Disclosed herein is a wearable drug delivery device including a container filled at least partially with a drug including at least one of a PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) specific antibody, a granulocyte colony-stimulating factor (G-CSF), a sclerostin antibody, or a calcitonin gene-related peptide (CGRP) antibody. The wearable drug delivery device may include a needle and an insertion mechanism configured to insert the needle into a patient. A fluid pathway connector may define a sterile fluid flowpath between the container and the insertion mechanism. Optionally, a cannula initially disposed about the needle may be included. The cannula may be retained in the patient at an injection site created by the needle after the needle is withdrawn from the patient. Methods of assembly and operation are also provided.