WALTHAM, Mass. — March 11, 2026
Pretzel Therapeutics announced new preclinical data for its lead therapeutic candidate PX578 during the MDA Clinical & Scientific Conference 2026 in Orlando, highlighting the compound’s potential to treat POLG Disease, a rare and often devastating mitochondrial disorder. The findings demonstrate that PX578 significantly increases mitochondrial DNA (mtDNA) levels while improving cellular respiration and energy production, reinforcing the therapy’s potential as a first-in-class disease-modifying treatment for mitochondrial DNA depletion syndromes (MDDS). The company also confirmed that the therapy is currently in Phase 1 clinical development, with plans to initiate a Phase 2 clinical study later in 2026.
Preclinical Results Demonstrate Improved Mitochondrial Function
The newly presented data highlight the bioenergetic restoration capabilities of PX578, a small-molecule activator of mitochondrial DNA polymerase (POLG) designed to address the underlying cause of mitochondrial DNA depletion disorders. Reduced mtDNA levels are widely recognized as a central driver of mitochondrial DNA depletion syndromes, which result from genetic mutations affecting mitochondrial DNA production and maintenance. By directly activating the mutant POLG enzyme, PX578 aims to restore mitochondrial function by increasing mtDNA levels within affected cells.
In preclinical studies spanning multiple in vitro and in vivo disease models, the therapy demonstrated a series of promising biological effects. Researchers observed increased mitochondrial DNA levels, enhanced cellular respiration, and improved cellular energy production, indicating that the compound effectively restores mitochondrial function at the cellular level. Additional results showed improved survival rates and enhanced liver health markers, suggesting that the therapy may offer systemic benefits for individuals affected by mitochondrial disorders.
Importantly, PX578 demonstrated activity across all tested POLG mutations, including the four most common mutations that together account for approximately 70 percent of POLG disease cases worldwide. This broad activity profile supports the possibility that the therapy could benefit a large proportion of patients affected by mitochondrial DNA depletion syndromes, which currently lack approved disease-modifying treatments.
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Clinical Development Progress and Upcoming Trials
Pretzel Therapeutics initiated a Phase 1 clinical study in healthy volunteers in 2025, marking the first step in translating PX578 from laboratory research to clinical application. According to company updates, the Phase 1 trial remains on track for completion during the first half of 2026, providing critical safety and pharmacokinetic data necessary for advancing the therapy to later-stage clinical testing.
Following completion of the Phase 1 study, Pretzel Therapeutics plans to begin a Phase 2 clinical trial during the second half of 2026, designed to evaluate the therapy in patients living with POLG disease. The upcoming trial will focus on generating robust pharmacokinetic and safety data alongside proof-of-concept clinical evidence, including evaluations of disease progression markers and patient-reported outcomes.
Scientists involved in the program believe the therapy’s unique mechanism of action targeting mitochondrial DNA polymerase represents a novel therapeutic strategy for treating rare mitochondrial diseases. Because mitochondrial dysfunction affects energy production in many tissues, restoring mitochondrial DNA levels could potentially improve muscle, neurological, and metabolic function in affected individuals.
Addressing a Major Unmet Need in Rare Mitochondrial Diseases
POLG disease is part of a broader category of primary mitochondrial disorders, which are characterized by defects in cellular energy production due to abnormalities in mitochondrial DNA maintenance. Patients with POLG disease often experience severe neurological symptoms, muscle weakness, liver dysfunction, and progressive organ damage, significantly impacting quality of life and survival. Despite decades of research, no approved disease-modifying therapies currently exist for this condition, leaving patients with limited treatment options focused mainly on symptom management.
The development of PX578 represents a potential breakthrough because it aims to directly address the root molecular cause of mitochondrial DNA depletion, rather than simply treating symptoms. By improving mitochondrial function and restoring cellular energy production, the therapy may offer a new therapeutic paradigm for mitochondrial disorders.
Pretzel Therapeutics continues to expand its pipeline focused on cellular energetics and mitochondrial biology, targeting diseases across neurological, metabolic, muscle, and rare disease categories. In addition to PX578, the company is also advancing programs targeting mitochondrial RNA polymerase and other mitochondrial regulatory pathways, reflecting growing scientific interest in mitochondrial biology as a frontier for therapeutic innovation.
As clinical development progresses, researchers and clinicians will closely monitor the results of upcoming studies to determine whether PX578 can deliver meaningful clinical benefits for individuals living with POLG disease and related mitochondrial conditions. If successful, the therapy could represent a major advancement in the treatment of mitochondrial DNA depletion syndromes, offering new hope for patients affected by these rare and life-threatening disorders.
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Source: Pretzel Therapeutics press release
