The PTO’s Patent Trial and Appeal Board said it will review patents covering the blockbuster erectile dysfunction drug Cialis and a widely used pneumonia vaccine, Prevnar 13, granting petitions from Mylan and Merck Sharp & Dohme Corp.

Mylan is challenging Eli Lilly & Co.’s patent on Cialis (tadalafil) dosing forms, saying its claims on a daily maximum of about 20 mg were obvious, considering the SNDA of the pill’s spiritual predecessor, Viagra (sildenafil) — as well as a broad ICH drug development guidance on using dose-response information to identify appropriate starting and maximum amounts, adopted by the FDA in 1994.

Cialis brought in more than $2.4 billion last year in global sales. Eli Lilly’s dosing patent is set to expire in April 2020; other patents on the compound and use, in both the U.S. and Europe, expire in November of this year. — Conor Hale