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Cancer Immunotherapy Pembrolizumab Expected to Be Approved Soon

Companies race to develop similar treatments

According to a report from Reuters, the FDA is likely to approve the highly anticipated immuno-oncology drug pembrolizumab (Merck) as a treatment for melanoma ahead of a late October deadline.

Pembrolizumab is an investigational selective, humanized monoclonal anti-programmed death receptor-1 (PD-1) antibody designed to block the interaction of PD-1 on T-cells with its ligands, PD-L1 and PD-L2, to reactivate anti-tumor immunity. Pembrolizumab exerts dual ligand blockade of the PD-1 pathway.

The biologics license application (BLA) for pembrolizumab is currently under priority review at the FDA for the treatment of patients with advanced melanoma previously treated with ipilimumab (Yervoy, Bristol-Myers Squibb); the Prescription Drug User Fee Act (PDUFA) date is October 28, 2014. The drug was granted the FDA’s “breakthrough therapy” designation for advanced melanoma. If approved, pembrolizumab has the potential to be the first PD-1 immune checkpoint modulator approved in this class.

Besides Merck, other companies, including Bristol-Myers Squibb, Roche Holding AG, and AstraZeneca, are working to develop similar treatments for a variety of cancers.

In a phase Ib study (KEYNOTE-001), pembrolizumab was evaluated as monotherapy in 411 patients with advanced melanoma. The estimated overall survival (OS) rate at 1 year was 69% for all patients, including 74% in patients without prior ipilimumab therapy (current standard therapy) and 65% in patients who had progressive disease during or following treatment with ipilimumab. At 18 months, the estimated OS was 62%.

The median progression-free survival (PFS), as defined by Response Evaluation Criteria in Solid Tumors (RECIST), was 5.5 months overall, including 5.6 months in patients with no prior ipilimumab therapy and 5.4 months in patients who had progressive disease during or after ipilimumab therapy.

The most common investigator-assessed, treatment-related adverse events with pembrolizumab included fatigue (36%), pruritus (24%), rash (20%), diarrhea (16%), arthralgia (16%), nausea (12%), vitiligo (11%), asthenia (9%), and cough (9%). The most common immune-related adverse events included hypothyroidism (8%) and hyperthyroidism (1%). Twelve (3%) treatment-related cases of pneumonitis were reported, including one grade-3/4 event. The most common grade-3/4 treatment-related adverse event was fatigue (2%). Overall, 17 patients (4%) discontinued treatment because of investigator-assessed, treatment-related adverse events. No treatment-related deaths were reported.

The findings were presented in June 2014 at the 50th annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago.

Sources: Reuters; August 25, 2014; and Merck; June 2, 2014.

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