Arrowhead updates TheStreet on clinical trial results of RNAi candidate for hepatitis B

Arrowhead Research reported Aug. 12 that patients in its Phase II clinical trial of the ARC-520 RNA interference candidate for hepatitis B had a "similar" knockdown to those reported in primate studies. The stock price bounced around a bit as investors considered the somewhat vague declaration, but fell at the very end of the trading day to close at $12.00 from an opening-day price of $13.00.

The knockdown (a metric measuring reduction of the virus in a patient's body) in chimpanzee studies was log 0.8; investors were expecting a reduction in the log 1.0 range, says TheStreet's Adam Feuerstein.

In addition, Arrowhead said that the duration of the knockdown was longer than in nonhuman primates and continued after 8 weeks, which is the most recent time point available. The company also said that the candidate appears safe and has not resulted in any serious adverse events so far. Dosing is also being considered in the trial. Dosing of 1 mg/kg and 2 mg/kg have been tested so far, and tests of the 3-mg/kg dose are under way, with the blessing of an institutional review board.

ARC-520 is designed to switch off production of hepatitis B genes using Arrowhead's Dynamic Polyconjugates delivery platform, with the hopes that the patient's immune system can fight off the remaining virus. It is the farthest along of the company's three RNAi candidates. The non-RNAi, anticancer small molecule Cyclosert is also in Phase II.

Arrowhead, based in Pasadena, CA, reported a net loss of $11.6 million in Q3 of fiscal year 2014 and cash on hand of $188.5 million, up from $29.8 million in September 2013.

The stock's volatility continues. Reflecting the uncertainty surrounding the still-unproven RNAi delivery technique, Arrowhead stock has risen about 50 cents to $12.50 in the first hour of today's market session on heavy trading.

- read the release
- here's TheStreet's take
- get more information about the delivery platform

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