Abstract: Disclosed herein are novel methods and compositions for targeting drug delivery systems to specific cells. One aspect relates to a drug delivery system comprising an elastin-like peptide (ELP) component and a ligand selected from the group consisting of mIgA and knob capable of either drug encapsulation or drug attachment. Further aspects relate to drug delivery systems comprising an elastin-like peptide (ELP) component and a ligand; wherein the ligand specifically binds to a receptor selected from the group consisting of CAR and pIgR. Further aspects include the novel transcytosing properties of the elastin-like peptide and the ligand, knob. Also provided are methods and pharmaceutical compositions comprising the disclosed therapeutics.