according to results from a phase 1b trial.
“The purpose of this study was to determine the safety and preliminary efficacy of the combination in patients previously treated with trastuzumab plus pertuzumab,” wrote Jame Abraham, MD, of the Cleveland Clinic and colleagues in the Journal of Clinical Oncology.
The open-label, dose-escalation study included 27 women with HER2-positive metastatic breast cancer who had hormone receptor–positive or hormone receptor–negative disease. All participants had demonstrated disease progression, despite prior treatment with combination pertuzumab and trastuzumab, plus a taxane. Among 19 response-evaluable patients, 12 patients (63%) had an objective response. Responses were observed across all neratinib doses, including a complete response in three patients, and partial response in nine patients.
“Deep and more durable responses occurred in patients with cell-free DNA ERBB2 amplification,” Dr. Abraham and associates noted.
“Alterations in the expression of specific HER2 species in ERBB2-amplified cancers, including p95HER2, may have therapeutic implications and require further investigation,” they wrote.
With respect to neratinib dosing, the initial cohort was started at 120 mg daily, which was increased to 240 mg daily in successive cohorts using a 3+3 design. T-DM1 was administered every 3 weeks at 3.6 mg/kg.
After analysis, the researchers proposed a phase 2 dose of neratinib 160 mg once daily and T-DM1 3.6 mg/kg for the combination.
Dose-limiting grade 3 diarrhea was reported in a total of six patients, which was most pronounced in cycle 1. At the phase 2 recommended dose of neratinib, 7 of 10 patients had early-onset diarrhea, which resolved within 24 hours. No grade 4-5 diarrheal toxicities were reported.
Other grade 3-4 adverse events observed were electrolyte abnormalities, thrombocytopenia, nausea, and dehydration.
Phase 2 studies are currently ongoing in order to better characterize the activity of combination T-DM1 and neratinib.
The study was funded by PUMA Biotechnology and the University of Pittsburgh. The authors reported financial affiliations with AstraZeneca, Eisai, Genentech, Guardant Health, Pfizer, Roche, Seattle Genetics, and several others.
SOURCE: Abraham J et al. J Clin Oncol. 2019 Aug 23. doi: 10.1200/JCO.19.00858.