The U.S. FDA kept its clinical hold on Regulus Therapeutics Inc.'s clinical development program for RG-101 for the treatment of hepatitis C virus.

The drug was placed on clinical hold in June 2016 after Regulus' submission of a second serious adverse event of jaundice.

Regulus submitted a complete response to the FDA's initial request for information in 2016, which included identification of a potential mechanism of hyperbilirubinemia. It also submitted a proposal to mitigate this risk.

Subsequently, the FDA requested the final safety and efficacy data from ongoing clinical and pre-clinical studies for the drug before reconsidering the clinical hold. The FDA also requested additional expert review of liver safety data due to the proposed mechanism of hyperbilirubinemia.