Elastomeric closures for biosimilars: the same rules, with reduced tolerance for gaps

The regulatory position 

From a regulatory standpoint, elastomeric components are expected to be assessed for biosimilars using the same core principles applied to originator products - covering functional suitability, extractables and leachables (E&L), and container closure integrity (CCI). 

USP <382> outlines an approach to functional suitability assessment of elastomeric components for injectable drug products. Across regulatory authorities (e.g., U.S. FDA, EMA, CDSCO), applicants are generally expected to justify elastomer selection and demonstrate suitability for the intended use across the product lifecycle; submission structure and emphasis may vary by jurisdiction. 

Supplier-generated data can support early risk assessment, but it does not replace system-level, product-specific evaluation of the assembled container-closure system. The regulatory burden remains with the applicant, and the work typically becomes harder when programs span multiple formats and markets. 

Where biosimilar programs are specifically exposed 

1. Format migration without planned closure continuity
   Many programs begin in the same presentation as the reference product, but the commercial target may shift to a prefilled syringe or autoinjector. If elastomer formulation, coating, or manufacturing standard changes between formats, existing E&L data may not be bridgeable and additional compatibility and justification work may be required. 

2. Dual-market filing complexity
   Many developers pursue domestic approval alongside, or shortly after, regulatory submissions to FDA or EMA. In practice, teams often need a coherent E&L and CCI strategy that can be adapted across agency expectations, supported by clear change control and documentation. 

The platform approach 

With a platform approach, elastomeric components, a defined manufacturing quality standard, E&L characterization, and supplier relationship are established once. Format transitions may reduce the need for requalification when the formulation/coating and relevant specifications remain unchanged (subject to product-specific assessment). The regulatory package can follow the program, rather than being rebuilt at each step. 

Timing and next step 

Elastomeric closure decisions are typically most flexible early in development, when format and scale are still evolving. If you are planning format migration or parallel filings, it may help to pressure-test the closure strategy and supporting documentation early - before timelines are committed.