tucatinib: clinical use

Prescribing considerations

• Initiate and supervise treatment within a specialist systemic anti-cancer therapy service.
• Review all medicines and herbal products for CYP2C8, CYP3A and P-glycoprotein interactions.
• Severe hepatic impairment requires product-specific adjustment and specialist oversight.
• Assess the combined toxicity profile of tucatinib, trastuzumab and capecitabine.

Contraindications and cautions

• Hypersensitivity to tucatinib or any tablet excipient.
• Use particular caution with hepatic impairment, significant diarrhoea, pregnancy risk and interacting medicines.
• Consider the sodium and potassium content in relevant restricted diets or renal impairment.

Monitoring

• Check ALT, AST and total bilirubin regularly and when clinically indicated.
• Monitor bowel symptoms, hydration, blood pressure and renal status if diarrhoea occurs.
• A creatinine rise may reflect inhibited tubular secretion rather than reduced glomerular filtration; consider cystatin C or other non-creatinine markers when clinically appropriate.
• Verify pregnancy status before initiation where relevant.

Clinical pharmacology

Tucatinib is a reversible, selective HER2 tyrosine kinase inhibitor. It is metabolised mainly by CYP2C8, with lesser CYP3A and aldehyde oxidase involvement, and is eliminated predominantly through the hepatobiliary route. It strongly inhibits CYP3A and inhibits P-glycoprotein and renal transporters involved in metformin and creatinine handling.

Formulation and product differences

• The selected product is a round, yellow, film-coated tablet debossed with “TUC” and “50”.
• Tablets must remain intact and should not be chewed, crushed or split.
• The formulation contains sodium and potassium and requires no special storage conditions.

Tablet

Route: Oral

Strengths: 50 mg, 150 mg