Pharmacodynamics of a single low dose of long-acting recombinant follicle-stimulating hormone (FSH-carboxy terminal peptide, corifollitropin alfa) in women with World Health Organization group II anovulatory infertility

In a double-blind, placebo-controlled, randomized study, 55 anovulatory subjects received a single sc injection of placebo (n = 10) or recombinant long-acting FSH [FSH-carboxy terminal peptide (CTP), ORG 36286, corifollitropin alfa; NV Organon, The Netherlands] in doses of 7.5 (n = 13), 15 (n = 10), 30 (n = 11), or 60 mug (n = 11). The injection was given 2 or 3 d after the onset of a spontaneous or progestagen-induced withdrawal bleed. After drug administration, the induced follicular response varied widely among subjects in each dose group. The percentage of subjects with a follicular response (at least one follicle greater than or equal to 10.0 mm) increased with the dose (P < 0.01) and was 10, 31, 70, 73, and 82% in the placebo and 7.5-, 15-, 30-, and 60-mu g treatment groups, respectively. In responding subjects, the average maximum number of follicles was 4.0, 7.6, 13.4, and 20.0, respectively, which was reached at 6.5, 6.9, 6.6, and 8.2 d after a single dose of 7.5, 15, 30, and 60 mu g FSH-CTP, respectively. The dose-response for the number of follicles was statistically significant within the dose range tested (P < 0.01). Peak serum inhibin-B levels were significantly correlated with serum estradiol (E-2) levels (r = 0.84, P < 0.01), and number of follicles observed at the same time point (for both hormones; r = 0.47, P < 0.01). Overall per treatment group, serum E-2 and inhibin B concentrations significantly increased only in the two highest FSH-CTP dose groups, reaching peak concentrations at d 3 in the 30-mug group and at d 5 in the 60-mug group. Thereafter these hormone values declined rapidly, returning to baseline within 1 wk after FSH-CTP administration. In total, nine of the 55 treated subjects (16.4%) ovulated after drug administration: one subject in the placebo group, two subjects in the 7.5-mug group, three subjects in the 15-mug group, two in the 30-mug group, and one in the 60-mug group. Three subjects had monofollicular ovulation after placebo (n = 1) and a single dose of 15 mug FSH-CTP (n = 2). In two subjects with too many preovulatory follicles, ( multiple) ovulation was prevented by GnRH antagonist administration. Thus, a single low dose of long-acting FSH-CTP was able to induce one or more follicles to grow up to ovulatory sizes, but the anovulatory status was not reversed because the incidence of subsequent (mono)ovulations was low.