Puma Biotechnology, Inc. announced the presentation of biomarker findings from a Phase II study of alisertib plus paclitaxel versus paclitaxel alone (Clinicatrials.gov identifier NCT02187991) in metastatic hormone receptor positive (HR+) and triple negative (TN) breast cancer at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting held June 2-6 in Chicago and online. The Phase II trial was conducted through The US Oncology Network. The results of this trial were published by Joyce O'Shaughnessy et al.

(Jama Network Open, April 2021) and showed that the addition of alisertib to paclitaxel improved progression-free survival (PFS) among enrolled patients compared with paclitaxel alone (HR, 0.56; 95%CI, 0.37-0.84; P = 0.005). The poster (Abstract #1037, poster #258), entitled, “Association of C-MYC, MYC target gene, and unfolded protein response (UPR) expression with clinical benefit from the oral aurora kinase A (AURKA) inhibitor, alisertib (A), in combination with paclitaxel (P) compared with P alone in patients (Pts) with HER2-negative metastatic breast cancer (MBC),” was presented at the Breast Cancer – MetastaticPoster Session by Sara A. Byron, Ph.D., Integrated Cancer Genomics Division, Translational Genomics Research Institute (TGen), part of City of Hope, on June 4. A copy of the poster is available on the Puma Biotechnology website. Archival tissue samples from patients enrolled in the clinical study were analyzed at TGen.

Of the 140 patients enrolled in the trial, 45 from the alisertib plus paclitaxel arm and 51 from the paclitaxel arm had sufficient tissue available for next generation sequencing, and 31 from the alisertib plus paclitaxel arm and 35 from the paclitaxel arm had enough for RNA sequencing/gene set enrichment analysis. The most frequently mutated genes were PIK3CA (45%) and TP53 (44%). No mutations were significantly associated with response or resistance to alisertib plus paclitaxel, including those in PIK3CA, TP53, AKT1, HER2, and CDH1.

Increased MYC RNA expression was observed in tumors from patients who did not derive clinical benefit from paclitaxel alone (defined as PFS less than 6 months) compared to those with benefit from paclitaxel alone (defined as PFS greater than or equal to 6 months). Increased MYC RNA expression was not observed in patients who did not appear to benefit from alisertib plus paclitaxel. Elevated expression of genes involved in MYC activation and in unfolded protein response (a pro-survival mechanism) were enriched in alisertib plus paclitaxel responders compared to paclitaxel responders and were associated with poor response to paclitaxel alone.

In 12 patients with exceptional response to alisertib plus paclitaxel (defined as PFS greater than or equal to 12 months), increased expression of genes involved in MYC activation and in epithelial to mesenchymal transition (a hallmark of cancer progression and metastasis) was observed in comparison to cancers from patients whose disease progressed within 6 months of initiating alisertib + paclitaxel (n=11) or those with exceptional response to paclitaxel alone (n=4).