1: J Pharmacol Exp Ther 1998 Mar;284(3):1074-81
In vitro immunosuppressive activity, isolation from pig liver microsomes
and identification by electrospray ms-ms of a new FK-506 C19-C20 epoxide
metabolite.
Lhoest G, Dieden R, Verbeeck RK, Maton N, Ingendoh A, Latinne D
Department of Pharmaceutical Sciences, UCL, Brussels, Belgium.
In order to mediate their effects, cyclosporin A and FK-506 must each bind
with high affinity to a cytosolic target protein that belongs to the immunophilin
group. FK-506 forms complexes with the FK-506 binding protein FKBP, mainly
FKBP-12, and these complexes possess immunosuppressive activity through
their ability to interact with another target, the abundant serine threonine
phosphatase calcineurin. Evaluating the immunosuppressive activities of
the FK-506 metabolites by comparing them with known immunosuppressive agents
via mixed lymphocyte reaction is of clinical importance because some metabolites
may retain the pharmacological activity of the parent drug or exhibit cytotoxic
effects. FK-506 is metabolized by the cytochrome P-450-dependent mixed-function
oxygenase system in different animal species, and we are reporting the
isolation from pig liver microsomes, and the identification by electrospray
ms-ms, of the FK-506 C19-C20 epoxide metabolite. We found that this new
metabolite exhibits reduced in vitro immunosuppressive activity compared
with FK-506 and has approximately the same immunosuppressive potency as
other known immunosuppressive drugs, such as cyclosporin A and IMM-125,
a hydroxyethyl derivative of D-serine cyclosporin A. We were able to demonstrate
that after incubation of the FK-506 metabolite in human mixed lymphocyte
reaction cultures for 6 days, the compound was stable under the conditions
used for cell culture as evidenced by electrospray-ms data. A weak direct
cytotoxic effect (< 30% cell death) was observed only at the highest
concentrations (2500 and 5000 ng/ml), which shows that the mixed lymphocyte
reaction inhibition cannot be due to a toxic effect.
PMID: 9495869, UI: 98173750