Good day and welcome to the Acumen Pharmaceuticals third quarter 2026 conference call and webcast. At this time, all participants are in a listen-only mode. After the speaker's presentation, there will be a question and answer session. To ask a question, you will need to press star 1-1 on your touchtone telephone. Please note this call may be recorded. I would like to turn the call over to Alex Braun, head of investor relations. Please go ahead.

Thanks, Michelle. Good morning and welcome to the Acumen conference call to discuss our business update and financial results for the quarter ended September 30th, 2026. With me today are Daniel O'Connell, our Chief Executive Officer, and Matt Zuga, our CFO and Chief Business Officer. They'll have brief prepared remarks, and then we'll open the call for questions. Before we begin, we encourage listeners to go to the Investor section of the Acumen website to find our press release issued this morning that we'll discuss today. Please note that during today's conference call, we may make forward-looking statements within the meaning of the federal securities laws, including statements concerning our financial outlook and expected business plans. Please see slide 2 of our corporate presentation, our press release issued this morning, and our most recent annual and quarterly reports filed with the SEC for important risk factors that could cause their actual results to differ materially from those expressed or implied in the forward-looking statements. We undertake no obligation to update or revise the information provided on this call or in the accompanying presentation as a result of new information or future results or developments. So with that, I'll turn the call over to Dan.

Great. Thanks, Alex. Good morning, everyone, and thanks for joining us today. In the third quarter, our team has been very busy readying for the top line readout from our phase two Altitude AD trial, investigating our lead product candidate, Sobernitog. If you've been following our company for some time, you're likely well aware that these results are highly anticipated. We are testing our central scientific thesis, that arresting the harm done by synaptotoxic amyloid beta-oligomers in the brain may offer a differentiated approach to treating Alzheimer's disease. So today, I'm pleased to confirm that we expect to announce these Phase II results this November. We are confident that we are fully evaluating the A-beta-oligomer hypothesis with this study. AltitudeAD is a large, well-powered Phase II trial with clinically meaningful endpoints. We are testing two doses of Subirnatug against placebo, carefully considered based on our Phase 1 study in Alzheimer's patients, such that either dose may prove efficacious in the Phase 2. We have executed the study to a very high operational standard with rapid enrollment, close engagement with study sites and investigators, and high rollover into the open-label extension of the study. As previously mentioned, we envision this study as part of a potential registration package and have conducted the study as such, with a single confirmatory Phase III anticipated following positive Phase II results. As previously outlined, AltitudeAD was designed to detect a statistically significant difference between suburnatug and placebo on the primary efficacy endpoint, Idris, following 18 months of treatment. We expect the top-line dataset to encompass primary endpoint results, key secondary outcomes including the CDR sum of boxes, Safety Evaluations Covering Adverse Events and ARIA Rates, and a range of informative fluid and imaging biomarkers. We believe that Suburnatug has the potential to demonstrate a differentiated benefit-to-risk profile given its unique product attributes as a selective anti-A-beta-oligomer IgG2 monoclonal. We look forward to sharing the data in November. We also continue to advance our Enhanced Brain Delivery Program, or EBD, for the treatment of Alzheimer's disease. representing the only program combining a validated blood-brain barrier-penetrating technology with an A-beta-oligomer-selective therapeutic antibody. As a reminder, we are working on two candidates in the lead-up to an IND filing expected in mid-2027. One candidate, ACU301, is based on a bispecific antibody incorporating suburnatone, and ACU401 incorporates a novel A-beta-selective antibody with differentiated properties known as ACU234. We presented encouraging data at the AAIC meeting in July showing that after intravenous dosing, all tested EBD bispecific antibodies achieved multi-fold greater brain exposure than unmodified ACU234 alone. ACU401 in particular achieved up to a 40-fold greater frontal cortex exposure in non-human primates and significant increase in exposures in deep brain regions. The degree of brain penetration we observed in the cinnamolus monkeys combined with the preserved soluble A-beta-oligomer selectivity and a clean hematological profile exceeded our expectations and give us confidence in the differentiated potential of our EBD program. The imminent data readout for Subbernative and the development of our next generation EBD candidates demonstrate both the robustness of our pipeline and our ability to deliver on key priorities positioning us for an important period of value-creating milestones ahead, both near and longer term. Again, we look forward to updating you in November. And with that, I'll turn the call over to Matt.

Thanks, Dan. As a reminder, our third quarter 2026 financial results are available in the press release we issued this morning and in our 10Q we will file later today. We ended the third quarter with approximately $79 million in cash and marketable securities on our balance sheet, which is expected to support our current clinical and operational activities into early 2027. R&D expenses were $21.1 million in the third quarter. The decrease over the prior year was primarily due to reductions in manufacturing and materials costs, as well as CRO costs, which are both associated with our Altitude AD clinical trial. DNA expenses were $4.7 million in the third quarter, roughly flat to the same period in the prior year. This led to a loss from operations of $25.8 million and a net loss of $25.4 million in the third quarter. We look forward to reporting on our Phase II Altitude AD study next month and remain committed to maximizing the potential of our portfolio of A-Beta Oligomer Targeted Antibodies to Generate Value for Patients Living with Alzheimer's Disease, Their Caregivers, and Our Stakeholders. And with that, we can open the call for Q&A. Operator?

Thank you. As a reminder, to ask a question, please press star 1-1. If your question has been answered and you'd like to remove yourself from the queue, press star 1-1 again. Our first question comes from Jason Zemanski. with Bank of America. Your line is open.

Good morning. Congratulations on the progress. Looking forward to the results. This may seem like a random question now, but as we think about the evolving treatment paradigm, it looks like Biogen is now positioning Lequembi as a follow-on after Denenumab clears plaque. And the argument is that soluble species sort of keep driving disease after the plaque is gone. So it seems like a natural place for and Oligomer Selective Antibody. How do you think about Subirnatug in addition to sort of a primary role but as a maintenance after plaque clearance or in combination with a plaque clear and could anything in the altitude data set inform that? Thanks so much.

Thanks, Jason. Great question. So we've always been advocates for chronic dosing essentially while patients are stable within an early AD stage of disease. as we believe these soluble aggregates are present and persistent in driving disease pathology. So it would be a logical extension to consider Subirnatug or an oligomer-selected antibody as a post-plat clearance follow-on. So in the primary mode, we're focused on the primary outcome for Subirnatug in altitude with an 18-month primary using the IGRAS. So I think we'll have the first case evidences really out of that Phase II moving towards Phase III, but the therapeutic rationale for Subirnatug as a follow-on would make sense to us as we sit here today.

Great. Thanks so much for the color.

Thank you. Our next question comes from Paul Matisse with Stifel. Your line is open.

Hi. This is Emily on for Paul. We were just wondering if you could talk a little bit about your dose selection and What might you expect to see in this upcoming readout that would look different on efficacy and safety between those two doses? Thank you.

Thanks, Emily. Yeah, so for the phase two, we chose doses of 35 mg per kg and 50 mg per kg, and this is IV dosing every four weeks. So we arrived at those doses as a consequence of the dose exposure and some of the pharmacodynamic effects we observed in the phase one. So a combination of The Phase 1 results with some dose modeling allowed us to select these two doses. And importantly, we think both 35 and 50 each are within the zone that could be efficacious. It may be that the higher dose of 50 mg per kg may have perhaps more observed effects on the amyloid PET signal, but we will see how that leads out in the weeks ahead. We're getting close to that data set, so very excited to see it. But important to establish that both of these doses we think are within that zone of efficacy in conjunction with the safety profile that we think could offer a benefit to risk profile that's attractive to patients.

Thank you. Our next question comes from Pete Stavropoulos with Cantor Fitzgerald. Your line is open.

Good morning and congrats on the execution. Looking forward to the data next month and thanks for taking our questions. A couple for me. I'm wondering what your current thinking is in terms of the bar or what is the minimum we'd like to sort of see out of altitude to move forward, especially since this is the first time that the oligomer hypothesis is being tested. So the bar for both clinical scales and biomarker data and what would we expect any OLE data in the readout?

Thanks, Pete. So as you may recall, we've been guiding towards a clear clinical success of 30% slowing on the Ivers after 18 months of a placebo control period. We think that's a zone in which that would give us the basis for moving forward. And in terms of the safety profile, I mean, the overall adverse event profile, inclusive of ARIA rates and infusion site reactions and other elements of the safety profile, is going to be a part of this top line readout. We would anticipate low double-digit REE in fatality and maybe consistent across the genotypes as part of the support of the oligomer hypothesis and the grounds of which Subrata would be moving forward to Phase III. So that's kind of how we're thinking about that. So your second question, Pete? OLE data. So, yeah, as you are good to point out, our open label extension is a 12-month open label extension. We've had high rollover, essentially greater than 95% of people eligible to participate in the open label extension have elected and consented to do so. That portion of the study we'll be reading out over an extended period of time. We do think that that will generate evidence into 2027 and likely won't be part of the top line results. I think important to establish, however, the top line results, as I just mentioned on the scripted call, will be inclusive of the primary and secondary, both efficacy and safety, and include biomarker effects, both imaging and fluid. In terms of the, you know, we'll be looking at the amyloid PET as a conventional imaging measure. We'll also be looking at fluid biomarkers CSF, and Plasma. I think we'll principally be looking at things such as the PETA 217 as a measure of disease status, potentially progression. And I think that's going to be a complete data set to inform, you know, stakeholders on the merits of Subirnatug and provide evidence in support of the oligomer hypothesis.

All right. Thank you for that. And just a question on EVD. How are you thinking about the path forward for 301 or 401? You know, the MADSAT studies, you know, are you going to go straight into patients or healthy volunteers first? And the length of time you sort of aim to have patients in the MADSAT study. And what optionality do these candidates offer?

Yeah, thanks, Pete. Well, yeah, so we think there's a lot of optionality in our EBD program. I think having both 301 and 401 in the mix is really helpful because it affords us a bit of diversity in terms of the profiles and ways to move the program forward. I think we've learned so much in the development of Suburnatug, both initially with Intercept, which was our phase one study exclusively in Alzheimer's patients that gave us really solid phase one proof of mechanism data in support of Suburnatug. And of course, as I just mentioned, informed dosing strategy and the plan for phase two. I think the team's still working on refining precisely what we want to do with EBD in the early phase and translational studies. and we'll be looking at the altitude results in particular to assess, you know, dosing strategy as well as biomarker strategy for the EBD program. So, we think, you know, one of the advantages we at Acumen have is all of the experience we've, you know, we've undertaken with Subirnatog not only through phase one but through a robust phase two that really serves as a foundation for our strategy for developing the EBD candidates.

All right. Thank you very much and congrats on the progress once again.

Thanks, Pete.

Thank you. Our next question comes from Tom Schrader with BTIG. Your line is open.

Good morning. I guess we'll all hold our breath for 30 days. I think one of the interesting things about Subirnatug is that it might act faster given the monomer binding, things like that. And the question is, how set up are you to capture that? When are you looking at patients? When are you scanning? When are you taking soluble biomarkers? I think a fantastic readout from this might be that your next phase three could be shorter because the drug works faster. And the question is, how set up are you to catch some sort of readout like that? Thank you. Thanks, Tom. Good morning. So, with Suburnatug's high selectivity for toxic A-beta ligamers, the thesis holds that neutralizing those toxic species and many more. to look at earlier time points for establishing a drug effect going forward. So, yeah, it's a really, as you mentioned, we think altitude is a robust test of this central scientific hypothesis and are eagerly awaiting the unblinding and interpretation of those results. Okay, fantastic. Good luck again. Thanks, Tom.

Thank you. Our next question comes from Jeff Meacham with Citi. Your line is open.

Good morning. This is Mary Keaton for Jeff. Thanks for taking our question. Could you speak to some of the KOL feedback you're receiving on Subirnatug and the Altitude AD program? Maybe what are physicians looking for in a treatment and how could Subirnatug address these needs? And then just as another one, maybe what feedback do they have on the mechanism here as well? Thank you.

Great, so in our travels and interactions with KOLs, I mean, they're mostly principally focused on better treatment options for patients. And I think as such, Suburnatum with a different mechanism, not a plaque busting agent, but rather something that targets these soluble toxic species is something of high interest and given that potential. So they are keenly, as is everybody in the field, I think kind of looking at altitude as a differentiated study where Subirnatug could shift some people's thinking on what the primary mode of treatment should be, whether it be oligomers versus plaque and so forth. So we think there's a lot of anticipation going into next month's readout, and we do think that the study has a mix of data outcomes and readouts. that will be very informative as to the merits of Suburnatug and underpin the attractiveness of targeting toxic oligomers in a primary, selective, and direct fashion.

Great. Thank you.

Thank you. Our next question comes from Dev Prasad with Lucid Capital Markets. Your line is open.

Hi, congrats on the progress and thank you for taking our question. A couple of questions. One is, as we approach the readout, can you comment on patient retention and maybe how should we think of the impact of missing data or discontinuation on primary efficacy analysis? And another one is on subcutaneous. I believe the subcu work was on hold until the dosage was chosen. So I'm wondering, do you plan to initiate that work after the phase two trial? Thank you.

Thanks, Deb. So in terms of retention and the primary altitude AD study, as we mentioned, we've conducted the study to a very high standard. We have our retention within the primary portion of the study has exceeded sort of our expectations, which is great. And we've had high rollover into the open label extension. Just objectively, we think people that are participating in the study like the study and have been inclined to stay in and or extend their involvement in the study. So that's encouraging, and yet it's obviously still blind to data. In respect to your question of missing data, I think we will be addressing those issues in a kind of conventional and per protocol basis. So I don't know that there's more I can offer, more specifics I can offer on that question. and thirdly, in terms of the sub-Q, yes, we completed a healthy volunteer, essentially a bioavailability study that read out in early 25. We think we have what we need in terms of the contrast between IV dosing and subcutaneous dosing of the subvertotype formulation. We anticipate using the phase three in one direction or another to incorporate a subcutaneous and I think we can look at some predicates out there if you look at what ASI and Biogen did with Lekembe, excuse me, incorporating sub-Q as part of the open-label extension in phase three, you know, that could be analogous to how we would be moving forward in the future with a subcutaneous option.

Great. Thank you.

Thank you. This concludes the question and answer session. Thank you for your participation. You may now disconnect. Good day.