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Last summer, a letter appeared in a scientific journal that challenged how truly “revolutionary” and world-changing CRISPR gene-editing technology really might be. Researchers found that when they used CRISPR to cure blindness in mice, it had resulted in not just a few but more than a thousand unintended effects. Those unintended changes to DNA, they found, were not detectable using common methods for checking for off-target effects. This, the authors wrote, meant that CRISPR needed significant fine-tuning before it was ready to cure disease in people. Stocks tumbled. The scientific community freaked out.

But backlash was swift. Other researchers lobbed accusations of “careless mistakes” and flaws in the methodology of the mouse study.

Now, a new paper published as a preprint on the website bioRxiv lends support to the assertion that the initial mouse study was little more than a false alarm. Scientists at the Wellcome Sanger Institute in Britain recreated the study and found that there wasn’t much to be concerned about. In their recreation, they used more rigorous controls for the sake of accuracy. Mice that got CRISPR’d didn’t have a significant difference in gene mutations than those that didn’t receive the treatment.

The possibility of unintended effects is still a concern in developing any CRISPR therapy—in January, another study found that CRISPR triggered an immune response in human cells—but this new paper suggests it’s perhaps not as big a concern as last summer’s paper proposed. (The authors of the original paper did not respond to a request for comment from Gizmodo prior to publication.)

“This work should support further efforts to develop CRISPR-Cas9 as a therapeutic tool,” they concluded.

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For those banking on CRISPR as the cure-all of the future, we’re guessing this paper is a big sigh of relief. It still must go through the peer-review process, however, and much more research will need to be done before CRISPR therapies are ready for the mainstream.