(Adds details, background, updates share movement)
Jan 12 (Reuters) - Drug developer Arrowhead Research Corp said the U.S. Food and Drug Administration placed thecompany's experimental hepatitis B treatment on partial clinicalhold, seeking additional data from the drug's mid-stage study.
The company's shares plunged 22 pct premarket on Mondayafter the FDA also asked the company to reduce the dosage of thedrug, ARC-520.
The FDA requested Arrowhead to begin the multiple-dose trialfor the drug at 1mg/kg - much lower than the company's proposed2 mg/kg and 4 mg/kg.
The regulator also requested additional information onpatients who received 1-4 mg/kg of the drug in the ongoingsingle-dose mid-stage trial and report from the ongoingmultiple-dose non-clinical study.
Arrowhead said its ongoing mid-stage trial would continue asplanned and that it expected to file with Asian and Europeanagencies to begin additional mid-stage studies in coming weeks.
Arrowhead's shares jumped 66 percent in the 30 days throughFriday's closing, in part due to speculation that the companycould be a takeover target for larger drugmakers.
Shares of the Pasadena, California based company closed at$9.06 on Nasdaq on Friday. (Reporting by Anjali Rao Koppala in Bangalore; Editing bySaumyadeb Chakrabarty)