Ribociklibiä

Ribociklibiä is the Finnish form used for the cancer drug ribociclib, a selective inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6). It is marketed under the brand name Kisqali and was developed for the treatment of hormone receptor–positive, HER2-negative breast cancer. It is used in combination with endocrine therapies as part of targeted treatment regimens.

Mechanism of action: Ribociclibiä inhibits CDK4 and CDK6, enzymes that phosphorylate the retinoblastoma (RB) protein. Inhibition prevents RB inactivation, causing cells to arrest in the G1 phase of the cell cycle and reducing cancer cell proliferation. The drug is used to enhance the effects of endocrine therapy in HR+, HER2− breast cancer.

Medical use: In postmenopausal women with HR+, HER2− advanced or metastatic breast cancer, ribociclibiä is approved in combination with letrozole as initial therapy. It is also approved in combination with fulvestrant for patients whose disease progressed after prior endocrine therapy. The ongoing MONALEESA clinical trial program has evaluated combinations with letrozole, fulvestrant, and other endocrine strategies, showing improvements in progression-free survival in various settings.

Dosing and administration: The common regimen is 600 mg taken orally once daily for 21 days on a 28-day cycle, in combination with either letrozole or fulvestrant, with dose adjustments for adverse effects as needed.

Safety and interactions: Common side effects include neutropenia, nausea, fatigue, alopecia, and rash. Ribociklibiä can cause hepatotoxicity (elevated liver enzymes) and QT interval prolongation, requiring monitoring. It is metabolized mainly by CYP3A4, so strong CYP3A inhibitors or inducers can alter drug levels, and use with other QT-prolonging agents should be cautious. It is teratogenic and should be avoided in pregnancy.

Regulatory status: Ribociklibiä is approved in many jurisdictions and marketed as Kisqali by Novartis for HR+, HER2− breast cancer in approved combinations.