Demographic Gaps and Requirements for Participation: A Systematic Review of Clinical Trial Designs in Hidradenitis Suppurativa

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory disease that disproportionally affects women, as well as Black and biracial individuals. While adalimumab remains the only therapy approved by the Food and Drug Administration for HS, many HS clinical trials for novel and re-tasked therapies are ongoing or upcoming. To optimize treatment equity, reflect the patient population, and facilitate trial participation, it is important to elucidate aspects of clinical trial protocols that may systematically exclude specific patient groups or impose hardships. Objective: The study aimed to systematically review inclusion and exclusion criteria as well as participant demographics in HS clinical trials. Methods: A literature search of PubMed, Embase, Cochrane Central, and Web of Science databases was conducted. Peer-reviewed publications of randomized controlled trials that were written in English and had at least 10 participants were included. Title and abstract screening and data extraction were completed by two independent reviewers, with disagreements resolved by a third. Results: Twenty-three studies totaling 1,496 adult participants met the inclusion criteria. Race and ethnicity were not reported in 473/1,496 (31.6%) and 1,420/1,496 (94.9%) trial participants, respectively. Trial participants were predominantly white (811/1,023, 79.3%) and female (1,057/1,457, 72.5%). The median of each study's average age was 35.7 years (IQR 33.5-38.0), and 17/23 (73.9%) trials excluded pediatric patients. Nearly all participants had Hurley Stage II (499/958, 52.0%) or Hurley Stage III (385/958, 40.2%) disease. Many trials excluded patients who were pregnant (19/23, 82.6%) and breastfeeding (13/23, 56.5%), or who had HS that was "too severe"(8/23, 34.8%) or "too mild"(16/23, 70.0%). Frequently, trial protocols required prolonged washout periods from HS therapies, relatively long duration in the study's placebo arm, and prohibited concurrent analgesic use. Conclusions: This systematic review of 23 HS clinical trials totaling 1,496 participants identified substantial hardships imposed by trial participation, high rates of missing race and ethnicity data, and low representation of key patient groups, including those who identify as Black. Future trials with pragmatic study designs, broader inclusion criteria, and study sites in diverse communities may alleviate burdens of trial participation and improve enrollment of diverse patient groups.