Pfizer, announced the New Drug Application (NDA) for palbociclib has been accepted for filing and granted Priority Review by the United States Food and Drug Administration (US FDA). This NDA requests FDA approval of palbociclib, in combination with letrozole, as a first-line treatment for postmenopausal women with estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer who have not received previous systemic treatment for their advanced disease. The submission is based on the final results of PALOMA-1, a randomised, phase 2 trial comparing palbociclib plus letrozole versus letrozole alone in this population of patients.

The FDA’s Priority Review status accelerates the review time from 10 months to a goal of six months from the day of acceptance of filing and is given to drugs that may offer major advances in treatment or may provide a treatment where no adequate therapy exists. The Prescription Drug User Fee Act (PDUFA) goal date for a decision by the FDA is April 13, 2015.

Palbociclib received Breakthrough Therapy designation from the FDA in April 2013, for the first-line systemic treatment of women with advanced or metastatic ER+, HER2- breast cancer.

“If approved as a first-line therapy in combination with letrozole, palbociclib will be an important new option for the thousands of women in the US who are living with metastatic breast cancer,” said Garry Nicholson, president, Pfizer Oncology. “We look forward to continuing to work closely with the FDA through the review process.”

Pfizer recently announced the initiation of a multi-center, open-label expanded access Programme (EAP) in the United States for palbociclib. Through the Programme, palbociclib is available to post-menopausal women with hormone receptor-positive (HR+), HER2- advanced breast cancer who are eligible for letrozole therapy and for whom enrolling in other palbociclib clinical trials is not an option. Healthcare professionals and patients can learn more about the palbociclib EAP by visiting www.clinicaltrials.gov (trial number: NCT02142868).

Palbociclib is an investigational oral targeted agent that selectively inhibits cyclin-dependent kinases (CDKs) 4 and 6 to regain cell cycle control and block tumor cell proliferation.

Loss of cell cycle control is a hallmark of cancer and CDK 4/6 are overactivated in numerous cancers, leading to loss of proliferative control.2,3CDK 4/6 are key regulators of the cell cycle that trigger cellular progression from growth phase (G1) into phases associated with DNA replication (S).4,5 CDK 4/6, whose increased activity is frequent in estrogen receptor-positive (ER+) breast cancer (BC), are key downstream targets of ER signaling in ER+ BC.6,7 Preclinical data suggest that dual inhibition of CDK 4/6 and ER signaling is synergistic, and it has been shown to stop growth of ER+ BC cell lines in the G1 phase.

Palbociclib is not approved for any indication in any market. PALOMA-1 (also known as Study 1003 and TRIO-18) is a phase 2 trial designed to assess progression-free survival in post-menopausal women with ER+, HER2- advanced breast cancer receiving palbociclib (125 mg once daily for three out of four weeks in repeated cycles) in combination with letrozole versus letrozole alone (2.5 mg once daily on a continuous regimen). Final results from PALOMA-1 were presented at the American Association for Cancer Research (AACR) Annual Meeting 2014. PALOMA-1 was conducted in collaboration with the Jonsson Cancer Center’s Revlon/UCLA Women’s Cancer Research Programme, led by Dr. Dennis Slamon.

Pfizer has worked closely with investigators and international breast cancer experts to establish a robust development Programme for palbociclib in ER+, HER2- breast cancer across stages and treatment settings.

Pfizer has initiated two phase 3 studies of palbociclib in advanced/metastatic breast cancer. PALOMA-2 (also known as Study 1008) is a randomised (2:1), multi-center, double blind Phase 3 study that evaluates palbociclib in combination with letrozole versus letrozole plus placebo as a first-line treatment for post-menopausal patients with ER+, HER2- advanced breast cancer. PALOMA-3 (also known as Study 1023) is a randomised (2:1), multi-centre, double blind pshase 3 study that evaluates palbociclib in combination with fulvestrant versus fulvestrant plus placebo in women with hormone receptor-positive (HR+), HER2- metastatic breast cancer whose disease has progressed after prior endocrine therapy. PALOMA-2 and PALOMA-3 have recently completed enrollment.

Additional, investigator-led studies of palbociclib in advanced/metastatic breast cancer and in early breast cancer are open and enrolling patients, including the PEARL and PENELOPE-B studies. PEARL, sponsored by Grupo Español de Investigación en Cáncer de Mama (GEICAM, Spanish Breast Cancer Research Group), with participation from the Central European Cooperative Oncology Group (CECOG), is a randomised (1:1), multi-centre, open-label phase 3 study evaluating palbociclib in combination with exemestane versus capecitabine in post-menopausal women with ER+, HER2- metastatic breast cancer whose disease was refractory to previous non-steroidal aromatase inhibitors (letrozole or anastrozole). PENELOPE-B is a randomised (1:1), double blind, placebo-controlled phase 3 study comparing palbociclib plus standard endocrine therapy to placebo plus standard endocrine therapy in patients with HR+, HER2- early-stage breast cancer with certain features that suggest an increased risk for recurrence after completing pre-operative chemotherapy followed by surgery. This international study is sponsored by the German Breast Group (GBG).