Regulus share price halves as FDA holds up studies on hep C drug

The US Food and Drug Administration has placed a clinical hold on studies of the Regulus Therapeutics (Nasdaq: RGLS) drug RG-101 for the treatment of chronic hepatitis C virus (HCV).

Shares in the US microRNAs biotech firm dropped by 49.3% on Tuesday after it revealed receipt of the FDA’s verbal notice, which will be followed by a formal clinical hold letter from the agency within 30 days.

The FDA initiated the clinical hold after Regulus reported a second serious adverse event of jaundice in an HCV patient with end-stage renal disease on dialysis who was enrolled in the company’s ongoing Phase I US study, occurring 117 days after receiving a single dose of RG-101.