In 2000 and 2014, respectively, the former Director of R&D WH at Organon, endocrinologist and gynecologist Prof. Herjan Coelingh Bennink (HCB), founded Pantarhei Bioscience and Pantarhei Oncology; Dutch biopharmaceutical companies developing unique innovative treatment concepts in the fields of “Women’s Health” (WH) and “Reproductive Endocrine Oncology” (REO). Pantarhei Bioscience for the development of E4 for combined oral contraceptives (COCs) and menopausal hormone therapy (MHT), and Pantarhei Oncology for estrogen treatment of advanced breast and prostate cancer. Finally, in 2019, PEI (Pandora Endocrine Innovation) was established. The companies have since filed more than 220 patents worldwide. HCB’s focus is now primarily on PEI.

RE4 contraceptive pill

The common thread in the Pantarhei and PEI companies is the fetal estrogen Estetrol (E4). For instance, Herjan and his team are convinced that the PEI-patented RE4W contraceptive pill will replace the current pill, which consists mostly of synthetic estrogens and in all cases synthetic progestogens, in the future with the GnRH antagonist Relugolix and the fetal estrogen Estetrol (E4). A publication on this topic recently appeared in AOGS, among others. (A concept for a new approach to combined oral contraception from adolescence to perimenopause: continuous use of the oral GnRH antagonist Relugolix and the fetal estrogen Estetrol)

HCB: ‘It is expected that the relugolix estetrol combination RE4W will enable women to control their fertility and prevent menstrual cycle-related problems, while offering a smooth transition through perimenopause into the postmenopause and decreasing the risk of breast cancer.’

PEI is currently seeking a financier for the development of RE4W.

Even if you have been living and working with it for decades, eventually the time comes to hand things over or at least make ‘future-proof changes’. For PEI, this will happen during the E4 symposium on July 5, 2026, in Bergen (NH). On that date, Herjan Coelingh Bennink will hand over active responsibilities for his company PEI, to a number of successors, including Chief Office Manager Karlijn Sistermans, who previously held this position at Pantarhei for approximately 15 years, and PEI’s new CEO, the Swedish Dr. Karolina Afors.

Karolina Afors is a consultant Obstetrician & Gynaecologist with over 15 years of experience working in the NHS and a strong track record in research and development. Karolina:‘As an internationally-recognised consultant gynaecologist, health educator, and advisor with extensive knowledge of chronic pelvic pain and endometriosis, I’m passionate about developing transformative solutions blending pharmaceutical, medical and lifestyle interventions.

I aim to drive innovation in women’s healthcare, addressing the historic underfunding of research in this sector. With almost 20 years of experience as a women’s health specialist, working across both clinical and corporate pharmaceutical settings, my unique perspective takes into consideration biological, social, and psychological factor.’

Karolinska Institute Sweden

A new R&D Director from Sweden - where have we encountered that country before? We dig back into history and land in 1965. In that year, the natural estrogen Estetrol was discovered at the Swedish Karolinska Institute (Stockholm). HCB: ‘Estetrol is produced by the human fetus during pregnancy. Such a hormone, already present during pregnancy, should be a safe hormone, and we have demonstrated this in clinical studies over the past 25 years. In 2022, Estetrol in a contraceptive pill reached the primary endpoint: market authorization. Canada was the first, followed by the EMA and FDA.’

Change, but do not stop. In this way, Coelingh Bennink remains involved with PEI as Chairman of the Supervisory Board. He was also invited in 2025 to affiliate with the Karolinska Institute in Stockholm. From these positions, he will continue his quest together with a new, passionate team.

Portfolio PEI

1)        Women’s Health 

·        Hormonal Contraception,

·        Menopausal Hormone Therapy,  

·        Infertility,

·        Pregnancy

2)        Endocrine treatment of COVID-19

    3)     Reproductive Endocrine Oncology (REO)

* Advanced breast cancer

* Advanced prostate cancer

See www.pandoranova.com/portfolio for the full portfolio.