The present invention relates to antibody-polypeptide-cytotoxin conjugates and methods of making, packaging, and using the conjugates. The polypeptide can be a Kunitz-type protease inhibitor or a derivative thereof that facilitates transport of the conjugate across the blood-brain barrier and/or into cancer cells outside the CNS, and the antibody moiety selectively binds a target within the CNS or in peripheral tumors to direct the cytotoxic agent to that target (e.g., a tumor or cancer cell). The conjugates can be further defined by the inclusion of a linker between the antibody moiety and the polypeptide by the number of polypeptides and cytotoxic agents conjugated thereto by the positions at which the entities within the conjugates are bound to one another and by the larger configuration of the conjugate. Modified polypeptides (e.g., polypeptides conjugated to cytotoxic agents but not to an anti-body moiety), pharmaceutical compositions, kits (e.g., including a modified polypeptide and an as-yet unconjugated antibody), and methods of making and using the conjugates are also features of the invention.
