“On January 12, 2020, one day after the first known COVID-19-related death had been confirmed, researchers in China identified the SARS-CoV-2 virus’ genetic sequence, and shared it with the rest of the world,” reported Jamie Bell in an article for NSMedicalDevices.com. Nucleic acid-based PCR (polymerase chain reaction) tests have been used around the world to understand and control the spread of COVID-19. But an inability to keep up with demand due to shortages of the chemical reagents used in the PCR-based testing kits highlighted the need for alternative testing options. Is CRISPR technology the answer?
CRISPR (clustered regularly interspaced short palindromic repeats) technology is a biotechnological tool that has most recently been used in the context of genetic engineering or gene editing. As a tool CRISPR could edit genomes by identifying DNA sequences inside a cell and then altering them through the use of a “pair of molecular scissors” and snipping specific strands of DNA to remove genetic mutations. Through this method it could correct genetic defects, treat and prevent the spread of certain diseases and even improve the quality of crops through genetic modification. More recent research has been examining whether CRISPR could be used in diagnostics through detection of certain genomes versus editing them. Diseases with a known genetic sequence, like SARS-CoV-2, could be identified and diagnosed in human samples.
Two American biotech firms, Sherlock Biosciences and Mammoth Biosciences, gained an emergency use authorization (EUA) from the FDA for their respective CRISPR-based testing kits. As of September 2020 more than 170 diagnostic tools for SARS-CoV-2 have received an EUA, but only Sherlock and Mammoth gained FDA approval for a CRISPR-based testing device. Sensitivity, the proportion of positive test results the test has been shown to correctly identify, and specificity, the proportion of negative test results it has been shown to correctly identify, are the two key elements determining how accurately a COVID-19 test can identify the virus. What are the benefits for utilizing CRISPR in SARS-CoV-2 testing?
GlobalData medical analyst Brian Hicks says, “When people say CRISPR is highly programmable, it means that researchers can design a strand of RNA based on the genetic sequence of the disease that they’re interested in finding. I think that’s the biggest advantage of CRISPR in comparison to PCRs and other types of tests – you can design different sequences for different targets.” Hicks goes on to say that coronavirus is “a virus that changes and mutates relatively quickly, and we’ve focused our efforts on developing a highly specific test, taking into account the much larger pool of sequences that became available as more and more was known about the virus.”
“Our SARS-CoV-2 test runs in about an hour, which is (two hours) faster than most PCR methods that dominate this type of testing,” says Sherlock Biosciences’ Chief Technology Officer, Will Blake. While a savings of two hours doesn’t seem that significant on an individual basis, in situations like the current pandemic it can be a critical benefit. Blake goes on to say, “the reason why CRIPSR has the potential to be a disruptor in the market is because, if you’re performing tests at a massive scale, every little bit of time saving counts.”
Reagents and Equipment
A survey from the Association of Molecular Pathology in May found that more than 70% of clinical labs had suffered delays in Covid-19 testing due to supply chain disruptions and shortages of critical reagents. Sherlock’s Blake says their test uses a different set of reagents that are “more readily available” and there is no requirement for specialized equipment. The equipment needed for the test is typically part of most CLIA-certified sets of lab equipment.