Spark Therapeutics will receive the option to exclusively license a defined number of synthetic promoters emerging from the collaboration for use in developing gene therapy products in specified indications. Upon option exercise, Spark Therapeutics will be responsible for conducting preclinical, clinical and commercialization activities for any gene therapy candidates that incorporate Senti Bio's licensed synthetic promoters. Senti Bio will receive an upfront payment as well as funding to support its research activities, and upon option exercise will be eligible to receive an option exercise payment as well as development, regulatory and sales milestone payments in addition to royalties on a per product basis. The aggregate potential value of upfront, opt-in and milestone payments to Senti Bio may exceed $645 million.