Nomegestrol acetate and vascular reactivity: nonhuman primate experiments

Area of Science:

• Cardiovascular Pharmacology
• Endocrinology
• Hormone Replacement Therapy

Background:

• Estrogen replacement therapy (ERT) offers cardiovascular benefits but poses endometrial hyperplasia risks.
• Combined hormone replacement therapy (HRT) uses progestins to mitigate endometrial cancer risk.
• Ensuring progestins do not negate estrogen's vascular benefits is crucial for HRT safety.

Purpose of the Study:

• To evaluate the vascular effects of nomegestrol acetate (NOMAC) in primate models of coronary artery disease.
• To determine if NOMAC negates the cardiovascular benefits of estrogen in hormone replacement therapy.

Main Methods:

• Two primate models were used: coronary vasoconstriction after diet and pharmacologically evoked coronary vasospasm.
• Ovariectomized Cynomolgus and Rhesus monkeys received estrogen (E2) with or without NOMAC or medroxyprogesterone acetate (MPA).
• Vascular reactivity was assessed via acetylcholine infusion and challenge protocols with serotonin and U46619.

Main Results:

• NOMAC did not counteract estrogen's prevention of paradoxical vasoconstriction to acetylcholine.
• In vasospasm models, NOMAC-treated monkeys showed no vasospasm, unlike MPA-treated monkeys.
• NOMAC demonstrated effective progestative activity, ensuring endometrial protection.

Conclusions:

• Nomegestrol acetate (NOMAC) preserves the vascular benefits of estrogen in hormone replacement therapy.
• NOMAC is a safe progestin for HRT, showing no adverse vascular effects unlike medroxyprogesterone acetate (MPA).
• NOMAC offers a balanced approach to HRT, addressing both cardiovascular and endometrial safety concerns.