The Biosimilar Void: Why 86 FDA-Approved Biosimilars Still Do Not Reach Patients
Intelligence briefing on the US biosimilar market access problem in 2026: PBM formulary barriers, rebate trap mechanics, USD 232 billion missed savings risk, and what health systems and PE investors can do now.
The FDA has now approved 86 biosimilars. The current wave is broader and more competitive than any that preceded it, reaching into oncology checkpoint inhibitors, long-acting insulins, and ophthalmology biologics that were once considered out of reach for biosimilar development. The agency has streamlined its clinical evidence requirements: the EMA adopted a reflection paper in March 2026 outlining a tailored clinical approach that reduces Phase 3 data requirements for certain products, mirroring FDA alignment that allowed Formycon to bypass the Phase 3 trial entirely for its pembrolizumab biosimilar based on pharmacokinetic equivalence alone.
The regulatory pathway is not the problem. The market access pathway is. Cardinal Health's 2026 Biosimilars Report — the most comprehensive annual analysis of the US biosimilar market — found that as of early 2026, biosimilars accounted for approximately 23% of the total biologics market in the United States. The report warned that a structural "biosimilar void" could result in USD 232 Billion in missed savings over the next 10 years if current conditions persist. The void is not a regulatory problem or a clinical problem. It is a commercial architecture problem.
The Humira case study: Adalimumab (Humira) lost US exclusivity in January 2023. Multiple biosimilars launched. The branded product retained more than 95% market share throughout 2023 because PBMs had negotiated rebate structures with AbbVie that made formulary placement of the high-cost original more financially attractive to the PBM than switching to the biosimilar. Market share only shifted materially when CVS Caremark removed branded Humira from its major national formularies in April 2024 — at which point utilisation surged from near-zero to 97% on those plans. But the primary beneficiary was Cordavis Hyrimoz, a co-branded biosimilar legally affiliated with CVS Health itself. Market access is now a function of PBM affiliation as much as clinical evidence or price.
The mechanics of the rebate barrier are now well-documented in Congressional testimony, in the DrugPatentWatch biosimilar paradox analysis published in January 2026, and in the Centre for Biosimilars literature. Reference biologic manufacturers respond to biosimilar entry by offering substantial rebates to PBMs in exchange for preferred formulary placement. The rebate flow benefits the PBM contractually even when the net cost to the health plan of keeping the branded product on formulary exceeds the biosimilar's list price. The PBM's contractual obligation to meet aggregate rebate guarantees means that a lower-cost biosimilar that does not provide equivalent rebate volume can be excluded from formulary, not because it is clinically inferior or economically more expensive to the payer in net terms, but because it disrupts the rebate accounting structure.
The 2026 formulary exclusion lists from the three largest PBMs — CVS Caremark, Express Scripts (Cigna), and Optum Rx (United Health Group) — show continued use of exclusions to shape competition, particularly in crowded biologic markets such as Humira and Stelara. Drug Channels analysis of the 2026 lists notes that formulary preferences for Humira and Stelara are dominated by private-label biosimilars affiliated with the same parent companies that operate the three PBMs. This vertical integration of biosimilar manufacturing and formulary management represents a structural evolution in the rebate trap: the PBM no longer necessarily protects the originator brand, but it does protect its affiliated biosimilar brand against independent competitors.
The 2026 biosimilar landscape is not uniformly bleak. Cardinal Health's report identifies meaningful structural shifts that are creating new access pathways alongside the persistent rebate barriers. The Centre for Biosimilars notes in its January 2026 analysis that some PBMs are introducing "rebate credit" mechanisms, allowing the price difference between a reference product and a biosimilar to count as a "phantom credit" toward rebate guarantee obligations — effectively removing the financial disincentive to formulary preference for the lower-cost biosimilar. This is a meaningful if imperfect fix that reduces the exclusion problem without requiring legislative action.
Congressional attention to the biosimilar access problem has intensified. Witnesses in 2025 and 2026 hearings have highlighted distortive rebate practices and outdated Medicare rules as creating perverse incentives for prescribers to select higher-cost reference products over biosimilar alternatives. The policy response has not yet produced legislation, but the scrutiny has accelerated PBM adoption of fiduciary and transparent contracting models in self-insured employer markets, where the plan sponsor has a direct financial incentive to prefer biosimilars when net cost is lower.
The biosimilar void quantified: If the market and policy conditions that created the USD 232 Billion missed savings estimate persist, the US healthcare system will spend the equivalent of two years of total biosimilar savings generated since 2015 above the level that competitive biosimilar markets in Europe demonstrate is achievable. Health system procurement teams, self-insured employers, and PE-backed provider groups that take an active position on biosimilar formulary management now will realise savings that passive adopters will not.
The oncology biosimilar category is the most commercially mature pathway. Cardinal Health's finding that oncology biosimilars reach an average 81% market share within five years of launch reflects the hospital formulary committee dynamic: when a health system's oncology pharmacy director and formulary committee decide to adopt a biosimilar, the substitution rate is high because the same institution controls both prescribing and dispensing in the infusion centre. That is structurally different from the retail pharmacy dynamic where the PBM intermediary controls formulary placement independently of the prescribing physician.