Findings from a Phase IIb trial of Boehringer Ingelheim’s faldaprevir and deleobuvir demonstrated strong efficacy in hepatitis C genotype-1 patients, without interferon. The results, reported last Thursday in The New England Journal of Medicine, may bode well for the BI regimen in a specific population.

The overall data show that in genotype 1a and 1b, 85% of patients taking faldaprevir and deleobuvir, formerly known as BI-207127, showed sustained virologic response at 12 week (SVR12). Genotype 1a results were less impressive, with SVR12 rates reaching 47%.

Genotype one accounts for 75% of the HCV population and remains the most difficult segment to treat. What could potentially detrail faldaprevir’s future success in HCV is Gilead’s contender, and the all-out oral front runner: sofosubvir.

Although sofosbuvir’s anticipated approval—which could be as early as December 2013—is only for genotypes 2 and 3, the drug is expected to be used in tandem with ledipasvir and ribavirin for off-label usage in genotype 1, according to inThought analyst Julie Hoggatt. Sofosbuvir was filed with the FDA in April 8, and Gilead plans to file in Europe later this year.

So far, Gilead’s genotype 1 research, specifically its phase II LONESTAR study, has shown that sofosbuvir plus ledispavir was associated with up to 100% cure rates in genotype 1 up to eight weeks after treatment stopped (SVR8). Even so, BI is aggressively pursuing faldaprevir’s indication in genotype 1b. The drug maker announced Thursday that it had already fully enrolled a 950 patient phase III trial.

There could be other hurdles for BI. Although faldaprevir showed strong results without interferon, ribavirin still remains a difficult adjunct to strip away for this new class of treatments. Faldaprevir only hit SVR12 in 39% of patients when used without ribavrin over a 28-week period. The trial also fell unevenly on certain racial groups—not including African Americans, reported MedPage Today. 88% of African Americans suffer from genotype 1 and are known to be more difficult to treat with interferon-based therapies.