MONARCH 3 Interim Results Show Superior PFS With Abemaciclib in Breast Cancer

Eli Lilly and Company has announced that abemaciclib, a CDK4/6 inhibitor that regulates the cell cycle, improved progression-free survival (PFS) as well as objective response rate (ORR) when combined with an aromatase inhibitor (AI), compared with AI alone, in patients with breast cancer.

The trial, MONARCH 3, is a randomized, double-blind phase 3 study of an AI (anastrozole or letrozole), combined with abemaciclib or placebo in postmenopausal women with hormone receptor-positive, HER2-negative recurrent or metastatic breast cancer. The 493 women enrolled in the trial had not previously been treated for advanced disease. While PFS was the primary trial endpoint, secondary endpoints include overall survival, duration of response, and ORR, among others.

The women were randomized to receive 150 mg first-line abemaciclib or placebo, twice daily, in combination with 1 mg anastrazole or 2.5 mg letrozole once daily, till progression or unacceptable toxicity. The actual trial findings will be released at a conference in the second half of 2017.

“We are very excited about the results seen in patients with breast cancer, from single-agent activity to clinically meaningful benefit when used in combination with fulvestrant or aromatase inhibitors,” said Levi Garraway, MD, PhD, senior vice president, global development and medical affairs, Lilly Oncology.

The final PFS data collection date for MONARCH 3 is November 2017. The company plans to file global submissions of these results in the third quarter of 2017.

In addition to breast cancer, abemaciclib is also being evaluated in lung cancer, brain metastases, and pancreatic cancer.

Abemaciclib is the third CDK4/6 inhibitor to be approved for breast cancer, following Pfizer’s palbociclib (Ibrance, approved in 2015) and ribociclib (Kisqali, approved in March 2017) by Novartis. This raises the bar for Lilly to ensure market share for abemaciclib.

The company’s pricing strategy, over and above better benefit, could help place the drug on formularies as well. A 21-capsule supply of palbociclib could cost $11,453, while the price of ribociclib varies based on the dose (eg, 28-day supply of 600 mg dose is $10,950).