Palbociclib (Ibrance—Pfizer) has received FDA approval for the treatment of advanced (metastatic) breast cancer in postmenopausal women. The new agent is indicated for use in combination with letrozole to treat estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative metastatic breast cancer as a first-line hormone-based therapy for metastatic disease.Mechanism of actionPalbociclib is the first and only FDA- approved medication in a new treatment class of medications. It is a selective inhibitor of cyclindependent kinases (CDKs) 4/6—kinases involved in tumor cell progression throughout the cell cycle. When palbociclib inhibits CDK 4 and 6, in vitro ER-positive breast cancer cell lines show decreased proliferation. When combined with letrozole, palbociclib is able to decrease Rb phosphoryla- tion, downstream signaling, and overall tumor growth."Palbociclib has an exciting mechanism of action, something we typically don't have for breast cancer," Laura Boehnke Michaud, PharmD, FASHP, BCOP, Manager and Clinical Pharmacy Specialist at the University of Texas M. D. Anderson Cancer Center, told Pharmacy Today."Historically, patients take anastrazole or letrozole for their first-line hormone-based therapy since it is important to use it for early treatment. But palbociclib is indicated for meta- static disease [in patients] who have yet to use hormone-based therapy, which may not be likely," Michaud explained. "Palbociclib is very new, with little published data and a narrow indication; thus, further studies are needed to determine how we can use this medication," she added.PALOMA-1Palbociclib's efficacy and safety were evaluated in PALOMA-1, a randomized, open-label, multicenter Phase II trial of 165 postmenopausal women with ER-positive, HER2-negative advanced breast cancer who had received no prior treatment. Patients were administered either a combination of palbociclib and letrozole or letrozole alone for 21 consecutive days, followed by 7 days off therapy.Overall, the study showed that patients receiving the palbociclib/ letrozole combination lived a median of 20.2 months without their cancer progressing (progression-free survival), compared with 10.2 months in patients receiving letrozole only.Adverse reactionsThe most common adverse reactions included neutropenia (75%), leukopenia (43%), fatigue (410%), anemia (35%), and upper respiratory tract infections (31%). The most frequently reported serious adverse reactions were pulmonary embolism (4%) and diarrhea (2%). In addition, infections have been reported at a higher rate in patients receiving both palbociclib/letrozole (5%) compared with those receiving letrozole alone (0%).Patient counselingGive patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood.Palbociclib (Ibrance)Manufacturer: PfizerDrug class: Cyclindependent kinaseCDK) 4 and 6 inhibitorIndication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease.Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d.Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood.FDA granted palbociclib breakthrough therapy designation and approved it under the agency's accelerated approval program to expedite patient access to this medication. Palbociclib (Ibrance—Pfizer) has received FDA approval for the treatment of advanced (metastatic) breast cancer in postmenopausal women. The new agent is indicated for use in combination with letrozole to treat estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative metastatic breast cancer as a first-line hormone-based therapy for metastatic disease. Mechanism of actionPalbociclib is the first and only FDA- approved medication in a new treatment class of medications. It is a selective inhibitor of cyclindependent kinases (CDKs) 4/6—kinases involved in tumor cell progression throughout the cell cycle. When palbociclib inhibits CDK 4 and 6, in vitro ER-positive breast cancer cell lines show decreased proliferation. When combined with letrozole, palbociclib is able to decrease Rb phosphoryla- tion, downstream signaling, and overall tumor growth."Palbociclib has an exciting mechanism of action, something we typically don't have for breast cancer," Laura Boehnke Michaud, PharmD, FASHP, BCOP, Manager and Clinical Pharmacy Specialist at the University of Texas M. D. Anderson Cancer Center, told Pharmacy Today."Historically, patients take anastrazole or letrozole for their first-line hormone-based therapy since it is important to use it for early treatment. But palbociclib is indicated for meta- static disease [in patients] who have yet to use hormone-based therapy, which may not be likely," Michaud explained. "Palbociclib is very new, with little published data and a narrow indication; thus, further studies are needed to determine how we can use this medication," she added. Palbociclib is the first and only FDA- approved medication in a new treatment class of medications. It is a selective inhibitor of cyclindependent kinases (CDKs) 4/6—kinases involved in tumor cell progression throughout the cell cycle. When palbociclib inhibits CDK 4 and 6, in vitro ER-positive breast cancer cell lines show decreased proliferation. When combined with letrozole, palbociclib is able to decrease Rb phosphoryla- tion, downstream signaling, and overall tumor growth. "Palbociclib has an exciting mechanism of action, something we typically don't have for breast cancer," Laura Boehnke Michaud, PharmD, FASHP, BCOP, Manager and Clinical Pharmacy Specialist at the University of Texas M. D. Anderson Cancer Center, told Pharmacy Today. "Historically, patients take anastrazole or letrozole for their first-line hormone-based therapy since it is important to use it for early treatment. But palbociclib is indicated for meta- static disease [in patients] who have yet to use hormone-based therapy, which may not be likely," Michaud explained. "Palbociclib is very new, with little published data and a narrow indication; thus, further studies are needed to determine how we can use this medication," she added. PALOMA-1Palbociclib's efficacy and safety were evaluated in PALOMA-1, a randomized, open-label, multicenter Phase II trial of 165 postmenopausal women with ER-positive, HER2-negative advanced breast cancer who had received no prior treatment. Patients were administered either a combination of palbociclib and letrozole or letrozole alone for 21 consecutive days, followed by 7 days off therapy.Overall, the study showed that patients receiving the palbociclib/ letrozole combination lived a median of 20.2 months without their cancer progressing (progression-free survival), compared with 10.2 months in patients receiving letrozole only. Palbociclib's efficacy and safety were evaluated in PALOMA-1, a randomized, open-label, multicenter Phase II trial of 165 postmenopausal women with ER-positive, HER2-negative advanced breast cancer who had received no prior treatment. Patients were administered either a combination of palbociclib and letrozole or letrozole alone for 21 consecutive days, followed by 7 days off therapy. Overall, the study showed that patients receiving the palbociclib/ letrozole combination lived a median of 20.2 months without their cancer progressing (progression-free survival), compared with 10.2 months in patients receiving letrozole only. Adverse reactionsThe most common adverse reactions included neutropenia (75%), leukopenia (43%), fatigue (410%), anemia (35%), and upper respiratory tract infections (31%). The most frequently reported serious adverse reactions were pulmonary embolism (4%) and diarrhea (2%). In addition, infections have been reported at a higher rate in patients receiving both palbociclib/letrozole (5%) compared with those receiving letrozole alone (0%).Patient counselingGive patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood.Palbociclib (Ibrance)Manufacturer: PfizerDrug class: Cyclindependent kinaseCDK) 4 and 6 inhibitorIndication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease.Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d.Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood.FDA granted palbociclib breakthrough therapy designation and approved it under the agency's accelerated approval program to expedite patient access to this medication. The most common adverse reactions included neutropenia (75%), leukopenia (43%), fatigue (410%), anemia (35%), and upper respiratory tract infections (31%). The most frequently reported serious adverse reactions were pulmonary embolism (4%) and diarrhea (2%). In addition, infections have been reported at a higher rate in patients receiving both palbociclib/letrozole (5%) compared with those receiving letrozole alone (0%). Patient counselingGive patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood. Patient counselingGive patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood. Patient counselingGive patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood. Give patients the Medication Guide and review it with them carefully. Inform patients that palbociclib may cause serious adverse effects, including infections resulting from neutropenia, especially upper respiratory infections, and pulmonary embolisms. Advise patients to consult their primary care provider if they experience any such adverse events. Counsel patients to monitor their temperature and withhold their next palobciclib dose if they experience a fever of at least 38.5 °C or greater. Patients should not take palbociclib with food or chew, crush, or open palbociclib capsules before swallowing them. Advise patients to avoid taking palbociclib with grapefruit or grapefruit products because they may increase the amount of palbociclib in the blood. Palbociclib (Ibrance)Manufacturer: PfizerDrug class: Cyclindependent kinaseCDK) 4 and 6 inhibitorIndication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease.Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d.Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood. Palbociclib (Ibrance)Manufacturer: PfizerDrug class: Cyclindependent kinaseCDK) 4 and 6 inhibitorIndication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease.Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d.Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood. Palbociclib (Ibrance)Manufacturer: PfizerDrug class: Cyclindependent kinaseCDK) 4 and 6 inhibitorIndication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease.Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d.Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood. Manufacturer: Pfizer Drug class: Cyclindependent kinaseCDK) 4 and 6 inhibitor Indication: In combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative advanced breast cancer as initial endocrine- based therapy for their metastatic disease. Dosage: 125 mg taken orally once a day for 21 consecutive days, followed by 7 days off treatment to comprise the 28-day cycle, combined with letrozole 2.5 mg taken once a day continuously throughout the 28-day cycle■Patients should avoid the concurrent use of strong and moderate CYP3A4 inhibitors. If a strong CYP3A4 inhbitor is used, the dose should be reduced to 75 mg/d. Of note: Palbociclib should be taken with food at approximately the same time each day. Patients should avoid grapefruit and grapefruit juice because they may increase levels of palbociclib in the blood. FDA granted palbociclib breakthrough therapy designation and approved it under the agency's accelerated approval program to expedite patient access to this medication.