BELLUS Health Announces the Launch of a Public Offering of Common Shares in Canada and the United States

The Supplement and the accompanying Base Prospectus contain important detailed information about the Offering. The Supplement and the accompanying Base Prospectus can be found on SEDAR at www.sedar.com and on EDGAR at www.sec.gov. Copies of the Supplement and accompanying Base Prospectus may also be obtained from the Company, by telephone at 450-­‐680-­‐4500 or by email at [email protected] or you may request them from: Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 2nd Floor, New York, NY 10022, by telephone at 877--821--7388 or by email at [email protected]; or Evercore Group L.L.C., Attention: Equity Capital Markets , 55 East 52nd Street, 35th Floor, New York, NY 10055, by telephone at 888-474-0200 or by email at [email protected]; or RBC Capital Markets, LLC, Attention: Equity Syndicate, 200 Vesey Street, 8th Floor, New York, New York 10281, by telephone at (877) 822-4089 or by email at [email protected]. Prospective investors should read the Supplement and accompanying Base Prospectus and the other documents the Company has filed before making an investment decision.