A multicenter randomized placebo-controlled trial evaluating daidzein-rich isoflavone aglycones in endometriosis-associated dysmenorrhea

Technical Summary: Daidzein-Rich Isoflavone Aglycones in Endometriosis-Associated Dysmenorrhea

Problem Statement
Endometriosis is a chronic inflammatory condition affecting approximately 10% of reproductive-age women, characterized by extra-uterine endometrial-like tissue growth, chronic pelvic pain, and infertility. Current standard-of-care treatments, including GnRH agonists/antagonists, dienogest, and oral contraceptives, rely on suppressing estrogen signaling and ovulation. While effective for pain management, these hormonal therapies preclude conception during treatment and do not improve pregnancy rates, creating a critical therapeutic gap for patients desiring fertility preservation. There is an urgent need for non-hormonal interventions that alleviate pain without suppressing ovarian function.

Methodology
The authors conducted a multicenter, randomized, double-blind, placebo-controlled trial involving Japanese women aged 20–50 with clinically diagnosed endometriosis and dysmenorrhea (Visual Analog Scale [VAS] ≥ 20).

• Intervention: Participants were randomized to receive either Daidzein-rich isoflavone aglycones (DRIAs) at 30 mg/day or a matching placebo for four months. DRIAs are a food-derived compound developed as a dietary supplement (AglyMax®).
• Study Design: The trial utilized a minimization method for randomization, balancing groups based on baseline dysmenorrhea severity, cyst diameter, and serum CA125 levels. The study was registered with the Japan Registry of Clinical Trials (jRCTs051200074).
• Sample Size and Constraints: The study aimed for 110 participants (55 per group) based on a pilot study and an estimated 40% placebo response. However, recruitment was significantly impacted by the COVID-19 pandemic, resulting in 81 randomized participants (40 DRIAs, 41 placebo) and 71 participants included in the modified intention-to-treat (mITT) analysis.
• Statistical Analysis: The primary endpoint was the change in dysmenorrhea VAS score, analyzed using a baseline-adjusted linear mixed model (LMM) with group, time, and group-by-time interaction as fixed effects. Secondary endpoints included changes in endometriotic cyst diameter, other pain symptoms (dyspareunia, dysuria, dyschezia), serum CA125 levels, and safety parameters.

Key Results

• Primary Endpoint (Dysmenorrhea Pain): Both groups showed significant improvement in VAS scores over time (p < 0.001). While the group-by-time interaction was not statistically significant (p = 0.344), a significant between-group difference favoring DRIAs was observed specifically at Month 3 (estimated difference: −13.53, 95% CI −23.8 to −3.22; adjusted p = 0.041). The direction of effect consistently favored the DRIAs group across all time points.
• Responder Analysis: At Month 4, the responder rate (defined as ≥30% reduction in VAS) was higher in the DRIAs group (73.5%) compared to the placebo group (56.8%), though this difference was not statistically significant (p = 0.2134).
• Secondary Endpoints:
  • Cyst Diameter: No significant changes were observed in the maximum diameter of ovarian endometriomas in either group, and no between-group differences were found.
  • Other Pain Symptoms: No significant group-by-time interactions were found for dyspareunia, dysuria, or dyschezia.
  • Biomarkers: Log-transformed serum CA125 levels decreased significantly from baseline to Month 4 across both groups (p = 0.035), but no significant between-group difference was detected at Month 4 (p = 0.574).
• Safety: The treatment was well-tolerated. One participant in the DRIAs group experienced a skin rash and discontinued; no serious adverse events or clinically relevant laboratory abnormalities were observed in either group.

Key Contributions and Claims of Significance
The paper claims to provide the first controlled clinical evidence supporting the use of an aglycone-rich isoflavone formulation as a monotherapy for endometriosis-associated pain in reproductive-aged women.

• Novel Mechanism: Building on preclinical data showing DRIAs exert anti-proliferative and anti-inflammatory effects via estrogen receptor β (ERβ) and modulate local estrogen metabolism (suppressing HSD17β1 and increasing EST), this study translates these findings to a clinical setting.
• Fertility Preservation: A primary significance of the study is the demonstration of pain reduction without the suppression of ovulation. Unlike standard hormonal therapies, DRIAs offer a potential therapeutic option for women who wish to conceive or preserve reproductive function, addressing a major limitation of current treatments.
• Clinical Relevance: The authors note that the magnitude of pain reduction observed at Month 3 exceeds commonly reported minimal clinically important differences for chronic pain, suggesting the effect is clinically meaningful despite the study's statistical limitations.
• Safety Profile: The study reinforces the short-term safety of DRIAs, noting no serious adverse events, which supports its potential as a food-derived therapeutic alternative.

Limitations and Modest Conclusions
The authors explicitly acknowledge that the study was underpowered due to recruitment constraints caused by the pandemic, which may have limited the ability to detect statistically significant differences in secondary endpoints and at later time points (Month 4). They do not claim definitive proof of efficacy but rather a "consistent trend" and "support for further evaluation." The paper concludes that while DRIAs appear to be a safe, non-hormonal option for managing dysmenorrhea, adequately powered studies with extended follow-up are required to confirm the durability of the effect and evaluate impacts on fertility outcomes.