Bayer launches phase III trial testing Mirena for uterine condition with no treatments

NAEH can cause heavy or abnormal bleeding and, if left untreated, may progress to uterine cancer

Bayer is moving its flagship hormonal intrauterine device into a new arena. 

The global life sciences company has announced the start of a global Phase III clinical trial to test Mirena as a treatment for nonatypical endometrial hyperplasia (NAEH)—a precancerous thickening of the uterine lining that currently has no approved medical therapy. 

NAEH, driven by an imbalance of estrogen and progesterone, can cause heavy or abnormal bleeding and, if left untreated, may progress to uterine cancer. The condition affects between 121 and 270 out of every 100,000 women annually, depending on geography, age, and menopausal status. With no sanctioned treatments available, clinicians often rely on off-label hormonal therapies or surgery. 

Positioning the study as part of its broader investment in women’s health, Bayer said it aims to fill that gap. “Having a leading position in global women’s health we are committed to advance science focusing on innovative options to address the unmet medical need of women globally. 

"With this new Phase III study, we are now expanding our broad clinical development program for intrauterine systems to be able to support women suffering from nonatypical endometrial hyperplasia with an effective treatment,” said Christian Rommel, Ph.D., Head of Research and Development at Bayer’s Pharmaceuticals Division. 

The SUNFLOWER study—short for Study of Understanding NAEH-treatment eFficacy of LevonOrgestrel–IUS in Women Electing non-suRgical options—will compare Bayer’s 52 mg levonorgestrel-releasing intrauterine system (LNG-IUS) to oral progestin therapy. Researchers plan to enroll 207 patients across roughly 90 sites in three countries, with completion expected in about 18 months. 

Earlier studies have shown promising results for the 52 mg LNG-IUS in restoring the endometrium to a normal state, likely due to its localized hormone delivery directly inside the uterus. SUNFLOWER will formally test that effectiveness in a controlled setting. 

Mirena is a T-shaped device containing 52 mg of levonorgestrel that releases small, steady doses of the hormone once placed in the uterus. It is a long-acting reversible contraceptive that can be removed at any time by a healthcare provider. 

Depending on the country, Mirena’s approved uses include contraception, heavy menstrual bleeding, endometrial protection during estrogen therapy, and dysmenorrhea. The device is currently available in more than 120 countries.