PBM-affiliated private label biosimilars would seem to have a built-in formulary advantage. But for ustekinumab, that advantage has not carried over to Medicare Part D.
A recent JAMA Network Open study identified 12 ustekinumab products available for formulary coverage in early 2026. Yet the average Part D plan covered only 2.3 biosimilars. Even more surprising, PBM affiliated private label products were largely missing from formularies connected to their corporate siblings.
CVS Health’s Cordavis labeled Pyzchiva received no Part D coverage. Optum Rx’s Nuvaila labeled Wezlana appeared in just 0.4% of UnitedHealth plans.
The results run against the conventional logic of vertical integration. If a PBM can influence formulary placement, why not direct volume toward its own product like in commercial formularies? The answer lies in the Inflation Reduction Act’s (IRA) Part D redesign, which made the economics of an affiliated private label biosimilar potentially less attractive in Medicare than in the commercial market.
Below, we follow the incentives that help explain why PBM-affiliated biosimilars remain largely absent from Medicare Part D formularies.