First, the rate of CNV—i.e. the rate of conversion to wet AMD—was substantially higher in the Zimura arms than in the sham (placebo) arm:
During the first 12 months of the trial, the incidence of choroidal neovascularization (CNV) in the untreated fellow eye was 10 patients (3.5%), and in the study eye was 3 patients (2.7%) in the sham control group; 6 patients (9.0%) in the Zimura 2 mg group; and 8 patients (9.6%) in the Zimura 4 mg group.
Conversion to wet AMD is a very bad outcome that renders any improvement in GA essentially meaningless for these patients.
Further, the BVCA (best corrected visual acuity) change from baseline had an inverse dose response whereby the 4mg Zimura arm had worse results than the 2mg arm.
Moreover, the BVCA change after 12 months in the 4mg Zimura arm was worse than in the placebo arm, as can be seen from the secondary-endpoint tables in the PR.
All told, the dataset from this phase-2b trial is highly problematic, IMO.