HORIZON: A Phase II Study to Evaluate the Safety and Efficacy of Two Doses of GT005

Open to people ages 55 years and up

1. Able and willing to give written informed consent
2. Age ≥55 years
3. 1. In Stage 1: Have a clinical diagnosis of GA secondary to AMD in the study eye, as determined by the Investigator, and a diagnosis of AMD in the contralateral eye; b.

   In Stage 2: Have a clinical diagnosis of GA secondary to AMD in the study eye, as determined by the Investigator, that is non-foveal, as determined by the central reading centre, or has a CFI rare variant genotype and meets inclusion criteria 3a, and a diagnosis of AMD in the contralateral eye (except if monocular)

4. GA lesion(s) within an acceptable size on FAF, in the study eye
5. The GA lesion in the study eye must reside completely within the FAF image
6. Up to 25% of the enrolled study population are permitted to have CNV in the fellow eye
7. Have a BCVA of ≥24 letters (6/95 or 20/320 Snellen acuity equivalent), using ETDRS charts, in the study eye
8. 1. In Stage 1: Meet one of the pre-specified AMD genetic subgroup criteria; b. In

   Stage 2: Genotyping is not required for study eligibility

9. Able to attend all study visits and complete the study procedures
10. Women of child-bearing potential must have a negative pregnancy test within 2 weeks prior to randomisation (not required for postmenopausal women) or provide documentation of being surgically sterilised

1. 1. In Stage 1: Carriers of excluded genetic variants; b. In Stage 2: Subjects are excluded if they have a clinical diagnosis of Stargardt Disease or other retinal dystrophies
2. Have a history, or evidence, of CNV in the study eye
3. Presence of moderate/severe or worse non-proliferative, diabetic retinopathy in the study eye
4. Have history of vitrectomy, sub-macular surgery, or macular photocoagulation in the study eye
5. History of intraocular surgery in the study eye within 12 weeks prior to Visit 1
6. Have clinically significant cataract that may require surgery during the study period in the study eye
7. Presence of moderate to severe glaucomatous optic neuropathy, uncontrolled intraocular pressure (IOP), despite use of two or more topical agents; or a history of glaucoma-filtering or valve surgery
8. Axial myopia of greater than -8 diopters in the study eye
9. Have received any investigational product for the treatment of GA within the past 6 months or 5 half-lives (whichever is longer), other than nutritional supplements such as the age-related eye disease study (AREDS) formula
10. Have received a gene or cell therapy at any time.
11. Have a contraindication to the protocol specified corticosteroid regimen
12. Are unwilling to use two forms of contraception (one of which being a barrier method) for 90 days post-dosing, if relevant
13. Active malignancy within the past 12 months, except for appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, or prostate cancer with a stable prostate-specific antigen (PSA) ≥ 12 months
14. Have any other significant ocular or non-ocular medical or psychiatric condition which, in the opinion of the Investigator, may either put the subject at risk or may influence the results of the study