Lyophilization cycle development for interleukin-2

The effects of temperature and pressure variation on the lyophilization of interleukin-2 (IL-2) were studied. The human recombinant IL-2 used in this study was synthesized in and purified from E. coli, formulated, and then submitted to experimental lyophilization procedures. The collapse temperature of the formulation was first determined to be -25 degrees C by differential scanning calorimetry. The effects of chamber pressure and shelf temperature on IL-2 during lyophilization were evaluated. Lyophilization chamber pressures were varied from 100 mu to 300 mu in combination with the different chamber pressures. Lyophilized cake quality was assessed by evaluating three of its properties: residual moisture, by the Karl Fischer method; the monomeric content of the protein, by RP-HPLC; and oligomeric content, by SDS-PAGE. Process uniformity was checked by determining residual moisture in cakes collected from various locations in the chamber. The experimental data show that IL-2 can be lyophilized in a pilot unit within 30 hours. The IL-2 lyophilized at various primary drying conditions retained its purity and potency throughout the stability study period (12 months).