FK 506 is a novel macrolide immunosuppressant which is more potent tha
n cyclosporine. Recent evidence that cyclosporine has efficacy in the
treatment of inflammatory bowel disease (IBD) led to the development o
f a new protocol using FK 506. FK 506 has been shown to produce substa
ntially greater survival in liver transplant patients than cyclosporin
e, with fewer side effects. Inhibition of lymphocyte production of cyt
okines interleukin (IL)-2, IL-3 and interferon gamma requires 10 to 10
0 times greater concentrations of cyclosporine than of FK 506. Rejecti
on episodes are less frequent and side effects fewer in patients recei
ving heart, kidney or liver transplants following treatment with FK 50
6 than with cyclosporine. Thus, the development of a new, potent immun
osuppressive agent with a greater safety profile than cyclosporine pro
vides a new opportunity to identify an effective therapy for patients
with IBD resistant to corticosteroids.