2-positive (HER2+) breast cancer.

Abstract

TPS663 Background: Anthracyclines have been an effective backbone of breast cancer therapies for decades. However, cardiotoxicity issues associated with free anthracyclines have limited their effective use in the clinic and led to the exploration of anthracycline-free regimens, particularly with HER2-positive cancers that require treatment with another cardiotoxic agent, trastuzumab. While liposomal doxorubicin formulations have succeeded in reducing cardiotoxicity, they have failed to demonstrate clear-cut efficacy advantages and can involve other toxicities. To address the safety and efficacy limitations of currently available anthracyclines, we have designed a new liposomal formulation, MM-302, that targets doxorubicin to HER2-overexpressing tumor cells. Antibody fragments that bind to HER2 without blocking HER2-mediated signaling are coupled to the outer surface of pegylated liposomal doxorubicin. MM-302 specifically binds and enters tumor cells overexpressing HER2 with minimal uptake into normal cells such as cardiomyocytes which express low levels of HER2. This first-in-human phase I study evaluates the safety of MM-302 in patients and provides preliminary efficacy data in HER-2+ advanced breast cancer (ABC). Methods: Patients aged > 18 years with histologically confirmed HER-2+ advanced breast cancer that have progressed or recurred on standard therapy or for which no standard therapy exists who have adequate performance status, bone marrow reserve, and organ function, are eligible for the study. Following a standard 3 + 3 dose escalation design, the maximum tolerated dose (MTD) or maximum feasible dose (MFD) is determined and up to 25 additional patients with HER-2+ ABC will be enrolled for a planned total of 40-49 patients. The primary endpoint is determination of the MTD/MFD. Secondary endpoints include determination of dose-limiting toxicity, adverse event(s), and pharmacokinetic and immunogenicity profiles of MM-302, as well as overall response and clinical benefit rates of MM-302. MM-302 is administered intravenously weekly in 4-week cycles. At the time of this submission, 8 patients have been enrolled in the dose escalation portion.