Development of N-Acetylated Dipalmitoyl-S-Glyceryl Cysteine Analogs as Efficient TLR2/TLR6 Agonists

Cancer vaccine is a promising immunotherapeutic approach to train the immune system with vaccines to recognize and eliminate tumors. Adjuvants are compounds that are necessary in cancer vaccines to mimic an infection process and amplify immune responses. The Toll-like receptor 2 and 6 (TLR2/TLR6) agonist dipalmitoyl-S-glyceryl cysteine (Pam(2)Cys) was demonstrated as an ideal candidate for synthetic vaccine adjuvants. However, the synthesis of Pam(2)Cys requires expensive N-protected cysteine as a key reactant, which greatly limits its application as a synthetic vaccine adjuvant in large-scaled studies. Here, we report the development of N-acetylated Pam(2)Cys analogs as TLR2/TLR6 agonists. Instead of N-protected cysteine, the synthesis utilizes N-acetylcysteine to bring down the synthetic costs. The N-acetylated Pam(2)Cys analogs were demonstrated to activate TLR2/TLR6 in vitro. Moreover, molecular docking studies were performed to provide insights into the molecular mechanism of how N-acetylated Pam(2)Cys analogs bind to TLR2/TLR6. Together, these results suggest N-acetylated Pam(2)Cys analogs as inexpensive and promising synthetic vaccine adjuvants to accelerate the development of cancer vaccines in the future.