Racial Inequities In Medicine: The Consequences Of Historical Unethical Experimentation In Clinical Trials

By Cornelia Baumgartner-Diolaiuti, Clinical Operations Expert, Cetacea Clinical, and Louis Johnson, Principal Consultant, Aries Clinical Consulting

Clinical trials are the foundation of modern medicine, but they have a complicated legacy, especially for Black Americans. The Tuskegee Syphilis Study and other unethical research practices targeting Black communities left a lasting scar of mistrust of the medical establishment. Despite significant ethical reforms, racial disparities in clinical trial participation persist today. Black Americans remain underrepresented in pivotal drug trials, which impacts the effectiveness, safety, and accessibility of new treatments for diverse populations.

In part one of this two-part series, we explored the historical context of mistrust. Part two looks at the ongoing diversity gap in clinical research and the tangible consequences for health outcomes. It also examines efforts to close these gaps and build a more inclusive, equitable future for clinical trials, because when research reflects the diversity of real-world patients, everyone benefits.

Modern-Day Gaps In Clinical Trial Diversity

Despite ethical reforms, representation in clinical trials remains inequitable. Racial and ethnic minorities, especially Black Americans, are still underrepresented in many research studies and drug trials. This lack of diversity is well documented. For example, an analysis of 32,000 participants in U.S. clinical trials for new drugs in 2020 found that only 8% were Black, even though Black people are ~14% of the population¹⁰. Similarly, FDA data show only 5% of patients in pivotal cancer drug trials from 2008-2018 were Black¹². Overall, studies have found that the proportion of Black participants in trials is often one-third or less of their proportion of the disease burden — and this gap hasn’t significantly improved⁹.

This underrepresentation has several causes. Structural barriers play a big role; many trials are conducted at major academic medical centers, which may be less accessible to communities of color⁹. Eligibility criteria or lack of transportation, time off work, and childcare can all disproportionately exclude Black participants⁹. Another major factor is the historical mistrust discussed in part 1: Some Black patients are wary of volunteering for research, given the legacy of abuse¹. Misinformation or lack of awareness about trials also contribute¹¹. Additionally, investigators themselves have been found to recruit fewer minority patients, sometimes due to implicit bias or assumptions about willingness to participate¹.

Whatever the reasons, the result is that many trials today do not fully reflect the patient populations who will use the treatments. Even high-profile trials have needed course-correction. For instance, during the COVID-19 vaccine trials in 2020, Moderna publicly slowed its enrollment at one point because Black Americans made up only 7% of participants, far below their 13% share of the U.S. population. The company recognized it needed more diversity to ensure confidence in the vaccine’s results and paused to recruit more Black participants¹⁰. This is a telling example of how the industry is grappling with representation issues.

Consequences Of Underrepresentation: Efficacy And Disparities

When clinical research lacks diversity, it can have serious consequences for medical outcomes and can perpetuate healthcare disparities. Medications or interventions may not work equally well for everyone, and if trials don’t include enough Black participants, we might not discover important differences. As the NIH and FDA note, drugs and vaccines can affect groups differently due to genetic variations, coexisting conditions, diet, stress, and other environmental factors⁹. Inclusive trials are crucial for safety and efficacy data across all demographics⁹.

One clear example is in cardiovascular medicine. Research has shown that certain blood pressure and heart failure drugs have different response rates in Black vs. white patients¹⁰. Several clinical trials found, for instance, that β-blockers and ACE inhibitors tend to be less effective at lowering blood pressure in many Black patients, while other drugs (like diuretics) may work better¹⁰. Over time, these findings became well accepted, leading to race-conscious treatment guidelines — e.g., hypertension recommendations that differed for Black patients — and even the development of a heart failure drug combination (hydralazine/isosorbide dinitrate) specifically tested in Black patients¹⁰. However, those insights came later than they might have, partly because early trials of cardiovascular drugs had very few Black participants. In effect, the lack of diversity initially masked crucial efficacy differences, delaying optimal care for Black patients.

Another consequence is that safety signals might be missed. If a side effect disproportionately affects a certain group, a homogeneous trial could fail to detect it. For example, concerns have been raised in asthma treatment: a large post-market study found that the asthma drug salmeterol was associated with higher risk of severe attacks in Black patients compared to others, a risk not evident in earlier trials that had fewer Black participants. Similarly, dosage or screening guidelines can be skewed by incomplete data. In 2021, the U.S. Preventive Services Task Force revealed it could not issue tailored guidelines for colon cancer screening in Black patients (who have the highest colon cancer rates in the country) because too few Black patients had been in the underlying studies⁹. This shows how lack of inclusion can even hamper the development of appropriate medical recommendations⁹.

Furthermore, underrepresentation can exacerbate disparities in access to new treatments. If trials don’t include Black participants, regulatory approvals and insurance coverage may end up narrowed to the groups studied, excluding others⁹. It also can undermine Black patients’ confidence in whether a new drug will work for them. Surveys have found that Black individuals are more likely to trust and accept a medication if they know Black patients were well-represented in the research⁹. Conversely, lacking that assurance may lead to a lower uptake of beneficial innovations (for instance, hesitancy about vaccines or novel therapies). In short, a non-diverse patient base risks creating a cycle where health innovations bypass the very groups who could benefit most, widening outcome gaps⁹.

Notably, researchers warn that current racial disparities in health (e.g., higher rates of hypertension, diabetes, and certain cancers in Black populations) could worsen if those groups don’t get equal access to cutting-edge treatments and trials⁹. For example, Black Americans suffer higher rates of diseases like diabetes and HIV, but if trials for new drugs for those conditions under-sample Black patients, the resulting treatments might not be optimized for them. All this highlights why leading institutions and even the FDA have called for renewed efforts to improve trial diversity, including requiring diversity action plans for studies and broadening eligibility criteria. It’s not just a matter of fairness; it’s about making medicine more precise and effective for everyone.

The Intersection Of Race And Gender: Black Women’s Health Disparities

When considering medical research and health outcomes, Black women face a double minority status — both race and gender — that has led to their underrepresentation. Historically, Black women were uniquely victimized in some unethical studies (as seen with Sims’ surgeries or forced sterilizations) and at the same time often excluded from mainstream clinical trials that focused on white males. This intersection has had lasting effects on Black women’s health.

Until the early 1990s, women were not included in many clinical trials. From 1977 to 1993, the FDA had effectively banned most women of childbearing age from early-phase drug trials out of concern for potential pregnancy-related risks¹⁴. Therefore, a generation of medical research was conducted predominantly on men. The U.S. NIH Revitalization Act of 1993 mandated the inclusion of women and minorities in federally funded research¹⁴. While this was a crucial step, progress has been uneven. Women of color, and especially Black women, remain underrepresented in clinical research.¹³ One recent review noted that the exclusionary practices of the past have left persistent “knowledge gaps” in conditions that affect women disproportionately.¹⁴ Those gaps are even wider when it comes to Black women.

The case of breast cancer illustrates the issue. Breast cancer is the most common cancer diagnosed in Black women, and Black women have a 40% higher mortality rate than white women with breast cancer¹¹. They also experience more aggressive subtypes, like triple-negative breast cancer (TNBC), at disproportionately high rates¹¹. Despite this, Black women have been woefully underrepresented in many breast cancer clinical trials. A recent analysis found that Black women’s enrollment in trials for TNBC therapies was nearly three times lower than expected based on their share of the population¹². In other words, even as Black women face the brunt of TNBC, the trials for new TNBC drugs often had <5% Black participant¹². This under-enrollment hinders the development of effective treatments for diverse patients¹² and may contribute to Black women not responding as well to new cancer drugs simply because those drugs were not vetted in patients like them. Researchers at Rutgers Cancer Institute note that such disparities in trials can lead to “poorer outcomes for Black patients and a lack of knowledge of the true drug efficacy in this population” once treatments are approved¹¹. This may factor into why Black women haven’t seen as large a benefit from recent cancer advances, worsening the outcome gap.

Black women’s health disparities go beyond cancer. Cardiovascular disease in women was long understudied because trials focused on men, leading to misperceptions that heart attacks were a “man’s problem.” Another glaring example is maternal health: Black women in the U.S. are three to four times more likely to die from pregnancy-related complications than white women¹⁵. While the causes are multifactorial, experts point out that there are research gaps in understanding conditions like preeclampsia, hemorrhage, and cardiomyopathy, specifically in Black women¹⁵. Until very recently, there were few large studies targeting Black maternal health or testing interventions in the communities most affected. The lack of focused research means clinical practices may not be fully optimized to protect Black mothers. Moreover, the intersection of race and gender has historically led to Black women’s pain and symptoms being dismissed at higher rates — a harmful bias that traces back to myths from slavery times². Even today, studies reveal that some medical professionals underestimate Black patients’ pain levels or concerns.

In response to these challenges, there are growing initiatives to amplify Black women’s representation and address gendered racial inequities in health research. The NIH now has an Office of Research on Women’s Health, and there are calls to not only include Black women in trials but also to analyze data by race and sex to pinpoint disparities¹⁴. Community organizations and researchers are also actively reaching out to Black women – for example, through programs connecting Black women with clinical trial information¹¹ or through patient navigator programs in Black communities for diseases like breast cancer. These efforts, alongside policy changes, aim to ensure that Black women are no longer an afterthought in research but rather a priority in study design and recruitment when relevant.

Key Takeaways And Ongoing Challenges

The historical context of medical experimentation on Black communities has left a legacy of mistrust and injustice that the medical field is still addressing today. These unethical studies caused immense harm but also catalyzed major reforms in ethics, leading to the informed consent and human-subject protections we now consider fundamental^16. They also serve as enduring reminders of the need for vigilance against bias in research. Today, one of the biggest ethical and practical issues in medicine is the diversity gap in clinical trials. Underrepresentation of Black individuals — especially Black women – in research has tangible impacts: it can skew our understanding of diseases, limit the effectiveness of new treatments in real-world diverse populations, and contribute to ongoing health disparities. Areas like cancer treatment, cardiovascular care, and maternal health show clearly that when research does not include everyone, not everyone benefits equally from scientific progress^9,11.

However, challenges remain. Building trust is paramount — researchers must engage with communities with humility and transparency to overcome the understandable wariness that many Black Americans have⁶. Additionally, increasing diversity in trials may require innovative approaches, such as mobile health units, community-based study sites, better communication about the purpose of research, and support (financial or logistical) for participants. It also means confronting and unlearning biases within the research and medical professions, so that Black patients are seen and heard as equal partners in their care⁶. The intersection of race and gender deserves special focus. Black women’s voices and data need to be uplifted in healthcare research, given the severe disparities they face.

The goal is to create a medical research environment where experiments like those done on Black communities in the past are unthinkable, and where all populations are fairly represented in the quest for new cures. By learning from the past and actively improving the present, the hope is to shape a more ethical, effective, and equitable future for medical science — one in which the lives and health of Black men, women, and children are valued equally, and where medical breakthroughs benefit everyone.

References:

1. Howell, J.D. Understanding Black Distrust of Medicine – University of Michigan School of Public Health Understanding Black Distrust of Medicine | Findings | University of Michigan School of Public Health | Racism | Vaccines | Infectious Disease | Health Disparities
2. More than Tuskegee: Understanding Mistrust about Research Participation – Journal of Healthcare for the Poor and Underserved pmc.ncbi.nlm.nih.gov
3. Health Research Authority (UK). Henrietta Lacks and informed consent (Oct 11, 2021) Why informed consent must be at the heart of medical ethics and regulation – a blog by Lou Silver Equality, Diversity and Inclusion Manager - Health Research Authority
4. National Women’s History Museum. Biography of Fannie Lou Hamer Fannie Lou Hamer | National Women's History Museum
5. Kaiser Family Foundation – Racial and Ethnic Disparities in Access to Medical Advancements (Feb 22, 2024) Racial and Ethnic Disparities in Access to Medical Advancements and Technologies | KFF)
6. Harvard Medical School – Embracing Diversity: Inclusive Clinical Trials (June 30, 2023) Embracing Diversity: The Imperative for Inclusive Clinical Trials | HMS Postgraduate Education
7. Pharmacy Times – Equitable Representation in Triple-Negative Breast Cancer Clinical Trials (2023) Equitable Representation in Triple-Negative Breast Cancer Clinical Trials
8. Meloney, L.G. et al. Advancing inclusion of underrepresented women in clinical research – Ther Innov Regul Sci (2022)  Advancing the inclusion of underrepresented women in clinical research - PMC
9. Northwestern Now – 30 Years After NIH Inclusion Mandate (June 6, 2023) The law mandating the inclusion of women in medical research turns 30. Where do we stand? - Northwestern Now
10. AMA Journal of Ethics – Black Maternal Health Inequity (2024) Cultivating Critical Love to Improve Black Maternal Health Outcomes | Journal of Ethics | American Medical Association
11. (CDC, 2024) Centers for Disease Control and Prevention. (n.d.). Tuskegee study - Timeline and impact on research. https://www.cdc.gov/tuskegee/about/effects-research.html

About The Authors:

Cornelia Baumgartner-Diolaiuti is the founder of Cetacea Clinical GmbH, a clinical operations consultancy specializing in early-phase oncology and infectious disease trials. She began her career as a CRA at Pfizer and has since gained over 24 years of experience in clinical research, holding key roles at NBE-Therapeutics, Aridis Pharmaceuticals, and Mundipharma EDO. At Cetacea Clinical, Cornelia provides strategic consulting, vendor oversight, and a ready-to-use quality management system (QMS) to biotech startups. Connect with Cornelia on LinkedIn.

Louis Johnson is a medical research professional with over 25 years of experience in the pharmaceutical industry. The first three years were in pharma sales, with the remaining years in clinical research. His expertise lies in clinical trial management and operations with a special focus on diversity in clinical trials and healthcare equality.  Louis is also skilled in the areas of process improvement, strategy, and planning. Louis has Bachelor of Arts and Master of Science degrees in biology from Hampton University and a Doctor of Health Administration (abd) from A.T. Still University.  In his spare time, he is a fitness enthusiast and is a volunteer football coach. He lives in the western suburbs of Chicago.