The iron chelator N,N',N' '-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (tachpyr) was recently reported to display potent antitumor activity. The present study was focused on identifying an adequate bifunctional version of tachpyr as a lead compound for use in antibody-targeted iron depletion tumor therapy. Preparation of tachpyr derivatives having a side chain is reported, and their cytotoxic activity is evaluated in the HeLa cell line. The observed cytotoxity appears dependent on the functionalization site of the tachpyr employed for introducing the protein conjugation. Tachpyr derivatives 14 and 15 having a side chain introduced into the 5-position of the pyridyl ring display more potent cytotoxicity than tachpyr derivatives 7 and 8 having a side chain introduced onto one of the secondary amines. BOC-protected tachpyr derivative 14 exhibited the most potent cytotoxicity against this cancer cell line, which was reasonably comparable to the parent tachpyr. Tachpyr derivative 14 was further converted into bifunctional tachpyr 17 possessing a maleimide linker for conjugation with thiolated monoclonal antibodies (mAbs).