Switch turns genes on or off, making gene therapy safer

Just as they adjust the dosage of a medicine to the patient’s needs, the expression of therapeutic genes, those modified in a person to treat or cure a disease through gene therapy, must also be kept within a therapeutic window. Staying within the therapeutic window is important as too much protein could be toxic and too little could result in little or no therapeutic effect.

Although the principle of therapeutic window has been known for a long time, there has been no strategy to implement it safely, which limits the possible applications of gene therapy in the clinic. Now, this work appears to have found a promising solution to fill this gap in the clinical applications of gene therapy.

“Although there are several genetic regulation systems used in mammalian cells, none have been approved for clinical applications, mainly because these systems use a regulatory protein foreign to the human body, which triggers an immune response against,” explains the researcher. Yen placement. “This means that the cells that express the therapeutic protein will be attacked, eliminated or neutralized by the patient’s immune systemrendering the therapy ineffective.

For more than a decade, Yen and his colleagues have been working on this technology and have now found a solution to overcome the main obstacles in its clinical use. “The solution we found does not involve a foreign regulatory protein that triggers an immune response in patients. “Instead, we use small molecules to interact with RNA, which do not normally trigger an immune response,” she says.

“Other groups have also tried to solve this critical problem, but the drug concentrations they used went beyond what has been approved for patients. We can design our system in such a way that it works with the dose approved by the FDA».

Scientists have developed a system that activates genes at different levels in a signal using small molecules at FDA-approved doses. The switch is placed in RNA, the copy of the genetic material that is translated into a protein. This approach allows researchers to take a step back in controlling the production of the protein by controlling its RNA.

ARREST

The RNA of interest is first designed to contain an additional polyA signal, similar to a «stop sign« that genes are naturally used to mark the end of a gene. When the cell’s machinery detects a polyA signal in the RNA, it automatically makes a cut and defines the cut point as the end of the RNA. “In our system, we use the polyA signal added, not to the end, but to the beginning of the RNA, so cleavage destroys the RNA and therefore the default is that no protein is produced. It turns off until we activate it with the small molecule,” Yen said.

To activate the gene to the desired level, the team designed a switch in the RNA. They modified a section of the RNA near the polyA signal so that it can now bind to a small molecule, in this case the FDA-approved tetracycline. “When the tetracycline It binds to that section that functions as a sensor of the RNA, masks the polyA signal and the RNA will now be translated into protein,” explains Yen.

In the future, a gene therapy patient that provides a gene to compensate for a defective disease-causing gene would have such a switch, which allows the doctor to control the production of the therapeutic protein. If the patient only needs a small amount of therapeutic protein, then he will only take a small dose of tetracycline, which will activate the therapeutic gene only a little. But if he needs a larger quantity, production will be increased. To stop the production of the therapeutic protein, the patient stops taking tetracycline.. In the absence of tetracycline, the switch will return to its default off position. Some diseases may benefit from the presence of constant low levels of therapeutic protein. In that case, the technology has the flexibility to pre-tune the default level to specific protein expression levels while retaining the option to augment expression with tetracycline.

«This strategy allows us to be more precise in controlling the gene expression of a therapeutic protein. It allows us to adjust its production according to the stages of the disease or adapt to the specific needs of patients, all using the FDA-approved dose of tetracycline,” highlights Yen.

Furthermore, he adds, such an approach is not disease-specific; In theory, he notes, “It can be used to regulate the expression of any protein and potentially has many therapeutic applications. Additionally, this system is more compact and easier to implement than existing technologies. Therefore, it can also be very useful in the laboratory to activate or deactivate a gene of interest to study its function.