Arrowhead Research Corporation, a biopharmaceutical company developing targeted RNAi therapeutics, has received regulatory approval to begin a phase IIa clinical trial of ARC-520, its RNAi-based drug candidate for the treatment of chronic hepatitis B virus (HBV) infection.

The Hong Kong Department of Health issued a Certificate for Clinical Trial, allowing the Company to proceed with its planned single-dose study of ARC-520 in two cohorts at two dose levels to be conducted at Queen Mary Hospital and Prince of Wales Hospital in Hong Kong.

A site initiation was completed and patient screening will initiate shortly. The Company expects top line study results to be available in the third quarter of 2014.

The phase IIa study is a multicentre, randomized, double-blind, placebo-controlled, dose-escalation study to determine the depth and duration of hepatitis B surface antigen (HBsAg) reduction after a single intravenous dose of ARC-520 in combination with entecavir in patients with chronic HBV infection. Single doses of ARC-520 will be evaluated at up to two ascending doses of 1.0 mg/kg and 2.0 mg/kg. At each of the two dose levels to be evaluated, a cohort of 8 patients will be enrolled with 6 being dosed with ARC-520 and 2 being dosed with placebo. This study will be conducted in adult male and female patients aged 16 to 65 years, with immune active chronic HBV infection, HBV e antigen (HBeAg) negativity, and ongoing entecavir therapy.

The primary objective of the study is to evaluate the depth and duration of HBsAg decline in response to a single dose of ARC-520 in combination with entecavir. Secondary objectives include evaluation of safety and tolerability and pharmacokinetic (PK) measures. Additional exploratory pharmacodynamics (PD) objectives include evaluation of the effect of ARC-520 on HBV DNA serum titers and antibodies to HBsAg (anti-HBs).

Arrowhead’s RNAi-based candidate ARC-520 is designed to treat chronic HBV infection by reducing the expression and release of new viral particles and key viral proteins. The goal is to achieve a functional cure, which is an immune clearant state characterized by hepatitis B s-antigen negative serum with or without sero-conversion. The siRNAs in ARC-520 intervene at the mRNA level, upstream of where nucleotide and nucleoside analogues act. In transient and transgenic mouse models of HBV infection, a single co-injection of Arrowhead’s DPC delivery vehicle with cholesterol-conjugated siRNA targeting HBV sequences resulted in multi-log knockdown of HBV RNA, proteins and viral DNA with long duration of effect. Arrowhead has completed enrollment in a phase I single ascending dose study in normal volunteers. The company is conducting a single dose phase IIa study in chronic HBV patients, which it expects to follow with a multi dose, multi national phase IIb study. Approximately 350 million people worldwide are chronically infected with the hepatitis B virus. Chronic HBV infection can lead to cirrhosis of the liver and is responsible for 80 per cent of primary liver cancers globally.