Romosozumab: Osteoporozda Kullanılan İlk Sklerostin İnhibitörü

In this lecture, Prof. Dr. Kemal BUHARALIOĞLU provides a detailed explanation of the pharmacological properties, clinical use, and safety profile of romosozumab, the first sclerostin inhibitor used in the treatment of postmenopausal osteoporosis. He examines romosozumab's 'dual' effect of blocking sclerostin and activating the Wnt/beta-catenin signaling pathway, thereby increasing bone formation while suppressing bone resorption, and the relationship between this mechanism and rare diseases such as sclerosteosis and van Buchem disease. Furthermore, the lecture comprehensively addresses the drug's limited 12-month treatment duration, black box warnings regarding cardiovascular risks, post-treatment antiresorptive transition strategies, and SUT reimbursement criteria. The lecture particularly emphasizes the critical role of pharmacists in managing patients at high risk of fractures and ensuring drug safety. 1. Molecular Structure: Romosozumab is the first sclerostin inhibitor used in the treatment of osteoporosis. It is a humanized IgG2 monoclonal antibody and is produced in Chinese hamster ovary (CHO) cells. 2. Mechanism of Action and Dual Pharmacological Effect: Romosozumab activates the Wnt/beta-catenin pathway by blocking sclerostin secreted from osteocytes. This increases bone formation while simultaneously altering the RANKL/OPG balance, reducing bone resorption. This "dual effect" provides a rapid and potent increase in bone density. 3. Genetic Origin and Model Diseases: The drug's development process was modeled after rare genetic diseases (sclerosteosis and van Buchem disease) characterized by sclerostin deficiency and excessive bone hardening due to SOST gene mutations. 4. Indication and Target Group: Romosozumab is indicated for the treatment of postmenopausal women at high risk of fracture (T-score -3.5 or lower, or with a history of fracture). Its use in men and premenopausal women is not yet approved. 5. Dosage and Method of Administration: Romosozumab treatment is administered as two consecutive subcutaneous injections (total 210 mg) once a month. 6. Duration and Transition to Treatment: The duration of use is limited to 12 months (12 doses). This is because the bone-building effect reaches a plateau after the 12th month. To maintain the acquired bone density, a switch to an antiresorptive drug (e.g., denosumab or bisphosphonate) is necessary at the end of treatment. 7. Cardiovascular Safety (Black Box Warning): Due to potential risk signals observed in clinical studies (ARCH and BRIDGE), its use is contraindicated in patients who have had a myocardial infarction (heart attack) or stroke within the last year. This is the most important safety warning for the drug. 8. Monitoring Treatment Response (Biomarkers): Treatment efficacy is monitored by tracking increases in P1NP (Procollagen Type 1 N-terminal propeptide), a marker of bone formation, and decreases in CTX (C-telopeptide), a marker of bone resorption. 9. Other Safety Precautions (Hypocalcemia and Jaw Osteonecrosis): Since the drug may cause hypocalcemia, calcium and vitamin D levels should be monitored before and during treatment, and supplementation should be provided if necessary. A dental examination before treatment is also recommended to assess the risk of jaw osteonecrosis. 10. Pharmacist's Role: The pharmacist should inquire about the patient's cardiovascular history, monitor compliance with the limited 12-month treatment period, and explain to the patient that switching to another medication after treatment (treatment transition) is necessary to prevent bone loss.