Over ten years ago two Nobel-Prize-winning biologists, Emmanuelle Charpentier and Jennifer Doudna, discovered a technology called CRISPR (clustered regularly interspaced short palindromic repeats). Bacteria contain genetic sequences repeated throughout their genes.
CRISPR treats diseases by removing a number of the patient’s cells and editing those cells in the lab. Using CRISPR technology, the scientists correct the genetic defect and reinsert the cells back into the body.
According to a recent article in Popular Science, that was just the beginning. This year, thanks to continued experimenting by researchers all over the world, CRISPR again made headlines. This time with a new technology that called for DNA editing straight into the bloodstream. Not only does this method cost less, but it can also treat a greater number of diseases. There are, however, certain risks including the inadvertent editing of healthy genes.
Another First
Last month the NE Journal of Medicine reported a six-patient study of a genetic disease called transthyretin amyloidosis. The disease is rare and is responsible for the buildup of amyloid, a defective protein that causes nerve damage and heart failure. It is usually fatal within twelve years after symptoms appear.
A new therapeutic approach based on CRISPR, called NTLA-2001, is delivered by intravenous infusion. It is a first for precision editing of a gene focused on target tissue in humans.
The technology was packaged inside a tiny lipid nanoparticle and transported directly to the liver where transthyretin (defective protein) is produced. CRISPR then continues to inactivate the defective cells and thus prevent the misfolded protein, transthyretin, from being produced.
The end result is that the liver produces a corrected version of transthyretin. The data were published in the NE Journal of Medicine.
It was the intent of the researchers to study the treatment’s safety factors. However, noting that excess amyloid results in characteristic symptoms, any lessening of these symptoms that occurred during the trial suggests that the treatment was effective.
More About the Study
Three study participants received a low dose of CRISPR-lipid nanoparticles. The remaining three received a somewhat higher dose.
The study results showed defective liver cells decreasing by almost fifty percent in participants who received the lower dose.
The second group who received a higher dose saw defective cells reduced by ninety percent.
The study thus far has produced positive results and is ongoing with continued testing for safety and effectiveness at even higher levels. The participants will be monitored for long-term effects for at least two years after treatment. One of the concerns would be cancer as the result of inadvertent gene changes.
Remembering A Virus
Bacteria stores genetic sequences of viruses and by doing so “remembers” that virus so that it attacks when the virus tries to invade again. The Cas-9 (CRISPR-associated) protein cuts up the genetic material belonging to the invading viruses.
How to Overcome the Potential for Harm
One of the most important benefits of CRISPR’s new technology is that it can reach most of the liver cells. It is possible to edit liver cells in other ways, for instance outside of the body, but doctors cannot take out someone’s liver to edit each cell.
When the cells are edited inside the body it is not possible to tell if or when something is wrong. Researchers relied on computer programs to detect vulnerable areas that are at risk for inappropriate targeting by CRISPR.
Looking Forward
Immunotherapy treatments utilizing CRISPR technology are currently being tested with the goal of altering the immune cells so that they will be more effective in killing cancer.
Intellia Therapeutics led the development of NTLA-2001 and funded the study together with Regeneron. Intellia has now developed another version of the drug to treat a genetic disease called angioedema which they intend to test on humans.
The researchers involved with the study agree that gene editing is a major player in medicine now, and in the future. They believe there is potential for CRISPR to address incurable diseases such as Alzheimer’s and Huntington’s disease.
