Classification and mechanism of action of Crizotinib/Xalkori targeted drugs

Crizotinib is the world's first targeted therapy drug approved for ALK-positive non-small cell lung cancer (NSCLC), which is a milestone in the history of molecular tumor treatment development. As a type of small molecule tyrosine kinase inhibitor (TKI), crizotinib precisely targets the abnormal protein produced by ALK gene fusion or mutation, thereby blocking the abnormal signaling pathways of tumor cells and inhibiting their proliferation and survival. Compared with traditional chemotherapy, this type of targeted drugs has changed the landscape of lung cancer treatment with higher selectivity and lower systemic toxicity.

From the perspective of drug classification, crizotinib is classified as a first-generationALK inhibitor. Its development logic stems from the discovery of ALK (anaplastic lymphoma kinase) gene rearrangements. The ALK fusion gene has been detected in some patients with non-small cell lung cancer, driving continued cell activation and tumor progression. Crizotinib can bind to the ALK kinase domain and inhibit its downstream signal transduction, such as the PI3K/AKT and MAPK/ERK pathways, thereby cutting off the "signaling network" that cancer cells rely on for survival. It is worth noting that crizotinib also has a certain inhibitory effect on ROS1 and MET kinase, which makes it potentially applicable in patient groups with different genetic backgrounds.

However, first-generationALK inhibitors have limitations in clinical use. The most prominent challenge is the occurrence of drug resistance, which includes insufficient central nervous system (CNS) penetration at the pharmacokinetic level, resulting in poor control of brain metastasis; and also includes mutations in the ALK kinase region at the pharmacodynamic level, which changes the drug binding site and weakens the inhibitory ability. In addition, tumor cells may escape the inhibitory effects of crizotinib by activating the alternative pathway. These problems have driven the development of second- and third-generation ALK inhibitors, such as alectinib, brigatinib, and lorlatinib, which not only improve coverage of drug-resistant mutations but also enhance penetration into the central nervous system, significantly improving treatment persistence and systemic control rates.

The mechanism of action of crizotinib also reflects the core concept of precision medicine. By detecting the ALK status of patients through molecular diagnostic methods, we can screen out the people who are truly suitable for using the drug and achieve "targeted targeting". This strategy of genotyping and drug matching avoids ineffective treatments and unnecessary side effects, and also brings longer progression-free survival and higher quality of life to patients. From the perspective of global oncology research, the success of crizotinib has promoted the path of targeted drugs from the laboratory to the clinic, becoming an important starting point for the continuous upgrading of subsequent generations of ALK inhibitors.

In current clinical practice, crizotinib is still an important option for some ALK-positive patients, especially in areas where drug accessibility and economy are required, and its status cannot be ignored. However, the medical community is more concerned about how to optimize the treatment sequence driven by the new generation of ALK inhibitors, delay the emergence of drug resistance, and achieve comprehensive management by combining immunotherapy, chemotherapy and other strategies. Crizotinib is not only a drug name, but also the opening symbol of the era of precision tumor treatment, laying the foundation for targeted therapy to move from "possibility" to "reality".

Reference materials:https://go.drugbank.com/drugs/DB08865