21MO - Primary results of a China bridging, phase II randomized study of initial endocrine therapy (ET) ± ribociclib (RIB) in pre- & postmenopausal Chinese women with HR+/HER2– ABC

Background

MONALEESA (ML)-2 and -7 enrolled postmenopausal (postM) and premenopausal (preM) patients (pts) with HR+/HER2− ABC, respectively, to initial RIB + ET treatment. Both demonstrated a statistically significant PFS and OS benefit in the ITT populations, with similar trends in the Asian subgroups. Specifically, regarding PFS in the Asian subgroups, RIB + ET had an HR of 0.39 (0.17-0.91) in ML-2 (n=51; median follow-up 15.3 mo) and ET had an HR of 0.40 (0.26-0.63) in ML-7 (n=198; median follow-up 19.2 mo). Here we report the primary results of a phase II bridging study of initial ET ± RIB in postM and preM pts from mainland China with HR+/HER2– ABC.

Methods

Pts were randomized 1:1; postM received letrozole (LET) + RIB or placebo (PBO) and preM received NSAI + goserelin + RIB or PBO. Primary endpoint was PFS (local assessment based on RECIST 1.1 criteria). The study was not powered to show statistical significance; it was adequately sized to show consistency of PFS of RIB + ET vs ET in Chinese populations compared to ML-2 and ML-7. Secondary endpoints included PK, OS, ORR, and safety.

Results

As of 15 April 2022, 77 and 77 postM pts and 79 and 77 preM pts were treated with RIB or PBO, respectively. Median follow-up was 34.7 mo for both groups. Baseline characteristics were generally balanced between arms within the cohorts. In the postM cohort, mPFS was not reached with RIB vs 18.5 mo with PBO (HR 0.400; 95% CI 0.258-0.618). In the preM cohort, the median PFS was 27.6 vs 14.7 mo (HR 0.672; 95% CI 0.448-1.009) for RIB vs PBO. ORR was higher for RIB in both postM and preM pts (Table); OS was not mature. The adverse event profile was consistent with what is known for ET ± RIB; the tolerability is consistent with ML-2 and -7 with no new findings.

Conclusions

Along with the results of the ML studies, this bridging study demonstrates the consistent efficacy benefit and well-tolerated safety profile of RIB + ET in Chinese pts. Table: 21MO

^aMeasurable disease.

Clinical trial identification

NCT03671330.

Editorial acknowledgement

Medical writing support was provided by Chris Carter at MediTech Media, funded by Novartis Pharmaceuticals Corporation.

Legal entity responsible for the study

Novartis Pharmaceuticals Corporation.

Funding

Novartis Pharmaceuticals Corporation.

Disclosure

Y. Bai, K. Amin, P. Deshpande, Y. Bi: Financial Interests, Personal, Full or part-time Employment: Novartis. All other authors have declared no conflicts of interest.