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David Baltimore, President Emeritus and the Judge Shirley Hufstedler Professor of Biology, Emeritus, at Caltech and a co-awardee of the 1975 Nobel Prize in Physiology or Medicine, departed on September 6, 2025. He was 87 years old.

Baltimore navigated a diverse career and existence as a globally impactful scientist, leader in academia and public policy, and a committed mentor, colleague, friend, father, and husband.

“David Baltimore’s impact as a virologist, uncovering essential mechanisms and applying those discoveries to immunology, cancer, and AIDS, has revolutionized biology and medicine,” remarks Caltech President Thomas F. Rosenbaum, the Sonja and William Davidow Presidential Chair and physics professor. “David’s significant impact as a mentor to countless students and postdocs, his generosity as a colleague, his guidance of prominent scientific institutions, and his active participation in global initiatives to outline ethical limits for biological advancements characterize an extraordinary intellectual journey.”

Baltimore received the Nobel Prize for his landmark discovery that the genetic material of tumor viruses could synthesize DNA from their RNA genomes, altering the long-standing belief that genetic information could only flow in one direction, from DNA to RNA. His research enhanced the understanding of the molecular mechanisms underpinning the immune response and influenced progress in biotechnology as well as the formulation of national science policies regarding recombinant DNA studies and the AIDS crisis.

More recently, he concentrated on exploring the development and function of the mammalian immune system and on creating viral vectors capable of delivering genes into cells to broaden the spectrum of diseases (from cancer to HIV to influenza) the body can effectively combat.

In addition to his scientific achievements, Baltimore was a distinguished leader in higher education and an advocate for science policy. He served as Caltech’s seventh president from 1997 to 2006, a period marked by the successful completion of a fundraising effort for the biological sciences, the establishment of the Broad Center for the Biological Sciences, and the initiation of a $1.4 billion capital fundraising campaign. His presidency also saw numerous successful space and planetary missions at the Jet Propulsion Laboratory, managed by Caltech for NASA, notably the Mars Exploration Rovers.

“David infused Caltech with scientific distinction and an ambitious vision for the future that he was uniquely positioned to actualize,” states David W. Thompson (MS ’78), chair of the Caltech Board of Trustees. “He enhanced the Institute’s global reputation through his ability to connect with varied audiences and successfully managed two impactful fundraising campaigns that pushed research across disciplines, improved education, and transformed the campus’s landscape. His legacy will resonate through our halls for generations.”

As president, Baltimore aimed to enhance diversity at Caltech, particularly by encouraging more women into administrative positions and, with a focus on improving undergraduate life quality, appointed the first full-time vice president for student affairs and initiated a $3 million fund to support student-life activities and services.

“During my tenure in the president’s office, I endeavored to maintain Caltech as the distinctive and highly effective institution envisioned by George Ellery Hale nearly 100 years ago,” Baltimore indicated in a note to campus upon announcing his retirement in 2005. “Its commitment to excellence has remained unwavering, necessitating that it continually evolves, striving for the shifting frontiers of knowledge.”

Baltimore’s personal sentiments are reflected in the memories and insights of colleagues who recounted his unquenchable curiosity and quest for new knowledge, knack for identifying and nurturing brilliance, and a profound and personal dedication to the individuals he surrounded himself with and the institutions to which he devoted his efforts.

“Reflecting on the numerous chapters of David’s scientific journey starting as an undergraduate at Swarthmore, through his time at MIT, the Salk, and Rockefeller, and ultimately at Caltech, the prevailing aspiration was a rigorous pursuit of what is novel, true, and fundamental—in his own research and that of others. Mostly, he succeeded, and when he did not, he always learned,” remarks Barbara Wold (PhD ’78), Caltech’s Bren Professor of Molecular Biology and Merkin Institute Professor. “At Caltech, both as our president and as a professor in the biology and biological engineering division, he often perceived in people potential they did not recognize in themselves.”

Paul Sternberg, Bren Professor of Biology and the William K. Bowes Jr. Leadership Chair of the Division of Biology and Biological Engineering, adds, “From a personal standpoint, I knew David from my graduate years at MIT and then for several decades at Caltech. What stands out the most to me was his constant readiness to share his wisdom and refined intellectual insight. There are countless scientists who have benefited from his mentorship.”

Baltimore commenced his PhD in 1960 at MIT, concentrating on studying bacteriophages, viruses that infect and reproduce within bacteria. However, after attending a summer course on animal virology at Cold Spring Harbor Laboratory, he shifted to The Rockefeller University to collaborate with Richard Franklin, a trailblazer in the molecular biology of animal viruses.

By 1970, after several years studying the replication of RNA viruses such as polio- and mengoviruses, which create RNA replicas of their RNA genomes for replication, Baltimore began to explore whether another category of RNA viruses, retroviruses, contained an enzyme that generates a DNA copy of the viral RNA. To validate this, he conducted an experiment to reveal the existence of this viral enzyme, reverse transcriptase, so designated because it reversed the then-prevalent notion of genetic information flow (DNA to RNA to protein). This experiment would serve as the foundation for the Nobel Prize in Physiology or Medicine he received in 1975 alongside former Caltech faculty member Renato Dulbecco and Howard Temin (PhD ’60), who completed his PhD studies in Dulbecco’s lab.

“The experiment exemplifies elegance and simplicity,” states Baltimore’s Caltech colleague Carlos Lois, research professor of biology. “In one fell swoop, David demonstrated that genetic information can flow from RNA to DNA, a phenomenon deemed impossible for over two decades. It is a testament to David’s ingenuity that he had never previously worked with retroviruses! For this experiment, he requested purified retroviral particles from a core facility at the National Institutes of Health. The viruses were mailed to him, and he executed the experiment. Thus, the first time he worked with retroviruses, he conducted an experiment that earned him a Nobel Prize.”

The discovery of reverse transcriptase enabled laboratories around the globe to investigate the molecular biology of retroviruses. When the AIDS epidemic emerged in the early 1980s, the scientific community quickly identified HIV—a retrovirus—as its causative agent. Moreover, the biotechnology revolution of the early 1980s was a direct result of leveraging reverse transcriptase to clone and manipulate genes.

After the revelation of reverse transcriptase, Baltimore continued to engage with
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Retroviruses for numerous years prior to shifting his attention to immunology. His laboratory was the first to identify one of the principal regulators of inflammatory mechanisms: a protein known as NFkappaB, the misregulation of which is associated with various forms of autoimmune disorders and malignancies. Furthermore, his students uncovered the genes linked to the creation of antibody diversity, enabling scientists to grasp at the molecular scale how an animal’s genome can produce billions of unique antibodies.

“Over the course of his career, David exhibited a rare quality among researchers: intellectual flexibility,” Lois states. “Whenever he felt there were crucial inquiries that were primed for exploration, he dove into the field, even if he had never ventured into that area previously.”

Lois was a postdoctoral scholar in Baltimore’s laboratory at Caltech from 1996 to 2002. “Becoming a part of his lab was a profoundly influential experience,” Lois reflects. “During lab meetings, you could, on the same afternoon, learn about the implications of an oncogene, memory cells in the immune system, genetic rearrangements, the architecture of a protein domain, the management of DNA damage repair, or the signaling cascades involved in cell demise. Each lab meeting was an opportunity to acquire fresh knowledge from individuals leading research on the subject. I have never encountered, before or after, a collective of individuals more passionate and driven toward scientific inquiry. The ambiance in the lab was exhilarating, and it was incredibly motivating to be surrounded by such intellectually ambitious individuals.”

Following his retirement from the presidency of Caltech in 2006, Baltimore stayed at the Institute to persist in his teaching and research endeavors. Among other projects, Baltimore developed a new approach to combat cancer, created a highly effective gene therapy to block HIV from infecting individual cells in the immune system, and devised a new method for generating transgenic mice. He also collaborated with others in a worldwide initiative to develop an HIV vaccine. In 2005, he received a $13.9 million grant from the Grand Challenges in Global Health initiative at the Bill & Melinda Gates Foundation for his strategy to “engineer immunity” against HIV and other chronic disease pathogens.

“David Baltimore will be remembered in history not only as an exceptional scientist but also as one of the outstanding presidents of Caltech,” remarked entrepreneur, philanthropist, and former Caltech trustee Eli Broad when Baltimore’s retirement was announced. “It is uncommon to find someone of his intellect, integrity, and leadership who can engage so effectively with people both inside and outside the realm of science.”

Baltimore was involved in public policy throughout his career. In the 1970s, he played a significant role in influencing national science policy pertaining to recombinant DNA research, serving as the co-organizer of the Asilomar Conference on Recombinant DNA in 1975, and he was an early champion for federal AIDS research. In 1986, he co-chaired the National Academy of Sciences committee on a National Strategy for AIDS, and in 1996, he was appointed to lead the National Institutes of Health (NIH) AIDS Vaccine Research Committee, which became known as “the Baltimore Committee” and is now an NIH subcommittee. He collaborated with the NIH while serving as director of the Whitehead Institute at MIT, assisting the government in formulating guidelines for the Human Genome Project.

After the 2000 presidential election, Baltimore established the Caltech/MIT Voting Technology Project alongside MIT President Charles Vest. The team consisted of political scientists, economists, and engineers aimed at addressing challenges within the electoral process. The group provided testimony to Congress, leading to the enactment of the Help America Vote Act in 2002.

In 2015, he was part of a distinguished group of scientists who called for a global moratorium on the use of genome-editing methods to modify inheritable human DNA; in 2018, he chaired the organizing committee for the second such summit.

“It’s part of my general belief that contemporary medicine will have the capability to alleviate much of the burden of the diseases that still afflict us as humans, like cancer, genetic disorders, and heart disease,” Baltimore stated in an interview following the 2018 summit. “I am optimistic that we will ameliorate these issues and that the world will become, in that regard, a better place because of modern biology.”

Baltimore was born on March 7, 1938, in New York City. He earned his BA in chemistry with high honors from Swarthmore College in 1960 and his PhD in biology from The Rockefeller University in 1964. He joined MIT as an associate professor in 1968, ascended to a full professorship in 1972, and was appointed American Cancer Society Research Professor in 1973. In 1974, he became part of the staff at the MIT Center for Cancer Research and was a founding director of the Whitehead Institute in 1982, leading it until 1990. He served as president of Rockefeller from 1990 to 1991 and was a member of the Rockefeller faculty until 1994, when he returned to the MIT faculty until he took on the presidency of Caltech in October of 1997.

Among other accolades and distinctions, Baltimore was honored with the National Medal of Science (1999), the National Academy of Sciences Award in Molecular Biology (1974), the Warren Alpert Foundation Prize (2000), the Eli Lilly and Co. Award in Microbiology and Immunology (1971), the Gustav Stern Award in Virology (1970), and the Lasker~Koshland Special Achievement Award in Medical Science (2021).

He was a member of the National Academy of Sciences and the National Academy of Medicine and was a fellow of the American Academy of Arts and Sciences and the American Institute of Immunologists, becoming a Distinguished Fellow in 2019; in addition, he was a foreign member of the Royal Society of London and the French Academy of Sciences. From 2007 to 2008, he held the position of president and chair of the American Association for the Advancement of Science. He received honorary doctorates in science from Mount Sinai Medical Center, the University of Helsinki, Cold Spring Harbor Laboratory, Columbia University, Yale University, The Rockefeller University, Harvard University, the University of Alabama, California Polytechnic State University, the Weizmann Institute of Science, Swarthmore College, Bard College, and Mount Holyoke College.

In 2006, in tribute to his mother, Baltimore established the Gertrude Baltimore Chair in Experimental Psychology. In 2017, the Eli and Edythe Broad Foundation founded the David Baltimore Professorship in Biology and Biological Engineering at Caltech, a title presently held by Pamela Bjorkman.

“David was magnanimous,” comments Elliot Meyerowitz, the George W. Beadle Professor of Biology and Howard Hughes Medical Institute Investigator. “His comprehension of biology was profound, and he shared it generously, along with his experience, insights, and time. His background was extensive not only in science but also as a leader and builder of universities, companies, and laboratories, including his remarkably successful tenure as president of Caltech. He was always willing to provide counsel when solicited. David was remarkably generous with his time, consistently pausing to converse, advise, and impart his knowledge—not just scientific but also about the latest dining spots, books, and concerts he enjoyed—despite being busier than most could fathom. David and Alice were gracious and inspiring hosts, both at Caltech and in their home in Pasadena. He will be profoundly missed by all of us.”

Thomas Palfrey, the Flintridge Foundation Professor of Economics and Political Science, Emeritus, who initially encountered Baltimore during the presidential search and subsequently collaborated closely with him as Caltech’s lead in the Caltech/MIT Voting Technology Project, sustained a long-standing friendship with Baltimore over the years. “One thing is clear: he was a brilliant scientist—one of the foremost scientists of his generation, a university leader, and significant in public service. Everyone is aware of that,” Palfrey remarks. “Yet what they may not realize is the breadth and depth of his interests: music, both classical and jazz, art, fine wine, and exceptional cuisine. He led a richly diverse life, one of those individuals who pressed on the accelerator and never eased up throughout his entire life. The quantity of pursuits he embraced—traveling for both pleasure and work—was astonishing. I think it’s essential to recognize that he engaged in a myriad of activities as a person as well as a scientist. He was concerned about his friends and the global community. Much of his work aimed at enhancing the human condition. He should be commemorated for that.”

Baltimore is survived by Alice Huang, a senior faculty associate in biology at Caltech and his spouse of 56 years, along with their daughter, TK Baltimore.

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