This is a randomized, active comparator-controlled, open-label, parallel-group, 2-part study. Parts 1 and 2 will be conducted in the same subjects.~Part 1 of the study is designed to evaluate the efficacy, safety, and tolerability of oral BCX9930 monotherapy for 24 weeks versus continuing C5 inhibitor therapy in subjects with PNH with inadequate response to their current C5 inhibitor therapy. Subjects will be randomized to either discontinue C5 inhibitor therapy and start BCX9930 monotherapy or to continue C5 inhibitor therapy for the 24-week randomized treatment period. The primary efficacy and safety analyses will be based on Part 1.~Part 2 of the study is designed to evaluate the long-term safety, tolerability, and effectiveness of BCX9930 monotherapy when administered through Week 52. All subjects in Part 2 will receive BCX9930. Subjects who are randomized to BCX9930 monotherapy in Part 1 will continue to receive BCX9930 in Part 2. Subjects who are randomized to C5 inhibitor therapy in Part 1 will discontinue that therapy at the Week 24 visit and receive BCX9930 in Part 2.
The purpose of this study is to determine the efficacy and safety of BCX9930 monotherapy for the treatment of PNH compared to continued C5 inhibitor therapy in adult PNH patients with residual anemia despite treatment with a C5 inhibitor.