Final overall survival analysis from the MONARCH 3 study of Verzenio (abemaciclib) presented at the 2023 San Antonio Breast Cancer Symposium

MONARCH 3 evaluated Verzenio (abemaciclib) in combination with an aromatase inhibitor (AI) compared to an AI alone as initial endocrine-based therapy for post-menopausal patients with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced or metastatic breast cancer.

At eight years of follow-up, MONARCH 3 showed women taking Verzenio and an AI had a median overall survival (OS) of more than 5.5 years – an increase of 13.1 months compared to the control arm in the intent-to-treat (ITT) population (66.8 vs 53.7 months), although statistical significance for the OS outcome was not reached (HR, 0.804; 95% CI, 0.637-1.015; p=0.0664).

For women with visceral organ metastases, data showed a median OS of more than five years, with an increase in median OS of 14.9 months in the Verzenio arm compared to the control arm (63.7 vs 48.8 months). This included those women whose breast cancer has spread to the liver or lungs. Patients with visceral disease are at an increased risk of disease progression and death compared to metastatic breast cancer (MBC) patients without visceral metastases. The OS results for this subpopulation were also not statistically significant (HR, 0.758; 95% CI, 0.558-1.030; p=0.0757).

"At eight years of follow-up, when the natural history of metastatic breast cancer starts to substantially impact patient survival, it is highly encouraging to see abemaciclib combined with AI therapy deliver a meaningful survival difference of 13 months in the ITT population and more than 14 months in women at even higher risk due to visceral disease," said Stephen Johnston M.D., Ph.D., Professor of Breast Cancer Medicine and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust (London, U.K.) and investigator on the MONARCH 3 trial. "Despite missing statistical significance, these data are clinically relevant and highly consistent with the overall body of evidence for abemaciclib in advanced or metastatic breast cancer."

The median progression free survival (PFS) benefit, the primary endpoint of the MONARCH 3 study, was maintained (29.0 vs 14.8 months; HR, 0.535; 95% CI, 0.429-0.668; nominal p<0.0001), with substantial difference in 6-year pfs rates (23.3% in the verzenio arm vs 4.3% in the control arm). pfs statistical significance was achieved in an interim analysis in 2017, leading to global regulatory approvals for this indication in 2018. no new safety signals were observed with longer-term use.

"With a median OS of more than 5.5 years in patients treated with Verzenio in this study, these data further support the role of Verzenio in the survival of women with HR+, HER2- metastatic breast cancer," said David Hyman, M.D., chief medical officer, Lilly. "We remain confident in the differentiated profile of Verzenio and we look forward to sharing these results with the clinical community at SABCS and getting their perspective on these data and relevance for clinical practice."