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Preliminary Phase I Data on Arrowhead HBV Drug Positive, Company Prices Offering


Arrowhead Research this week announced that it has completed enrollment in a phase I trial of its siRNA-based hepatitis B treatment ARC-520, and that available data indicate that the compound is safe to advance into a planned phase IIa study.

Separately, the company disclosed that it has priced its planned $60 million private offering.

ARC-520 comprises two distinct siRNAs targeting highly conserved genomic regions across the major HBV genotypes, and is formulated with a proprietary delivery technology called dynamic polyconjugates, or DPCs. The program was acquired from Roche when Arrowhead bought its RNA drug assets in late 2011 (GSN 10/27/2011).

This summer, Arrowhead advanced the drug into the phase I trial, which enrolled 36 healthy volunteers. Twenty-four individuals received single doses of the drug ranging from .01 mg/kg to 2 mg/kg, and 12 received placebo.

All subjects received their full, assigned dose and there were no discontinuations for adverse events or otherwise, Arrowhead said, and no adverse events have been reported by any subject to date.

The firm added that preclinical data suggest that any clinically significant or dose-limiting toxicities would be observed within the first 48 hours after the drug was administered.

"The anticipated organs of interest for potential toxicity and the resultant chemistries are liver, kidney, and muscle," Arrowhead said. However, laboratory tests have not indicated toxicity in any of these organs in any study subject.

The study remains blinded and follow-up is ongoing, the company added. Additional data will be released when they become available.

However, Arrowhead said that the blinded data supports the start of a single-dose phase IIa trial in HBV patients in Hong Kong, for which regulatory clearance is being sought.

Meanwhile, Arrowhead said that it will sell about 3.1 million shares of its common stock at $5.86 and 46,000 newly issued shares of non-voting convertible preferred stock at $1,000. The preferred stock is convertible into shares of common stock at $5.86 apiece, pay no dividend, and include no liquidation preference.

Arrowhead's shares were trading around $6.58 as of midday Tuesday.

The offering is set to close this week.