AS-101 is a tellurate compound originally designed as a drug with cyto
static activity. Nevertheless, in vivo it was found to be an immunomod
ulator agent due to a stimulation of cytokine production. Mitotic inde
x (MI) as an indicator of cytotoxicity and cell proliferation kinetics
(CPK) in lymphocytes cultures are parameters used in the evaluation o
f the antineoplastic activity of drugs, such as mitomycin-C and cispla
tin. For this reason, we evaluated the effects of AS-101 upon these tw
o parameters. The results show that AS-101 produces an inhibition of M
I in proliferating lymphocytes higher than the inhibition mediated by
cisplatin. When CPK was evaluated, AS-101 induced a retardation not re
lated with dose, while cisplatin produced a stepwise inhibition. This
effect contrasts with the stimulation observed when AS-101 was added t
o non-proliferating lymphocytes which was measured as an increased [H-
3]thymidine incorporation in culture. The results confirm the mode of
action of AS-101 as a real modulating agent of cell proliferation.