Comparison of antiviral properties in mice of bis-pyrrolidinoacetamido-fluorenone (MLU-B75), bis-dipropylaminoacetamido-fluorenone (MLU-B76), and tilorone hydrochloride.

Like tilorone . HCl, its analogues, bis-pyrrolidinoacetamido-fluorenone (MLU-B75), and bis-dipropylaminoacetamido-fluorenone (MLU-B76), significantly protected mice against intraperitoneal challenge with a lethal dose of Mengo virus when administered prophylactically in a single oral dose of 250 mg per kg body weight. At lower doses the antiviral activity of MLU-B75 and MLU-B76 decreased more rapidly than that of tilorone. HCl. At the dose of 250 mg per kg the degree of antiviral protection and the titre of interferon induced by tilorone. HCl correlated well, but there was no correlation between the extent of protection and the detected amount of virus inhibitor induced by MLU-B76. It remains to be determined whether the antiviral protection elicited by the analogues of tilorone is mediated by interferon.