On December 9, 2020 Puma Biotechnology, Inc. (Nasdaq: PBYI), a biopharmaceutical company, reported that updated results from the ongoing Phase II SUMMIT trial of neratinib at the 2020 Virtual San Antonio Breast Cancer Symposium (SABCS) that is currently taking place (Press release, Puma Biotechnology, DEC 9, 2020, View Source [SID1234572543]). The presentation entitled, "Latest findings from the breast cancer cohort in SUMMIT – a phase 2 ‘basket’ trial of neratinib + trastuzumab + fulvestrant for HER2-mutant, hormone receptor-positive, metastatic breast cancer," is being presented at a Spotlight Poster Discussion Session by Komal Jhaveri, M.D., FACP, Memorial Sloan Kettering Cancer Center, an investigator of the trial. A copy of this poster presentation is available on the Puma website.

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The Phase II SUMMIT basket trial is an open-label, multicenter, multinational study to evaluate the safety and efficacy of neratinib administered daily to patients who have solid tumors with activating HER2 (ERBB2) or lung cancers with EGFR exon 18 mutations (NCT01953926). In the HER2-mutant, hormone receptor (HR)-positive breast cancer cohort, 51 patients received 240 mg of neratinib daily in combination with trastuzumab and fulvestrant. In this cohort, patients had received a median of 4 prior lines of therapy in the metastatic setting (range 1-10 prior regimens) before entering the trial. 36 patients (70.6%) had received prior fulvestrant, 35 patients (68.6%) had received prior aromatase inhibitor and 4 patients (7.8%) had received prior tamoxifen. Further, 30 patients (58.8%) received prior cyclin-dependent kinase 4/6-inhibitor (CDK4/6i) therapy. Thirty-five patients (68.6%) had received prior chemotherapy.

The interim efficacy summary of the breast cohort that received neratinib in combination with trastuzumab and fulvestrant showed that for the 37 RECIST efficacy evaluable patients, 17 patients (45.9%) experienced a confirmed objective response, including one complete response (2.7%) and 16 (43.2%) partial responses, and 20 patients (54.1%) experienced clinical benefit (clinical benefit is defined as confirmed complete response or partial response or stable disease for at least 24 weeks). The median duration of response was 10.9 months and the median progression-free survival was 8.3 months.

The safety profile observed in patients treated with the combination of neratinib plus trastuzumab plus fulvestrant in the SUMMIT study was consistent with that observed previously in metastatic patients with HER2 amplified tumors. All patients received anti-diarrheal prophylaxis with loperamide alone. The interim safety results of the study showed that the most frequently observed adverse event was diarrhea. For the 51 safety evaluable patients enrolled in this cohort, 20 patients (39.2%) reported grade 3 diarrhea. The median duration of grade 3 diarrhea for those patients was 6 days. No patient permanently discontinued neratinib due to diarrhea.

Komal Jhaveri, M.D., FACP, Memorial Sloan Kettering Cancer Center, Clinical Director of the Early Drug Development Service and Assistant Professor of Medicine, Weill Cornell Medical College, said, "HER2 mutations appear to be oncogenic drivers in a subset of metastatic breast cancers and are clinically actionable. The combination of neratinib + trastuzumab + fulvestrant therapy demonstrates encouraging clinical activity with durable responses in this molecular-defined patient population with clinical benefit observed in patients who have previously been treated after standard of care CDK4/6i and endocrine therapies."

Alan H. Auerbach, CEO and President of Puma Biotechnology, added, "We are pleased to see that the combination of neratinib + fulvestrant + trastuzumab continues to demonstrate encouraging clinical activity in this heavily pre-treated cohort. We are continuing to enroll the randomized cohorts in the SUMMIT trial of neratinib in hormone receptor positive breast cancer patients with HER2 mutations and we anticipate the completion of this enrollment in the first half of 2021."