A gene editing tool with promising clinical applications is facing renewed scrutiny after several recent studies found its side effects could be worse than expected, Eileen Drage O"Reilly writes.
Sometimes heralded as "revolutionary," CRISPR-Cas9 is the subject of a massive investment of money and research efforts toward the ultimate goal of editing human genes, which many hope will begin on a trial basis in the U.S. this year.
The big question: Is CRISPR-Cas9 safe enough to expand it into human clinical trials? The consensus of scientists whom Axios spoke with: Not quite yet.
"The CRISPR reagents are wonderful tools for research but we still do not control them enough for safe and efficient use into patients. Particularly we know very little about the DNA repairing mechanisms triggered after the cut by Cas9."— Lluis Montoliu, research scientist, Spanish National Research Council (CSIS)
CRISPR is a hot topic, and for good reason: it could have a wide range of applications for treating diseases and correcting genetic conditions in humans.
Advances in research are published frequently. For instance, yesterday Science Translational Medicine published a study in which researchers took cancer cells that had left their original tumor in mice, edited them with CRISPR to have "suicide genes," and re-injected them into the animal to see if they would return to the tumor and end up killing the cancer. They said they found "marked survival benefits."
Still, there's always been a steady drumbeat of cautionary tales since it's been known the editing process often targets the wrong gene. Problems can also be caused when the cell repairs itself after the editing process, Montoliu says.
This was brought sharply into focus in recent studies:
- Earlier this week, U.K. scientists published a study in Nature Biotechnology saying in some cases CRISPR may cause large deletions and rearrange the DNA it is targeting. They warned that the problem has been "seriously underestimated."
- This follows recent studies that found CRISPR may inadvertently increase the risk of triggering cancer.
- In May, the FDA halted a trial for sickle cell patients before it started. Scientists planned to edit bone marrow stem cells using CRISPR and then transplant them back into the patients.
What's next: Michael Kosicki, study author of the Wellcome Sanger Institute study from the U.K., says questions for researchers include:
"Is there any important genes close to the one we want to edit? How often do large deletions, rearrangements and especially translocations happen in relevant cells? And finally, how much risk is acceptable? The answer to the last question depends on how serious the treated disease is."
Go deeper: Read the full story in the Axios stream.