The present invention provides indole compounds of Formula (I) or (II): or a stereoisomer, tautomer, pharmaceutically acceptable salt or solvate form thereof, wherein the variables ring A, X.sub.1, X.sub.2, X.sub.3, X.sub.4, R.sup.6, and R.sup.15 are as defined herein. These compounds are selective inhibitors of the human P2Y.sub.1 receptor which can be used as medicaments.