Evaluation of alternative diluents for clinical use of collagenase clostridium histolyticum (CCH‐aaes)

BACKGROUND: Collagenase clostridium histolyticum (CCH‐aesthetic formulation [CCH‐aaes]; QWO™ [Endo Aesthetics, Malvern PA, USA] is approved as a subcutaneous injection for treatment of cellulite. In the aesthetic practice, dilution of marketed products is commonly employed to tailor treatments to individual patients or off‐label locations. Dilution beyond the 0.23 mg/ml achievable with the proprietary diluent supplied with the CCH‐aaes lyophilized powder requires diluents readily available in clinic. AIM: To characterize the functionality and stability of CCH‐aaes when reconstituted and/or diluted with alternative diluents, including normal saline, bacteriostatic saline, and/or proprietary diluent. PATIENTS/METHODS: Each dilution was assessed for purity using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE), activity using collagenase (AUX‐I) and gelatinase (AUX‐II) assays, and aggregation using size‐exclusion chromatography. RESULTS: When reconstituted with either saline or proprietary diluent, and diluted with proprietary diluent or saline, purity, activity, and stability of CCH‐aaes is maintained for up to 24 h at 5°C or 25°C. In contrast, use of bacteriostatic saline to reconstitute and/or dilute CCH‐aaes results in up to a 40% decrease in activity and aggregation of 5.3% of CCH‐aaes protein. Importantly, inclusion of 2% lidocaine and 1:200 000 epinephrine does not negatively impact CCH‐aaes purity, concentration, or activity for up to 24 h at 5°C or 25°C. CONCLUSIONS: From an efficacy and safety perspective, CCH‐aaes must not be/should not be reconstituted and/or diluted with bacteriostatic saline to avoid injection of protein aggregates. Ideally, CCH‐aaes should be reconstituted in proprietary diluent: further dilution with normal saline and addition of lidocaine and epinephrine is acceptable.