Medicine can affect women differently than men, but rarely are sex and gender considered in the development of drugs. There’s now a movement, including in Switzerland, to change this. In July 2023 lecanemab, sold under the brand name Leqembi, became the first drug in 20 years to be fully approved by the United States Food and Drug Administration (FDA) for Alzheimer’s disease. The drug, which was developed by US firm Biogen and Japanese firm Eisai, works by reducing amyloid plaques that form in the brain, a defining feature of the memory-robbing illness that affects some 55 million people globally. The pivotal study for approval of the drug showed that it slowed cognitive decline by 27% compared to a placebo. But the supplementary appendix told a more complex story. It revealed differences among the 1,700 patients in the study, some 51.7% of whom were women. The drug slowed cognitive decline by only 12% in women compared to 43% in men. These results are difficult to interpret ...