Crizotinib (Xalkori) has been approved by the FDA for patients with ROS1-positive metastatic non-small cell lung cancer (NSCLC), based on substantial efficacy displayed in a phase I study.
The phase I study consisted of 50 patients with ROS1-positive NSCLC, where the overall response rate (ORR) was 66% and the median duration of response was 18.3 months by independent review. The approval was preceded by a breakthrough therapy designation and arrived approximately one month ahead of a deadline set under the Prescription Drug User Fee Act.
“Lung cancer is difficult to treat, in part, because patients have different mutations, some of which are rare,” Richard Pazdur, MD, director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, said in a statement. “The expanded use of Xalkori will provide a valuable treatment option for patients with the rare and difficult to treat ROS-1 gene mutation by giving health care practitioners a more personalized way of targeting ROS-1 positive NSCLC.”
In the phase I trial, 50 patients at a median age of 53 were treated with crizotinib at 250 mg twice daily in a continuous 28-day cycle. A majority of patients had an ECOG performance status of 0 or 1 (98%), had never smoked (78%), and had adenocarcinoma histology (98%). Half of patients were white (54%) and 42% were Asian. The majority of patients (86%) had received previous treatment, with 44% having received more than 1 prior therapy.
In total, ROS1 was detected in approximately 1% of screened patients with NSCLC. The ROS1 rearrangement was confirmed in all but one patient using a break-apart FISH assay, with the remaining patient identified by RT-PCR.
Next-generation sequencing (NGS) of the tumor identified by RT-PCR would later reveal the absence of a ROS1 rearrangement. One patient who tested positive by the break-apart test was found to be ALK-positive but not ROS1-positive by NGS. Additionally, one patient had a coexisting amplification in MET.
In data from study, which were published in The New England Journal of Medicine (NEJM), treatment with crizotinib elicited an ORR of 72% in patients with ROS1-rearranged NSCLC by investigator assessment. The ORR was comprised of 3 complete responses (6%) and 33 partial responses (66%). An additional 9 patients (18%) had stable disease as their best response for an overall disease control rate of 90%.
The median time to first response was 7.9 weeks and the median duration of response was 17.6 months. At the time of the analysis, 64% of patients were still responding to therapy, with a median duration of treatment of 64.5 weeks. The median progression-free survival (PFS) with crizotinib was 19.2 months. At a median follow-up for overall survival (OS) of 16.4 months, the 12-month OS rate was 85%. The median had not been reached.
Crizotinib’s safety profile was similar to previous studies in patients with ALK-rearranged NSCLC. The most common events with crizotinib were visual impairment (82%), diarrhea (44%), nausea (40%), peripheral edema (40%), constipation (34%), vomiting (34%), an elevated aspartate aminotransferase level (22%), fatigue (20%), dysgeusia (18%), and dizziness (16%).
The most common grade 3 adverse events were hypophosphatemia (10%), neutropenia (10%), and an elevated alanine aminotransferase level (4%). Additionally, one patient (2%) discontinued crizotinib because of treatment-related nausea.
Crizotinib was initially granted an accelerated approval for patients with ALK-positive NSCLC in August 2011, which was followed by a full approval in November 2013. The full approval was based on the demonstration of superior PFS and ORR for crizotinib compared with chemotherapy in ALK-positive NSCLC. The median PFS with crizotinib was 7.7 versus 3.0 months with chemotherapy (HR, 0.49; P <.0001). ORR was 65% with crizotinib versus 20% with chemotherapy.