Tucatinib (Tukysa): A Precision Medicine for HER2-Positive Breast & Colorectal Cancer

　　Tucatinib(Tukysa,also known as Tucatinib)is an oral tyrosine kinase inhibitor(TKI)developed by Seagen Inc.,specifically designed to target the HER2 protein.By inhibiting the HER2 signaling pathway,it effectively controls tumor proliferation and metastasis,showing remarkable efficacy in HER2-positive breast cancer and colorectal cancer.Approved by the FDA in 2020 for advanced breast cancer,and in 2023 for RAS-wildtype colorectal cancer.

　　Indications:

　　1.Metastatic Breast Cancer:In combination with trastuzumab and capecitabine,for treatment of unresectable locally advanced or metastatic HER2-positive breast cancer,including patients with brain metastases who have received≥1 prior anti-HER2 regimen.

　　2.Unresectable/Metastatic Colorectal Cancer:Combined with trastuzumab for RAS-wildtype HER2-positive disease progressing after fluoropyrimidine,oxaliplatin,and irinotecan-based therapies.Approval is based on tumor response rate and duration;continued approval contingent on confirmatory trial outcomes.

　　Dosage and Administration:

　　●Recommended Dose:300mg orally twice daily,in combination with designated therapies,continued until disease progression or unacceptable toxicity.

　　●Adjustments for Severe Hepatic Impairment:Reduce to 200mg twice daily for Child-Pugh C patients.

　　●CYP2C8 Inhibitors:Avoid co-administration;if unavoidable,reduce Tucatinib to 100mg twice daily.Resume original dose after 3 half-lives of inhibitor discontinuation.

　　●Administration Guidance:Swallow whole;dose every 12 hours with or without food.Do not replace missed doses;continue scheduled regimen.Avoid if tablet is damaged.

　　Common Adverse Reactions(≥20%):

　　●Breast Cancer Combo:Diarrhea,palmar-plantar erythrodysesthesia,nausea,hepatic toxicity,vomiting,etc.

　　●CRC Combo:Diarrhea,fatigue,rash,abdominal pain,pyrexia,etc.

　　Contraindications:

　　1.Hypersensitivity to Tucatinib or excipients.

　　2.Severe hepatic impairment(Child-Pugh C).

　　3.Pregnancy(embryo-fetal toxicity risk);effective contraception required during treatment and for 1 week post-dose.

　　Precautions:

　　1.Diarrhea Management:Monitor for severe cases;initiate anti-diarrheal therapy and adjust dose as needed.

　　2.Hepatotoxicity:Baseline and every 3 weeks monitor ALT/AST/bilirubin;withhold,reduce,or discontinue based on severity.

　　3.Reproductive Risk:Animal data suggest fetal harm;advise contraception for females and males with female partners of childbearing potential.

　　4.Special Populations:

　　○Lactation:Avoid breastfeeding during treatment and 1-week post-dose.

　　○Pediatrics:Safety not established.

　　○Geriatrics:Safety similar in≥65-year-olds;limited data for≥75-year-olds.

　　○Renal Impairment:No adjustment needed for mild/moderate impairment;avoid in severe impairment(CrCl<30 mL/min)due to capecitabine contraindication.

　　Pharmacokinetics:

　　●Absorption:Median Tmax≈2 hours;food has minimal clinical impact.

　　●Metabolism:Primarily via CYP2C8,partly CYP3A.

　　●Elimination:86%fecal(16%unchanged),4%renal;half-life≈11–16 hours.