This randomized clinical trial will evaluate the effect of tonabersat compared with placebo on central subfield thickness (CST) in eyes with center-involved diabetic macular edema (CI-DME) and good visual acuity.



Eligible Ages
Over 18 Years
Eligible Genders
Accepts Healthy Volunteers

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

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

Study Design

Phase 2
Study Type
Intervention Model
Parallel Assignment
Intervention Model Description
Randomized, double-masked, placebo-controlled clinical trial
Primary Purpose
Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)

Arm Groups

ArmDescriptionAssigned Intervention
Placebo Comparator
  • Other: Placebo
    Two pills of Study Drug (placebo) is taken orally once daily. It is recommended the Study Drug be taken at bedtime. The first dose (two pills) will be taken at bedtime on the day the participant is randomized.
Active Comparator
Tonabersat (80 mg)
  • Drug: Tonabersat
    Two pills of Study Drug (80 mg tonabersat) is taken orally once daily. It is recommended the Study Drug be taken at bedtime. The first dose (two pills) will be taken at bedtime on the day the participant is randomized.

Recruiting Locations

Boston Medical Center Corporation
Boston, Massachusetts 02118
Steven D. Ness, MD

More Details

Jaeb Center for Health Research

Study Contact

Cynthia Stockdale, MSPH

Detailed Description

The primary objective is to assess the effects of tonabersat, an orally administered Connexin43 hemichannel inhibitor, on central subfield thickness (mean change) compared with placebo in eyes with CI-DME and good visual acuity at 6 months. Exploratory objectives will evaluate biomarkers of kidney function for potential benefit. Furthermore, this phase 2 study is being conducted to determine whether the conduct of a phase 3 trial has merit and provide information on outcome measures needed to design a phase 3 trial.


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.