Mark A. Walterfang

Background: Young-onset neurocognitive symptoms result from a heterogeneous group of neurological and psychiatric disorders which present a diagnostic challenge. To identify such factors, we analysed the Biomarkers in Younger-Onset Neurocognitive Disorders cohort, a study of individuals <65 years old presenting with neurocognitive symptoms for a diagnosis and who have undergone cognitive and biomarker analyses. Methods: Sixty-five participants (median age at assessment of 56 years, 45% female) were recruited during their index presentation to the Royal Melbourne Hospital Neuropsychiatry Centre, a tertiary specialist service in Melbourne, Australia, and categorized as either early-onset Alzheimer's disease (n = 18), non-Alzheimer's disease neurodegeneration (n = 23) or primary psychiatric disorders (n = 24). Levels of neurofilament light chain, glial fibrillary acidic protein and phosphorylated-tau 181, apolipoprotein E genotype and late-onset Alzheimer's disease polygenic risk scores were determined. Information-theoretic model selection identified discriminatory factors. Results: Neurofilament light chain, glial fibrillary acidic protein and phosphorylated-tau 181 levels were elevated in early-onset Alzheimer's disease compared with other diagnostic categories. A multi-omic model selection identified that a combination of cognitive and blood biomarkers, but not the polygenic risk score, discriminated between early-onset Alzheimer's disease and primary psychiatric disorders (area under the curve ⩾ 0.975, 95% confidence interval: 0.825-1.000). Phosphorylated-tau 181 alone significantly discriminated between early-onset Alzheimer's disease and non-Alzheimer's disease neurodegeneration causes (area under the curve = 0.950, 95% confidence interval: 0.877-1.00). Conclusions: Discriminating between early-onset Alzheimer's disease, non-Alzheimer's disease neurodegeneration and primary psychiatric disorders causes of young-onset neurocognitive symptoms is possible by combining cognitive profiles with blood biomarkers. These results support utilizing blood biomarkers for the work-up of young-onset neurocognitive symptoms and highlight the need for the development of a young-onset Alzheimer's disease-specific polygenic risk score.

Objective: N-acetyl-l-leucine (NALL) has been established to improve the neurologic manifestations of Niemann-Pick disease type C (NPC) after 12 weeks in a placebo-controlled trial. In the open-label extension phase (EP) follow-up, data were obtained after 12 and 18 months to evaluate the long-term effects of NALL for NPC. Methods: This is an ongoing, multinational, multicenter EP. Patients with a genetic diagnosis of NPC aged 4 years or older who completed the placebo-controlled trial were eligible to continue in the EP and receive orally administered NALL 2-3 times per day in 3 tiers of weight-based dosing. The primary end point is the modified 5-domain NPC Clinical Severity Scale (NPC-CSS) (range 0-25 points; lower score representing better neurologic status); data from the EP cohort are compared with the expected annual trajectory of decline (i.e., disease progression) established in natural history studies. Analyses are also performed on exploratory end points, including the 15-domain and 4-domain NPC-CSSs and the Scale for Assessment and Rating of Ataxia (SARA). Results: Fifty-three patients aged 5-67 years (45.3% female, 54.7% male) were enrolled in the EP. After 12 months, the mean (±SD) change from baseline on the 5-domain NPC-CSS was -0.27 (±2.42) with NALL vs +1.5 (±3.16) in the historical cohort (95% CI -3.05 to -0.48; p = 0.009), corresponding to a 118% reduction in annual disease progression. After 18 months, the mean (±SD) change was +0.05 (±2.95) with NALL vs +2.25 (±4.74) in the historical cohort (95% CI -4.06 to -0.35; p = 0.023). The 15-domain and 4-domain NPC-CSSs were consistent with the 5-domain NPC-CSS. The improvements in neurologic manifestations demonstrated in the placebo-controlled trial on the primary SARA end point were sustained over the long-term follow-up. NALL was well tolerated, and no treatment-related adverse events or serious reactions occurred. Conclusions: Treatment with NALL was associated with a significant reduction in NPC disease progression after 12 and 18 months, demonstrating a disease-modifying, neuroprotective effect. The trial is registered with ClinicalTrials.gov (NCT05163288; registered December 6, 2021), EudraCT (2021-005356-10). The first patient was enrolled into the EP on March 8, 2023. The trial was funded by IntraBio Inc. Methods: This study provides Class IV evidence that NALL reduces disease progression in NPC.

Objective: We investigated diagnostic utility of phosphorylated tau 217 and 181 (ptau217, ptau181), glial fibrillary acidic protein (GFAP), amyloid beta 42 and 40 (Aβ42, Aβ40), and neurofilament light (NfL) to distinguish biomarker-defined Alzheimer disease (AD) from non-AD conditions, in a heterogenous clinical cohort of younger people. Methods: Plasma biomarkers were analysed using ultrasensitive technology, and compared in patients with CSF Alzheimer disease profiles (A+T+) to other CSF profiles (Other). Results: Seventy-nine patients were included, median age 60.8 years: 16 A+T+, 63 Other. Ptau217, ptau181, GFAP were significantly elevated in A+T+ compared to Other (3.67 vs 1.12 pg/mL, 3.87 vs 1.79 pg/mL, 189 vs 80 pg/mL, respectively). ptau217 distinguished AD from Other with 90% accuracy (88% specificity, 100% sensitivity). ptau217 also demonstrated strong diagnostic performance for clinically diagnosed AD. Conclusions: Plasma ptau217 has strong diagnostic performance in distinguishing CSF biomarker-defined AD in a clinically relevant, younger cohort of people with symptoms, adding further weight for a simple diagnostic blood test for AD as a cause of a patient's symptoms.

Background: Niemann-Pick Disease Type C (NPC) is an ultra-rare disorder characterized by progressive psychiatric and neurologic manifestations, with late infantile, juvenile, and adolescent/adult presentations. We examined morphological properties of the choroid plexus, a protective blood-cerebrospinal fluid barrier, in NPC, and their relationship with neurodegeneration, clinical status, and circulatory markers. This study also determined whether choroid plexus morphology differentiates between NPC and more prevalent illnesses, schizophrenia (SZ) and bipolar disorder (BD), which have overlapping psychiatric symptoms with adolescent and adult-onset NPC and are associated with misdiagnosis. Methods: Patients with NPC were assessed using neuroimaging, clinical instruments, and plasma protein quantification focusing on inflammatory markers. Morphological properties (i.e., choroid plexus volumes) were compared between patients with NPC (n = 17), SZ (n = 20), BD (n = 24), and healthy controls (HCs, n = 106). Results: Choroid plexus enlargement (p < 0.05) and reduced thalamic volumes (p < 0.05) were observed in NPC patients versus HCs and SZ or BD patients. A logistic regression model with choroid plexus and thalamic volumes as predictors yielded high prediction accuracy for NPC vs. HCs, NPC vs. SZ, and NPC vs. BD (area under the receiver operating characteristics curve [AUROC] of 1). Choroid plexus volumes were negatively correlated with left (p = 0.009-0.012) and right (p = 0.007-0.025) thalamic volumes, left (r = -0.69, p = 0.003) and right (r = -0.71, p = 0.002) crus I of the cerebellum, and greater severity on the NPC-Suspicion Index psychiatric subscale (ρ = 0.72, p = 0.042). Targeted protein expression quantification revealed differential expression of TGFA, HLA-DRA, TNFSF12, EGF, INFG, and IL-18 in NPC patients vs. HCs (p < 0.05), with higher choroid plexus volumes correlating with IL-18 levels (ρ = 0.71, p = 0.047). Conclusions: The choroid plexus may play a critical role in NPC neuropathogenesis and serve as a novel biomarker for monitoring neurodegenerative and inflammatory processes in NPC.

Background: People with neurodegenerative disorders (ND) frequently face diagnostic delay and misdiagnosis. We investigated blood and cerebrospinal fluid (CSF) neurofilament light chain (NfL) to distinguish ND from primary psychiatric disorders (PPD), a common challenge in clinical settings. Methods: Plasma and CSF NfL levels were measured and compared between groups, adjusting for age, sex, and weight. Results: A total of 337 participants were included: 136 ND, 77 PPD, and 124 Controls. Plasma NfL was 2.5-fold elevated in ND compared to PPD and had strong diagnostic performance (area under the curve, [AUC]: 0.86, 81%/85% specificity/sensitivity) that was comparable to CSF NfL (2-fold elevated, AUC: 0.89, 95%/71% specificity/sensitivity). Diagnostic performance was especially strong in younger people (40- < 60 years). Additional findings were cutoffs optimized for sensitivity and specificity, and issues important for future clinical translation. Conclusions: This study adds important evidence for a simple blood-based biomarker to assist as a screening test for neurodegeneration and distinction from PPD, in clinical settings. Conclusions: NfL levels were significantly higher in ND versus PPD. Plasma NfL showed strong diagnostic performance, comparable to CSF NfL, to distinguish ND from PPD. Diagnostic performance was higher in younger people, where diagnostic challenges are greater. Further research is needed on analytical and reference range factors, for clinical translation. These findings support a simple screening blood test for neurodegeneration.

Complement Activation in the Lysosomal Storage Disorders