ABBOTT PARK, Ill. ( TheStreet) -- A combination regimen of oral hepatitis C drugs developed by Abbott ( ABT) achieved near-perfect cure rates in patients new to treatment. Cure rates were almost as strong in patients who failed previous therapy, making them among the hardest to treat. With cure rates of 99% following a 12-week regimen of oral drugs, Abbott stamps itself as a strong challenger to Gilead Sciences ( GILD) in the rapidly evolving race to develop potent, interferon-free regimens for hepatitis C. Abbott shares rose more than 3% to $71.60 following the release of the hepatitis C data. The new Abbott data announced Monday come from a large, phase II study known as "AVIATOR" that was designed to assess the efficacy and safety of various combinations of oral hepatitis drugs in treatment-naive patients as well as hard-to-treat "null" responders. The Abbott drugs studied in AVIATOR were ABT-450, a protease inhibitor that requires blood-boosting with ritonavir; ABT-267, a NS5A inhibitor; and ABT-333, a "non-nuc" polymerase inhibitor. Ribavirin, a current backbone in hepatitis C treatment, was also included in some but not all of the combination regimens. A 12-week regimen consisting of all three Abbott drugs plus ribavirin demonstrated "observed" SVR12 rates of 99% (76/77) in treatment-naive patients and 93% (38/41) in null responders. SVR12 is the scientific jargon for a cure and measures the percent of patients who have undetectable hepatitis C virus in their system 12 weeks after treatment ends. The "observed" SVR12 results omit two treatment-naive patients and four null responder patients with either missing data or inadequate follow-up. If those patients were included and all failed to achieve an SVR12 cure -- a worst-case scenario -- the treatment-naive and null responder cure rates would drop to 96% and 84%, respectively. Sixty-six percent of the patients enrolled in the Abbott study has genotype 1A virus, considered more resistant to treatment than genotype 1b. Similarly, 70% of patients had unfavorable "non-CC" genetics. The AVIATOR study also treated patients with regimens consisting of two (not three) Abbott drugs with ribavirin, some with shortened treatment to eight weeks (not 12 weeks.) SVR12 cure rates in these various arms of the study ranged from 89-92%, Abbott announced. More detailed data from the AVIATOR study will be presented in November at the American Association for the Study of Liver Disease (AASLD) annual meeting.