Two weeks ago, we reported on a significant problem with the CRISPR gene editing technology, and by this week, it appears the problem has been at least partly rectified. Scientists from The University of Texas at Austin developed a technique that can spot editing mistakes made by CRISPR.

Scientists already use the gene-editing tool called CRISPR to edit the genetic code, in anticipation of a revolutionary ability to revise genetic imperfections that cause severe or debilitating diseases. And until recently, reporting on CRISPR trials was mostly positive… until a few weeks ago, when one team reported a significant side effect of CRISPR editing. In theory, gene-editing should work much like fixing a recurring typo in a document with an auto-correct feature, but CRISPR molecules — proteins that find and edit genes — sometimes target the wrong genes, acting more like an auto-correct feature that turns correctly spelled words into typos. Editing the wrong gene could create new problems, such as causing healthy cells to become cancerous.

The UT Austin team developed a way to rapidly test a CRISPR molecule across a person’s entire genome to foresee other DNA segments it might interact with besides its target. This new method, they say, represents a significant step toward helping doctors tailor gene therapies to individual patients, ensuring safety and effectiveness.

“You and I differ in about 1 million spots in our genetic code,” says Ilya Finkelstein, an assistant professor in the Department of Molecular Biosciences at UT Austin and the project’s principal investigator. “Because of this genetic diversity, human gene editing will always be a custom-tailored therapy.”

“If we’re going to use CRISPR to improve peoples’ health, we need to make sure we minimize collateral damage, and this work shows a way to do that,” says Stephen Jones, a postdoctoral researcher at UT Austin and one of three co-lead authors of the paper.

Knowing these rules will lead to better computer models for predicting which DNA segments a specific CRISPR molecule is likely to interact with. And that means personalized gene therapies will be safer and more effective, sooner.

The research appears in the journal Cell.