Merck KGaA is firmly back in the race to get an oral multiple sclerosis treatment onto the market after regulators in the USA said they will now accept a filing for the German firm’s cladribine and grant it a speedy review.

In November last year, the US Food and Drug Administration a ‘refuse to file’ letter for Merck's New Drug Application for cladribine, saying it was “not sufficiently complete to permit a substantive review”. However the agency now appears to be satisfied with the re-submission made on June 8 and the drug has been granted a priority review designation.

This means that the review on cladribine should take six months instead of the standard ten. Therefore, Merck expects a decision by the FDA in the fourth quarter and the agency’s decision “is a critical milestone on the path to potential approval for short-course therapy with cladribine”, said Fereydoun Firouz, head of Merck’s EMD Serono unit in the USA.

The FDA has already granted priority review status to Novartis’ rival oral MS drug fingolimod. That file was accepted in January and in June the agency’s Peripheral and Central Nervous System Drugs Advisory Committee recommended approval of fingolimod, also known as FTY720, putting the Swiss major in pole position to be the first firm to get an oral MS pill onto the US market.

Merck is still in there fighting though and earlier this month, regulators in Russia gave the green light to cladribine, the first worldwide approval for an MS oral drug.