CMN Weekly (28 November 2025) - Your Weekly CRISPR Medicine News

Top picks

• CRISPR-Cas9 nickase targeted to CAG/CTG repeats was used to achieve efficient contractions in Huntington's disease and myotonic dystrophy type 1 patient-derived neurons and astrocytes, with the approach proving allele-selective and free of detectable off-target mutations. Striatal injection of the Cas9 nickase via adeno-associated viral vectors in a Huntington's disease mouse model led to contractions in over half the infected cells, reducing inclusion bodies, improving transcriptomic profiles, and ameliorating locomotion – effects greater than expected from the contractions alone, suggesting that non-cell-autonomous mechanisms may contribute.
• Through systematic engineering of the CRISPR-associated IscB protein DelIscB and its sgRNA, researchers generated enDelIscB with 48.9-fold increased activity that recognises a flexible NAC TAM sequence, compared to the complex NWRRNA TAM required by OgeuIscB. Fusion of enDelIscB with T5 exonuclease, cytosine deaminase or adenosine deaminase created efficient miniature genome-editing tools (enDelIscB-T5E, ICBE and IABE) that successfully generated mouse models following embryo microinjection, with enDelIscB's compact size offering advantages for in vivo delivery.

Research

• Manipulating in vitro salt concentrations enabled mapping of cleavage preferences for chimeric gene editors comprising I-TevI nuclease domain fusions to CRISPR nucleases, with low salt buffers decoupling DNA cleavage by the I-TevI domain at CNNNG sites from gRNA-targeted sites. For TevCas12a, non-targeted cleavage was enriched at Tev CNNNG motifs within a 30-bp window upstream of Cas12a TTTV PAM sites, with similar non-targeted products observed for TevSaCas9, Tev-meganuclease and Tev-zinc finger editors, highlighting how reaction conditions can functionally dissect chimeric gene editor activity.
• A CRISPR-Cas9 approach enabled single-edit insertion of the inducible caspase9 (iCasp9) suicide gene alongside either a reporter gene or a tumour antigen-specific single-chain immunoglobulin cassette at the IgH locus in B-cells, preserving B-cell functionality whilst hijacking antigen specificity. Activation of iCasp9 with the drug AP1903 efficiently induced apoptosis in edited cells, both in vitro and in established tumours in immunodeficient animals. However, resistant cells with reduced iCasp9 and therapeutic antibody expression consistently emerged following treatment, suggesting that the safety switch could serve as neoadjuvant therapy or as a rheostat to modulate therapeutic-molecule infusion in adoptive immunotherapy.
• Using CRISPR-Cas9 technology, researchers have created four humanised mouse models carrying human DMD gene deletions of exon 44, 45, 51 or 53 in a dystrophin-deficient background, efficiently generating models that develop typical muscular dystrophy pathology. Intramuscular treatment with vivo-morpholinos successfully induced exon skipping and restored dystrophin expression, validating these models for preclinical testing of human sequence-specific therapies for Duchenne muscular dystrophy.
• French and Italian researchers published a gene-editing strategy using adenine base editors to precisely repair two of the most common severe β-thalassaemia mutations, restoring adult haemoglobin production in patient blood stem cells. The work reports high correction rates alongside an encouraging safety profile, potentially extending mutation-specific therapy to more than 40% of transfusion-dependent β-thalassaemia patients in France who carry these variants. Also, read our take on the findings.
• Researchers have identified FZD6 as a promising therapeutic target for advanced prostate cancer through systematic screening of Wnt receptors, revealing that its inhibition creates exploitable vulnerabilities that can be targeted with specific kinase inhibitors. A comprehensive screen across the entire human kinome demonstrated that FZD6 knockdown sensitises prostate cancer cells to PKMYT1 inhibition.
• CRISPR-Cas9-mediated knockout of AKT1 in HT-1080 cells, validated through Sanger sequencing and InDel analysis, significantly reduced AKT1 mRNA and protein expression and altered the expression of downstream effectors mTOR, BCL-2 and FOXO1. The findings highlight the impact of AKT1 disruption on cellular signalling pathways and provide insights into the regulatory role of this serine/threonine kinase gene.
• By including introns in Cas9 expression cassettes, silencing across multiple cell lines was significantly reduced. T-rich introns over 2 kb conferred the greatest protection, and incorporation of an intron into a CRISPRa construct resulted in reduced silencing, increased expression levels and markedly enhanced target gene activation. Introns worked synergistically with chromatin-opening elements to further mitigate silencing, suggesting regulatory mechanisms acting at both the DNA and RNA levels and offering an approach to optimise genetic constructs for improved cellular engineering that requires constitutive expression of large transgenes.

Industry

• Manus has launched a licensing programme for MAD7™, a CRISPR-Cas nuclease with high on-target precision and reduced off-target activity. Featuring a TTTN PAM, MAD7 expands genomic targeting beyond SpCas9. Now, under Manus' platform post-merger with Inscripta, it's offered via flexible, cost-effective licences to support diverse CRISPR R&D across microbial, plant, and mammalian systems.

Delivery

• A new modular system for delivering Cas9 ribonucleoprotein complexes uses extracellular vesicles, exploiting the high-affinity binding between MS2 coat proteins fused to EV-enriched proteins and MS2 aptamers incorporated into guide RNAs, combined with a UV-activated photocleavable linker. The versatile platform successfully delivered not only Cas9 but also alternative variants, including the transcriptional activator dCas9-VPR and adenine base editor ABE8e, offering a robust approach for CRISPR-Cas9-based genetic engineering and transcriptional regulation.
• A cost-effective mechanoporation system using micro-engineered filters delivered CRISPR-Cas9 plasmid DNA targeting Fkbpl into trophoblast cells, generating clones with 38% knockout efficiency that showed significantly reduced migration and proliferation, modelling preeclampsia pathogenesis. Treatment with mesenchymal stem cell-derived small extracellular vesicles failed to restore migratory capacity or proliferation in Fkbpl-deficient cells despite enhancing wild-type cell proliferation, suggesting FKBPL mediates the therapeutic effects of MSC-sEVs in trophoblasts.

Screening

• A genome-wide CRISPR knockout screen in lipopolysaccharide-treated human myeloid U937 cells identified 295 genes regulating interleukin-1β production, including TNRC18, linked to inflammatory diseases in the Finnish population. U937 cells engineered with the Finnish-enriched rs748670681 risk allele showed decreased TNRC18 and WIPI2 expression, with knockouts revealing TNRC18 modulates inflammatory responses through H3K27 acetylation, whilst WIPI2 loss exacerbates interferon signalling.
• Bulk and single-cell CRISPR screens in primary cardiac fibroblasts identified chromatin factors, including Srcap and Kat5, as potent regulators of myofibroblast differentiation, with these factors required for collagen synthesis and cell contractility. Chromatin profiling revealed that pro-fibrotic chromatin complexes facilitate the activity of pro-fibrotic transcription factors, and KAT5 inhibition alleviated fibrotic responses in patient-derived human fibroblasts, suggesting therapeutic potential for cardiac fibrosis.

Detection

• A thermally regulated asynchronous CRISPR-enhanced (TRACE) assay enables rapid, sensitive detection of multiple DNA targets in a streamlined one-pot format, achieving a limit of detection of 2.5 copies/test – 40 times lower than that of canonical one-pot CRISPR approaches. When applied to clinical samples, TRACE demonstrated 99.5% accuracy across diverse sample types, detecting monkeypox virus within 11 minutes with performance comparable to qPCR but fivefold faster report times, whilst enabling simultaneous detection of pathogen and host genes to address the lack of internal controls in current CRISPR diagnostics.

Perspectives

• A new framework proposes a pragmatic approach to assessing CRISPR-Cas off-target risks, acknowledging that zero off-target edits is unrealistic. It advocates weighing off-target consequences against disease severity and therapeutic benefit, using current and emerging tools. The goal is to enable more informed, balanced safety assessments and accelerate clinical translation of CRISPR therapies.

Reviews

• CRISPR/Cas-editing technologies for viral-mediated gene therapies of human diseases: mechanisms, progress and challenges. This review examines how viral vectors, particularly AAV and lentiviral platforms, are being leveraged to deliver CRISPR-Cas therapeutics, outlining current clinical progress and persistent challenges in developing next-generation gene editing interventions.
• Epigenetic editing: from concept to clinic. This review explores how CRISPR-Cas–guided epigenetic editing is being developed to reprogramme gene expression via targeted chromatin modifications, assessing progress, limitations, and emerging strategies to achieve durable, disease-relevant regulation.