Biosimilar Selection Guide 2026: Which One Does Your Plan Prefer?

The Biosimilar Landscape in 2026

By 2026, the U.S. biosimilar market has matured into one of the most active corners of specialty pharmacy. Ten or more adalimumab (Humira) biosimilars have launched since the original July 2023 patent cliff, six ustekinumab (Stelara) biosimilars rolled out across 2024-2025 following the late-2024 patent expiration, and the FDA continues to expand the list of products that carry the "interchangeable" designation — the only label that allows a pharmacist to substitute the biosimilar for the reference brand without the prescriber rewriting the order.

The cost stakes are enormous. Reference Humira ran north of $80,000 per patient per year at peak; biosimilar wholesale acquisition cost (WAC) for the same molecule now ranges from a few thousand dollars to roughly half the reference brand, depending on the product and contract. Stelara biosimilars are tracking a similar trajectory. PBMs and payers have responded by reshuffling formularies aggressively, with most major plans now naming a single preferred biosimilar per molecule and excluding (or step-therapy-restricting) the rest.

For prescribers, this means the era of "write the brand, the pharmacy will figure it out" is over. Choosing the wrong biosimilar at the point of prescribing now triggers prior authorization denials, formulary exclusions, or pharmacy-level rejections that delay therapy by days or weeks.

Why Biosimilar Selection Matters for Prior Auth

Plans no longer treat biosimilars as a fungible class. Each major PBM has negotiated rebate contracts with specific manufacturers, and those contracts dictate which biosimilar is preferred on the formulary. Prescribing a non-preferred biosimilar — even when it is clinically identical — typically results in an automatic formulary exclusion or step therapy denial, with the patient required to fail (or document intolerance to) the preferred product first.

Critically, the substitution rules differ from small-molecule generics. With generics, any state-licensed pharmacist may swap the prescribed brand for the AB-rated generic without contacting the prescriber. With biosimilars, automatic substitution is only permitted when the biosimilar carries the FDA "interchangeable" designation AND state law allows it. For non-interchangeable biosimilars (or in states with stricter rules), the prescriber must write the specific biosimilar by name — meaning the burden of selecting the plan-preferred product falls on the clinician, not the pharmacy.

The result: knowing which biosimilar each major plan prefers, before signing the prescription, is the single highest-leverage step a prescriber can take to avoid a 7-14 day therapy delay.

Adalimumab (Humira) Biosimilar Landscape

Ten adalimumab biosimilars are commercially available in 2026, and they are not clinically interchangeable with each other on a generic-substitution basis. Key product-level differences include FDA interchangeability status, citrate-free vs citrate-buffered formulation (citrate stings on injection), and high-concentration (100 mg/mL) vs low-concentration (50 mg/mL) presentations. The current adalimumab biosimilar lineup:

• ✓ Amjevita (adalimumab-atto, Amgen) — first U.S. adalimumab biosimilar to launch (January 2023); not interchangeable; available in low and high concentration
• ✓ Cyltezo (adalimumab-adbm, Boehringer Ingelheim) — first FDA-designated interchangeable adalimumab biosimilar; citrate-containing low-concentration
• ✓ Hadlima (adalimumab-bwwd, Organon/Samsung Bioepis) — high-concentration citrate-free formulation available; interchangeable status added
• ✓ Hyrimoz (adalimumab-adaz, Sandoz) — citrate-free high-concentration; widely contracted on PBM formularies
• ✓ Abrilada (adalimumab-afzb, Pfizer) — interchangeable designation; available in high-concentration citrate-free
• ✓ Hulio (adalimumab-fkjp, Biocon/Viatris) — citrate-containing biosimilar
• ✓ Yuflyma (adalimumab-aaty, Celltrion) — interchangeable; citrate-free high-concentration
• ✓ Yusimry (adalimumab-aqvh, Coherus BioSciences) — known for deeply discounted cash-pay pricing through Mark Cuban Cost Plus and similar channels
• ✓ Idacio (adalimumab-aacf, Fresenius Kabi) — citrate-free low-concentration
• ✓ Simlandi (adalimumab-ryvk, Alvotech/Teva) — interchangeable high-concentration citrate-free; launched 2024
• ✓ The "interchangeable" designation allows a pharmacist to substitute the biosimilar for reference Humira (subject to state law) without prescriber re-authorization. It does NOT allow substitution between two different biosimilars.

Adalimumab Biosimilar Formulary Preferences by Major PBM

The three largest PBMs — CVS Caremark, Express Scripts, and OptumRx — collectively manage pharmacy benefits for the majority of commercially insured Americans. Each has negotiated different preferred-biosimilar arrangements. The list below reflects publicly disclosed 2025-2026 formulary positioning; always verify against the live formulary because PBMs revise these contracts mid-year.

• ✓ CVS Caremark — Hyrimoz (Sandoz) and Cyltezo (Boehringer Ingelheim) generally preferred; reference Humira removed from many CVS Caremark commercial template formularies starting 2024
• ✓ Express Scripts — Simlandi and Hadlima have been positioned as preferred on multiple Express Scripts national formularies; Express Scripts also launched its own private-label biosimilar arrangement through Quallent Pharmaceuticals
• ✓ OptumRx — Hadlima (Organon) and Cyltezo (Boehringer Ingelheim) commonly preferred; OptumRx also offers low-WAC private-label adalimumab through Nuvaila
• ✓ Prime Therapeutics — Hyrimoz frequently preferred on BCBS-affiliated Prime formularies
• ✓ Reference Humira (AbbVie) — most major commercial plans now require trial of a preferred biosimilar before approving brand Humira; Medicare Part D plans vary, with some retaining brand on formulary alongside biosimilars
• ✓ Self-funded employer plans on any of the above PBMs may carve out a different preferred product per their plan sponsor contract — always check the member-specific formulary, not just the PBM template.

Infliximab (Remicade) Biosimilars

The infliximab biosimilar market has been more stable than adalimumab's because IV infliximab biosimilars launched earlier (Inflectra in 2016, Renflexis in 2017) and most plans long ago shifted to a preferred biosimilar. Available products include Inflectra (infliximab-dyyb, Pfizer/Celltrion), Renflexis (infliximab-abda, Organon/Samsung Bioepis), Avsola (infliximab-axxq, Amgen), and Ixifi (infliximab-qbtx, Pfizer — limited U.S. availability). For IV infliximab, most commercial plans and Medicare Advantage plans prefer Inflectra or Avsola, with reference Remicade typically requiring step therapy.

The newer story is Zymfentra (infliximab-dyyb, Celltrion) — the first and only subcutaneous infliximab, launched in 2023 as a 505(b)(2) product (not a biosimilar to Remicade despite using the same -dyyb suffix). Zymfentra coverage is fragmented: many plans treat it as a novel agent and require failure of self-administered TNF biosimilars (adalimumab products) before approving SC infliximab. Prescribers should expect a multi-step prior auth pathway and document why an SC infliximab is medically necessary versus simply restarting an adalimumab biosimilar.

Ustekinumab (Stelara) Biosimilars

Stelara's major U.S. patent expired in late 2024, and six ustekinumab biosimilars launched within roughly a year of that expiration — making this the single largest cohort of biosimilars to enter the market simultaneously in U.S. history. The 2024-2025 ustekinumab biosimilar wave includes:

• ✓ Wezlana (ustekinumab-auub, Amgen) — first FDA-approved ustekinumab biosimilar AND the only one with the FDA "interchangeable" designation as of mid-2026
• ✓ Selarsdi (ustekinumab-aekn, Alvotech/Teva)
• ✓ Otulfi (ustekinumab-aauz, Fresenius Kabi/Formycon)
• ✓ Pyzchiva (ustekinumab-ttwe, Sandoz/Samsung Bioepis)
• ✓ Imuldosa (ustekinumab-srlf, Accord BioPharma/Dong-A ST)
• ✓ Yesintek (ustekinumab-kfce, Biocon Biologics)
• ✓ Because all six launched within months of one another, PBM formulary positions are still in flux as of early 2026. Many plans named a preferred ustekinumab biosimilar in mid-2025 contracts, but rebid windows are short and preferred products are likely to shift over the next 12-18 months. Wezlana is the only product on which a pharmacist may substitute for reference Stelara without prescriber reauthorization.

Other Key Biosimilars to Know

Beyond the TNF/IL-23 inhibitor space, several other biosimilar categories are now meaningful drivers of formulary policy:

• ✓ Tocilizumab (Actemra) — Tofidence (tocilizumab-bavi, Biogen) and Tyenne (tocilizumab-aazg, Fresenius Kabi) are the U.S. tocilizumab biosimilars; both available in IV and SC presentations
• ✓ Denosumab (Prolia/Xgeva) — Wyost/Jubbonti (denosumab-bbdz, Sandoz) and Ospomyv/Xbryk (denosumab-dssb, Samsung Bioepis) launched 2024-2025; the dual-brand naming reflects the separate Prolia (osteoporosis) and Xgeva (oncology) reference indications
• ✓ Etanercept (Enbrel) — Erelzi (etanercept-szzs, Sandoz), Eticovo (etanercept-ykro, Samsung Bioepis), and Nepexto (etanercept-jess) are FDA-approved, though Enbrel patent litigation has delayed full U.S. market entry compared to other anti-TNFs
• ✓ Pegfilgrastim (Neulasta) — multiple biosimilars including Fulphila, Udenyca, Ziextenzo, Nyvepria, Stimufend, and Fylnetra; pegfilgrastim is one of the most commoditized biosimilar markets, with deep payer-driven price competition

How to Identify Your Patient's Preferred Biosimilar Before Prescribing

The 30 seconds spent confirming the plan-preferred biosimilar before signing the script saves hours of downstream prior auth and pharmacy callbacks. Practical workflow options:

• ✓ Pull the published plan formulary — most commercial plans publish a current-year formulary PDF or searchable web tool that lists preferred and non-preferred biosimilars by tier
• ✓ Run a Surescripts real-time benefit check (RTBC) at the point of prescribing — modern EHRs return the patient-specific covered alternatives, copays, and PA requirements within the e-prescribing screen
• ✓ Call the PBM prescriber line printed on the patient's pharmacy card — fastest authoritative answer for unusual self-funded plans whose formulary differs from the PBM template
• ✓ Use a clinical decision tool (RxCheckUp or similar) that maintains the cross-PBM biosimilar preference table and surfaces it inside the prior auth workflow
• ✓ Confirm the formulation detail (citrate-free vs citrate, high vs low concentration, autoinjector vs prefilled syringe) — a "preferred" biosimilar may only be preferred in certain formulations

What to Do When the Prescribed Biosimilar Is Rejected

When a biosimilar prescription comes back with a denial or pharmacy rejection, prescribers have two paths and should choose based on whether the patient is treatment-naive or already stable on therapy.

For treatment-naive patients (or patients not yet stabilized), the fastest path is almost always to switch to the plan-preferred biosimilar. The molecule is the same, the clinical efficacy data are equivalent, and the patient avoids a 7-14 day appeal cycle. Re-route the prescription to the preferred product and document the change.

For patients already stable on a specific biosimilar — for example, someone who has been on Cyltezo for 18 months in remission — switching is clinically risky and the right move is to file a formulary exception with clinical justification. The exception letter should document the duration of stability, the disease activity at baseline vs current, the immunogenicity risk of switching, and any payer-specific continuity-of-care language. Most plans approve continuity-of-care exceptions when the documentation is complete.

Common Pitfalls and How to Avoid Them

A handful of avoidable mistakes account for most biosimilar-related prescribing failures:

• ✓ Treating "adalimumab" as one drug — there are 10+ distinct products, each with its own NDC, formulary status, and patient assistance program; specifying the brand on the prescription is mandatory
• ✓ Ignoring citrate vs citrate-free — citrate-buffered injections cause meaningful injection-site pain in some patients; if the patient previously stopped Humira due to injection pain, prescribe a citrate-free biosimilar
• ✓ Confusing concentrations — high-concentration (100 mg/mL) and low-concentration (50 mg/mL) presentations have different injection volumes and device options; pediatric and weight-based dosing may require a specific concentration
• ✓ Assuming any biosimilar is interchangeable — only specific products carry the FDA interchangeable designation; in the absence of that designation (and in states without permissive substitution laws), the pharmacy cannot substitute and will reject the prescription if the prescribed brand is non-preferred
• ✓ Forgetting that PBM formularies revise mid-year — a biosimilar that was preferred in January may be displaced in July; re-verify on each new patient or after any plan-year change
• ✓ Skipping the patient-assistance check — even when a biosimilar is non-preferred, manufacturer copay programs (when permitted by the plan) can make a non-preferred product affordable for a stable patient

How RxCheckUp Speeds Biosimilar Selection

RxCheckUp's drug database now includes all 10+ adalimumab biosimilars, all 6 ustekinumab biosimilars, the full infliximab and tocilizumab biosimilar lines, and the major denosumab, etanercept, and pegfilgrastim products — each tagged with FDA interchangeability status, formulation details, and current PBM formulary positioning. When a prescriber starts a prior auth for any reference biologic, RxCheckUp surfaces the patient's plan-preferred biosimilar inline, pre-fills the correct prior auth form, and routes the request to the right pharmacy benefit channel — reducing the average time from prescription to therapy start by days.