An improved synthesis of the hexasaccharide MBr1 antigen (globo-H) is reported. Enhanced efficiency in the synthesis was necessary for the scale up production of globo-H, in order to advance globo-H based anticancer vaccines to clinical trials. The key features of the improved synthesis include preactivation-based glycosylations and a revised iodosulfonimidation/ rearrangement.The glycosphingolipid globo-H (1, Figure 1), first isolated by Hakomori and colleagues from the breast cancer cell line MCF-7, 1 is recognized by the monoclonal antibody MBr1. 2 This human breast cancer-associated antigen was found to be distinctively overexpressed on the surfaces of a variety of other epithelial cancer cells such as prostate, ovary, lung, colon, and small cell lung cancers. 3 For this reason, the globo-H antigen has played an important role in our ongoing carbohydrate-based cancer vaccine program. 4 Of particular interest to our laboratory was a recent report, indicating that globo-H and SSEA3 -the pentasaccharide precursor of globo-H -are also overexpressed in breast cancer stem cells. Interestingly, when co-administered with an immunological adjuvant (α-galactosylceramide), a globo-H based vaccine induces antibodies against both globo-H and SSEA3. 5 In the light of the fact that cancer stem cells are often responsible for relapse and metastasis of cancerous tissues,6 it is envisioned that globo-H based therapy might form the basis of an important new direction in cancer treatment. Indeed, the globo-H vaccine, 2, synthesized in our laboratories as a glycoconjugate appended to immunogenic carrier protein, has shown promise as a potential breast and prostate cancer vaccine, in preclinical, and even clinical settings.4a-e More recently, we also disclosed the synthesis and preclinical evaluation of the unimolecular pentavalent vaccine 34f-g, displaying globo-H and other antigens known to be overexpressed on prostate and breast cancer cell surfaces. The thought was to construct a single entity antigen system which reflects the actual degree of carbohydrate heterogeneity associated with most cancers. 7 Nonetheless, the accessibility of such complex carbohydrate antigens remained as an important question. Globo-H isolated from human cancer tissue collections is typically limited to sub-milligram levels, which impedes broader * s-danishefsky@ski.mskcc.org .Supporting Information Available: NMR spectra for 6, 7, 8, 9, and 10. This material is available free of charge via the Internet at http://pubs.acs.org. Figure 2). Although this concise and stereoselective strategy allows rapid access to globo-H, some steps, particularly those leading to DEF donor 7, still require further optimization if we are to secure the globo-H antigen in amounts required for our ongoing clinical trials with globo-H, both in monovalent and multivalent settings. NIH Public AccessIn this regard, we report herein our efforts to seek a much improved synthesis of the DEF donor 7 and ABC accepter 8. As described in our earlier report, 4b,13 DEF trisac...

Fully synthetic, carbohydrate-based antitumor vaccine candidates have been synthesized in highly clustered modes. Multiple copies of tumor-associated carbohydrate antigens, Tn and STn, were assembled on a single cyclic peptide scaffold in a highly convergent manner. Ring-closing metathesis-mediated incorporation of an internal cross-linker was also demonstrated. In particular, this rigidified cross-linked construct would enhance a cluster-recognizing antibody response by retaining an appropriate distance between glycans attached to the peptide platform. Details of the design and synthesis of highly clustered antigens are described herein.

A series of fluorinated analogs of malachite green (MG) have been synthesized and their toxicity to Saccharomyces cerevisiae and a human ovarian epithelial cell line examined. The toxicity profiles were found to be different for these two species. Two analogs, one with 2,4-difluoro substitution and the other with 2-fluoro substitution seem to be the most promising analogs because they showed the lowest toxicity to the human cells.

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