Allogeneic chimeric antigen receptor T-cell (CART) treatments need several gene alterations to be therapeutically feasible. Unfortunately, the majority of allogeneic CARTs were produced utilizing gene editing methods that cause DNA double-stranded breaks (DSBs), which can have undesired on-target editing results and unanticipated effects.

As opposed to clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), cytosine base editors (CBEs) install C•G to T•A point mutations in T cells with between 90% and 99% efficiency in silencing gene expression without creating DSBs, greatly reducing or eliminating undesirable editing outcomes after multiplexed editing. Researchers produced 7CAR8, a CD7-directed allogeneic CART utilizing four concurrent base modifications, employing CBE.

They demonstrated that CBE, in contrast to CRISPR-Cas9, did not affect T-cell proliferation, result in inappropriate activation of the DNA damage response mechanism, or cause karyotypic anomalies after combinatorial editing. They used various in vitro and in vivo models to show that 7CAR8 is particularly effective against T-cell acute lymphoblastic leukemia (T-ALL).

Therefore, CBE is a promising approach for multiplexed gene editing applications and may be utilized to produce quadruple-edited 7CAR8 cells, which have a high potential for clinical translation for T-ALL that has relapsed and is no longer responsive to treatment.

Reference: ashpublications.org/blood/article/140/6/619/485236/Cytosine-base-editing-enables-quadruple-edited