Policy Impact: FDA’s Interchangeability Designation Expands Biosimilar Access
The US Food and Drug Administration’s (FDA) first approval of an interchangeable biosimilar in 2021 marked a pivotal moment in health policy. Insulin glargine, marketed as Semglee and its biosimilar insulin glargine-yfgn, was granted interchangeable status, allowing pharmacists to substitute it for the branded originator without requiring prescriber intervention. A new economic evaluation provides evidence that this designation meaningfully altered prescription trends, offering insights into how regulatory designations can influence market adoption and patient access.
The study analyzed prescription data from IQVIA’s National Prescription Audit and PayerTrak, covering September 2019 through June 2024. Researchers applied interrupted time-series methods to assess changes before and after the FDA’s decision. The results showed a sharp discontinuous increase in biosimilar dispensing immediately following interchangeability approval in November 2021. Specifically, combined dispensing of Semglee and insulin glargine-yfgn rose by more than 47 000 prescriptions, representing a significant jump that was not mirrored across the broader insulin glargine market. This suggests the designation itself played a critical role in driving utilization.
Importantly, the gains extended across all dispensing channels. Retail, mail order, and long-term care pharmacies all registered statistically significant increases in biosimilar dispensing. Even in segments where formulary adjustments favored Semglee, the biosimilar insulin glargine-yfgn also experienced an adoption boost, underscoring the independent effect of interchangeability. When data were stratified by payer type, utilization patterns revealed especially strong uptake of insulin glargine-yfgn in Medicare Part D, Medicaid, and cash-paying segments. This points to interchangeability’s potential to expand access for patients across diverse coverage types, including those most sensitive to out-of-pocket costs.
The findings highlight a broader policy implication: interchangeability can accelerate biosimilar substitution and help generate meaningful cost savings within the US health care system. For insulin, a drug class frequently criticized for its high prices and barriers to affordability, the approval of interchangeable biosimilars represents a key mechanism for promoting competition. Beyond automatic substitution, the designation may also enhance physician and patient trust, addressing common hesitations about transitioning to biosimilars.
The FDA’s decision to grant interchangeable status to insulin glargine biosimilars catalyzed a marked rise in dispensing, offering early proof that interchangeability designations can meaningfully expand biosimilar use. For managed care organizations, these findings highlight the value of leveraging interchangeability to promote cost-effective prescribing and enhance patient access. The ability to substitute at the pharmacy level—without additional administrative burden—creates new opportunities to lower drug spend while maintaining therapeutic continuity. As more biologics enter the market with interchangeable status, payer strategies that encourage adoption through formulary design, provider education, and patient engagement will be central to capturing the full economic and clinical benefits of biosimilars.
Reference
Murphy SJ, Holtkamp NC. Prescription dispensing for insulin glargine after interchangeable biosimilar designation. JAMA Health Forum. 2025;6(5):e250033. Published 2025 May 2. doi:10.1001/jamahealthforum.2025.0033
