Lapatinib Ditosylate

What it is and how it works

Mechanism of Action Lapatinib is a 4-anilinoquinazoline kinase inhibitor of the intracellular tyrosine kinase domains of both Epidermal Growth Factor Receptor (EGFR [ErbB1]) and of Human Epidermal Receptor Type 2 (HER2 [ErbB2]) receptors (estimated K i app values of 3nM and 13nM, respectively) with a dissociation half-life of greater than or equal to 300 minutes. Lapatinib inhibits ErbB-driven tumor cell growth in vitro and in various animal models. An additive effect was demonstrated in an in vitro study when lapatinib and 5-FU (the active metabolite of capecitabine) were used in combination in the 4-tumor cell lines tested.

Indications

Lapatinib tablets are kinase inhibitor indicated in combination with: capecitabine for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress human epidermal growth factor receptor 2 (HER2) and who have received prior therapy, including an anthracycline, a taxane, and trastuzumab. Limitations of Use: Patients should have disease progression on trastuzumab prior to initiation of treatment with lapatinib tablets in combination with capecetabine. letrozole for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer that overexpresses the HER2 receptor for whom hormonal therapy is indicated. Lapatinib tablets in combination with an aromatase inhibitor has not been compared to a trastuzumab-containing chemotherapy regimen for the treatment of metastatic breast cancer.

Dosage and administration (summary)

The recommended dosage of lapatinib tablets for advanced or metastatic breast cancer is 1,250 mg (5 tablets) given orally once daily on Days 1 to 21 continuously in combination with capecitabine 2,000 mg/m 2 /day (administered orally in 2 doses approximately 12 hours apart) on Days 1 to 14 in a repeating 21- day cycle. The recommended dose of lapatinib tablets for hormone receptor-positive, HER2-positive metastatic breast cancer is 1,500 mg (6 tablets) given orally once daily continuously in combination with letrozole. When lapatinib tablets are coadministered with letrozole, the recommended dose of letrozole is 2.5 mg once daily.

Contraindications

Lapatinib tablets are contraindicated in patients with known severe hypersensitivity (e.g., anaphylaxis) to this product or any of its components. Known severe hypersensitivity (e.g., anaphylaxis) to this product or any of its components.

Warnings and precautions

Decreases in left ventricular ejection fraction (LVEF) have been reported. Confirm normal LVEF before starting lapatinib tablets and continue evaluations during treatment. Lapatinib has been associated with hepatotoxicity. Monitor liver function tests before initiation of treatment, every 4 to 6 weeks during treatment, and as clinically indicated. Discontinue and do not restart lapatinib tablets if patients experience severe changes in liver function tests. Dose reduction in patients with severe hepatic impairment should be considered.

Pregnancy

Pregnancy Risk Summary Based on findings in animal studies and its mechanism of action, lapatinib tablets can cause fetal harm when administered to a pregnant woman . There are no available human data to inform of the drug-associated risks.

Storage and supply

Lapatinib tablets 250 mg are orange colored, oval shaped, film-coated tablets, debossed “NTL” on one side and plain on another side and are available in: Bottles of 150 tablets: NDC 68180-801-36 Store at 25°C (77°F); excursions permitted to 15° to 30°C (59° to 86°F) .

Source: Lapatinib (Lapatinib) — US FDA prescribing information, 2025-06-10, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.