This restores frataxin levels and therefore cellular health. Now, for the other side of the platform, long repeat expansions in regions of genes are shown in red in the upper half. This is the case in diseases like Fuchs Endothelial Corneal Dystrophy and Myotonic Dystrophy. Repeat expansions in coding regions of genes are shown in the lower half in red, as is the case in Huntington’s Disease, and it only takes one allele to cause the disease. So patient has one wild type allele shown in the strand without the red, and a mutant allele shown in the strand with the red expanded regions. Now in the upper half, this mutant allele is transcribed by RNA polymerase to create RNA, which then folds over on itself causes tangles and sequesters MBNL proteins.
This causes nuclear foci and — osteopathy and other cellular dysfunction. Now in the lower half, the RNA is transcribed and then translated by ribosomes to make toxic mutant proteins. These proteins cause toxic aggregates, as is the case in Mutant Huntington protein causing Huntington’s Disease. GeneTAC molecules selectively target these abnormal alleles at the repeat expansions shown in red, and they dial down transcription of toxic mutant gene products and thereby restore cellular health. The wild type alleles continue to function normally. This slide summarizes the mechanism of action that we’ve just reviewed in the animation. And now for a deeper dive into our FA program. The root cause of FA lies in the single gene frataxin. It’s the reduction in frataxin expression that causes the dysfunction, whether it’s in the C&S, musculoskeletal tissues, cardiac hypertrophy, or metabolic problems that patients face.
When we look at frataxin levels in [Audio Gap] healthy individuals, carriers and patients, we see that carriers have approximately half the level of their frataxin is indicated by the black line representing the group average, carriers do not have FA and have no disease burden. FA patients have a quarter to a fifth of normal frataxin levels on average. Of course, around every mean is a distribution, and there may be individuals who are above or below the mean and different individuals might require different levels of restoration to get back into the normal zone, which is somewhere near carrier levels. And that is the therapeutic goal, which is thought to be about a doubling. Now, most of the general population has less than 34 GA repeats in their frataxin gene, but someone with FA has 400 or over a 1,000 and these repeats reduce the level of normal frataxin, and it turns out you can measure this reduction with a blood test.
What’s shown on the top right is a result of a PCR test conducted on blood cells from patients. You can see in the gray bar on the graph that RNA levels are low in patient cells when compared with frataxin from an unaffected sibling who has two normal copies of the frataxin gene. You can imagine our excitement when we were able to observe that when cells from patients are incubated with GeneTAC molecules, there’s a restoration of frataxin to normal levels in a dose dependent fashion. And when cells from unaffected siblings are incubated with the compounds, the frataxin levels remain unaltered. This is exactly what one would wish for an FA, a medicine that restores natural levels of the single gene product that causes all of these problems. And that’s what’s so exciting about Design, is we have an opportunity to provide a restorative therapy of natural frataxin from the patient’s own genes and to do it with a small molecule.
Now, we’ve seen that this effect is observed in a wide variety of cell types tested shown here is the result of treating terminally differentiated neurons taken from patient derived IPS cells. On the left is an increase in frataxin RNA, and on the right is an increase in frataxin protein, which follows a few days later and has a long half-life of several days. DT-216 was taken into clinical trials in patients with FA in 2022 and ‘23 with a prior formulation and the trial design is shown here. We learned from the human studies that the duration of adequate levels of exposure of DT-216 was much shorter than expected. While we knew that the drug was short-lived in plasma. Human studies showed by muscle biopsy that it was also short-lived in tissue and that what you observe in plasma is predictive of what is observed in tissue.
The tissue levels from human muscle biopsies were approximately only eight to 10 nanomolar at day two, and the drug was almost gone with levels of one nanomolar by day seven. Well, despite that, there was a clear increase in frataxin expression observed in treated patients in a dose dependent fashion with one patient frataxin level, going to clinically normal carrier levels as shown in the right. However, the effect was transient because the drug exposure was transient, so we needed to develop a new drug product that could sustain this drug exposure. While the drug was generally well tolerated, there were injection site thrombophlebitis events observed, which limited the frequency and levels of dosing with the prior product candidate. Nonclinical studies showed that these reactions were attributable to the formulation excipients in the drug product.
We have now conducted new non GLP animal studies with DT-216P2, which lead us to believe that these issues have now been solved and we can progress to confirmatory GLP studies to get back into the clinic. Furthermore, this new drug product appears suitable for IV administration, compatible with injections or infusions, peripheral or central, and also appears suitable for a subcutaneous route of administration. As we showed in the beginning, the new drug product, DT-216P2 has a much more sustained exposure profile as seen in the single dose ID PK curve from non-human primates. You can see between day one and day seven, the levels are 10 to perhaps a hundred-fold higher than the prior drug product, even with a quarter to approximately a 10th of the reference dose.
