The safety and tolerability as well as pharmacokinetics of a new selective antiprogestagen, Org 31710, were studied after oral administration of single doses of 10, 25, 50, or 75 mg to 24 healthy male volunteers. Per dose-group, five subjects received active and one subject received placebo treatment. In subjects receiving 75 mg, the effects of Org 31710 on serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone were also studied. No adverse or seriously adverse events were observed. All doses of Org 31710 were well tolerated. Characterization of the Org 31710 plasma pharmacokinetics revealed a statistically significant deviation from linearity: the dose normalized Cmax (nCmax) and dose normalized area under the curve (nAUC) values were significantly lower for the higher dosages (p < 0.05). Furthermore, tmax tended to decrease (from 1.6 to 0.9 h), whereas the elimination half-life (t1/2) tended to increase (from on average 45 to 57 h) with increasing dose. Org 31710 did not have any effect on serum levels of FSH, LH, and testosterone. In conclusion, Org 31710 appears to be a safe and well-tolerated compound in the dosage range studied.
PIP: The pharmacokinetics, safety, and tolerability of a new selective antiprogestagen--Org 31710--were investigated in 24 healthy Dutch men. Single oral doses of 10, 25, 50, or 75 mg were administered. In each dose group, 5 subjects received Org 31710 and 1 was given placebo. All dosages were well tolerated and no clinically relevant adverse events were recorded. Plasma pharmacokinetic characterizations revealed a statistically significant deviation from linearity after single doses of 10-75 mg of Org 31710. The dose-normalized maximum plasma concentrations was significantly higher in the 10 mg group and significantly lower in the 75 mg group compared with the 25 mg and 50 mg groups. Mean values of the normalized area under the plasma concentration time curve at 10 and 25 mg were significantly higher than values at higher dosages. The time to reach maximum plasma concentration decreased from 1.6 to 0.9 hours with increasing Org 31710 dose, while the elimination half-life increased from 45 to 57 hours. Serum levels of follicle-stimulating hormone, luteinizing hormone, and testosterone were not affected by a single dose of 75 mg of Org 31710. These findings demonstrate the safety and tolerability of the novel antiprogestagen Org 31710. The low antiglucocorticoid activity of Org 31710 represents a potential advantage over RU 486.