CDK4/CDK6 inhibitors show great promise for breast cancer treatment

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Abstracts released Wednesday ahead of next month’s American Society of Clinical Oncology meeting showed strong survival and response rate data for cyclin dependent kinase 4 (CDK4) and CDK6 inhibitors from Pfizer Inc. (NYSE:PFE) and Eli Lilly and Co. (NYSE:LLY) to treat breast cancer. Separately, Novartis AG (NYSE:NVS; SIX:NOVN) said Wednesday that it would stop early a trial of its own CDK4/CDK6 inhibitor for breast cancer following a positive interim analysis.

Combined therapy with Pfizer’s Ibrance palbociclib plus letrozole led to progression-free survival (PFS) of 24.8 months vs. 14.5 months for letrozole plus placebo in the Phase III PALOMA-2 study, meeting the trial’s primary endpoint. The objective response rate (ORR) for the Ibrance combo was 42.1% vs. 34.7% for letrozole alone (p=0.031). The 666-patient study evaluated Ibrance as a first-line treatment for estrogen receptor-positive, HER2-negative, advanced or metastatic breast cancer in postmenopausal women. Ibrance has accelerated approval from FDA in combination with letrozole in the first-line setting. The drug has full approval to treat hormone receptor (HR)-positive, HER2-negative metastatic breast cancer in combination with Faslodex fulvestrant in women whose disease has progressed after endocrine therapy.

In an eight-month interim analysis of the Phase II MONARCH 1 study, Lilly’s CDK4/CDK6 inhibitor abemaciclib led to a PFS of 5.7 months and ORR of 17.4%. The data are the first reported Phase II results for the compound, which is in Phase III testing for HR+ breast cancer and lung cancer. MONARCH 1 enrolled 132 patients with HR-positive, HER2-negative metastatic breast cancer whose disease progressed on or after endocrine therapy and chemotherapy.

Novartis said an interim analysis of the 668-patient Phase III MONALEESA-2 trial showed that ribociclib plus letrozole met the primary PFS endpoint vs. letrozole alone as first-line therapy for postmenopausal women with HR-positive, HER2-negative advanced breast cancer. As a result, the pharma said it would stop the study early. Novartis plans to present full data at an upcoming medical meeting, and hopes to submit regulatory applications for ribociclib in 2H16. The CDK4 and CDK6 inhibitor is in two other ongoing Phase III studies for HR-positive, HER2-negative breast cancer.

Now that three pharma giants have all reported positive results on CDK4/CDK6 inhibitors for the treatment of breastcancer, little doubt remains that these molecules can have a tremendous impact on breastcancer patients.

Adapted from BioCentury.