Disc Medicine Stock Plunges As Light Sensitivity Treatment Data Confounded Due To Outsized Placebo Response

On Monday, Disc Medicine Inc DISC released topline data from the AURORA Phase 2 study of bitopertin in patients with Erythropoietic Protoporphyria (EPP). 

Erythropoietic protoporphyria is a rare condition in which a toxic substance, protoporphyrin IX (PPIX), builds up in the blood. Patients experience severe reactions in the sunlight, including pain, swelling, burning sensations, and blistering.

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). 

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%.

On the key secondary endpoint of cumulative time in sunlight on days without pain, bitopertin patients had a positive response, but the endpoint did not meet statistical significance due to strong placebo performance.

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.

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.

Bitopertin treatment groups witnessed improvements in light tolerance from baseline in 20 mg and 60 mg dose cohorts. However, the results were not statistically significant relative to placebo.

There was a 75% reduction in the incidence rate of new phototoxic reactions with pain in the 60 mg dose group compared to placebo (p=0.011) and a 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.

Price Action: IRON shares are down 58.57% at $25.80 on the last check Monday.

Photo by Darko Stojanovic from Pixabay