Metabolic pathways of the contragestational agent, 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazole (DL 111-IT), in the rat

Embryotoxicity and teratogenicity of DL111-IT, an early pregnancy-terminating agent, in the subsequent gestation following administration in rats

DL 111-IT is a new non-hormonal early pregnancy-terminating agent. The subsequent embryotoxic and teratogenic effects of DL111-IT were studied in the rats whose first pregnancy had been terminated by the agent. The secondary pregnancy of the treated rats were allowed to initiate at 30-, 45-, and 90-day intervals, respectively, after the termination of the first pregnancy. The toxicities primed with DL111-IT, such as resorbed embryos and nephrohydrosis fetuses, were found to be 8.0% and 8.5%, respectively, in the rats with pregnancy at 30-day interval. This is significantly different from 4.0% resorbed embryos and 2.4% nephrohydrosis fetuses in vehicle control (P less than 0.05). However, the rate of resorbed embryos decreased to 7.0% or 6.0% in the rats with pregnancy at 45- or 90-day intervals, respectively. No other significant embryotoxicity and teratogenicity were observed in those rats initiating their pregnancy 45 days later after first-pregnancy termination by DL111-IT. Thus, DL111-IT appears to have very low subsequent toxicity in the course of rat pregnancy cycles.

On the mode of action of a new contragestational agent (DL 111-IT)

Non-hormonal compounds belonging to 3,5-diphenyl-1H,1,2,4 triazoles and chemically related classes (triazoles in short) are known to be endowed with high contragestational activity in rodents, dogs and primates. The data herein reported for one of the leaders of this family of compounds (DL 111-IT) along with those previously reported for some analogues, demonstrate that triazoles cause pregnancy arrest by a direct action on conception product. This action is expressed through a progressive slowing down of the conceptus development with a consequent onset of a state of anoxia, pregnancy arrest, degeneration of placentae and adnexae and their absorption or expulsion. The selective time of gestation during which they elicit the antifertility effect (early post-implantation period) and the histological examinations revealed that the target of their action are the ectoplacental and decidual cells. Biochemical studies on conceptus product demonstrate that, although they do not bind to progesterone receptors or inhibit ornithine decarboxylase activity, triazoles induce an early and marked increase in the number of cytosol progesterone receptors accompanied by a steep decrease in the ornithine decarboxylase activity in the product of conception. These findings are discussed in relation to the possibility that triazoles may trigger pregnancy arrest by interfering with the chain of events by which progesterone regulates the mitotic activity of decidual and trophoblastic cells.

Immunological profile of DL111-IT, a new immunosuppressant agent

The immunosuppressive properties of the non-hormonal contragestional agent 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazole (DL111-IT) were evaluated on different immunological functions. The compound displayed significant immunosuppressive activity on both humoral and cellular immunity when administered during the inductive phase of the immune response. In experimental models autoimmunity and skin transplantation, DL111-IT was able to reduce the production of auto-antibodies and prolong skin graft survival. The compound, even at doses much higher than those effective inhibiting immune responses, did not influence the survival time of some haematological tumors in mice. This suggest that DL111-IT does not act by a general cytotoxic mechanism.