Merck & Co and Bristol-Myers Squibb have signed an agreement to test a once-daily oral combination of a pair of investigational hepatitis C drugs from their respective pipelines.

The drugs in question are B-MS' NS5A replication complex inhibitor daclatasvir and Merck's NS3/4A protease inhibitor MK-5172. A Phase II trial, conducted by the latter, will look at the combo as a treatment for people with genotype 1 chronic HCV infection, the most common form of hepatitis.

The companies note that a Phase I safety evaluation has been completed but no agreement is in place regarding clinical development activities beyond Phase II. Just last week, B-MS announced it has signed a deal with Vertex Pharmaceuticals which will see the latter conduct two studies of a combination of VX-135, a nucleotide analogue HCV polymerase inhibitor and daclatasvir.

Merck is also conducting Phase II trials of MK-5172 in combination with other approved and investigational medications, including an all-oral combo with MK-8742, the US drug giant’s own investigational HCV NS5A protease inhibitor. Merck already markets Victrelis (boceprevir) for HCV which had fourth-quarter sales of $115 million, up 32% on the like, year-earlier period.

Victrelis, approved in 2011, is an oral treatment and is taken along with another oral treatment, ribavirin, but also with a pegylated interferon, which has to be injected. The latter can come with serious side effects and a number of companies are engaged in the race to come up with all-oral treatments.

Eliav Barr, head of infectious diseases at Merck Research Laboratories, said that "in HCV, agreements like this that combine novel investigational candidates are important to evaluate the potential of novel oral regimens early in the development cycle”.