Many in vitro #CRISPR knock-in approaches use small molecule drugs to improve the efficiency of homology-directed repair, but these drugs may or may not be safe in vivo. In this paper from #NatureBiotechnology, the authors find that an FDA-approved therapy, fludarabine, can be used for a similar purpose. Still a long ways to go before any genetic knock-ins are routinely done in vivo, but making progress toward doing so safely: https://www.nature.com/articles/s41587-022-01240-2 #science #medicine #GeneEditing #AAV