Canada's drug price watchdog has ordered Alexion Pharmaceuticals to lower the price of Soliris, one of the world's most expensive drugs.

In a decision released Wednesday, the Patented Medicine Prices Review Board ruled that the price of Soliris (eculizumab) is excessive.

The panel has also ordered Alexion to pay Ottawa back for overcharging Canadians for the drug. The amount of that excess revenue has not been disclosed.

The drug treats two rare diseases where the body's immune system attacks and destroys red blood cells. In Canada, Soliris can cost about $700,000 per patient per year, depending on the weight of the patient.

The <a href="https://twitter.com/PMPRB_CEPMB">@PMPRB_CEPMB</a> Hearing Panel has issued its decision on the matter relating to Soliris <a href="https://t.co/j5n1nAFTR7">https://t.co/j5n1nAFTR7</a> <a href="https://twitter.com/hashtag/cdnhealth?src=hash">#cdnhealth</a> —@PMPRB_CEPMB

In a statement to CBC News, Alexion said "we strongly disagree with the PMPRB panel's decision and we will be seeking immediate judicial review."