OBJECTIVES: Repurposing generic drugs offers a quick and accessible route to deliver new treatments to rare diseases patients, however, there is limited research into its extent and associated economic benefits. A two-stage Pragmatic Literature Review (PLR) was carried out to identify examples of, and economic data relating to, repurposed drugs in rare diseases.

METHODS: Stage 1 identified reports of drugs repurposed in rare diseases through database searches in MEDLINE and Embase, conference and website searches. Stage 1 results informed targeted searches for economic data in Stage 2. Due to the large number of repurposed drugs identified, priority was given to diseases of interest and study type, with case reports de-prioritised.

RESULTS: In Stage 1, 167 rare disease/repurposed drug combinations were identified. This included 93 drugs, repurposed from a range of original indications including erectile dysfunction and cancer therapies, being used in 30 rare diseases. Stage 2 identified 26 publications reporting economic information for 4 rare diseases and their respective repurposed drugs (pulmonary arterial hypertension [PAH] and sildenafil, idiopathic pulmonary fibrosis [IPF] and pirfenidone, alkaptonuria and nitisinone, sickle cell anaemia and hydroxyurea). Nine records described sildenafil in PAH, the majority (7/9) reporting sildenafil to be more cost-effective than comparators. Fourteen records reported the use of pirfenidone in IPF, half reported Quality-Adjusted Life Years (QALYs) or incremental QALYs, for pirfenidone and comparators. Incremental QALYs for pirfenidone versus nintedanib ranged from -0.67 to 1.04 (mean 0.073), and versus best supportive care from 0.31 to 1.95 (mean 0.66).

CONCLUSIONS: Given the substantial number of generic drugs repurposed for rare diseases and the potential for cost effective treatment through the use of low-cost generics, only a very small number of publications examined the associated economic outcomes. There is considerable variation in the economic outcomes reported for PAH and IPF, indicating that further research is required.