CRISPR/Cas9 for the treatment of haematological diseases: a journey from bacteria to the bedside

Abstract

Genome editing therapies represent a significant advancement in next-generation, precision medicine for the management of haematological diseases, and CRISPR/Cas9 has to date been the most successful implementation platform. From discovery in bacteria and archaea over three decades ago, through intensive basic research and pre-clinical development phases involving the modification of therapeutically relevant cell types, CRISPR/Cas9 genome editing is now being investigated in ongoing clinic trials. Despite the widespread enthusiasm brought by this new technology, significant challenges remain before genome editing can be routinely recommended and implemented in the clinic. These include risks of genotoxicity resulting from off-target DNA cleavage or chromosomal rearrangement, and suboptimal efficacy of homology-directed repair editing strategies, which thus limit therapeutic options. Practical hurdles such as high costs and inaccessibility to patients outside specialised centres must also be addressed. Future improvements in this rapidly developing field should circumvent current limitations with novel editing platforms and with the simplification of clinical protocols using in vivo delivery of editing reagents.

CRISPR gene editing: a revolution in progress

“…So, life on Earth evolved a plethora of defence mechanisms. At least 40% of bacteria, for example, use the Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) system to defend themselves from viruses 2 . CRISPR is such a powerful line of defence that it has remained part of cells’ machinery for millions of years.…”

“…Over the years, researchers exploited several genome‐editing methods, such as zinc finger nuclease and transcription activator‐like effector nuclease 2,8 . However, CRISPR‐Cas9 (see Figure 1) is the most widely used 2 . Dr Antony Adamson, Manager of the Genome Editing Unit, University of Manchester, points out that the older approaches were difficult to use and often inefficient.…”

“…Different bacterial species evolved variations on Cas9 that recognise different PAMs 9 . Researchers are trying to develop variations of Cas9 that don't need PAM 2 . But it is early days.…”

“…CRISPR‐Cas9 could help treat several other genetic diseases including sickle cell anaemia, hereditary retinal disorders, beta‐thalassemia, cystic fibrosis and Duchenne muscular dystrophy. CRISPR‐Cas9 could also lead to new treatments for some cancers and cardiovascular conditions, Huntington's disease and certain viral infections, including HIV and SARS‐CoV‐2 2,4‐6 …”

Multiplex CRISPR/Cas9 genome editing in hematopoietic stem cells for fetal hemoglobin reinduction generates chromosomal translocations

“… 9 , 10 , 11 , 12 , 13 , 14 An alternative curative approach is offered by genome editing platforms, the most commonly used being Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). 15 One way in which this technology may be applied to the treatment of β-hemoglobinopathies is by the disruption of prespecified areas of the genome in a manner predicted to recapitulate the condition of hereditary persistence of fetal hemoglobin (HPFH). In this naturally occurring, benign variant, individuals retain high levels of fetal hemoglobin (HbF) into adulthood beyond the point at which a physiological switch to adult hemoglobin (HbA) production usually occurs.…”