Matthew B. Klein
Thanks, Joe, for the question. So, the PIVOT-HD study is a 12-month placebo controlled study that is in two parts. Part one is 12 weeks in duration, it focuses on PK PD in the blood, as well as biodistribution. Looking at the relative exposure in the CSF and in the plasma. These are important data points to inform optimal dose that gets us towards the target reduction in the brain and 30 to 50% of Huntington protein. The second 9 months of the study is focused on biomarkers of disease including Huntington protein levels and CSF, radiographic markers, including bringing volume changes as well as NFL levels in case and the CSF. The data we plan to share in the second quarter is an interim analysis from the first 12 weeks of PIVOT-HD. We will be sharing information on the PK/PD in a blood. So looking at blood, looking at drug levels in the blood and the reduction in Huntington mRNA protein one and then looking at the relative exposure of the CSF in the plasma. As you recall from our Phase 1 healthy volunteers study, we're able to confirm that we were getting excellent CNS exposure. And in fact, achieving greater exposure in the CSF than in the plasma. So that's a very important finding that will seek to confirm the trove of data of the biomarker data including the CSF, Huntington protein levels, NFL levels, and brain volume changes will come up in the readout from the 12-onth data. To your second question regarding patient populations. As I shared, answering Kristen's question, the mechanism of the drug is targeting the production of the disease causing mutant Huntington protein. That is by leveraging splicing, we're able to introduce a stop codon that effectively decreases the production of that disease causing protein. Obviously, that holds promise for the full spectrum of HD patients, and whether they be juvenile or adult patient, given that the disease causes the same in all cases. However, it's obviously incredibly important in conducting a clinical trial that we try to include the right study population to whom we could practically capture clinical effects. And in the case of the PIVOT-HD study, biomarker effect, along the -- in the time limited constraints on a clinical trial. So we put a lot of effort into identifying the attributes of what we felt would be that optimal population. We availed ourselves and the robust Huntington disease natural history database is to work closely with Huntington's disease experts in biostatisticians, who support these databases, to come up with what we thought were the essential attributes of a study population that would likely to decline over the course of a clinical trial. Obviously, we want patients who are not so advanced in their disease, that by targeting the upstream cause of the disease, we can practically deliver a benefit. And we certainly don't want patients who are so early in disease, that they're not progressing at all right. Therefore, making it impossible to show that we're slowing disease progression. So we put these attributes can play at our inclusion criteria for the study, these were essentially Stage 2 HD patients. We shared at the JP Morgan conference in January, that we were adding additional cohorts on slightly later stage patients. We were now including patients with who had a total functional capacity score of 11 and 12, rather than just simply having a TFC score of 13, which was initially acquired. The reasons for this were because there were a number of these patients who were identified some pre-screened and prepared to participate in other clinical trials that were no longer being conducted. So anyway, a situation where there are patients identified but it could be in clinical trials, incredibly eager to participate in clinical trials and whom we obviously believe we could have provided benefit with this therapy. So maybe decision to introduce additional dosing cohorts, 5 milligrams, 10 milligram dosing cohorts in these early Stage 3 patients, because this will provide us additional important data on potential benefit of PTC508. And will also allow us to test our hypothesis in terms of the awful population that we initially set out to enroll. So I hope that answers your question on the adjustments or the addition of the patient.