Liquid drug transfer device for use in a Ready-To-Use liquid drug transfer assemblage for establishing flow communication between a liquid source and an injection vial. The liquid drug transfer device includes an injection vial adapter for mounting on an intact injection vial having an injection vial stopper without puncturing same, a liquid source adapter for attachment to a liquid source, a dual ended liquid transfer member for flow communication with the liquid source and puncturing an injection vial stopper, a safety catch mechanism requiring an initial manual linear sliding extension for priming the liquid drug transfer device, an extension limit arrangement for limiting the linear sliding extension, and a snap fit securing arrangement for securing the liquid source adapter on the injection vial adapter after actuation.
