CRISPR-Cas

What makes CRISPR-Cas a game-changer in gene editing?

The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) — CRISPR-associated protein (Cas) system has transformed gene editing into a precise, powerful tool capable of changing lives. This technology enables targeted genetic modifications with wide-ranging therapeutic potential, including correcting disease-causing mutations in genetic and rare disorders, engineering cells for cell and gene therapies (e.g., CAR-T cells), and modulating cancer-related genes to treat tumors. Notably, CRISPR-Cas9 has enabled Casgevy, the first approved CRISPR-based therapy for sickle cell anemia and β-thalassemia.

How does CRISPR-Cas enable genome editing?

CRISPR-Cas9 gene editing mechanism

CRISPR-Cas9 uses a Cas9 nuclease guided by a single-guide RNA (sgRNA) to recognize a specific DNA sequence located next to a protospacer adjacent motif (PAM) and introduce a precise double-strand break. The cell then repairs the break using one of two natural pathways: non-homologous end joining (NHEJ), which can disrupt the gene by introducing small insertions or deletions, or homology-directed repair (HDR), which can utilize a donor DNA template for precise modifications.

Alternative CRISPR tools

Beyond Cas9, other CRISPR systems — including Cas12, Cas13, base editors, and prime editors — operate through alternative mechanisms, expanding the possibilities for DNA or RNA editing.

Where is CRISPR-Cas applied?

CRISPR-Cas systems enable precise and permanent DNA modifications, supporting applications from basic research to therapeutic development.

Genetic & rare diseases: CRISPR can disrupt harmful genes or correct disease-causing mutations.
Cell & gene therapies: Ex vivo or in vivo genome editing allows engineered cells — such as chimeric antigen receptor (CAR)-T cells, CAR-NK cells — to be used for personalized therapies.
Cancer treatment: CRISPR can be used to knock out or modulate cancer-related genes, enhancing tumor-targeted strategies.
Functional genomics: In research, CRISPR provides a rapid way to knock out or modify genes, helping scientists study gene function and validate therapeutic targets.

What are the challenges in CRISPR-Cas delivery?

Efficient and safe delivery of CRISPR components remains a key challenge in translating genome editing into clinical therapies. Target cells — especially immune cells — can be difficult to transfect, and achieving genetic modification at clinical scale might pose challenges. Moreover, immune responses against Cas proteins can compromise in vivo therapies by eliminating Cas-expressing edited cells, whereas transient ex vivo approaches (e.g., mRNA delivery) largely avoid this issue. To reduce off-target activity and mitigate immunogenicity, current strategies increasingly favor delivery formats that enable only short-lived expression of procaryotic enzymes.

The choice of payload and delivery method of CRISPR therapeutics significantly impact both genome editing efficacy and safety.

What are payload options for delivering CRISPR?

CRISPR payload formats

CRISPR tools (Cas nucleases, sgRNAs, and donor templates) can be introduced into cells in different formats: ribonucleoprotein (RNP) complexes, plasmid DNA (pDNA), or messenger RNA (mRNA). Each format follows a distinct intracellular pathway: pDNA requires nuclear entry for transcription, mRNA undergoes translation in the cytoplasm, and RNP complexes are immediately active, shaping the timing and efficiency of gene editing. These formats also vary in their stability and immune interactions.

Advantages of mRNA-based CRISPR delivery

Of particular interest, mRNA-based delivery provides quick and transient Cas9 expression, which improves safety by reducing off-target activity, insertional risks, and immune activation. Once translated, Cas9 protein associates with sgRNA in the cytoplasm to drive genome editing.

How can CRISPR be delivered to cells effectively?

CRISPR delivery strategies

CRISPR components can be delivered via viral or non-viral platforms, including adeno-associated viruses, lentiviral vectors, electroporation, and lipid nanoparticles (LNPs). These approaches differ in cargo capacity, targeting ability, immunogenicity, suitability for ex vivo versus in vivo applications, and clinical readiness.

Lipid Nanoparticles (LNPs) for CRISPR delivery

Within this landscape, LNPs stand out as a clinically proven and scalable platform, offering exceptional versatility for both ex vivo and in vivo gene editing. CRISPR-Cas9 mRNA-LNPs’ transient mode of action supports permanent genome edits while avoiding extended nuclease activity. A striking example of their potential is baby KJ, born with carbamoyl phosphate synthetase 1 (CPS1) deficiency, who was rapidly treated using LNP-mediated in vivo base editing — demonstrating the speed, precision, and real-world impact of this delivery technology.