Arrowhead sneaks out pre-election clinical hold news on hep B candidate

Late last night, seemingly in an effort to minimize exposure to the news as the U.S. election dominates, small cap Arrowhead Pharmaceuticals ($ARWR) announced that the FDA has hit the biotech with a clinical hold for a small test of its hepatitis B med ARC-520, which has previously been touted as a possible cure for the infection.

The Heparc-2004 study, which is being conducted in 12 patients, will now be halted “while the company provides responses to questions arising from a nonclinical toxicology study in non-human primates using EX1, the company’s liver-targeted, intravenously administered delivery vehicle,” it said in a statement.

The biotech stressed however that the FDA “did not indicate the clinical hold was based on any human findings.”

It’s not yet been given a formal written notice, but in the verbal notice from the FDA, the clinical hold was prompted by deaths at the highest dose of an ongoing, nonhuman primate toxicology study.

Arrowhead said that this study involves “higher doses of EX1 than those used clinically in humans” and “higher than those” used in the company’s previous animal toxicology studies. The cause of these animal deaths is unknown, but the biotech believes the findings in animal toxicology studies are related to dose level.

The biotech was hit this morning on the news, with its shares trading down around 20% premarket. 

ARC-520 is designed to work upstream of the reverse transcription process, where current standard-of-care nucleotide and nucleoside analogs act.

It is intended to silence the production of all HBV gene products. The small interfering RNAs (siRNAs) in ARC-520 aim to reduce the levels of HBV proteins and the RNA template used to produce viral DNA.

Back in August the California biotech said it had raised $45 million in cash through a series of investors to help bolster its R&D war chest. This came after it struck a $674 million cardiovascular RNAi pact with Amgen ($AMGN) back in September.

The company is working on developing a number of gene-silencing techniques, with much of its RNAi assets bought from Novartis in a $35 million deal that saw it grab the rights to three preclinical candidates.

In 2011, it bought out Roche’s ($RHHBY) RNAi platform as this tech moved out of Big Pharma and into smaller biotech.

Arrowhead has for some time been locked in a rivalry with fellow RNAi specialist Alnylam ($ALNY) to get their RNAi meds onto the market first.

Alnylam has had its own troubles, losing around a half-billion dollars in market cap in trading in late September on the news that it halted development of RNAi liver disease candidate ALN-AAT after a Phase I/II study resulted in three patients with liver enzyme elevation at the highest dose.