David Baltimore

David Baltimore (March 7, 1938 – September 6, 2025) was an American biologist, university administrator, and 1975 Nobel laureate in Physiology or Medicine. He was a professor of biology at the California Institute of Technology (Caltech), where he served as president from 1997 to 2006. He founded the Whitehead Institute and directed it from 1982 to 1990. In 2008, he served as president of the American Association for the Advancement of Science.

At age 37, Baltimore won the Nobel Prize with Renato Dulbecco and Howard M. Temin "for their discoveries concerning the interaction between tumour viruses and the genetic material of the cell", specifically the discovery of the enzyme reverse transcriptase. He contributed to immunology, virology, cancer research, biotechnology, and recombinant DNA research. He also trained many doctoral students and postdoctoral fellows, several of whom have gone on to notable and distinguished research careers. In addition to the Nobel Prize, he received a number of other awards, including the U.S. National Medal of Science in 1999 and the Lasker Award in 2021.

Baltimore was born on March 7, 1938, in Manhattan, New York, to Gertrude (Lipschitz) and Richard Baltimore. Raised in the Queens neighborhoods of Forest Hills and Rego Park, he moved with his family to suburban Great Neck, New York, while he was in second grade because his mother felt that the city schools were inadequate. His father had been raised as an Orthodox Jew and his mother was an atheist, and Baltimore observed Jewish holidays and would attend synagogue with his father through his Bar Mitzvah. He graduated from Great Neck North High School in 1956, and credits his interest in biology to a high-school summer spent at the Jackson Laboratory's Summer Student Program in Bar Harbor, Maine. It was at this program that he met Howard Temin, with whom he would later share the Nobel Prize.

Baltimore earned his bachelor's degree in chemistry with high honors at Swarthmore College in 1960. He was introduced to molecular biology by George Streisinger, under whose mentorship he worked for a summer at Cold Spring Harbor Laboratory as part of the inaugural cohort of the Undergraduate Research Program in 1959. There he also met two new MIT faculty, future Nobel Laureate Salvador Luria and Cyrus Levinthal, who were scouting for candidates for a new program of graduate education in molecular biology.

Luria and Levinthal invited Baltimore to apply to the Massachusetts Institute of Technology (MIT). Baltimore's future promise was evident in his work as a graduate student when he entered MIT's graduate program in biology in 1960. His early interest in phage genetics quickly yielded to a passion for animal viruses. He took the Cold Spring Harbor course on animal virology in 1961 and chose to move to Richard Franklin's lab at Rockefeller University to complete his PhD research on animal virology. There he made fundamental discoveries on virus replication and its effect on cell metabolism, including the first description of an RNA replicase, finishing his PhD in only two years.

After his PhD, Baltimore returned to MIT for postdoctoral research with James E. Darnell in 1963. He continued his work on virus replication using poliovirus and pursued training in enzymology with Jerard Hurwitz at Albert Einstein College of Medicine in 1964.

In February 1965, Baltimore was recruited by Renato Dulbecco to the newly established Salk Institute for Biological Studies in La Jolla as an independent research associate. There he investigated poliovirus RNA replication and began a long and storied career of mentoring other scientists' early careers including Marc Girard, and Michael Jacobson. They discovered the mechanism of proteolytic cleavage of viral polyprotein precursors, pointing to the importance of proteolytic processing in the synthesis of eukaryotic proteins. He also met his future wife, Alice Huang, who began working with Baltimore at Salk in 1967. He and Alice together carried out key experiments on defective interfering particles and viral pseudo types. During this work, he made a key discovery that polio produced its viral proteins as a single large polyprotein that was subsequently processed into individual functional peptides.

In 1968, he was recruited once more by soon-to-be Nobel laureate Salvador Luria to the department of biology at MIT as an associate professor of microbiology. Alice S. Huang also moved to MIT to continue her research on vesicular stomatitis virus (VSV). They became a couple, and married in October 1968. At MIT, Huang, Baltimore, and graduate student Martha Stampfer discovered that VSV replication involved an RNA-dependent RNA polymerase within the virus particle, and used a novel strategy to replicate its RNA genome. VSV entered a host cell as a single negative strand of RNA, but brought with it RNA polymerase to stimulate the processes of transcription and replication of more RNA.

Baltimore extended this work and examined two RNA tumor viruses, Rauscher murine leukemia virus and Rous sarcoma virus. He went on to discover reverse transcriptase (RTase or RT) – the enzyme that polymerizes DNA from an RNA template. In doing so, he discovered a distinct class of viruses, later called retroviruses, that use an RNA template to catalyze synthesis of viral DNA. This overturned the simplified version of the central dogma of molecular biology that stated that genetic information flows unidirectionally from DNA to RNA to proteins. Reverse transcriptase is essential for the reproduction of retroviruses, allowing such viruses to turn viral RNA strands into viral DNA strands. The viruses that fall into this category include HIV.

The discovery of reverse transcriptase, made contemporaneously with Howard Temin, who had proposed the provirus hypothesis, showed that genetic information could traffic bidirectionally between DNA and RNA. They published these findings in back-to-back papers in the journal Nature. This discovery made it easier to isolate and reproduce individual genes, and was heralded as evidence that molecular and virological approaches to understanding cancer would yield new cancer treatments. This may have influenced President Richard Nixon's war on cancer, which was launched in 1971 and substantially increased research funding for the disease. In 1972, at the age of 34, Baltimore was awarded tenure as a professor of biology at MIT, a post that he held until 1997.

Baltimore married Alice S. Huang in 1968. They had one daughter. Baltimore was an avid fly-fisher.

Baltimore died from cancer at his home in Woods Hole, Massachusetts, on September 6, 2025, at the age of 87.

1971 First recipient of the Gustav Stern Award in Virology

1971 Eli Lilly Award in Immunology and Microbiology

1974 Fellow of the American Academy of Arts and Sciences

1975 Nobel Prize in Physiology or Medicine

1986 Golden Plate Award of the American Academy of Achievement

Luria, S. E., J.E. Darnell, D. Baltimore and A. Campbell (1978) General Virology 3rd edition John Wiley and Sons, New York, New York.

Darnell, J., H. Lodish and D. Baltimore (1986) Molecular Cell Biology, Scientific American, New York, New York.