Voyager Therapeutics Inc

NASDAQ:VYGR

Earnings Call Analysis

Voyager Therapeutics Advances Alzheimer's Programs and Maintains Strong Cash Position

Voyager Therapeutics is making promising strides in its Alzheimer's programs, specifically VY7523, an anti-tau antibody, which recently completed its initial trial phase. With encouraging data supporting its efficacy against tau accumulation, the company anticipates initiating a multiple ascending dose trial next year and aims for IND filings for three gene therapy programs in 2025. Their platform, TRACER, is key to these advancements. Voyager retains a strong cash position of $345 million, providing operational runway through 2027, while focusing on critical partnerships that enhance their innovation in neurogenetic medicine.

Voyager Therapeutics' Vision for Alzheimer's Treatment

Voyager Therapeutics aims to revolutionize the treatment landscape for Alzheimer's disease by focusing on two key approaches: an anti-tau antibody known as VY7523 and a tau silencing gene therapy. Both strategies target tau protein, which is crucial in the disease's progression. Their innovative pipeline includes 4 wholly owned and 14 partnered programs, backed by leading industry partnerships.

Positive Momentum from VY7523 Trials

In the recent quarter, Voyager completed the dosing trial for VY7523, their anti-tau antibody. Preliminary results are anticipated in the first half of 2025, which will include safety and pharmacokinetic data from a single ascending dose study in healthy volunteers. Importantly, a multiple ascending dose trial in Alzheimer's patients is expected to begin next year, providing further insights into clinical efficacy.

Significant Third-Party Data Enhancing Confidence

The company's optimism is buoyed by recent data presented at the CTAD meeting, showcasing UCB's bepranemab, which inhibited tau accumulation in the brain by 33% to 58% and lowered cognitive decline by 21% to 25% per ADAS-Cog14. These findings validate the potential of the anti-tau approach, suggesting that VY7523 may offer similar or enhanced benefits.

Financial Health and Strategic Partnerships

As of the third quarter of 2024, Voyager reports a cash position of $345 million, providing a runway into 2027. This financial stability is critical for advancing their therapeutic pipeline and includes contributions from significant partnerships with companies like Novartis, enabling continuous progress in their development programs. The company is actively leveraging its TRACER platform for CNS-targeted gene therapy, expecting to file INDs for three additional programs next year.

Anticipated Milestones and Market Position

Voyager anticipates substantial clinical milestones over the next 12 to 24 months, which may catalyze significant value creation for investors. The strategic positioning in the neurological disease market, particularly Alzheimer's, is supported by promising therapy pipelines targeting tau proteins, coupled with a strong cash base and potential future revenue from partner collaborations.

Projected Growth and Future Outlook

Looking ahead, Voyager is on track to produce initial data from their tau PET imaging studies by the latter half of 2026, contributing to an evolving understanding of tau's role in Alzheimer's. Their ongoing studies aim to refine patient selection criteria based on tau burden, enhancing the efficacy of their treatments. This precision approach may unlock superior therapeutic outcomes compared to existing anti-amyloid therapies.

Earnings Call Transcript 2024-Q3

[Operator]

Good afternoon, and welcome to the Voyager Therapeutics Third Quarter 2024 Financial Results Conference Call. [Operator Instructions] Please note that today's call is being recorded. A replay of today's call will be available on the Investors section of the company website approximately 2 hours after completion of this call.

I would now like to turn the call over to Trista Morrison, Chief Corporate Affairs Officer at Voyager.

[Trista Morrison, executive]

Thank you, and good afternoon. We issued our third quarter 2024 financial results press release this afternoon. The press release and 10-Q are available on our website.

Joining me on today's call are Dr. Al Sandrock, our Chief Executive Officer; Dr. Toby Ferguson, our Chief Medical Officer; and Dr. Todd Carter, our Chief Scientific Officer. We will also be joined for the Q&A portion of the call by Nathan Jorgensen, our Chief Financial Officer.

Before we get started, I would like to remind everyone that during this call, Voyager representatives may make forward-looking statements as noted in Slide 2 of today's deck. These statements are based on our current expectations and beliefs. They are subject to risks and uncertainties, and our actual results may differ materially. I encourage you to consult the risk factors discussed in our SEC filings, which are available on our website for additional detail.

Now I will turn the call over to Al.

[Alfred Sandrock, executive]

Good afternoon, everyone, and thank you for joining us.

Please turn to Slide 3. At Voyager, we are leveraging the power of human genetics to discover and deliver transformative medicines that address the root cause of neurological diseases. Our 4 pillars of value include: first, our pipeline of 4 wholly owned and 14 partnered programs. During the third quarter, we completed enrollment and dosing in the single ascending dose trial of VY7523, our anti-tau antibody for Alzheimer's disease. We also recently saw encouraging third-party clinical data with another anti-tau antibody for Alzheimer's disease, which Toby will talk about shortly.

Our second pillar of value is our industry-leading TRACER platform for the discovery of novel AAV capsids to enable CNS gene therapy. These IV-delivered CNS-targeted capsids underlie all of our wholly owned and partnered gene therapy programs, and we expect INDs for 3 of these programs next year. Third, we have blue-chip partnerships with some of the world's experts in neurology and gene therapy, including Neurocrine, Novartis and Alexion. We continue to progress these partnerships through the third quarter with Novartis signing on for a fifth program partnership and Neurocrine nominating a third development candidate.

Finally, we continue to explore the potential to leverage receptors we have identified to shuttle nonviral genetic medicines into the brain. Ultimately, we aim to expand from gene therapy and antibodies into other modalities of neurogenetic medicine, broadening our impact.

With that, I'll turn the call over to Toby to talk more about our anti-tau antibody and some of the recent third-party data in the space.

[Toby Ferguson, executive]

Thanks, Al, and good afternoon. Please turn to Slide 4. This slide summarizes the 4 wholly owned programs and 14 partner programs that Al mentioned earlier. Today, we are going to focus on our tau-targeting programs for Alzheimer's disease.

Turning to Slide 5. The point I want to make here is that we view tau as a critically important target for the treatment of Alzheimer's disease. As you can see in the image on the left of this slide, the spread of pathological tau, as identified on tau PET imaging, correlates closely to Alzheimer's disease progression as measured by Braak clinical pathologic staging.

Additionally, exploratory clinical data from Biogen's BIIB080 tau knockdown program showed a reduction in pathological tau, as well as potentially greater slowing of clinical disease progression than seen with anti-amyloid antibodies. So in short, we think targeting tau has the potential to impact Alzheimer's disease progression and do so in a significant way. This is why Voyager is pursuing 2 approaches to targeting tau, our anti-tau antibody VY7523 and our tau silencing gene therapy.

On Slide 6, I want to highlight how the team selected our anti-tau antibody. We started with more than 700 antibodies across the mid-domain and C-terminus of tau. We first focused on antibodies targeting pathological tau. This was important with the anti-amyloid antibodies. Several that failed, such as solanezumab or bapineuzumab, were shown to have insufficient target engagement with aggregated forms of amyloid beta, while the approved anti-amyloid antibodies all target the aggregated species. We narrowed the funnel through further in vitro and in vivo studies. We evaluated antibodies targeting various epitopes across tau, including in the mid-domain and the C-terminus. In a mouse seeding model of human pathological tau spread, the C-terminal targeted antibody, Ab-01, the murine version of VY7523, decreased the spread of injected pathological human tau by approximately 70%.

Based on these data and the specificity for pathological tau, we selected VY7523 as our clinical candidate. We also conducted a series of head-to-head studies in the same model against other anti-tau antibodies. These data are summarized on Slide 7. In the first head-to-head study, we evaluated murine VY7523 against murine versions of Biogen's gosuranemab and Lilly's zagotenemab. These antibodies both targeted the N-terminus of tau, and both failed the primary endpoints in clinical trials. Both were ineffective at reducing tau spread in the model, while our C-terminal targeted antibody again blocked tau spread. This gave us confidence that the model had negative predictive value. In the second head-to-head study, we compared our C-terminal targeted antibody to UCB's bepranemab, which targets the mid-domain. In our models, both antibodies inhibited tau spread. Based on these data, we were eager to see the results from the bepranemab clinical trial, because we thought that if this antibody could impact tau in a clinical trial, then our model might also have positive predictive value.

Turning to Slide 8, I want to summarize the recent bepranemab data shared at the 2024 CTAD meeting. I want to start by noting that the primary endpoint, CDR sum of boxes, was not met in the full study population. This is important to acknowledge. Now I would like to note that bepranemab inhibited the accumulation of tau in the human brain by 33% to 58%. We saw this as establishing that an antibody can be used to inhibit the spread of pathological tau in the brain. This finding should not be underestimated, as I think that after the failure of the N-terminal anti-tau antibodies, there was uncertainty in industry as to whether an antibody approach could impact tau accumulation.

As it turns out, it can. I also want to note that bepranemab slowed cognitive decline by 21% to 25% versus placebo per ADAS-Cog14. Additionally, in subgroup analyses, it seems that patients with the greatest reduction in tau burden had more consistent clinical benefit, although we will need to see more detailed PK/PD and PD clinical correlation analyses. Finally, bepranemab demonstrated an acceptable safety profile with brain hemorrhagic and inflammatory changes similar to placebo.

What does this mean for Voyager's VY7523? I would say that these data give us increasing confidence that antibody targeting the appropriate epitope of tau can slow the accumulation of tau in the brain of Alzheimer's patients, and that this slowing may offer a clinically significant benefit in some patients. This was a top line data presentation, and there is certainly more work to be done here, and we look forward to seeing the additional data.

Slide 9 provides an overview of our Phase I clinical development plan for VY7523. During the third quarter, we completed enrollment and dosing of healthy volunteers on our single ascending dose trial. We expect to report top line safety and pharmacokinetic data in the first half of next year. We expect to initiate a multiple ascending dose trial in patients with early Alzheimer's disease next year and generate initial tau PET imaging data in the second half of 2026. At this point, we don't see anything in the bepranemab data that would shift our thinking here. If anything, the data reaffirmed that tau PET imaging is the critical outcome we want to focus on, and we have planned a very efficient trial focused on that outcome. We found the safety profile of bepranemab encouraging and look forward to exploring the full range of dosing possibilities. I mentioned earlier that we are advancing 2 approaches to targeting tau for Alzheimer's disease. We focused a lot on the antibody approach today in light of the recent third-party data, but I will now turn the call over to Todd to touch on our other approach.

[Todd Carter, executive]

Thanks, Toby. Please turn to Slide 10. In addition to our antibody-based approach, we are also advancing a tau silencing gene therapy program. This program deploys a tau-targeted siRNA packaged in an IV-administered TRACER capsid. Using this approach, we have demonstrated robust reductions in human tau mRNA and protein across the brain following a single IV administration in mice that express human tau, as shown on this slide. It is also important to note that the recent BIIB080 data that Toby mentioned showed that reducing tau expression was associated with favorable trends on clinical outcomes and pathological tau as measured by PET imaging. We view these data as supportive for a knockdown approach and believe that a onetime IV gene therapy could provide benefits over repeated intrathecal therapy. This program remains on track for U.S. IND and Health Canada CTA filings in 2026.

I will now turn the call back over to Al.

[Alfred Sandrock, executive]

Thanks, Todd. As you can see on Slide 11, Voyager continues to deliver on expectations for 2024. We have advanced our pipeline, our platform, and our partnerships. Our strong cash position of $345 million at the end of the third quarter is expected to provide runway into 2027, enabling multiple data readouts. This cash figure doesn't include the recent payments from Novartis or Neurocrine, which were received in October, nor does it contemplate any future potential milestones from our 14 partnered programs. With a robust slate of clinical milestones expected into the next 12 months to 24 months, a maturing partnership portfolio with top-tier collaborators, and cash runway into 2027, we believe Voyager is poised to drive significant value creation over both the near and long-term. Finally, I'd like to thank all of our employees for their hard work and dedication to improving the lives of patients.

With that, we will open the call for questions. Operator?

[Operator]

[Operator Instructions] Our first question comes from Phil Nadeau at TD Cowen.

[Philip Nadeau, analyst]

Congrats on the progress. I guess, first a follow-up to your comments on the tau PET imaging. We're curious whether you have more insight as to how to translate the tau PET imaging results like we saw from Roche/UCB into cognitive improvements, and any additional thoughts now that you've had a bit more time to let the CTAD data set in? Do you think it's a question of selecting the right patients, selecting the right endpoint? And any thoughts on how to get that tau PET imaging data to translate into a clinical improvement in cognitive benefits?

[Toby Ferguson, executive]

So maybe I'll start that question. This is Toby. So I think fundamentally, I think that I'll reemphasize the point that the tau PET imaging, we saw clear data in the whole population that you did not -- you slow the accumulation of tau. And then I think the other point I'd make is that when you look in some of the other populations, particularly the lower tau populations, you saw perhaps a slightly greater lesson of accumulation in that context. So I do think as we move forward, really understanding the population will be critical in the terms of perhaps tau burden, which seems to be the main point. And then I think the other point I think is we'll look forward to understanding the full dose response in terms of sort of the tau reduction in the context of PK/PD, we look forward to that data from UCB moving forward. I think those are my initial thoughts.

[Alfred Sandrock, executive]

I would just add that, this relationship between tau PET effects and disease effects on clinical outcomes are agnostic to the drug or to the approach, right? So there are more than one -- there is more than one drug targeting tau over the next couple of years. I think we'll learn this relationship better, what degree of tau PET imaging translates to what clinical outcome. And I agree with Toby that selecting the right patients, particularly with respect to tau burden, for example, may be very important.

[Philip Nadeau, analyst]

Perfect. And then a follow-up on the SOD1 silencing gene therapy for ALS, you note in the press release and in your prepared remarks that the initial trial could generate proof-of-concept based on biomarkers. Is that something that we could possibly see in 2026? Is that something that's within 12 months of the U.S. IND?

[Toby Ferguson, executive]

So we haven't guided to timing of the biomarker results. The points I can make is that, one, we'll go into the SOD1 population, of course, and two, we'll start in -- at doses we think are potentially efficacious given the severity of the disease. In that context, we do think results would be reasonably forthcoming.

[Alfred Sandrock, executive]

And maybe I could add that certainly in the case of the tofersen clinical development plan, and the trials that have been published in the New England Journal, you can start to see effects on SOD1 levels in spinal fluid in about -- is it 12 weeks?

[Toby Ferguson, executive]

About 12 weeks.

[Alfred Sandrock, executive]

12 weeks, Toby, yes. And then effects on plasma neurofilament, which is a surrogate outcome that's reasonably likely to predict clinical outcomes and was the basis of approval by FDA of tofersen. That measurement should also yield data in the first, say, 6 months or so. So if that's any precedent, that gives you an idea of the timing that it takes to see both biological effect and the outcomes on clinically relevant surrogate outcomes like NfL.

[Philip Nadeau, analyst]

Last question, an accounting question from us. The $15 million from Novartis and $3 million from Neurocrine, how will those be booked? Are those going to be booked in the fourth quarter of this year or will they be spread out over the life of those agreements?

[Nathan Jorgensen, executive]

It will be booked in the fourth quarter.

[Operator]

Our next question comes from Jack Allen at Baird.

[Jack Allen, analyst]

Great. Congrats on the progress. I wanted to ask about an aspect of the Voyager story that's more in its infancy, and that being the blood-brain shuttle programs. I was hoping you could just provide some context as to where those programs sit and when you maybe could look to bring an asset into the clinic. I know there's been a lot of activity in the space with AbbVie's acquisition of Aliada and then also Roche providing some initial proof-of-concept data from their beta amyloid asset there as well.

[Alfred Sandrock, executive]

Well, Jack, I'll start and I'll ask Todd to provide more color. But I would say that we're very excited about the potential of leveraging the receptors we identify through our capsids to shuttle other sort of macromolecules across the BBB. And as you pointed out, trontinemab, the data with trontinemab, which leverages transferrin receptors, looking very promising as an approach to get anti-amyloid antibodies into the brain. And so we're very excited about that. We're still in the preclinical stages. We haven't been -- we're not close enough to the clinic yet to guide on when we would enter the clinic. Todd, do you want to provide more color on that?

[Todd Carter, executive]

Thanks, Al. So, Jack, as you do point out, we are excited by it. We know that these receptors, and we do have different receptors in different capsid families, they can mediate transcytosis delivery across the blood-brain barrier for a large molecule, the AAV capsid. So there's reason to believe that they should be able to deliver other things. Hopefully in the future, we'll be able to share data on that. I think the other aspect is that we're seeing with receptors such as transferrin that there's the opportunity for additional receptors to have an impact because we expect that each receptor could have its own profile, both for pharmacokinetics and safety that could really give an opportunity for different receptors, for different diseases and indications.

[Jack Allen, analyst]

Great. That's great context. Maybe just one brief follow-up. You've been incredibly successful in partnering your gene therapy library of capsids, even in the context of using preclinical assets. Any comments as it relates to potential partnerships around the blood-brain shuttle programs? And is that thing you have an appetite for before moving this into the clinic?

[Alfred Sandrock, executive]

Well, Jack, this is Al. Yes, I mean, I'm always interested and willing to talk to potential partners. This is exactly the kind of thing where there could be expertise in other companies that could really be very complementary to our shuttle program. So always opening -- always open to talking to potential partners about these kinds of things and really accelerate the program.

[Operator]

Our next question comes from Joon Lee at Truist Securities.

[Joon Lee, analyst]

Congrats on the progress. Your plans for VY7523 MAD study in 2025 imply that you may be seeing something positive in SAD study or am I being too liberal with my interpretation? And so the SAD study due in first half of '25, in addition to safety, what are you tracking that could give us some incremental conviction on the drug?

[Toby Ferguson, executive]

Joon, it's Toby. Thank you for the question. Just to remind, the SAD study is in healthy volunteers. And so really the data we're looking from the SAD study is PK, initial immunogenicity, and do we have the appropriate exposures to pick doses for the MAD study and some initial read on safety. So really it's not a -- it's not in patients, that's the key point.

[Operator]

Our next question comes from Jay Olson at Oppenheimer.

[Jay Olson, analyst]

Congrats on the progress and thanks for providing this update. We have a few questions. Based on the bepranemab data that you saw, what's your latest thinking on the potential read across to your own VY7523 program? And is there any additional data from UCB that you would be interested in seeing? And then I have a follow-up.

[Alfred Sandrock, executive]

Well, look, I think, Jay, this is Al. I mean, this is the first time we've seen that an antibody could have biological effects in the brain in humans, right? And so that's -- I look on that as positive, right, that an antibody approach could affect the biology of tau spreading in the brain. We -- even before we knew about the bepranemab data, we did say that there could be read-through because we had tested the UCB antibody, which binds to a mid-domain region versus our antibody, which binds to the C-terminal region in an animal where we look for the -- we look at the spread of pathological tau in a mouse-expressing human tau where we inject pathological tau from Alzheimer's brains into the animal. And we said before the CTAD, before we knew anything about the bepranemab data that the UCB antibody was pretty comparable to our antibody in blocking the spread and actually distinguishable from the N-terminal directed antibodies that did not block the spread in that same model and which also failed in the clinic.

So -- and so we still believe that there could be read-through. And we also expect that the safety perhaps would also be similar in the sense that the antibody is binding to extracellular tau. I would say the other differentiating feature of our antibody relative to the UCB antibody is the fact that our antibody is specific for pathological forms of tau. We don't know how important that is. We'll find out, but that is another distinguishing feature. So that's where we stand, Jay. Todd, do you want to add anything?

[Todd Carter, executive]

I agree with everything you said, Al. The other thing to mention, there is a question about additional data from UCB, and I think it will be important for us to see what additional data come out on some of the PK and PD, that PK/PD relationship. As Al has pointed out, the relationship between reduction of tau accumulation and potential cognitive benefit that it appears is pretty interesting, and we see that as very encouraging. Those are in some groups. I think seeing more detail about target engagement in that relationship will really be important to interpret the results.

[Alfred Sandrock, executive]

Go ahead, Jay.

[Jay Olson, analyst]

Great. And then maybe just as a follow-on, how are you thinking about prioritizing VY7523 versus your tau silencing gene therapy and then the potential for combining either of your anti-tau approaches with anti-amyloid antibodies?

[Alfred Sandrock, executive]

Well, I would say that they're both high priorities. Am I allowed to say that 2 things are both high priorities?

[Jay Olson, analyst]

Yes.

[Alfred Sandrock, executive]

Look, we've always said that tau is a very important target, that we think it's the next step in helping Alzheimer's patients that the anti-amyloid treatments got us started, but we need to do better for patients. And so I think they're both high priorities. They're very different approaches in many ways. And so we'll find out which is the better approach. In terms of combining with the anti-amyloid antibodies, I do think that there could be a place for combining. I would say that it would be in those patients that seem to have a partial response to the anti-amyloid antibodies.

They have no response to the anti-amyloid antibodies. There's no sense in continuing the drug. If they've had a full response to anti-amyloid antibodies, which may be the case in some patients. If you're not progressing at all in your disease on anti-amyloid antibodies, there'd be no reason to add anything else. So I think time will help us -- time will tell what the heterogeneity of the treatment response is to the anti-amyloid antibody therapies in humans as we see the drugs being rolled out. And then by the time we're ready to think about that combination approach, I think we'll have more data on how many patients respond fully, how many respond not at all, and how many respond partially. And -- but I would say that we would want data initially as monotherapy too, first to see that -- make sure that our drug is active, and then have some understanding of the doses that we would want to use.

[Operator]

Our next question comes from Lili Nsongo at Leerink.

[Lili Nsongo, analyst]

I guess 2 questions for me. So the first one, as we await for inpatient data in 2026 for the tau-targeted antibodies, are there any plans to potentially test previously developed C-terminal antibodies in preclinical models to try to further confirm the negative predictive values of the model you use in a more region-specific approach?

[Alfred Sandrock, executive]

Well, if we -- if there's another antibody that's negative, I think that would be a pretty interesting study to do, particularly if it's not N-terminal, right? So I'm not sure doing any more N-terminal-directed antibodies would add much, but if there's an antibody targeting a different epitope that fails, then it might be interesting to do that experiment that you're proposing, Lili.

[Lili Nsongo, analyst]

Yes. Because it was my understanding that both Hoffmann-La Roche and then Lundbeck has some C-terminal antibody, I think it could be really interesting preclinical data as we await. And I guess maybe segue into my second question. So regarding the UCB data and the challenges that they've had in the overall population, would that compel you to potentially start the development in patient in maybe a smaller, more targeted patient population? So I guess my question is, does the results of the study compel you to maybe have more stringent inclusion criteria in the initial inpatient study for the antibody?

[Alfred Sandrock, executive]

Yes. Lili, this is Al, and I'll start and I'll ask Toby to add his comments, but I would say that we would be very open to that idea. We would like to see if we can differentiate from bepranemab, if at all possible. And it could be that the choice of patient population could be a way to boost the efficacy that we see particularly on the clinical outcome measures, right, and get more clarity. We -- as Toby noted in his comments, there were subgroups, particularly those that were prespecified, I think it was the APOE4 non-carrier low tau burden patients who seem to do better. And those were exactly the patients where the effect on tau accumulation was more pronounced. So I'd be open to that. Even though it's a smaller population, we're talking about a gigantic population overall, the Alzheimer's disease patients and to have a targeted treatment for smaller population is still quite large, by the way, is -- would be of interest. Toby?

[Toby Ferguson, executive]

So, Al, you captured it nicely. I think the only other comment I'd make is that when we did look at the bepranemab data, they had segregated their low and high tau populations. There really weren't that many low tau patients in the study overall, about a 80-20 ratio approximately. And so I think more data there, that is suggestive data, but we want to see sort of the breakdown of those data.

[Lili Nsongo, analyst]

And maybe just a follow-up. So we will be waiting for initial safety and PK data in healthy volunteers in the first half of 2025, but I was wondering maybe if you could give a little more granularity in terms of when we should expect an update on the potential design of the inpatient study.

[Alfred Sandrock, executive]

I think she's interested in the design of the multiple ascending dose study.

[Lili Nsongo, analyst]

Yes, absolutely.

[Toby Ferguson, executive]

Thanks, Lili. So I think as we -- once we get closer to the start, which -- start next year, we'll share the details of the design.

[Operator]

Our next question comes from Patrick Trucchio at H.C. Wainwright & Co.

[Patrick Trucchio, analyst]

Just a couple of questions from me. The first is just a follow-up on earlier comment regarding the appropriate patient population for the tau program -- for the antibody program. Can you discuss what level of tau PET burden do you think could be appropriate based on this learnings from this recent data, and particularly as we approach that Phase Ib trial with VY7523? And then separately, as we think about or as we look ahead to the tau silencing gene therapy, I'm wondering if you can talk about the advantages or differences we should expect from the tau silencing gene therapy as compared to these tau-targeting antibodies. And then secondly, what remains to be completed to ensure that the 2026 IND and CTA filings remain on track for the tau silencing gene therapy? And then lastly, if you could, just talk about the anticipated capsid and advantages of the Voyager platform as compared to some of these others in the field developing a similar approach?

[Alfred Sandrock, executive]

That's a lot of questions, Patrick, but we'll knock them off one by one here. So I'll take the first one and then maybe Toby can take the second and, Todd, you can take the third one. But anyway, on the appropriate patients, the cutoff that UCB shared data with us was a prespecified cutoff, but it was not the median. In fact, there were many fewer patients, I think, in the low tau burden subgroup versus the high tau. I think that was because it was prespecified. Hopefully, we'll see more data on the full range of tau burden and to understand better what the cutoff needs to be. And so right now, I mean, all we have is that one piece of data to go on. I think we would need more to be more specific about the tau burden. Toby, you can let me know if you disagree with that.

[Toby Ferguson, executive]

I do not, Al.

[Alfred Sandrock, executive]

Okay. And then on the tau [ KD ], I think you were asking how do we make sure that we stay, like are we on track. And so maybe, Toby and Todd, do you want to help me with those questions?

[Toby Ferguson, executive]

Sure. Maybe I'll start and ask Todd to fill in. So the preclinical development is proceeding. I think the key next steps are sort of moving the molecule forward. And then, of course, I think the pivotal step we'll do in the toxicology studies.

[Todd Carter, executive]

All right. The standard IND-enabling studies would be part of the process. You also asked about differentiation for the tau knockdown versus the antibody approach, I believe. And I think the BIIB080 data, which is an ASO delivered, that has shown some really interesting clinical data to date versus the antibody approaches. But what was seen in the BIIB080 data are not only signs that you could reduce the accumulation of tau, but you may be able to reduce tau burden, pathological tau burden, as measured by PET, in some cases below starting burden, which is a pretty remarkable finding. When you look at those sorts of data, and even with the recent bepranemab data that also seem to suggest that an impact on tau PET imaging results can impact clinically.

I think there, there is accumulating evidence in the field that impacting tau accumulation can have a clinical benefit with the gene therapy approach, of course. Here, we're talking about a once-and-done approach. We can dose once. We know that our vectors, and this gets into a little bit of the Voyager platform question as well, that our capsids can deliver quite broadly throughout the CNS. We can get delivery not only to the, I'll call it the shallower regions of the brain, but also the deeper structures with that single dose. And so we think there could be some substantial benefits for a tau knockdown approach. It is also an intracellular effect.

The antibody has an impact presumably based on the prion spreading hypothesis as the pathological tau spreads from cell to cell. So an intracellular reduction of tau could have an impact not only in reducing that cell to cell spread, but also in an intracellular way. So those 2 approaches I think are both interesting. There are signs of -- for both those mechanisms that they could work. And in the end, it's even possible there could be combination approaches.

[Alfred Sandrock, executive]

So, Toby, do you want to add on potential clinical outcomes?

[Toby Ferguson, executive]

So there, I think the BIIB080 data in particular really emphasized, along with the recent bepranemab data, the importance of tau PET. And to Todd's prior point, in the BIIB080 knockdown-based approach or a knockdown-based approach, you can see the removal of both preexisting pathological tau and prevention of further accumulation and -- in somewhat earlier time frame, 6 months or so, which is distinct from slowing accumulation. This is particular to the tau knockdown approach. In addition, you can also see clear signals in the CSF biomarkers, total tau, for example, and other tau species. And so there is a chance based on biomarkers to get a relative quick read on how the molecule is performing.

[Alfred Sandrock, executive]

And what about the -- do you think the effect size, I mean, it's hard, right?

[Toby Ferguson, executive]

It's early data. The -- I mean, if you look at the [ propensity ] score matching that Biogen performed, they looked at a comparison to another study called TANGO, they looked at a natural history study, and there that effect size was 2 points to 2.5 points on CDR sum of boxes. As a reminder, the effects on the amyloid therapies were 0.4 points to 0.9 points approximately on CDR sum of boxes. So potentially larger effect size as well, which gives you an additional opportunity to potentially see clinical signal with smaller sample size.

[Operator]

I'm showing no further questions at this time. I would now like to turn it back to Al for closing remarks.

[Alfred Sandrock, executive]

Thank you everyone for joining us today, and we look forward to speaking with you again soon.

[Operator]

Thank you for your participation in today's conference. This does conclude the program. You may now disconnect.