President Donald Trump pledged in his State of the Union address in February to ‘eliminate the HIV epidemic in the United States within 10 years’. Specifics were lacking, but an important part of Trump's plan included trying to increase the use of preexposure prophylaxis (PrEP) among those at high risk for HIV infection – an estimated 1.2 million people. PrEP is a highly effective combination of two drugs, tenofovir disoproxil fumarate and emtricitabine, that can reduce the risk of HIV infection by 99% when taken daily [1]. Mathematical modeling studies suggest providing PrEP to 40% of MSM in the United States would avert 33% of expected infections [2]. In a recent Lancet study, rapid, targeted, and high-coverage rollout of PrEP among MSM in New South Wales, Australia's most populous state, resulted in a 31.5% decline in new HIV infections in 12 months [3]. But the high cost of PrEP in the United States keeps the drug out of reach for many people who need it. Currently, only about 10% of those at substantial risk for HIV are taking the drug. One sure way to increase PrEP use and reduce HIV infections would be to lower its cost. The list price of brand-name PrEP, or Truvada, is currently around $1600 for a month's supply. Bringing down the cost of PrEP could be accomplished quickly if the executive branch invoked a law that has existed since 1980 but which has never been used for the purpose of curbing unlimited price-setting for drugs developed through publicly funded research. The Bayh-Dole Act gives the government certain rights to ensure that federally supported inventions meet the needs of both the government and the public. That is, when a product has been developed using public funds, the government can ensure that the product's benefits are ‘available to the public on reasonable terms’. If a company fails to take effective steps to achieve availability on reasonable terms – for example, if it effectively bars many of the individuals who could benefit from its use by setting unreasonably high prices – then the government has ‘march-in authority’ to require the company that holds the patent to grant a license to another manufacturer. Tenofovir–emtricitabine was initially approved by the Food and Drug Administration (FDA) in 2004 to treat people already infected with HIV in combination with other antiretrovirals. The formulation quickly showed potential in preventing people from becoming infected – so much so that the National Institutes of Health (NIH) funded studies that ultimately led to the drug's approval to be used as PrEP in 2012. Some additional funding was contributed by the Bill and Melinda Gates Foundation, whereas Gilead, the maker of brand-name Truvada, contributed only drug samples [4]. In almost every other country, generic PrEP is already available and costs less than $100 per month, but patent laws keep affordable generics out of the United States. Although most insurers cover PrEP, out-of-pocket costs make the drug unaffordable even for many with insurance. Gilead offers a copay assistance program to help cover the cost of the medication, up to $7200 per year. But federal law prohibits people on Medicare from using copay assistance, and for many other healthcare plans, the expected out-of-pocket costs for Truvada far exceed this amount. Aside from the medication, additional costs are incurred from PrEP-related medical costs, such as required quarterly blood work. Although not without controversy, in mid May, Gilead announced that it would allow one generic to be introduced into the US market in 2020. Some states and counties offer resources to help those at risk get PrEP for free or at low cost, but finding clear information about eligibility and how to apply for financial assistance is often difficult. This confusion has spawned ‘PrEP navigators’ and inquiry response services run by advocates or local public health departments, which guide existing and potential PrEP users through the complicated application process for help affording the drug. This raises the question of why such a complex system is necessary, incurring enormous costs in bureaucratic overhead, in order for Americans to be able to pay for a drug that was developed using public funds and that addresses an essential public health need. The executive branch should carefully consider exercising its march-in right to grant another manufacturer the license to make and sell generic PrEP in the United States. Such a move would not only help those at risk for HIV, but could set an important precedent for the government to use its power to respond appropriately when pharmaceutical prices hinder significant public health benefit. Acknowledgements Conflicts of interest There are no conflicts of interest.