Change from Baseline to Week 24 in the Early and Mild Alzheimer's Cognitive Composite (EMACC), a z-score composite of six neuropsychological tests (International Shopping List Test-Immediate Recall; Digit Span Forward/Backward; Category Fluency; Letter Fluency [D-KEFS]; Trail Making Test A and B; Digit Symbol Coding). Each component is standardized to the pooled baseline mean (0) and SD (1), then averaged. Higher scores indicate better cognitive performance; a positive change from baseline indicates improvement.

Modified Intent-to-Treat (mITT) population: all randomized participants who received ≥1 dose of study drug and had ≥1 post-baseline efficacy assessment (n=200). Week 24 MMRM included 169 participants with EMACC data (XPro1595 n=111, Placebo n=58). The mITT was the pre-specified primary analysis population per the Statistical Analysis Plan.

Change from Baseline to Week 24 in the Clinical Dementia Rating - Sum of Boxes (CDR-SB), the sum of the six CDR domain box scores (each 0, 0.5, 1, 2, or 3); total range 0 to 18, with higher scores indicating greater impairment (worse outcome). A negative change favors XPro1595 (less decline).

Modified Intent-to-Treat (mITT) population: all randomized participants who received ≥1 dose of study drug and had ≥1 post-baseline efficacy assessment (n=200). Week 24 MMRM included 179 participants with CDR-SB data (XPro1595 n=120, Placebo n=59). Analyzed per the Statistical Analysis Plan

Change from Baseline to Week 24 in the Everyday Cognition (E-Cog) total score, a 39-item informant-report questionnaire that asks the study partner to rate the participant's current performance on cognitively relevant everyday activities relative to 10 years prior (i.e., before illness onset). Activities span memory, language, visuospatial/perceptual abilities, planning, organization, and divided attention. Each item is rated on a 4-point scale from 1 (better or no change) to 4 (consistently much worse). The total score is the mean of all rated items and ranges from 1 to 4, with higher scores indicating greater decline since prior to illness onset.

Modified Intent-to-Treat (mITT) population: all randomized participants who received ≥1 dose of study drug and had ≥1 post-baseline efficacy assessment (n=200). Week 24 MMRM included 177 participants with E-Cog data (XPro1595 n=119, Placebo n=58). Analyzed per the Statistical Analysis Plan.

Change from Baseline to Week 24 in the Neuropsychiatric Inventory, 12-domain version (NPI-12), a structured interview administered to the study partner (informant) assessing 12 neuropsychiatric domains (delusions; hallucinations; agitation/aggression; depression/dysphoria; anxiety; elation/euphoria; apathy/indifference; disinhibition; irritability/lability; aberrant motor behavior; nighttime behaviors; appetite/eating). Each domain is scored as frequency (1-4) × severity (1-3); the total score is the sum of domain scores and ranges from 0 to 144.

Higher scores indicate greater neuropsychiatric burden (worse outcome); a negative change from baseline favors XPro1595. The total score is reported; domain or subfactor scores, where applicable, are interpreted only within the context of the full instrument.

Modified Intent-to-Treat (mITT) population: all randomized participants who received ≥1 dose of study drug and had ≥1 post-baseline efficacy assessment (n=200). Week 24 MMRM included 179 participants with NPI-12 data (XPro1595 n=120, Placebo n=59). Analyzed per the Statistical Analysis Plan

Goal Attainment Scaling (GAS): an individualized outcome in which each participant set a minimum of three personalized treatment goals at baseline. Attainment of each goal is rated on a 5-point scale (-2 = much worse than expected; -1 = baseline/somewhat worse; 0 = expected goal level; +1 = somewhat better; +2 = much better than expected).

A participant's goal ratings are aggregated across goals into a standardized GAS T-score using the Kiresuk-Sherman formula (which accounts for the number of goals and their inter-correlation), scaled to a mean of 50 and a standard deviation of 10. The reported values are the standardized GAS T-score, not the individual -2 to +2 ratings; a T-score of 50 indicates goals were met on average, and higher T-scores indicate greater goal attainment (better outcome).

Modified Intent-to-Treat (mITT) population: all randomized participants who received ≥1 dose of study drug and had ≥1 post-baseline efficacy assessment as per the SAP