Algernon Pharmaceuticals Inc. reported that ifenprodil achieved a 93% (p = 0.036) reduction in median cough count in an acute guinea pig citric acid challenge study. The multi-dose study was conducted under the direction of Seyltx Inc. ("Seyltx"), a private US-based drug development company which recently acquired Algernon's ifenprodil research program for the purchase price of $2 million and a 20% equity position. The study was designed to inform dose selection in Seyltx's planned Phase 2b ifenprodil human study, recently named SILINDA, in refractory chronic cough ("RCC").

Seyltx has also announced that patient enrollment in the study is expected to begin in early 2025. Ifenprodil is an N-methyl-D-aspartate (NMDA) receptor antagonist specifically targeting the NR2B subunit, which prevents glutamate signalling. Ifenprodil represents a first-in-class potential treatment for chronic cough and interferes with central signalling in the brain, supressing the urge to cough.

The near-complete suppression of cough was observed in animals receiving a dose of 30 mg/kg, in a dose-dependent manner, below the no observed adverse effect level dose ("NOAEL"). Other dosing arms included 1, 3, and 10 mg/kg. A clear and statistically significant dose response was observed.

The full results of the study will be presented at the London International Cough Symposium July 18th - 19th, 2024. In an earlier Algernon Phase 2a clinical trial measuring cough in patients with idiopathic pulmonary fibrosis, ifenprodil, 20 mg TID (three times daily), reduced cough by ~40% from baseline (p = 0.001). In an earlier Algern on Phase 2a clinical trial measuring respiratory trial measuring cough in patients withidiopathic pulmonary fibrosis.

Ifenprodil, 20 u mg TID (three times daily), reduced cough by approximately 40% from baseline (p= 0.001). SILINDA Phase 2b Study Summary: Based on U.S. FDA feedback, Seyltx?s SILINDA program is currently structured to include three dose arms and a placebo arm, evaluating the efficacy, safety, and tolerability of ifenprodil in approximately 240 adults with RCC. SILINDA will be placebo-controlled, parallel-arm trial randomized 1:1:1:1 with expected treatment arms of 40 mg TID, 80 mg TID, 120 mg TID, and placebo.

The primary endpoint of 24-hour cough frequency will be measured at 12-weeks. The SILINDA Phase 2b program?s primary endpoint will be assessed using the VitaloJAK® cough monitoring system in a patient population that is not stratified for baseline 24-hour cough frequency given the uniform efficacy seen in the Phase 2a open label study across both low and high cough count patients. Key exploratory efficacy endpoints include the Cough Severity using Visual Analogue Scale (?CS-VAS?), the Leicester Cough Questionnaire (?LCQ?) and real-time longitudinal cough monitoring.

Topline data from SILINDA are expected at the end of 2026.