FDA Greenlights a CRISPR-Based Test to Diagnose Covid-19
A test that can diagnose the coronavirus within an hour using the gene-editing technology known as CRISPR has received emergency use authorization from the U.S. Food and Drug Administration.
The test was developed by Sherlock Biosciences, a biotech company launched in March 2019 by CRISPR pioneer Feng Zhang, a researcher at MIT and the Broad Institute.
In recent years, CRISPR has been imagined as a way to treat all kinds of diseases because of its ability to precisely cut DNA. It does that by using a molecular guide that searches for and locks onto a particular DNA sequence. Once there, an enzyme attached to the guide cuts the DNA at the right spot.
The technology can be used to snip out sections of DNA or replace genetic sequences entirely. A handful of early-stage clinical trials are testing the technique to treat certain cancer, blood disorders, and a type of inherited blindness. But researchers have also been experimenting with CRISPR as a way to diagnose diseases.
Sherlock Biosciences’ test works by programming CRISPR’s molecular guide to detect the presence of a specific genetic signature — in this case, the genetic signature for SARS-CoV-2 — in a nasal or throat swab. When that’s found, the CRISPR enzyme is activated and releases a signal. The test gives a result in an hour and can be run on basic equipment that most labs already have. The company says its test provides true positive and true negatives with 100% accuracy in patient samples, though it has not published data on the claim yet.
“The promise of CRISPR has been talked about for years now,” Rahul Dhanda, CEO and co-founder of Sherlock Biosciences, said in an interview, “We’ve been able to take the steps necessary to show that that promise is real.”
Currently, most tests to diagnose Covid-19 relies on a method called polymerase chain reaction, or PCR, which works by amplifying a tiny amount of viral genetic material so that it can be detected. While it’s a highly accurate and reliable lab technique, it’s also rather slow. It can take six to eight hours to run.
Companies like Abbott Laboratories and Cepheid have developed tests that render a result in just 15 minutes or less, but they use special machines that are expensive and not available everywhere. Public health experts agree that much more testing is needed in the United States, around the order of millions of tests a day, in order for cities and states to safely reopen. The country is currently testing over 200,000 people a day, according to estimates. Fast new tests could help in that effort, as well as track the spread of the disease over time.
The Cambridge, Massachusetts-based Sherlock Biosciences is working to rapidly scale the production of its test kits to make them available soon. Dhanda says the company will focus on rolling them out at high-volume testing locations around the country. Another startup, Mammoth Biosciences of San Francisco, is working on a similar CRISPR-based coronavirus test that could provide a result in around 45 minutes. That group, which is also seeking FDA authorization, published a paper in mid-April detailing promising results of its test on patient samples.
Meanwhile, Zhang’s group at MIT is working on an even simpler version of a CRISPR test called STOPCovid that’s similar to a pregnancy test and costs less than $10. It uses a nasal swab or saliva sample and does not require any lab equipment. For now, it’s only available to scientists for research purposes, but the goal is for the test to be used in pharmacies, emergency rooms, or eventually at home.