Pantarhei is developing estetrol (E4) for oncological and veterinary applications, including breast and prostate cancer. High Dose Estetrol (HDE4) for breast cancer and prostate cancer treatment has successfully achieved proof-of-concept in human. Phase II clinical studies have demonstrated promising anti-tumor activity and major improvement of quality of life in patients with advanced breast and advanced prostate cancer (dual efficacy). Based on a positive outcome of the FDA Pre-IND meeting, the project is ready for Phase III development for the prostate cancer indication. For more information on these projects, see Estetrol for breast cancer and Estetrol for prostate cancer.
Pantarhei is potentially interested in (pharmaceutical) partners for the further oncological development of E4. The breast cancer project is ready for Phase IIB and prostate cancer for Phase III development. The breast cancer and prostate cancer indications are patent protected until 2037 respectively and 2038.
Estetrol (E4) is an estrogen, produced by the human fetal liver during pregnancy. It is present in high concentrations in the blood of pregnant women and at even higher levels in fetal blood (10-20 times) at parturition. This high exposure of the vulnerable developing fetus implies that E4 might be a safe estrogenic steroid for human use. Estetrol was identified by Egon Diczfalusy at the Karolinska Institute in Stockholm in 1965. It has been discovered as a potential new drug for human use by Herjan Coelingh Bennink at Pantarhei Bioscience (PRB) in 2000. Since then PRB has performed pre-clinical and clinical Phase I/II development of E4 for Women’s Health applications such as contraception and menopausal hormone therapy and Reproductive Endocrine Oncology (REO).
In 2015 Pantarhei sold all rights, assets, and patents of E4 to the Belgian company Mithra Pharmaceuticals. All rights for the oncological and veterinary E4 applications (including breast cancer and prostate cancer) were exclusively licensed back to Pantarhei and product development was continued by Pantarhei Oncology. Mithra is developing the Women’s Health applications of E4 (i.e. hormonal contraception [Estelle®] and menopausal hormone therapy [Donesta®]). Due to the many years of experience from the utilization of E4 in Women’s health applications, E4 has a well-established safety profile. During the first half year of 2021 approval was obtained for the new oral contraceptive Estelle® and the pill was launched in US, Canada and Europe the same year. For the indication menopausal hormone therapy, Phase III development is currently ongoing. The first positive top-line results from Donesta® Phase III studies were announced by Mithra in January 2022.