TORONTO Drug makers Valeant Pharmaceuticals International and Kadmon Pharmaceuticals will collaborate to develop antiviral drugs for treating such diseases as hepatitis C, the two companies said Monday.

Kadmon, founded by former ImClone Systems chief executive Samuel Waksal, will pay Valeant $5 million upfront, plus milestones and royalties, for the right to develop taribavirin. Under a separate agreement, Valeant paid Kadmon $7.5 million to market ribavirin, also a hepatitis C drug, in several European countries.

“We are pleased to find a strong partner for a compound that we believe has potential to help patients in need of improved treatment,” Valeant CEO J. Michael Pearson stated. “While participating in product development in the overall hepatitis C market no longer fits within our corporate development strategy, ribavirin should be a significant product for our branded generics portfolio in central Europe.”