CMN Weekly (30 September 2022) - Your Weekly CRISPR Medicine News

Top picks

• mRNA is frequently modified by N⁶-methyladenosine (m6A) to regulate biological processes. Now, Chinese researchers have demonstrated a method for CRISPR-dCas13a-based RNA m6A-editing. The method can target RNAs using single or multiple CRISPR RNA (crRNA) arrays to methylate or demethylate m6A in human 293T cells and mouse embryonic stem cells. The method's efficacy was demonstrated by modulation of X chromosome silencing and activation by modulating m6A levels on the non-coding XIST transcript.
• American researchers have performed CRISPR prime editing with separated, rather than fused, nSpCas9 and Moloney murine leukaemia virus reverse transcriptase (MMLV-RT) proteins. They show that the separated proteins function as efficiently as intact PE2 in human cells. In addition, the authors argue that split-prime editors can address the limitations of size-constrained AAV vectors.

Research

• A new multifunctional non-viral vector can efficiently target tumour cells and deliver CRISPR-Cas9 plasmids into nuclei of cancer cells for non-small cell lung cancer therapy. Plasmid DNA was condensed with protamine sulfate, coated with liposome and further modified with hyaluronic acid for nuclei-targeting, degradation avoidance and tumour cell targeting. The efficacy of the delivery system was demonstrated by the disruption of the MTH1 (mutT homolog1) gene, leading to growth inhibition of non-small cell lung cancer cells.
• Chinese researchers have assessed and compared the gene editing outcomes of the recently developed CRISPR-Cas12f nuclease to that of Cas9 and two Cas12a proteins at multiple genomic sites. The study finds that while Cas9 and Cas12a show relatively higher editing efficiency at the vast majority of the tested sites, the off-target hotspots identified with these nucleases are negligibly detected in the Cas12f-edited cells.
• The MALAT1 gene is suggested as a new tumour biomarker and therapeutic target with the CRISPR-Cas9 technique in prostate cancer (PC). MALAT1 is highly expressed in PC cells, and its knockout in DU-145 human prostate cancer cells increases apoptosis and prevents the proliferation and migration of cancer cells.
• American researchers have designed a series of endogenous testbed systems to quantify and compare the genome editing, CRISPRi, and CRISPRa capabilities among ten natural and engineered Cas protein variants. They find a hierarchy for genome editing and CRISPRa applications, wherein Cas9 ≥ Cas12a > Cas12e/Cas12j.

Industry

• Scribe Therapeutics and Sanofi have signed a strategic partnership to expedite the development of breakthrough CRISPR-based cell therapies for cancer. The alliance will leverage Scribe's CRISPR genome editing technologies for new natural killer (NK) cell cancer therapeutics. According to the deal, Scribe will receive an upfront payment of $25m and be entitled to receive potential payments worth over $1bn on meeting development and commercial milestones.
• CRISPR Therapeutics has been granted FDA regenerative medicine advanced therapy (RMAT) designation to CTX130 for treating cutaneous T-cell lymphomas (CTCL). CTX130 is a healthy donor-derived gene-edited allogeneic CAR T investigational therapy targeting CD70, an antigen expressed on various solid tumours and hematologic malignancies.
• CRISPR Therapeutics and Vertex Pharmaceuticals have announced that FDA has granted exa-cel - an autologous, ex vivo CRISPR-Cas9 gene-edited therapy for sickle cell disease and transfusion-dependent beta-thalassemia - a rolling review. Exa-cel edits a patient's hematopoietic stem cells to produce high fetal haemoglobin levels (HbF) levels in red blood cells.
• Arsenal Biosciences and Genentech have announced a multi-year collaboration. ArsenalBio's proprietary technology for high-throughput screening and engineering T cells will be deployed to identify critical success circuits in T cell-based therapies. Arsenal will receive $70 million in upfront payments along with research, development, and commercial milestones.
• Excision BioTherapeutics announced that the California Institute for Regenerative Medicine (CIRM) has awarded the company a $6.85 million grant. The grant will support the clinical development of the EBT-101 program for human immunodeficiency virus type 1 (HIV-1). Excision recently reported that the first participant in the EBT-101 Phase 1/2 clinical trial was dosed in July 2022, with initial findings indicating the therapeutic has been well tolerated.
• NanoSyrinx has been named the winner of the 2022 AbbVie UK Golden Ticket accelerator programme - a competitive award open to early-stage life sciences companies and biotech start-ups developing cutting-edge therapies or technology platforms. NanoSyrinx is built around an entirely genetically encoded drug delivery system, using naturally occurring 'nanosyringes'.
• Sherlock Biosciences has been named the Medical Device/Diagnostics Company of the Year by PM360, a leading trade magazine for marketing decision-makers in the pharmaceutical, biotech, medical device, and diagnostics industries.

Detection

• Spanish scientists have developed a reverse transcription-loop-mediated isothermal amplification (RT-LAMP)-CRISPR-Cas13a method for SARS-CoV-2 detection in nasopharyngeal samples without using RNA extraction. The technique exhibits 100% specificity and 83% sensitivity, and a positive predictive value (PPV) of 100%.
• Chinese researchers have developed a fluorescence biosensor for detecting miRNAs based on double amplification reactions with the primer exchange reaction (PER) and CRISPR/Cas12a. The new biosensor could detect miRNA-21 at a lower limit of 10 FM and had low detection cost, simple operation, and mobility.
• Researchers in China have combined CRISPR with surface-enhanced Raman scattering to detect the drug resistance gene macB in bovine raw milk. The method does not require nucleic acid amplification or other complex steps and may be effective for improving food hygiene.

Reviews

• American researchers have reviewed recent advances in understanding the structural mechanisms of two miniature Cas endonucleases, Cas12f and Cas12j. The authors discuss overall architecture, target searching and DNA unwinding, guide RNA processing and cleavage efficiencies, and specificities of the two nucleases.
• Indian researchers have published another review comparing Cas nucleases. They provide details and mechanisms of all Cas proteins, including Cas9, Cas12, Cas13, and Cas14, discovered so far. They also discuss the pros, cons, and recent applications of various Cas proteins in diverse fields.
• Researchers in India discuss using so-called nanourchins as a delivery system for CRISPR reagents and other drugs. Nanourchins are multibranched nanoparticles with surface spikes that make them resemble sea urchins.
• A review by Chinese researchers discusses genome-editing applications in human pluripotent stem cells for cardiac disease therapy. The study includes zinc finger nucleases (ZNF), transcription activator-like effector nucleases (TALEN), and CRISPR-Cas9.

Opinion and comments

• A paper in the Journal of Bioethical Inquiry discusses the ethics of using human germline editing for enhancement purposes. The author supports Habermas's argument from human nature that discourages human germline editing and argues that objections to its supposedly genetic essentialist and determinist framework originate from an instrumentalist reading of Habermas's view.

News from CRISPR Medicine News

• This week's feature article explained how CRISPR knockout of a chromatin remodelling factor could reverse T cell exhaustion. In addition, an interview with researchers in the U.S. describes how they recently shed much-needed light on the molecular mechanisms underpinning T cell exhaustion, revealing an epigenetic regulator as a critical target for improving T cell therapies for cancer.