Age-related macular degeneration (AMD) is the abnormal growth of new blood vessels in the light-sensitive tissue at the back of the eye called the retina. Geographic Atrophy (GA) is an advanced form of dry AMD. The purpose of this study is to assess the adverse events and how intravitreal ABBV-6628 moves through the body of adult participants with secondary to age-related macular degeneration

ABBV-6628 is an investigational monoclonal antibody fragment being developed for the treatment of geographic atrophy (GA) secondary to (AMD) age-related macular degeneration. Participants in the Stage 1 part will be placed in 1 of 4 groups, called treatment arms. Participants in Stage 2 will be placed into 1 of 2 groups. Each group receives different treatment. Adult participants aged 50 and older years with a diagnosis GA secondary to age-related macular degeneration will be enrolled. Around 66 participants will be enrolled in the study at approximately 27 sites across the US.

Participants in Stage 1 will be given ABBV-6628 as an intravitreal injection (injection into the jelly-like tissue that fills the eyeball injection) with dose escalation. Participants in Stage 2 will receive ABBV-6628 or SYFOVRE, an approved treatment for geographic atrophy, administered as per the FDA-approved label. The treatment duration is approximately 22 months and 3 months of follow-up.

There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular weekly visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.

Inclusion Criteria:

Stage 1 and Stage 2

-Diagnosed with Geographic atrophy (GA) secondary to age-related macular degeneration (AMD) in the study eye.

Stage 1

• Foveal or non-foveal GA with total GA lesion area ≥ 0.5 DA (1.25 mm2) in the study eye, as assessed by the investigator at Screening and confirmed by the central reading center prior to Baseline/Day 1
• Absence of choroidal neovascularization (CNV) in the study eye as assessed by the investigator at Screening and confirmed by the central reading center prior to Baseline/Day 1. In addition, investigators should confirm eligibility prior to treatment administration on Baseline/Day 1.

Stage 2

• Non-foveal GA with total lesion area of 1 to 7 DA (2.5 to 17.5 mm2); within 0.5 to 1.5 mm from fovea center in the study eye, as assessed by the investigator at Screening and confirmed by the central reading center prior to Baseline/Day 1.
• Absence of CNV in both eyes as assessed by the investigator at Screening and confirmed by the central reading center prior to Baseline/Day 1. In addition, investigators should confirm eligibility prior to treatment administration on Baseline/Day 1.

Exclusion Criteria:

Stage 1 and Stage 2

• History of recurrent or currently active ocular or intraocular inflammation (e.g., uveitis, endophthalmitis) in at least one eye at Screening and Baseline/Day 1.
• Active periocular, ocular, or intraocular infection in at least one eye at Baseline/Day 1.
• History or clinical signs of diabetic retinopathy, diabetic macular edema (DME), or any retinal vascular disease other than AMD in at least one eye at Screening and Baseline/Day 1.