Puma Biotechnology, Inc. (NASDAQ:PBYI), a biopharmaceutical company, announced that the results of the Phase II TBCRC041 randomized clinical trial of alisertib alone or in combination with fulvestrant in patients with endocrine-resistant advanced breast cancer have been published online in JAMA Oncology. Alisertib is an adenosine triphosphate–competitive and reversible inhibitor of aurora kinase A and results in disruption of mitosis leading to apoptosis of rapidly proliferating tumor cells that are dependent on aurora kinase A.
The Phase II randomized clinical trial was conducted through the Translational Breast Cancer Research Consortium. The trial enrolled postmenopausal women with endocrine-resistant, HER2–negative metastatic breast cancer who were previously treated with fulvestrant. For the 91 evaluable patients, baseline characteristics were well-balanced between the two arms of the trial; however, more patients in the alisertib plus fulvestrant arm had been previously treated with chemotherapy in the metastatic setting (47.8% in the alisertib alone arm, 68.9% in the alisertib plus fulvestrant arm). 100% of the patients in each arm of the trial were previously treated with CDK 4/6 inhibitors. 37% of the patients in the alisertib alone arm and 57.8% of patients in the alisertib plus fulvestrant arm were previously treated with everolimus.
The efficacy results from the trial showed that for the 46 evaluable patients in the alisertib alone arm of the trial nine partial responses were seen, resulting in an overall response rate of 19.6%. The median duration of response was 15.1 months, and the 24-week clinical benefit rate was 41.3%. The median progression-free survival (PFS) was estimated to be 5.6 months. For the 45 evaluable patients in the alisertib plus fulvestrant arm of the trial, nine patients experienced a response, resulting in an overall response rate of 20.0%. These responses consisted of one patient with a complete response and 8 patients with partial responses. The median duration of response was 8.5 months, and the 24-week clinical benefit rate was 28.9%. The estimated median PFS was 5.4 months.
In the alisertib alone arm of the trial, the most common grade 3 or higher adverse events were neutropenia (43.4%), leukopenia (17.4%), and anemia (19.6%). In the alisertib plus fulvestrant arm of the trial, the most common grade 3 or higher adverse events were neutropenia (42.2%), leukopenia (31.1%), lymphopenia (15.6%), fatigue (11.1%), and anemia (8.9%).
“Although there have been new drugs approved for the treatment of ER-positive HER2-negative metastatic breast cancer, there continues to be a need for new drugs and drugs that specifically address patients who have been previously treated with CDK 4/6 inhibitors,” said Tufia C. Haddad, MD, Associate Professor of Oncology at the Mayo Clinic College of Medicine and co-leader of Platform and Digital Innovation, Mayo Clinic Comprehensive Cancer Center. “This Phase II randomized clinical trial demonstrated that alisertib is among the first investigational targeted therapies demonstrating promising clinical activity and a tolerable safety profile in the setting of endocrine and CDK 4/6 inhibitor resistant metastatic breast cancer. We look forward to the continued development of alisertib in this patient population.”
“We are very pleased with the results from the TBCRC041 trial demonstrating the efficacy of alisertib in patients with ER-positive HER2-negative metastatic breast cancer. Alisertib’s unique mechanism of action is well suited to address the mechanisms of CDK 4/6 resistance that are targetable with an aurora kinase inhibitor,” said Alan H. Auerbach, Chairman, Chief Executive Officer and President of Puma. “We greatly look forward to advancing alisertib into additional clinical trials for ER-positive HER2-negative breast cancer.”