Leflunonide-an lmmunomodulator-lnduces Regression of Endometrial Explants in a Rat

OBJECTIVE: To test if leflunomide, an immunomodulator, could impede the growth ofan ectopic uterine tissue. METHODS: Endometriosis was surgically induced in 26 rats by transplantinig an autologousfragment of endometrial tissue onto the inner surface (of the abdominal wall. Four weeks later two rats were killed. The volume and weight of the implants were measured. The remaining rats were randomly grouped, and in group I no medication was given. To the rats in group 2, 35 mg/kg/d of leflunomide was administered orally. Four weeks later, rats were killed and ectopic uterine tissues were reevaluated morphologically and histologically. A scoring system was used to evaluate preservation of epithelia. RESULTS: Two rats in the control group died 5 weeks dfter surgery. There was a significant difference in post-treatment spherical volumes (139.1 ± 92.8 versus 33.5 ± 12.5 mm3) and explant weighits (156.3 + 105.6 versus 38.6 ± 12.6mtg) between the control and leflunoomide-treatedgroups. 77Te epithelia were found to be preserved significantly better in the control group lvhen compared with the leflunomide-treated group (median 2.5 [interquartile range, 1.25] voersus medianz 1.00 [interquartile range, 1.5J). CONCLUSION: Leflunomide appeared to cause regression of experimental endometriosis in rats. (U Soc Gynecol Investig 2006;3:378- 83) Copyi(ght (©D 2006 by the Society for Gynecologic Investigation.