Presentation (CTI)

OBJECTIVES: Many gene therapies for rare conditions fail to secure investment-funds to support clinical trials (phase I/II/III) providing evidence to understand patient benefits and harms. Social impact bonds have the potential to appeal to private investors to finance clinical trials, with a rate of return on investment (ROI) that reflects developmental risks. This study aimed estimate a viable ROI for social impact bonds to finance research and development costs of exemplar gene therapies.
METHODS: A viable ROI was derived from a model-based evaluation to establish when the expected value of future repayments was worthwhile. The investment was assumed to cover development costs of a gene therapy from Phase I/II to the completion of Phase III. A decision tree depicted the consequent repayments (£; 2024 price-year) after failure/success at any phase. Three different repayment terms were evaluated: (1) base-case (repay unused investment at trial failure); (2) best-case (base-case plus 75% repayment guarantee for failure at Phase III); (3) worst-case (no repayment of unused investment at failure). One-way and probabilistic sensitivity analyses investigated the key development risks influencing the estimated ROI.
RESULTS: The estimated viable ROI for the base-case, best-case, and worst-case scenarios were 328%, 296%, and 482% of the investment, respectively. The one-way sensitivity analyses showed the key driver of the estimated ROI was the assumed probability of trial success; gene therapy trials with a lower probability of success had a higher estimated viable ROI for investors to reflect greater development risk. Probabilistic sensitivity analysis showed that securing repayment terms reduced the variance in the expected ROI.
CONCLUSIONS: Social impact bonds can be designed with a viable rate of return, informed the likelihood of sequential trial success rates, to support research and development costs of emerging gene therapies indicated for rare conditions.