Advance market commitments (AMCs) are gaining increasing attention as an alternative science funding mechanism to promote innovation in medicine. In this paper, we first review the theory underlying AMCs, before analyzing two case studies of prior AMCs: the Gavi, the Vaccine Alliance pneumococcal conjugate vaccine AMC launched in 2007 and the use of AMC-like mechanisms in Operation Warp Speed in the US. We identify the empirical successes and limitations of AMCs in promoting research and development into new therapeutics and vaccine candidates, highlighting both the strong promise of AMCs and the need to complement them with other science funding mechanisms to promote innovation. We conclude with a series of recommendations to inform science policymakers.