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CRISPR Companies Respond

In separate letters, Intellia Therapeutics and Editas Medicine criticize a recent report in Nature Methods that found that CRISPR/Cas9-based gene editing led to unexpected changes, Technology Review reports.

Stanford University's Vinit Mahajan and his colleagues used the gene-editing approach to fix the mutation behind retinitis pigmentosa in mice, but when they sequenced the whole genomes of the edited mice, they discovered indels and SNPs that hadn't been predicted to be possible off-target editing sites. The report sent the stock of gene-editing companies down.

However, Tech Review points out that researchers on Twitter and elsewhere uncovered errors in their analysis. In particular, it notes that the researchers mistakenly attributed some normal variation between the animals to the effect of editing.

Scientists from Editas and Intellia both argue that report's conclusions aren't supported by its data. Editas co-founder George Church, who is also at Harvard University, tells Tech Review that the report should at least be updated and, possibly, retracted, while Intellia's CEO Nessan Bermingham says it should be retracted.

Nature Methods says it is "carefully considering all concerns that have been raised with us and are discussing them with the authors."