Disc Medicine, Inc. presented topline data from AURORA, a phase 2 study of bitopertin in patients with EPP. Treatment with bitopertin resulted in statistically significant reductions in PPIX, the primary endpoint, and significant improvements in the rate of phototoxic reactions with pain and the Patient Global Impression of Change (PGIC). On the key secondary endpoint of cumulative time in sunlight on days without pain, bitopertin patients had a positive response consistent with BEACON results, but the endpoint did not meet statistical significance due to strong placebo performance.

The AURORA study is a randomized, double-blind, placebo-controlled phase 2 study that enrolled 75 adult subjects with EPP. Subjects were randomized 1:1:1 to receive 20 mg of bitopertin, 60 mg of bitopertin, or placebo once daily for 17 weeks. Summary of topline results: Primary endpoint: Bitopertin resulted in significant, dose-dependent, and sustained reductions in whole blood PPIX levels: -21.6% for 20 mg (p=0.003 vs placebo) and -40.7% for 60 mg (p<0.001 vs placebo); the placebo group had mean increases of +8.0%.

Secondary endpoints. Cumulative total time in sunlight between 10 am and 6 pm on days without pain observed over the 4-month treatment period: bitopertin-treated patients recorded a mean of 175.1 hours at 20 mg and 153.1 hours at 60 mg, compared with 133.9 hours for placebo; results were not statistically significant compared to placebo. The magnitude of the improvement in the bitopertin-treated patients was comparable to that observed in the BEACON study, but the benefit in the placebo arm in the AURORA trial was greater than expected.

Large improvements in light tolerance from baseline in 20 mg and 60 mg bitopertin treatment groups as measured by time to prodrome; results were not statistically significant relative to placebo. Substantial and dose-dependent reductions in phototoxic reactions with pain during the 4-month study period: 75% reduction in the incidence rate of new phototoxic reactions with pain at the 60 mg dose group compared to placebo (p=0.011); 60% reduction in the 20 mg dose group (p=0.109). Fewer bitopertin-treated patients reported a phototoxic event compared to placebo: 19% for 20 mg and 12% for 60 mg compared to 46% for placebo.

Dose-dependent improvements in PGIC, which were statistically significant for the 60 mg dose: 77% of completers at 20 mg and 86% at 60 mg (p=0.022 vs placebo) reported that their EPP was ?much better? compared with 50% for placebo. Bitopertin was generally well tolerated in both dose groups with no serious adverse events and stable hemoglobin levels.

Two patients discontinued treatment due to treatment-emergent AEs, both in the 60 mg dose group: one due to dizziness and one due to a skin rash. The most common AE reported with bitopertin treatment was dizziness: n=4 in the 20 mg dose group, n=11 in the 60 mg dose group compared with n=4 in the placebo group (median durations of 4.5, 5, and 2 days, respectively).