Simplified Monopalmitoyl Toll‐like Receptor 2 Ligand Mini‐UPam for Self‐Adjuvanting Neoantigen‐Based Synthetic Cancer Vaccines

• Published in: Chembiochem : a European journal of chemical biology Vol. 22; no. 7; pp. 1215 - 1222
• Main Authors: Ende, Thomas C., Heuts, Jeroen M. M., Gential, Geoffroy P. P., Visser, Marten, Graaff, Michel J., Ho, Nataschja I., Jiskoot, Wim, Valentijn, A. Rob P. M., Meeuwenoord, Nico J., Overkleeft, Herman S., Codée, Jeroen D. C., Burg, Sjoerd H., Verdegaal, Els M. E., Marel, Gijsbert A., Ossendorp, Ferry, Filippov, Dmitri V.
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 06.04.2021; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Additives; Amino acids; Antigens; Biochemistry & Molecular Biology; Cancer; Cancer vaccines; Cell therapy; Chemistry, Medicinal; Conjugates; Covalence; dendritic cells; Epitopes; Immunogenicity; Immunostimulation; Immunotherapy; Life Sciences & Biomedicine; Ligands; lipopeptides; Major histocompatibility complex; Melanoma; Neoantigens; neoepitopes; Peptides; Pharmacology & Pharmacy; Physicochemical properties; Receptors; Science & Technology; Solid phase methods; Solid phase synthesis; Synthetic peptides; TLR2 ligand; TLR2 protein; Toll-like receptors; Tumors; Vaccines; IMMUNITY; dendritic cells; neoepitopes; cancer vaccines; lipopeptides; TLR2 ligand; solid-phase synthesis
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.202000687

Synthetic vaccines, based on antigenic peptides that comprise MHC−I and MHC‐II T‐cell epitopes expressed by tumors, show great promise for the immunotherapy of cancer. For optimal immunogenicity, the synthetic peptides (SPs) should be adjuvanted with suitable immunostimulatory additives. Previously, we have shown that improved immunogenicity in vivo is obtained with vaccine modalities in which an SP is covalently connected to an adjuvanting moiety, typically a ligand to Toll‐like receptor 2 (TLR2). SPs were covalently attached to UPam, which is a derivative of the classic TLR2 ligand Pam3CysSK4. A disadvantage of the triply palmitoylated UPam is its high lipophilicity, which precludes universal adoption of this adjuvant for covalent modification of various antigenic peptides as it renders the synthetic vaccine insoluble in several cases. Here, we report a novel conjugatable TLR2 ligand, mini‐UPam, which contains only one palmitoyl chain, rather than three, and therefore has less impact on the solubility and other physicochemical properties of a synthetic peptide. In this study, we used SPs that contain the clinically relevant neoepitopes identified in a melanoma patient who completely recovered after T‐cell therapy. Homogeneous mini‐UPam‐SP conjugates have been prepared in good yields by stepwise solid‐phase synthesis that employed a mini‐UPam building block pre‐prepared in solution and the standard set of Fmoc‐amino acids. The immunogenicity of the novel mini‐UPam‐SP conjugates was demonstrated by using the cancer patient's T‐cells. Less lipophilic ligands: A novel TLR2 ligand has been designed and synthesized to be subsequently conjugated with synthetic peptides containing clinically relevant neoepitopes. By treating HEK‐TLR2 cells, human moDCs and antigen specific human T‐cells with these new constructs, the immunogenic potential of the new TLR2 ligand and the conjugation of TLR ligands with neoepitopes was assessed.