Regulus Plummets After Reported Continuation Of RG-101 Clinical Hold

Shares of Regulus Therapeutics Inc RGLS, a biopharmaceutical company that develops medicines targeting microRNAs, were trading lower by nearly 40 percent ahead of Monday's market open.

Regulus received a written communication from the U.S. Food and Drug Administration that the clinical development for the company's RG-101 remains on clinical hold.

RG-101 is Regulus' wholly-owned lead product candidate is a GalNAc-conjugated anti-miR targeting miR-122 for the treatment of hepatitis C virus (HCV) infection. miR-122 is the he most abundant miR in the liver and is essential for HCV stability.

Regulus' completed Phase 1 clinical study in February of 2015 showed that treatment with a single subcutaneous dose of either 2 mg/kg or 4 mg/kg of RG-101 as monotherapy resulted in significant and sustained viral load reductions in all treated HCV patients, including patients with difficult to treat genotypes, various liver fibrosis status and those who have experienced viral relapse after a prior IFN-containing regimen.

However, in June 2016, RG-101 was placed on clinical hold following the company's submission of a second serious adverse event of jaundice. The company then submitted a complete response to the FDA's request for information and a proposal to mitigate the risk.

On Friday, the company confirmed the clinical development program remains on clinical hold and the FDA. The agency also requested final safety and efficacy data from on-going RG-101 clinical and pre-clinical studies before reconsidering the clinical hold.

Regulus expects the requested data to be available in the fourth quarter of 2017.

"While we are disappointed that the clinical hold was not lifted at this time, we plan to continue to work with the FDA to address their additional requests as we seek the removal of the clinical hold," Dr. Timothy Wright, Chief R&D Officer of Regulus said in a press release.

Analysts at SunTrust and Needham both downgraded Regulus Therapeutics' stock, which traded recently at $1.61, down about 29 percent.