Kilo-Scale GMP Synthesis of Renewable Semisynthetic Vaccine-Grade Squalene

Emulsions of the triterpene squalene ((6E,10E,14E,18E)-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene, CAS 111-02-4) have been used as adjuvants in influenza vaccines since the 1990s. Traditionally sourced from shark liver oil, the overfishing of sharks and concomitant reduction in the oceanic shark population raise sustainability issues for a vaccine adjuvant-grade squalene. We report a semisynthetic route to squalene meeting current pharmacopeial specifications for use in vaccines that leverages the ready availability of trans-β-farnesene ((6E)-7,11-dimethyl-3-methylene-1,6,10-dodecatriene, CAS 18794-84-8), manufactured from sustainable sugar cane via a yeast fermentation process. The scalability of the proposed route was verified by a kilo-scale GMP synthesis. We also report data demonstrating the synthesized semisynthetic squalene's physical stability and biological activity when used in a vaccine adjuvant formulation.