Complex sentence: Decernotinib also had the name VX-509 in development phase, a novel, potent, with high selectivity for JAK3, which demonstrates good efficacy in vivo in the rat host versus graft model (HvG).
Split into simpler sentences: Decernotinib also had the name VX-509 in development phase. It is an experimental drug with high selectivity for JAK3, which demonstrates good efficacy "in vivo" in the rat host versus graft model (HvG).