Surabgene Lomparvovec Administered in the Suprachoroidal Space in Adult Participants With Diabetic Retinopathy Without Center-Involved Diabetic Macular Edema

Inclusion Criteria:

Ocular (Study Eye for Phase 2b and Phase 3 Portions; Both Eyes for Bilateral Portion)

• Moderately severe or severe nonproliferative diabetic retinopathy (NPDR) (earlytreatment diabetic retinopathy study-diabetic retinopathy severity scale [DRSS]level 47 or 53) for which panretinal photocoagulation (PRP) or anti- vascularendothelial growth factor (VEGF) can be safely deferred for at least 6 months afterScreening Visit 1.

• Best-corrected visual acuity (BCVA) in the study eye of >= 69 Early treatmentdiabetic retinopathy study letters (approximate Snellen equivalent 20/40 or better)at Screening Visit 1.

Systemic

• Diabetic retinopathy (DR) secondary to diabetes mellitus Type 1 or 2 with a hemoglobin A1c (HbA1c)< 12% within 60 days prior to Screening Visit 1.

Exclusion Criteria:

Ocular (Study Eye for Phase 2b and Phase 3 Portions; Both Eyes for Bilateral Portion)

• Presence of active center involved-diabetic macular edema (CI-DME) in the study eyeas determined by spectral domain optical coherence tomography (SD-OCT) evaluated bythe central reading center (CRC), using the following threshold:

Central retinal thickness (CRT) >= 320 μm as measured by Heidelberg Spectralis SD-OCT (conversion to equivalent measurement is required and performed by the CRC if imaging is done with another SD-OCT instrument).

• Active ocular inflammation including scleral inflammation (including episcleritis)or ocular/ periocular infection present in either eye at Screening Visit 1 orScreening Visit 2

• Neovascularization from a cause other than DR, per investigator

• Evidence or documented history of panretinal photocoagulation (PRP) or retinal lasertherapy

• History of intravitreal therapy, including anti-VEGF and long- or short-actingsteroid therapy, within the prior 6 months and documentation of more than 10 prioranti-VEGF or short acting steroid intravitreal injections within 36 months ofScreening Visit 1

• Pregnant and breastfeeding individuals are excluded from this clinical study.

Systemic

• Initiation of intensive insulin treatment (pump or multiple daily injections) withinthe past 6 months or plans to do so within 52 weeks after Day 1

• Initiation of any treatment containing a GLP-1 receptor agonist within the 3 monthsprior to Screening Visit 1 or plans to do so within 52 weeks after Day 1

• Pregnant and breastfeeding individuals are excluded from this clinical study