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

EXPLORE: A Phase II, Outcomes Assessor-masked, Multicentre, Randomised Study to Evaluate the Safety and Efficacy of Two Doses of GT005 Administered as a Single Subretinal Injection in Subjects With Geographic Atrophy Secondary to Age-related Macular Degeneration

The purpose of this clinical study was to evaluate the safety and efficacy of two doses of GT005 administered as a single subretinal injection in subjects with geographic atrophy secondary to age-related macular degeneration (AMD).

This was a Phase II, outcomes assessor-masked, multicentre, randomized study to assess the safety and efficacy of two doses of GT005 administered as a single-time subretinal injection in subjects with Geographic Atrophy (GA) secondary to age-related macular degeneration (AMD). Approximately 202 subjects were planned to be randomized to GT005 or the untreated control group.

Subjects entered the study had genotyping and serum complement factor I(CFI) levels assessed. Assessments were either performed at a sponsor-approved laboratory during the EXPLORE screening period or provided through participation in a previous Gyroscope sponsored study. If subjects failed to meet the eligibility criteria for EXPLORE, they were classified as screen failures for this study and could be considered for entry into another Novartis/Gyroscope sponsored study.

After providing the informed consent, subjects underwent ophthalmic and clinical assessments to determine eligibility for inclusion in the study.

Upon confirmation of eligibility, subjects in part 1 were randomized to one of two groups: low dose [2E10 vg], or high dose [2E11 vg]. Within each group, subjects were allocated to GT005 or untreated control based on a 2:1 ratio. Once part 1 enrolment was completed, and the last active subject completed screening and either was screen-failed or randomized, then Part 2 could commence. In part 2, subjects were randomized to the low dose [2E10] group or untreated control based on a 2:1 ratio. The study eye was identified for all subjects.

Subjects were stratified by GA lesion size on fundus autofluorescence (FAF) (≤10 mm2 or >10 mm2) and presence of choroidal neovascularisation (CNV) in the fellow eye (Yes or No). Randomization of study eyes in the GA lesion size upper stratum of >10 mm2 to 17.5 mm2 was capped at 20% of total subjects randomized. Once enrolment capping at 20% based on the upper GA lesion size was reached, eyes that fulfilled the cap criteria were no longer eligible, unless the subject had a CFI rare variant genotype (minor allele frequency ≤1%) previously associated with normal or low serum CFI or had an unreported CFI rare variant genotype. Of all subjects enrolled and randomized in the study, the presence of CNV in the fellow eye was capped at 25% per stratum. A permuted-block randomization method was used to obtain an approximately 2:1 ratio between GT005 and the untreated control groups for each dose group within each stratum.

Following randomization, the investigator was informed of the subject's allocated treatment (GT005 or the untreated control group) and the study eye selected. To minimize bias, all imaging endpoint assessments and grading were performed at a Central Reading Centre (CRC), in a masked fashion. For part 1, the Sponsor, subject, investigators, and study personnel performing clinical assessments remained masked to dose received for those allocated to GT005. For part 2, the Sponsor, investigators, subjects, and study personnel performing clinical assessments were unmasked to dose received, since only the low dose was administered.

Subjects randomized to GT005 underwent a single time subretinal administration of the study drug. Vitreous samples were collected during surgery. Following surgery, a prophylactic steroid regimen was prescribed.

The study consisted of a screening period lasting up to 8 weeks (or up to 12 weeks if agreed by the Sponsor Medical Monitor), followed by a 96-week study period. All subjects were assessed for the occurrence of adverse events (AEs) at each visit and underwent functional visual and retinal imaging,anatomical assessments, and biological sampling as per the schedule of assessments.

This study was conducted in compliance with Independent ethics committees (IECs) / Institutional review board (IRBs), informed consent regulations, the Declaration of Helsinki, International Council on Harmonisation (ICH) Good Clinical Practices (GCP) Guidelines, and the Food and Drug Administration (FDA) guidance.

On 24-Aug-2023, the decision was taken to terminate the study and the GT005 program. The decision was aligned with the recommendation of an independent DMC, which concluded that futility criteria had been met for the HORIZON study (GT005-03) and the overall benefit-risk ratio did not support continuation of the current development program as planned. All GT005- treated subjects, who were willing to be transferred into the long-term safety follow-up study were enrolled in the ORACLE (CPPY988A12203B / NCT05481827) study.

In both Part 1 and Part 2, patients with geographic atrophy secondary to age-related macular degeneration were enrolled. In Part 1, patients with CFI rare variant genotype and low serum CFI level and in Part 2, patients were enrolled regardless of genotypes. Efficacy results were analyzed by arm and also by part. AE and disposition data were reported per arm, but the parts were combined, according to the analysis plan.

Part 1 enrolled subjects with CFI rare variant; Part 2 enrolled subjects regardless of genotype.

There were no subjects in the high dose arm in Part 2.

Inclusion Criteria:

1. Able and willing to give written informed consent

2. Age ≥55 years

3. 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 (except if the subject is monocular)

4. Have GA lesion(s) total size between or equal to 1.25mm2 to 17.5mm2 in the study eye

5. The GA lesion(s) 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, defined as either:

   1. Non-exudative/sub-clinical fellow eye CNV identified at Screening, or
   2. Known history of fellow eye CNV with either ≥2 years since diagnosis or with no active treatment required in 6 months prior to Screening

7. Have a BCVA of 24 letters (6/95 and 20/320 Snellen acuity equivalent) or better, using ETDRS charts, in the study eye

8. Part 1 Only: Subjects carrying a CFI rare variant genotype (minor allele frequency of ≤1%) previously associated with low serum CFI or subjects carrying an unreported CFI rare variant genotype that have tested to have a low serum CFI

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. A pregnancy test is not required for postmenopausal women (defined as being at least 12 consecutive months without menses) or those surgically sterilised (those having a bilateral tubal ligation/bilateral salpingectomy, bilateral tubal occlusive procedure, hysterectomy, or bilateral oophorectomy)

Exclusion Criteria:

1. Subjects who have a clinical diagnosis of Stargardt Disease or other retinal dystrophies, confirmed by the central reading centre
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 Screening (Visit 1). Yttrium aluminium garnet capsulotomy is permitted if performed >10 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 in the study eye; uncontrolled IOP despite the use of two or more topical agents; a history of glaucoma-filtering or valve surgery is also excluded
8. Axial myopia of greater than -8 dioptres in the study eye
9. 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
10. Have a contraindication to specified protocol corticosteroid regimen
11. Have received any investigational and/or approved product(s) 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 in the study eye or systemically
12. Have received a gene or cell therapy at any time
13. Are unwilling to use two forms of contraception (one of which being a barrier method) for 90 days post-dosing, if relevant
14. 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