A social impact bond: investors fund a repurposing trial, payers repay from savings

Some repurposing questions have direct payer savings attached: a generic that reduces relapse (fewer expensive second-line treatments), replaces a costly supportive drug, or allows de-escalation. The proposal is a development impact bond in which investors fund the trial, an independent evaluator verifies the result and the projected savings, and one or more payers repay investors with a return only if the trial is positive and the intervention is adopted. Outcome-based bonds have funded health interventions in India and the UK; none has funded a cancer trial.