UK Authorizes Clinical Trial for PX578
The drug aims to treat POLG-mediated mitochondrial disorders by activating the polymerase enzyme to restore DNA levels.
Updated on Oct. 31, 2026 in Biotech
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The UK Medicines and Healthcare products Regulatory Agency has authorized the clinical trial application for PX578. This experimental small molecule, designed to treat POLG-mediated primary mitochondrial disorders, is currently in the research-stage of clinical development.
Why it matters
PX578 is being developed as a first-in-class small molecule activator to address the lack of disease-modifying therapies for progressive POLG mutations. By targeting mitochondrial DNA replication, the treatment aims to restore cellular function in patients who currently have no approved clinical options.
PX578 functions as a small molecule activator of the mitochondrial polymerase POLG, an enzyme required for DNA replication. This mechanism aims to increase mitochondrial DNA levels to overcome the deficiencies caused by genetic mutations.
The players
Pretzel Therapeutics
A biotechnology company focused on developing small molecule therapies to restore mitochondrial function and treat primary mitochondrial diseases.
Medicines and Healthcare products Regulatory Agency
The United Kingdom's executive agency responsible for ensuring that medicines and medical devices meet safety and efficacy standards.
US Food and Drug Administration
The United States federal agency responsible for regulating pharmaceuticals, which previously cleared the clinical trial application for PX578.
The details
POLG disease is a progressive disorder caused by mutations in the POLG gene that result in mitochondrial dysfunction. PX578 acts by directly activating the polymerase to drive replication, theoretically restoring energy production in affected cells. The upcoming POLARIS study is a randomized, double-blind, placebo-controlled phase 2 trial intended to measure these therapeutic effects in patients.
Timeline
August 2026: FDA cleared the Investigational New Drug application for PX578.
September 2026: FDA granted Fast Track Designation to the program.
October 31, 2026: UK Medicines and Healthcare products Regulatory Agency authorized the clinical trial application.
End of 2026: Planned initiation of the phase 2 POLARIS study.
The Tech Race
The development of PX578 places Pretzel Therapeutics at the front of the effort to provide the first disease-modifying treatment for POLG-mediated mitochondrial disorders. This work follows years of focus on managing symptoms, as there are currently no approved therapies for the underlying genetic mechanism.
This authorization enables the start of clinical research in the UK, moving PX578 closer to potential human testing alongside its existing FDA clearance. Patients and caregivers should monitor the trial status as researchers begin the process of recruiting for the phase 2 POLARIS study.
The takeaway
The initiation of the phase 2 POLARIS trial marks a critical milestone for patients living with progressive POLG mutations. Interested observers should monitor clinical trial registries for patient eligibility criteria and enrollment updates as the 2026 study launch approaches.
What happens next
Pretzel Therapeutics expects to begin the phase 2 POLARIS study for POLG disease by the end of 2026.
Further reading
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Source note: This article includes information reported by Pharmabiz.
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