Who Is Represented in Endometriosis Clinical Trials?

FDA-approved endometriosis trials do not consistently reflect disease prevalence across racial and ethnic groups.

Key Points

Highlights: 

• Racial and ethnic representation in clinical trials leading to FDA approval of endometriosis treatments is inconsistently reported and does not fully reflect the U.S. population.

Importance:

• Transparent and standardized reporting of race and ethnicity is essential to ensure equitable trial representation, reliable assessment of treatment efficacy, and generalizability of results in endometriosis care.

What’s done here:

• This research letter of cross-sectional analysis evaluated clinical trials conducted in North America that led to FDA approval of endometriosis therapies between 1980 and 2025.
• Enrollment fractions by race were compared with population-based estimates of endometriosis prevalence to assess representation across racial and ethnic groups.

Key results:

• Among trials reporting race, Black participants were overrepresented relative to White participants.
• Asian or Pacific Islander participants were underrepresented in trials that included these categories.
• Ethnicity data were not reported in any of the included trials.

Limitations:

• Reliable estimates of endometriosis prevalence by race and ethnicity remain limited.
• Findings are restricted to North American clinical trials and may not be generalizable to other regions.

From the Editor-in-Chief – EndoNews

"The study by Levin et al. delivers an overdue and necessary audit of the evidentiary foundations on which endometriosis therapies have been approved over the past four decades. By interrogating the racial and ethnic composition of clinical trials leading to approval by the U.S. Food and Drug Administration, the authors expose a paradox that is both scientifically troubling and ethically consequential: among trials that reported race, Black participants were often overrepresented, while Asian and Pacific Islander individuals were consistently underrepresented.

This imbalance is not a trivial reporting artifact. Endometriosis is a biologically heterogeneous disease, with growing evidence that symptom profiles, diagnostic delays, comorbidity patterns, and possibly treatment responses differ across populations. When trial enrollment does not reflect the populations ultimately treated—and when race and ethnicity are inconsistently defined or incompletely reported—the external validity of regulatory approvals is weakened. In such a context, “approval” risks becoming a narrow regulatory milestone rather than a robust guarantee of generalizable benefit.

Importantly, the authors do not frame their findings as evidence of inclusion success or failure alone, but as a signal of structural inconsistency across decades of trial design, reporting standards, and regulatory expectations. The long temporal window of this analysis underscores that progress in therapeutic innovation has not been matched by progress in methodological equity. That this gap persists into contemporary trials should prompt reflection not only among investigators, but also among sponsors, regulators, and journals.

Going forward, transparent, standardized, and mandatory reporting of race and ethnicity—paired with enrollment strategies that reflect disease epidemiology—should be regarded as a core component of scientific rigor, not an optional ethical add-on. Without this recalibration, disparities risk being perpetuated at the very stage where evidence is canonized into clinical practice.

This study thus serves as a call to action: to align the science of endometriosis treatment with the realities of the populations it aims to serve, and to ensure that regulatory approval rests on evidence that is both methodologically sound and socially responsible."

Lay Summary

Clinical trials play a critical role in determining which treatments are approved for use, yet who is included in these trials can strongly influence how well results apply to the broader patient population.

A new research letter published in British Journal of Obstetrics and Gynaecology found important gaps in how race and ethnicity are reported—and represented—in clinical trials that led to U.S. Food and Drug Administration (FDA) approval of endometriosis treatments.

The researchers reviewed clinical trials conducted between 1980 and 2025 that supported FDA approval of medications for endometriosis-related symptoms.

Of the 9 trials identified, only 4 reported participants’ race, and none reported ethnicity. Among the trials that did include racial data, Black participants were enrolled at higher rates than White participants, while participants of Asian or Pacific Islander background were underrepresented.

To conduct this analysis, a team led by Dr. Raanan Meyer from Cedars-Sinai Medical Center examined enrollment fractions by race and compared them with estimates of endometriosis prevalence in the U.S. population. Three North American phase III trials, including a total of 3,211 participants, formed the basis of the final analysis. These trials evaluated commonly used therapies such as gonadotropin-releasing hormone agonists, antagonists, and progestins.

The finding that Black participants were overrepresented was unexpected, given prior epidemiologic studies suggesting a lower diagnosed prevalence of endometriosis in Black women. At the same time, the lack of ethnicity reporting and the underrepresentation of Asian or Pacific Islander participants highlight important blind spots in trial design and reporting.

The authors emphasize that inconsistent racial and ethnic data limit the ability to fully understand whether treatments perform similarly across populations.

They conclude that future endometriosis trials should prioritize transparent, standardized, and comprehensive reporting of race and ethnicity to ensure that approved therapies are truly applicable to all patients affected by the disease.

Research Source: https://pubmed.ncbi.nlm.nih.gov/40928122/