# Quantitative Measurement of Phenylalanine Metabolism in Sapropterin-Responsive Hyperphenylalaninemia

> **NIH NIH U54** · OREGON HEALTH & SCIENCE UNIVERSITY · 2021 · $121,848

## Abstract

5. PROJECT SUMMARY – PROJECT 2
The goal of this project is to validate noninvasive methods of measuring whole body phenylalanine (Phe)
metabolism rates that are not confounded by dietary Phe intake in individuals with phenylalanine hydroxylase
(PAH) deficiency. Future clinical trials of liver-directed gene therapy for the treatment of PAH deficiency will
require the use of such methods to measure treatment efficacy. We propose to evaluate two different methods
of measuring Phe metabolism: 1) measurement of 13CO2 enrichment in breath over time following oral
administration of 1-13C-L-phenylalanine, and 2) measurement of plasma Phe clearance and plasma tyrosine
production following oral unlabeled Phe challenge in a fasting state. These measures will be repeated over
time in the same cohort of study subjects with full or partial PAH deficiency in order to assess the sensitivity
and test-retest variability of the methods. This project will assess the sensitivity and stability of the proposed
testing methods in measuring Phe metabolism non-invasively and prepare a clinical trial ready protocol for
future use.

## Key facts

- **NIH application ID:** 10260445
- **Project number:** 5U54HD100982-03
- **Recipient organization:** OREGON HEALTH & SCIENCE UNIVERSITY
- **Principal Investigator:** Cary O. Harding
- **Activity code:** U54 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $121,848
- **Award type:** 5
- **Project period:** 2019-09-16 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10260445

## Citation

> US National Institutes of Health, RePORTER application 10260445, Quantitative Measurement of Phenylalanine Metabolism in Sapropterin-Responsive Hyperphenylalaninemia (5U54HD100982-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10260445. Licensed CC0.

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