Interchangeable biosimilars are getting approved faster, and Wezlana shows why

The U.S. Food and Drug Administration’s decision to clear Amgen’s Wezlana (ustekinumab-auub) as both a biosimilar and an interchangeable option to Stelara (ustekinumab) may read like a clinical milestone, but for operators it becomes a workflow and contracting issue. Interchangeability means pharmacists can substitute at the pharmacy counter without first contacting the prescriber, depending on state law, as Healthcare Purchasing News reported from the FDA announcement.

The bigger takeaway is review timing. A brief report in Therapeutic Innovation & Regulatory Science, published by Springer, analyzed FDA data on interchangeable biosimilars and reported that average approval timelines decreased from 798 days for applications dated in 2020 to 364 days for applications dated in 2024. For health systems, PBMs, and specialty pharmacies, shorter timelines can reduce the time between a product appearing on a watch list and needing a conversion plan.

Wezlana’s label coverage turns interchangeability into a real conversion decision

Healthcare Purchasing News reported that the FDA approved Wezlana on Oct. 31, 2023, granting it interchangeability with Stelara across several high-volume inflammatory indications. For adults, the FDA-approved indications include moderate to severe plaque psoriasis in patients who qualify for phototherapy or systemic treatment, active psoriatic arthritis, Crohn’s disease that is moderately to severely active, and ulcerative colitis that is moderately to severely active. The same report said the approvals for pediatric patients ages 6 and older cover moderate to severe plaque psoriasis and active psoriatic arthritis.

For enterprise buyers, the operative word is “interchangeable,” not “biosimilar.” An interchangeable biosimilar is a biosimilar that may be substituted for the reference product without consulting the prescriber, subject to state pharmacy laws, according to Healthcare Purchasing News. Healthcare Purchasing News also reported FDA officials said biosimilars can increase access and that FDA approval standards mean patients and providers can expect the same safety and effectiveness from both a biosimilar and an interchangeable biosimilar as they would for the reference product.

The FDA’s interchangeable biosimilar pipeline has accelerated, and approvals are bunching

Springer’s analysis, based on the FDA Purple Book archive as of September 2025 and FDA approval letters, counted 26 FDA-approved interchangeable biosimilars since 2020. Springer reported that 19 were approved between January 2024 and September 2025.

The same paper identified two manufacturer strategies: pursuing interchangeability in a concurrent submission (17 cases) or seeking it later after an initial biosimilar approval (9 cases). For pharmacy and payer operations teams, that split shows up as unpredictability in “when” a biosimilar becomes eligible for pharmacy-level substitution. Concurrent submissions compress that uncertainty.

The approval-time data point is the one that should change internal timelines. Springer reported average approval timelines decreased from 798 days for applications dated in 2020 to 364 days for applications dated in 2024. That does not automatically translate to immediate uptake, but it can mean that organizations that review biosimilar readiness quarterly may find themselves making decisions after the market has already started moving.

Where the operational work shifts: formulary, IT build, and state-by-state substitution

Interchangeability is often described in regulatory terms, but the day-to-day burden lands across pharmacy operations, IT, and procurement. Healthcare Purchasing News’ description of pharmacy-level substitution “subject to state pharmacy laws” is the practical catch: multi-state health systems and national pharmacy organizations have to manage different substitution permissions and documentation requirements across their footprint.

In practice, Wezlana-like approvals force a chain of small, failure-prone tasks that decide whether savings show up. Drug file and item master maintenance, NDC mapping and crosswalks (particularly when both reference and biosimilar products remain active), prior authorization rule updates, claims edits, and EMR preference list changes all have to be aligned with formulary policy. None of those steps are optional when a product can be substituted at the pharmacy level.

Springer’s paper also described the FDA’s June 2024 draft guidance on interchangeability as relaxing approval criteria by focusing on analytic rather than clinical findings. The study also reported that all currently approved interchangeable biosimilars completed pre-approval switching studies. For operators, the implication is practical: development timelines and launch timing may keep tightening, increasing the value of standing conversion playbooks.

Where this lands in 2026 contracting and conversion planning

The immediate takeaway for procurement leaders is not that another ustekinumab product exists. It is that interchangeability is increasingly arriving as part of the first commercial posture, and approvals are coming faster, according to Springer’s dataset. That changes how teams should sequence contracts, operational readiness, and patient communication.

• Build a standing “interchangeable launch” checklist that starts with state substitution requirements in the markets served and ends with EMR and pharmacy system preference changes, because Healthcare Purchasing News notes substitution is state-law dependent.
• Ask manufacturers and wholesalers whether interchangeability is being pursued concurrently or later. Springer found concurrent submission for interchangeability in 17 cases and delayed pursuit in 9 cases, and that difference affects conversion timing and rebate guarantee language.
• Tighten monitoring cadence for the Purple Book and FDA letters if the organization is still reviewing biologic class conversions once or twice a year. Springer reported average approval timelines decreased to 364 days for applications dated in 2024.
• For ustekinumab specifically, validate which dispensing channels will drive substitution and align the PA and claims edits accordingly. Interchangeability can shift volume only if payer and pharmacy edits match formulary intent.