Data from a highly anticipated mid-stage study of an all-oral hepatitis C therapy under development by Gilead Sciences and Bristol-Myers Squibb were released this week at the European Association for the Study of Liver Disease, or EASL. And the results couldn’t have been much better.

The new hepatitis C therapy combines Bristol’s daclatasvir with Gilead’s GS-7977. Each is a pill administered once a day.

Bristol reported that the combination of the two therapies, taken by patients for 24 weeks, achieved “a rapid and sustained viral response.” Four weeks after completing the treatment, all genotype 1 patients and 91 percent of genotype 2 and genotype 3 patients had no detectable hepatitis C virus RNA in their blood.

Gilead also announced that in a separate study, which enrolled 25 genotype 1 patients, GS-7977 plus ribavirin suppressed the hepatitis C virus in 88 percent of trial patients. The results surpassed most expectations.

After Vertex and Merck gained U.S. Food and Drug Administration approval for their hepatitis C drugs early in 2011, there has been a dramatic race for those in the hepatitis C space to formulate the first all-oral therapy that could control the virus without the need for interferon injections which often cause unpleasant side-effects.

But despite the impressive results from their combination therapy, Gilead doesn’t appear keen on jumping immediately into late-stage trials. To justify the $11 billion it paid for Pharmasset and gain rights to its then lead compound P-7977, Gilead needs to deliver returns to its shareholders. And pursuing a collaborative effort with Bristol may very well dilute Gilead’s potential profits.

In an interview with The Street, Bristol spokeswoman Cristi Barnett said, “Given the strong SVR4 data from the combo trial of daclatasvir and GS-7977, and in the interest of advancing the science and for the benefit of patients, we were interested in a phase 3 collaboration. Unfortunately Gilead was not interested.”

A Gilead spokesman disputes that, saying that the company needs time to evaluate and understand the new data “We’re going to do that, and look at the best option or options for proceeding as quickly as possible to advance the best all-oral regimen,” he says.

If the companies are unwilling to collaborate, they both still have compounds in their respective pipelines that could replace the other. Gilead could combine GS-7977 with GS-5885, which belongs to the same inhibitor class as Bristol’s daclatasvir. Bristol, on the other hand, could combine daclastasvir with INX-189, which it acquired from Inhibitex and which belongs to the same nucleoside class of drugs as GS-7977.

Neither scenario provides the fastest path to market however, as both GS-5885 and INX-189 have a long development pathway before they can reach a late-stage combination study. It may mean that hepatitis C patients might have to wait a little longer for what appears to be a highly potent therapy.