FDA Review of Sibnayal Offers Hope for Rare Kidney Disease Patients

PARIS, France – January 19, 2026

French pharmaceutical company Advicenne has announced a significant milestone in its effort to bring a new treatment to Americans suffering from a rare kidney disorder. The U.S. Food and Drug Administration (FDA) has accepted for review the company's New Drug Application (NDA) for Sibnayal®, a therapy designed specifically for distal Renal Tubular Acidosis (dRTA). The acceptance moves the drug into a substantive review phase, with the FDA setting a target action date of September 3, 2026.

This development marks a crucial step toward potentially introducing the first and only FDA-approved therapy for dRTA in the United States, a market where an estimated 20,000 patients currently rely on off-label and often burdensome treatments. The drug, a fixed-dose combination of potassium citrate and potassium bicarbonate, is already approved for use in the European Union and Great Britain, and its arrival on American shores is now a tangible possibility.

The Unseen Struggle of Distal Renal Tubular Acidosis

Distal Renal Tubular Acidosis is a serious condition in which the kidneys are unable to properly excrete acid from the body into the urine. This failure leads to an accumulation of acid in the blood, a state known as metabolic acidosis. While rare, dRTA has profound and lifelong consequences for patients.

The chronic acid imbalance disrupts the body's delicate chemistry, leading to a cascade of debilitating symptoms. Patients often suffer from low blood potassium (hypokalemia), which can cause severe muscle weakness, pain, and even paralysis. The body's attempt to buffer the acid by leaching calcium from bones results in rickets in children and osteomalacia or osteopenia (soft or brittle bones) in adults. Furthermore, the altered urine chemistry frequently leads to the formation of painful kidney stones and calcium deposits within the kidneys, known as nephrocalcinosis, which can impair renal function over time.

For children, the disease is particularly devastating, often causing stunted growth and a failure to thrive. The current standard of care in the United States involves managing the symptoms with generic alkalizing agents like sodium bicarbonate or potassium citrate. However, these treatments are not specifically approved for dRTA and present significant challenges. They are typically short-acting, requiring multiple doses throughout the day and night, and are often unpalatable, leading to major issues with patient adherence, especially among pediatric patients.

A Tailor-Made Solution

Sibnayal® was developed to directly address the shortcomings of current dRTA management. It is formulated as prolonged-release granules, designed to provide a steady therapeutic effect over a 12-hour period. This allows for a more convenient twice-daily dosing schedule, a significant improvement that could dramatically enhance patient compliance and quality of life.

The therapy's efficacy is supported by robust clinical data from European studies, which formed the basis of its successful marketing authorization across the Atlantic. The pivotal Phase III study (B21CS) and its 24-month open-label extension (B22CS) demonstrated that Sibnayal® effectively normalized blood bicarbonate levels in the vast majority of patients, correcting the underlying metabolic acidosis. Furthermore, blood potassium levels were restored to normal in over 80% of study participants. The treatment was well-tolerated, with most side effects being mild gastrointestinal discomfort, and no patients discontinued the therapy due to adverse events.

Critically, the studies also reported high rates of patient satisfaction and treatment adherence, with an average quality of life improvement of 89% noted after two years. If approved, Sibnayal® would transition dRTA care from a regimen of off-label, frequently dosed compounds to a precisely formulated, evidence-backed, and specifically indicated prescription medicine.

Navigating the Path to U.S. Approval

Advicenne is pursuing U.S. approval through the FDA's 505(b)(2) regulatory pathway. This streamlined process allows a drug developer to include data from studies not conducted by the applicant, such as published literature or, in this case, the FDA's previous findings on the active ingredients and Advicenne's own extensive European clinical trial data. This pathway is particularly vital for rare disease therapies, as it can reduce the need for duplicative, large-scale clinical trials, thereby accelerating development and reducing costs.

The company's successful submission on November 2, 2025, was followed by a 60-day filing review period, during which it satisfactorily addressed initial questions from the agency. This paved the way for the formal acceptance of the NDA.

Didier Laurens, Chief Executive Officer of Advicenne, commented on the milestone in a press release. “This acceptance acknowledges the outstanding work accomplished by the entire Advicenne team, across clinical, regulatory, and CMC functions, both in France and the United States,” he stated. “It attests to the quality of our submission, which, I would like to emphasize, was filed precisely on schedule. We are now entering the substantive review phase, which is expected to continue through September 2026. During this time, we will remain fully committed to responding promptly and effectively to all FDA requests.”

A European Biotech's American Ambition

For Advicenne, a specialty pharmaceutical company founded in 2007 with a focus on rare kidney diseases, the potential entry into the U.S. market represents a transformative step. Securing FDA approval for its lead product would not only provide a major new revenue stream but also validate its clinical and regulatory strategy on a global stage, solidifying its position as a key player in the nephrology space.

The company's work extends beyond dRTA, with late-stage development programs for Sibnayal® in treating cystinuria—another rare genetic kidney disease—underway in Europe, the U.S., and Canada. This focused pipeline underscores a deep commitment to addressing unmet needs in a patient population that has long been underserved.

As the FDA embarks on its comprehensive review, patients, families, and clinicians in the dRTA community are watching with anticipation. The prospect of a dedicated, convenient, and effective therapy offers a new horizon of hope for managing this challenging chronic illness, promising a future with better health outcomes and an improved quality of life for thousands.