Patients alleging makers of four diabetes drugs should have warned about pancreatic cancer risk won reinstatement of their suits against Eli Lilly & Co., Merck Sharp & Dohme Corp., and others.

The trial court erred in ruling about 750 suits were barred under Wyeth v. Levine, the U.S. Court of Appeals for the Ninth Circuit said in an unpublished opinion Dec. 6.

The drugs at issue are Janumet and Januvia, manufactured by Merck; Victoza, made by Novo Nordisk Inc.;...