WATERTOWN, Mass. — Disc Medicine, Inc. (NASDAQ:IRON), a clinical-stage biopharmaceutical company focused on the discovery, development, and commercialization of novel treatments for patients suffering from serious hematologic diseases, today 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.
“This study has confirmed that bitopertin significantly reduces the toxic metabolite, PPIX, in patients with EPP, and we have shown that bitopertin-treated patients experience improvements in the clinically meaningful outcomes of Patient Global Impression of Change and the number and rate of phototoxic reactions with pain, with the 60 mg dose reaching statistical significance compared to placebo. Despite the strong performance of bitopertin on the key secondary endpoint of cumulative time in light, consistent with results seen in BEACON, statistical significance was not met due to an outsized placebo response,” said John Quisel, J.D., Ph.D., President and Chief Executive Officer. “Given that, we will need to conduct an analysis of our final data set and work with investigators, regulators, and patient advocacy groups to define the optimal registrational endpoints moving forward. While we do this additional work, we continue to be excited about the upcoming readouts from our other programs, including updated data from our DISC-0974 study in anemia of myelofibrosis in Q2.”
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)
About Bitopertin
Bitopertin is an investigational, clinical-stage, orally-administered inhibitor of glycine transporter 1 (GlyT1) that is designed to modulate heme biosynthesis. GlyT1 is a membrane transporter expressed on developing red blood cells and is required to supply sufficient glycine for heme biosynthesis and support erythropoiesis. Disc is planning to develop bitopertin as a potential treatment for a range of hematologic diseases including erythropoietic porphyrias, where it has potential to be the first disease-modifying therapy. There are currently two ongoing phase 2 clinical trials of bitopertin in patients with EPP that have fully enrolled and have had key data readouts: the open-label trial called BEACON and a randomized, double-blind placebo-controlled trial called AURORA.
Bitopertin is an investigational agent and is not approved for use as a therapy in any jurisdiction worldwide. Disc obtained global rights to bitopertin under a license agreement from Roche in May 2021.
About Erythropoietic Protoporphyria (EPP) and X-linked Protoporphyria (XLP)
Erythropoietic protoporphyria (EPP) and X-linked Protoporphyria (XLP) are rare, debilitating and potentially life-threatening diseases caused by mutations that affect heme biosynthesis, resulting in the accumulation of a toxic, photoactive intermediate called protoporphyrin IX (PPIX). This causes severe reactions when patients are exposed to sunlight, characterized by excruciating pain, edema, burning sensations and potential blistering and disfigurement. PPIX also accumulates in the hepatobiliary system and can result in complications including gallstones, cholestasis, and liver damage in 20-30% of patients and in extreme cases liver failure. Current standard of care involves extreme measures to avoid sunlight, including restricting outdoor activities to nighttime, use of protective clothing and opaque shields, and pain management. This has a significant impact on the psychosocial development, quality of life, and daily activities of patients, particularly in young children and families. There is currently no cure for EPP and only one FDA-approved therapy, a surgically implanted synthetic hormone designed to stimulate melanin production called Scenesse® (afamelanotide).
About Disc Medicine
Disc Medicine is a clinical-stage biopharmaceutical company committed to discovering, developing, and commercializing novel treatments for patients who suffer from serious hematologic diseases. We are building a portfolio of innovative, potentially first-in-class therapeutic candidates that aim to address a wide spectrum of hematologic diseases by targeting fundamental biological pathways of red blood cell biology, specifically heme biosynthesis and iron homeostasis.
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