Lorlatinib is a targeted medicine that blocks abnormal signaling from anaplastic lymphoma kinase (ALK). In ALK-positive NSCLC, abnormal ALK activity can contribute to uncontrolled cancer-cell growth.
By inhibiting ALK, lorlatinib interferes with a signaling pathway that cancer cells can depend on.
Detailed mechanism
ALK is a receptor tyrosine kinase. Genetic rearrangements involving ALK can create abnormal signaling proteins that promote proliferation and survival of cancer cells.
Lorlatinib binds to ALK and inhibits its kinase activity. Pfizer developed the molecule with the goal of inhibiting ALK mutations associated with resistance to earlier ALK inhibitors.
Central nervous system activity
A major pharmacologic feature of lorlatinib is its ability to penetrate the blood-brain barrier. This is clinically relevant because ALK-positive NSCLC can involve the brain, either at diagnosis or during treatment.
The CROWN study demonstrated substantial intracranial activity. At five years, the probability of remaining free of intracranial progression was 92% with lorlatinib compared with 21% with crizotinib in the overall treatment-naïve study population.
Resistance mutations
Cancer cells may acquire molecular changes that reduce sensitivity to earlier ALK inhibitors. Lorlatinib was designed to retain activity against several clinically relevant resistance mutations.
Why multi-level inhibition matters
ALK signaling is not limited to a single anatomical site. A treatment that can inhibit ALK in systemic disease while also reaching the central nervous system may be particularly relevant in ALK-positive NSCLC with brain involvement.
This does not mean lorlatinib is appropriate for every person with NSCLC. ALK testing and the applicable regulatory indication remain essential.