The data obtained after the first screening indicate that the nature of the anchored moiety (nucleobase or other type of small molecule), as well as that of the connector influence on a larger extent the antiparasitic activity compared to the toxicity on the host cells. 20 compounds fulfilled the selection criteria (compounds that when applied at 1 µM inhibited T. gondii-β-gal proliferation by at least 90% and did not impair HFF viability by more than 50%) and were submitted to dose-response studies to determine the T. gondii IC50 values and the cytotoxicity to host cells at 2.5 µM (the results are summarized in Table ).