ADSLD Gene Therapy Community Update June 22, 2026

We wanted to share a summary of recent discussions about ADSL research, our fundraising efforts, and the path toward future treatments. Our goal is to keep families informed about where we are today, what we know, and what questions still remain.

Where We Are Today

Rare Birds Foundation is currently focused on advancing the most promising therapeutic approaches for ADSL Deficiency, with gene therapy as our primary research priority.

Current evidence suggests that gene therapy may be able to provide the body with a working copy of the ADSL gene, helping to stop or slow ongoing damage caused by enzyme deficiency. However, based on what is currently understood, gene therapy is not expected to reverse neurological damage that has already occurred.

Because ADSL Deficiency causes toxic metabolite buildup that damages white matter and myelin, preventing further injury is an important goal.

Why We Are Raising $250,000

Our current fundraising campaign is designed to support critical preclinical research. Dr. Chen exhausted much of the funding from Iva to test the therapy in skin cells from Minja and to develop a mouse that could live with ADSLD. Now, as they begin the work of testing in those mice, more funding is needed to see the project through until the end.

Approximately $200,000 is intended to advance Dr. Xin Chen's gene therapy program at the University of Texas (UT) Southwestern to generate the proof-of-concept data needed to compete for larger research grants and future funding opportunities. Recently, Dr. Chen’s team successfully developed a mouse model and has begun testing on mice with ADSL Defiency. These funds will help progress this timely research and ensure the program maintains momentum. The remaining $50,000 will provide flexibility to support collaborative research efforts and additional studies that may strengthen the overall development program and get us closer to FDA approval.

This fundraising campaign is intended to bridge the gap between early-stage research and larger institutional funding sources. Long-term development of an approved therapy will require significantly greater investment, likely through grants, partnerships with industry, venture philanthropy, and other major funding sources.

Collaboration Between Research Teams

While we do intend to raise the full amount Dr. Chen has requested, Rare Birds is actively encouraging collaboration between Dr. Xin Chen's team at UT Southwestern and Dr. Marie Zikanova's team in Prague.

To avoid duplicating work and to maximize the impact of limited research dollars, a collaborative proposal is currently being explored by Dr. Zikanova’s team to identify opportunities for shared studies, data generation, and cost efficiencies.

Rare Birds will continue to direct funding toward the research strategy that shows the strongest scientific promise and the greatest potential benefit for the ADSLD community.

Why Gene Therapy Is the Current Focus

Over the past several years, researchers have evaluated multiple treatment approaches, including drug repurposing strategies such as Allopurinol and Disulfiram.

While these approaches may provide limited stabilization or symptom management for some individuals, they are not considered curative therapies and do not address the underlying genetic cause of ADSL Deficiency.

As a result, Rare Birds has shifted its primary research focus toward gene therapy and other approaches that have the potential to address the root cause of the disease. However, our new collaboration with a research team in Vienna holds promise for repurposed drug candidates, and they seem poised for a warm hand-off of research from Dr. Wendy Hanna-Rose and her team at Penn State. We will learn more this week.

Understanding the Treatment Development Process

Developing a therapy for an ultra-rare disease is a long and complex process.

Historically, bringing a treatment from laboratory research to FDA approval has cost tens of millions of dollars. Gene therapy programs for other rare diseases have required as many as 10 years from initial development to first patient dosing, although advances in technology are helping shorten timelines.

The FDA is also actively exploring ways to make rare disease development more efficient, and programs such as the Priority Review Vouchers encourage pharmaceutical companies to invest in therapies for small patient populations. In addition, the FDA is moving towards the elimination of expensive Phase 3 clinical trials for ultra-rare disorders, which would drastically shorten our timeline and be more cost effective.

Future Clinical Trials

If proven safe for use in humans, some patients may receive the investigational therapy during clinical trials before FDA approval is obtained.

While no clinical trial has been designed for the AAV-9 Gene Therapy for ADSLD, current expectations are that early trials may prioritize younger children, based on experience from other rare disease gene therapy programs.

However, ADSL Deficiency affects a very small patient population, and future inclusion criteria will ultimately be determined by scientific and regulatory considerations. It may be possible that age restrictions could be more flexible than those seen in larger disease groups.

Fundraising and Future Treatment Costs

One of the most important clarifications is that current fundraising efforts support research development, not individual treatment costs.

Funds raised today are being used to move research forward and generate the data needed to advance toward clinical trials.

Questions remain regarding the eventual cost of treatment, particularly regarding the cost before FDA approval. (If the treatment is FDA approved, Insurance benefits will be a consideration.) Preliminary discussions have referenced a potential cost of approximately $350,000 per dose, but this figure is not finalized and requires additional clarification from researchers. The cost may change over time as manufacturing processes improve and more gene therapies reach the market.

What We Still Don't Know

Several important questions remain unanswered:

• The exact cost structure for ADSLD-specific gene therapy development.

• How treatment costs may be shared among patients, insurers, researchers, and sponsors.

• Whether there is a specific age or disease stage at which gene therapy provides the greatest benefit.

• How much of the disease burden occurs during early childhood versus later life.

• What FDA requirements will look like when clinical trials are ready to begin, as these are in flux at the moment.

  
  

To help answer some of these questions, Rare Birds is working to support both treatment development and natural history research at the National Institutes of Health (NIH) that will improve our understanding of disease progression over time.

Next Steps

Over the coming weeks, Rare Birds plans to:

• Publish an ADSL Research Roadmap connecting fundraising milestones to research progress.

• Continue fundraising for ongoing preclinical research.

• Evaluate collaboration opportunities between research groups.

• Learn from other rare disease organizations that are further along in the gene therapy development process.

• Begin identifying larger-scale funding partners, including venture philanthropists and pharmaceutical industry collaborators.

  
  

A Final Note

We know families are eager for treatments and timelines. While there are still many unknowns, meaningful progress is being made. The current fundraising campaign is an important step toward generating the data needed to unlock larger funding opportunities and move ADSL gene therapy closer to the clinic.

We remain committed to transparency, scientific rigor, and keeping the patient community informed every step of the way.