Primary results of LORELEI

Primary results of LORELEI: a phase II randomized, double-blind study of neoadjuvant letrozole plus taselisib versus letrozole plus placebo in postmenopausal patients with ER+/HER2-negative early breast cancer (EBC) [LBA10_PR]

Dr. Cristina Saura, et al reported that the addition of taselisib to letrozole increased the ORR in the overall population and in patients with PIK3CA-mutant ER+/HER2-negative early breast cancer.

  • ORR in the overall population: 50.0% taselisib (N=166) vs 39.3% placebo (N=168) (p=0.049)
  • ORR in patients with PIK3CA-mutant tumours: 56.2% taselisib (N=73) vs 38.0% placebo (N=79) (p=0.033)
  • Most common grade 3-4 adverse events in the taselisib arm:
    • gastrointestinal disorders (7.8%),
    • infections (4.8%), and
    • skin/subcutaneous tissue disorders (4.8%).
  • Taselisib discontinuation (10.8%) and dose reductions (11.4%) were infrequent.

LORELEI is the first randomised study to demonstrate a significant increase in ORR, measured by centrally assessed MRI, upon treatment with a PI3K-selective inhibitor plus endocrine therapy in ER+/HER2-negative EBC. As in previous studies, the treatment effect appeared to be more pronounced in patients with PIK3CA-mutant tumours.

Taselisib is an investigational PI3K inhibitor currently being studied for its potential to selectively inhibit the PI3Kα isoform.  For more information, please visit:

Cheng Siu Fung
Manager, Medical Affairs
Breast Franchise