A Pfizer Inc. antibacterial vaccine patent sustained another loss at the U.S. Patent and Trademark Office, this time in a challenge brought by Sanofi Pasteur Inc. and South Korean company SK Chemicals Co. LTD.

The PTO’s Patent Trial and Appeal Board June 3 found all 45 claims of U.S. Patent No. 9,492,559 unpatentable as obvious in light of prior art. The decision came in an inter partes review, a procedure in which the patentability of a patent’s claims are considered...