Characterization of alpha(4)beta(1) (CD49d/CD29) on equine leukocytes: potential utility of a potent alpha(4)beta(1) (CD49d/CD29) receptor antagonist in the treatment of equine heaves (recurrent airway obstruction).
The purpose of this study was to characterize the alpha(4)beta(1) receptor (CD49d/CD29, very late antigen-4, VLA-4) on circulating equine leukocytes and to evaluate the intrinsic potency of an alpha(4)beta(1) receptor antagonist (Compound B) in the horse. Ultimately, these studies would allow us to determine the suitability of treating recurrent airway obstruction (RAO; heaves) affected horses by blocking the cellular recruitment of lymphocytes and neutrophils into the lung. The data demonstrates the alpha(4)beta(1) integrin is present on horse lymphocytes and neutrophils (fluorescence-assisted cell sorter, FACS) and can bind low molecular weight alpha(4)beta(1) antagonists (Compounds A and B) with high affinity. K(D) values for the binding of Compound A to non-activated alpha(4)beta(1) on isolated horse PBMCs (peripheral blood mononuclear cells) and activated neutrophils were 17 pM and 27 pM, respectively. Compound B was identified as a suitable antagonist for performing a series of in vivo experiments. Compound B was found to possess excellent potency in horse whole blood, possessing IC(50) and IC(90) values of 39 pM and 172 pM, respectively. This represents a 3.9-fold molar excess of drug over the alpha(4)beta(1) concentration in blood. Following oral administration of Compound B (5 mg/kg) to beagle dogs and rhesus monkeys, rapid and sustained alpha(4)beta(1) receptor occupancy (>80%) was achieved and maintained for a period of 24 h. When Compound B was administered intravenously to the horse, by either a slow or rapid infusion at a dose of 0.3 mg/kg, receptor blockade of >80% was observed out to 24 h with a concomitant leukocytosis. We believe that Compound B possesses suitable intrinsic and pharmacological properties to be evaluated clinically in horses affected by RAO.
Treonze
Kelly M
KM
Department of Immunology, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA. kelly_treonze@merck.com
Alves
Kenneth
K
Fischer
Paul
P
Hagmann
William K
WK
Hora
Donald
D
Kulick
Alison
A
Vakerich
Ken
K
Smith
Nicholas D
ND
Lingham
Russell B
RB
Maniar
Salony
S
Reger
Thomas S
TS
Zunic
Jasmine
J
Munoz
Benito
B
Prasit
Peppi
P
Nicholson
Donald
D
Si
Qian
Q
Judd
Keith
K
Nicolich
Susan
S
Kellerhouse
Patricia
P
Thompson
Donald
D
Mumford
Richard A
RA
D000402:Airway Obstruction / Q000097:blood / Q000188:drug therapy / Q000276:immunology / Q000662:veterinary*; D000818:Animals; D001667:Binding, Competitive; D004285:Dogs; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006734:Horse Diseases / Q000097:blood / Q000188:drug therapy / Q000276:immunology*; D006736:Horses; D039041:Integrin alpha4beta1 / Q000037:antagonists & inhibitors / Q000276:immunology*; D007962:Leukocytes / Q000276:immunology*; D008253:Macaca mulatta; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D039041:Integrin alpha4beta1