Valeant Pharmaceuticals International Inc. became a household name with its historic rise and fall. Reviving the drugmaker is proving a unique challenge.

“This is a turnaround opportunity of a lifetime,” Chief Executive Officer Joseph Papa, who took over in May 2016, said during a presentation Wednesday at the J.P. Morgan Healthcare Conference in San Francisco.

Papa has cut the total debt burden by more than $6 billion from a peak of $32 billion just before he joined, through asset sales and refinancing, while trying to increase revenue. He still has a long way to go. Dermatology is one area lagging behind the rest, Papa said.