Enhanced Antitumor Immunity of a Globo H‐Based Vaccine Enabled by the Combination Adjuvants of 3D‐MPL and QS‐21

Globo H, a specific carbohydrate antigen overexpressed on various human malignancies, has attracted considerable interest as an antigenic target for anticancer vaccine development. Despite several Globo H‐based carbohydrate vaccines that have been designed, efficient access to Globo H hexasaccharide antigen and development of powerful adjuvants for enhancing antitumor immunity remain challenging. Herein, we reported a streamlined chemoenzymatic approach to prepare this hexasaccharide antigen, relying on chemical synthesis of Gb5 pentasaccharide by a stereoconvergent [2+3] strategy and subsequent enzymatic α‐fucosylation to easily install α1,2‐fucose residue. Separately, a modular assembly approach to efficiently synthesize 3‐O‐deacyl‐monophosphoryl lipid A (3D‐MPL) was developed by the integration of stereocontrolled glycosylation, regioselective acylation, site‐specific phosphorylation, and facile global deprotection. After efficient construction of Globo H‐CRM197 conjugate, we conducted systematic immunological evaluations of Globo H‐CRM197 formulated with various adjuvants and adjuvant combinations, comprising saponin QS‐21, synthetic 3D‐MPL and α‐galactosylceramide derivative S34. The results revealed that Globo H‐CRM197 conjugate adjuvanted with QS‐21 and 3D‐MPL elicited robust IgG2a and IgG3 antibody responses and Th1 cellular immunity in mice. Moreover, antibodies induced by this formulation effectively bound to Globo H‐positive MCF‐7 cancer cells and exhibited superior complement‐dependent cytotoxicity and antibody‐dependent cellular phagocytosis, holding promise for further development of effective anticancer vaccines.