A 90-day subcutaneous toxicity and fertility study of a LHRH antagonist in rats.

[Ac-D2Nal1,4Cl-DPhe2,D3Pal3,Arg5,DGlu6+ ++ (anisole adduct),DAla10]-GnRH (Nal-Glu) is an antagonist of LHRH and has the potential to be utilized as an antigonadal agent. A study was undertaken to evaluate the toxicological effects of Nal-Glu in rats. Nal-Glu, dissolved in 5% mannitol in water containing 9 ml/liter benzyl alcohol, was administered subcutaneously. In subchronic studies, groups of 12 male and 12 female rats received 0, 50, 250, or 1250 micrograms/kg body weight (BW) Nal-Glu for 90 days and were killed on Day 91. Additional groups of male and female rats were given the high dose of Nal-Glu (1250 micrograms/kg BW) or vehicle for either 30 or 90 days. Their fertility was assessed by mating them with normal animals. Unlike some other LHRH antagonists, Nal-Glu exhibited a low potency for causing in vitro histamine release from rat peritoneal mast cells. Furthermore, in acute in vivo studies, Nal-Glu was less active in the induction of peripheral edema. In the subchronic study, all doses of Nal-Glu were well tolerated and there were no apparent systemic toxic effects. The pharmacological effects of Nal-Glu were quite evident, however. Nal-Glu treatment led to a significantly decreased body weight gain in the males and a significantly increased body weight gain in the females. There was a dose-dependent decrease in weights of gonads and reproductive organs in both the sexes. Some of the hematological and serological parameters were significantly different in Nal-Glu-treated animals. However, most of the values were within the normal range and are considered to be of no toxicological significance. Histopathological evaluations were made in the control and high-dose groups only. In the male, a seminiferous tubular degeneration and atrophy of the interstitial cells was seen. The prostate and seminal vesicles were also atrophied and the epididymides were devoid of spermatozoa. In the females, the ovaries and uteri were atrophic. The injection site of Nal-Glu-treated rats had inflammatory changes indicative of a local irritating action of the drug. All other tissues had normal histomorphology. Both male and female rats became infertile when 1250 micrograms/kg Nal-Glu was administered for 30 days. Normal fertility was restored 8 weeks after cessation of 90-day treatment. It is concluded that repeated administration of Nal-Glu leads to reversible infertility in both male and female rats. Although it was irritating at the site of injection. Nal-Glu had no systemic toxicological effects.

Effect of sulfasalazine and its analogs on fertility in male rats.

Several derivatives of sulfasalazine were tested for their antifertility activity in male rats. The compounds were administered to groups of rats daily by oral gavage for 28 days. Fertility of the rats treated with sulfasalazine or compound CH 74A was reduced, while other compounds had no effect. In a subsequent experiment, therefore, only the active compounds were studied further. Fertility of rats treated with sulfasalazine, compound CH 74A, CH 99A or sulfapyridine was reduced during 40 days of treatment. At the end of treatment, body weights were reduced in higher dose groups of sulfasalazine, CH 74A and sulfapyridine compared to control animals. The weights of the testes, prostate or seminal vesicle were not altered by any of the treatments. On the other hand, weight of the epididymides decreased in all higher dose groups except in CH 99A-treated animals. Sperm motility decreased in all the treated rats except in animals treated with low dose of sulfapyridine, whereas epididymal sperm count decreased in all but CH 99A-treated animals. These results suggest that sulfasalazine and its derivatives bring about their antifertility effects by decreasing sperm motility and/or number of spermatozoa.

Reversal of testicular function after prolonged suppression with an LHRH agonist in rhesus monkeys.

Using subcutaneously implanted osmotic pumps, four male rhesus monkeys were continuously infused for 18 months with 100 micrograms/day of [(imBzl)-D-His6-Pro9-NEt]-LHRH (LHRH-A), a potent agonist of LHRH. After an initial increase, serum testosterone levels declined to 10% of pretreatment levels in three monkeys and the response to electroejaculation was lost. There was a decrease in testicular volume. Androgen replacement in the form of subcutaneous SILASTIC implants releasing 7 alpha-methyl-19-nor-testosterone acetate led to a restoration of ejaculatory response and the electroejaculates were devoid of spermatozoa. Under this treatment regimen (100 micrograms LHRH-A + 100 micrograms androgen daily), azoospermia was essentially maintained in the three monkeys for about 8 months. Withdrawal of LHRH-A and androgen treatment led to a complete restoration of testicular function. Serum testosterone returned to control levels and spermatozoa reappeared in the ejaculates with sperm counts reaching the normal range. Testicular volumes showed a gradual increase. These results indicate that continuous administration of an LHRH agonist together with an androgen can induce an extended period of azoospermia in rhesus monkeys. These results also show that after prolonged suppression (more than one year) of testicular function complete recovery occurs after cessation of treatment.