Early-stage research
Phase 1 studies primarily examine safety, tolerability and how an investigational treatment behaves in the body.
Research & Innovation | PKU Research Update
Agios Reports Progress in Phase 1b Study of AG-181 for Adults with PKU
Agios Pharmaceuticals has announced that the first participant has received a dose in a Phase 1b clinical trial evaluating AG-181, an investigational phenylalanine hydroxylase stabilizer, in adults living with phenylketonuria.
Overview
Agios Pharmaceuticals released its second-quarter 2026 financial results and business update on July 30, 2026. Among several company and research announcements, Agios confirmed an important development for the phenylketonuria community: the first participant has been dosed in a Phase 1b study of AG-181.
AG-181 is an investigational treatment being studied in adults with PKU. Agios describes it as a phenylalanine hydroxylase, or PAH, stabilizer. The Phase 1b trial is evaluating its safety and tolerability.
Agios expects to report data from this trial during the second half of 2026. The timing and content of future updates may change as the study progresses.
First participant dosed in the AG-181 Phase 1b trial
According to the Agios announcement, the company has dosed the first participant in its Phase 1b clinical trial of AG-181 in adults with PKU.
This early-stage study is focused on evaluating the safety and tolerability of AG-181. These studies help researchers understand how an investigational treatment behaves in people and whether further clinical development may be appropriate.
Agios stated that data from the Phase 1b trial are expected in the second half of 2026.
What is AG-181?
AG-181 is an investigational phenylalanine hydroxylase stabilizer being developed by Agios for PKU.
Phenylalanine hydroxylase, commonly called PAH, is the enzyme that helps the body convert phenylalanine into tyrosine. In most people with PKU, changes in the PAH gene reduce the amount or activity of this enzyme, allowing phenylalanine to accumulate.
A PAH stabilizer is intended to support or stabilize certain forms of the PAH enzyme. Whether AG-181 can safely produce a meaningful treatment benefit for people with PKU must be determined through clinical research.
Important distinction
AG-181 remains investigational. It has not been approved as a treatment for PKU, and the Phase 1b trial is an early stage of clinical development.
What does this update mean for the PKU community?
Dosing the first participant is an important operational milestone for a clinical trial. It means that the study has moved from planning and preparation into active evaluation in participants.
It does not yet show that AG-181 is safe, effective or suitable for broad use. Those questions require clinical evidence gathered across the different stages of development and, where appropriate, regulatory review.
Adults with PKU
The Phase 1b trial described by Agios is evaluating AG-181 in adults living with PKU.
Data expected in 2026
Agios has indicated that initial Phase 1b data are expected during the second half of 2026.
More evidence will be needed
Additional research would be required before AG-181 could be considered for regulatory approval or routine clinical use.
CanPKU+ recognizes the importance of continued research into treatment options that may respond to the different needs, preferences and circumstances of people living with PKU.
Other developments reported by Agios
The quarterly announcement included updates across Agios' commercial products and rare hematology research pipeline. These included:
- Worldwide second-quarter net revenue of US$44.7 million from mitapivat, marketed under the names PYRUKYND® and AQVESME™.
- Continued U.S. commercial activity for AQVESME in thalassemia, with 442 cumulative prescriptions reported as of June 30, 2026.
- U.S. Food and Drug Administration Priority Review of a supplemental application for mitapivat in sickle cell disease, with a target decision date of November 1, 2026.
- Plans to advance AG-236 into Phase 2/3 development for polycythemia vera.
- Licensing of cevidoplenib for potential development in immune thrombocytopenia.
- Decisions not to continue development of tebapivat in lower-risk myelodysplastic syndromes or sickle cell disease.
These broader business and pipeline announcements provide context for the company's research priorities but are separate from the AG-181 clinical program in PKU.
What happens next?
The next publicly identified milestone for the AG-181 program is the release of Phase 1b trial data, which Agios currently expects during the second half of 2026.
When results become available, important areas to examine will include:
- the number and characteristics of trial participants;
- reported side effects and overall tolerability;
- how AG-181 behaved in participants' bodies;
- whether changes in blood phenylalanine were observed;
- which PAH variants may potentially respond; and
- the company's plans for any future stages of research.
CanPKU+ will continue following the AG-181 program and will share relevant, publicly available information as the research develops.
Read the original announcement
This article is based on the Agios Pharmaceuticals news release: Agios Reports Second Quarter 2026 Financial Results and Provides Business Update, published July 30, 2026.
