Son of Titus Labienus, was to sent to Parthia (Modern Day Iraq/Iran) by Cassius in winter 43/2 BCE to solicit help against the triumvirs. Philippi marooned him in Parthia, but in winter 41/0 BCE he and the king’s son Pacorus led Parthian troops into Syria and defeated Antony’s governor L. Decidius Saxa; then, with Saxa’s army, which went over to him, Labienus overran part of Asia Minor. On his coins he calls himself ‘Q. Labienus Parthicus imp’, claiming victory over the Parthians and had forced them to become allies. In 39 BCE he was defeated and killed by P. Ventidus.
Hornblower et al, Oxford Classical Dictionay, 3rd edition, Oxford, 2003. p 809.