A paper published in Nature Biotechnology by Allan Bradley and colleagues from the Wellcome Sanger Institute in Hinxton, UK, shows that classical CRISPR editing can cause large rearrangements of DNA near the target site in actively dividing cells. We may think of it as the latest CRISPR alarm, but also as a demonstration of how biomedical research works. Firstly: no technology is perfect, but the best ones are perfectible. CRISPR belongs to this category because it is an extraordinarily versatile and fast-evolving biotech platform. When reading news like “CRISPR causes this or that problem,” the first question to ask is: which CRISPR variant are we talking about?

There are many by now, standard or high fidelity, targeting DNA or RNA, cutting to edit or editing without cutting. The rearrangement problem, for example, should not occur with  CRISPR systems for base-editing applications. Secondly: China has already started many human trials, but Europe and the US are moving more cautiously, therefore it is no wonder that researchers focus on CRISPR risks, to learn how to best control them, before using CRISPR clinically. The question, then, is the following: is there any hope to efficiently discard badly edited cells? If the cells can be harvested and then reintroduced back into the patient (ex vivo gene therapy), the answer is yes, keep calm and sequence DNA. Not just the DNA word intended for editing but the whole sentence, paragraph and even the book, to make sure that there are no unintended changes within the genome. Biotech companies working on medical applications already do it. Thirdly: there will always be some hype on successes and failures of cool new technologies, but there is no lack of balanced articles either. To go deeper into the latest controversy,  for example, you may want to read Nature, STAT, The Conversation.