Quince Therapeutics Inc. (NASDAQ: QNCX) experienced a dramatic drop in share value, registering almost a 90% decline on Thursday following the announcement of topline data from its Phase 3 NEAT clinical study. This pivotal trial was designed to evaluate the efficacy and safety of the company’s lead investigational therapy, dexamethasone sodium phosphate encapsulated in autologous erythrocytes (referred to as eDSP), targeting Ataxia-Telangiectasia (A-T), a rare inherited neurodegenerative condition.
Ataxia-Telangiectasia is characterized by mutations in the ATM gene, leading to progressive motor coordination impairment (ataxia), noticeable small blood vessels in the skin and eyes (telangiectasias), immunodeficiency, and a heightened susceptibility to malignancies. This debilitating disorder poses significant challenges in management due to its complex symptomatology and progression.
The NEAT study enrolled a total of 105 participants, segmented into two cohorts: 83 children aged between six and nine years constituting the primary analysis group, and 22 participants aged ten years or older. The trial's primary efficacy endpoint was the change from baseline to the final efficacy assessment at six months, measured by the Rescored modified International Cooperative Ataxia Rating Scale (RmICARS). This scale is widely utilized to evaluate disease progression in ataxia disorders.
Results indicated a mean change score of 0.94 in the treatment arm compared to 2.24 in the placebo group, resulting in a difference of −1.30; however, this did not reach statistical significance, evidenced by a p-value of 0.0851. Likewise, the key secondary endpoint—a measure of change in severity from baseline through six months as assessed by the Clinical Global Impression of Severity (CGI-S)—also failed to achieve significance, with a p-value of 0.522.
From a safety perspective, eDSP was generally well tolerated among participants. No notable safety concerns emerged during the trial, and common adverse events in the treatment cohort included pruritus (itching) and pyrexia (fever), which were manageable and did not lead to discontinuation.
An additional presentation was made concerning long-term safety data, previously reported, involving children undergoing extended eDSP treatment for A-T. This data was showcased at the British Paediatric Neurology Association 2026, illustrating that long-term eDSP administration was associated with stable growth and metabolic outcomes without detectable corticosteroid-related toxicity. Metrics such as height and weight z-scores remained stable, and importantly, patients did not exhibit corticosteroid-induced linear growth suppression or weight gain—issues commonly seen in A-T progression.
Moreover, no disruptions in glucose metabolism or adrenal function were identified. There were no confirmed cases of adrenal insufficiency; nonetheless, continued routine monitoring remains advisable to preempt any potential complications.
Despite these encouraging safety profiles, the failure to meet efficacy targets raises substantial questions about the future prospects of eDSP as a treatment for Ataxia-Telangiectasia. Following the announcement, Quince Therapeutics' stock price plummeted to $0.26 in the premarket session on Friday, representing a 2.22% drop at the time of last report.
The rapid market movement underscores the volatility surrounding clinical-stage biopharmaceutical companies, especially those addressing rare genetic disorders. Investors reacted swiftly to the updated trial data, reflecting concerns over the therapeutic’s readiness for regulatory approval and commercial success.