Patricia Cortazar

See accompanying editorial on page 1186 Lee M. Ellis, University of Texas MD Anderson Cancer Center, Houston, TX; David S. Bernstein and Richard L. Schilsky, American Society of Clinical Oncology, Alexandria, VA; Emile E. Voest, University Medical Center Utrecht, Utrecht, the Netherlands; Jordan D. Berlin, Vanderbilt-Ingram Cancer Center, Nashville, TN; Daniel Sargent, Mayo Clinic, Rochester, MN; Patricia Cortazar, US Food and Drug Administration, Silver Spring, MD; Elizabeth Garrett-Mayer, Medical University of South Carolina, Charleston, SC; Roy S. Herbst and Rogerio C. Lilenbaum, Yale Cancer Center, New Haven, CT; Camelia Sima and Mithat Gonen, Memorial Sloan-Kettering Cancer Center, New York, NY; Alan P. Venook, Helen Diller Family Comprehensive Cancer Center at University of California San Francisco, San Francisco, CA; Neal J. Meropol, University Hospitals Seidman Cancer Center, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH; Lowell E. Schnipper, Beth Israel Deaconess Medical Center, Boston, MA.

On February 3, 2015, the FDA granted accelerated approval to palbociclib (IBRANCE, Pfizer Inc.), an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), for use in combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, HER2-negative advanced breast cancer as initial endocrine-based therapy for their metastatic disease. The approval is based on a randomized, multicenter, open-label phase I/II trial (PALOMA-1) in 165 patients randomized to palbociclib (125 mg orally daily for 21 consecutive days, followed by 7 days off treatment) plus letrozole (2.5 mg orally daily) or letrozole alone. The phase II portion of the trial was divided into two cohorts: cohort 1 enrolled 66 biomarker-unselected patients and cohort 2 enrolled 99 biomarker-positive patients. The major efficacy outcome measure was investigator-assessed progression-free survival (PFS). A large magnitude of improvement in PFS was observed in patients receiving palbociclib plus letrozole compared with patients receiving letrozole alone (HR, 0.488; 95% confidence interval, 0.319-0.748). Multiple sensitivity analyses were supportive of clinical benefit. The most common adverse reaction in patients receiving palbociclib plus letrozole was neutropenia. This article summarizes the FDA thought process and data supporting accelerated approval based on PALOMA-1 that may be contingent upon verification and description of clinical benefit in the ongoing and fully accrued confirmatory trial PALOMA-2.

On February 22, 2013, the FDA licensed ado-trastuzumab emtansine (Kadcyla; Genentech, Inc.) for use as a single agent for the treatment of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) who previously received trastuzumab and a taxane, separately or in combination. The clinical basis for licensure was a phase III trial in 991 patients with HER2-positive MBC that randomly allocated patients to receive ado-trastuzumab emtansine (n=495) or lapatinib in combination with capecitabine (n=496). The coprimary endpoints were progression-free survival (PFS) based on tumor assessments by an independent review committee and overall survival (OS). Statistically significant improvements in PFS and OS were observed in patients receiving ado-trastuzumab emtansine compared with patients receiving lapatinib plus capecitabine [difference in PFS medians of 3.2 months, HR, 0.65 (95% confidence interval, CI, 0.55-0.77), P<0.0001 and difference in OS medians of 5.8 months, HR, 0.68 (95% CI, 0.55-0.85), P=0.0006]. The most common adverse reactions in patients receiving ado-trastuzumab emtansine were fatigue, nausea, musculoskeletal pain, thrombocytopenia, headache, increased aminotransferase levels, and constipation. Other significant adverse reactions included hepatobiliary disorders and left ventricular dysfunction. Given the PFS and OS results, the benefit-risk profile was considered favorable.