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Study to Evaluate mRNA-3210 for Safety and Tolerability in Patients with Phenylketonuria

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a condition called Phenylketonuria (PKU), which is a rare genetic disorder that affects how the body processes a substance called phenylalanine, found in many protein-containing foods. The study will use a new treatment called mRNA-3210, which is designed to help manage PKU by providing the body with instructions to produce a specific enzyme that helps break down phenylalanine. This treatment is given through an injection into the vein.

The purpose of the study is to evaluate the safety and tolerability of mRNA-3210 in people with PKU. Participants will receive different doses of the treatment to find the most suitable dose. The study will monitor how the body responds to the treatment and any side effects that may occur. Participants will have regular check-ups and tests to assess their health and the treatment's effects over the course of the study.

In addition to mRNA-3210, the study will also involve other medications such as Hydroxyzine Hydrochloride, Buclizine Hydrochloride, Paracetamol (also known as acetaminophen), Codeine Phosphate, Ibuprofen Lysine, Pseudoephedrine Hydrochloride, Cetirizine Dihydrochloride, Fexofenadine, Famotidine, and Diphenhydramine. Some participants may receive a placebo instead of the active treatment. The study aims to gather information on how these medications interact with mRNA-3210 and their overall impact on managing PKU.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Upon joining the study, an initial assessment is conducted to confirm eligibility. This includes a review of medical history and a genetic test to confirm a diagnosis of phenylketonuria (PKU).

    Blood samples are taken to measure phenylalanine (Phe) levels. These samples are collected at least 72 hours apart during the screening period.

  2. Step 2

    Dietary evaluation

    A study dietitian evaluates dietary protein intake to ensure it remains consistent with baseline levels throughout the study.

    Approval from the dietitian and the investigator is required to confirm that diet alone will control the disease during participation.

  3. Step 3

    Medication stability

    If applicable, any neuropsychiatric medication must be stable prior to enrollment and remain stable throughout the study unless a change is clinically necessary.

  4. Step 4

    Study medication administration

    The study involves the administration of mRNA-3210 through an intravenous route. This is a dose escalation study, meaning doses will increase over time to assess safety and tolerability.

    The primary objective is to evaluate the safety and tolerability of multiple doses of mRNA-3210.

  5. Step 5

    Monitoring and follow-up

    Participants are monitored for any treatment-emergent adverse events (TEAEs).

    Regular blood tests are conducted to measure changes in blood Phe levels and to characterize pharmacokinetic (PK) and pharmacodynamic (PD) parameters.

    The presence and levels of anti-PEG antibodies are also assessed.

  6. Step 6

    Study duration

    The study is expected to continue until August 2027, with recruitment starting in September 2024.

    Participants are required to use effective contraception during the study and for three months after the last administration of the study medication.

Who can join the trial?

7 criteria

  • Participants must have signed a written informed consent before any study procedures are done.
  • Participants must be between the ages of 18 and 70 at the time of giving consent.
  • Participants must have a confirmed diagnosis of **Phenylketonuria (PKU)** due to **PAH deficiency** through genetic testing. PKU is a condition where the body can't break down an amino acid called phenylalanine, and PAH deficiency is a specific cause of PKU.
  • Participants must have at least three blood **phenylalanine (Phe)** levels of 600 micromoles per liter or higher. Phe is an amino acid that people with PKU have trouble processing. These levels should be measured at specific times: two during the screening period and one from 6 to 24 months before the screening starts.
  • Participants must have approval from a study dietitian confirming they can maintain their usual protein intake during the study, and from the investigator confirming that diet alone can control the disease during the study.
  • If participants are taking medication for mental health conditions like ADHD, depression, or anxiety, they must have been on a stable dose before joining the study and be willing to keep the dose stable during the study unless a change is needed for medical reasons.
  • Sexually active females who can have children and sexually active males must agree to use a highly effective method of birth control during the study and for three months after the last dose of the study treatment.

Who cannot join the trial?

4 criteria

  • Participants who do not have **Phenylketonuria**. Phenylketonuria is a genetic condition where the body cannot break down a certain amino acid called phenylalanine.
  • Participants who are not within the specified age range. The study is open to certain age groups, so if you are outside this range, you cannot participate.
  • Participants who are not part of the specified clinical trial groups. The study may be looking for specific characteristics or conditions in participants.
  • Participants who are part of a vulnerable population. This means people who might be at higher risk of harm or exploitation, such as children or those unable to give consent, are not included.
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Investigated drugs

mRNA 3210 is an experimental treatment being studied for its potential to help people with Phenylketonuria, a genetic disorder that affects the body's ability to break down a certain amino acid. This medication is designed to be given through an intravenous (IV) infusion, meaning it is delivered directly into the bloodstream. The study aims to understand how safe and tolerable this treatment is when given in increasing amounts to participants.

What is already known about the treatment

mRNA-3210 – This medication is administered intravenously and is currently in Phase 1/2 clinical trials. It is being studied for its potential use in treating individuals with phenylketonuria, a genetic disorder. The main therapeutic goal is to evaluate its safety and tolerability in patients. At the molecular level, mRNA-3210 works by delivering messenger RNA to cells, which instructs them to produce specific proteins that may be deficient or dysfunctional in phenylketonuria. It falls under the pharmacological classification of gene therapy products.

Investigated diseases

Phenylketonuria – Phenylketonuria is a rare genetic disorder that affects the body's ability to break down an amino acid called phenylalanine. This amino acid is found in many protein-containing foods and some artificial sweeteners. In individuals with phenylketonuria, the enzyme needed to process phenylalanine is deficient or absent, leading to a buildup of phenylalanine in the blood. Over time, high levels of phenylalanine can cause a variety of health problems, particularly affecting brain development and function. Symptoms may include intellectual disabilities, behavioral problems, and seizures. Early diagnosis and management are crucial to prevent these complications.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2023-506963-32-00Protocol codemRNA 3210-P101Estimated enrolment54 patientsSponsorModerna Therapeutics Inc.

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