Crizotinib, an oral targeted anticancer drug used in the treatment of non-small cell lung cancer, was developed in the early 2000s and later approved for medical use in 2011. Its history is notable for being one of the first successful precision oncology therapies designed specifically for tumors with ALK gene rearrangement, marking a major advancement in targeted cancer treatment. Crizotinib, a tyrosine kinase inhibitor (TKI) that blocks ALK, ROS1, and MET signaling pathways, demonstrated significant clinical effectiveness in ALK-positive NSCLC patients, leading to rapid regulatory approval. However, its clinical use also revealed the development of acquired resistance mutations over time, prompting the creation of next-generation ALK inhibitors for improved long-term disease control.
BRAND NAMES
Crizotinib
Xalkori (original and most widely known brand name)
MECHANISM OF ACTION
Crizotinib is a small-molecule tyrosine kinase inhibitor (TKI) that selectively targets abnormal oncogenic signaling in cancer cells. It inhibits the activity of ALK gene rearrangement, as well as ROS1 and MET receptor tyrosine kinases by competitively blocking ATP binding at their kinase domains.
PHARMACOKINETICS
Absorption
Crizotinib is well absorbed orally, with peak plasma concentrations typically reached within 4 to 6 hours after administration. Its systemic exposure increases more than proportionally with dose, indicating non-linear pharmacokinetics at higher doses.
Distribution
Crizotinib has a large apparent volume of distribution, indicating extensive distribution from the plasma into peripheral tissues. This suggests significant tissue binding and penetration beyond the vascular compartment, consistent with its activity against tumor cells in various organs affected by non-small cell lung cancer.
Metabolism
Crizotinib is extensively metabolized in the liver, primarily by the Cytochrome P450 3A4 system. It undergoes oxidative metabolism followed by phase II conjugation, producing several inactive metabolites.
Elimination
Crizotinib is eliminated primarily through hepatic metabolism, with the majority of the drug and its metabolites excreted in the feces (via biliary excretion), and a smaller proportion eliminated in the urine.
PHARMACODYNAMICS
Crizotinib exerts its pharmacological effects by selectively inhibiting multiple receptor tyrosine kinases, primarily ALK gene rearrangement, as well as ROS1 and MET signaling pathways. By blocking ATP binding to these kinases, crizotinib prevents autophosphorylation and downstream activation of key oncogenic signaling cascades, including the PI3K/AKT and RAS/RAF/MEK pathways.
ADMINISTRATION
Crizotinib is administered orally as a capsule. It is usually taken twice daily (BID), with or without food. The capsules should be swallowed whole and not crushed, chewed, or opened. Treatment is continued until disease progression or unacceptable toxicity occurs in patients with non-small cell lung cancer. Regular monitoring of response and adverse effects is required during therapy.
DOSAGE AND STRENGTH
Crizotinib is available in oral capsule form in strengths of 200 mg and 250 mg, with the 250 mg capsule being the most commonly prescribed. The standard recommended dose is 250 mg taken orally twice daily (BID), with or without food. Treatment is continued until disease progression or unacceptable toxicity occurs in patients with non-small cell lung cancer, and dose modifications may be required based on tolerability or hepatic function.
DRUG INTERACTIONS
Crizotinib is primarily metabolized by the Cytochrome P450 3A4, so it has important drug interaction potential. Strong CYP3A4 inhibitors (such as certain azole antifungals and macrolide antibiotics) can increase crizotinib plasma levels and risk of toxicity, while strong CYP3A4 inducers (such as rifampin or certain anticonvulsants) can significantly reduce its effectiveness.
FOOD INTERACTIONS
Crizotinib has no clinically significant food effect on overall drug exposure, and it can be taken with or without food. However, taking it with meals may sometimes help improve gastrointestinal tolerance in patients with non-small cell lung cancer.
CONTRAINDICATIONS
Crizotinib is contraindicated in patients with known hypersensitivity to crizotinib or any of its formulation components. It should not be used in individuals with a history of severe allergic reactions to the drug.
SIDE EFFECTS
Nausea and vomiting
Diarrhea
Constipation
Visual disturbances (blurred vision, photopsia, trails of light)
Peripheral edema
Fatigue
OVER DOSE
Overdose of Crizotinib may lead to exaggeration of its pharmacologic effects and toxicity, although specific cases are limited. Expected manifestations include severe gastrointestinal symptoms (nausea, vomiting, diarrhea), visual disturbances, marked hepatotoxicity, bradycardia, and QT interval prolongation.
TOXICITY
Crizotinib has a toxicity profile primarily related to its effects on kinase signaling and hepatic metabolism. Dose-related toxicities commonly include hepatotoxicity, gastrointestinal disturbances, and visual disorders, while more serious toxicities include QT interval prolongation, bradycardia, and rare cases of interstitial lung disease (pneumonitis).
