As FDA's "Sex Differences" Guidance Reemerges, UCB Reaffirms Importance Of Including Women In Clinical Research

A conversation with Marie Teil, Global Head of Women of Childbearing Age Program, UCB Biopharma

It’s been just 30 years since the FDA first required the inclusion of women in clinical research. Now, the Agency has produced draft guidance on the importance of studying women, specifically sex differences, in the evaluation of medical products. The guidance, "Study of Sex Differences in the Clinical Evaluation of Medical Products," was published by the FDA in January 2025, removed, and then reappeared in March 2025, though its initial publication date was retained.  

UCB’s Global Head of Women of Childbearing Age Program Marie Teil is happy to see its return.

To help clinical research professionals understand the importance of this guidance, Teil explores reasons to prioritize women's inclusion in research and how the guidance is poised to support that endeavor.

Clinical Leader: What are some of the highlights of the draft guidance?

Marie Teil: The updated guidance is a significant step forward in increasing enrollment of women in clinical trials and ultimately supporting data generation for women. It’s particularly important as the last update of the guidance was in 1993 — the same year the NIH mandated the inclusion of women in clinical trials. This new guidance emphasizes the importance of considering sex differences in clinical evaluations, which is crucial for developing more effective and inclusive medical products.

I’m really pleased to see that the FDA is encouraging practices to improve the recruitment, enrollment, and retention of women in clinical trials, such as considering flexibility in scheduling, locating clinical trial sites in neighborhoods where women receive their healthcare, using mobile clinics and implementing digital health technology to collect data.

In particular, I’m glad to see that they’ve specifically mentioned the enrollment of “females of reproductive potential,” with appropriate risk mitigation efforts (e.g., contraception), as well as discussion around the inclusion of pregnant and lactating participants and the importance of collecting pharmacokinetic data during pregnancy.

This is paramount. Women living with chronic diseases, and their families, lack concrete data and clear guidance about disease management and treatment, particularly during breastfeeding and pregnancy.

What are some of the key reasons to consider and understand sex differences in research?

One reason is the physiological and biological differences between sexes that significantly influence how diseases manifest, progress, and respond to treatment, often leading to sex-specific symptoms and outcomes. One example is cardiovascular disease (CVD), where men are more likely to experience chest pain, whereas women often present with atypical symptoms such as fatigue, nausea, and shortness of breath, leading to delays in diagnosis and treatment.

Another reason is that some diseases predominantly affect women, like autoimmune diseases. Women account for nearly 80% of all chronic autoimmune diseases, yet they face significant challenges when it comes to disease management and treatment.

These challenges become even more significant for women during family planning because pregnancy introduces unique physiological changes that can alter how diseases present, progress, and are diagnosed, making it critical to consider sex- and pregnancy-specific health patterns. Although many women living with chronic diseases will need to consider treatment management during pregnancy and breastfeeding to protect both themselves and their child, only 5% of medications have been adequately monitored, tested, and labeled with safety information for use in this population.

I always say that women should be supported and protected through research, not from research.

If there isn’t an effort by the industry to enroll more women in clinical research, what is at risk?

A recent analysis by the World Economic Forum, in collaboration with the McKinsey Health Institute (MHI), found that, on average, women spend 25% more of their lives in poor health than men. This disparity is partly due to gaps in sex-specific treatment development and access.

Systemic health inequities create significant barriers, affecting not only individual well-being but also the social and economic health of entire communities.

It is known that health systems that take account of sex differences in their public health strategies are more likely to be successful and have a greater societal impact.

The lack of research and data frequently leads to confusing and often contradictory information about potential health risks, making informed decision-making even more challenging. Women should never have to choose between managing their health and growing their families.

Can you share an experience or a realization you had with sex and/or gender as it relates to investigational new drugs and their safety or efficacy?

The COVID-19 pandemic was uncharted territory, and there was a lot of uncertainty, especially for pregnant women. Would there be a vaccine safe enough for mothers, for their babies? In the field of vaccine biology, distinct sex differences have been observed.

Pregnant women with COVID-19 are at higher risk of severe illness and adverse outcomes like preterm birth and stillbirth. Initial exclusion from vaccine trials led to limited safety data and low vaccine uptake among pregnant women. Including pregnant women in clinical trials can help evaluate effective therapies, improve maternal and birth outcomes, and expedite treatment recommendations.

Watching the developments around the COVID vaccine unfold in real time reinforced my conviction about the need to generate data earlier and to accelerate our WoCBA program at UCB.

What advances affirm this is an important consideration for drug developers and clinical researchers?

A growing number of researchers and advocacy groups have called for the inclusion of pregnant and lactating women in clinical studies and have provided evidence that inclusion in research is the more ethical and responsible course of action. Although clinical research and evidence on the dosage, safety, and efficacy of medical products in these populations remains scarce, we are starting to see more initiatives, such as the development of guidance on the inclusion of pregnant and lactating women in clinical trials and the scientific societies specifically considering these populations in their clinical guidelines.

We’re encouraged by the advances we’re witnessing from the National Academies of Science, Engineering, and Medicine. Their report, Advancing Clinical Research with Pregnant and Lactating Populations, highlights the urgent need to improve research on the safety and efficacy of medications for pregnant and breastfeeding individuals. They recommend that pregnancy and lactation should be considered as conditions requiring more research, not less. The report calls for a cultural and systemic shift to ensure pregnant and lactating individuals are included in clinical research.

Doing so will lead to safer, evidence-based treatments, ultimately improving maternal and infant health outcomes.

How could this draft guidance, if finalized, impact UCB?

Our mission at UCB, which began about 10 years ago, is to empower and support women of childbearing age living with chronic diseases to make informed decisions about their healthcare — and this is embedded across early drug development, late stage, and in-market disease areas.

Our program focuses on providing women with robust data to make better informed decisions about their health, especially concerning pregnancy and managing chronic diseases. We also equip them with tools such as discussion guides to have productive conversations with their physicians, ensuring their voices are heard and fostering a shared decision-making model.

Our clinical trial protocol templates allow women who become pregnant during trials to remain in the studies and not be excluded. This innovative approach advances the industry standards, where pregnant women were typically excluded from studies.

This FDA guidance allows us to continue our commitment to women of childbearing age living with chronic diseases by encouraging joint efforts and outlining ways of working together to fill knowledge gaps. We acknowledge the collaborative nature of our mission, and we recognize that a sustainable impact cannot be achieved in isolation. This guidance allows us to partner with more patients, scientific communities, regulators, and policymakers to advance the scientific understanding of women of childbearing age living with chronic diseases.

For those wanting the latest updates and recommendations regarding sex differences in clinical research, where should they look?

At UCB, we can only speak to women of childbearing age as this is our area of expertise within clinical research. Leading scientific societies and health bodies are updating their protocols and/or clinical guidelines to include management of pregnant and breastfeeding patients with chronic diseases. We have a helpful resource on UCB.com through our women of childbearing age program that lists these efforts. Additionally, the global independent commission, BRIDGE (Better Research, Information and Data Generation for Empowerment), where I’m a co-chair, is constantly shining a light on these topics and is a great resource.

About The Author:

Marie Teil is a pharmaceutical executive with 20+ years of experience in the health field, with roles ranging from academia and clinical research to ethics and operations. She joined UCB with a visionary purpose — to establish the Women of Childbearing Age program. Her mission was to push the boundaries of science and elevate the standard of care for women facing chronic diseases during their childbearing years.

As a woman and mother, Marie is dedicated to advancing science in women's health. She believes that by collaborating with patients, HCPs, regulators, and advocacy groups, we can create a more inclusive and patient-centric approach to drug development and clinical care.

In addition to her UCB work, she co-chairs BRIDGE (Better Research, Information and Data Generation for Empowerment) — a global independent commission committed to advancing practical and action-oriented solutions to overcome information gaps that affect women’s health before, during, and after pregnancy.