A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of GSK2798745 in Participants With Diabetic Macular Edema

The study will be composed of 3 periods for all participants: Screening, 28-day Treatment period, and Follow-up visit (approximately 28 days after the final dose).


Eligibility Criteria:
Inclusion Criteria:

* At least 18 to 75 years of age inclusive, at the time of signing the informed consent.
* Diagnosis of diabetes mellitus (type 1 or type 2).
* Confirmation of DME with center involvement in at least one eye by fluorescein angiography.
* Confirmation of retinal thickening (diabetic macular edema) involving the center of the fovea in the study by Investigator.
* Best Corrected Visual Acuity (BCVA) letter score of 80 letter or worse (Snellen equivalent: equivalent to 20/25) or worse in the study eye.
* Safe to withhold treatment of the study eye with laser photocoagulation, intravitreal steroid injection, or intravitreal vascular endothelial growth factor (VEGF) inhibitor for the duration of the study.
* Body weight greater than equal to (\>=) 50 kilograms (kg) and Body mass index (BMI) within the range 18 to 43 kg per square meter (inclusive) at screening.
* Male participants must agree to refrain from donating sperm, plus either be abstinent from heterosexual or homosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent or must agree to use acceptable contraception/barrier to use acceptable contraceptive methods if their partner is of childbearing potential. This criterion must be followed from the first dose of study treatment until the follow-up visit.
* A female participant is eligible to participate if she is not of childbearing potential.

Exclusion Criteria:

* Additional eye disease in the study eye that in the opinion of the Investigator could compromise assessment.
* History of choroidal neovascularization in the study eye, or current choroidal neovascularization in the fellow eye requiring treatment.
* Active Proliferative diabetic retinopathy (PDR) in the study eye or untreated active PDR in the fellow eye.
* Ischemic maculopathy on fluorescein angiography.
* Intraocular surgery or laser photocoagulation in the study eye within 90 day.
* Use of intravitreal ranibizumab,or bevacizumab within 42 days (6 weeks), or aflibercept within 56 days (8 weeks) of dosing in the study eye.
* Use of intraocular steroids in the study eye within 180 days of dosing.
* Use of or expected need for intravitreal or intraocular treatment in the study eye during course of the study.
* Use of any systemically administered anti-angiogenic agent within 6 months of dosing.
* Evidence of vitreomacular traction as determined by the Investigator.
* Uncontrolled intraocular pressure in the study eye despite treatment with glaucoma medication.
* Within 6 months prior to the Screening Visit, use of medications known to be toxic to the retina, lens or optic nerve
* Uncontrolled diabetes as indicated by glycated hemoglobin (HbA1c) \>12% at Screening.
* Active ulcer disease or gastrointestinal bleeding by history within 6 months of screening or by exam at the time of screening.
* Certain type of liver disease.
* Participant who, in the Investigator's opinion, poses a significant suicide risk.
* History or current evidence of any serious or clinically significant cardiac, gastrointestinal, renal, endocrine, neurologic, hematologic, infectious or other condition that is uncontrolled.
* Corrected (QTc) interval \>450 milliseconds (msec) or QTc \>480 msec in participants with bundle branch block.
* Use of certain medications that may interfere with the study medication or eye assessments (these will be identified by the study doctor).
* Current enrollment, or recent participation in a study of investigational intervention or medical research.
* Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the Investigator or Medical Monitor, contraindicates participation in the study.
* Any other reason the investigator deems the participant should not participate in the study.
* Other protocol-defined inclusion/exclusion criteria may apply.