HE-PBX is used to denote missiles which use HE (High-Explosive) warheads and which also use polymers to bind the explosive material together (PBX = Polymer-Bonded eXplosives).
HE and PBX are two different classifications of a warhead. The first is a classification by the velocity of the shock wave, which distinguishes high explosive vs low explosive. The other one classifies missiles by the use form of the explosive, i.e. the way the explosive material is packed together in the warhead (here: bound by polymers).