The U.S. biosimilars market has generated over $56.2 billion in savings since 2015, according to the DrugPatentWatch Biosimilar Paradox 2026 Market Report. Sounds like progress. It's not, relative to what was possible.
The American Journal of Managed Care estimated biosimilars had the potential to generate $124 billion in savings by 2025. We captured less than half. The gap between what's possible and what's happening isn't a patient behavior problem. It's a formulary design problem. Your PBM is at the center of it.
As of 2025, the FDA has approved 83 biosimilars, with approvals accelerating sharply to 18 per year in 2024 and 2025. Yet for medications with available biosimilars, The Segal Group found that generally less than 10% of prescriptions were filled with a biosimilar. Specialty drugs represent less than 2% of pharmacy volume but account for more than 60% of total pharmacy spending. The biosimilar opportunity is concentrated exactly where your plan spends the most.
Why Do PBMs Keep Branded Biologics on Formulary?
Rebates. Branded biologics like Humira carry large manufacturer rebates. PBMs negotiate those rebates, keep a portion, and pass the rest to plan sponsors. Sometimes.
The math often favors keeping the expensive drug preferred over the cheaper biosimilar that pays no rebate. The Association for Accessible Medicines puts it plainly: adoption of pharmacy-dispensed biosimilars remains disappointing due to PBM formulary practices that favor high-priced brand biologics with high rebates and fees that benefit the PBM but aren't shared with patients.
You're funding the rebate. You're not keeping the savings. That's the same hidden margin structure that inflates costs across your entire pharmacy benefit.
The FTC confirmed this pattern. Their interim staff report found that PBMs and brand drug manufacturers negotiate rebates that are sometimes conditioned on limiting access to lower-cost generic and biosimilar competitors. Nine Humira biosimilars had less than 2% market share in January 2024, despite having parity coverage with the originator and lower net costs per unit.
When a PBM does list a biosimilar, they often place it at parity with the reference product. The branded drug stays allowed without penalty. No incentive means no shift. The savings opportunity sits there, unclaimed.
What's the Private-Label Problem?
PBMs are launching their own private-label biosimilars, then favoring them on formulary. According to MMIT, payers representing 43% of commercial lives said they were not at all likely to place a biosimilar like Wezlana on formulary unless their organization had an affiliation with the private-label distributor. That's not clinical decision-making. That's distribution capture.
By August 2024, CVS converted 97% of Humira use by its commercial customers to biosimilars, with private-label Cordavis versions capturing 15% of overall adalimumab market share. The Center for Biosimilars tracked the combined market share for all 10 adalimumab biosimilars reaching 22% by October 2024. That's progress. But the question is whether the savings flow to your plan or stay inside the PBM's vertically integrated channel.
PBM-owned private-label biosimilars set a price floor for the entire category and concentrate market share when patients use PBM-owned specialty pharmacies. The biosimilar market was supposed to create competition and drive prices down. Vertically integrated PBMs are using it to consolidate control.
What's the Current State of Humira Biosimilars?
Humira was the world's best-selling drug for years. Its biosimilar rollout is the most-watched test case for the entire biosimilar market.
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Ten adalimumab biosimilars are now on the U.S. market. Humira sales have declined more than 56% from their 2023 peak. Seven of the ten now carry interchangeable designations from the FDA. The shift accelerated fast: Evernorth Research Institute tracked adalimumab biosimilar claims growing 1,145% from Q1 2024 to Q1 2025, rising from 4.2% to 52.3% of all adalimumab claims. Average savings: $4,505 per patient per year. For a plan with 100 Humira users, that's $450,000 back in the plan annually.
The Segal Group reported a 2.3 percentage point decrease in branded biologic utilization after CVS excluded Humira from most of its major commercial formularies in April 2024. That's a meaningful shift from a single formulary decision. The levers exist. They're just not being pulled in your favor by default.
What's the Next Wave of Biosimilar Launches?
The Humira wave was just the beginning. The next targets are even bigger for employer plans.
Stelara (ustekinumab): Multiple biosimilars launched in early 2025. Wezlana was the first, with an interchangeability designation. By May 2025, four Stelara biosimilars had interchangeable status: Selarsdi, Otulfi, Starjemza, and Wezlana. Stelara generated $10+ billion annually at peak, making these biosimilars some of the most consequential launches for employer pharmacy spend.
Eylea (aflibercept):Yesafili and Opuviz were approved as the first interchangeable Eylea biosimilars in May 2024. Important for plans covering ophthalmology specialty drugs.
Regulatory tailwind: In June 2024, the FDA issued draft guidance eliminating the requirement for switching studies, allowing interchangeability designations based on analytical and clinical data alone. This accelerates the pipeline. More biosimilars reach interchangeable status faster, giving pharmacists the ability to substitute without prescriber intervention in most states.
Nearly $80 billion in potential savings through 2030 sits in the biologics losing patent protection over the next few years. The peptide and biologic decade is creating both the cost problem and the biosimilar solution simultaneously.
Why Is the U.S. So Far Behind Europe on Biosimilars?
In Europe, biosimilar penetration is dramatically higher. Denmark reached 90% market share for trastuzumab biosimilars within three months of launch. Germany mandates biosimilar starting therapy for new patients. European glargine prices fell 21.6% within 10 years of biosimilar entry. The competitive pressure works because European markets don't have the same PBM rebate structure blocking adoption.
In the U.S., biosimilar insulin (Semglee) captured roughly 15% of basal insulin prescriptions by 2025. Oncology biosimilars have done better, reaching 82% uptake. Civica launched insulin glargine in January 2026 at $45 per box, compared to $150-$500 for branded alternatives. Blue Cross Blue Shield partnered with Civica to distribute it through BCBS plans. That's 70-90% savings on insulin, available now, for any plan willing to add it. The difference: oncology biosimilars are administered in medical settings where physicians control the decision. Pharmacy-dispensed biosimilars run through PBM formularies, where rebate incentives favor the branded product.
The gap between U.S. and European biosimilar adoption is a formulary design problem. The clinical evidence is settled. Biosimilars are equivalent. The FDA says so. The question is whether your PBM's financial incentives are aligned with your plan's interest. In most cases, they aren't.
What Should Employers Demand From Their PBM?
Start by asking your PBM for a biosimilar utilization report broken out by drug class. Less than 10% of your biologic fills going to biosimilars means you have a concrete problem to address.
Don't accept vague answers about "formulary optimization." Push for these specific changes at your next contract renewal:
Mandatory biosimilar-first step therapy. Require biosimilar trial before the reference biologic gets approved. New-to-therapy patients start on the biosimilar. Period.
Member cost-sharing differentials. Create a real financial incentive. A $0 copay on the biosimilar versus standard specialty copay on the reference biologic moves behavior faster than any formulary letter.
Reference biologic exclusion. Where interchangeable biosimilars exist, exclude the reference product entirely. This is what CVS did with Humira. The result was a 2.3-point drop in branded biologic utilization.
Full rebate pass-through. Demand 100% pass-through of any rebates on reference biologics that remain on formulary. The CAA 2026 requires this for contracts renewed after August 2028. Start demanding it now.
Private-label disclosure. Require your PBM to disclose any financial relationship between their organization and private-label biosimilar distributors. Know whether the biosimilar on your formulary is there because it's the best price or because your PBM owns the distribution channel.
Performance guarantees. Tie contract terms to biosimilar adoption rates, not just formulary placement. Placement without adoption is marketing. Adoption is savings.
Your plan sponsor fiduciary duty under ERISA requires you to act in the interest of plan members. Specialty drugs account for more than 60% of pharmacy spend while serving less than 2% of members. Biosimilars offer 15-85% discounts on the most expensive drugs in your formulary. Letting $67.8 billion in potential savings sit on the table because your PBM's formulary isn't structured to capture it isn't a neutral decision. It's a costly one.
The CAA 2026 classified PBMs as "covered service providers" under ERISA 408(b)(2). All PBM compensation must be disclosed and must be "reasonable." A PBM that earns more by keeping a branded biologic on formulary than by switching to a biosimilar has a compensation structure that works against your plan. That's exactly the kind of arrangement the CAA was designed to expose.
The clinical question is settled. The FDA has approved 83 biosimilars. Interchangeability designations are accelerating. The only question left is whether your formulary reflects the science or your PBM's revenue model.
