Newly-Approved Drug for HR+, HER2- PI3K Mutant MBC

Bestbird

Some good news about a drug that was just approved in the US (hopefully other countries to follow)!

The PI3K (or PIK3CA) mutation is frequently found in metastatic breast cancer tumors, and it can be diagnosed via a liquid biopsy or a tumor biopsy.

Until recently, there has not been an approved therapy targeting this mutation.  The good news is that Alpelisib, an oral PI3K inhibitor, was FDA-approved in May 2019 for the treatment of postmenopausal women (and men) with HR-positive, HER2-negative, PIK3CA-mutated MBC following progression on or after a hormonal therapy regimen. 

Alpelisib's approval was based upon the SOLAR-1 Phase 3 clinical trial which compared Faslodex plus Alpelisib versus Faslodex plus placebo in postmenopausal patients with PIK3CA mutations that were found via liquid or tumor biopsy.  Patients in the Faslodex/Alpelisib arm fared substantially better (median PFS 11.0 months) than similar patients in the Faslodex plus placebo arm (median PFS 5.7 months). Patients in this trial had received 1 or more lines of prior hormonal therapy but no chemotherapy.  The Overall Response Rate in the PIK3CA-mutant cohort was 26.6% in the Faslodex/Alpelisib arm compared with 12.8% in the Faslodex/placebo arm. These results, assessed after a median follow-up of 20 months, translated into a 35% reduction in the risk of progression or death in favor of Faslodex/Alpelisib arm.  (There was no advantage to providing Alpelisib in patients without a PIK3CA mutation). 

The FDA has also  approved the companion diagnostic test “Therascreen PIK3CA RGQ PCR Kit” to detect the PIK3CA mutation in a tissue and/or a liquid biopsy. Patients whose results are negative by the Therascreen test using the liquid biopsy are encouraged to undergo tumor biopsy for PIK3CA mutation testing. From: https://www.targetedonc.com/news/alpelisib-receives-fda-approval-in-breast-cancer and https://www.fda.gov/news-events/press-announcements/fda-approves-first-pi3k-inhibitor-breast-cancer

As an aside, this and other information can be found in my book, "The Insider's Guide to Metastatic Breast Cancer" which is also available in a complimentary .pdf.  For more information, please visit: https://www.insidersguidembc.com/about

With good wishes!