Neoadjuvant buparlisib plus trastuzumab and paclitaxel for women with HER2+ primary breast cancer: A randomised, double-blind, placebo-controlled phase II trial (NeoPHOEBE)

Abstract

Aim: The Neoadjuvant PI3K inhibition in HER2 OverExpressing Breast cancEr (NeoPHOEBE) trial evaluated the efficacy and safety of buparlisib, a pan-phosphatidylinositol 3-kinase (PI3K) inhibitor, plus trastuzumab and paclitaxel as neoadjuvant treatment for human epidermal growth factor receptor-2 positive (HER2+) breast cancer.

Methods: NeoPHOEBE was a neoadjuvant, phase II, randomised, double-blind study. Women with HER2+ breast cancer were randomised within two independent cohorts by PIK3CA mutation status and, in each cohort stratified by oestrogen receptor (ER) status to receive buparlisib or placebo plus trastuzumab (first 6 weeks) followed by buparlisib or placebo with trastuzumab and paclitaxel. Primary end-point was pathological complete response (pCR) rate; key secondary end-point was objective response rate (ORR) at 6 weeks. Exploratory end-points were evaluation of Ki67 levels and change in tumour infiltrating lymphocytes (TILs) in intermediate biopsies at day 15.

Results: Recruitment was suspended mainly due to liver toxicity after enrolment of 50 of the planned 256 patients. In each arm (buparlisib n = 25; placebo n = 25) 21 patients (84%) had wild type PIK3CA and 4 patients (16%) had mutant PIK3CA. Overall, pCR rate was similar between buparlisib and placebo arms (32.0% versus 40%; one-sided P = 0.811). A trend towards higher ORR (68.8% versus 33.3%; P = 0.053) and a significant decrease in Ki67 (75% versus 26.7%; P = 0.021) was observed in buparlisib versus placebo arm in the ER+ subgroup (Pinteraction = 0.03).

Conclusions: Addition of the pan-PI3K inhibitor buparlisib to taxane-trastuzumab-based therapy in HER2+ early breast cancer was not feasible. However, the higher ORR and Ki67 reduction in the ER+, HER2+ subgroup indicates a potential role for PI3K-targeted therapy in this setting and may warrant further investigation with better-tolerated second-generation PI3K inhibitors.

Trial registration identifier: NCT01816594.

Keywords: Buparlisib; HER2; NeoPHOEBE; Neoadjuvant; Primary breast cancer; pCR.

Conflict of interest statement

Conflict of interest statement

S Loibl has received funding from Novartis. LSC has received funding from Novartis, Roche, Pfizer, GlaxoSmithKline, Esai Co Ltd, ASLAN Pharmaceuticals, Roche and AstraZeneca. SK has a consulting/advisory role for Novartis. GS has received funding from Novartis, AstraZeneca, Pfizer, Celegne, Teva, Roche and Lilly. ML has received funding from Novartis. MJP has received funding from Roche. GVM has received funding from Novartis. JB has a leadership role at Infinity Pharmaceuticals and ownership interest in GRAIL. S Loi has received funding from Roche, Pfizer, Novartis and Merck. ST and PU are Novartis employees. All other authors declare no conflict of interest.

Copyright © 2017 Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Consort statement.

Fig. 2

Change in Ki67 levels and percentage of TILs. a: Change in Ki67 levels from baseline up to day 15 with buparlisib versus placebo. b: Change in percentage of TILs from baseline up to day 15 with buparlisib versus placebo. TIL, tumor infiltrating lymphocytes.