I draw a distinction between: a) ritonavir boosting to convert a BID/TID drug into a qD drug; and b) ritonavir boosting to try to salvage a drug that has a small (or nonexistent) therapeutic window.
What ITMN is doing with ITMN-191 falls within case b, and that’s why I’m skeptical of the outcome.
Based on the trial cited in your post, ABT-072 is evidently still a viable candidate. I wasn’t sure if it was because: i) ABT stopped mentioning ABT-072 by name in its PR’s; and ii) the only ABT-072 trial at clinicaltrials.gov other than the one you cited is a “resistance assessing” trial (http://clinicaltrials.gov/ct2/show/NCT00872196 ), which may be an indication that there are problems.
[ABT-450 is a protease inhibitor that requires boosting with ritonavir to enable qD dosing. The completed phase-1b study tested the usual 3 days of “monotherapy.” The phase-2a study in progress is testing ABT-450/r + SoC for 12 weeks followed by SoC alone for 36 weeks vs a control arm of SoC for 48 weeks; this PR reports 4-week data in which 91% of patients on ABT-450/r + SoC achieved an RVR.
All told, my assessment of ABT-450 is that it’s a day late and a dollar short; the requirement for ritonavir boosting does not help.]
ABBOTT PARK, Ill. and WATERTOWN, Mass., Nov. 1, 2010 /PRNewswire-FirstCall/ -- Abbott (NYSE:ABT) and Enanta Pharmaceuticals today announced 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 3-day and 4-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.
Key findings:
• 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 percent (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, M.D., 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 favorable 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, M.D., 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 3-day monotherapy and 4-week rapid virologic response results for ABT-450 and we look forward to further clinical results from the program," said Jay Luly, Ph.D, president and chief executive officer, Enanta Pharmaceuticals. "This data is an important step in our HCV program, and for advancing our broader vision to improve patient care in this field."
Study Objectives and Design
The objectives of the 48-week Phase 2 study are to assess the safety, tolerability, pharmacokinetics, and antiviral activity of multiple dose strengths of ABT-450/r in treatment-naïve adults infected with HCV genotype 1, which is the most common and difficult to treat form of the infection in the developed world. Trial endpoints include early virologic response and rapid virologic response. Initial antiviral activity was evaluated via a 3-day treatment period during which ABT-450/r was administered alone. Subsequently, ABT-450/r was administered with pegIFN/RBV (SOC) for 12 weeks, followed by treatment with SOC alone for an additional 36 weeks. Participants are then monitored post therapy for 24 weeks for sustained virologic response.
ABT-450 was discovered as part of an alliance between Abbott and Enanta and is being developed with low-dose ritonavir, which enhances the pharmacokinetic properties of ABT-450, allowing for once-daily dosing. This Phase 2 study also evaluated ABT-333 and ABT-072, two of Abbott's internally discovered compounds that are part of the company's ongoing non-nucleoside polymerase inhibitor development program. The study findings for these two compounds have been submitted for presentation at a future scientific meeting.‹