Phase I study of LZM005 in patients with HER2-positive metastatic breast cancer

The prognosis of human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer (MBC) remained unsatisfactory currently, more anti-HER2 agents are needed. Here we report a phase I study that evaluated the safety, activity, and biomarkers of LZM005, a HER2 antibody, used as a monotherapy or in combination with trastuzumab plus docetaxel in patients with HER2-positive MBC. From October 2017 to December 2019, 34 patients received LZM005 (14 monotherapy, 20 combination therapy). No DLT was observed. The common adverse events (AEs) in phase Ia included diarrhea (21.4%), infusion reaction (21.4%), and hypertriglyceridemia (21.4%), while those in phase Ib were leukopenia (85.0%), neutropenia (75.0%), anemia (60.0%), diarrhea (60.0%), and rash/pruritus (50.0%). All AEs were manageable. In phase Ia, partial response (PR) was achieved in one case (1/14, overall response rate [ORR]: 7.1%); the disease control rate was 42.90% (6/14). In phase Ib, 11 patients (55.0%) achieved PR, and eight (40.0%) had stable disease. The ORR was 100% (6/6) in trastuzumab-naive and 35.7% (5/14) in trastuzumab-pretreated patients. Biomarker analysis showed that chromatin remodeling genes KMT2B and BRWD1 were associated with better progression-free survival. LZM005 is well tolerated and shows potent activity in patients with HER2-positive MBC.