Why Biosimilar Companies Are Leaving Money on the Table in Market Access

The biosimilar market has generated over USD56.2 billion in savings for America's patients and the U.S. healthcare system since 2015. The FDA approved a record 18 biosimilars in 2025 — across oncology, immunology, ophthalmology, and endocrinology. And in the fastest-growing categories biosimilars have already captured 81% market share within five years of launch. 

The opportunity has never been larger. The execution has never been more complex.

And yet many biosimilar companies — including well-funded, scientifically sophisticated ones — are systematically underperforming on market access. Not because their products are inferior. Because their market access strategy was built too late, designed too narrowly, and executed without understanding how payer dynamics have fundamentally changed.

Here is what is going wrong, and how to fix it.

The Core Mistake: Treating Market Access as a Launch Activity

The most common and most costly market access mistake in biosimilars is treating payer strategy as something you build in the twelve months before launch.

By the time you are filing your BLA, your market access architecture should already be in place. Payer relationships take years to develop. Formulary positioning requires evidence packages that take time to build. Reimbursement modeling — particularly in the Medicare Part D context — requires understanding pricing dynamics that shift every budget cycle.

If your market access team is being hired as you approach your PDUFA date, you are already behind.

Underestimating PBM Consolidation

The three largest PBMs — CVS Caremark, Express Scripts, and OptumRx — control formulary access for the majority of commercially insured lives in the United States. Their consolidation has created an environment where formulary exclusions are not the exception — they are the strategy. Express Scripts alone added 129 new formulary exclusions in 2026.

Step therapy requirements, site-of-care steering, and formulary exclusions are actively being used to manage biosimilar uptake in ways that are not always intuitive. A biosimilar that wins on price may still lose on access if the PBM has a rebate relationship with the reference biologic manufacturer that makes formulary exclusion economically rational for them.

But there is a newer and increasingly important dynamic: PBMs are now actively preferring their own affiliated private-label biosimilars over third-party biosimilars on their formularies. CVS Caremark's Cordavis, for example, is a direct commercial entity competing with independent biosimilar manufacturers for formulary position within the same PBM's book of business. This is not a theoretical risk — it is already reshaping formulary decisions in adalimumab and other high-volume categories.

Understanding PBM economics — not just as a theoretical framework, but at the contract and affiliate level — is a prerequisite for building a market access strategy that actually works.

Ignoring the ASP Variability Problem

Average Sales Price (ASP) variability is one of the most underappreciated risks in biosimilar commercialization, particularly for hospital and clinic-administered products reimbursed under Medicare Part B.

ASP is calculated on a lagging basis and is sensitive to pricing decisions made across the competitive set. As new biosimilars enter a reference biologic's market and price aggressively, ASP can decline faster than your cost structure can accommodate. The HHS ASPE confirmed that biosimilar competition reduced Medicare Part B spending by 62% in 2023 — validating the scale of ASP compression in competitive biosimilar classes. 

Adding further complexity: the 2026 Medicare Physician Fee Schedule final rule introduced significant new ASP reporting methodology changes effective 01/01/2026, altering how ASP is calculated and reported across the competitive set. Companies that have not updated their reimbursement models to reflect these methodology changes are working from incorrect assumptions.

Model multiple ASP scenarios — including a scenario where a late entrant prices 40–50% below you — and build your cost of goods and gross margin targets around those scenarios, not the optimistic case.

Underinvesting in the Evidence Package

Payers in 2026 are not buying on price alone. They are asking for real-world evidence, comparative effectiveness data, and pharmacovigilance records that demonstrate the biosimilar performs as expected in the real world — not just in clinical trials.

The Consolidated Appropriations Act of 2026, signed on 03/02/2026, introduces the most significant PBM reforms in a decade — prohibiting rebate-linked compensation in Medicare Part D and requiring enhanced transparency and standardized reporting on formulary placement rationale. 

It is important to note that these reforms take effect in 2028–2029, not immediately. But the strategic signal is clear: the financial incentives that allowed PBMs to exclude biosimilars in favor of rebate-paying reference biologics are being structurally dismantled. Biosimilar manufacturers who are building their evidence packages, payer relationships, and formulary access strategies now will be best positioned when those reforms fully take effect.

Your evidence generation strategy should be running in parallel with your clinical program — not starting after approval.

Building a Reimbursement Strategy in a Vacuum

Reimbursement strategy for biosimilars is not a standalone workstream. It intersects with your pricing strategy, your patient services model, your specialty pharmacy relationships, and your medical affairs function. Companies that build these workstreams in silos consistently underperform on access metrics in the first twelve to eighteen months post-launch.

The fix is organizational: appoint a single executive accountable for the full market access ecosystem — pricing, contracting, formulary, reimbursement, and patient services — and give that person a seat at the leadership table from day one of commercial planning.

What Good Looks Like

The biosimilar companies executing market access well in 2026 share four characteristics:

• They started payer engagement years before launch — not at BLA submission

• They built scenario-based economic models that stress-tested ASP compression, rebate dynamics, and the new private-label PBM competitive threat

• They invested in real-world evidence programs alongside clinical development, not after approval

• They treated market access as a CEO-level priority — not a commercial function hand-off

The market is there. The science is proven. The gap between winning and losing in biosimilars in 2026 is almost entirely an execution and strategy gap.

At Katogen, we bring deep operator experience in product strategy, market access design, and commercial execution — grounded in 35+ years of hands-on biopharma leadership, including building a complex generics businesses from the ground up.