An Orchestra of Science: How Sophie Zaaijer, PhD, Is Advancing Precision Medicine

You never know where you might find Sophie Zaaijer, PhD. She might be collaborating with clinicians in a lab at UC Irvine, where, in September 2025, she joined the Division of Hematology and Oncology as a research specialist advancing precision medicine.

She’s also a researcher at UC Riverside, so you could find her there as well. She recently collaborated with her UCR colleague Simon C. Groen on a study of clinical trials used to approve new drugs in the U.S., finding that only 6% reflected the country’s racial and ethnic makeup.

Later this month, Zaaijer will be in San Diego at the inaugural Health Executive and Research Summit (HERS), moderating a panel on ways to redesign clinical trials to better serve women’s health.

Or, you could catch her in Hollywood as scientific advisor for the series Orphan Black, and, believe it or not, you might spot Zaaijer playing the viola in a music video for a rock band!

In addition to her work as a scientist, Zaaijer has toured the world as a violist. In fact, her background in music informs her research to make clinical trials more representative and to advance precision medicine.

Blending Music & Science

Zaaijer started playing the violin at age 5 but switched to the viola, her “true love,” when she was 14. Soon after, she was accepted into the Dutch National Youth Orchestra and toured internationally, performing in Japan, Italy, Germany and Spain.

“For many years, I maintained dual academic tracks, balancing music with molecular biology and genetics,” says Zaaijer, who pursued BSc majors in both conservatory and scientific studies before later earning a PhD in molecular biology and genetics. She has prioritized her scientific work in recent years, but music remains a strong influence.

“Music taught me discipline, creativity, resilience, problem-solving, collaboration and the importance of listening — skills that are just as essential in translational research as they are in chamber music,” she says. “I still occasionally perform with professional orchestras, and I appeared in a [not yet released] music video for the Hollywood rock band Vampire Time!”

She also stresses how excellence in music is both individual and collective. “In an orchestra, you must master your individual part with precision, but the performance only succeeds if you listen carefully and blend seamlessly with others,” she says. “That principle — rigor paired with deep listening — has shaped how I approach science.”

That approach has led her to explore clinical trials and, in turn, expose critical gaps when it comes to advancing precision medicine.

Gaps in Precision Medicine

“Precision medicine is not theoretical; it is transforming outcomes today,” says Zaaijer. For example, mutations in tumor DNA can inform whether or not a particular cancer treatment will work for a patient.

In the clinic, the genitourinary (GU) team at UC Irvine — including Arash Rezazadeh Kalebasty, MD, a medical oncologist collaborating with Zaaijer — uses this approach daily to inform clinical decision-making, with growing evidence from global clinical trials demonstrating major benefits for treatment efficacy, timing of intervention and predicting disease progression or recurrence.

However, as shown in Zaaijer’s study with Groen, many current therapies are built using datasets that do not adequately represent the full diversity of the human population. “Because of this,” she explains, “we may miss DNA variants that could serve as new targets for treatment to help even more patients.”

Their findings, published in Communications Medicine, highlight shortcomings in trial cohort representativeness, particularly for Black and Hispanic individuals.

“If certain populations are underrepresented in clinical trials, we narrow the genetic variation we study,” explains Zaaijer. “During clinical trials, this can affect accurate risk prediction, drug efficacy and toxicity profiles.” A therapy that appears highly effective and safe in a trial population might produce unanticipated adverse effects when used more broadly if the genetic background of those patients were not represented in the evidence base.

“Consideration of ancestral background is an important stepping stone in the process of improving precision drug discovery and treatment,” says Zaaijer. “Understanding biomedical diversity advances biomedicine for everybody.”

Biomedicine for All

Addressing ancestral inclusion requires understanding the international nature of drug development, which is why Zaaijer advises alignment with the International Council for Harmonization. The ICH determines how readily accepted trial data is across regulatory regions.

“Because the U.S. includes one of the largest populations of individuals of African descent within an ICH-aligned framework, increased U.S.-based trials can improve representation,” says Zaaijer, adding that Brazil and Argentina are now ICH regulatory members as well. “As these countries are increasingly incorporated into global clinical trials, this may meaningfully expand Hispanic representation in international studies.”

Similar to ancestral differences, it is also critical to consider biological sex differences. “Although policy changes since 1993 have improved the inclusion of women in clinical trials, important gaps remain,” she says. “How well are we designing trials to truly capture female and male physiology over time? Are we adequately accounting for hormonal status and its dynamic changes when evaluating drug efficacy and safety?”

Zaaijer was excited to see a session at the recent American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium with four talks focused on sex differences in bladder cancer. Although bladder cancer is less common in women, women tend to have worse progression and survival once they develop the disease. “Understanding why means studying the biology in both sexes — what drives the higher incidence in men, and what shapes outcomes in women,” says Zaaijer. “Improving outcomes for women also deepens our understanding of the disease in men, so it’s a scientific win-win.”

Zaaijer will tackle this topic further as a moderator for the panel, “Why Counting Women Isn’t Enough: Rethinking Clinical Trials to Serve Women’s Health,” which takes place on March 24, 2026, the second day of the HERS “Women’s Health: Drug Discovery to Novel Therapies” program.

Clinical Collaborations

As Zaaijer continues to explore questions around clinical trials, she is pleased to be at the UC Irvine School of Medicine, collaborating with Rezazadeh. “First and foremost, biomedical excellence and active engagement in cutting-edge clinical research drew me to UC Irvine and his clinic,” she says.

UC Irvine also resonated with her commitment to inclusion and diversity, which extends beyond her research and into the workplace. “Since I have been at UC Irvine, I’ve had the honor of interacting with many leaders in medicine, including Sheetal Desai, MD, Nataliya Mar, MD, Jennifer Valerin, MD, Shera Feinstein, MD, and Catherine Coombs, MD, and many more,” she says. “They are exceptional women physicians and scholars, deeply dedicated to advancing science while delivering compassionate, highest-quality care. Their drive shows me what is possible and inspires me to raise my own bar.”

One project Zaaijer is working on stems directly from an unusual clinical observation Rezazadeh made in his clinic. “A patient undergoing androgen deprivation therapy (ADT) developed thymic regrowth and remained in remission,” she says. “Because the thymus is central to T-cell development and typically regresses in adulthood under the influence of testosterone, this case raises an important question — could androgen suppression enable thymic reactivation and enhance anti-tumor immunity?” She is investigating this alongside Arti Gupta, MD, and Akash Joshi, MD, in radiology; Sudhir Gupta, MD, PhD, in immunology; and Farah Rahmatpanah, PhD, in pathology.

In parallel, Zaaijer is collaborating with Xiaolin Zi, PhD, and Liankun Song, PhD, to study therapeutic resistance in prostate cancer. “Despite major advances…resistance ultimately emerges in many patients,” she says. “Our goal is to identify the molecular mechanisms driving this resistance by integrating longitudinal clinical samples with functional laboratory models.”

In this translational collaboration, the UCI Biobank is vital. “This unique clinic-to-bench infrastructure — founded by Maheswari Senthil, MD — provides a seamless pipeline for acquiring and leveraging patient samples, enabling research questions that would otherwise be difficult to address at scale,” she says.

“UC Irvine fosters a culture where disciplines converge and new ideas take shape, and where all clinicians and scientists thrive — not only as individuals, but as part of a collaborative and mission-driven community,” says Zaaijer, again echoing parallels with her orchestral experience. “As a basic scientist, entwined within the clinical space, I’m able to work on powerful projects that otherwise would be difficult to pull together.”

— Shani Murray