A Study to Evaluate the Efficacy, Durability, and Safety of KSI-301 Compared to Aflibercept in Participants With Diabetic Macular Edema (DME)

Inclusion Criteria: 1. Signed informed consent prior to participation in the study. 2. Treatment-naïve diabetic macular edema, with vision loss and center involvement (if present) diagnosed within 9 months of screening. 3. BCVA ETDRS letter score between 78 and 25 (-20/25 to 20/320 Snellen equivalent), inclusive, in the Study Eye. 4. CST of ≥ 320 microns on SD-OCT (Heidelberg Spectralis or equivalent on other OCT instruments) as determined by the Reading Center. 5. Decrease in vision determined by the Investigator to be primarily the result of DME. 6. Type 1 or Type 2 diabetes mellitus and a HbA1c of ≤12%. 7. Other protocol-specified inclusion criteria may apply. Exclusion Criteria: 1. Macular edema in the Study Eye considered to be secondary to a cause other than DME. 2. Active iris or angle neovascularization or neovascular glaucoma in the Study Eye. 3. High-risk proliferative diabetic retinopathy characteristics in the Study Eye. 4. History of Pan-retinal Photocoagulation (PRP) laser in the Study Eye within 3 months of screening. 5. Tractional retinal detachment in the Study Eye. 6. Active retinal disease other than the condition under investigation in the Study Eye. 7. Any history or evidence of a concurrent ocular condition present, that in the opinion of the Investigator could require either medical or surgical intervention or affect macular edema or alter visual acuity during the study (e.g., vitreomacular traction, epiretinal membrane). 8. Active or suspected ocular or periocular infection or inflammation in either eye at Day 1. 9. Any prior use of an approved or investigational treatment for DME in the Study Eye (e.g., anti-VEGF, intraocular or periocular steroids, macular laser photocoagulation). 10. Women who are pregnant or lactating or intending to become pregnant during the study. 11. Uncontrolled blood pressure defined as a systolic value ≥ 180 mmHg or diastolic value ≥100 mmHg while at rest. 12. Recent history (within the 6 months prior to screening) of myocardial infarction, stroke, transient ischemic attack, acute congestive heart failure or any acute coronary event. 13. History of a medical condition that, in the judgment of the Investigator, would preclude scheduled study visits, completion of the study, or a safe administration of investigational product. 14. Other protocol-specified exclusion criteria may apply.