The Food and Drug Administration (FDA) has approved Xalkori (crizotinib capsules; Pfizer) for the treatment of metastatic non-small cell lung cancer (NSCLC) in patients whose tumors are ROS1-positive. ROS1 rearrangements occur when the ROS1 gene attaches to another gene and changes the way each gene normally functions, which can contribute to cancer-cell growth. This is the second approval for the drug, which was approved in 2011 for the treatment of patients with metastatic NSCLC that is anaplastic lymphoma kinase (ALK)-positive. 

This new approval was based on a multicenter, single-arm trial where patients with metastatic ROS1 rearrangement-positive NSCLC received crizotinib 250mg twice daily.  Fifty patients were enrolled in the study; objective response rate (ORR) and duration of response (DoR) were the efficacy outcome measures. The ORR by independent radiology review (IRR) was 66% (95% CI: 51%, 79%) with a median DoR of 18 months. The ORR according to investigators was 72% (95% CI: 58%, 84%). 

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Safety results of this trial were consistent with the safety profile of the ALK-positive metastatic NSCLC trial which evaluated crizotinib in 1,669 patients. The most common adverse reactions associated with crizotinib therapy include vision disorders, nausea, diarrhea, vomiting, edema, constipation, elevated transaminases, fatigue, decreased appetite, upper respiratory infection, dizziness and neuropathy.

“The approval of crizotinib for metastatic ROS1-positive non-small cell lung cancer represents another significant step forward in biomarker-driven cancer care,” said Dr. Alice Shaw, Associate Professor of Medicine at Massachusetts General Hospital and Harvard Medical School, and principal study investigator. “As with ALK-positive lung cancer, ROS1-positive lung cancer defines a distinct subset of patients for whom crizotinib is efficacious.”

Crizotinib is an inhibitor of receptor tyrosine kinases. The drug received Breakthrough Therapy Designation for the ROS1-positive development program and the application was granted Priority Review. 

An FDA-approved test for the detection of ROS1 rearrangements in NSCLC is not currently available; however, laboratory developed tests are available. A companion diagnostic test is currently under development to identify patients with ROS1-positive metastatic NSCLC who may benefit from treatment with crizotinib.

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