Pantarhei Bioscience Study Findings Demonstrate the Disappearance of Breast Tumours During Treatment With the Human Fetal Estrogen Estetrol

Published: Jun 06, 2012

Wednesday, 6 June 2012: Netherlands: Pantarhei Bioscience (PRB), a specialty pharmaceutical company focusing on the development of innovative, proprietary treatments in the fields of women’s health and endocrine cancer, announces the publication of study results of the human fetal estrogen Estetrol (E4) in prevention and suppression of tumor growth in an in vivo mammary tumour model. The findings have been published in the Journal of Hormone Molecular Biology and Clinical Investigation (2012; 9(1): 95-103).

Pantarhei Bioscience is developing E4 for several Women’s Health applications amongst other hormone replacement therapy (HRT), oral contraception, osteoporosis, menstrual migraine and estrogen hormone sensitive cancers.

“Our results in the DMBA rat model for mammary tumour growth show that E4 prevents tumor initiation by DMBA and inhibits the growth of existing DMBA-induced tumors” concluded Monique Visser, PhD., principal scientist of the project and Program Director Estetrol at PRB. “The rat DMBA model is a mammary tumour model and the preferred tool to assess the potential in vivo prophylactic and therapeutic effects of new drugs in breast cancer.”

She added : “One particularly striking finding was the fact that E4 was found to have an estrogen antagonistic effect on breast tumour tissue, especially surprising since other estrogenic hormones used in HRT and in contraception, such as Estradiol (E2) and Ethinylestradiol (EE), are known to have a stimulatory effect on breast cancer growth”.

Prof. Herjan Coelingh Bennink, MD, PhD., gynecologist and founder and CEO of Pantarhei Bioscience, added. “At present the first choice endocrine treatment of “breast cancer is aromatase inhibitors (AIs). However, these drugs often cause serious side effects for patients, including arthralgia (joint pain), frequent hot flushes and sweatings, interference with cognition, bone loss and fractures. This is caused by the extreme estrogen deficiency induced and up to 50% of patients discontinue treatment with AIs, especially because of arthralgia.”

He continued: “The unique properties of E4 with estrogenic effects on organs such as the vagina, the joints, bone and the brain and estrogen antagonistic effects on the breast, makes E4 potentially suitable for estrogenic add-back therapy to counteract the side effects of the AIs, without stimulating the growth of breast tumours”, explained Prof. Coelingh Bennink.

“This hypothesis will be tested now in a multi-center clinical study in women with breast cancer”.

He added: “The profile of E4 suggests that the use of E4 in oral contraception, HRT and other applications may not increase the risk of breast cancer”.

About Pantarhei Bioscience B.V.

Pantarhei Bioscience B.V. is a specialty pharmaceutical company focusing on the development of innovative, proprietary treatments in the fields of Women’s Health and the Endocrine Treatment of Cancer. Within these disease areas, Pantarhei has generated product opportunities based on its ability to identify (novel) medical uses for endogenous human biologicals and/or (combinations of) existing drugs. The Company's lead product is Estetrol (E4) a natural human estrogen for e.g. oral contraception, hormone replacement therapy, breast- & prostate cancer and osteoporosis. Other priority projects are the ZP3 project for ovarian cancer and the ARC project solving mood and sexual problems associated with androgen loss during oral contraception.

For more information, please contact Tristan Jervis or Alex Heeley, De Facto Communications on 44 (0) 207 861 3019 or e-mail:

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