Evaluation of Tonabersat for DME

Key Inclusion Criteria

1. Adults with type 1 or 2 diabetes mellitus

2. At least one eye with:

• Best corrected E-ETDRS visual acuity letter score ≥ 74 (i.e., 20/32 or better)

• Ophthalmoscopic evidence of center-involved DME in study eye confirmed by central subfield thickness on spectral domain OCT

• Zeiss Cirrus: ≥ 290 µm in females, ≥ 305 µm in males

• Heidelberg Spectralis: ≥ 305 µm in females, ≥ 320 µm in males

• Recruitment will be monitored with a goal to have equal proportions in the following categories above the CI-DME thresholds: <75 μm, 75 μm to <175 μm, ≥175 μm

3. Media clarity, pupillary dilation, and study participant cooperation sufficient for adequate OCT

Key Exclusion Criteria

• Macular edema is considered to be due to a cause other than DME

• Major ocular surgery within prior 4 months, or anticipated after randomization

• History of focal/grid laser or other ocular surgical, intravitreal, or peribulbar treatment for DR or DME within prior 1 year, and no more than 4 anti-VEGF injections within prior 3 years

• Anticipated need to treat DME or DR during the first 6 months, or anticipated need for cataract surgery during study period

• Any history of vitrectomy

• Systemic anti-VEGF or pro-VEGF treatment within 12 months prior to randomization

• History of chronic renal failure requiring dialysis or kidney transplant

• History of moderate to severe hepatic impairment, including known liver function test (LFT) values > 3x's the upper limit of normal