Investigation of sterile hydrogels as topical vehicles for APOSEC TM , a stressed peripheral blood mononuclear cell secretome for the treatment of poorly healing wounds

Abstract APOSECTM, a complex mixture of secreted proteins, lipids, and extracellular vesicles from stressed peripheral blood monocytes, is currently in clinical trials for the treatment of chronic, poorly healing wounds. When applied to open wounds, 1 mL reconstituted APOSECTM lyophilisate is syringe-mixed with 3 g sterile hydrogel prior to administration. This study investigates the pharmaceutical performance of this novel administration system. A gel formulation (APOgel) was developed for terminal sterilisation in pre-filled syringes with post-sterilisation viscosity (∼325-350□Pa*s at 1□s-1) comparable to a commercial benchmark gel. Syringe mixing of APOgel with a liquid APOSECTM surrogate (3:1) reduced viscosity by ∼67% but was highly reproducible across different operators (CV < 6%). Administration of three sequential dose units of the mixture from the syringe revealed an ∼20% higher content of active ingredients in the first and final dispensed compared to the middle unit, indicating non-uniform mixing in the closed syringe system. In vitro release studies over 72□h showed a 32% and 48% higher release of a small molecule marker and total proteins from the sterile APOgel compared to the benchmark gel as well as more pronounced gel swelling. However, efficacy studies in a murine wound healing model showed no significant difference between APOgel and the benchmark. These findings indicate that terminal sterilisation of gels for topical applications may provide benefits for more rapid release of active agents but syringe mixing of gels and a liquid requires optimisation to ensure uniform drug distribution. Highlights An autoclavable hydrogel for APOSECTM delivery was developed A novel syringe-mixing system for combining a gel with a liquid with subsequent dispensing of different volume units showed non-homogenous active ingredient distribution Final optimised APOSECTM-APOgel formulation maintains functional wound-healing efficacy Competing Interest Statement Equipment, drugs, or supplies was provided by Aposcience AG. Hendrick Jan Ankersmit reports a relationship with Aposcience AG that includes: board membership. H.J. Ankersmit has patent #EP2201954 issued to APOSCIENCE AG. Hendrick Jan Ankersmit, Michael Mildner and Sylwia Gazda-Miarecka are respectively CEO, CSO and Head of Quality Assurance of APOSCIENCE AG which developed and produces the secretome and is the sponsor of this study. Nina Langoth-Fehringer, Hannes Kuehtreiber and Melanie Salek are also affiliated with APOSCIENCE AG. All other authors declare no competing interests. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.