Algernon Reports 93% Cough Suppression with Ifenprodil

VANCOUVER, British Columbia, July 16, 2024 - Algernon Pharmaceuticals Inc., a clinical stage pharmaceutical development company, has announced promising results for ifenprodil in a recent study. Conducted by Seyltx, Inc., the multi-dose study reported a 93% reduction in median cough count in an acute guinea pig citric acid challenge. Seyltx, a US-based drug development company, acquired Algernon’s ifenprodil research program for $2 million USD and a 20% equity share.

The study aimed to determine the appropriate dose for Seyltx’s upcoming Phase 2b human study, named SILINDA, focusing on refractory chronic cough (RCC). Patient enrollment is anticipated to commence in early 2025. Ifenprodil, an NMDA receptor antagonist targeting the NR2B subunit, interrupts glutamate signalling. This mechanism suppresses the urge to cough by interfering with central brain signalling, making ifenprodil a promising candidate for chronic cough treatment.

The animal study involved doses of 1, 3, 10, and 30 mg/kg, showing a clear dose-dependent response with significant results below the no observed adverse effect level (NOAEL) dose. Full results will be shared at the London International Cough Symposium on July 18-19, 2024.

Previous trials by Algernon showed that ifenprodil, administered at 20 mg three times daily, reduced cough by approximately 40% in patients with idiopathic pulmonary fibrosis. Dietrich A. Stephan, Ph.D., CEO of Seyltx, remarked that the pre-clinical study, combined with human Phase 2a data, validates the target’s central role in chronic cough and informs the dosing regimen for the Phase 2b trial.

Brendan Canning, Ph.D., a professor at Johns Hopkins University and member of Seyltx’s Scientific Advisory Board, emphasized the significance of achieving cough suppression below the NOAEL dose without affecting overall respiration. This enhances confidence in ifenprodil’s potential as a top-tier treatment for RCC.

Jacky Smith, MB, ChB, FRCP, Ph.D., a professor at the University of Manchester and a member of Seyltx’s Scientific Advisory Board, highlighted plans to incorporate recent learnings to maximize the SILINDA trial’s success. Given the robust effect sizes and broad patient applicability, ifenprodil could benefit millions suffering from this difficult-to-treat condition.

The SILINDA Phase 2b study, structured based on U.S. FDA feedback, will include three dose arms and a placebo arm, evaluating the efficacy, safety, and tolerability of ifenprodil in roughly 240 adults with RCC. This randomized, placebo-controlled, parallel-arm trial will feature treatment arms of 40 mg, 80 mg, and 120 mg, all administered three times daily, and a placebo group. The primary endpoint is the 24-hour cough frequency at 12 weeks, assessed using the VitaloJAK® cough monitoring system.

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 the SILINDA study are expected by the end of 2026.

Algernon Pharmaceuticals Inc., a Canadian clinical stage drug development company, is investigating multiple drugs for unmet medical needs globally. Its subsidiary, Algernon NeuroScience, is advancing a psychedelic program for stroke and traumatic brain injury and has an active research initiative for chronic kidney disease. Algernon recently finalized its agreement with Seyltx Inc. for the acquisition of its ifenprodil research program, securing $2 million USD and a 20% equity stake in Seyltx.