title: An orally active reversible inhibitor of cathepsin S inhibits human trans vivo delayed-type hypersensitivity.
abstract: Cathepsin S is a major histocompatibility complex (MHC) class II associated invariant chain (Ii) degrading enzyme expressed in antigen presenting cells such as B cells and dendritic cells. This enzyme is essential for MHC class II associated antigen processing and presentation to CD4(+) T cells. Compound I, a selective, reversible and orally bioavailable, inhibitor of cathepsin S, with molecular IC(50)=9 nM, has been recently described. We have tested the effects of compound I in a trans vivo model of delayed-type hypersensitivity. Human peripheral blood mononuclear cells (7-10 x 10(6)) from tetanus-sensitized donors were co-injected with tetanus toxoid (0.25 Lf) into C57Bl/6 mouse footpads. At 24 h, significant footpad swelling (+0.024+/-0.001 cm) characterized by an influx of mouse neutrophils and monocytes was observed. Injection of peripheral blood mononuclear cells alone caused negligible swelling (0.002+/-0.0002 cm). Anti-human MHC class II (HLA-DR, DP, DQ) antibody (5 mg/kg, i.p.) inhibited the swelling 91+/-7%, thus demonstrating a role of human antigen presenting cells in this model. Compound I (10, 30, and 100 mg/kg, p.o.) inhibited the response with an ED50 of approximately 18 mg/kg. Compound III, a less active analogue (molecular IC50>20 microM) had no effect. Furthermore, pretreatment of peripheral blood mononuclear cells with 10 nM compound II, an irreversible inhibitor (molecular IC50=11 nM) inhibited swelling 87+/-4%. These findings support the role of cathepsin S in human delayed-type hypersensitivity. Inhibition of cathepsin S with compound I may be useful in the treatment of human autoimmune diseases like rheumatoid arthritis and multiple sclerosis.
authors.affiliation: Department of Immunology and Inflammation, Boehringer Ingelheim Pharmaceutical Inc., 900 Ridgebury Road, Box 368, Ridgefield, CT 06877-0368, USA. sdesai@rdg.boehringer-ingelheim.com
authors.forename: Sudha N
authors.initials: SN
authors.lastname: Desai
authors.forename: Della M
authors.initials: DM
authors.lastname: White
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: O'shea
authors.forename: Maryanne L
authors.initials: ML
authors.lastname: Brown
authors.forename: Charles L
authors.initials: CL
authors.lastname: Cywin
authors.forename: Denice M
authors.initials: DM
authors.lastname: Spero
authors.forename: Maret J
authors.initials: MJ
authors.lastname: Panzenbeck
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D006968:Hypersensitivity, Delayed / Q000276:immunology / Q000473:pathology / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015394:Molecular Structure; D013329:Structure-Activity Relationship
chemical_list: D004791:Enzyme Inhibitors; D002403:Cathepsins; C028217:cathepsin S