US regulators are refusing to file Celgene’s application to market its experimental multiple sclerosis therapy ozanimod.

The US Food and Drug Administration concluded that the nonclinical and clinical pharmacology sections in the New Drug Application were insufficient to permit a complete review.

Celgene said it intends to seek immediate guidance to determine what additional information will be required to resubmit the application.

"We remain confident in ozanimod's clinical profile demonstrated in the pivotal program in relapsing forms of multiple sclerosis," said the firm’s chief medical officer Jay Backstrom.

“We will work with the FDA to expeditiously address all outstanding items and bring this important medicine to patients.”

Ozanimod is a novel, oral, selective, sphingosine 1-phosphate 1 (S1PR1) and 5 (S1PR5) receptor modulator in development for immune-inflammatory indications, including relapsing multiple sclerosis, ulcerative colitis and Crohn's disease.

Celgene picked up rights to ozanimod when it bought Receptos for $7.2-billion back in 2015.