# Identification of Potential Biomarkers and Clinical Tools for use in Mucopolysaccharidosis IIIC Patients.

> **NIH NIH R44** · PHOENIX NEST, INC. · 2024 · $881,675

## Abstract

PROJECT SUMMARY/ABSTRACT
Lysosomal storage diseases (LSD) are rare inherited metabolic disorders caused by defects in the cellular
catabolic system. Mucopolysaccharidosis Type IIIC (MPS IIIC or Sanfilippo disease type C) is one such LSD
that is caused by deficiency of the enzyme heparan sulfate acetyl CoA: -glucosaminide N-acetyltransferase,
(HGSNAT) essential for degradation of heparan sulfate, a repeating carbohydrate generally found attached to
proteoglycans. This disease causes accumulation of heparan sulfate resulting in a progressive and severe
neurological deterioration early in life with little somatic features. The symptoms in patients with MPS IIIC may
present at an average age of 3.5 years of age with psychomotor developmental delays and behavioral problems.
Before the age of 15 years verbal communication is often lost in patients with MPS IIIC. Most lose the ability to
walk between the 20 and 30 years of age. The condition is fatal by an average age of 34 years (range, 25-48).
Enzyme replacement therapies are not an option since the protein is localized and bound to lysosomal
membrane. There are currently no treatments available for treatment of MPS IIIC. Individuals affected by
MPS IIIC are managed with supportive care, consultation with medical professionals from multiple disciplines,
physical therapy, and pharmacological interventions to alleviate symptoms. Gene therapy represents a
reasonable and promising approach to provide a meaningful and long-term therapeutic benefit for this population
in the near future.
We had a positive interaction with the FDA and got guidance for moving our program into the clinics. In
preparation for the interventional study the recommendation was for a thorough natural history study (NHS) in
the available patient population with a broad net to capture endpoints that are most likely to predict the clinical
benefits in individuals. Since the number of diagnosed patients is small, individuals could potentially serve as
their own control at the time of intervention, where the patient will receive the gene therapy. Most of the work will
be executed by contracted service providers. The clinical trial itself will be conducted at UT Southwestern Medical
Center, Dallas, TX. The clinical protocol was designed by the team at Phoenix Nest with help of KOLs and clinical
experts in the MPS III field. We have engaged expert third party clinical service providers to help with the
execution, monitoring and data collection. Crucial data collected from the patients on this study will help us
develop clinical outcomes that will be tools for measuring the efficacy of our AAV9 gene therapy. This trial will
put a step closer to executing the pivotal trial to assess the efficacy of our experimental therapy and its
commercialization.

## Key facts

- **NIH application ID:** 10921133
- **Project number:** 1R44NS137892-01
- **Recipient organization:** PHOENIX NEST, INC.
- **Principal Investigator:** Srikanth Singamsetty
- **Activity code:** R44 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $881,675
- **Award type:** 1
- **Project period:** 2024-07-01 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10921133

## Citation

> US National Institutes of Health, RePORTER application 10921133, Identification of Potential Biomarkers and Clinical Tools for use in Mucopolysaccharidosis IIIC Patients. (1R44NS137892-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10921133. Licensed CC0.

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