Palbociclib: Additional Phase II data

Additional data from the double-blind, international Phase II PALOMA-1 (Study 1003/TRIO-18) trial in 165 evaluable postmenopausal women with estrogen receptor-positive, HER2-negative advanced breast cancer showed that first-line treatment with once-daily 125 mg palbociclib for 3 weeks of a 4-week cycle plus Femara letrozole led to a median PFS, the primary endpoint, of 20.2 months vs.10.2 months for Femara alone (HR=0.488, 95% CI: 0.319, 0.748, p=0.0004). On secondary endpoints, palbociclib plus Femara led to an ORR of 43% vs. 33% for Femara alone. The clinical benefit rate (CBR), defined as a complete or partial response or stable disease for >=24 weeks, was 81% for palbociclib plus Femara vs. 58% for Femara alone. An initial analysis of median OS showed that palbociclib plus Femara led to a non-significant improvement on the secondary endpoint vs. Femara alone (37.5 vs. 33.3 months, HR=0.813, 95% CI: 0.492, 1.345, p=0.2105). Pfizer said a follow-up OS analysis following the accrual of additional events will be conducted, but the pharma declined to disclose a time frame for when additional OS data are expected. The combination was generally well tolerated. Data were presented at the American Association for Cancer Research meeting in San Diego.

In February, Pfizer reported that palbociclib plus Femara met the primary endpoint in PALOMA-1. Interim data from the trial were reported in 2012 (see BioCentury, Dec. 10, 2012 & Feb. 10, 2014). Last year, FDA granted palbociclib breakthrough therapy designation to treat breast cancer based on interim data from PALOMA-1 (see BioCentury, April 15, 2013). ...