Concurrently, Zymeworks has terminated its existing 2025 share repurchase program under which the Company has repurchased 4,197,553 million shares of common stock for $102.3 million, representing an average purchase price of $24.36 per common share.

"The authorization of this 2026 share repurchase program reflects our continued focus on disciplined capital allocation and long-term value creation," said Kenneth Galbraith, Chair and Chief Executive Officer of Zymeworks. "We believe this program provides an efficient mechanism to return capital to stockholders, while preserving the flexibility to further invest in our R&D pipeline and pursue strategic opportunities."

As of May 13, 2026, the Company had approximately 73.0 million outstanding common shares.

The program will be funded through the Company's strong balance sheet, leveraging its financial capacity to repurchase shares. The shares may be repurchased from time to time in open market transactions, or other means in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and Rule 10b-18 of the Exchange Act. The timing, number of shares repurchased, and prices paid for the shares under this program will depend on general business and market conditions as well as corporate and regulatory limitations, prevailing stock prices, and other considerations. The 2026 share repurchase program may be suspended or discontinued at any time and does not obligate the Company to acquire any amount of common stock.***