Aim: Stabilization of critical reagents by freeze-drying would facilitate storage and transportation at ambient temperatures, and simultaneously enable constant reagent performance for long-term bioanalytical support throughout drug development. Freeze-drying as a generic process for stable performance and storage of critical reagents was investigated by establishing an universal formulation buffer and lyophilization process. Results: Using a storage-labile model protein, formulation buffers were evaluated to preserve reagent integrity during the freeze-drying process, and to retain functional performance after temperature stress. Application to critical reagents used in pharmacokinetics and anti-drug antibodies assays demonstrated stable functional performance of the reagents after 11 month at +40°C. Conclusion: Stabilization and storage of critical assay reagents by freeze-drying is an attractive alternative to traditional deep freezing.