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Alzheimer's disease (AD) research has entered a new era with the recent positive phase 3 clinical trials of the anti-Aβ antibodies lecanemab and donanemab. Why did it take 30 years to achieve these successes? Developing potent therapies for reducing fibrillar amyloid was key, as was selection of patients at relatively early stages of disease. Biomarkers of the target pathologies, including amyloid and tau PET, and insights from past trials were also critical to the recent successes. Moving forward, the challenge will be to develop more efficacious therapies with greater efficiency. Novel trial designs, including combination therapies and umbrella and basket protocols, will accelerate clinical development. Better diversity and inclusivity of trial participants are needed, and blood-based biomarkers may help to improve access for medically underserved groups. Incentivizing innovation in both academia and industry through public-private partnerships, collaborative mechanisms, and the creation of new career paths will be critical to build momentum in these exciting times. [ABSTRACT FROM AUTHOR]

Summary: Several families have been reported with autosomal-dominant frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), genetically linked to chromosome 9p21. Here, we report an expansion of a noncoding GGGGCC hexanucleotide repeat in the gene C9ORF72 that is strongly associated with disease in a large FTD/ALS kindred, previously reported to be conclusively linked to chromosome 9p. This same repeat expansion was identified in the majority of our families with a combined FTD/ALS phenotype and TDP-43-based pathology. Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (23.5%). The repeat expansion leads to the loss of one alternatively spliced C9ORF72 transcript and to formation of nuclear RNA foci, suggesting multiple disease mechanisms. Our findings indicate that repeat expansion in C9ORF72 is a major cause of both FTD and ALS. [Copyright &y& Elsevier]

Frontotemporal dementia (FTD) therapy development is hamstrung by a lack of susceptibility, diagnostic, and prognostic biomarkers. Blood neurofilament light (NfL) shows promise as a biomarker, but studies have largely focused only on core FTD syndromes, often grouping patients with different diagnoses. To expedite the clinical translation of NfL, we avail ARTFL LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) study resources and conduct a comprehensive investigation of plasma NfL across FTD syndromes and in presymptomatic FTD mutation carriers. We find plasma NfL is elevated in all studied syndromes, including mild cases; increases in presymptomatic mutation carriers prior to phenoconversion; and associates with indicators of disease severity. By facilitating the identification of individuals at risk of phenoconversion, and the early diagnosis of FTD, plasma NfL can aid in participant selection for prevention or early treatment trials. Moreover, its prognostic utility would improve patient care, clinical trial efficiency, and treatment outcome estimations., Competing Interests: A.C.B. is site PI for the Alector INFRONT-3 trial. A.L.B. receives research support from NIH (R01AG038791, R01AG073482, and U24AG057437), Rainwater Charitable Foundation, Association for Frontotemporal Degeneration, Bluefield Project to Cure Frontotemporal Dementia, Alzheimer’s Drug Discovery Foundation, and the Alzheimer’s Association. He has served as a consultant for Alector, AGTC, Arkuda, Arvinas, AZTherapies, GSK, Oligomerix, Ono, Roche, Samumed, Stealth, Third Rock, Transposon, TrueBinding, and Wave and received research support from Biogen, Eisai, and Regeneron. B.F.B. has served as an investigator for clinical trials sponsored by Biogen, Alector, and EIP Pharma. He receives royalties from a published book entitled Behavioral Neurology of Dementia (Cambridge Medicine, 2009, 2017), serves on the Tau Consortium Scientific Advisory Board, and receives research support from the NIH. B.C.D. consults for Acadia, Arkuda, Axovant, Lilly, Biogen, Merck, Novartis, and Wave LifeSciences; has Elsevier editorial duties with payment (Neuroimage: Clinical and Cortex); and receives royalties from Oxford University Press and Cambridge University Press. K.D.-R. has research funding from Biogen and Lawson Health Research Institute and receives consultant fees from Biogen and educational fees from MedBridge. D.R.G. consults for Biogen, Fujirebio, and Amprion and is on the DSMB for Cognition Therapeutics. M.G. is participating in treatment trials sponsored by Alector, Prevail, and Passage Bio and is a consultant to Takeda, Passage Bio, and Biogen. N.G. has or is participating in clinical trials of anti-dementia drugs sponsored by Bristol Myers Squibb, Lilly/Avid Radiopharmaceuticals, Janssen, Novartis, Pfizer, and Wyeth. N.R.G.-R. has taken part in multicenter studies funded by Biogen, AbbVie, and Lilly. G.-Y.R.H. has received research support from Anavax, Biogen, and Roche. I.L. received support from Roche, Abbvie, Biogen, EIP-Pharma, and Biohaven Pharmaceuticals; was member of a Lundbeck Advisory Board; and receives salary from the University of California, San Diego and as Chief Editor of Frontiers in Neurology. J.C.M. participates on a speaker forum for Biogen and receives research support from Biogen, Eisai, Eli Lilly, Green Valley, and Novartis. C.U.O. is a consultant with Alector and Acadia and receives research funding from Alector. L.P. is a consultant for Expansion Therapeutics. E.D.R. receives funding from NIH, Alzheimer’s Drug Discovery Foundation, Bluefield Project, and Alector; consults for Biogen, AVROBIO, and AGTC; and owns intellectual property related to tau. J.C.R. is a site PI for Eli Lilly and Eisai clinical trials and receives research support from NIH K23AG059888. M.C.T. participates in clinical trials with Biogen, Avanex, UCB, and Janssen. Z.K.W. is supported by the NIH/NIA and NIH/NINDS (1U19AG063911, FAIN: U19AG063911), Mayo Clinic Center for Regenerative Medicine, Mayo Clinic in Florida Focused Research Team Program, the gifts from The Sol Goldman Charitable Trust, the Donald G. and Jodi P. Heeringa Family, the Haworth Family Professorship in Neurodegenerative Diseases fund, and The Albertson Parkinson’s Research Foundation. He serves as PI or co-PI on Biohaven Pharmaceuticals, Inc. (BHV4157-206 and BHV3241-301); Neuraly, Inc. (NLY01-PD-1); and Vigil Neuroscience, Inc. (VGL101–01.001) grants. He serves as co-PI of the Mayo Clinic APDA Center for Advanced Research and as an external advisory board member for Vigil Neuroscience, Inc. All other authors report no competing interests., (© 2022 The Author(s).)

GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found that Grn -/- mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn -/- brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine. We investigated a protein replacement strategy by engineering protein transport vehicle (PTV):PGRN-a recombinant protein linking PGRN to a modified Fc domain that binds human transferrin receptor for enhanced CNS biodistribution. PTV:PGRN rescued various Grn -/- phenotypes in primary murine macrophages and human iPSC-derived microglia, including oxidative stress, lysosomal dysfunction, and endomembrane damage. Peripherally delivered PTV:PGRN corrected levels of BMP, glucosylsphingosine, and disease pathology in Grn -/- CNS, including microgliosis, lipofuscinosis, and neuronal damage. PTV:PGRN thus represents a potential biotherapeutic for GRN-FTD., Competing Interests: Declaration of interests All authors, except A.L.B., H.H., H.J.R., and B.F.B., are full-time employees and/or shareholders of Denali Therapeutics. A.L.B. reports consultancy for AGTC, Alector, Arkuda, Arvinas, Asceneuron, AZTherapies, Bioage, GSK, Humana, Lundbeck, Ono, Roche, Samumed, Sangamo, Stealth Therapeutics, Third Rock, Transposon, UCB, and Wave and research support from the Association for Frontotemporal Degeneration, Biogen, Bluefield Project to Cure Frontotemporal Dementia, Eli Lilly, Eisai, National Institutes of Health (grant numbers U19AG063911, U54NS092089, R01AG031278), and the Rainwater Charitable Foundation. B.F.B. reports research support from the NIH (U19AG063911). H.J.R. reports funding from the NIH and consultancy with Alector, Ionis, Biogen, Wave, Takeda, and AFTD. This work has been in part described in one or more pending patent applications., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Tauopathies represent a group of neurodegenerative disorders characterized by the accumulation of pathological TAU protein in brains. We report a human neuronal model of tauopathy derived from induced pluripotent stem cells (iPSCs) carrying a TAU-A152T mutation. Using zinc-finger nuclease-mediated gene editing, we generated two isogenic iPSC lines: one with the mutation corrected, and another with the homozygous mutation engineered. The A152T mutation increased TAU fragmentation and phosphorylation, leading to neurodegeneration and especially axonal degeneration. These cellular phenotypes were consistent with those observed in a patient with TAU-A152T. Upon mutation correction, normal neuronal and axonal morphologies were restored, accompanied by decreases in TAU fragmentation and phosphorylation, whereas the severity of tauopathy was intensified in neurons with the homozygous mutation. These isogenic TAU-iPSC lines represent a critical advancement toward the accurate modeling and mechanistic study of tauopathies with human neurons and will be invaluable for drug-screening efforts and future cell-based therapies.