Eli Lilly and Incyte are facing more complications in the US approval of their experimental rheumatoid arthritis (RA) drug baricitinib after the FDA raised concerns over its safety in a resubmission of data following rejection last year.

According to the US regulator, the new data provided did little to assuage worries compared to the original batch. It suggested that the lower 2mg dose of the drug is safe, but called into question the additional benefit of the higher 4mg dose, but even the lower dose suffered from limited data, making an accurate risk/benefit analysis difficult.

The FDA’s concerns have given rise to a fear that they could impact other Janus kinase (JAK) inhibitors, but the agency noted that the dangers presented – namely, thrombosis risk – were specific to baricitinib and have not been seen in comparable products. The concerns pose a real risk to an approval of the drug in the US.

The pair of firms are looking to launch the drug to carve out a slice of the lucrative RA market, the same space occupied by Abbvie’s Humira, the best-selling prescription medicine in the world.  

A robust evaluation is due to be made by an independent panel of experts in an advisory committee meeting on Monday, 23 April.

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