Biosimilar Switching in 2026: Documentation Requirements Payers Expect

The biosimilar landscape in 2026 looks nothing like it did three years ago. Adalimumab biosimilars alone went from zero US market options in 2022 to more than a dozen competing products. Infliximab biosimilars have been on market long enough that most payers now consider them the default. Etanercept biosimilars are gaining formulary traction. And payers have responded to this shift by systematically removing originators from their preferred tiers — or dropping them from coverage entirely.

For practices managing biologic patients, this creates two distinct problems. The first is administrative: understanding what documentation payers now require for biosimilar compliance. The second is clinical: knowing when you have grounds to push back on a forced switch — and what that documentation needs to look like.

The Adalimumab Situation

Humira's loss of exclusivity in January 2023 triggered the largest biosimilar entry in US history. By 2026, multiple adalimumab biosimilars have established significant formulary presence — Hadlima, Hyrimoz, Cyltezo, Yusimry, and others have all found preferred positions on major commercial plans.

Most major commercial payers have now moved originator Humira to a non-preferred or non-covered tier for new starts. For existing patients on originator adalimumab, the policies vary: some plans allow grandfathering through renewal periods, others require active steps to transition patients to a biosimilar by a defined date.

The practical effect is that many rheumatology, gastroenterology, and dermatology practices are managing waves of patients receiving letters about mandatory biosimilar transitions — often without clear guidance on what documentation they need to provide, or what their rights are if the switch creates clinical problems.

Non-Medical Switching: What It Means and Why It Matters

Non-medical switching refers to payer-mandated transitions from one biologic to another for formulary or cost reasons rather than clinical ones. A patient who has been stable on Humira for four years getting moved to a biosimilar because their plan changed its formulary is non-medical switching.

The clinical concern is real. While biosimilars are FDA-approved as highly similar to the originator, not all patients transition without issue. Immunogenicity is a documented risk — some patients develop antibodies to biosimilars after switching that they didn't develop on the originator. For patients with established immunological tolerance to an originator product, switching carries a non-trivial clinical risk that treating physicians are right to consider.

This isn't an anti-biosimilar argument — it's a precision medicine argument. Some switches are clinically straightforward. Others aren't. The documentation distinction matters for both scenarios.

When Payers Require Documentation for Staying on the Originator

If your patient needs to remain on the originator biologic despite payer pressure to switch, you're essentially filing a medical exception. The documentation bar is higher than a standard PA renewal, and it varies by payer.

Most commercial payers require the following for a medical exception to a biosimilar switch:

Clinical stability statement: Documentation that the patient is currently stable and responding to the originator product, with quantified disease activity scores (DAS28 for RA, CDAI for Crohn's, PASI/BSA for psoriasis)
Prior switch history: If the patient has previously attempted a biosimilar switch and experienced loss of disease control or immunogenicity, that history needs to be documented with objective data — not just a note that the switch "didn't work"
Clinical rationale for originator-specific continuation: This is the hardest part. You need to articulate why this specific patient requires the originator rather than a biosimilar — prior hypersensitivity, documented antibody formation, formulation-specific tolerability issues (citrate-free vs citrate-containing formulations, for instance)
Prescriber attestation: Many payers require the treating physician to attest that the switch would represent a risk to the patient, not just a preference

The FDA's biosimilar guidance is useful background for understanding what "interchangeable" designation means in practice — an important technical point when constructing a medical exception argument.

Infliximab: A More Established Landscape

Infliximab biosimilars have been on market in the US since 2016. Inflectra and Renflexis have been followed by Ixifi, Avsola, and others. By 2026, most major payers treat infliximab biosimilars as the standard of care for new starts in RA, IBD, psoriasis, and ankylosing spondylitis.

For new infliximab PA requests, expect payers to default to requiring a biosimilar. If you're requesting originator Remicade for a biologic-naive patient, you'll need a documented exception reason upfront — not after the denial comes back.

For existing Remicade patients, the switching pressure has been intense since 2022. If your patient has been stable on Remicade for years and faces a forced transition, document their current clinical status thoroughly before any switch attempt. If they later experience worsening after switching, having a documented pre-switch baseline with objective disease activity scores makes the medical case for returning to the originator substantially stronger.

State Protections: Where Patients Have More Rights

Non-medical switching protections exist at the state level in a growing number of jurisdictions. These laws vary considerably, but the strongest versions prevent health plans from requiring patients to switch from a stable biologic to a different product (including a biosimilar) without physician consent and a clinical review process.

As of 2026, states with meaningful non-medical switching protections for biologics include states that have adopted the NCSL model step therapy legislation or specific biosimilar switching laws. Practices operating in these states have an additional compliance tool: referencing the relevant state statute in a denial appeal can be effective when a payer is applying a formulary-driven switch without appropriate clinical review.

This protection doesn't eliminate the documentation requirement — it changes the legal posture. Know your state's rules before assuming you're operating in a pure payer-discretion environment.

Documentation for Compliant Biosimilar Switches

When a switch is clinically appropriate and the patient consents, the documentation for a biosimilar PA is generally simpler than an originator exception. But "simpler" doesn't mean empty.

For a biosimilar PA renewal or new authorization, payers typically expect:

Confirmed indication and ICD-10 codes matching the payer's biosimilar coverage criteria
Current disease activity documentation (condition-appropriate validated scores)
Prior treatment history demonstrating step therapy compliance (same requirements as for originator biologics)
Confirmation that the biosimilar being requested matches the FDA-approved indications — some biosimilars don't carry all originator indications via extrapolation, which can create coverage issues for off-label use cases

That last point trips up practices more often than it should. Not every adalimumab biosimilar has been approved for every Humira indication. Before submitting a biosimilar PA for a non-RA or non-psoriasis indication, verify the specific biosimilar's FDA label.

The Extrapolation Issue

FDA biosimilar approval can include extrapolation of indications from the reference product — meaning a biosimilar tested in RA patients can receive approval for Crohn's disease based on biosimilarity to the reference biologic, without separate Crohn's clinical trials. Most adalimumab and infliximab biosimilars have received full indication extrapolation.

But payers don't always update their coverage policies in sync with FDA approvals. A biosimilar may be FDA-approved for IBD via extrapolation while the payer's policy was written before that extrapolation was granted — and hasn't been updated. When you submit, you may run into a payer denial citing "no coverage policy for [biosimilar] in Crohn's disease" even when the FDA approval is clear.

This is a situation where citing the FDA approval letter directly in your submission, and noting the extrapolation explicitly, can resolve what would otherwise become a denial-and-appeal cycle.

How Luma Handles Biosimilar Documentation

Biosimilar switching requests are among the most documentation-intensive PA scenarios a practice can face, because the requirements span formulary rules, medical exception criteria, state law, and FDA approval status simultaneously. A generic PA template won't cut it.

Luma generates documentation specifically addressing biosimilar switch criteria — whether you're documenting compliance with a payer-directed switch or building the medical exception case for staying on an originator. The platform researches current payer policy for the specific biosimilar-originator pair and generates submission language that maps directly to the reviewer's checklist. You can see how this fits into a broader approach to PA documentation on the Luma blog.

The biosimilar adoption data consistently shows that documentation gaps — not clinical resistance — are a primary driver of delayed or denied PA requests for both biosimilars and originator biologics in switch scenarios. Getting the documentation right is the lever practices can actually pull.

Sources:
1. FDA Biosimilar Product Information — fda.gov
2. NCSL Step Therapy and Non-Medical Switching State Laws — ncsl.org
3. AJMC — Biosimilar Adoption Barriers and Payer Policies — ajmc.com
4. Alliance for Safe Biologic Medicines — Non-Medical Switching Resources — safebiologics.org
5. ACR — Position Statement on Biosimilar Non-Medical Switching — rheumatology.org