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Gene-editing technologies, which include the CRISPR–Cas nucleases1–3 and CRISPR base editors4,5, have the potential to permanently modify disease-causing genes in patients6. The demonstration of durable editing in target organs of nonhuman primates is a key step before in vivo administration of gene editors to patients in clinical trials. Here we demonstrate that CRISPR base editors that are delivered in vivo using lipid nanoparticles can efficiently and precisely modify disease-related genes in living cynomolgus monkeys (Macaca fascicularis). We observed a near-complete knockdown of PCSK9 in the liver after a single infusion of lipid nanoparticles, with concomitant reductions in blood levels of PCSK9 and low-density lipoprotein cholesterol of approximately 90% and about 60%, respectively; all of these changes remained stable for at least 8 months after a single-dose treatment. In addition to supporting a ‘once-and-done’ approach to the reduction of low-density lipoprotein cholesterol and the treatment of atherosclerotic cardiovascular disease (the leading cause of death worldwide7), our results provide a proof-of-concept for how CRISPR base editors can be productively applied to make precise single-nucleotide changes in therapeutic target genes in the liver, and potentially in other organs. In a cynomolgus macaque model, CRISPR base editors delivered in lipid nanoparticles are shown to efficiently and stably knock down PCSK9 in the liver to reduce levels of PCSK9 and low-density lipoprotein cholesterol in the blood.

As multiple genetic strategies advance through the clinic, important safety questions remain to be answered. As multiple genetic strategies advance through the clinic, important safety questions remain to be answered.

After finally gaining traction as a potential treatment for certain genetic disorders, gene therapy tackles the challenge of sickle-cell disease. After finally gaining traction as a potential treatment for certain genetic disorders, gene therapy tackles the challenge of sickle-cell disease.

DNA or RNA molecules, arranged into spherical shapes, can attack brain cancers and other illnesses that evade conventional drug design. DNA or RNA molecules, arranged into spherical shapes, can attack brain cancers and other illnesses that evade conventional drug design.

Various approaches are approved for treating blood cancers and a few rare disorders—they may soon become standard care. Various approaches are approved for treating blood cancers and a few rare disorders—they may soon become standard care.

Administering gene-editing treatment directly into the body could be a safe and effective way to treat a rare, life-threatening condition. Administering gene-editing treatment directly into the body could be a safe and effective way to treat a rare, life-threatening condition.

After three decades of false starts, gene therapy against the disease is in new clinical trials — and there is even hope of a cure. After three decades of false starts, gene therapy against the disease is in new clinical trials — and there is even hope of a cure.

Neuromuscular disorders are often caused by heterogeneous mutations in large, structurally complex genes. Targeting compensatory modifier genes could be beneficial to improve disease phenotypes. Here we report a mutation-independent strategy to upregulate the expression of a disease-modifying gene associated with congenital muscular dystrophy type 1A (MDC1A) using the CRISPR activation system in mice. MDC1A is caused by mutations in LAMA2 that lead to nonfunctional laminin-α2, which compromises the stability of muscle fibres and the myelination of peripheral nerves. Transgenic overexpression of Lama1, which encodes a structurally similar protein called laminin-α1, ameliorates muscle wasting and paralysis in mouse models of MDC1A, demonstrating its importance as a compensatory modifier of the disease1. However, postnatal upregulation of Lama1 is hampered by its large size, which exceeds the packaging capacity of vehicles that are clinically relevant for gene therapy. We modulate expression of Lama1 in the dy2j/dy2j mouse model of MDC1A using an adeno-associated virus (AAV9) carrying a catalytically inactive Cas9 (dCas9), VP64 transactivators and single-guide RNAs that target the Lama1 promoter. When pre-symptomatic mice were treated, Lama1 was upregulated in skeletal muscles and peripheral nerves, which prevented muscle fibrosis and paralysis. However, for many disorders it is important to investigate the therapeutic window and reversibility of symptoms. In muscular dystrophies, it has been hypothesized that fibrotic changes in skeletal muscle are irreversible. However, we show that dystrophic features and disease progression were improved and reversed when the treatment was initiated in symptomatic dy2j/dy2j mice with apparent hindlimb paralysis and muscle fibrosis. Collectively, our data demonstrate the feasibility and therapeutic benefit of CRISPR-dCas9-mediated upregulation of Lama1, which may enable mutation-independent treatment for all patients with MDC1A. This approach has a broad applicability to a variety of disease-modifying genes and could serve as a therapeutic strategy for many inherited and acquired diseases.

The safety and efficacy of genome editing in human embryos hasn’t been proven, researchers warn. The safety and efficacy of genome editing in human embryos hasn’t been proven, researchers warn.

This scientific partnership could fight everything from blood diseases to HIV. This scientific partnership could fight everything from blood diseases to HIV.

Deletion of the Hippo pathway component Salvador in mouse hearts with established ischaemic heart failure after myocardial infarction induces a reparative genetic program with increased scar border vascularity, reduced fibrosis, and recovery of pumping function. Previous work has shown that interfering with Hippo signalling during myocardial injury improves heart function in mice. Clinical outcomes of acute myocardial infarction in humans have improved as a result of better emergency care, but chronic heart failure, whereby the heart tissue undergoes pathological remodelling, remains a leading cause of death. James Martin and colleagues now show that the failing heart has a previously unrecognized capacity for repair. They show that blocking Hippo signalling can rescue established heart failure in mice. Deletion of the Hippo pathway component Salvador (Salv) or virus-mediated delivery of Salv short hairpin RNA when ischaemic heart failure is established can improve heart function in mice. The authors attribute the effect to the induction of a reparative genetic program, including increased expression of stress response genes and proliferative genes and preservation of mitochondrial quality control. Mammalian organs vary widely in regenerative capacity. Poorly regenerative organs, such as the heart are particularly vulnerable to organ failure. Once established, heart failure commonly results in mortality1. The Hippo pathway, a kinase cascade that prevents adult cardiomyocyte proliferation and regeneration2, is upregulated in human heart failure. Here we show that deletion of the Hippo pathway component Salvador (Salv) in mouse hearts with established ischaemic heart failure after myocardial infarction induces a reparative genetic program with increased scar border vascularity, reduced fibrosis, and recovery of pumping function compared with controls. Using translating ribosomal affinity purification, we isolate cardiomyocyte-specific translating messenger RNA. Hippo-deficient cardiomyocytes have increased expression of proliferative genes and stress response genes, such as the mitochondrial quality control gene, Park2. Genetic studies indicate that Park2 is essential for heart repair, suggesting a requirement for mitochondrial quality control in regenerating myocardium. Gene therapy with a virus encoding Salv short hairpin RNA improves heart function when delivered at the time of infarct or after ischaemic heart failure following myocardial infarction was established. Our findings indicate that the failing heart has a previously unrecognized reparative capacity involving more than cardiomyocyte renewal.

The medical regulatory authorities ride a wave of clinical studies for gene therapies. The medical regulatory authorities ride a wave of clinical studies for gene therapies.

Despite the continent being the epicentre of sickle-cell disease, too few Africans are included in genome-wide association studies. Despite the continent being the epicentre of sickle-cell disease, too few Africans are included in genome-wide association studies.

A condition that affects many people of African descent is finally meeting its therapeutic match. A condition that affects many people of African descent is finally meeting its therapeutic match.

Hopes were high for drugs designed to lower levels of a mutant protein, but development has stalled. Hopes were high for drugs designed to lower levels of a mutant protein, but development has stalled.

When conventional laboratory models fail, stem cells from squirrels, seals and other species can come to researchers’ aid. When conventional laboratory models fail, stem cells from squirrels, seals and other species can come to researchers’ aid.

A bacterial toxin has been found that allows DNA in a cellular organelle called the mitochondrion to be precisely altered. This development could help to combat diseases caused by mutations in mitochondrial DNA. A base editor for mitochondrial DNA.

Antisense oligonucleotides are providing researchers and patients with fresh hope of targeting the condition’s genetic cause. Antisense oligonucleotides are providing researchers and patients with fresh hope of targeting the condition’s genetic cause.

A one-off injection to reduce the risk of cardiovascular disease is now a prospect thanks to advances in gene editing. A one-off injection to reduce the risk of cardiovascular disease is now a prospect thanks to advances in gene editing.

Treatment restores immune-system function in young children with severe disorder. Treatment restores immune-system function in young children with severe disorder.

The research is promising, but a true cure for this painful condition could be years away. The research is promising, but a true cure for this painful condition could be years away.

Researcher and entrepreneur Luk Vandenberghe thinks he can transport genes into cells much more efficiently by improving the viral vectors that carry them. Researcher and entrepreneur Luk Vandenberghe thinks he can transport genes into cells much more efficiently by improving the viral vectors that carry them.

Cancelling out an illness before a child is born offers the most potential benefit. Cancelling out an illness before a child is born offers the most potential benefit.

Targeted approach could lead to an opioid-free way of treating chronic pain. Targeted approach could lead to an opioid-free way of treating chronic pain.

Researchers report early successes using genetic approaches to treat sickle-cell anaemia and β-thalassaemia. Researchers report early successes using genetic approaches to treat sickle-cell anaemia and β-thalassaemia.

Recent clinical trials of gene therapy have shown remarkable therapeutic benefits and an excellent safety record. They provide evidence for the long-sought promise of gene therapy to deliver 'cures' for some otherwise terminal or severely disabling conditions. Behind these advances lie improved vector designs that enable the safe delivery of therapeutic genes to specific cells. Technologies for editing genes and correcting inherited mutations, the engagement of stem cells to regenerate tissues and the effective exploitation of powerful immune responses to fight cancer are also contributing to the revitalization of gene therapy.

Preliminary results suggest that treatment for rare disease is safe, but its effectiveness is unclear. Preliminary results suggest that treatment for rare disease is safe, but its effectiveness is unclear.

Gene editing offers the prospect of curing the inherited neurodegenerative condition in a single dose. Gene editing offers the prospect of curing the inherited neurodegenerative condition in a single dose.

Revamped Cas9 protein could work on more sites in the genome, and with fewer unwanted effects. Revamped Cas9 protein could work on more sites in the genome, and with fewer unwanted effects.

The largest organ in the body is a prime target for gene therapy. The largest organ in the body is a prime target for gene therapy.

Site-specific gene addition can allow stable transgene expression for gene therapy. When possible, this is preferred over the use of promiscuously integrating vectors, which are sometimes associated with clonal expansion1 and oncogenesis2. Site-specific endonucleases that can induce high rates of targeted genome editing are finding increasing applications in biological discovery and gene therapy3. However, two safety concerns persist: (1) endonuclease-associated adverse effects, both on4 and off-target5,6; and (2) oncogene activation caused by promoter integration, even without nucleases7. Here, we perform recombinant adeno-associated virus (rAAV) mediated promoterless gene targeting without nucleases and demonstrate amelioration of the bleeding diathesis in haemophilia B mice. In particular, we target a promoterless human coagulation factor IX (hF9) gene to the liver-expressed albumin (Alb) locus. hF9 is targeted, along with a preceding 2A-peptide coding sequence, to be integrated just upstream to the Alb stop codon. While hF9 is fused to Alb at the DNA and RNA levels, two separate proteins are synthesized by way of ribosomal skipping. Thus, hF9 expression is linked to robust hepatic albumin expression without disrupting it. We injected an AAV8-hF9 vector into neonatal and adult mice and achieved on-target integration into ~0.5% of the albumin alleles in hepatocytes. We established that hF9 was produced only from on-target integration, and ribosomal skipping was highly efficient. Stable hF9 plasma levels at 7–20% of normal were obtained, and treated factor IX deficient mice had normal coagulation times. In conclusion, transgene integration as a 2A-fusion to a highly expressed endogenous gene may obviate the requirement for nucleases and/or vector-borne promoters. This method may allow for safe and efficacious gene targeting in both infants and adults by greatly diminishing off-target effects while still providing therapeutic levels of expression from integration.

Bone-marrow transplantation is an effective cell therapy but requires myeloablation, which increases infection risk and mortality. Recent lineage-tracing studies documenting that resident macrophage populations self-maintain independently of haematological progenitors prompted us to consider organ-targeted, cell-specific therapy. Here, using granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor-β-deficient (Csf2rb(-/-)) mice that develop a myeloid cell disorder identical to hereditary pulmonary alveolar proteinosis (hPAP) in children with CSF2RA or CSF2RB mutations, we show that pulmonary macrophage transplantation (PMT) of either wild-type or Csf2rb-gene-corrected macrophages without myeloablation was safe and well-tolerated and that one administration corrected the lung disease, secondary systemic manifestations and normalized disease-related biomarkers, and prevented disease-specific mortality. PMT-derived alveolar macrophages persisted for at least one year as did therapeutic effects. Our findings identify mechanisms regulating alveolar macrophage population size in health and disease, indicate that GM-CSF is required for phenotypic determination of alveolar macrophages, and support translation of PMT as the first specific therapy for children with hPAP.

Clinical trials may soon test whether gene editing can cure a group of debilitating haemoglobin disorders.

Targeted genome editing by artificial nucleases has brought the goal of site-specific transgene integration and gene correction within the reach of gene therapy. However, its application to long-term repopulating haematopoietic stem cells (HSCs) has remained elusive. Here we show that poor permissiveness to gene transfer and limited proficiency of the homology-directed DNA repair pathway constrain gene targeting in human HSCs. By tailoring delivery platforms and culture conditions we overcame these barriers and provide stringent evidence of targeted integration in human HSCs by long-term multilineage repopulation of transplanted mice. We demonstrate the therapeutic potential of our strategy by targeting a corrective complementary DNA into the IL2RG gene of HSCs from healthy donors and a subject with X-linked severe combined immunodeficiency (SCID-X1). Gene-edited HSCs sustained normal haematopoiesis and gave rise to functional lymphoid cells that possess a selective growth advantage over those carrying disruptive IL2RG mutations. These results open up new avenues for treating SCID-X1 and other diseases.

The US Food and Drug Administration’s decision breathes new life into RNA-interference therapies. RNA-interference therapies were once left for dead but now the US Food and Drug Administration has approved patisiran.

The method could minimize damage from disease if a condition is diagnosed in utero. The method could minimize damage from disease if a condition is diagnosed in utero.

Recombinant adeno-associated viral (rAAV) vectors have shown early promise in clinical trials. The therapeutic transgene cassette can be packaged in different AAV capsid pseudotypes, each having a unique transduction profile. At present, rAAV capsid serotype selection for a specific clinical trial is based on effectiveness in animal models. However, preclinical animal studies are not always predictive of human outcome. Here, in an attempt to further our understanding of these discrepancies, we used a chimaeric human-murine liver model to compare directly the relative efficiency of rAAV transduction in human versus mouse hepatocytes in vivo. As predicted from preclinical and clinical studies, rAAV2 vectors functionally transduced mouse and human hepatocytes at equivalent but relatively low levels. However, rAAV8 vectors, which are very effective in many animal models, transduced human hepatocytes rather poorly-approximately 20 times less efficiently than mouse hepatocytes. In light of the limitations of the rAAV vectors currently used in clinical studies, we used the same murine chimaeric liver model to perform serial selection using a human-specific replication-competent viral library composed of DNA-shuffled AAV capsids. One chimaeric capsid composed of five different parental AAV capsids was found to transduce human primary hepatocytes at high efficiency in vitro and in vivo, and provided species-selected transduction in primary liver, cultured cells and a hepatocellular carcinoma xenograft model. This vector is an ideal clinical candidate and a reagent for gene modification of human xenotransplants in mouse models of human diseases. More importantly, our results suggest that humanized murine models may represent a more precise approach for both selecting and evaluating clinically relevant rAAV serotypes for gene therapeutic applications.

Technique to knock out mutant gene relies on fatty molecules to deliver CRISPR components to inner-ear cells. Technique to knock out mutant gene relies on fatty molecules to deliver CRISPR components to inner-ear cells.

The treatment of a patient affected by an incurable genetic skin disease demonstrates the efficacy, feasibility and safety of replacing almost the whole skin using genetically corrected stem cells. See Letter p.327 Patients with junctional epidermolysis bullosa (JEB) carry mutations in genes that encode components of the basement membrane, which ensures the integrity between the epidermis and the dermis, such as laminin-332. These mutations cause blistering of the skin and chronic wounds. Following initial treatment of an adult patient with a limited affected region, Michele De Luca and colleagues reconstruct the full epidermis of a 7-year-old patient with autologous transgenic cells transduced with a virus vector carrying the non-mutated form of laminin-322. The integration sites of the virus used for gene delivery provide a tracing tool ex vivo and in vivo and demonstrate that the human epidermis is sustained by a limited number of long-lived stem cells.

In the 1980s, bone-marrow transplants transformed the lives of children with fatal lysosomal diseases. Researchers are now working on another revolutionary treatment.

After a series of setbacks, genetic therapies are finally moving beyond small academic trials towards approval as treatments.

Editing of the human genome to correct disease-causing mutations is a promising approach for the treatment of genetic disorders. Genome editing improves on simple gene-replacement strategies by effecting in situ correction of a mutant gene, thus restoring normal gene function under the control of endogenous regulatory elements and reducing risks associated with random insertion into the genome. Gene-specific targeting has historically been limited to mouse embryonic stem cells. The development of zinc finger nucleases (ZFNs) has permitted efficient genome editing in transformed and primary cells that were previously thought to be intractable to such genetic manipulation 1 . In vitro, ZFNs have been shown to promote efficient genome editing via homology-directed repair by inducing a site-specific double-strand break (DSB) at a target locus 2–4 , but it is unclear whether ZFNs can induce DSBs and stimulate genome editing at a clinically meaningful level in vivo. Here we show that ZFNs are able to induce DSBs efficiently when delivered directly to mouse liver and that, when co-delivered with an appropriately designed gene-targeting vector, they can stimulate gene replacement through both homology-directed and homologyindependent targeted gene insertion at the ZFN-specified locus. The level of gene targeting achieved was sufficient to correct the prolonged clotting times in a mouse model of haemophilia B, and remained persistent after induced liver regeneration. Thus, ZFNdriven gene correction can be achieved in vivo, raising the possibility of genome editing as a viable strategy for the treatment of genetic disease.

Therapy that targets disease-causing mutations could become the first of its kind approved for use in the United States.

Adeno-associated virus (AAV) vectors are currently the leading candidates for virus-based gene therapies because of their broad tissue tropism, non-pathogenic nature and low immunogenicity. They have been successfully used in clinical trials to treat hereditary diseases such as haemophilia B (ref. 2), and have been approved for treatment of lipoprotein lipase deficiency in Europe. Considerable efforts have been made to engineer AAV variants with novel and biomedically valuable cell tropisms to allow efficacious systemic administration, yet basic aspects of AAV cellular entry are still poorly understood. In particular, the protein receptor(s) required for AAV entry after cell attachment remains unknown. Here we use an unbiased genetic screen to identify proteins essential for AAV serotype 2 (AAV2) infection in a haploid human cell line. The most significantly enriched gene of the screen encodes a previously uncharacterized type I transmembrane protein, KIAA0319L (denoted hereafter as AAV receptor (AAVR)). We characterize AAVR as a protein capable of rapid endocytosis from the plasma membrane and trafficking to the trans-Golgi network. We show that AAVR directly binds to AAV2 particles, and that anti-AAVR antibodies efficiently block AAV2 infection. Moreover, genetic ablation of AAVR renders a wide range of mammalian cell types highly resistant to AAV2 infection. Notably, AAVR serves as a critical host factor for all tested AAV serotypes. The importance of AAVR for in vivo gene delivery is further highlighted by the robust resistance of Aavr(-/-) (also known as Au040320(-/-) and Kiaa0319l(-/-)) mice to AAV infection. Collectively, our data indicate that AAVR is a universal receptor involved in AAV infection.

Repairing the faulty genes that cause haemophilia could ultimately cure the disease, but it will be a tough challenge.

Gene therapy is finally getting a bumper crop of data that show clinical efficacy after fine-tuning of key parameters that control safety and potency. Supporting evidence comes from treatment of two life-threatening human diseases.