Celgene's JAK2 inhibitor Inrebic garners FDA approval for myelofibrosis

The FDA on Friday approved Celgene's JAK2 inhibitor Inrebic (fedratinib) to treat adults with intermediate-2 or high-risk primary or secondary myelofibrosis. The company gained the drug last year as part of its acquisition of Impact Biomedicines under a deal potentially worth up to $7 billion. 

"Prior to today, there was one FDA-approved drug to treat patients with myelofibrosis," noted Richard Pazdur, acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, referring to Incyte's JAK 1 and 2 inhibitor Jakafi (ruxolitinib), which first gained clearance in the US in 2011 to treat certain patients with the disease. 

Approval of Inrebic was supported by the results of its clinical programme involving 608 patients with myelofibrosis. Data from the Phase III JAKARTA study showed that the therapy reduced spleen volume by at least 35% in 37% of patients, while symptom scores were improved by 50% or more in 40% of patients. Meanwhile, updated results from the Phase II JAKARTA2 study of patients who had been previously treated with Jakafi, demonstrated that among the 97 participants making up the intent-to-treat (ITT) population, 31% of those in the Inrebic group had a decrease in spleen volume of at least 35%. Meanwhile, the response rate of the 79 patients in this group who were also resistant or intolerant to Jakafi was 30%, "consistent with the response rate observed in the ITT population," Celgene said.

Inrebic comes with a boxed warning for serious and fatal encephalopathy, including Wernicke's. In 2013, Sanofi halted development of the therapy after it was linked to "cases consistent with Wernicke's encephalopathy," with the FDA placing a clinical hold on studies of the drug. Impact Biomedicines bought full rights for the global development and commercialisation of the treatment from Sanofi in 2016, and the FDA lifted the clinical hold in 2017.

The therapy, which was assessed under a priority review, also has an orphan drug designation by the FDA for the treatment of primary or secondary myelofibrosis. 

Celgene is in the process of being acquired by Bristol-Myers Squibb for $74 billion. Bristol-Myers Squibb, which has said it expects the transaction to be completed by the end of 2019 or in early 2020, received unconditional approval of the pending transaction from the European Commission last month.   

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