Preclinical data from Beam Therapeutics' base editing platform demonstrate how technology could open new treatment options for patients with cancer and other immune-mediated diseases who might benefit from advanced cellular therapies requiring a large number of simultaneous edits.  
According to Beam Therapeutics, a biotechnology company that develops precision genetic medicines through base editing, the fourth-generation base editor (BE4) demonstrated high-efficiency multiplex base editing of 3 cell surface targets in primary human T cells (TRAC, B2M, and PD-1), knocking out expression of each gene in 95%, 95% and 88% of cells, respectively, in a single electroporation, during the study.
Editing each of these genes has the potential to be useful in the creation of CAR-T cell therapies with improved therapeutic properties, according to a statement.
Each of the genes was silenced by a single targeted base change (C to T) without the creation of double strand breaks. As a result, the BE4-treated cells also did not have any measurable translocations (large-scale genomic rearrangements), whereas cells receiving the same 3 edits with a nuclease did show detectable genomic rearrangements.
The data underscore an exciting emerging application of base editing technology, according to John Evans, chief executive of Beam.
This application allows multiplex editing of CAR-T cells without genomic rearrangements.
“Beam is actively applying base editing across a wide range of serious genetic diseases using both ex vivo and in vivo delivery approaches, and we are pleased to begin sharing some of the research progress in our therapeutic programs,” Evanssaid in a statement.
Beam Therapeutics presented the preclinical data Monday at the American Society of Gene and Cell Therapy (ASGCT) 22nd Annual Meeting in Washington, DC.


Beam Therapeutics presents data on multiplex base editing for engineered CAR-T cells at American Society of Gene and Cell Therapy 22nd Annual Meeting [news release]. Cambridge, MA; April 29, 2019: Beam Therapeutics. Accessed April 30, 2019.