The latest proposal from the U.S. Centers for Medicare and Medicaid Services (CMS) to let insurers use step therapies, or to drop protections on certain classes of drugs if price increases outpace inflation, may harm a wider circle of drugmakers, ranging from GlaxoSmithKline to Gilead.

Amgen, Regeneron Pharmaceuticals and Roche Holding are often cited as the drugmakers having the most to lose in proposed changes to Medicare. Regeneron’s Eylea, Roche’s Avastin and Amgen’s franchise of blood boosters get...