Prothena Corp Public Ltd Co Q4 FY2025 Earnings Call

Good day, everyone, and welcome to the Prothena Biosciences Fourth Quarter and Full Year 2025 Financial Results Conference Call. My name is Jeannie, and I will be your coordinator today. I would now like to turn the presentation over to Mark Johnson, Vice President and Head of Investor Relations at Prothena. Please go ahead.

Thank you, operator. Good afternoon, everyone, and welcome to today's call to review Prothena's business progress, fourth quarter and full year 2025 financial results, and 2026 financial guidance. Please review the press release we issued earlier today, which is available on our website at prothena.com and is also attached to a Form 8-K filed today with the SEC. In addition, we are using supplemental slides, which are available on our Investors website, Events & Presentations section. On today's call, Dr. Gene Kinney, our President and Executive Officer, will provide opening remarks, including an overview on Prothena's corporate strategy. Chad Swanson, our Chief Development Officer, will provide an update on our ongoing partnered clinical programs. Then Phil Dolan, our Vice President and Head of Discovery Research, will provide an update on our active preclinical programs. Tran Nguyen, our Chief Strategy Officer and Chief Financial Officer, will then discuss our 2025 financial results and 2026 financial guidance before turning it back to Gene for closing remarks, at which point, we will open up the call for a Q&A session. Brandon Smith, our Chief Operating Officer, will also be available during the Q&A session. Before we begin, I would like to remind you that during today's presentation, we will be making forward-looking statements that are subject to certain risks, uncertainties, and other factors that could cause actual results to differ materially from those referred to in any of the forward-looking statements. For a discussion of these risks and uncertainties associated with our forward-looking statements, please see our press release issued today as well as our most recent filings with the SEC and our annual report on Form 10-K to be filed with the SEC for our fiscal year 2025. We disclaim any obligation to update our forward-looking statements. With that, I'd like to turn the call over to Gene.

Thank you, Mark, and thank you all for joining us today. Let's begin on Slide 5. In 2025, we saw significant progress with our clinical pipeline where 2 of our partner programs, prasinezumab and coramitug, advanced into Phase III clinical trials. Roche advanced prasinezumab into the Phase III PARAISO trial, evaluating 900 participants with early Parkinson's disease. This decision was informed by results from 2 Phase II clinical trials that both demonstrated consistent slowing of disease progression. Novo Nordisk advanced coramitug into the Phase III CLEOPATTRA trial, evaluating 1,280 patients with amyloid transthyretin cardiomyopathy or ATTR-CM. This decision was informed by results from their Phase II trial demonstrating positive NT-proBNP and echocardiogram changes as well as directional observation of benefit in the 6-minute walk test. Our collaborations with Bristol Myers Squibb also progressed in 2025 with several important advancements, including the Phase II TargetTau-1 clinical trial, evaluating BMS-986446 in early Alzheimer's disease, which was fully enrolled in 2025 with completion expected in the first half of 2027. Bristol Myers Squibb also completed a Phase I study evaluating a subcutaneous formulation of BMS-986446 in 2025. And BMS-986446 obtained Fast Track designation from the U.S. FDA for the treatment of Alzheimer's disease. And finally, we are conducting a Phase I trial for PRX019, which is on track for completion in 2026. We also shared important updates from our wholly owned preclinical portfolio in 2025. In the fourth quarter, we introduced our CYTOPE technology with presentations of our TDP-43 CYTOPE program for ALS at 2 scientific congresses. At a high level, these data demonstrated that our CYTOPE technology has the potential to enable precise targeting of intracellular disease pathways. We also reported results from our Phase I ASCENT clinical program evaluating PRX012 in patients with early Alzheimer's disease. The results help to elucidate the profile of this once-monthly subcutaneous anti-A beta antibody. Based on significant scientific advances over the last several years, we believe we can further improve this profile with the addition of transferrin receptor technology and are actively advancing a PRX012 transferrin program in preclinical development. Turning to Slide 6, we have several key 2026 priorities that we believe meaningfully contribute to long-term value creation. The first is to ensure we are best positioned to capture value embedded in our clinical partnerships. As a reminder, all of our partnerships with large pharma companies are programs that originated from Prothena's R&D engine. This year, we have the potential to earn up to $105 million in aggregate clinical milestone payments if coramitug achieves a prespecified enrollment target in its ongoing Phase III trial and if BMS decides to advance PRX019 into Phase II clinical development. In addition, we have now received all the necessary approvals from our extraordinary General Meeting of Shareholders, and confirmed by the Irish High Court to support a share redemption program in 2026. Finally, we continue to advance our knowledge and understanding of our preclinical portfolio to support our business development team as they explore research collaborations and licensing agreements. For example, we are engaged in a research collaboration with a large pharmaceutical company that explores multiple approaches for applying our CYTOPE technology to advance and elucidate intracellular targeting. We look forward to establishing additional research collaborations, which may lead to future licensing deals. Our strategic priorities are supported by our $308.4 million cash and restricted cash balance as of year-end 2025 and our prudent capital utilization to ensure that we are well positioned to receive future potential economics from our partner programs. Let's move to Slide 7 to review our upcoming catalysts from our partner portfolio. Looking ahead, we have 2 potential milestones in 2026 from coramitug and PRX019, which could be worth up to $105 million. In the first half of 2027, we expect Bristol Myers Squibb to complete their Phase II TargetTau-1 trial for BMS-986446. And in 2029, we expect primary completions from the 2 Phase III trials evaluating Roche's prasinezumab and Novo Nordisk coramitug. In total, when you look at our 4 partner clinical programs, they have the potential in aggregate to deliver up to approximately $3 billion in future milestone payments, which is in addition to any royalties. With that, I'll now turn the call over to Chad to discuss our partner programs in more detail.

Thanks, Gene. Let's start on Slide 9. Prasinezumab is a humanized IgG1 monoclonal antibody designed to selectively bind aggregated forms of alpha-synuclein to reduce neurotoxicity and slow disease progression of Parkinson's disease by blocking further accumulation and propagation of these toxic aggregates. Based on the consistent results from 2 Phase II clinical trials, PADOVA and PASADENA and our open-label extensions, our partner, Roche, made the decision to advance prasinezumab to Phase III, bringing this potential first disease-modifying therapy one step closer to patients. In fact, Roche made this decision based on a number of important questions. First, is there an unmet need? Yes, there are over 10 million patients globally, and it is the fastest-growing neurodegenerative disease with no approved disease-modifying therapies to slow progression. Second, does it address the foundational target? Yes, alpha-synuclein is a known biological driver of PD progression and the clinical evidence to date demonstrates efficacy potential and supports a favorable safety and tolerability profile. Third, is there a meaningful therapeutic differentiation? Yes. The totality of data suggests clear evidence of delayed motor progression even on top of the standard symptomatic treatment levodopa. And finally, is there a strong commercial rationale? Yes, Roche believes prasinezumab represents a global peak sales opportunity greater than $3.5 billion. For Prothena, our deal includes up to $620 million in potential future milestone payments and sales royalties tiered to high-teen percentages. In the fourth quarter of 2025, Roche initiated the Phase III PARAISO clinical trial, which will enroll approximately 900 participants with early Parkinson's disease with primary completion expected in 2029. Moving on to Slide 10, this is an important data set from the Phase IIb PADOVA trial, which Roche presented at ADPD 2025. Here, they show progression on the MDS-UPDRS Part III scale from baseline, which is used to measure disease progression on motor symptoms. This figure shows the results for an exploratory endpoint looking at the subset of participants, approximately 75% of the trial population were on stable levodopa treatment comparing 24 months of prasinezumab treatment versus placebo. What we see is a 40% relative reduction in progression with a nominal p-value of 0.0177 on this exploratory endpoint. These were very important results as they were used to further optimize aspects of the Phase III PARAISO trial design. On Slide 11, let's review key aspects of the Phase III protocol that were optimized to increase the relative probability of successful outcome. First, increased patient population. The Phase III trial is evaluating 900 patients, whereas the Phase IIb PADOVA trial enrolled 586 patients. Second, all patients in the Phase III trial are required to be on stable symptomatic treatment with levodopa. In the prior Phase IIb PADOVA trial, the approximately 75% of patients on levodopa treatment were nominally statistically significant on the primary outcome and exploratory endpoint shown on the previous slide. Third, the duration of the Phase III trial is a minimum of 24 months versus 18 months in the prior Phase IIb PADOVA trial. In the PADOVA trial, the patients who are on treatment for at least 24 months had greater separation from placebo on the exploratory endpoint shown on the previous slide. We believe Roche will continue to communicate clinical results from its completed Phase II trials and ongoing open-label extensions at upcoming medical conferences. We look forward to the primary completion of the Phase III PARAISO trial expected in 2029. Moving to coramitug on Slide 12, potential first-in-class amyloid depleter antibody for the treatment of ATTR cardiomyopathy being developed by Novo Nordisk. ATTR-CM is a rare, progressive and potentially fatal disease characterized by deposition of abnormal non-native forms of transthyretin amyloid in vital organs. Coramitug is thought to deplete both the positive amyloid and circulating non-native TTR to prevent further deposition and to improve organ function. This mechanism of action has the potential to provide benefit for all ATTR-CM patients, even those patients currently receiving treatment with a stabilizer or silencer. Novo Nordisk completed its Phase II clinical trial evaluating coramitug in ATTR-CM in 2025 and presented those positive results in a late-breaking session at the American Heart Association's 2025 Scientific Session with a simultaneous publication in the journal circulation. The results demonstrated reductions in NT-proBNP and echocardiogram improvement suggested of cardiac remodeling, all with a favorable safety profile. It's important to note that these results were demonstrated on top of standard of care with over 80% of patients across coramitug and placebo controlled arms receiving concomitant TTR stabilizers. Based on these results, Novo Nordisk initiated a Phase III CLEOPATTRA trial, which is intended to enroll approximately 1,280 ATTR-CM patients, primary completion expected in 2029. Based on peak sales estimates for the currently approved ATTR-CM drug, we believe that coramitug represents a multibillion-dollar market opportunity, allowing Prothena to potentially capture future milestone payments of up to an additional $1.13 billion. Let's review the Phase II results on Slide 13. This was a 12-month 105-patient Phase II trial randomized to placebo, 10 milligram per kilogram coramitug or 60 mg per kg coramitug. The co-primary endpoints were change from baseline versus placebo and NT-proBNP in the 6-minute walk test. The 60 mg per kg dose of coramitug resulted in a statistically significant reduction in NT-proBNP versus placebo with a 48% difference and a p-value equal to 0.0017. In addition, coramitug actually reduced NT-proBNP below baseline values in the 60-milligram per kilogram group. For the 6-minute walk test, the 60 mg per kg coramitug group demonstrated an encouraging numerical improvement but was not statistically significant, likely due to small sample size and short study duration. Additional analyses included a wide range of echocardiogram parameters, including measure of left and right ventricular systolic function, diastolic function and estimated pulmonary arterial pressures. Across these measures, coramitug at 60 mg per kg was associated with improvement compared to placebo suggested of cardiac remodeling. These results were the basis for advancing coramitug Phase III. As we see in Slide 14, the Phase III CLEOPATTRA trial is anticipated to enroll approximately 1,280 ATTR-CM patients randomized 1:1 to coramitug plus standard of care, placebo plus standard of care. The trial is available to New York Heart Association Class 1 through 4 patients with some additional inclusion/exclusion criteria. The primary endpoint is a composite endpoint of either the number of cardiovascular deaths or recurrent cardiovascular events such as hospitalization or an urgent heart failure visit. We look forward to the primary completion of the Phase III CLEOPATTRA trial expected in 2029. Moving on. Let's now discuss BMS-986446 on Slide 15. This is our potential first-in-class anti-tau antibody being developed by Bristol Myers Squibb. BMS-986446 was specifically designed to target key epitope within the microtubule binding region or MTBR of tau, a protein implicated in the causal pathophysiology of Alzheimer's. Tau tangles along with amyloid beta plaques are core hallmarks of Alzheimer's pathology and tau is strongly linked to clinical and cognitive decline. To date, BMS-986446 has completed its Phase I MAD in sales as well as an open-label single-dose trial to assess the subcutaneous formulation. In addition, BMS-986446 was granted Fast Track designation by the U.S. FDA for the treatment of Alzheimer's disease. Bristol Myers Squibb completed enrollment in the ongoing Phase II TargetTau-1 clinical trial in approximately 310 patients with early Alzheimer's in 2025, and we expect study completion in the first half of 2027. Alzheimer's disease represents a multibillion-dollar market opportunity. And in our partnership with BMS, we have the potential to earn up to an additional $562.5 million in future milestones as well as tiered sales royalties up to high teens percentages on a weighted average basis. Slide 16 illustrates the various areas where antibodies have been developed to target tau. Tau is a large protein comprised of approximately 440 amino acids in some forms with multiple phosphorylation sites, truncation sites and multiple splice variants. One of the long-standing challenges in the field has been how to best target the tau protein in order to provide functional benefit in the context of disease. We took an approach called empirical epitope mapping in order to identify an antibody that delivered consistent robust effects. This work led us to target the MTBR domain, which was the only area that satisfied our internal requirements. The field has since clarified that MTBR domain is central to fibropmation, feeding and cell-to-cell transmission of tau pathology. MTBR-tau-243 has been shown to be highly correlated tau-PET and disease progression. In preclinical studies, MTBR-targeting antibodies demonstrated blocking of internalization and spread of tau, leading to the reduction of tau pathology. Ongoing Phase II clinical trials, including the Phase II TargetTau-1 for our partner, BMS, are underway. A different anti-MTBR-tau antibody recently demonstrated positive trends on biomarkers, including MTBR-tau-243 and tau PET in a small number of patients. Slide 17 highlights the Phase II TargetTau-1 trial design, which enrolled approximately 310 patients with early Alzheimer's disease, randomized 433 and placebo low-dose BMS-986446 and high-dose BMS-986446, respectively. The primary endpoint is change from baseline in brain tau deposition as measured by tau PET at 76 weeks with secondary endpoints measuring functional and cognitive changes, including CDR sum of boxes and iADRS. We are excited to learn the results from this Phase II trial with primary completion expected in the first half of 2027. And finally, I'll briefly review PRX019 on Slide 18. For our agreement with Bristol Myers Squibb, we are conducting the Phase I trial, both single ascending and multiple doses evaluating safety, tolerability, immunogenicity, PK and pharmacodynamic effect. We expect to complete the trial in 2026 and are eligible for a potential milestone for BMS decide to further develop PRX019. In total, we have the potential to earn up to $617.5 million in future milestones, tiered sales royalties up to high teen percentages. With that, I'll now turn the call over to Phil Dolan to discuss our wholly-owned preclinical portfolio.

Thanks, Chad. Please turn to Slide 20 for an overview of our exciting new CYTOPE technology. Our CYTOPE is an innovative targeting technology invented by Prothena to reach virtually any cell type and enable precise targeting of intracellular disease pathways in the brain and periphery through an endosomal uptake and escape mechanism that preserves membrane and vesicle integrity following systemic administration. This technology potentially allows for targeting of previously undruggable intracellular disease targets. Each CYTOPE program is uniquely tailored to target a specific intracellular disease pathway. It is comprised of a cell internalizing technology, a targeting element derived from a macromolecule such as an antibody and may include optional elements such as the addition of receptor-mediated technology to enable delivery to specific cells or tissues. Our first disclosed program to utilize this technology is our TDP-43 CYTOPE amnoscorphic lateral sclerosis or ALS. Let's discuss further on Slide 21. ALS is a progressive fatal neurodegenerative disease characterized by the selective loss of upper and lower motor neurons and in the majority of cases by cytoplasmic aggregation and nuclear depletion of the RNA binding protein TDP-43. Current approved therapies used to treat ALS seek to affect disease progression by targeting broad mechanisms such as cytotoxicity and oxidative stress rather than the core molecular pathology. These treatments do not stop or reverse motor neuron degeneration and to date, provide limited clinical benefit. Consequently, there remains a major unmet need for disease-modifying therapies that directly address TDP-43-driven mechanism. Using our internally discovered CYTOPE technology, we have developed an anti-phosphorylated TDP-43 CYTOPE lateral that is designed to address the core molecular pathology associated with approximately 97% of ALS cases. This regulation of TDP-43 triggers both toxic gain of function and loss of function deficits in the context of disease. A key challenge in the field has been how to effectively target intracellular phosphorylated TDP-43 aggregates, which are broadly deposited in the CNS and periphery while preserving normal TDP-43 function. As shown in the slide, neither conventional antibodies, small molecules or oligonucleotides have all of the components needed to effectively target and eliminate intracellular phosphorylated TDP-43 aggregates. And our TDP-43 CYTOPE on Slide 22. TDP-43 CYTOPE was designed to specifically bind to and degrade intracellular phosphorylated TDP-43 aggregates that are central to ALS pathology. In preclinical studies, our unique TDP-43 cytope has been demonstrated to degrade phosphorylated TDP-43 associated aggregates located in the cytoplasm, addressing the toxic gain of function pathology. In addition, we have demonstrated that administration of our TDP-43 CYTOPE addresses the related loss of function biology potentially through restoration of TDP-43 trafficking and the function of normal TDP-43 in the nucleus. Importantly, the unmatched targeting specificity suggests that we may effectively reduce the pathogenic phosphorylated TDP-43 aggregates while preserving normal TDP-43 activity throughout the body. Moving to Slide 23, which highlights some of the key data presented at the Society for Neuroscience Congress in November of last year. On the left, we show supportive data on how TDP-43 CYTOPE addresses toxic gain of function by significantly reducing brain and muscle pathology in a highly aggressive ALS mouse model following systemic administration. These findings are particularly compelling given rapid persistent and aggressive accumulation of pathogenic aggregates in the rNLS8 transgenic mouse model of ALS. On the right, we show supportive data demonstrating that TDP-43 CYTOPE also addresses the loss of function biology. Here, TDP-43 CYTOPE attenuated RNA mis-splicing caused by cytoplasmic TDP-43 aggregation in both human neuronal cells and mice. This is exciting data from our TDP-43 CYTOPE program and supports the potential of our CYTOPE technology more broadly. We look forward to continuing to elucidate the potential of this program and the technology. Let's move to Slide 24 to provide an update on our PRX012 transferrin receptor preclinical program, or PRX012 TFR. Trontinemab is an anti-Abeta antibody developed from gantenerumab to also include transferin receptor binding technology. So far, reported data indicate the addition of transferrin targeting in trontinemab has resulted in improvements over gantenerumab, including significantly decreased the time required to achieve meaningful amyloid reduction and substantially lower risk of ARIA-E associated with amyloid targeting antibodies. Given the potential of our PRX012 antibody, which is based in part on our demonstration of the activity of this antibody in the clinical setting, we believe the combination of transferrin receptor binding technology could be very exciting. Let's move to Slide 25. Last year, we reported interim results from the PRX012 ASCENT Phase I clinical program, including a mean reduction in amyloid PET to approximately 27.5 centiloids at month 12 for patients who received a monthly subcutaneous dose of 400 milligrams of PRX012 from the start of the study. Preliminary results for patients reaching 18 months of treatment with the 400-milligram dose showed a mean reduction in amyloid PET to approximately 16 centiloids and 9 of the 12 patients achieved amyloid negativity defined as having a centiloids value less than 24.1. But as we reported in August, the ARIA-E rates for PRX012 were noncompetitive relative to FDA-approved anti-Abeta antibodies. Based on these collective results, we believe a PRX012-TfR approach is appropriate for further development. It is our desire to improve over PRX012 while maintaining a convenient once-monthly subcutaneous administration. Currently, we are exploring partnership interest for PRX012-TfR while advancing the program preclinically. With that, I'll turn it over to Tran to review our financial results.

Thanks, Phil. Please turn to Slide 27. Today, we reported financial results that were in line or favorable to our 2025 financial guidance. Please refer to our press release for a detailed breakdown of our financial results. In terms of our 2025 financial performance relative to guidance, we had net cash used in operating and investing activities of $163.7 million, which was favorable to our guidance range of $170 million to $178 million. Net loss was $244.1 million, which was in line with our guidance range of $240 million to $248. As of December 31, 2025, Prothena had $308.4 million in cash, cash equivalents and restricted cash, which was favorable to our guidance of $298 million. As of February 12, 2026, Prothena had 53.8 million ordinary shares outstanding. Additionally, we continue to have a simple capital structure with 0 debt. Turning to our 2026 financial guidance on Slide 28. We expect our full year 2026 net cash used in operating and investing activities to be between $50 million and $55 million. We expect to end the year with approximately $255 million in cash, cash equivalents, and restricted cash, which represents the midpoint of the range. The estimated full year 2026 net cash used in operating and investing activities is primarily driven by an estimated net loss of $67 million to $72 million, which includes an estimated $24 million of noncash share-based compensation expense. And as a reminder, our 2026 financial guidance does not include the up to $105 million of potential aggregate clinical milestone payments from strategic partners in 2026 related to the advancement of both coramitug or ATTR amyloidosis with cardiomyopathy by Novo Nordisk and PRX019 for neurodegenerative diseases by Bristol Myers Squibb. With that, I'll turn the call back to Gene for closing remarks.

Thank you, Tran. Moving to Slide 30. As we've shared today, we have a robust pipeline of programs that address significant unmet needs for potentially millions of patients, caregivers, and their families. It is our mission to continue to further develop our programs and elucidate the potential of our technology to address these needs. Let me end by recapping our 2026 strategic priorities, which are to capture the value embedded in our clinical partnerships, including up to $105 million in clinical milestones in 2026, to implement a share redemption program and invest in our preclinical portfolio to support our ongoing partnering efforts in the form of research collaborations, especially on our CYTOPE technology and drive future partnerships for our unpartnered programs. I'm proud of Prothena's execution and resilience in 2025, setting us up for an exciting future. We are well capitalized with a robust cash position and remain focused on delivering long-term shareholder value by delivering on our mission to patients. With that, we will now open the call to Q&A.

Your first question comes from the line of Yasmeen Rahimi with Piper Sandler.

This is Shannon on for Yas Rahimi. Congrats on the great progress, guys. We just wanted to know with the primary completion dates for the partnered program trials PARAISO and CLEOPATTRA not expected until 2029. Could you maybe walk us through some of the key milestones to look out for in 2026 and 2027 and what those milestones might be contingent on?

Yes. Thanks for the question, Shannon. So as we kind of laid out, we have a lot of things happening this year into next year and for the next several years. So I think as we look to some of our emerging technologies, some of the CYTOPE activities that we talked about on the call, we certainly expect to share more of that information this year through scientific presentations in particular, around our TDP-43 CYTOPE program and obviously, the progress we're making there. We talked about in 2027 in the first half of 2027, starting to see the data coming from our partner tau program with Bristol Myers Squibb. So we think that Phase II program would be very interesting as it was outlined by Chad on the call. Clearly, the primary outcome measure there is tau PET. So we think this is going to be a very interesting evaluation of our MTBR targeting tau approach. And then obviously, very much looking forward to the 2 Phase III readouts with primary expected completion dates in 2029, as you outlined, for both coramitug and prasinezumab. And clearly, as we indicated, not only do we think that those are well positioned based on the Phase II results, to be tested in an adequate way in the Phase III studies, but also represents the potential for significant medical advance in areas with pretty high unmet need and also, I think, very interesting economic opportunities with respect to the commercial opportunity there. But so yes, so I think it's actually going to be a very busy time for us. And the only other thing I would mention here, and maybe, Tran, if you want to speak to it further, as we look forward to instituting our share redemption program this year as well. So that's something that we needed to get approval for in an EGM, which took place at the end of last year, needed Irish High Court approval for that. And I think this year, we expect to implement that.

Yes, we'll make further announcements of that closer to the filing of our 10-K. But that also being said, to repeat that this year, we'll also have potentially up to $105 million worth of clinical milestones from our partners, which Gene covered in our prepared remarks from coramitug and PRX012. So exciting 2026 and beyond.

Your next question comes from the line of Michael DiFiore with Evercore ISI.

One on PRX012. If you could just elaborate how you try to keep the amyloid data story alive versus much larger, more advanced competitors. And as a relative follow-up, there are many transferrin receptor tech platforms out there. Maybe you could describe what the ideal transferrin receptor platform would offer that would make one stand apart.

Thank you for the question. You broke up a little, but I believe I understood most of it. To start, I'll ask Brandon to provide some insights on the business development aspect, but first, I want to address why we're enthusiastic about our PRX012 transferrin-based approach. There are two key aspects to these types of molecules. Much of our understanding in this area and the potential of integrating transferrin technology or receptor technology into anti-beta antibodies comes from the gantenerumab/trontinemab approach. We have gained a solid understanding of both the amyloid removal effectiveness and the ARIA-E rates associated with gantenerumab, and adding a transferrin-based approach with specific characteristics has proved beneficial. This is similar to Roche's strategy, and the results from trontinemab allow for direct comparison to gantenerumab. We have shared data for the parent molecule, PRX012, which shows promising results with a once-monthly subcutaneous administration, demonstrating significant amyloid removal. The majority of patients showed as amyloid negative, and the average centiloid value was notably low, indicating that we have a convenient and effective antibody for amyloid removal. However, we noted that the ARIA-E rates were somewhat less competitive. With this technology and by following the successful path observed with gantenerumab and trontinemab, we believe we can enhance the overall profile of PRX012 through our transferrin program. This is an exciting opportunity, and we anticipate quick progress, aiming for clear results early in Phase I clinical testing, given our thorough understanding of PRX012's characteristics. There's significant interest in this space regarding licensing, which we view positively. We are pleased to see not only sustained momentum but an increasing buildup around these approaches that may reduce some limitations of the anti-Aβ antibodies while potentially enhancing their primary mechanism of action, which is amyloid removal. Brandon, could you elaborate on the current dynamics within the business development space, especially in this class?

Yes, I appreciate that, Gene. And I appreciate the question. So from the market perspective, there is clearly a high level of interest for the approach that we're taking. And what we're building off of relative to what gantenerumab saw when they added transferrin and turned it into trontinemab, we think we're uniquely suited to build upon that story. And the market has begun to recognize that, and our dialogues are active. That's probably the best I can say about the BD dialogue. What's really interesting about the space, though, is also the opportunity potentially to grow. And what we're following very closely is that profile that Gene described, which is once-a-month subcu, leveraging a better ARIA profile that we expect to see and hope to see coming with the addition of transferrin is uniquely suited for where the market is heading, not just early Alzheimer's disease, which we think we have a unique capability there, but really around the presymptomatic space. We're looking forward to what the field is seeing in the presymptomatic space. We expect readouts this year. And that opens up a unique opportunity for us because we are a paradigm that is much less frequent, much less cumbersome. And when we're talking about those presymptomatic patients, that's exactly what they need. You need something that is uniquely set up for them, something that is not cumbersome and it potentially helps prevent the progression. So that's recognized in the field and something that is very interesting. Obviously, we're also very interested in the data that we're generating internally to help build upon that program. We hope to talk about that over the course of this year, internally with you and with our potential partner.

Your next question comes from the line of Eric Schmidt with Cantor Fitzgerald.

This is Alexa Deemer on for Eric. Congrats on the great year. So for the Phase I study of 019, which is expected to complete this year, do you plan to share data from the study this year? And what do you want to see for this program to advance?

Yes. It's a great question. Thank you for the question. So with PRX019, that is a program that we have a partnership with Bristol Myers Squibb on. We have not, for strategic reasons, talked about the target of that yet, except to say that it's broadly applicable to neurodegeneration. I think as Chad mentioned in his comments, that Phase I study is being conducted by us. We expect that to complete this year. And what we would then do is share that information with our partners at Bristol Myers Squibb. And I think you heard both Tran earlier say, and I said in my remarks as well that the potential to achieve up to $105 million this year through partner programs, some of that is tied to decisions made around PRX019. So what we expect is that we'll share that information with Bristol-Myers Squibb at the end of the day, it will be up to them to decide what and how much of that information to share publicly. But obviously, we'll be talking about that a little bit later this year. And with that said, maybe, Tran, you can add.

Just a reminder, they have global rights to this program. They exercised it. They paid us $80 million for it. So hence, the data is theirs and theirs to decide on how to disseminate that. So that being said, what we would do is, of course, announce if we've earned and they've taken that molecule forward into further clinical development, and that's when we'll earn the clinical milestone associated with PRX019.

Your next question comes from the line of Jason Butler with Citizens.

Can you maybe just from a broader level, speak to how you would think about the amount of data necessary to secure a partnership for the CYTOPE platform? Or ultimately, if you made the decision to advance the program into the clinic yourselves from the CYTOPE platform, what data you'd want to see to de-risk the initial clinical development?

Yes. Thanks for the question, Jason. So maybe I can start with a little bit of the biology here, and then Brandon can speak a little bit to just the development strategy. But I think from a TDP-43 perspective, the data we shared last year, I think, was interesting, both with respect to the CYTOPE technology and also to the idea of targeting TDP-43 in the context of ALS. And Phil covered this in some of his remarks. But I think for the CYTOPE technology, one of the things you clearly saw and particularly in those animal studies, the in vivo animal studies in the rNLS8 mice is you saw that with systemic administration, you were not only seeing activating with this intracellular target in a very disease or pathological specific way, but you were seeing actually removal of that target. And in the CNS, you were seeing that as well. So not only does this platform appear to allow us to target things in the intracellular space, but also seems to allow us to do so in the central nervous system as well. And so we think that, that's a really important lesson learned from the technology. And again, as was mentioned by Phil, we're not seeing any evidence that we're disrupting endosomes or causing problems that other forms of technology that have attempted to do these sorts of things have suffered from. I think in terms of ALS, it's particularly interesting. We know 97%, again, Phil covered some of this, 97% of patients has TDP-43 dysfunction as a core element of their pathology. And one of the challenges in targeting TDP-43 intracellularly directly is how to target the abnormal form of these proteins while leaving the normal form to do a day job, which is essential for cells to function properly. And so by having a very specific targeting approach, you were able to see that specificity translate into not only kind of sorting out the toxic gain of function, which is the aggregate that you see in the cytosol, but also interestingly in vitro setting in human cell types, correcting the loss of function, which is really the misplicing variant or the misplicing dysfunction that you see in the level of the nucleus. And so that seemed to be corrected as well. So we're excited by those data. We think the mouse model, which is an extraordinarily aggressive mouse model, most folks in an unchanged way, if they don't change the mouse model in some way, really struggle to see any effect here, we saw some very robust clearing of the intracellular aggregates of TDP-43. So that said, in terms of what we need to see, we think we're very excited by what these data are telling us to date. And obviously, we are interested in continuing to move that program forward. In terms of just the strategy around this program and potentially other programs within our CYTOPE technology platform, maybe, Brandon, you can speak a little bit to that.

Yes. It's important to note that the technology became publicly known only in November of last year, which sparked many conversations. We are discovering that there is a vast array of applications for this technology, extending well beyond neuroscience, our primary field, and it is essentially applicable across various therapeutic areas. This allows us to address a wide range of issues that our potential partners are looking to tackle using this technology. One specific example, as mentioned in our call, is that even within the last 3 to 4 months, we have formed specific research collaborations and have others in progress that aim to apply our insights from the TDP-43 program to targeted areas of interest. This broader application is particularly well-suited for this technology, and we are pleased with the progress we've made. Concurrently, during these discussions, potential partners are dedicating their time and resources to acquire this technology for their own use. This is new and exciting for them, and they are eager to validate our findings with their own targets. This approach will enable us to move towards partnerships focused on these targets or even broader applications. We are very optimistic about our current position and the future ahead.

Your next question comes from the line of Brian Abrahams with RBC Capital Markets.

This is Nevin on for Brian. Just a couple from us. So I guess I'm curious to know, based on some of the preclinical experiments that you've done in-house, what you think might be maybe some of the mechanistic hypothesis for why the transferrin modification ends up reducing the ARIA risk. And I guess along with that, do you expect potential lower heme toxicities with this? And then an additional clarification question on my end. Just wanted to see if the transferrin modification to PRX012 would still enable PRX012 to be subcutaneously delivered or if this would be IV administered.

Yes, those are good questions regarding PRX012. I’ll start off, and Phil can add if he has anything. First, regarding the transfer and how it relates to ARIA events, there are many hypotheses. One that both Roche and Eli Lilly suggest as a likely mechanism relates to the location of transferrin in the cerebral vasculature. This theory proposes that better penetration into the brain through capillaries, as opposed to arteries, might provide some benefits. There is some validity to this, considering that amyloid deposits in the cerebral vasculature typically occur in the larger arterial structures, especially in the perivascular space. Therefore, altering the route of entry to the capillary system could offer advantages. Another idea discussed in the field is about the duration the antibody remains on amyloid in the vasculature. With the transferrin-based approach, transcytosis across the blood-brain barrier might reduce that time. It’s possible that a combination of factors is at play. This highlights that we need to ensure the transferrin-based approach we are taking with PRX012 shares characteristics with methods that have been successful previously. The data set we have so far is quite small, similar to the gantenerumab and trontinemab stories we’ve mentioned. We aim to maintain a consistent approach to ensure we effectively leverage whatever mechanism is in play. Regarding the subcutaneous part of your question, we believe the inclusion of transferrin will not necessitate changing our method of administration. Subcutaneous delivery remains a viable option for PRX012 transferrin-based formulations. In fact, the potency of PRX012 allows us to achieve a biological effect at lower doses, providing both pharmacokinetic and potency advantages. This is evident from our data showing that PRX012 effectively reduces amyloid, particularly at the 400-milligram dose, which appears to be more robust compared to earlier gantenerumab data. This reinforces the potency of PRX012, which we believe is crucial for ensuring that it can be effectively administered subcutaneously. Phil or Chad, do you have any comments on this?

I want to mention one thing, Gene. You've touched on the potency, which is important. We see comparable and strong levels of reduction at 18 months with an antibody that has a flat dose of 400, significantly less than the 10 mg per kg currently in the clinic. Because of this, although we don't know for sure, I understand you had a question regarding heme toxicity. It's possible that we could dose at lower levels and achieve similar effects as seen with trontinemab. If this holds true, there may be a chance to reduce the risk associated with these non-ARIA adverse events, like anemia and others. So, I think there's potential, but we need to conduct the study.

Thank you, everyone. That completes our question-and-answer session. I'll now turn it over to Gene Kinney, CEO, for closing remarks.

Thank you, operator. And I want to thank you all for joining us on the call today. We appreciate your interest in Prothena and look forward to sharing further updates on our programs.

Thank you for your participation in today's conference call. This concludes the presentation. You may now disconnect. Good day.