Genome editing in human embryos inches closer to the clinic

On Aug 2Nature published a study in which US-based researchers successfully edited the genome of a human embryo using the CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9) system to correct a genetic defect implicated in a potentially fatal heart condition. Although this is not the first time CRISPR has been used for genome editing in embryos, the introduction of the editing molecules at an earlier stage led to a much higher targeting efficiency than that in previous studies (72% vs 14–25%). The researchers also managed to avoid mosaicism, in which some cells in the embryo have the corrected version of the gene but others still have the mutation.

The work has raised hopes for new treatments based on genome editing, as well as fears over so-called designer babies. But both are still a long way off. Read more in The Lancet Child & Adolescent Health.

The big cull

Can New Zealand pull off an audacious plan to get rid of all invasive predators by 2050?

Razza the rat nearly ended James Russell’s scientific career. Twelve years ago, as an ecology graduate student, Russell was releasing radio-collared rats on to small islands off the coast of New Zealand to study how the creatures take hold and become invasive. Despite his sworn assurances that released animals would be well monitored and quickly removed, one rat, Razza, evaded capture and swam to a nearby island.

For 18 weeks, Russell hunted the animal. Frustrated and embarrassed, he fretted about how the disaster would affect his PhD. “I felt rather morose about the prospects for my dissertation,” he says. Read more in Nature.

Zinc-finger nucleases make the cut in HIV

Sangamo’s lead zinc-finger therapeutic supports the potential of gene-editing technology, but CRISPR-based gene-editing therapeutics are close behind.

On 6 March, Sangamo BioSciences released the latest encouraging results for its potential anti-HIV therapy SB-728-T, a zinc-finger nuclease (ZFN) gene-editing drug. Phase I and II trials showed continued signs of safety and efficacy, it reported in the New England Journal of Medicine (N. Engl. J. Med. 370, 901–910; 2014) and in several abstracts presented at the Conference on Retroviruses and Opportunistic Infections (CROI) in Boston, Massachusetts, USA.

SB-728-T works by targeting the CC-chemokine receptor 5 (CCR5) gene, which encodes a cell-surface receptor that HIV uses to gain entry into CD4 T cells. CCR5 is well validated as a drug target: GlaxoSmithKline’s small-molecule CCR5 inhibitor maraviroc was approved as an anti-HIV drug in 2007, people with loss-of-function CCR5 mutations are immune to many common strains of HIV, and one person, Timothy Brown — known as the ‘Berlin patient’ — has been cured of HIV since receiving a bone marrow transplant from a CCR5-mutant donor. Sangamo’s treatment breaks new ground by taking CD4 cells from a patient, disabling CCR5 by editing the gene-coding sequence and then reintroducing the modified cells back into the patient to proliferate and replace vulnerable and infected cells. Read more in NRDD.