Estrogen plays a role in the activation of systemic lupus erythematosus (SLE) and in upregulating intracellular signals by binding to the estrogen receptor(s). Fulvestrant (Faslodex, AstraZeneca Pharmaceuticals, Wilmington, DE, USA), an estrogen selective receptor downregulator, competes for receptor binding in vitro and inhibits estrogen action in target cells. We evaluated the efficacy, side effects, and expression of T cell activation markers, following the administration of fulvestrant or placebo to premenopausal patients with SLE.
Twenty women with moderate SLE Disease Activity Index (SLEDAI; 7.87 +/- 3.7) were enrolled. They were premenopausal with regular menstrual cycles and not taking exogenous hormones. The study was double-blind and placebo-controlled. Ten patients received 250 mg fulvestrant intramuscularly for 12 months, and 10 received the placebo. All were observed monthly and 3 months after final fulvestrant/placebo injection. Measures studied were monthly SLEDAI scores, routine and serologic markers for lupus, and serum concentrations of estrogen and fulvestrant. Expression of T cell calcineurin and CD154 mRNA in peripheral T cells was measured by polymerase chain reaction. Medications the patients were taking were recorded each visit. Bone density was obtained at baseline and at visit 12.
Sixteen patients completed the 15-month study, 8 from each group. SLEDAI improved significantly in the fulvestrant group at both 12 months (p = 0.02) and 15 months (p = 0.002), but serologic markers, routine laboratory tests, and bone density did not. Serum estrogen levels were higher in the fulvestrant group and dropped when fulvestrant was discontinued; these differences were not statistically significant. Medications for therapy of lupus to the fulvestrant group were reduced, whereas the placebo group medications were unchanged or increased. Comparison of relative values at individual timepoints revealed significantly lower median values for the T cell activation markers CD154 (p < 0.001) and calcineurin (p = 0.013) in the fulvestrant arm.
Blocking estrogen receptors in vivo by an estrogen selective receptor downregulator could be considered as a new and relatively safe therapeutic approach in the management of SLE patients with moderately active disease for the 1-year study period.