This bill, titled the "Old Drugs, New Cures Act," amends the Social Security Act to prevent certain priority research drugs from being treated as line extensions for manufacturer rebate calculations under Medicare and Medicaid, aiming to reduce financial obligations for drug manufacturers developing new uses for existing medications. The legislation establishes a process for the Secretary to designate a drug as a priority research drug if it meets specific criteria. These include being approved for at least 10 years and currently under investigation for a new indication that addresses a significant unmet medical need without an existing alternative. Additionally, the new indication must target a disease or condition with a high prevalence among beneficiaries of Federal health care programs , meaning at least 33 percent of claims are paid by programs such as Medicaid, Medicare Part D (for low-income individuals), 340B, or VA. By excluding these designated drugs from line extension definitions and related special rules, the bill modifies how manufacturer rebates are determined, thereby incentivizing pharmaceutical companies to invest in repurposing older drugs for new therapeutic uses, especially for conditions prevalent within federal healthcare programs.