Design, Synthesis, and Preliminary Immunological Studies of MUC1-Based Antitumor Vaccines Adjuvanted with R- and S‑FSL‑1

Fibroblast stimulating lipopeptide 1 (FSL-1) is the ligand of TLR2 and TLR6 and can be used as the vaccine adjuvant to prepare antitumor vaccines. However, FSL-1 is a stereoisomeric mixture that contains the R stereoisomer and S stereoisomer, and it is still unclear which stereoisomer has better adjuvant activities. In this work, we designed and synthesized MUC1-based antitumor vaccines adjuvanted with the stereoisomers R-FSL-1 and S-FSL-1, which were synthesized from the stereoisomeric building blocks R-Fmoc-Pam₂Cys-OH and S-Fmoc-Pam₂Cys-OH, respectively. Immunological evaluation indicated that both R-FSL-1 and S-FSL-1 can be used as adjuvants for the construction of MUC1-based antitumor vaccines, with R-FSL-1 showing a better adjuvant effect than S-FSL-1.