Details for Patent: 5,318,899

Title:	Platelet aggregation inhibitors
Abstract:	An assay for screening snake venom for the presence or absence of platelet aggregation inhibitors (PAIs) based on specific receptor binding is described. Using this assay, the identification and characterization of PAIs in a wide range of snake venom samples was accomplished. The isolated and purified PAI from several of these active snake venoms is described and characterized. In addition, PAIs lacking the Arg-Gly-Asp (RGD) adhesion sequence but containing K.sup.* -(G/Sar)-D wherein K.sup.* is a modified lysyl residue of the formula wherein each R.sup.1 is independently H, alkyl(1-6C) or at most one R.sup.1 is R.sup.2 --C.dbd.NR.sup.3 wherein R.sup.2 is H, alkyl(1-6C) or is NR.sup.4.sub.2 in which each R.sup.4 is independently H or alkyl(1-6C) and R.sup.3 is H, alkyl(1-6C), phenyl or benzyl, or R.sup.2 --C=NR.sup.3 is a radical selected from the group consisting of: ##STR1## where m is an integer of 2-3, and each R.sup.5 is independently H or alkyl(1-6C); and wherein one or two (CH.sub.2) may be replaced by O or S provided said O or S is not adjacent to another heteroatom are prepared and shown to specifically inhibit the binding of fibrinogen or von Willebrand Factor to GP IIb-IIIa.
Inventor(s):	Scarborough; Robert M. (Belmont, CA), Wolf; David L. (Palo Alto, CA), Charo; Israel F. (Lafayette, CA)
Assignee:	COR Therapeutics, Inc. (South San Francisco, CA)
Filing Date:	Feb 20, 1990
Application Number:	07/483,229
Claims:	1. A DNA in isolated and purified form which encodes a platelet aggregation inhibitor (PAI) capable of inhibiting binding of fibrinogen (Fg) or von Willebrand factor (vWF) to platelet membrane glycoprotein (GP) IIb-IIIa with substantially more potency than of inhibiting binding of vitronectin to vitronectin receptor of fibronectin to fibronectin receptor, which PAI has the primary structure of a naturally occurring platelet aggregation inhibitor, wherein said naturally occurring PAI contains the amino acid sequence RGD, and wherein said PAI is modified by substituting for said RGD the sequence KGD. 2. A recombinant expression system capable, when transformed into a compatible host, of expressing a DNA encoding a specific platelet aggregation inhibitor (PAI) capable of inhibiting binding of fibrinogen (Fg) or von Willebrand factor (vWF) to platelet membrane glycoprotein (GP) IIb-IIIa with substantially more potency than of inhibiting binding of vitronectin to vitronectin receptor or fibronectin to fibronectin receptor, which PAI has the primary structure of a naturally occurring platelet aggregation inhibitor, wherein said naturally occurring PAI contains the amino acid sequence RGD, and wherein said PAI is modified by substituting for said RGD the sequence KGD, which expression system comprises said encoding DNA operably linked to control sequences compatible with said host. 3. A recombinant host transformed with the expression system of claim 2. 4. A method to produce a platelet membrane glycoprotein (GP) IIb-IIIa specific platelet aggregation inhibitor (PAI) wherein said PAI has the primary structure of a naturally occurring platelet aggregation inhibitor, wherein said naturally occurring PAI contains the amino acid sequence RGDE, and wherein said PAI is modified by substituting for said RGD the sequence KGD, which method comprises culturing the host of claim 3 under conditions effective to express the PAI-encoding DNA to produce PAI; and recovering the PAI from the culture. 5. The DNA of claim 1 wherein said naturally occurring PAI is selected from the group consisting of trigramin, echistatin, elegantin, albolabrin, lachesin, flavoviridin, eristicophin, tergeminin, rhodastomin, applaggin, halysin, bitistatin, ruberin, cerastin, cotiarin, crotatroxin, horridin, basilicin, lutosin, molossin, and viridin. 6. The recombinant expression system of claim 2 wherein said naturally occurring PAI is selected from the group consisting of trigramin, echistatin, elegantin, albolabrin, lachesin, flavoviridin, eristicophin, tergeminin, rhodastomin, applaggin, halysin, bitistatin, ruberin, cerastin, cotiarin, crotatroxin, horridin, basilicin, lutosin, molossin, and viridin. 7. The host of claim 3 wherein said naturally occurring PAI is selected from the group consisting of trigramin, echistatin, elegantin, albolabrin, lachesin, flavoviridin, eristicophin, tergeminin, rhodastomin, applaggin, halysin, bitistatin, ruberin, cerastin, cotiarin, crotatroxin, horridin, basilicin, lutosin, molossin, and viridin. 8. The method of claim 4 wherein said naturally occurring PAI is selected from the group consisting of trigramin, echistatin, elegantin, albolabrin, lachesin, flavoviridin, eristicophin, tergeminin, rhodastomin, applaggin, halysin, bitistatin, ruberin, cerastin, cotiarin, crotatroxin, horridin, basilicin, lutosin, molossin, and viridin.