11/9/2016 5:52:32 AM
November 9, 2016
By Alex Keown, BioSpace.com Breaking News Staff
PASADENA, Calif. – Shares of Arrowhead Pharmaceuticals (ARWR) are down more than 26 percent this morning after the company’s experimental hepatitis B drug, ARC-520, was placed on clinical hold by the U.S. Food and Drug Administration (FDA).
The regulatory agency called for the hold on the Phase IIb Heparc-2004 trial so Arrowhead could provide answers to questions from a nonclinical toxicology study in non-human primates using EX1, the company’s liver-targeted, intravenously administered delivery vehicle. The company said the hold was prompted following the death of primate study subjects at the highest doses of EX1.
In an announcement this morning, Arrowhead said the FDA did not indicate the hold was based on any problems with human patients. Arrowhead added that it has not received written notification of the clinical hold, but did receive verbal communication about the concerns. The Phase IIb human trial does not involve doses as high as those administered in the primate study. Arrowhead said the experimental drug has been given more than 800 times to more than 300 “human study subjects and patients.” Out of those patients, Arrowhead said there have only been three serious adverse events observed. Two were fevers which were treated and the patients resumed the treatment, the company said. The other incident was an instance of hepatic carcinoma in a patient with chronic HBV and cirrhosis, judged by the treating physician to be unrelated to the drug. The EX1 delivery vehicle is used in the company’s ARC-520, ARC-521, and ARC-AAT programs.
Heparc-2004 is a multicenter, randomized, double-blind, placebo-controlled, multi-dose study of ARC-520, which is currently being performed in up to 12 patients in the United States under an Investigational New Drug Application. ARC-520 intervenes upstream of the reverse transcription process where current standard-of-care nucleotide and nucleoside analogs act, and is designed to silence the production of all HBV gene products. The small interfering RNAs (siRNAs) in ARC-520 engage the body’s normal cellular RNAi machinery and direct specific cleavage of HBV RNA transcripts, thereby reducing the levels of HBV proteins and the RNA template used to produce viral DNA, according to Arrowhead’s website.
The clinical hold comes on the heels of a deal Arrowhead struck with Amgen as part of a deal to develop and commercialize RNA interference (RNAi) therapies for cardiovascular disease. Arrowhead is developing its RNAi ARC-LPA program. The engineered molecules are designed to reduce elevated lipoprotein(a), which is a genetically validated, independent risk factor for atherosclerotic cardiovascular disease. The Amgen deal could be worth up to $673 million for Arrowhead.
Arrowhead is trading at $4.51 per share this morning, down from its previous close of $6.11.
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