BLU-5937 is a potent, highly selective, orally bioavailable small molecule antagonist of the P2X3 receptor, a clinically validated target for chronic cough. BLU-5937 has the potential to be a best-in-class therapeutic for chronic cough patients who do not respond to current therapies.

BELLUS Health announced in September 2017 that BLU-5937 has shown a significant reduction in cough and no taste disturbance in two separate preclinical models. In a guinea pig cough model, BLU-5937 has shown comparable efficacy to the current leading P2X3 antagonist, Merck & Co’s Gefapixant (also named AF-219 or MK-7264). In a rat taste model, BLU-5937 did not inhibit taste; however, consistent with clinical trial data previously presented by Merck & Co, Gefapixant led to significant taste disturbance. Refer to Preclinical Study Results section below for details.

The Company is currently performing preclinical studies on BLU-5937 to complete its package for submission of a Clinical Trial Application (CTA), expected in the second quarter of 2018. The Company plans to initiate a Phase 1 clinical study in the third quarter of 2018.

Rights to BLU-5937 were obtained under a license agreement with the NEOMED Institute in February 2017. The P2X3 antagonist program was initiated by AstraZeneca scientists in Montreal, and assigned to NEOMED in October 2012. BLU-5937 was selected as a drug candidate to advance towards the clinic based on comprehensive structure-activity relationship testing at AstraZeneca and extensive preclinical development efforts in chronic cough undertaken by NEOMED.

Preclinical Study Results

BLU-5937’s Reduction in Cough Frequency Comparable to the Leading P2X3 Antagonist, Gefapixant

The anti-tussive effect of BLU-5937 was compared to that of Gefapixant in a guinea pig cough model.  Treatments (control, BLU-5937 (0.3, 3 and 30 mg/kg) or Gefapixant (0.3, 3 or 30 mg/kg)) were administered orally in seven groups of 6 animals 2 hours prior to tussive agent exposure (citric acid and histamine) and the number of coughs were counted for a period of 15 minutes. Both treatments showed comparable dose-dependent reduction in cough frequency as compared to the control. The reduction in cough was statistically significant at 3 mg/kg (39% vs. control) and 30 mg/kg (52% vs. control) with BLU-5937, and at 30 mg/kg (45% vs. control) with Gefapixant.

BLU-5937’s Duration of Effect also Comparable to Gefapixant

Using the same guinea pig cough model, a time course study was conducted to assess the duration of the anti-tussive effect of BLU-5937 and Gefapixant following the administration of a single oral 30 mg/kg dose. In this study, animals in groups of 6 were exposed to tussive agents (citric acid and histamine) at various times after the administration of the study drugs (2, 4, 6, 8 and 12 hours post-dose for BLU-5937 and 2 and 8 hours post-dose for Gefapixant) and the number of coughs were measured for 15 minutes. The reduction in cough frequency compared to control was shown to be statistically significant at 2, 4 and 6 hours post-dose with BLU-5937, and at 2 hours post-dose with Gefapixant. The anti-tussive effect was no longer significant at 8 hours post-dose for both agents. These results indicate that BLU-5937 and Gefapexiant have comparable duration of effect.

BLU-5937 Shows No Impact on Taste, Leading P2X3 Antagonist Gefapixant Shows Significant Taste Disturbance in the Rat Taste Model

A rat taste model was used to compare BLU-5937’s effect on taste function with that of Gefapixant. Animals were water-fasted overnight and presented with one bottle of water and one bottle of (bitter-tasting) quinine at the time corresponding to the maximum plasma concentration of study drugs; and the volume of liquid consumed from each bottle was measured for 15 minutes. Treatments (control, BLU-5937 (10 or 20 mg/kg) or Gefapixant (10 or 20 mg/kg)) were administered intraperitoneally in two groups of 10 rats. Animals treated with BLU-5937 did not drink more quinine than the control animals, while those treated with Gefapixant drank significantly (approximately 5 times) more quinine than the control at the two doses tested. These results indicate that Gefapixant altered taste function, while BLU-5937 did not.

Disease and Market

Chronic cough is associated with significant adverse social, psychosocial and physical effects on quality of life. Chronic cough, defined as a cough that lasts more than eight weeks, is estimated to affect approximately 10% of adults in the U.S. While an underlying etiology may contribute to cough in some of these patients, including gastro-oesophageal reflux, asthma, or allergic rhinitis, an underlying condition cannot be identified in 10%-20% of chronic cough patients (unexplained chronic cough). A portion of patients with an underlying condition as well as the large majority of unexplained chronic cough patients are not well controlled by current therapies.

In June 2017, the Company commissioned Torreya Insights LLC to conduct a market assessment through an evaluation of chronic cough epidemiology and pricing estimates. Based on primary and secondary research, the report concludes that, in the United States alone, more than 26 million adults suffer from chronic cough and more than 2.6 million of these patients have chronic cough lasting for more than a year. The number of treatment-refractory chronic cough patients expands to 11.7 million when taking into account those patients with a cough duration between eight weeks and one year. The market assessment also sought to better understand the pricing and reimbursement landscape for a condition that has no recently-approved therapies, and therefore no direct comparables. Based on interviews with Key Opinion Leaders, prescribing physicians and payers, the consensus is that new chronic cough treatments, such as BLU-5937, will be priced similarly to therapies for chronic constipation, asthma and partial onset seizures. These analogs represent non-lethal chronic conditions that have a significant impact on quality of life and address a large patient population in competitive markets that also include generic and over-the-counter products. The monthly price for these analogs varies between US $300 and $600.

In April 2017, the Company announced that the U.S. Patent and Trademark Office issued U.S. Patent No. 9,598,409, which grants claims covering the composition of matter of BELLUS’ Health lead drug candidate, BLU-5937, and related imidazopyridine compounds, in addition to pharmaceutical compositions comprising BLU-5937 and uses thereof. The patent has an expiration date of 2034, excluding any potential patent term extension. The Company was granted a patent for similarly broad claims in China on July 10, 2017. Similar patent applications are currently pending in Europe, Japan and other industrialized nations.

Pathophysiology of Chronic Cough

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