GenSight Biologics has recently released data showing the effectiveness of GS010, the company’s gene therapy for Leber Hereditary Optic Neuropathy (LHON), a mitochondrial disease that can lead to blindness. Like in previous studies, this therapy had a bilateral effect.
Gene Therapy
In LHON, the mitochondrial protein ND4 is poorly expressed through mitochondrial DNA (mtDNA). GS010 is a gene therapy that causes this protein to be allotropically expressed in the nucleus, after which it is shuttled to the mitochondria through messenger RNA. This makes GS010 a partial treatment for mitochondrial dysfunction, which is one of the hallmarks of aging.
RESCUE and REVERSE
We previously reported the results of GenSight’s REVERSE trial, which studied the effects of GS010 on people whose onset of LHON was between 6 and 12 months ago. RESCUE, by comparison, studied patients with LHON onset of 6 months or less. The studies are nearly identical otherwise, with REVERSE studying 37 patients and RESCUE studying 39.
GenSight’s data shows a similarity in disease progression between the two trials. The relevant graph shows that REVERSE may be more effective than RESCUE, and both injected and sham eyes continued to fail in the RESCUE trial before rebounding from a nadir. This suggests a time-dependent effect and will surely affect the development of future therapies based on GS010.
Bilateral Improvement
Both trials supported the company’s contention that a single injection into one eye affected both eyes, as sham-injected eyes performed only slightly worse than the corresponding treated eyes in both RESCUE and REVERSE. This bilateral improvement make the clinical effectiveness of GS010 less clear, however; neither trial employed pure control groups that did not have GS010 administration at all, as to do so would be to leave participants in these groups completely blind.
As with its REVERSE trial, the company noted the differences between GS010-treated eyes and those of patients in previous natural history studies, and the comparison was approximately as encouraging.
Forward Progress
The company is attempting to bring GS010 to market despite its difficulties in testing; it will have a meeting with the FDA next month and plans on meeting with the EMA (European Medical Agency) in early 2020, with the intent ot submitting a marketing application for European markets in the third quarter of 2020. We hope for GenSight’s success in this endeavor, and not only for the sake of people suffering from LHON, as it demonstrates that targeting mitochondrial dysfunction is a valid approach for therapies.
One of Many Genes
While GenSight’s approach works on ND4, there are many other genes in the mitochondria that could be better protected in the nucleus. If we were to allotropically expressing these genes there, rather than the mitochondria themselves, this would obviate the need for mtDNA at all, finishing the job that evolution started.
Our current MitoMouse campaign focuses on another mitochondrial gene, ATP8; similar to what GenSight is doing, allotropically expressing ATP8 in the nucleus would be a solution for even more mitochondrial disorders, including those caused by aging. Your donations help to make MitoMouse a reality, proving the concept of this therapy and bringing a swifter end to mitochondrial dysfunction.
