Thryv's Heart Drug Gets FDA Fast Track, Enters Pivotal Trial

SAN FRANCISCO, CA – April 22, 2026 – Thryv Therapeutics announced today a pair of significant advancements for its investigational drug, THRV-1268, offering a new wave of hope for individuals with Long QT Syndrome (LQTS), a dangerous inherited heart rhythm disorder. The biotechnology company has commenced patient dosing in a pivotal Phase 2/3 clinical trial and has received Fast Track Designation from the U.S. Food and Drug Administration (FDA), signaling a potentially accelerated path for a therapy that aims to be the first to treat the underlying cause of the disease.

These milestones mark a critical step forward in the fight against a condition that can lead to fainting, seizures, and sudden cardiac death. The Wave II study, now underway at leading arrhythmia centers across the United States, will evaluate THRV-1268 in patients with genetically confirmed Long QT Syndrome Type 2 (LQT2), one of the most common forms of the disorder.

A New Horizon for a Life-Threatening Condition

Long QT Syndrome is a disorder of the heart's electrical system, affecting an estimated one in every 2,500 people. The condition is characterized by a prolonged QT interval on an electrocardiogram, which signifies a delay in the heart's ability to electrically reset itself between beats. This delay creates a window of vulnerability for chaotic and dangerously fast heart rhythms, known as Torsades de Pointes, which can be fatal.

For decades, the standard of care has focused on managing risk rather than correcting the root problem. Patients are often prescribed beta-blockers to prevent adrenaline-triggered arrhythmias and may require lifestyle changes, such as avoiding certain medications and strenuous activities. For those at high risk, an implantable cardioverter-defibrillator (ICD) may be surgically placed to shock the heart back into a normal rhythm if a life-threatening event occurs. While these measures have saved lives, they do not cure the disease and come with their own set of challenges and side effects.

Thryv's THRV-1268 represents a fundamentally different approach. As a potential disease-modifying therapy, it is designed to target the biological mechanism that causes the QT interval prolongation in the first place.

"The emerging clinical evidence for SGK1's role in cardiac electrophysiology gives me hope that we may finally have a new approach to Long QT Syndrome that addresses the underlying QT interval prolongation," said Vasanth Vedantham, MD, PhD, a Professor of Medicine and Cardiac Electrophysiologist at UCSF Health, who initiated the first patient in the Wave II study. "Patients and their families carry an enormous burden – not just the medical complexity of managing arrhythmic risk, but the emotional weight of living with a condition that remains life-threatening despite current therapies."

The Science of SGK1 Inhibition

THRV-1268 is part of a new class of drugs known as SGK1 inhibitors. SGK1, or serum glucocorticoid inducible kinase 1, is a protein that has been identified as a key regulator of cardiac ion channels - the tiny pores in heart cells that control the flow of electrical signals. In certain genetic contexts, like LQTS, overactive SGK1 signaling can disrupt this delicate electrical balance, leading to the prolonged repolarization seen in the disorder.

Thryv's precision medicine strategy is to inhibit SGK1, thereby normalizing ion channel function and shortening the dangerously long QT interval. This approach has shown promise across different LQTS subtypes. While the current Wave II trial focuses on LQT2, caused by mutations in a potassium channel gene, the FDA's Fast Track Designation also covers LQTS Type 3 (LQT3), which stems from a defect in a sodium channel. This suggests the drug's mechanism may have broad utility.

This confidence is built on a foundation of encouraging data. A previous Phase 1 study of THRV-1268 in healthy participants demonstrated that the drug was well-tolerated and, crucially, produced a measurable shortening of the QT interval, confirming its ability to engage its target in humans.

Navigating the Fast Track to Approval

The initiation of the Wave II study is a major step in the drug's clinical development. The multicenter, Phase 2/3 trial will assess the safety and efficacy of two different doses of THRV-1268 over a 12-week period. The primary goal is to measure the change in the corrected QT interval (QTcF). Initially, participants will receive the drug as an oral suspension, a formulation choice intended to accelerate data collection that could support a future pediatric version.

The FDA's decision to grant Fast Track Designation is a significant validation of the drug's potential. This status is reserved for investigational therapies that treat serious conditions and fill an unmet medical need. It allows for more frequent communication with the FDA, the potential for a "Rolling Review" where the company can submit parts of its application as they are completed, and eligibility for Priority Review and Accelerated Approval.

"Fast Track Designation represents a meaningful regulatory milestone that reflects the serious and underserved nature of genetically defined Long QT Syndrome," said Amy Sehnert, MD, FACC, Chief Medical Officer of Thryv Therapeutics. "This recognition by the FDA reinforces our confidence in THRV-1268 and its potential to become the first disease-modifying therapy to specifically target the underlying disease biology of Long QT Syndrome."

For Thryv, a privately held company backed by investors including Amplitude Ventures and Lumira Ventures, these developments are crucial. Positive clinical results combined with an expedited regulatory pathway could dramatically increase the value of its lead asset and attract further investment or partnership opportunities. The company is also exploring THRV-1268 for other cardiac conditions, including heart failure and atrial fibrillation, positioning SGK1 inhibition as a potential platform technology for a range of cardiovascular diseases. With initial data from the Wave II study anticipated in the fourth quarter of 2026, the medical community and patient families will be watching closely.