Taselisib is an oral, selective PI3K inhibitor with enhanced activity against PIK3CA-mutant cancer cells.
Adding taselisib to letrozole in the neoadjuvant setting increased objective responses among patients with estrogen receptor (ER)-positive, HER2-negative, metastatic breast cancer (phase 2 LORELEI clinical trial).
Patients were randomized to receive letrozole 2.5 mg daily plus taselisib 4 mg or placebo on a 5-day with treatment, 2-day without schedule for 16 weeks followed by surgery.
Taselisib added to letrozole therapy was associated with a higher rate of objective responses than placebo (50% vs 39%, respectively.
Serious adverse events were more common with taselisib than with placebo, and 1 patient died in the taselisib arm, although the death was not deemed to be treatment-related.