ATH434's Phase 3 Path Is Set: Alterity on What FDA Alignment Means for MSA

In early June, Alterity Therapeutics announced that it had achieved alignment with the FDA following a successful End-of-Phase 2 meeting for ATH434, its investigational oral iron redistribution agent in development for multiple system atrophy (MSA). The FDA agreed on the key elements of the proposed Phase 3 design, including the study population, the 50 mg twice-daily dosing regimen, a 12-month treatment duration, and the 11-item UMSARS Part I as the primary efficacy endpoint. The alignment clears the path for a pivotal registrational trial, with activities on track to initiate by year-end 2026.¹

In a randomized, double-blind, placebo-controlled Phase 2 trial, ATH434 previously demonstrated a 46% relative slowing of disease progression on the UMSARS Part I compared with placebo with a favorable safety profile and neuroimaging findings consistent with reduced toxic iron accumulation in affected brain regions. The drug has also received Fast Track and Orphan Drug designations from the FDA, underscoring the significant unmet need in MSA, a rapidly progressive neurodegenerative disease where the median survival is approximately 7.5 years from symptom onset and no disease-modifying therapies are currently approved.

In this Q&A, David Stamler, MD, Chief Executive Officer of Alterity, discusses what FDA alignment at the End-of-Phase 2 stage means for the ATH434 development program, why UMSARS Part I was selected as the primary endpoint, how the Phase 2 findings shaped the Phase 3 design, and what a successful pivotal trial could ultimately mean for the up to 50,000 individuals living with MSA in the United States.

What does achieving FDA alignment at the End-of-Phase 2 meeting mean for the ATH434 development program, and how does it de-risk the path to a pivotal phase 3 study?

Achieving alignment with the FDA at our End-of-Phase 2 (EOP2) meeting is an important milestone for Alterity as well as for the individuals living with Multiple System Atrophy (MSA). In the biotech industry, a successful EOP2 meeting represents the transition from an exploratory phase of development to a definitive, registrational pathway.

For the ATH434 program, this alignment gives us the clarity to finalize our protocol and advance to a pivotal Phase 3 study, and we are on track to initiate trial activities by the end of 2026. This de-risks the path forward: it removes uncertainty around the protocol and its design elements, including the study population, treatment duration, and dosing regimen. It also helps validate the primary endpoint, secondary endpoints and planned statistical analysis.

Combined with our existing Fast Track and Orphan Drug designations, this alignment gives us a clear roadmap to potentially bring the first disease-modifying therapy to patients living with MSA, a truly devastating disease.

The FDA agreed to use UMSARS Part I as the primary endpoint. Why was this measure selected, and what makes it a meaningful endpoint for patients with MSA?

The FDA likes to focus on endpoints that measure how a patient feels or functions.And if you talk to individuals living with MSA or their care partners, what matters most to them is whether they can take care of themselves and maintain independence for longer. That is why the selection of the UMSARS Part I, with the FDA’s alignment, is so meaningful for us and the MSA community.

The UMSARS Part I is a scale that focuses on the most important areas of daily function that are affected in MSA. In our Phase 2 study, this scale allowed us to detect a 46% relative slowing of disease progression compared to placebo and the difference was statistically significant.

For an MSA patient, a "meaningful endpoint" isn't an abstract statistical value. It translates directly into how they can communicate with others, care for themselves, and maintain autonomy. The items on the UMSARS scale measure things that are important in day to day living such as, speech and swallowing, handwriting and feeding, hygiene and dressing, and mobility. Generally, a 1.5-point differential is understood to provide a clinically meaningful difference. Because the FDA prioritizes functional measures that reflect the patient's actual lived experience, the UMSARS Part I is the right endpoint for our pivotal study.

Can you discuss the rationale behind the final phase 3 design, including the selected patient population, treatment duration, and 50 mg twice-daily dosing regimen?

The Phase 3 design builds on the successful Phase 2 trial, where ATH434 demonstrated meaningful benefit on functional endpoints to investigate the drug’s safety and efficacy in a larger study population as we move towards potential approval for the treatment of MSA.

Regarding the patient population, we’ve optimized the design to select participants who are most likely to benefit from intervention. Because MSA is such an aggressive and debilitating disease, early intervention matters. So, we’ve opted to target MSA patients who are still ambulatory and most likely to benefit from treatment that potentially slows disease progression.

Regarding treatment duration, we have aligned with the FDA on 12-months treatment in the pivotal study, coinciding with our Phase 2 trial. It was over this timeframe that the treatment effect resulted in a 46% relative slowing of disease progression. We believe this is long enough to demonstrate a similar treatment effect as was observed in Phase 2, yet short enough to maximize patient participation and operational efficiency.

And for the dosing regimen, the orally administered 50 mg twice daily (100 mg total daily) dose level achieved clinically and statistically significant efficacy in Phase 2 on the UMSARS Part I scale.

Furthermore, our neuroimaging analyses were consistent with ATH434 reducing the toxic effects of the reactive form of iron in affected brain regions and showed trends in preserving brain volume. And importantly, in our Phase 2 study, the 50 mg twice-daily dose was well-tolerated, with adverse event rates comparable to placebo, and no serious adverse events that were attributed to ATH434.

ATH434 demonstrated a 46% slowing of disease progression on UMSARS Part I in phase 2. How did those findings help shape the phase 3 program, and what will you be looking to confirm in the pivotal study?

The positive Phase 2 results translated directly to how we are structuring the Phase 3 program. In Phase 3, our primary objective is to demonstrate that the treatment effect observed in the Phase 2 is reproducible in a larger, well-defined patient population and that ATH434 continues to demonstrate a favorable safety profile. These will be the cornerstones supporting an application for marketing authorization.

If successful, what impact could ATH434 have on the treatment landscape for MSA, where there are currently no approved disease-modifying therapies?

MSA is an incredibly tough and devastating diagnosis. Currently, physicians lack treatments to slow the course of neurodegeneration. The current standard of care is purely symptomatic treatments to help maintain blood pressure on standing, and a drug called levodopa which can offer some temporary, modest help with parkinsonian symptoms like slowed movements and stiffness. But with symptomatic treatments, the disease continues to progress.

The median survival is only about 7.5 years from symptom onset, and more than half of patients will require a wheelchair within 5 years. Our goal with ATH434, pending a successful Phase 3 trial, will be to establish a new treatment paradigm, moving from temporary symptom improvement to slowing of disease progression by targeting the underlying pathology of the disease.

For the up to 50,000 individuals living with MSA in the United States and the hundreds of thousands globally, a successful Phase 3 study for ATH434 offers the prospect of meaningfully altering the course of the disease. That is the future we are urgently working towards.

REFERENCES
1. Alterity Therapeutics achieves alignment with U.S. FDA on pivotal phase 3 program for ATH434 in multiple system atrophy. GlobeNewswire. June 9, 2026. Accessed August 17, 2026. https://www.globenewswire.com/news-release/2026/06/09/3308715/0/en/alterity-therapeutics-achieves-alignment-with-u-s-fda-on-pivotal-phase-3-program-for-ath434-in-multiple-system-atrophy.html
2. Alterity Therapeutics Reports Positive Topline Data from Open-Label Phase 2 Clinical Trial of ATH434 in Multiple System Atrophy. News release. Alterity Therapeutics. July 28, 2025. Accessed July 28, 2025. https://alteritytherapeutics.com/investor-centre/news/2025/07/28/alterity-therapeutics-reports-positive-topline-data-from-open-label-phase-2-clinical-trial-of-ath434-in-multiple-system-atrophy/