HMI-115, a Potential First-in-Class Treatment for Endometriosis, Published Proof-of-Concept Phase II Clinical Trial Results in The Lancet Obstetrics, Gynaecology, & Women's Health

HMI-115 demonstrates statistically significant improvement of endometriosis-related pain

Dysmenorrhea NRS scores decreased by 41.57%, 34.72%, and 27.35% across the three dosage groups

Non-menstrual pelvic pain NRS scores decreased across all HMI-115 dosage groups, with sustained efficacy 12 weeks after the end of treatment

HMI-115 did not trigger hypoestrogenic side effects such as hot flashes or depression; bone mineral density and key sex hormone levels remained stable during treatment

SHANGHAI, Nov. 5, 2025 /PRNewswire/ -- Hope Medicine (HopeMed), a clinical-stage innovative biotech company, in collaboration with a joint research team from Peking University, Peking Union Medical College Hospital, Shandong University, and other institutions, announced that the results of a proof-of-concept Phase II clinical trial evaluating HMI-115 (a human monoclonal antibody targeting the prolactin receptor) for the treatment of endometriosis-related pain have been published in The Lancet Obstetrics,  Gynaecology, & Women's Health. The article is titled "Safety and efficacy of subcutaneous injection with HMI-115 versus placebo in endometriosis-associated pain in premenopausal women: a multicentre, double-blind, randomised, proof-of-concept phase 2 trial." The study aimed to evaluate the safety, tolerability, and preliminary efficacy of HMI-115 in premenopausal women with moderate to severe endometriosis-related pain. A total of 108 patients with surgically confirmed endometriosis (via laparoscopy or laparotomy) were enrolled and randomly assigned in a 1:1:1:1 ratio to receive subcutaneous injections of HMI-115 (60 mg, 120 mg, or 240 mg) or placebo every two weeks for 12 weeks. The primary efficacy endpoint was the change from baseline in dysmenorrhea numeric rating scale (NRS) scores at Week 13.

Results showed that at the end of the 12-week treatment period, dysmenorrhea NRS scores decreased by 41.57%, 34.72%, and 27.35% in the 240 mg, 120 mg, and 60 mg HMI-115 groups, respectively, compared to the 18.61% reduction in the placebo group. Non-menstrual pelvic pain NRS scores also decreased across all HMI-115 dosage groups, with sustained efficacy observed at Week 25. The percentage reductions of dysmenorrhea and non-menstrual pelvic pain in the 240 mg group is statistically significant compared to placebo.  Additionally, HMI-115 groups showed improvements in the Endometriosis Daily Impact Pain (EDIP) scores and reduced use of NSAID rescue medications.

In terms of safety, the incidence of treatment-emergent adverse events (TEAEs) was 56%, 59%, 75%, and 37% in the 60 mg, 120 mg, 240 mg HMI-115 groups, and placebo group, respectively. The most common adverse events included injection site itching and rash, dizziness, nausea, nasopharyngitis, and headaches. No treatment-related deaths or serious adverse events were reported. Unlike existing hormonal therapies, HMI-115 did not cause hypoestrogenic side effects such as hot flashes or depression, and bone mineral density and key sex hormone levels remained stable during treatment.

This study is the first to clinically validate the potential of blocking prolactin receptor signaling to alleviate endometriosis-related pain. Its non-hormonal mechanism of action avoids interference with ovulation and menstrual cycles, offering a promising new option for patients with fertility intentions. The research team stated that these findings provide a strong foundation for initiating longer-duration Phase III trials to further evaluate the clinical benefits and risks of HMI-115.

About HMI-115

HMI-115 is a highly specific human monoclonal antibody that non-competitively blocks prolactin receptor-mediated signaling. Preclinical and Phase I clinical studies have demonstrated favorable safety profile of HMI-115. The recently published Phase II proof-of-concept trial further supports its development potential in treating endometriosis-related pain. In 2019, Hope Medicine entered into a global exclusive licensing agreement with Bayer AG for the development and commercialization of HMI-115, a monoclonal antibody targeting the prolactin receptor (PRLR), for multiple indications. HMI-115 has been granted Breakthrough Therapy Designation (BTD) by the Center for Drug Evaluation (CDE) of China's National Medical Products Administration (NMPA) for the treatment of moderate to severe pain associated with endometriosis.

About Endometriosis

Endometriosis is a common gynecological disease characterized by the implantation of endometrial cells in locations outside the endometrium, typically presenting as chronic inflammation. The endometrium is a layer of mucosal tissue within the uterine cavity that undergoes hormone dependent changes during the menstrual cycle. Endometriosis is common in women of childbearing age. According to comprehensive literature reports, about 10% of women of childbearing age, or approximately 190 million women worldwide, are affected by endometriosis. In addition, 20%–50% of women with infertility and 71%–87% of women with chronic pelvic pain are reported to have endometriosis. Symptoms include lower abdominal and pelvic pain, dysmenorrhea, painful intercourse, and infertility. Endometriosis negatively impacts patients' quality of life and sex, psychology, and social behavior. Endometriosis is one of the leading causes of dysmenorrhea, infertility, and chronic pelvic pain. It often leads to decreased quality of life and affects patients' sexual health, psychology, and social behavior. Globally, the condition represents a potential market opportunity of approximately USD 200 billion.

About Hope Medicine

Hope Medicine Inc. is a science-driven clinical-stage biopharmaceutical company with research laboratories and offices in Beijing, Shanghai, and Nanjing, China. HopeMed is established on the in-depth expertise in translational medicine and decades of research of Professor Rui-Ping Xiao's laboratory at the Institute of Molecular Medicine of Peking University. Based on excellent scientific research and to improve the quality of life, HopeMed is committed to the research, development, and commercialization of first-in-class medicines for common and major diseases that threaten human health.

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SOURCE Hope Medicine