Agios Expands Rare-Disease Pipeline With New Phase 1b PKU Study of AG-181

Agios Pharmaceuticals (AGIO) announced an update on their ongoing clinical study.

Study Overview

Agios Pharmaceuticals is launching a Phase 1b trial titled “A Phase 1b, Open-label, Multicenter, Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics Study of AG-181 in Subjects With Phenylketonuria.” The main goal is to see how safe and tolerable AG-181 is for people with phenylketonuria (PKU), a rare inherited disorder that limits how the body breaks down the amino acid phenylalanine. For investors, this early-stage study matters because it tests a new asset in Agios’ pipeline outside its core blood-disorder focus, opening a potential new rare-disease revenue stream if the program progresses.

Intervention/Treatment

The study tests AG-181, an oral film-coated tablet. It is designed to help manage PKU by changing how the body handles phenylalanine, with the goal of improving control of the disorder and easing the treatment burden. All participants in the trial will receive AG-181, which allows the company to closely track how the drug behaves and how patients respond.

Study Design

This is an interventional study, which means participants are given an active treatment rather than just being observed. The trial is non-randomized and uses a sequential design: small groups (cohorts) are treated one after another, so safety and dosing can be adjusted over time. There is no masking or placebo group; both doctors and patients know they are receiving AG-181. The main purpose is treatment-focused, aimed at understanding safety and early signals of benefit rather than proving full effectiveness at this stage.

Study Timeline

The study was first submitted on November 17, 2025, signaling Agios’ formal regulatory step to begin clinical work with AG-181 in PKU. The trial is currently listed as “Not Yet Recruiting,” so enrollment has not started. The most recent update was filed on January 28, 2026, which suggests ongoing planning, regulatory interactions, or protocol refinements ahead of first patient dosing. Primary completion and overall completion dates are not yet posted; once available, those milestones will guide investors on when to expect initial safety and drug-exposure data, and later, a full readout.

Market Implications

This update reinforces Agios’ push into rare metabolic diseases, an area that often supports premium pricing and long-duration revenue when drugs succeed. While a Phase 1b trial is early and carries high risk, simply moving AG-181 toward first-in-patient testing may support the pipeline value story, especially if investors see it as diversification beyond Agios’ existing hematology portfolio. In the PKU space, BioMarin and others already market or develop treatments, so any positive signs from AG-181 could position Agios as a future competitor in a concentrated but high-value niche. In the near term, traders should expect limited direct stock impact from this single update, but successful enrollment and clean safety data could gradually lift sentiment around Agios’ long-term growth options. The study is currently ongoing in the setup phase, with further operational and scientific details available on the ClinicalTrials portal.

To learn more about AGIO’s potential, visit the Agios Pharmaceuticals drug pipeline page.