Zai Lab Limited’s partner MacroGenics, Inc., a biopharmaceutical company focused on developing and commercializing innovative monoclonal-antibody-based therapeutics for the treatment of cancer, announced that the U.S. Food and Drug Administration (FDA) has approved MARGENZA, in combination with chemotherapy, for the treatment of adult patients with metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease. MARGENZA is being further developed by MacroGenics for the treatment of advanced gastric cancer, with support by Zai Lab in Greater China. The approval in breast cancer in the U.S. was based on safety and efficacy results from the pivotal Phase 3 SOPHIA trial.

“We congratulate our partner MacroGenics for this great success,” said Samantha Du, PhD., Founder, Chairwoman and Chief Executive Officer of Zai Lab. “We look forward to bringing this important medicine to metastatic breast cancer patients in China as soon as possible. We are also participating in the global Phase 2/3 MAHOGANY clinical trial of margetuximab plus checkpoint blockade, with or without chemotherapy, as a potential first-line treatment for patients in front-line gastroesophageal cancer.”

The approval for MARGENZA was based on data from SOPHIA, a randomized Phase 3 clinical trial. The study, which included 536 patients, showed a statistically significant 24% reduction in the risk of disease progression or death with MARGENZA plus chemotherapy compared with trastuzumab plus chemotherapy (hazard ratio [HR]=0.76; 95% CI, 0.59-0.98; P=0.033; median PFS 5.8 vs 4.9 months). The objective response rate for MARGENZA plus chemotherapy was 22% and for trastuzumab plus chemotherapy was 16%. The final Overall Survival (OS) analysis is expected in the second half of 2021.

Adverse reactions occurring in greater than twenty percent of patients with MARGENZA in combination with chemotherapy were fatigue/asthenia (57%), nausea (33%), diarrhea (25%), and vomiting (21%). The MARGENZA U.S. Prescribing Information has a BOXED WARNING for left ventricular dysfunction and embryo-fetal toxicity. In addition, MARGENZA can cause infusion-related reactions (IRRs). IRRs occurred in 13% of patients treated with MARGENZA, with the majority reported as Grade 2 or less. Grade 3 IRRs occurred in 1.5% of patients.

The SOPHIA study is a randomized, open-label Phase 3 clinical trial evaluating MARGENZA plus chemotherapy compared to trastuzumab plus chemotherapy in patients with HER2-positive metastatic breast cancer, who have previously been treated with anti-HER2-targeted therapies. All study patients had previously received trastuzumab, all but one patient had previously received pertuzumab, and 91% had previously received ado-trastuzumab emtansine, or T-DM1.

The study enrolled 536 patients who were randomized 1:1 to receive either MARGENZA (n=266) given intravenously at 15 mg/kg every three weeks or trastuzumab (n=270) given intravenously at 6 mg/kg (or 8 mg/kg for loading dose) every three weeks in combination with one of four chemotherapy agents (capecitabine, eribulin, gemcitabine or vinorelbine) given at the standard doses. Intent-to-treat PFS analysis occurred after 265 PFS events.

The primary endpoints of the study are sequentially assessed PFS, determined by blinded, centrally reviewed radiological review, followed by OS. Additional key secondary endpoints are PFS by investigator assessment, ORR and Duration of Response. Tertiary endpoints include ORR by investigator assessment and safety. PFS and ORR were assessed according to Response Evaluation Criteria in Solid Tumours version.