The method set out herein involves conducting adaptive clinical trial to develop parenteral therapeutic product with variable dose drug delivery devices. The method comprises using a variable dose drug delivery device to respond modifications during the adaptive clinical trial, wherein the variable dose drug delivery device is able to deliver more than one dose level and is for delivering fluid formulation. Other methods set out herein involve using a variable dose drug delivery device equipped with radio frequency identification (RFID) or near field communication (NFC) technology to improve patient adherence to drug administration in the adaptive clinical trial.