Do you remember the alarm about the cancer risks of CRISPR? According to a study published in Cell Stem Cell by Italian researchers, the DNA-damage response is not such a big problem in edited cells. At least not in hematopoietic stem cells edited with highly specific nucleases.
If the Cas9 enzyme also makes cuts at off-target sites, a robust and prolonged p53 response follows, leading to detrimental effects up to irreversible cell arrest. But employing highly specific nucleases, edited cells only experience a temporary proliferation delay. Both CRISPR and the zinc finger platforms appear to work fine. Researchers from the San Raffaele Telethon Institute for Gene Therapy in Milan indeed are so satisfied with safety and efficiency data that they are now considering the next step: starting human trials for immunodeficiencies syndromes such as SCID-X1 or hyper IgM in the near future. According to clinicaltrials.gov, several trials on hematopoietic stem cells editing are already recruiting patients. Three are using zinc fingers and two are choosing CRISPR.