Spergualin

15-Deoxyspargualin (DSG) is a synthetic analogue of spergualin isolated from the culture filtrate of Bacillus laterosporus. It shows a strong immunosuppressive effect by antiproliferating action inhibiting the IL-2-stimulated maturation of T cells from the G0/G1 phases to the S and G2/M phases. Hsc70, a constitutive member of Hsp70 was identified as the immunophilin of DSG by Nadlar et al. In allogeneic transplantation of rat heart and dog kidney, DSG was definitely proved to prevent rejection and to rescue ongoing rejection. Our multicenter clinical trials on DSG showed that the percent efficacy to reverse acute rejection was 70-80%, and 600 days graft survival was 90% in the cases effectively treated with DSG at acute rejections. The combined use of DSG with methylprednisolone to treat acute rejection and the use of DSG to treat rejections in chronic phases were reported as the beneficial uses of DSG.

Spergualin is a natural product that exhibits immunosuppressive, anti-tumor and anti-bacterial activities. Its derivatives, such as 15-deoxyspergualin (15-DSG), have been clinically approved for acute allograft rejection. However, the reported syntheses are cumbersome (>10 steps) and they suffer from low overall yields (∼0.3% to 18%). Moreover, spergualin and its derivatives are chemically unstable and rapidly hydrolyzed in aqueous buffer. Here, we have re-explored these issues and report a modified synthetic route with significantly improved overall yield (∼31% to 47%). The key transformation is a microwave-accelerated Ugi multi-component reaction that is used to generate the peptoid core in a single step. Using the products of this route, we found that modifications of the hemiaminal significantly increased chemical stability. Thus, we anticipate that this synthetic route will improve access to biologically active 15-DSG derivatives.

PURPOSE OF REVIEW: In the past, recommendations for the treatment of Wegener's granulomatosis were primarily based on findings reported from open-label clinical trials. Results from several randomized controlled trials in patients with Wegener's granulomatosis and other antineutrophil cytoplasm antibody-associated vasculitides have recently been reported that have a great impact on patient care.

In 1951, we were pioneers in initiating screening of antitumor agents from microbial metabolites. We discovered bleomycin in 1962 and aclacinomycin in 1975. Peplomycin, a derivative of bleomycin, and pirarubicin, a tetrahydropyranyl derivative of doxorubicin, were also studied. All of them have been clinically used for the treatment of cancer. Using new screening methods, we isolated spergualin in 1982. This agent exhibited immunosuppressive activity as well as antitumor activity. Deoxyspergualin, a derivative of spergualin, is now clinically used for the treatment of acute rejection after kidney transplantation. Bestatin was screened as an inhibitor of aminopeptidase B in 1976. It binds to the aminopeptidases located on the cell membrane of immunocompetent cells and modulates immune responses. It is now used for the treatment of acute non-lymphocytic leukemia. Microbial metabolites will become more important as a source of anticancer drugs in the future.