Tucatinib – Highly Selective HER2 Tyrosine Kinase Inhibitor

Tucatinib is a highly selective oral tyrosine kinase inhibitor of the HER2 protein (Human Epidermal Growth Factor Receptor 2). The drug represents a new generation of targeted therapy with exceptional specificity: it acts directly on the HER2 kinase domain, having minimal effect on the related EGFR receptor. This allows for the minimization of typical EGFR-related side effects, such as severe diarrhea and skin rash, while providing potent suppression of HER2-positive tumor cell growth.

The mechanism of action of tucatinib is based on blocking signaling pathways for cell proliferation and survival (MAPK and PI3K/AKT). One of the key clinical features of the drug is its high ability to cross the blood-brain barrier. This makes tucatinib a critical component in the treatment of patients with HER2-positive breast cancer who have brain metastases — a condition that was previously extremely difficult to treat with systemic therapy. When used in combination with trastuzumab and capecitabine, tucatinib demonstrates a significant increase in overall survival and time to disease progression. The drug works effectively even after the tumor has developed resistance to other anti-HER2 therapies, such as antibodies or conjugates.

The drug is taken orally twice daily. Therapy requires mandatory confirmation of HER2 overexpression or ERBB2 gene amplification in the tumor tissue.

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Tucatinib

Indications

Tucatinib is indicated for use in combination with trastuzumab and capecitabine in adult patients:

  • HER2-positive Breast Cancer: treatment of locally advanced or metastatic cancer, including patients with brain metastases.
  • Prior Therapy: use in patients who have received one or more prior anti-HER2-based regimens for metastatic disease.
  • HER2-positive Colorectal Cancer: in combination with trastuzumab for the treatment of metastatic colorectal cancer after progression on standard chemotherapy (in certain jurisdictions).

Dosage and administration

The tucatinib dosing regimen requires strict adherence to intervals between doses to maintain therapeutic concentrations.

  • Standard Dose: 300 mg twice daily (two 150 mg tablets).
  • Administration Method: tablets are taken orally whole, regardless of food intake, every 12 hours.
  • Missed Dose: if a dose is missed, wait for the next scheduled dose. Do not take an extra dose to compensate for the missed one.
  • Duration: therapy is continued until disease progression or unacceptable toxicity occurs.
  • Dose Adjustment: if severe side effects develop, the dose is reduced to 250 mg, 200 mg, or 150 mg twice daily.

The use of tucatinib has the following medical restrictions:

  • Hypersensitivity: known allergy to tucatinib or any drug components.
  • Severe Hepatic Impairment: patients with Child-Pugh Class C require an initial dose adjustment (to 200 mg twice daily).
  • Pregnancy and Lactation: the drug has teratogenic potential; breastfeeding should be discontinued during treatment and for one week after the last dose.
  • Drug Interactions: avoid concomitant use with strong CYP3A inducers or strong CYP2C8 inhibitors.

The side effects of tucatinib most commonly manifest when used in combination with chemotherapy:

  • Digestive System: diarrhea (usually mild to moderate), nausea, vomiting, and stomatitis.
  • Hepatotoxicity: increased levels of ALT, AST, and bilirubin, requiring regular blood test monitoring.
  • Dermatology: hand-foot syndrome (redness and soreness of palms and soles), associated with the combined use of capecitabine.
  • General Symptoms: fatigue, decreased appetite, and joint pain.
  • Hematology: anemia and a decrease in white blood cell counts.

Frequently Asked Questions

Tucatinib is an oral tyrosine kinase inhibitor that is highly selective for the HER2 receptor. Unlike some other medications in its class, it minimally inhibits the EGFR receptor. This selectivity allows for more precise targeting of cancer cells while reducing the risk of side effects typically associated with EGFR inhibition, such as severe skin rash and diarrhea.
Tucatinib is indicated for the treatment of HER2-positive metastatic breast cancer. It is typically administered as part of a "triple" combination therapy along with trastuzumab and capecitabine. This regimen significantly improves survival outcomes for patients whose disease has progressed after previous lines of targeted therapy.
Yes, this is one of tucatinib's primary advantages. The substance is able to cross the blood-brain barrier. Clinical studies have demonstrated that adding tucatinib to a treatment regimen effectively slows tumor growth in the brain and extends survival in patients with active CNS metastases.
Tucatinib is taken twice daily (every 12 hours) with or without food. While tucatinib is generally less toxic to the GI tract than similar drugs, diarrhea frequently occurs when it is used in combination with capecitabine. It is important to have anti-diarrheal medication (such as loperamide) on hand and start taking it at the first sign of loose stools, while also notifying your physician.
Tucatinib can cause elevations in liver enzymes (ALT, AST) and bilirubin, which may indicate liver stress. Your healthcare provider will order blood tests every three weeks, or more frequently at the start of therapy. If significant abnormalities occur, a dose reduction or temporary treatment interruption may be necessary until liver function improves.

List of medicines by active substance

-12%
Tucaxen 150 150 mg Everest
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Everest

Tucaxen 150

Tucatinib
150 mg 30 tablets
49438₴ 56180₴
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