A Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of AG-181 in Subjects With Phenylketonuria

August 26, 2026 updated by: Agios Pharmaceuticals, Inc.

A Phase 1b, Open-label, Multicenter, Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics Study of AG-181 in Subjects With Phenylketonuria

The primary purpose of this study is to assess the safety and tolerability of AG-181 in subjects with Phenylketonuria (PKU).

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
20

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Poland
    • West Pomeranian Voivodeship
      • Szczecin, West Pomeranian Voivodeship, Poland, 71-252
        • Recruiting
        • Centrum Wsparcia Badań Klinicznych Pomorskiego Uniwersytetu Medycznego w Szczecinie
  • United States
    • Indiana
      • Indianapolis, Indiana, United States, 46202
        • Recruiting
        • Indiana University
    • Pennsylvania
      • Pittsburgh, Pennsylvania, United States, 15224
        • Recruiting
        • UPMC Children's Hospital of Pittsburgh
    • Texas
      • Dallas, Texas, United States, 75390
        • Recruiting
        • University of Texas Southwestern Medical Center (UTSW)

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Key Inclusion Criteria:

  • Diagnosis of PKU, defined as documented presence of 2 mutant alleles in the phenylalanine hydroxylase (PAH) gene, of which at least 1 is the R408W mutation, as determined during Screening per the genotyping performed by the study central genotyping laboratory.
  • At least 1 plasma Phe concentration greater than (>) 600 micromoles per liter (μmol/L) in the 52 weeks before providing informed consent.
  • Average concentration of plasma Phe > 600 μmol/L in Phe samples taken during Screening, with no individual assessment below 360 μmol/L. Any Phe samples taken after Day -20 will not be included.
  • Body mass index (BMI) greater than or equal to (≥) 18.0 kilograms per meter square (kg/m^2) to lesser than or equal to (≤) 35.0 kg/m^2 and weight ≥ 50 kilograms (kg) at any time during the Screening Period.
  • Documented approval from a dietitian confirming that the subject can maintain their diet consistent in protein and Phe intake throughout the study as outlined in the Diet Manual.

Key Exclusion Criteria:

  • Prior exposure to AG-181.
  • Receiving inhibitors of P-glycoprotein (P-gp) that have not been stopped for ≥ 5 days or a timeframe equivalent to 5 half-lives (whichever is longer) before administration of the first dose of study drug.
  • Receiving products that are strong inhibitors or strong inducers of cytochrome P450 CYP1A2, CYP2C8, or CYP3A that have not been stopped for ≥ 28 days before administration of the first dose of study drug.
  • Receiving treatment with an acid-reducing agent, including but not limited to proton pump inhibitors and H2 blockers. Short-acting acid-reducing agents such as calcium carbonate are permitted.
  • Any preexisting condition that could (in the opinion of the Investigator) interfere with gastrointestinal anatomy or motility that may disrupt the absorption, metabolism, and/or excretion of the study drug.
  • Any preexisting condition that could (in the opinion of the Investigator) interfere with hepatic or renal function that may disrupt the absorption, metabolism, and/or excretion of the study drug.
  • Inability to tolerate oral medication.
  • Unwillingness to washout from tetrahydrobiopterin (BH4) supplementation (eg, sapropterin dihydrochloride, Kuvan), pegvaliase-pqpz (Palynziq), or any other PKU therapy by Day -30 during Screening.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Non-Randomized
  • Interventional Model: Sequential Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Cohort 1: AG-181
Subjects will receive AG-181 from Day 1 to Day 28.
Drug: AG-181
AG-181 film-coated tablets
Experimental: Cohort 2 (Optional Cohort): AG-181
Subjects will receive AG-181.
Drug: AG-181
AG-181 film-coated tablets

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Number of Subjects with Adverse Events (AEs) and Serious Adverse Events (SAEs) by Type, Severity, and Relationship to the Study Drug
Time Frame: Up to Day 42
Up to Day 42

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Plasma Concentration of AG-181
Time Frame: Up to Day 28
Up to Day 28
Maximum Concentration (Cmax) of AG-181
Time Frame: Up to Day 28
Up to Day 28
Time to Maximum (Peak) Concentration (Tmax) of AG-181
Time Frame: Up to Day 28
Up to Day 28
Area Under the Concentration-Time Curve (AUC) of AG-181
Time Frame: Up to Day 28
Up to Day 28
Apparent Total Body Clearance (CL/F) of AG-181
Time Frame: Up to Day 28
Up to Day 28
Apparent Volume of Distribution in the Terminal Phase (Vz/F) of AG-181
Time Frame: Up to Day 28
Up to Day 28
Change From Baseline in Phenylalanine (Phe) Concentration
Time Frame: Baseline up to Day 28
Baseline up to Day 28

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Agios Pharmaceuticals, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
April 17, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
January 17, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
January 17, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
November 17, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 17, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 21, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
August 27, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 26, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
August 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • AG181-C-002
  • 2025 (U.S. NIH Grant/Contract: Faculty of Social Sciences Scientific Grant at the University of Gdańsk)
  • 2025-522630-31-00 (Ctis)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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