PASADENA, Calif.–(BUSINESS WIRE)– Arrowhead Research Corporation (NASDAQ: ARWR), a biopharmaceutical company developing targeted RNAi therapeutics, today announced that it completed dosing healthy volunteers and will begin dosing patients in an on-going phase 1 study of ARC-AAT, the Company’s clinical candidate for the treatment of liver disease associated with Alpha-1 Antitrypsin Deficiency (AATD). AATD is a rare genetic disorder that can severely damage the liver and lungs of affected individuals. The study was designed to begin dose escalation in healthy volunteers (Part A) and transition into patients (Part B) when a predefined knockdown target is achieved. That target is at least 30% reduction of serum AAT levels in 3 subjects or greater than 60% reduction in a single subject. This was met during the third cohort. All three dose levels tested appear to be generally well tolerated and the data safety committee has cleared the study to move into patients with AATD. Dosing in patients may now begin at the highest dose level used in Part A and then continued dose escalation may proceed under the protocol. The company expects to complete the Phase 1 study by the end of 2015.