BVF Partners L.P. Acquires Shares of Xenon Pharmaceuticals Inc.

SAN FRANCISCO, CALIFORNIA--(Marketwired - Sept. 9, 2016) - BVF Partners L.P. ("Partners") announced that on September 8, 2016, certain affiliates of Partners acquired Common Shares (the "Common Shares") of Xenon Pharmaceuticals Inc. ("Xenon"), a Burnaby, British Columbia-based company, in a public offering (collectively, the "Transactions").

Following these Transactions, the holdings of the various affiliates are as follows: Biotechnology Value Fund, L.P. ("BVF"), ownership of 1,352,312 Common Shares representing approximately 7.8% of the issued and outstanding Common Shares (from Common Shares representing approximately 5.4% of the then issued and outstanding Common Shares prior to the Transaction); Biotechnology Value Fund II, L.P. ("BVF2"), ownership of 883,470 Common Shares representing approximately 5.1% of the issued and outstanding Common Shares (from Common Shares representing approximately 3.5% of the then issued and outstanding Common Shares prior to the Transaction); Biotechnology Trading Fund OS LP ("Trading Fund OS"), ownership of 262,664 Common Shares representing approximately 1.5% of the issued and outstanding Common Shares (from Common Shares representing approximately 1.1% of the then issued and outstanding Common Shares prior to the Transaction); Investment10 LLC ("ILL10"), ownership of 190,509 Common Shares representing approximately 1.1% of the issued and outstanding Common Shares (from Common Shares representing approximately 0.9% of the then issued and outstanding Common Shares prior to the Transaction); MSI BVF SPV, L.L.C. ("MSI"), ownership of 419,950 Common Shares representing approximately 2.4% of the issued and outstanding Common Shares (from Common Shares representing approximately 1.7% of the then issued and outstanding Common Shares prior to the Transaction).

Partners, as the general partner of BVF and BVF2, the investment manager of MSI and ILL10, and the sole member of BVF Partners OS, Ltd., which is itself the general partner of Trading Fund OS, may be considered to have the power to exercise control or direction over the Common Shares beneficially owned in the aggregate by BVF, BVF2, Trading Fund OS, ILL10 and MSI.

Partners has purchased shares from the Issuer for investment purposes, and in the future may further purchase, hold, vote, trade, dispose or otherwise deal in the common shares of the Issuer in such manner as they deem advisable to benefit from changes in market prices of such common shares, publically disclosed changes in the operations of the Issuer, its business strategy or prospects or from a sale or merger of the Issuer.

Partners is located at 1 Sansome Street, 30^th Floor, San Francisco, California 94104. Xenon's head office is located at 200-3650 Gilmore Way, Burnaby, British Columbia V5G 4W8.