Ovarest is an oral treatment for endometriosis being developed by Enteris BioPharma. It contains leuprolide, a synthetic form of gonadotropin-releasing hormone (GnRH.)

How Ovarest works

Endometriosis is a condition in which the endometrium or the tissue lining the uterus grows outside the uterus. In women with the disease, this tissue is most commonly found in the ovaries, fallopian tubes and other tissues in the pelvic area.

The displaced endometrium continues to respond to hormonal changes of the menstrual cycle: thickening, breaking down and bleeding. However, because it is situated outside the uterus, it cannot exit the body via the menstrual flow and is trapped, which leads to inflammation and pain.

Ovarest disrupts the hormonal cycle associated with menstruation. This cycle begins with GnRH, which is normally released in pulses from an area of the brain called the hypothalamus. GnRH binds to its receptors in the pituitary gland and stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones, in turn, cause the egg follicle to develop in the ovary, as well as ovulation and the release of estrogen and progesterone.

Ovarest disrupts this pattern of GnRH pulses, which desensitizes the pituitary gland’s GnRH receptors. This reduces production of FSH and LH. As a result, less estrogen being released. This prevents menstruation and shrinks endometrial tissue, which reduces pain and inflammation in women with endometriosis.

An injectable form of leuprolide — the active ingredient leuprolide found in Ovarest — has been in use since the 1980s under various trade names, including Lupron. Ovarest is notable because it can be taken orally as a tablet. Leuprolide is a protein and therefore must be injected, because proteins are typically broken down in the digestive tract or have difficulty being absorbed into the bloodstream.

Enteris used its delivery technology, Peptelligence, to package the leuprolide so that it can still be effective when taken as a daily oral tablet. This method taking the medication is more convenient for patients than injecting leuprolide, usually once a month.

Ovarest in clinical trials

Ovarest is currently being investigated in Phase 2a clinical trial (NCT02807363) in healthy volunteers with promising results. That trial aims to enroll 32 women with endometriosis and is still recruiting participants in Canada. It will evaluate the pharmacokinetics and pharmacodynamics of two different doses of Ovarest administered over 28 days. These will be compared to Lupron.

Enteris plans a Phase 2b trial later in 2018 with the hope it will llay the foundations of a Phase 3 trial, which would examine the efficacy and safety of Ovarest in many women. The company will also determine whether Ovarest may be an effective treatment for other conditions such as uterine fibroid tumors and prostate cancer.

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