ABSTRACT
Pharmacokinetics of the orally active, cyclic peptide complement factor C5a receptor antagonist, AcF-[OP(D-Cha)WR] (PMX53) were determined in the rat. Biliary excretion of the unchanged drug was a major route of elimination after intravenous administration, but not following oral administration. Portal and peripheral blood levels of PMX53 were determined after oral administration or direct injection into the ileum, colon or local administration into the rectum. PMX53 was rapidly absorbed from mucosal sites, with peak plasma levels occurring as early as 5 min post-administration. Early portal blood levels were consistently higher than peripheral levels following ileal, colonic and rectal administration, but not after oral dosing. The results suggest that hepatic elimination occurs rapidly with higher (>or= 100 ng/ml) peripheral blood levels of the drug. Combination of PMX53 with the excipient chitosan resulted in significantly higher peripheral levels of the drug following ileal and colonic application, but not with buccal or oral administration. Buccal administration resulted in a similar plasma pharmacokinetic profile to oral administration. These results suggest that PMX53 is rapidly absorbed across mucosal membranes in the rat, and that administration using excipients such as chitosan may offer a method of increasing bioavailability.
Subject(s)
Complement C5a/antagonists & inhibitors , Peptides, Cyclic/administration & dosage , Peptides, Cyclic/pharmacokinetics , Administration, Oral , Animals , Bile/metabolism , Drug Carriers/chemistry , Female , Injections, Intravenous , Peptides, Cyclic/blood , Peptides, Cyclic/pharmacology , Rats , Rats, WistarABSTRACT
We have previously shown that complement factor 5a (C5a) plays a role in the pathogenesis of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats by using the selective, orally active C5a antagonist AcF-[OP(d-Cha)WR]. This study tested the efficacy and potency of a new C5a antagonist, hydrocinnamate (HC)-[OP(d-Cha)WR], which has limited intestinal lumenal metabolism, in this model of colitis. Analogs of AcF-[OP(d-Cha)WR] were examined for their susceptibility to alimentary metabolism in the rat using intestinal mucosal washings. One metabolically stable analog, HC-[OP(d-Cha)WR], was then evaluated pharmacokinetically and investigated at a range of doses (0.03-10 mg/kg/day p.o.) in the 8-day rat TNBS-colitis model, against the comparator drug AcF-[OP(d-Cha)WR]. Using various amino acid substitutions, it was determined that the AcF moiety of AcF-[OP(d-Cha)WR] was responsible for the metabolic instability of the compound in intestinal mucosal washings. The analog HC-[OP(d-Cha)WR], equiactive in vitro to AcF-[OP(d-Cha)WR], was resistant to intestinal metabolism, but it displayed similar oral bioavailability to AcF-[OP(d-Cha)WR]. However, in the rat TNBS-colitis model, HC-[OP(d-Cha)WR] was effective at reducing mortality, colon edema, colon macroscopic scores, and increasing food consumption and body weights, at 10- to 30-fold lower oral doses than AcF-[OP(d-Cha)WR]. These studies suggest that resistance to intestinal metabolism by HC-[OP(d-Cha)WR] may result in increased local concentrations of the drug in the colon, thus affording efficacy with markedly lower oral doses than AcF-[OP(d-Cha)WR] against TNBS-colitis. This large increase in potency and high efficacy of this compound makes it a potential candidate for clinical development against intestinal diseases such as inflammatory bowel disease.
Subject(s)
Complement C5a/metabolism , Inflammatory Bowel Diseases/drug therapy , Peptides, Cyclic/therapeutic use , Receptors, Complement/antagonists & inhibitors , Animals , Biological Availability , Biotransformation , Digestive System/metabolism , Eating/drug effects , Edema/chemically induced , Edema/pathology , Edema/prevention & control , Female , Humans , Inflammatory Bowel Diseases/chemically induced , Inflammatory Bowel Diseases/pathology , Intestinal Mucosa/pathology , Peptides, Cyclic/pharmacokinetics , Peptides, Cyclic/pharmacology , Rats , Rats, Wistar , Trinitrobenzenesulfonic Acid , Ulcer/chemically induced , Ulcer/pathology , Ulcer/prevention & control , Weight LossABSTRACT
BACKGROUND/AIMS: Complement activation is induced by ischaemia-reperfusion (I/R) and the complement factor C5a plays an important role in organ specific I/R injuries. This study investigated the efficacy of a small molecule C5a receptor (C5aR) antagonist against hepatic I/R injury. METHODS: Total hepatic ischaemia or partial hepatic ischaemia were induced in rats, followed by a period of reperfusion. The C5aR antagonist, AcF-[OPdChaWR], was administered at 1 mg/kg i.v. or 10 mg/kg p.o. or s.c. before induction of ischaemia. Total hepatic I/R-induced mortality was measured and partial hepatic ischaemia injury was assessed by measuring the serum levels of liver enzymes, tissue or serum TNFalpha, liver and lung myeloperoxidase activity, the number of infiltrating neutrophils, neutrophilia and liver histopathology. RESULTS: C5aR antagonist treatment reduced total hepatic I/R-induced mortality. In partial hepatic I/R rats, treatment with the C5aR antagonist significantly attenuated the increases in liver enzymes, serum and tissue TNFalpha, myeloperoxidase activity, infiltrating neutrophils, neutrophilia, and also reduced liver histopathology. CONCLUSIONS: This study shows that an orally active, small molecule C5aR antagonist is effective in reducing the markers of tissue damage caused by I/R in the rat, suggesting an important role for C5a in I/R injuries in the liver.
