Uses

Abemaciclib is a CDK4/6 inhibitor indicated for HR-positive, HER2-negative breast cancer: (1) as adjuvant therapy with endocrine therapy in node-positive early breast cancer at high recurrence risk; (2) combined with an aromatase inhibitor as initial therapy for advanced or metastatic disease; (3) combined with fulvestrant for disease progression following prior endocrine therapy; (4) as monotherapy for disease progression after endocrine and prior chemotherapy.

Do not use if

No formal contraindications listed. Avoid use in pregnancy due to potential fetal harm. Not recommended during breastfeeding.

Side effects

Common adverse effects include diarrhea, neutropenia, fatigue, nausea, infections, and abdominal pain. Serious effects include severe diarrhea with dehydration, significant neutropenia, interstitial lung disease/pneumonitis, hepatotoxicity, and venous thromboembolism.

Warnings

Monitor complete blood counts for neutropenia; dose interruption or reduction may be required. Initiate antidiarrheal therapy at the first sign of loose stools. Monitor liver function tests periodically. Evaluate for interstitial lung disease if respiratory symptoms develop.

How it works

Abemaciclib inhibits cyclin-dependent kinases 4 and 6 (CDK4/6), which in ER+ breast cancer cells promotes Rb phosphorylation and cell cycle progression. Inhibition of CDK4/6 arrests cells in G1 phase, reducing tumor cell proliferation.

Storage

Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).