James Dentzer
Analyst · Bill Jahangiri with Truist
Yes. Thank you. Appreciate it, Bill, and thanks for joining us. So let me try and knock off those 3 questions in a row. So first, the split on FLT3 patients versus spliceosome patients. So this one is really, really interesting. And I think it reflects the unmet need in AML. Both of these studies are recruiting quickly. As you may recall, we came off our partial clinical hold midyear last year, got our sites up and running. And we are seeing really strong enrollment rates across the board at our sites. There's a real pent-up demand in AML for a novel target.
In particular, as you note, the pace of spliceosome has been really interesting. So FLT3 constitutes roughly 1/3 of AML. 1/3 of AML patients have a FLT3 mutation. Patients with a splicing factor mutation make up a much smaller portion of that community. Maybe 10% of AML patients have a splicing factor mutation. And yet, that has outpaced enrollment in FLT3. And I think it's precisely what we said. There are no drugs available. Not only is nothing approved, nothing works for these patients. This is the first time people are seeing activity. And to see that kind of activity with a single agent is really compelling.
So we look forward to sharing our results with you next week in those 2 populations. And we look forward in having the discussions with FDA as well. We've got to our data set in 20 patients with spliceosome. We're going to add another couple in FLT3 and follow these patients and take those data to the FDA and begin the discussions on registrational design, and we're looking forward to that.
The second question was about triplet safety. So the design of this study, as you may remember, I think, is really interesting, and it's all about, as I mentioned to Yale, ensuring that our leukemia program is partner ready. So we will have, by year-end, mature data sets in 2 distinct genetically driven populations in FLT3 and splicing factor mutation. The study we just started in triplet is a study that enrolls patients who are currently on aza-ven in the frontline setting who have achieved CR but are still MRD positive. We're going to then take those patients into the study and add emavusertib to their therapy, turning the doublet into a triplet.
Of course, what we're hoping is that we can see efficacy and get those patients to MRD negativity. But the key is that we will have been able to isolate the safety effect of adding emavusertib to that aza-ven doublet, to the current standard of care, so that by the time we get to year-end -- obviously, we're always hoping to see signs of efficacy. But what we really want to be able to say is we've got a drug that's hitting a novel target in IRAK4. That novel target clearly matters because we're seeing single-agent activity. We know that the existing standard of care of aza-ven doesn't hit it. And then we hope to add to the discussion by year-end, we can add a drug, emavusertib, to that doublet that allows the current standard of care to address this new novel target of IRAK4, and we would hope, of course, that we would then see in the clinic, in that setting, what we saw in the preclinical data, which is we have the potential to establish a new benchmark and establish a new standard of care in frontline therapy and AML across the board, all comers, FLT3 mutation or not.
Then your third question was on BTK-naive patients in the study in lymphoma. So just as a reminder, we have tested the combination of emavusertib with ibrutinib in multiple indications within NHL, and specifically with primary CNS lymphoma in BTK-naive patients as well as BTK-experienced patients. The underlying logic of the drug is that patients who are on ibrutinib or NHL patients who are on ibrutinib are on it precisely because it allows them to downregulate NF-kappaB over activity by blocking the BCR pathway.
There are 2 pathways that are driving NF-kappaB overactivity in these patients. There are a lot of BTK inhibitors today. There's only one drug that blocks TLR pathway, that second pathway driving NF-kappaB overactivity, and that's emavusertib.
Our view would be blocking both of those pathways that are driving NF-kappaB, which is driving disease in NHL, blocking both pathways is always going to be better than blocking either one alone. So if we can then take that mechanistic logic into the preclinical setting and see the hypothesis is supported, which we've already done, and now go into the clinic and compare and contrast, as you say, BTK-naive and BTK-experienced patients, being able to show both as good, and we already have.
But we think it's even more powerful -- if all we had were BTK-naive patients, someone might wonder whether the efficacy was coming from the BTK inhibitor. But because we know these patients are on a BTK and then fail, either relapsed or refractory, you would, of course, expect that to immediately rechallenge them with ibrutinib yet again, the response rate is probably going to be 0.
So if we can show that we can get activity in those patients, even though they've just failed BTK, then it's obviously either the performance of emavusertib alone or emavusertib's synergistic combination with BTK and its ability to resensitize patients to BTK that is driving that. And so we think that's a really powerful thing to do. Thank you for asking that question. That was pretty long. I hope it answered your question thoroughly.