An analysis of variability in the manufacturing of dexosomes: Implications for development of an autologous therapy

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Abstract
Dexosomes are nanometer‐size vesicles released by dendritic‐cells, possessing much of the cellular machinery required to stimulate an immune response (i.e. MHC Class I and II). The ability of patient‐derived dexosomes loaded with tumor antigens to elicit anti‐tumor activity is currently being evaluated in clinical trials. Unlike conventional biologics, where variability between lots of product arises mostly from the manufacturing process, an autologous product has inherent variability in the starting material due to heterogeneity in the human population. In an effort to assess the variability arising from the dexosome manufacturing process versus the human starting material, 144 dexosome preparations from normal donors (111) and cancer patients (33) from two Phase I clinical trials were analyzed. A large variability in the quantity of dexosomes (measured as the number of MHC Class II molecules) produced between individual lots was observed ( > 50‐fold). An analysis of intra‐lot variability shows that the manufacturing process introduces relatively little of this variability. To identify the source(s) of variability arising from the human starting material, distributions of the key parameters involved in dexosome production were established, and a model created. Computer simulations using this model were performed, and compared to the actual data observed. The main conclusion from these simulations is that the number of cells collected per individual and the productivity of these cells of are the principal sources of variability in the production of Class II. The approach described here can be extended to other autologous therapies in general to evaluate control of manufacturing processes. Moreover, this analysis of process variability is directly applicable to production at a commercial scale, since the large scale manufacture of autologous products entails an exact process replication rather than scale‐up in volume, as is the case with traditional drugs or biologics.