17β-Estradiol and natural progesterone for menopausal hormone therapy: REPLENISH phase 3 study design of a combination capsule and evidence review.

Several formulations combining estrogens and progestins for hormone therapy (HT) have been approved worldwide for the treatment of menopausal symptoms, yet recent data indicate a decline in their use and an increase in compounded bioidentical HT. Up to now, no single product combining natural 17β-estradiol and progesterone has been approved by the US Food and Drug Administration (FDA) or the European Medicines Agency (EMA). A phase 3 trial (REPLENISH) is underway to study a novel oral formulation of solubilized 17β-estradiol and natural progesterone combined in a single gelatin capsule (TX-001HR; TherapeuticsMD, Inc, Boca Raton, FL) for treating vasomotor symptoms (VMS) in postmenopausal women. The REPLENISH trial evaluates the efficacy and safety of TX-001HR (4 doses) versus placebo for the reduction of moderate to severe VMS frequency and severity at 4 and 12 weeks and evaluates the endometrial safety of the combinations at 1 year. TX-001HR contains hormones that are molecularly identical to endogenous estradiol and progesterone and is intended as an option for women who prefer bioidentical hormones; further, it does not contain peanut oil, a common allergen. The constituents of TX-001HR, in a pharmacokinetic report, showed similar bioavailability and safety compared with reference estradiol tablets and micronized progesterone capsules administered together. Published data suggest a safer profile of estradiol and natural progesterone compared with HT containing conjugated equine estrogens and progestins. This report summarizes the methodology of the REPLENISH trial and reviews the evidence suggesting clinical differences between HT containing progesterone or progestins, and estradiol or conjugated equine estrogens.