In summer 2025, a rumor spread online that chemotherapy drugs came from the chemical weapon commonly known as mustard gas.
For example, a post on X (archived) claimed chemotherapy had started in 1946 after the U.S. Department of Defense "needed to find a medical use for mustard gas":
The claim also appeared on Facebook and Reddit.
The claim is a mixture of true and false information. The first recorded chemotherapy trial on a human was conducted in 1942 (not 1946) at Yale University using a derivative of mustard gas for a specific type of cancer. However, research into chemical compounds to fight cancer had been ongoing for years. Further, nitrogen mustard was not the only compound that revealed itself to be effective.
In a 2011 lecture, a soon-to-be graduate of the Yale School of Medicine named Panos Christakis gave a lecture recounting the events, which had recently been confirmed after the chart of the cancer patient in that trial was found. He based his lecture on an article published the same year by John Fenn and Robert Udelsman, both of Yale.
Christakis said in 1919, Edward Krumbhaar, a pathologist at the University of Pennsylvania, noticed that World War I soldiers who were exposed to sulfur mustard (commonly known as mustard gas) first exhibited an increase in white blood cells in the blood ("leukocytes"), followed by a quick drop of the leukocyte count due to the destruction of the bone marrow, where white blood cells are produced. This phenomenon drew the attention of a team of researchers at Yale, who had received a contract from the U.S. Department of War (a predecessor of the Department of Defense), to study these gases and possible antidotes for them.
Yale's Alfred Gilman, a pharmacologist, and Dr. Louis Goodman, a physician and pharmacologist, had taken notice of these properties and used a derivative of sulfur mustard, nitrogen mustard (HN-3), on mice into which they had previously transplanted lymphomas — cancers of the lymph happen when white cells proliferate uncontrollably.
In 1942, a man identified only as JD had been treated at Yale for lymphosarcoma (now better known as non-Hodgkins lymphoma) and treated with surgery to excise tumors and radiation to shrink them, to no avail. Gilman and Goodman suggested that his medical team try giving him injections of nitrogen mustard to shrink the tumors.
The treatment worked. However, the toxicity of the compound also caused the patient to bleed profusely and die three months after the trial began. In the autopsy, physicians saw bone marrow had failed and fat appeared in its stead.
While HN-3 was deemed unusable for clinical purposes, another nitrogen mustard, HN-2, showed more promise and was used to treat cancer before eventually being deemed too toxic as well. Modern oncology still uses less-toxic derivatives of the mustard family of compounds for cancer treatment, however.
A 2008 article in the journal Cancer Research showed that research for cancer-treating drugs had started far earlier than the 1940s — as early as the 1900s. The two decades that followed saw an explosion of the field, with new drugs appearing from antifolates, which interfere with cell DNA by blocking folic acid, to antitumor antibiotics, which use different mechanisms to disrupt the cells' genetic material and prevent them from proliferating.