Shares of Arrowhead Research (ARWR) were up more than 20% after announcing positive phase 2a trial results for Hepatitis B patients. In addition, the company reported pre-clinical results for treating chimpanzees that have the Hepatitis B virus. One thing to note though is that the chimpanzee study used the company's Hepatitis B treatment, known as ARC-520, together with some nucleotide/nucleoside inhibitors -- NUCs. 

HBV E-antigen positive patients that took a combo of  4 mg/kg ARC-520 and a NUC such as entecavir saw an average gene knockdown of 92% -- 1.2 log. On the other hand, the combination saw a maximum gene knockdown of 98% -- 1.7 log. 

In terms of the chimp study the company reported that four chimps with the Hepatitis B positive e-antigen demonstrated a 99% gene reduction -- 2 log -- by taking 6 to 11 monthly doses of ARC-520. On the other hand four chimps  taking the Hep B negative e-antigen saw an 81% gene reduction -- 0.7 log. One chimp which transitioned from Hep B positive e-antigen to Hep B negative e-antigen saw an 87% gene knockdown -- 0.9 log. 

The safety of ARC-520 looks promising  as 84 trial patients -- humans -- have already received this drug therapy from Arrowhead and there have been no serious adverse events reported to date. In addition, there have been no patient discontinuations from the trial due to any reported adverse events. 

The gene knockdowns observed in these trials are a good start. Now we will have to see if multi-dose trials allowed on humans could observe greater gene knockdown. For now it seems that Arrowhead is on the right path for being in a phase 2a trial. With further refinement of the dosing and possible multi-dosing in humans some type of functional cure may eventually be possible for Hep B patients.