Unlike most other CRISPR/Cas-9 therapies that are ex vivo treatments in which cells are modified outside the body, this study was successful with an in vivo treatment
Use of CRISPR-Cas9 gene editing technology for therapeutic purposes can be a boon for clinical laboratories. Not only is this application a step forward in the march toward precision medicine, but it can give clinical labs the essential role of sequencing a patient’s DNA to help the referring physician identify how CRISPR-Cas9 can be used to edit the patient’s DNA to treat specific health conditions.
Most pathologists and medical lab managers know that CRISPR-Cas9 gene editing technology has been touted as one of the most significant advances in the development of therapies for inherited genetic diseases and other conditions. Now, a pair of biotech companies have announced a milestone for CRISPR-Cas9 with early clinical data involving a treatment delivered intravenously (in vivo).
As with other therapies, determining which patients are suitable candidates for specific treatments is key to the therapy’s success. Therefore, clinical laboratories will play a critical role in identifying those patients who would most likely benefit from a CRISPR-delivered therapy.
Such is the goal of precision medicine. As methods are refined that can correct unwelcome genetic mutations in a patient, the need to do genetic testing to identify and diagnose whether a patient has a specific gene mutation associated with a specific disease will increase.
Cleveland Clinic describes ATTR amyloidosis as a “protein misfolding disorder” involving transthyretin (TTR), a protein made in the liver. The disease leads to deposits of the protein in the heart, nerves, or other organs.
According to Intellia and Regeneron, NTLA-2001 is designed to inactivate the gene that produces the protein.
The interim clinical trial data indicated that one 0.3 mg per kilogram dose of the therapy reduced serum TTR by an average of 87% at day 28. A smaller dose of 0.1 mg per kilogram reduced TTR by an average of 52%. The researchers reported “few adverse events” in the six study patients, “and those that did occur were mild in grade.”
Current treatments, the companies stated, must be administered regularly and typically reduce TTR by about 80%.
“These are the first ever clinical data suggesting that we can precisely edit target cells within the body to treat genetic disease with a single intravenous infusion of CRISPR,” said Intellia President and CEO John Leonard, MD, in a press release. “The interim results support our belief that NTLA-2001 has the potential to halt and reverse the devastating complications of ATTR amyloidosis with a single dose.”
He added that “solving the challenge of targeted delivery of CRISPR-Cas9 to the liver, as we have with NTLA-2001, also unlocks the door to treating a wide array of other genetic diseases with our modular platform, and we intend to move quickly to advance and expand our pipeline.”
In Part 2 of the Phase 1 trial, Intellia plans to evaluate the new therapy at higher doses. After the trial is complete, “the company plans to move to pivotal studies for both polyneuropathy and cardiomyopathy manifestations of ATTR amyloidosis,” the press release states.
Previous clinical trials reported results for ex vivo treatments in which cells were removed from the body, modified with CRISPR-Cas9 techniques, and then reinfused. “But to be able to edit genes directly in the body would open the door to treating a wider range of diseases,” Nature reported.
How CRISPR-Cas9 Works
On its website, CRISPR Therapeutics, a company co-founded by Emmanuelle Charpentier, PhD, a director at the Max Planck Institute for Infection Biology in Berlin, and inventor of CRISPR-Cas9 gene editing, explained that the technology “edits genes by precisely cutting DNA and then letting natural DNA repair processes take over.” It can remove fragments of DNA responsible for causing diseases, as well as repairing damaged genes or inserting new ones.
The therapies have two components: Cas9, an enzyme that cuts the DNA, and Guide RNA (gRNA), which specifies where the DNA should be cut.
Charpentier and biochemist Jennifer Doudna, PhD, Nobel Laureate, Professor of Chemistry, Professor of Biochemistry and Molecular Biology, and Li Ka Shing Chancellor’s Professor in Biomedical and Health at the University of California Berkeley, received the 2020 Nobel Prize in Chemistry for their work on CRISPR-Cas9, STAT reported.
At some future point, it can be expected that these technologies will be combined and integrated in a way that allows clinical laboratories to make very early and accurate diagnoses of many health conditions.
Known as Prime Editing, the scientists developed this technique as a more accurate way to edit Deoxyribonucleic acid (DNA). In a paper published in Nature, the authors claim prime editing has the potential to correct up to 89% of disease-causing genetic variations. They also claim prime editing is more powerful, precise, and flexible than CRISPR.
The research paper describes prime editing as a “versatile and precise genome editing method that directly writes new genetic information into a specified DNA site using a catalytically impaired Cas9endonuclease fused to an engineered reverse transcriptase, programmed with a prime editing guide RNA (pegRNA) that both specifies the target site and encodes the desired edit.”
And a Harvard Gazette article states, “Prime editing differs from previous genome-editing systems in that it uses RNA to direct the insertion of new DNA sequences in human cells.”
Assuming further research and clinical studies confirm the
viability of this technology, clinical laboratories would have a new diagnostic
service line that could become a significant proportion of a lab’s specimen
volume and test mix.
In that e-briefing we wrote that Liu “has led a team of scientists in the development of a gene-editing protein delivery system that uses cationic lipids and works on animal and human cells. The new delivery method is as effective as protein delivery via DNA and has significantly higher specificity. If developed, this technology could open the door to routine use of genome analysis, worked up by the clinical laboratory, as one element in therapeutic decision-making.”
Now, Liu has taken that development even further.
Cell Division Not Necessary
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. It is considered the most advanced gene editing technology available. However, it has one drawback not found in Prime Editing—CRISPR relies on a cell’s ability to divide to generate desired alterations in DNA—prime editing does not.
This means prime editing could be used to repair genetic mutations in cells that do not always divide, such as cells in the human nervous system. Another advantage of prime editing is that it does not cut both strands of the DNA double helix. This lowers the risk of making unintended, potentially dangerous changes to a patient’s DNA.
The researchers claim prime editing can eradicate long lengths of disease-causing DNA and insert curative DNA to repair dangerous mutations. These feats, they say, can be accomplished without triggering genome responses introduced by other forms of CRISPR that may be potentially harmful.
“Prime editors are more like word processors capable of
searching for targeted DNA sequences and precisely replacing them with edited
DNA strands,” Liu told NPR.
The scientists involved in the study have used prime editing to perform over 175 edits in human cells. In the test lab, they have succeeded in repairing genetic mutations that cause both Sickle Cell Anemia (SCA) and Tay-Sachs disease, NPR reported.
“Prime editing is really a step—and potentially a significant step—towards this long-term aspiration of the field in which we are trying to be able to make just about any kind of DNA change that anyone wants at just about any site in the human genome,” Liu told News Medical.
Additional Research Required, but Results are Promising
Prime editing is very new and warrants further
investigation. The researchers plan to continue their work on the technology by
performing additional testing and exploring delivery mechanisms that could lead
to human therapeutic applications.
“Prime editing should be tested and optimized in as many cell types as researchers are interested in editing. Our initial study showed prime editing in four human cancer cell lines, as well as in post-mitotic primary mouse cortical neurons,” Liu told STAT. “The efficiency of prime editing varied quite a bit across these cell types, so illuminating the cell-type and cell-state determinants of prime editing outcomes is one focus of our current efforts.”
Although further research and clinical studies are needed to
confirm the viability of prime editing, clinical laboratories could benefit
from this technology. It’s worth watching.
Three innovative technologies utilizing CRISPR-Cas13, Cas12a, and Cas9 demonstrate how CRISPR might be used for more than gene editing, while highlighting potential to develop new diagnostics for both the medical laboratory and point-of-care (POC) testing markets
Now, scientists at three universities are investigating ways to expand CRISPR’s use. They are using CRISPR to develop new diagnostic tests, or to enhance the sensitivity of existing DNA tests.
One such advancement improves the sensitivity of SHERLOCK (Specific High Sensitivity Reporter unLOCKing), a CRISPR-based diagnostic tool developed by a team at MIT. The new development harnesses the DNA slicing traits of CRISPR to adapt it as a multifunctional tool capable of acting as a biosensor. This has resulted in a paper-strip test, much like a pregnancy test, that can that can “display test results for a single genetic signature,” according to MIT News.
Such a medical laboratory test would be highly useful during pandemics and in rural environments that lack critical resources, such as electricity and clean water.
One Hundred Times More Sensitive Medical Laboratory Tests!
MIT News highlighted the high specificity and ease-of-use of their system in detecting Zika and Dengue viruses simultaneously. However, researchers stated that the system can target any genetic sequence. “With the original SHERLOCK, we were detecting a single molecule in a microliter, but now we can achieve 100-fold greater sensitivity … That’s especially important for applications like detecting cell-free tumor DNA in blood samples, where the concentration of your target might be extremely low,” noted Abudayyeh.
“The [CRISPR] technology demonstrates potential for many healthcare applications, including diagnosing infections in patients and detecting mutations that confer drug resistance or cause cancer,” stated senior authorFeng Zhang, PhD. Zhang, shown above in the MIT lab named after him, is a Core Institute Member of the Broad Institute, Associate Professor in the departments of Brain and Cognitive Sciences and Biological Engineering at MIT, and a pioneer in the development of CRISPR gene-editing tools. (Photo copyright: MIT.)
They published the results of their development of CRISPR-mediated analog multi-event recording apparatus (CAMERA) systems, in Science. The story was also covered by STAT.
“The order of stimuli can be recorded through an overlapping guide RNA design and memories can be erased and re-recorded over multiple cycles,” the researchers noted. “CAMERA systems serve as ‘cell data recorders’ that write a history of endogenous or exogenous signaling events into permanent DNA sequence modifications in living cells.”
This creates a system much like the “black box” recorders in aircraft. However, using Cas9, data is recorded at the cellular level. “There are a lot of questions in cell biology where you’d like to know a cell’s history,” Liu told STAT.
While researchers acknowledge that any medical applications are in the far future, the technology holds the potential to capture and replay activity on the cellular level—a potentially powerful tool for oncologists, pathologists, and other medical specialists.
Using CRISPR to Detect Viruses and Infectious Diseases
Despite the current focus on HPVs, the researchers told Gizmodo they believe the same methods could identify other viral or bacterial infections, detect cancer biomarkers, and uncover chromosomal abnormalities.
Future Impact on Clinical Laboratories of CRISPR-based Diagnostics
Each of these new methods highlights the abilities of CRISPR both as a data generation tool and a biosensor. While still in the research phases, they offer yet another possibility of improving efficiency, targeting specific diseases and pathogens, and creating new assays and diagnostics to expand medical laboratory testing menus and power the precision medicine treatments of the future.
As CRISPR-based diagnostics mature, medical laboratory directors might find that new capabilities and assays featuring these technologies offer new avenues for remaining competitive and maintaining margins.
However, as SHERLOCK demonstrates, it also highlights the push for tests that produce results with high-specificity, but which do not require specialized medical laboratory training and expensive hardware to read. Similar approaches could power the next generation of POC tests, which certainly would affect the volume, and therefore the revenue, of independent clinical laboratories and hospital/health system core laboratories.
How SHERLOCK and CRISPR Differ and Why That’s Important
Scientists have long suspected that CRISPR could be used to detect viruses. However, far more attention has been given to the its genome editing capabilities. And, there are significant differences between how CRISPR and SHERLOCK work. According to the Science article, when CRISPR is used to edit genes, a small strip of RNA directs an enzyme capable of cutting DNA to a precise location within a genome. The enzyme that CRISPR uses is called Cas9 (CRISPR associated protein 9). It works like scissors, snipping the strand of DNA, so that it is either damaged or replaced by a healthy, new sequence.
SHERLOCK, however, uses a different enzyme—Cas13a (originally dubbed C2c2 by the researchers who discovered it). Cas13a goes to RNA, rather than DNA, and once it starts cutting, it doesn’t stop. It chops through any RNA it encounters. The researchers who developed SHERLOCK describe these cuts as “collateral cleavage.” According to an article published by STAT, “All that chopping generates a fluorescent signal that can be detected with a $200 device or, sometimes, with the naked eye.”
The screenshot above is from a video in which Feng Zhang, PhD (center), a Core Member of the Broad Institute at MIT and one of the lead researchers working on SHERLOCK, and his research team, explain the difference and value SHERLOCK will make in the detection of diseases like Zika. Click on the image above to watch the video. (Video copyright: Broad Institute/MIT.)
Early Stage Detection in Clinical Laboratories
A research paper published in Science states that SHERLOCK can provide “rapid DNA or RNA detection with attomolar sensitivity and single-base mismatch specificity.” Attomolar equates to about one part per quintillion—a billion-billion. According to the article on the topic also published in Science, “The detection sensitivity of the new CRISPR-Cas13a system for specific genetic material is one million times better than the most commonly used diagnostic technique.” Such sensitivity suggests that clinical laboratories could detect pathogens at earlier stages using SHERLOCK.
The Stat article notes that, along with sensitivity, SHERLOCK has specificity. It can detect a difference of a single nucleotide, such as the difference between the African and Asian strains of Zika (for example, the African strain has been shown to cause microcephaly, whereas the Asian strain does not). Thus, the combination of sensitivity and specificity could mean that SHERLOCK would be more accurate and faster than other diagnostic tests.
Clinicians in Remote Locations Could Diagnose and Treat Illness More Quickly
Perhaps one of the most important aspects of SHERLOCK is the portability and durability of the test. It can be performed on glass fiber paper and works even after the components have been freeze dried. “We showed that this system is very stable, so you can really put it on a piece of paper and it will survive. You don’t have to refrigerate it all the times,” stated Feng Zhang, PhD, in an interview with the Washington Post. Zhang is a Core Member of the Broad Institute at MIT and was one of the scientists who developed CRISPR.
The researchers note that SHERLOCK could cost as little as 61-cents per test to perform. For clinicians working in remote locations with little or no power, such a test could improve their ability to diagnose and treatment illness in the field and possibly save lives.
Anatomic pathologists and clinical laboratories will want to follow SHERLOCK’s development. It could be on the path to fundamentally transforming the way disease gets diagnosed in their laboratories and in the field.
According to the Post article, “The scientists have filed several US patent applications on SHERLOCK, including for uses in detecting viruses, bacteria, and cancer-causing mutations.” In addition to taking steps to secure patents on the technology, the researchers are exploring ways to commercialize their work, as well as discussing the possibility of launching a startup. However, before this technology can be used in medical laboratory testing, SHERLOCK will have to undergo the regulatory processes with various agencies, including applying for FDA approval.