59MO - Adjuvant Abemaciclib Combined with Endocrine Therapy (ET): Efficacy Results in monarchE Cohort 1

Background

Abemaciclib (oral CDK4 & 6 inhibitor) plus ET as adjuvant treatment for HR+, HER2- high risk early breast cancer (EBC), previously demonstrated robust benefit with an acceptable safety profile in the monarchE trial. Here we present efficacy data in a monarchE patient population (Cohort 1) which has a high risk of recurrence, can easily be identified in clinical practice, and recently received regulatory approval.

Methods

monarchE, a global, phase 3 trial, randomly assigned (1:1) 5637 patients to receive ET +/- adjuvant abemaciclib into 2 cohorts. Cohort 1 (C1) enrolled 5120 patients with either ≥4 positive axillary lymph nodes (pALN), or 1-3 pALN plus additional high risk features of Grade 3 disease and/or tumor ≥5 cm. Cohort 2 enrolled 517 patients, was previously described, and data are immature.

Results

With 28 months median follow-up in C1 (data cut off April 2021), the 17% risk of recurrence at 3Y in the ET alone arm confirms the high risk nature of this patient population. Abemaciclib+ET demonstrated a clinically meaningful benefit in reducing the risk of developing an IDFS event by 32% (absolute benefit of 5.7% at 3Y) and a DFRS event by 33% (4.5% absolute benefit at 3Y)(Table). Within C1, consistent treatment benefit in IDFS and DRFS was seen in subgroups of patient and disease characteristics. Safety analyses, conducted on the entire safety population, were consistent with the known profile of abemaciclib. Table: 59MO

DRFS: distant relapse-free survival; IDFS: invasive disease-free survival

Conclusions

As C1 comprises 91% of the patients in monarchE, C1 drives the robust benefit observed in the ITT population. C1 data demonstrate substantial evidence of the benefit of adjuvant abemaciclib+ET in patients with HR+, HER2- EBC at high risk of recurrence who can be identified easily as part of routine diagnostic breast cancer workup.

Clinical trial identification

NCT03155997.

Editorial acknowledgement

Medical writing support and editorial assistance were provided by Eglantine Julle-Daniere, employee of Eli Lilly and Company.

Legal entity responsible for the study

Eli Lilly and Company.

Funding

Eli Lilly and Company.

Disclosure

M. Toi: Financial Interests, Personal, Advisory Board, + Invited speaker: Kyowa-Kirin, Daiichi Sankyo, Eli Lilly and Companies; Financial Interests, Personal, Advisory Board: BMS, Athenex Oncology, Bertis, Terumo, Kansai Medical Net; Financial Interests, Personal, Invited Speaker: Chugai, Takeda, Pfizer, Taiho, Eisai, AstraZeneca, MSD, Exact Science, Novartis, Shimadzu, Yakult, Nippon-Kayaku, Devicore Medical Japan; Financial Interests, Institutional, Research Grant, Research Grant to Institution, Funding to Institution Coordianting PI (non-finacial interest), Steering Committee member (non-financial interest), Local PI (non-finacial interest): Chugai; Financial Interests, Institutional, Research Grant, Research grant to clinical study: Takeda, Yakult, GL Science; Financial Interests, Institutional, Funding, Research Grant to Institution Coordinating PI (non-finacial interest): Pfizer; Financial Interests, Institutional, Research Grant, Research grant to a preclinical study: Kyowa-Kirin; Financial Interests, Institutional, Funding, Funding to translational research of JBCRG assoc. studies: The Japan Breast Cancer Research Group association; Financial Interests, Institutional, Funding, Funding to translational research of KBCRN assoc studies: The Kyoto Breast Cancer Research Network association; Financial Interests, Institutional, Funding, Funding to a clinical study Coordinating PI of a neoadjuvant study (non-financial interest): Eisai; Financial Interests, Institutional, Funding, Funding to a clinical study Steering committee member (non-financial interest): Eli Lilly and companies; Financial Interests, Institutional, Research Grant, Research grant to a preclinical study Steering committee member (non-financial interest): Daiichi Sankyo; Financial Interests, Institutional, Research Grant, Research grant to a basic-cliical study Steering committee member (non-financial interest): AstraZeneca; Financial Interests, Institutional, Research Grant, Research grant to a basic study: Astellas, AFI technology, Luxonus; Financial Interests, Institutional, Research Grant, Research grant to a basic investigation: Shimadzu; Financial Interests, Institutional, Research Grant, Research grant to a basic-clinical study: Nippon-Kayaku, Shionogi; Non-Financial Interests, Invited Speaker, No salary: The Japanese Onco-Cardiology Society, The Kyoto Breast Cancer Research Network association, The Japan Breast Cancer Research Group Association, Organisation for Oncology and Translational Research; Other, Deputy Editor: International Journal of Oncology; Other, Associate editor: British Journal of Cancer, Scientific Reports, Breast Cancer Research and Treatment, Cancer Science, Frontiers in Women's Cancer, Asian Journal of Surgery, Asian Journal of Breast Surgery. F. Boyle: Financial Interests, Personal, Advisory Role: Roche, Pfizer, Eli Lilly and Company, and Novartis; Financial Interests, Personal, Other, Honoraria: Roche, Pfizer, Eli Lilly and Company, and Novartis. M. Reinisch: Financial Interests, Other, Personal fees: AstraZeneca, MSD, Eli Lilly and Company, Roche, Novartis, Daiichi Sankyo, Seagen, Pfizer, Somatex; Non-Financial Interests, Other, Travel: Novartis, Pfizer. R.J. Wei, F. Sapunar, B. Grimes: Financial Interests, Personal, Full or part-time Employment: Eli Lilly and Company. S.C. Nabinger: Financial Interests, Personal, Full or part-time Employment: Eli Lilly and Company; Financial Interests, Personal, Stocks/Shares: Eli Lilly and Company. S.R.D. Johnston: Financial Interests, Personal, Other, Consulting/Advisory Role: Eli Lilly, Puma Biotechnology; Financial Interests, Personal, Other, Consulting/Advisory Role and Speakers Bureau: AstraZeneca, Pfizer, Novartis; Financial Interests, Personal, Other, Speakers Bureau: Eisai. Roche/Genentech; Financial Interests, Institutional, Funding, Research funding for lab studies and clinical trials: Pfizer; Financial Interests Institutional, Funding, Research funding for lab studies: Puma Biotechnology; Financial Interests, Institutional, Funding, Research funding for clinical trials: Eli Lilly, AstraZeneca, Novartis, Roche/Genentech. All other authors have declared no conflicts of interest.