Non-Whites Remain Sorely Underrepresented in Phase 3 Psoriasis Trials

Ted Bosworth

October 21, 2020

Non-White patient participation in phase 3 therapeutic trials for plaque psoriasis is less than 15%, according to a recently published analysis of data from the ClinicalTrials.gov database.

The exact figure drawn from the survey of 82 trials was 14.2%, but 20 (24%) of the trials did not include ethnoracial data at all, and only 65% of those with data had complete data, according to a report in the British Journal of Dermatology by a team of investigators from the department of dermatology at the University of California, San Francisco.

"The remaining studies reported the percentage of white participants only or white participants and one additional ethnoracial group," reported the investigators, led by Vidhatha D. Reddy, a medical student at UCSF.

The investigators broke down participation by race in all phase 3 plaque psoriasis trials that enrolled adults and had posted results by May 2020. Data from trials of medications yet to be approved were excluded.

Most trials were multinational. The medications evaluated included 11 biologics, 10 topicals, 2 oral systemic agents, and a phosphodiesterase type-4 inhibitor. The 82 trials included in this analysis enrolled 48,846 collectively.

From trials that identified race, 85.8% of 39,161 participants were White, 3.09% of 25,565 patients were Black, 19.55% of 11,364 patients were Hispanic or Latino, and 9.21% of 30,009 patients were Asian. Of trials that included Native Americans or Pacific Islanders, fewer than 2% of participants represented this category.

Non-White patients remain underrepresented even when recognizing differences in the prevalence of psoriasis. For example, one recent survey found the U.S, prevalence of psoriasis to be about half as great in Blacks as it is in Whites (1.9% vs. 3.9%), but the representation of Blacks in the phase 3 trials evaluated by Mr. Reddy and colleagues was more than 20 times lower.

There are many reasons to suspect that lack of diversification in psoriasis trials is impeding optimal care in those underrepresented. Of several examples offered by the authors, one involved differential responses to adalimumab among patients with hidradenitis suppurativa with genetic variants in the BCL2 gene, but the authors reported racially associated genetic differences are not uncommon.

"Estimates have shown that approximately one-fifth of newly developed medications demonstrate interracial/ethnic variability in regard to various factors, such as pharmacokinetics, safety and efficacy profiles, dosing, and pharmacogenetics," Mr. Reddy and his coinvestigators stated.

Although racial diversity in the design and recruitment for clinical trials has not been a priority in trials involving psoriasis, other skin diseases, or most diseases in general, the authors cited some evidence that this is changing.

"Since 2017, research funded by the National Institutes of Health has been required to report race and ethnicity of participants following an amendment to the Health Revitalization Act," according to the authors, who suggested that other such initiatives are needed. They advocated "explicit goals to increase recruitment of people of color" as a standard step in clinical trial conduct.

Hypertension trials were cited as an example in which diversity has made a difference.

"Although Black patients are at an elevated risk of developing hypertension, it was not until the enrollment of a substantial proportion of black participants in ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) that enough data on Black patients were available to make specific treatment recommendations in this population," they noted.

Impossible to Know Treatment Benefits Without Ethnoracial Data

Without clinical trials that include a substantial proportion of Blacks or patients from other racial and ethnic groups, the study investigators concluded that it is impossible to determine whether response to patients of different races and ethnicities benefit similarly. This concern seems particularly apt for diseases of the skin.

Another investigator who has considered this issue, Junko Takeshita, MD, PhD, an assistant professor of dermatology at the University of Pennsylvania, Philadelphia, agreed.

"Lack of diversity among participants in phase 3 clinical trials for psoriasis is a problem," said Dr. Takeshita, who led a study of racial differences in perceptions of psoriasis therapies that was published last year.

In that study, "my research group not only found differences in perceptions about biologics between Black and White patients with psoriasis, but we have also shown that Black patients with psoriasis are less likely to receive biologic treatment," she reported. There are many explanations. For example, she found in another study that Black patients are underrepresented in direct-to-consumer advertisements for biologics.

This problem is not unique to psoriasis. Underrepresentation of Blacks and other ethnoracial groups is true of other skin diseases and many diseases in general, according to Dr. Takeshita. However, she cautioned that the 3% figure for Black participation in psoriasis trials reported by Mr. Reddy and colleagues is not necessarily reflective of trials in the United States.

"This study included international study sites that are recruiting patients from populations with different demographics than the U.S.," she noted. By including sites with only Asian patients or countries with few Blacks in the population, it dilutes Black representation. She would expect the exact proportion of Black participants to be somewhat higher even if they are "still likely to be underrepresented" if the analysis has been limited to U.S. data.

The research had no funding source. Three of the nine authors reported financial relationships with pharmaceutical companies.

SOURCE: Reddy VD et al. Br J Dermatol. 2020 Sep 17. doi: 10.1111/bjd.19468.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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