Excision BioTherapeutics recently announced that the first participant in a Phase I/II clinical trial has received a CRISPR-based gene-editing therapy designed to snip HIV out of human cells, potentially leading to a functional cure. Antiretroviral therapy can keep HIV replication suppressed, but the virus inserts its genetic blueprints—known as a provirus—into the DNA of human cells and establishes a long-lasting reservoir that is unreachable by antiretrovirals and invisible to the immune system. The therapy, dubbed EBT-101, uses an adeno-associated virus to deliver CRISPR-Cas9 nucleases—enzymes that act as “molecular scissors”—and dual guide RNAs targeting three sites in the HIV genome that tell the enzymes where to cut. This study is evaluating a single IV infusion of EBT-101 in nine men with an undetectable viral load on daily antiretroviral therapy. The first par-ticipant was treated last July, and the therapy has been well tolerated so far. The man is expected to start a carefully monitored antiretroviral treatment interruption to see whether his HIV rebounds.