Synthetic and Immunological Studies on Clustered Modes of Mucin-Related Tn and TF O-Linked Antigens: The Preparation of a Glycopeptide-Based Vaccine for Clinical Trials against Prostate Cancer

The syntheses of two tumor-associated carbohydrate antigens, Tn and TF, have been achieved using glycal assembly and cassette methodologies. These synthetic antigens were subsequently clustered (c) and immunoconjugated to a carrier protein (KLH or BSA) or a synthetic lipopeptide (pam) for immunological study. Three Tn conjugates were used to vaccinate groups of mice, and all preparations proved to be immunogenic. The Tn(c) covalently linked to KLH ( 27 −KLH) plus the adjuvant QS-21 was the optimal vaccine, inducing high median IgM and IgG titers against Tn(c) by ELISA. These antibodies were strongly reactive with the Tn(c) positive human colon cancer cell line LS-C but not the Tn(c) negative colon cancer cell line LS-B by FACS. The antibodies' reactivities with natural antigens were inhibited with synthetic Tn(c) but not with structurally unrelated compounds. On the basis of these results, vaccines containing 27 −KLH and 30 −pam plus QS-21 are being tested in patients with prostate cancer.