Key Takeaways
- 62% of specialty drug launches in 2025 faced a formulary restriction or prior authorisation requirement within 90 days, up from 41% in 2022, according to a 340-respondent survey by a major benefits consultancy.
- Biosimilar penetration in oncology supportive care has reached 78% by volume, yet payer leverage in high-acuity biologics remains structurally constrained by limited interchangeability designations.
- IRA negotiation timelines are compressing manufacturer planning windows by an estimated 14 to 18 months, forcing earlier health-economic modelling decisions with less real-world evidence available.
- Pharmacy benefit managers controlling more than 80% of covered lives have shifted step-therapy protocols to apply at the point of initial prescribing rather than at renewal, a change that materially alters launch-year revenue forecasts.
The conventional wisdom in drug pricing holds that biosimilar competition moderates payer aggression: supply increases, prices fall, formulary battles ease. That logic held broadly through 2021 and 2022. It is failing in measurable ways today. A 340-respondent benefits consultancy survey published in February 2026 found that prior authorisation denial rates for newly launched specialty biologics rose to 34% at first submission, up from 22% three years prior. Payers are not retreating as biosimilar volumes climb; in several therapeutic categories, they are escalating. Understanding why requires looking past headline penetration figures to the structural mechanics underneath them, because the divergence is not random. It is being driven by three identifiable and durable forces.
The IRA Has Shifted the Centre of Gravity
The Inflation Reduction Act's negotiation provisions, now in their second active cycle, have done something few anticipated at the legislation's passage: they have concentrated payer leverage on precisely the drugs where manufacturers believed they had the most pricing power. By targeting high-spend, single-source small-molecule drugs and biologics with no biosimilar competition, the IRA mechanism has validated the payer argument that list prices on these agents were structurally inflated. The head of market access at a mid-size US specialty pharma company described it plainly in a January 2026 industry forum: "The IRA didn't just set prices on ten drugs. It gave every formulary committee a political permission structure to push harder on the next hundred."
The knock-on effect is measurable in contracting timelines. Manufacturers report that payers are now initiating formulary placement negotiations an average of five months earlier in the product lifecycle, before Phase III readouts in several documented cases. That compression forces pricing decisions with thinner evidence packages, weakening the clinical differentiation arguments that have historically anchored premium positioning. A market access director at a large European biologics group noted that two of their 2025 US launches entered payer negotiation before the label was finalised.
Interchangeability Gaps Are Creating Asymmetric Battlegrounds
Biosimilar penetration statistics obscure a critical fracture in the market. In therapeutic areas where the FDA has granted interchangeability designations, substitution at the pharmacy level has driven brand erosion of 40 to 65% within 18 months of biosimilar entry, consistent with historical small-molecule generic patterns. But in high-acuity biologics, particularly monoclonal antibodies used in autoimmune and oncology indications, interchangeability designations remain rare. As of March 2026, fewer than 12% of approved biosimilars carry an interchangeability designation, according to FDA Orange Book data. That gap is not closing quickly. The clinical data requirements for interchangeability, particularly immunogenicity evidence across patient subpopulations, create a regulatory burden that smaller biosimilar developers frequently cannot bear.
Payers know this. Where substitution cannot happen automatically at the pharmacy counter, formulary exclusions and step-therapy requirements become the primary lever. The result is a bifurcated market where payer behaviour looks radically different depending on the interchangeability status of competing products, a distinction that aggregate penetration statistics completely obscure.
"We modelled three reimbursement scenarios for our lead asset in 2024. By the time we launched in Q1 2026, all three were obsolete. The payer landscape had shifted in ways our HEOR team simply had no historical precedent to anticipate."
Chief Regulatory Officer at a large European pharma group (survey respondent)
PBM Protocol Shifts Are Landing Earlier in the Patient Journey
Perhaps the most operationally disruptive change in the current cycle is the repositioning of step-therapy requirements. Historically, step therapy applied most aggressively at the point of therapy switch or annual renewal. The three largest pharmacy benefit managers, controlling a combined 83% of commercially insured covered lives in the US, have in the past 18 months migrated step-therapy triggers to the point of initial prescribing for a defined list of specialty categories. For manufacturers, this is not a marginal administrative change. It means that launch-year uptake curves, which underpin investor guidance and commercial team compensation structures, now carry a structural drag that did not exist in prior product cycles.
The categories most affected by initial-prescribing step therapy include dermatology biologics, JAK inhibitors, and CGRP antagonists used in migraine prevention. In a February 2026 analysis of 47 specialty launches since 2023, a healthcare analytics firm found that products in these categories reached 50% of projected 12-month volume an average of 4.2 months later than comparable launches from the 2019 to 2021 cohort.
Three dynamics are worth tracking closely as this cycle continues to develop:
- Interchangeability designation velocity: Any acceleration in FDA granting interchangeability status to pending biosimilar applications would rapidly shift leverage in categories currently protected by the substitution gap, altering competitive dynamics within 12 to 24 months of a designation.
- IRA negotiation scope expansion: The statute's provisions allow negotiation eligibility criteria to broaden in subsequent cycles. If biologics with existing biosimilar competition enter the negotiation pool, the current assumption that biosimilar availability confers pricing stability will require fundamental revision.
- State-level prior authorisation reform: Twenty-three states have passed or are actively considering legislation to limit denial timelines and mandate clinical criteria transparency. If federal legislation follows, the administrative leverage PBMs currently exercise through prior authorisation processes could be materially constrained within two to three years.
The broader strategic implication is this: manufacturers who built their market access models on the assumption that biosimilar market maturation would gradually reduce payer friction are working from a map that no longer matches the terrain. The structural forces now operating, IRA negotiation precedent, interchangeability scarcity in high-acuity categories, and PBM protocol repositioning, are not cyclical. They represent a durable reset of the baseline conditions under which specialty biologics achieve and sustain reimbursement. Organisations that recognise this shift and rebuild their HEOR, contracting, and launch sequencing strategies accordingly will have a material structural advantage over those still modelling from pre-2023 baselines. The window for that recalibration is narrowing with each new product cycle.
