The FDA Must Decide Whether Crispr’s Gene-Editing Promise Is Worth the Risk

Over the ages, scientists have devised medicines to successfully treat thousands of illnesses, but eliminating rare and deadly maladies altogether is a holy grail. Treatments for inherited conditions like sickle cell disease have offered mere stopgaps that still leave patients to live sickly, pain-filled lives. The gene-editing technology Crispr, whose researchers were awarded the 2020 Nobel Prize in chemistry, could change that. It’s been heralded for its potential not only to treat such diseases, but to cure them by changing a person’s genetic code.

Now, for the first time, a therapy that harnesses Crispr’s power is poised to make its way to market. That is, if it can clear one last hurdle: regulators.

The US Food and Drug Administration is considering a Crispr treatment that could offer a cure for the blood disorder sickle cell disease, a condition that affects some 100,000 Americans, most of whom are Black. In late October, FDA staff raised concerns about some of the safety data submitted by two companies seeking approval for the therapy, dubbed exa-cel. A panel of FDA medical advisers convened this week to ask questions about the treatment. By early December, regulators will decide whether to give it a stamp of approval.

It’s a major test for a technology that, since its discovery more than a decade ago, has been expected to bring about a revolution in medicine. Crispr’s innovation is the ability to cut and paste DNA with far more ease and precision than ever before—necessary, for example, to address the mutation to a single letter of genetic code that causes sickle cell disease. Instead of treating the disease, Crispr essentially rewrites the code for what’s causing the malady. But regulators have viewed it with caution, worried about the risks of making permanent changes to the body’s instruction manual. Advocates also say they fear the one-time sickle cell disease treatment, which is expected to cost at least $1 million, will be far too expensive for many patients.

Two companies, Vertex Pharmaceuticals Inc. and Crispr Therapeutics AG, are seeking approval to edit the genes of people with sickle cell disease so that they make a different form of hemoglobin, the molecule that carries oxygen throughout the body. Sickle cell disease is caused by a mutation of just one of the 3 billion letters that make up a person’s DNA. That mutation causes red blood cells to bend in a crescent shape instead of a round one, making it harder for essential oxygen to reach tissues and organs. The companies want to extract blood stem cells and edit them in a lab, then return them to patients’ bodies.

The results so far have been promising. A clinical trial conducted by the companies found that more than 90% of sickle cell disease patients were free of pain crises for at least 12 months. Hank Greely, a law professor at Stanford University who wrote a book on the science and ethics of Crispr, called the study’s results “tremendous.”

But researchers have studied patients treated with Crispr for only a few years, and no one knows what will happen to them over their lifetimes. “That will be an ongoing question for any clinical application of genome editing: What are the long-term effects, and are they truly predictable?” says Jennifer Doudna, a Crispr pioneer, biochemist at University of California at Berkeley and founder of the Innovative Genomics Institute. “If they are, that bodes well for opening up the pipeline to other diseases in the future.”







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