Disc Medicine has finalized the design of the confirmatory trial for its rare blood disorder drug candidate, adding a co-primary endpoint at the request of the FDA to clear the path to accelerated approval.
The biotech plans to file for accelerated approval of bitopertin in erythropoietic protoporphyria (EPP), a rare genetic disorder that causes photosensitivity, in the second half of the year. Disc committed to the plan after agreeing to the use of protoporphyrin IX (PPIX) reduction as the surrogate endpoint with the FDA last year.
Talks with the agency spurred a change in the design of the study Disc plans to run to confirm the effect of bitopertin in EPP. Previously, Disc said the FDA agreed that it can use average monthly time in sunlight without pain at the end of a six-month treatment period as a primary endpoint. That agreement remains in place, Disc said, but is now joined by agency support for the use of a co-primary endpoint.
The additional primary endpoint is looking at changes from baseline in whole blood metal-free PPIX after six months of treatment. Will Savage, M.D., Ph.D., chief medical officer at Disc, discussed the choice of co-primary endpoint, which is the same measure the biotech is using to seek accelerated approval, on a conference call with investors Tuesday.
“The elevation of this endpoint to co-primary is an indication that regulators understand the importance of the role of PPIX,” Savage said. “It is highly objective and we are optimistic that we can meet this endpoint, so we feel that it strengthens the design of the confirmatory trial favorably.”
Disc needs to hit both primary endpoints. The biotech said enrollment in the 150-patient study will be well underway by the time the FDA needs to make a decision on accelerated approval.