All participants, study eye: - Center-involved diabetic macular edema (CI-DME) defined as CST ≥320 μm (micrometers) at Screening, as confirmed on spectral-domain optical coherence tomography (SD-OCT) and confirmed by the central reading center (CRC). - Sufficiently clear ocular media, adequate pupillary dilation, and fixation, to permit quality fundus imaging. All participants: - Diagnosis of diabetes mellitus (DM) type 1 or type 2 under regular treatment, with glycated hemoglobin HbA1c <12%. - Be willing and able to understand the study procedures and the risks involved. - Signed and dated written informed consent in accordance with international council for harmonization - good clinical practices (ICH-GCP) and local legislation prior to admission to the trial and any trial related procedures. - Age ≥18 years (or above legal age according to local legislation) at time of signing the informed consent form (ICF). - Male or female participants - Woman of childbearing potential (WOCBP) must be ready and able to use highly effective methods of birth control - For men, contraception (condom or complete abstinence) should be used as precaution to prevent pregnancy of a partner and/or exposure of an existing embryo or fetus. Further inclusion criteria apply.

All participants, study eye: - Only one functional eye, even if that eye was otherwise eligible for the study. Fellow eye must have sufficient visual function per the investigator's medical judgment in consultation with the participant, to support the participant's daily functioning. - Evidence of active proliferative diabetic retinopathy (PDR). - Evidence of active retinal neovascularization (NV) clinical exam and/or Ultra-Widefield Color Fundus Photography ((UWF-)CFP) within the early treatment diabetic retinopathy study (ETDRS) 7-field, confirmed by the CRC grading. Potential participants with NV outside of the ETDRS 7-field on ultra-widefield imaging may be included in the trial if this condition, based on the assessment of the investigator, does not require acute treatment. - Evidence of active NV of the iris (small iris tufts are not an exclusion) or in the anterior chamber angle. - Additional eye disease in the study eye that could compromise trial participation: - Uncontrolled glaucoma or intraocular pressure (IOP) >24 mmHg despite treatment - History of high myopia >8 diopters in the study eye - Anterior segment and vitreous abnormalities in the study eye that would preclude adequate detection of intraocular inflammation (IOI) or other pathologies - Ocular conditions which, at discretion of the investigator, might interfere with the outcome of the trial. - Previously received ocular gene therapy or cell therapy. - Corticosteroid use locally or systemically within 1 month prior to Screening. - Aphakia or total absence of the posterior capsule. Yttrium aluminum garnet (YAG) laser capsulotomy may be permitted, if performed more than 2 months prior to Day 1. Further exclusion criteria apply.