Thermoplastic compositions based on polybutylene terephthalate are provided which are useful in high temperature resistant wire coating applications. These compositions generally are four-component alloys containing a) 40-65 % by weight of poly (1,4-butylene terephthalate); b) 1-30 % by weight of a polymeric grafting agent which is an ethylene copolymer carrying reactive groups; c) 0-20 % by weight of an ethylene copolymer ionomer; d) at least one component selected from the group of a copolyester urethane, a copolyether ester, a hydrogenated styrene/diene block copolymer optionally grafted with maleic anhydride, an adduct of maleic anhydride and a copolymer of ethylene or an acrylic-modified elastomer-based polymer.