Abbott and Enanta Pharmaceuticals have received positive results from a phase-2 study of ABT-450/r, an investigational, oral protease inhibitor being developed for the treatment of hepatitis C (HCV) infection. Initial three-day and four-week results suggest that ABT-450/r (ABT-450 with 100mg of ritonavir to support once-daily dosing) demonstrates potent antiviral activity in treatment-naïve adults. Results show that more than 90 percent of patients (21 of 23) on study drug achieved HCV-RNA levels <25 IU/mL at four weeks. Results were presented today at the American Association for the Study of Liver Disease annual meeting in Boston.

After three days, treatment with ABT-450/r alone resulted in statistically significant, 4-log mean reductions of HCV RNA, across the three dose ranges of ABT-450 (50mg, 100mg, 200mg, once-daily dosing) compared to placebo.

At week four, 91.3 per cent (21 of 23) of patients receiving ABT-450/r in combination with standard of care (SOC) – pegylated alpha interferon and ribavirin (pegIFN/RBV) – achieved HCV-RNA <25 IU/ml.
 
Safety appears consistent to that expected with SOC - "In spite of the progress that has been made in HCV treatment, limitations in efficacy remain with the current standard of care," Fred Poordad, chief of hepatology at the Liver Disease and Transplant Center at Cedars-Sinai Medical Center in Los Angeles, and one of the investigators for the study. "The initial results of ABT-450/r in patients with HCV suggest that ABT-450/r has favuorable potency in the most common HCV genotype and that ABT-450/r could be an important element in a combination direct-acting antiviral regimen for treatment of HCV."

"Abbott has focused its antiviral research expertise on finding new treatment options for HCV-infected patients that could transform current therapy – by shortening the duration of treatment and increasing cure rates," said Scott Brun, divisional vice president, infectious disease development, Abbott. "We continue to explore the potential for use of ABT-450/r in a variety of combination regimens."

"We are very encouraged by the three-day monotherapy and four-week rapid virologic response results for ABT-450 and we look forward to further clinical results from the program," said Jay Luly, president and chief executive officer, Enanta Pharmaceuticals. "This data is an important step in our HCV programme, and for advancing our broader vision to improve patient care in this field."

The use of Norvir (ritonavir) with ABT-450 for the treatment of HCV is investigational.