Molecular Therapy

Autosomal dominant retinitis pigmentosa (adRP) caused by RHO mutations is a leading form of inherited retinal degeneration. Extensive allelic heterogeneity of RHO pathogenic variants limits the translational applicability of mutation-specific gene therapies. To address this, we developed SNARE (SNP-guided Silencing of Aberrant RHO Expression), a mutation-independent, allele-specific antisense oligonucleotide (ASO) strategy. SNARE selectively suppresses mutant RHO transcripts by targeting the common, benign c.-26A/G single-nucleotide polymorphism (SNP) as an allelic discriminator. Candidate gapmer ASOs were screened in engineered reporter lines and validated in patient-derived retinal organoids, identifying RHOligo-A as the lead c.-26A-targeting candidate. In vitro, RHOligo-A achieved robust, preferential knockdown of the target allele, improving RHO localization in retinal organoids, and demonstrated a favorable safety profile with minimal transcriptomic off-target effects and no detectable immunostimulatory activity. Subsequent validation in a novel, humanized RHOP347L/WT mouse model, achieved sustained c.-26A-linked allele-selective suppression, retinal structure preservation, and significantly restored visual function, upon a single intravitreal administration. These findings establish RHOligo-A and SNARE as a scalable, mutation-independent therapeutic platform with strong translational potential and substantial clinical reach for RHO-associated adRP.

Nonsense variants cause 18% of inherited retinal diseases (IRDs), yet current therapies require variant-specific development, leaving most patients untreated. Here, we combined a large-scale genetic analysis literature survey of >37,500 IRD patients with anticodon-edited (ACE)-tRNA engineering to create a single, gene-agnostic therapy targeting Arg>Ter nonsense variants which are the most prevalent subclass (35%) of premature stop codons (PTCs). We developed an optimized ACE-tRNA (V3) that achieved up to 86% readthrough across 13 clinically relevant variants, restored native PRCD localization in the arRP-causing p.R22* mutant, and demonstrated activity in photoreceptor-like cells. To enable translation, we established an AAV2/7m8 production platform (1*10{superscript 1}{superscript 2}-1*10{superscript 1}3 GC/mL) and defined 1*10 GC/eye as the safe dose in mice. This patient genetics-guided strategy positions ACE-tRNA_V3 as a promising candidate for preclinical development, offering a precision medicine approach that targets the most common nonsense variant class with a single therapeutic molecule.

To facilitate the translation of NF1 exon 17 skipping as a mutation-specific therapy for Neurofibromatosis type 1 into in vivo testing, we have continued to develop more efficient antisense oligonucleotides (ASOs), humanized mouse models, and explored multiple delivery platforms including an adeno-associated virus (AAV)-U7-SnRNA vector approach. We evaluated both biodistribution and exon skipping efficacy of a U7-SnRNA targeting NF1 exon 17 with an SFFV-driven cassette containing T2A-linked Luciferase (Luc) and eGFP packaged in AAV-9, AAV-F and AAV-B1 capsids. We show that AAV-F is superior to AAV-9 and AAV-B1 for mouse brain delivery based on DNA transduction, GFP expression, and luciferase activity, but AAV-B1 delivers 2-4 fold more to sciatic nerve (SCN). In terms of exon skipping, AAV-F appears to induce the most skipping in liver and optic nerve (ON), while AAV-B1 mediates highest skipping in the liver, SCN, and ON. The identification of AAV serotypes that allow efficient transduction and delivery of transgenes to the mouse CNS and PNS is impactful for preclinical research in murine models of other diseases. Furthermore, this is both the first report of NF1 exon skipping efficacy in vivo and the first successful application of an U7-SnRNA for the restoration of functional neurofibromin for NF1.

Autosomal dominant Best vitelliform macular dystrophy (BVMD) caused by variants in the BEST1 gene is characterized by dysfunction of the macular retinal pigment epithelium (RPE) and secondary degeneration of the photoreceptors. There are currently no approved treatments for BVMD, and owing to its dominant nature, there remains uncertainty regarding the utility of traditional gene augmentation. Here we evaluated whether a dominant pathogenic BEST1 allele can be corrected by base editing in differentiated RPE cells. We identified a patient with a likely pathogenic BEST1 c.851A>G (p. Tyr284Cys) variant that was amenable to cytidine base editing. After establishing patient-derived induced pluripotent stem cells (iPSCs), we corrected the pathogenic variant in the iPSCs to obtain corrected iPSCs with the same genetic background. Corrected iPSC-derived RPE exhibited normalized monolayer appearance, improved barrier integrity, reduced cell death, and restored RPE-specific transcriptome. We then used a dual adeno-associated virus (AAV) split-intein system to deliver a CRISPR-associated protein 9 cytidine base editor (SpCas9-CBE) to BEST1 c.851A>G mutant RPE monolayers and achieved editing of the pathogenic allele with a maximum efficiency of 13.42 {+/-} 3.64% (mean {+/-} SD). Together, these results demonstrate progress towards allele-specific base editing in a dominantly inherited retinal disorder.

PurposeAutosomal dominant retinitis pigmentosa caused by mutations in the rhodopsin gene (RHO-adRP) is among the most prevalent inherited retinal dystrophies. With nearly 100 distinct pathogenic variants identified to date, the mutational heterogeneity of RHO-adRP severely limits the clinical utility of mutation-specific therapeutic strategies. We aimed to develop a mutation-agnostic gene insertion therapy using homology-independent targeted integration (HITI) mediated by zinc finger nuclease ZF-ND1 targeting the human RHO 5'-UTR, and to validate its preclinical efficacy, safety, proof-of-concept, and proof-of-mechanism. MethodsWe developed two AAV serotype 5 (AAV5) vectors: one encoding the ZF-ND1 pair (AAV5-ZFN) and one carrying the therapeutic donor cassette (AAV5-RHO), delivered by subretinal co-injection. ZF pairs targeting the RHO 5'-UTR were arranged and refined by in vitro validation; AAV vector optimization and mechanistic verification were performed in human induced pluripotent stem cell (hiPSC)-derived retinal organoids-derived retinal organoids; longitudinal proof-of-concept efficacy and safety were assessed in a humanized RHO-T17M rat disease model by 6-month optical coherence tomography (OCT); and proof-of-mechanism was evaluated in non-human primate retina. ResultsWe identified a ZF-ND1 pair achieving cleavage efficiency comparable to the SpCas9 RNP previously validated for HITI-mediated editing in mouse retina, and optimized the ZF array composition and NLS configuration for efficient editing especially in post-mitotic photoreceptors. HITI-mediated donor integration was confirmed across multiple cell types and ZFN:donor ratios. In the humanized rat disease model, the therapeutic vector provided outer nuclear layer (ONL) preservation by 6 months, with AAV5-ZFN:AAV5-RHO ratios of 1:1 and 1:2 maintaining ONL thickness above the preservation threshold. In the non-human primate retina, the fraction of HITI-edited rod photoreceptors exceeded the 20% therapeutic correction threshold in the successfully treated individual. ConclusionsThese findings support the advancement of this therapeutic vector to first-in-human trials as a mutation-agnostic insertion therapy applicable to all patients with RHO-adRP, irrespective of the specific causative variant.

Oligonucleotide based therapeutics continue to rise as a significant class of medicines for the treatment of human disease. However, achieving delivery to non-hepatic tissues remains a challenge in the field. While substantial advances have been realized, largely through the use of antibody or protein based targeting agents to tissues including muscle and the CNS, these large protein agents present complications in synthesis and carry the potential for immune responses. In an effort to identify a simpler, smaller and robust means of delivery, we have generated and evaluated aptamers targeting the human transferrin receptor (hTfR) for the delivery of both ASO and siRNA cargoes to muscle. Using a fully backbone modified anti-TfR aptamer, 36 nt in length, that binds hTfR and does not compete for binding with the natural ligand, transferrin, we evaluated the ability to deliver ASOs to skeletal muscle following systemic delivery. Using optimized linker chemistry, aptamer-ASO conjugates led to >50% target gene knockdown in muscle tissue for up to 42 days following a single dose at 3 mg/kg ASO ([~]11 mg/kg total drug) in mice. Taken as a whole, these results offer significant promise for the use of aptamers in the development of future therapeutics.

Personalized neoantigen vaccines are an emerging strategy for cancer immunotherapy, but their effectiveness depends on selecting tumor-specific antigens capable of inducing functional T-cell responses. The VACINUS AI-informed neoantigen prioritization framework previously identified and peptide-validated three immunogenic Tier 1 neoantigens in the B16F10 melanoma model. In this study, we extended that framework by translating these validated neoantigens into a multi-epitope messenger RNA vaccine formulated with lipid nanoparticles and evaluating its preclinical immunogenicity and antitumor activity. The three VACINUS-prioritized B16F10 neoantigens were encoded within a single multi-epitope construct, BF-V1_27-Ser, and formulated to generate BF-RNA-P. In B16F10 tumor-bearing mice, BF-RNA-P induced neoantigen-specific CD8+T-cell responses, with the strongest response directed against the B16F10-1-4 epitope. Combination with anti-PD-1 further enhanced vaccine-induced CD44+IFN-{gamma}+ CD8+ T-cell activation, whereas anti-PD-1 alone did not induce detectable peptide-specific responses. BF-RNA-P also suppressed tumor growth in vivo, and combination treatment produced the strongest antitumor effect, reflected by reduced tumor volume and lower endpoint tumor burden. Together, these findings demonstrate that VACINUS-prioritized and peptide-validated neoantigens can be reformatted into a multi-epitope messenger RNA/lipid nanoparticle vaccine while retaining antigen-specific immunogenicity and antitumor activity. This study provides preclinical proof-of-concept for integrating AI-informed, TCR-aware neoantigen prioritization with messenger RNA/lipid nanoparticle delivery as a translational strategy for personalized cancer vaccine development.

BackgroundBiallelic loss-of-function mutations in PRKN gene (encoding Parkin protein) cause early-onset Parkinsons disease (EOPD). Parkin is a crucial component of PINK1-Parkin pathway, which marks damaged mitochondria for degradation via mitophagy. Without functional Parkin, damaged mitochondria accumulate, causing oxidative stress and neurodegeneration. ObjectiveInvestigate Parkin gene replacement via AAV gene therapy as a potential treatment for Parkin-dependent EOPD. MethodsWe initially validated phosphorylated ubiquitin Ser65 (pUbSer65) as an indicator of Parkin-mediated mitophagy initiation. We evaluated AAV-mediated PRKN replacement (hereafter, AAV-Parkin) in a Parkin knockout neuroblastoma cell line (SH-SY5Y cells) and feasibility of delivery in mouse and rat models. ResultsOur research showed pUbSer65 signal was reduced in Parkin-KO SH-SY5Y cells when compared to wild-type cells after mitochondrial stress, indicating deficiency in initiation of mitophagy. AAV-mediated human PRKN gene replacement successfully restored these pUbSer65 levels in knockout cells. We saw restoration in patient-derived fibroblasts following AAV-Parkin overexpression. We developed a translatable gene therapy approach using rodents. We demonstrated the feasibility of delivering AAV-Parkin directly into the substantia nigra (SN) of wild-type rats. Using an AAV1 capsid with Ef1a promoter, we achieved dose-dependent Parkin expression and identified a well-tolerated dose. We also evaluated multiple promoters in a proprietary Spark100 capsid, finding Ef1a and Synapsin1 (Syn1) were most effective for transducing dopaminergic neurons in the SN of mice without causing adverse effects. These findings established a well-tolerated vector dose and an optimal capsid-promoter combination. ConclusionsOur results support the potential of AAV-Parkin gene therapy as a disease-modifying approach for Parkin-deficient EOPD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/737487v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@16dd13corg.highwire.dtl.DTLVardef@c3dfcdorg.highwire.dtl.DTLVardef@19a310dorg.highwire.dtl.DTLVardef@a66f2_HPS_FORMAT_FIGEXP M_FIG C_FIG

Huntingtons disease (HD), caused by a CAG repeat expansion in the huntingtin (HTT) gene, is characterized by progressive neurodegeneration and accumulation of DNA damage with multiple disease-modifier genes involved in DNA repair pathways. Previous studies have implicated ataxia telangiectasia mutated (ATM) signaling in the regulation of genomic stability and DNA damage repair (DDR) pathways in HD. ATM has also been linked to the WW domain-containing oxidoreductase (WWOX), a protein involved in DNA repair and maintenance of genomic stability, through the E3 ubiquitin ligase ITCH. However, whether this signaling pathway contributes to HD pathogenesis remains unknown. Here, we investigated the role of ATM-ITCH-WWOX signaling in HD. Our results revealed no significant alterations in total ATM, phosphorylated ATM (pATM-S1981), or ITCH in HD post-mortem prefrontal cortex (PFC) compared to controls. Although treatment of human neuroblastoma SH-SY5Y cells with HD PFC lysates did not alter pATM-S1981 levels, it increased histone H2AX phosphorylation at S139 ({gamma}-H2AX), a marker of DNA double-strand breaks. This finding suggested the presence of persistent DNA damage signaling independent of canonical ATM activation. Conversely, WWOX levels were increased in both HD PFC and HD embryonic stem cell-derived cortical neurons. Additionally, treatment of SH-SY5Y cells with recombinant human WWOX protein or WWOX overexpression increased {gamma}-H2AX levels, supporting a role for WWOX in promoting DNA damage. To determine whether WWOX contributed to DNA damage in HD, SH-SY5Y cells were treated with HD PFC lysates that were depleted of WWOX. Immuno-depletion of WWOX reduced the ability of HD PFC lysates to increase {gamma}-H2AX, suggesting that WWOX contributes to DNA damage in HD. Finally, overexpression of WWOX in RPE1-AAVS1-CAG115 cells did not affect somatic CAG repeat instability, despite persistent increases in {gamma}-H2AX levels. Collectively, our findings identify WWOX as a contributor to DNA damage in HD, acting independently of the ATM pathway.

Ischemic stroke remains a leading cause of death and disability, and current reperfusion therapies do not address the secondary neuroinflammatory response following blood-brain barrier (BBB) disruption. Purinergic signaling critically regulates this process: extracellular ATP promotes inflammation, whereas its enzymatic conversion into adenosine exerts tissue-protective effects. Notably, the ectonucleotidase CD73 (NT5E), which catalyzes AMP-to-adenosine conversion, is highly expressed by human but not murine brain endothelial cells (BECs). Here, we investigated the role of endothelial CD73 in ischemic stroke using an AAV vector engineered for selective transduction of murine BECs to induce BBB-specific CD73 expression. Endothelial CD73 enhanced extracellular ATP degradation toward adenosine generation and established a purine metabolism profile resembling that of human BECs. In the transient middle cerebral artery occlusion (tMCAO) mouse model, BBB-targeted CD73 expression reduced infarct volume by 40% and prevented early mortality within 48 h after reperfusion. Transcriptomic and flow cytometric analyses revealed altered leukocyte responses, including increased recruitment of monocytes/macrophages whose gene expression signatures were consistent with inflammation-resolving programs. These findings identify endothelial CD73 as an important regulator of post-ischemic neuroinflammation and highlight species-specific differences in BBB purine metabolism with implications for translational stroke research.

RNA interference (RNAi) therapeutics enable selective silencing of disease-associated genes. Yet, their clinical application remains largely confined to the liver due to extrahepatic delivery constraints of current platforms such as GalNAc conjugates and lipid nanoparticles. Extracellular vesicles (EVs) offer an attractive alternative delivery strategy owing to their biocompatibility, ability to traverse biological barriers, and amenability to engineering. However, EV-mediated RNA delivery is limited by inefficient endogenous RNA loading and poor cytosolic release following uptake. Here, we establish a modular EV-based platform that addresses both challenges by integrating enhanced endogenous shRNA loading with fusogen-mediated cytosolic delivery. Using Argonaute 2 (AGO2)-assisted loading, we substantially increase shRNA copy numbers per vesicle (up to 3.7 copies/EV) and enable quantitative, molecule-resolved assessment of delivery potency. Engineered EVs achieve robust and reproducible shRNA-mediated gene silencing with picomolar IC50 values across multiple cell types and induce significant target knockdown in the mouse brain following intracerebral administration. Together, these findings demonstrate that coordinated engineering of shRNA loading and cytosolic release can overcome key limitations of EV-mediated small RNA delivery.

Chimeric antigen receptor (CAR)-T cell therapies have transformed the treatment of various tumor types by redirecting and activating T cells against tumor cells. However, CAR-T cell manufacturing approaches remain challenging and limit their widespread use in clinical settings. In vivo CAR-T therapy bypasses ex vivo cell manufacturing and patient preconditioning limitations; however, it faces a significant safety concern as CAR proteins on viral packaging cells are incorporated into budding virions, leading to off-target transduction of tumor cells. Here, we address this risk by developing the CAR-Less ER-Anchor Vector (CLEAN-V) system. By exploiting endoplasmic reticulum (ER) retention, CLEAN-V prevents the CAR protein from trafficking to the cell surface during viral packaging, thereby blocking its incorporation into the viral envelope. CLEAN-V particles exhibit near-complete loss of CAR-mediated tumor cell transduction. Furthermore, CLEAN-V integrates seamlessly into existing third-generation LVV workflows in four- or five-plasmid formats and generates CAR-T cells with preserved phenotypic and functional integrity. These results establish CLEAN-V as a robust platform for developing safe, targeted lentiviral vectors for in vivo CAR-T therapy.

Parkinson's disease (PD) is characterized by progressive DAergic neurodegeneration and the accumulation of aggregated -Synuclein (Syn), which drives chronic neuroinflammation through sustained activation of innate and adaptive immune responses. Regulatory T cells (Tregs) exert potent immunosuppressive functions and have shown neuroprotective effects in preclinical PD models; however, clinical translation of polyclonal Treg therapies has been limited by poor tissue specificity and insufficient therapeutic efficacy. To overcome these limitations, we engineered induced human Tregs (iTregs) expressing chimeric antigen receptors (CARs) directed against pathological Syn aggregates. Among the CAR designs tested, only a nanobody-based construct incorporating NbSyn87 displayed selective antigen-dependent activation in response to Syn preformed fibrils (PFFs). Intriguingly, despite the ability of the parental NbSyn87 nanobody to bind both monomeric and aggregated Syn, incorporation into the CAR architecture conferred functional selectivity for aggregated conformers. This feature enabled discrimination between pathological extracellular aggregates and physiological monomeric Syn, providing an important safety advantage. To evaluate therapeutic activity in vivo, we established an immunodeficient mouse model of synucleinopathy permissive to human cell engraftment. iTregs preferentially accumulated within Syn-rich brain regions and, in the presence of astrocyte-derived human IL-2 with antigen-independent mechanism. Conversely, only CAR iTregs directed against Syn significantly reduced microglial and astrocytic activation, decreased pro-inflammatory cytokine expression, and attenuated Syn pathology. Collectively, these findings demonstrate that Syn-specific CAR iTregs can selectively exert potent local immunomodulatory effects, establishing a promising antigen-specific cellular immunotherapy platform for PD and other synucleinopathies.

Human Immunodeficiency Virus (HIV)-1 broadly neutralizing antibodies (bNAbs) have demonstrated clinical efficacy, but face manufacturing challenges associated with recombinant protein production and purification. Here, we present a ribonucleic acid (RNA)-encoded bNAb (RibobNAb) platform that enables in vivo antibody production of the clinically validated bNAb PGT121 via lipid nanoparticle (LNP) delivery, supporting rapid evaluation of Fc variants (LS, del294, LS-del294) in vitro and in vivo. We confirmed expression, sub-nanomolar HIV-1 Env binding, and potent neutralization across all RibobNAb variants in vitro. In mice, single RNA-LNP administrations yielded in vivo expression of all RibobNAb variants, with PGT121-LS exhibiting a prolonged half-life compared with PGT121. In non-human primates (NHPs), a single intravenous administration of PGT121-LS RNA-LNP was well tolerated without anti-drug antibody (ADA) formation over 180 days and resulted in PGT121-LS half-lives comparable to the reference protein. Single intramuscular administration showed RibobNAb expression but resulted in ADA development from Day 14 onwards and lower bioavailability. In vivo-expressed PGT121-LS RibobNAb retained identical antiviral functionality to PGT121-LS reference protein. An NHP pharmacokinetics model integrating RNA transfection and translation dynamics enabled allometric scaling and first-in-human dose prediction. We highlight RibobNAbs as an alternative to conventional purified protein antibodies for rapid development of bNAb-based therapeutic strategies.

Ex vivo genome editing of human hematopoietic stem and progenitor cells (HSPCs) requires targeted integration strategies that support large therapeutic DNA payloads while preserving stem cell fitness. Although CRISPR/Cas9-mediated homology-directed repair using AAV donors is effective, it is constrained by limited cargo capacity and adverse effects on long-term HSPCs function. Integrase-defective lentiviral vectors (IDLVs) offer an alternative donor platform, yet their precise and controlled genomic integration remains inefficient. Here, we describe TILV (Targeted Integration of Lentiviral Vector), a CRISPR-assisted knock-in strategy that exploits Cas9-mediated linearization of episomal IDLV DNA to expose a single homology arm and engage homology-mediated end-joining repair pathways. TILV enables precise, directional and seamless integration of transgenes in multiple loci, enabling constitutive or physiological expression. Using single-cell clonal analyses and targeted long-read sequencing, we define the molecular features of TILV-mediated integration and demonstrate preferential use of CRISPR-linearized episomal substrates. TILV supports accurate insertion of large therapeutic transgenes, without compromising HSPC viability or multilineage potential. We further show that transient modulation of DNA repair pathway, in combination with extended homology arms, enhances integration efficiency and junctional precision. Importantly, optimized TILV enables targeted integration in phenotypically defined long-term HSPCs, highlighting its potential for scalable and durable gene therapy.

Gene therapy has been the subject of extensive research following the advent of gene-editing technologies. Genetic disorders with difficult-to-target tissues, such as cystic fibrosis (CF), still face many challenges in developing efficacious gene therapy. The potential universal approach of gene replacement involves inserting a functional CFTR gene after generating DNA double strand breaks using gene editors such as CRISPR/Cas9. However, this strategy has not achieved clinical significance, as CRISPR/Cas9-mediated integration of CFTR is limited primarily by the infrequent activity of the homology-directed repair (HDR) pathway. To circumvent this limitation and improve CFTR transgene integration and expression, we explored a method of adding a second integration site, which we termed the dual-locus-targeting method. Using a helper-dependent adenoviral vector (HDAd)-delivered CRISPR/Cas9 system in porcine epithelial cells, we found that sequential delivery of two vectors, one targeting the CFTR locus and the other the genomic safe harbour site GGTA1, enhanced the integration efficiency of lacZ and CFTR donor genes to 16.5% and 3.4%, respectively. These results demonstrated a potential strategy to improve the efficacy of CFTR replacement for the development of a universal and permanent gene therapy treatment for CF lung disease. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/731381v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@1774590org.highwire.dtl.DTLVardef@1782915org.highwire.dtl.DTLVardef@1d13b12org.highwire.dtl.DTLVardef@17d3f93_HPS_FORMAT_FIGEXP M_FIG C_FIG

A challenge of "once-and-done" adeno associated virus (AAV)-based gene therapy is the inability to modulate the level of therapeutic protein expression post-administration. Herein, we demonstrate the utility of an adenosine deaminase acting on RNA (ADAR) - mediated gene switch to control AAV-delivered gene expression. Using a premature termination codon (PTC) in the human Factor IX (hFIX) transgene, we established an ON switch, where expression of hFIX is contingent on rescuing the PTC mutation via RNA editing. In vitro and in vivo studies demonstrated silencing of the hFIX transgene by the PTC mutation and induction of protein expression by administration of an ADAR-recruiting trigger RNA. Mice transduced with a hepatotropic AAV capsid encoding an ApoE-hAAT hFIX-PTC transgene expression cassette showed a dose-dependent response between the levels of LNP-delivered trigger RNA and the amount of plasma hFIX expression achieved. We observed predictable and reproducible levels of hFIX expression upon multiple rounds of RNA editing and demonstrated that this system can achieve clinically relevant levels of hFIX. This work suggests that ADAR-mediated RNA editing may be a valuable tool for tunable expression of therapeutic transgenes in applied gene therapies.

Microglia play key roles in brain development, homeostasis, and neurodegeneration. Although multiple strategies for viral gene delivery to microglia have been reported, they have not been directly compared. Here, we developed microglia-targeting AAV capsids and benchmarked them against existing approaches. The novel capsids exhibit improved transduction efficiency in cultured mouse and human microglia, as well as neurons and astrocytes. However, when we compared microglial transduction efficiency of the novel capsids with published engineered and naturally occurring capsids after intracranial injection, all capsids achieved efficient and specific transduction when paired with a genome incorporating IBA1 promoter and miR-124 target sites. In contrast, CAG promoter did not support efficient microglial transduction. Moreover, blood-brain barrier- crossing capsids carrying IBA1 promoter and miR-124 target sites efficiently transduced microglia at high doses but exhibited off-target expression. Together, our work provides improved capsids for in vitro manipulation of microglia and establishes viral genome design, not capsid identity, as the principal determinant of efficient in vivo microglial targeting.

Proteostasis impairment at the level of the endoplasmic reticulum (ER) is a salient feature of Alzheimers disease (AD). The unfolded protein response (UPR) is the main pathway to cope with ER stress, where the expression of the transcription factor X-Box binding protein 1 (XBP1) is central to establish repair programs. To artificially enforce the adaptive capacity of the UPR in the AD brain, we recently reported the protective effects of overexpressing active XBP1 in the brain using adeno-associated vectors (AAVs) of AD mice, in addition to aged animals. Here we have generated a next generation vector suitable for clinical testing by (i) expressing codon-optimized human XBP1s without artificial tags, (ii) the use of the synapsin promoter to restrict expression to neurons, and (iii) incorporating a novel variant of AAV2 (AAV-TT) with greater biodistribution (here termed Proteostaser-1). Treatment of 5xFAD mice with Proteostaser-1 improved spatial learning and synaptic plasticity, and reduced the deposition of amyloid plaques in the brain. Proteostaser-1 administration also improved cognition in a model of sporadic AD based on the intracerebral injection of amyloid {beta} oligomers. Our results further support the therapeutic potential of the UPR as a strategy to ameliorate AD features and sustain synaptic function.

Sustained trophic factor delivery via Encapsulated Cell Technology (ECT) is a powerful new class of therapeutics with broad potential for targeted treatment. Intravitreal delivery of ciliary neurotrophic factor (CNTF) via the ECT, NT-501, is a first-in-class therapy that slows the progression of macular telangiectasia type 2 (MacTel). Despite its clinical efficacy, key questions remain regarding its mechanism of action, including whether other implant-derived factors contribute to therapeutic benefit and how optimal dosing should be determined. Resolving these issues is critical for optimizing NT-501 in MacTel and guiding the development of ECT-based therapies for other diseases. We evaluated the biological activity of implant-derived cytokines on retinal tissue, using long-term NT-501 intravitreal implants in rabbits alongside human retinal organoid (hRO) models treated with NT-501-conditioned medium (NT-501-CM). Then, using a MacTel-specific photoreceptor degeneration model in hROs, we showed NT-501-CM significantly reduced photoreceptor cell death, and this protective effect was abolished by either CNTF-neutralizing antibodies or JAK inhibitor. We also established a therapeutic dose-response relationship linking NT-501-derived CNTF levels to JAK/STAT3 activation and photoreceptor protection. These findings directly connect ECT-derived CNTF exposure with JAK/STAT3-mediated photoreceptor protection in human retinal tissue and suggest an optimal concentration range for efficacy.