This study is testing whether high-dose Vitamin C is safe and well-tolerated in patients with two inherited red blood cell disorders - Pyruvate Kinase Deficiency (PKD) and Class A Glucose-6-Phosphate Dehydrogenase Deficiency (G6PDA). Both conditions cause red blood cells to break down too quickly, leading to anemia and related complications.

Our earlier research showed that a single oral dose of Vitamin C (250 mg, 500 mg, or 750 mg) reduced red blood cell breakdown by approximately 50% within one hour. This study builds on those findings by testing different doses and frequencies of Vitamin C to find the safest and most effective dosing schedule.

Participants will take Vitamin C once, twice, or three times daily over a 3-week period, with careful monitoring of blood counts, red blood cell survival, iron levels, and any side effects. The study will first enroll 3 adult patients with PKD at Huntsman Cancer Institute. If the results are safe and promising, the study will be extended to patients with G6PDA deficiency, and eventually to children ages 4 and older at Primary Children's Hospital in Salt Lake City.

The goal is to establish a foundation for Vitamin C as a novel therapy to reduce anemia and red blood cell destruction in these rare inherited disorders.

Pyruvate kinase deficiency (PKD) and Class A Glucose-6-Phosphate Dehydrogenase deficiency (G6PDA) are inherited red blood cell enzyme disorders characterized by chronic hemolytic anemia. Current treatment options are limited and do not fully address the underlying mechanisms of red blood cell destruction, iron overload, and oxidative stress.

Our preliminary studies demonstrated that oral Vitamin C administration at doses of 250 mg, 500 mg, and 750 mg reduced the rate of hemolysis by approximately 50% within one hour of administration, as measured by end-tidal carbon monoxide corrected for ambient CO (ETCOc) - a validated marker of red blood cell breakdown. These findings provide a strong rationale for evaluating the safety and optimal dosing frequency of Vitamin C supplementation in these patient populations.

Study Design:

This is a Phase I, single-site, sequential within-patient dose escalation study. Three adult PKD patients will be enrolled in the initial cohort, each assigned to a different starting dose:

Patient 1: 250 mg daily → 250 mg twice daily → 250 mg three times daily Patient 2: 500 mg daily → 500 mg twice daily → 500 mg three times daily Patient 3: 750 mg daily → 750 mg twice daily → 750 mg twice daily + 500 mg once daily (to reach the NIH-recommended maximum daily dose of 2,000 mg/day)

Each dosing frequency will be maintained for one week, for a total active treatment period of 3 weeks per participant. Safety and hematologic assessments will be performed at baseline and at each dose adjustment visit (9 assessments per participant).

Assessments:

At each visit, participants will undergo:

ETCOc measurement to assess real-time hemolysis Complete blood count and reticulocyte count Metabolic panel including bilirubin and LDH Iron studies including serum iron, transferrin, ferritin, hepcidin, and erythroferrone Vital signs and adverse event assessment

Study Extension:

Following successful completion of the PKD cohort, the study will be extended to G6PDA patients, including 5 G6PDA males and 5 G6PDA heterozygous females from a well-characterized family. A subsequent extension to pediatric patients ages 4 and older is planned at Primary Children's Hospital in Salt Lake City, pending safety and preliminary efficacy data from the adult cohort.

Inclusion Criteria:

• Confirmed diagnosis of Pyruvate Kinase Deficiency (PKD) or Class A glucose-6-phosphate dehydrogenase (G6PD A) as verified by genetic mutation documentation or enzymatic testing
• 18 years of age or older
• Able to take oral medications either by mouth or via gastrostomy tube
• Willing and able to provide written informed consent prior to any study procedures
• Heterozygous female carrier of G6PDA deficiency

Exclusion Criteria:

• Does not have an established diagnosis of Pyruvate Kinase Deficiency (PKD) or Class A Glucose-6-Phosphate Dehydrogenase Deficiency (G6PDA)
• Unable to tolerate oral medications either by mouth or gastrostomy tube
• Currently pregnant or planning to become pregnant during the study period
• Incarcerated individuals
• Unable to provide written informed consent or assent
• Known allergy or hypersensitivity to Vitamin C (ascorbic acid)

De-identified individual participant data will be made available upon reasonable request following publication of study results. Data will be stored securely at the Huntsman Cancer Institute and shared in accordance with applicable IRB and institutional data sharing policies.

Beginning 6 months after primary results publication and available for 5 years thereafter

Researchers may submit data access requests to the Principal Investigator (Jihyun Song, PhD) at jihyun.song@utah.edu. Requests will be reviewed on a case-by-case basis.