The subjects in this study will be subjects with central-involved DME (CI-DME). Both treatment-naïve and previously treated subjects will be included.  Inclusion Criteria:  Written informed consent obtained from the subject prior to screening procedures Male or female aged 18 years or older at the time of signing the informed consent Type 1 or type 2 diabetes BCVA ETDRS letter score ≥ 39 in the study eye CI-DME with CST of ≥ 300µm in men (or equivalent in women), measured from RPE to ILM inclusively, on SD-OCT, in the study eye BCVA ETDRS letter score ≥ 34 in the fellow eye  Exclusion Criteria:  Macular edema due to causes other than DME in the study eye Concurrent disease in the study eye, other than DME, that could require medical or surgical intervention during the study period or could confound interpretation of the results Any condition in the study eye that could confound the ability to detect the efficacy of the investigational medicinal product Previous confounding medications / interventions, or their planned administration during the study Presence of iris neovascularisation in the study eye Uncontrolled glaucoma in the study eye Previously received THR-687 or any other experimental therapy for DME, in either eye Any active or suspected ocular or periocular infection, or active intraocular inflammation, in either eye Untreated Diabetes Glycated haemoglobin A (HbA1c) > 12% Uncontrolled hypertension