Zymeworks

expected to close in 2H 2026, adding durable commercial cash flows and expanding Zymeworks' diversified revenue base Continued advancement of R D pipeline across wholly-owned and partnered programs Repurchased $49.4 million of common shares as of August 4, 2026 under the newly authorized 2026 share repurchase program Strong balance sheet with $322.5 million in cash, cash equivalents and marketable securities as of June 30, 2026 Vancouver, British Columbia (August 6, 2026) Zymeworks Inc.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

These diverse royalty and milestone cash flows improve our ability to sustain long-term investment in our wholly-owned R D pipeline, pursue additional strategic acquisitions and partnerships, and continue returning capital to shareholders through our share repurchase program.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

Maintaining Financial Flexibility Cash Resources Zymeworks reported $322.5 million in cash, cash equivalents and marketable securities as of June 30, 2026 Share Repurchase Program In May 2026, the Board of Directors authorized a 2026 share repurchase program under which the Company may repurchase up to $125.0 million of its outstanding common stock, par value $0.00001 per share.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

As of August 4, 2026, the Company has utilized approximately $49.4 million of this current approved repurchase program to acquire 1,971,454 shares at an average price of $25.04 per share (exclusive of commission expense and estimated excise tax).

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

Since initiating its share repurchase program in August 2024, the Company has cumulatively utilized $213.6 million to reacquire 10,571,316 shares at an average price of $20.21 per share (exclusive of commission expense and estimated excise tax).

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

, Europe, Japan, and China, and assuming the full execution of the $125.0 million share repurchase program, to fund Zymeworks planned operations beyond 2028 based on current operating plans expected financial performance and future financial position, including anticipated adjusted gross operating expense (non-GAAP), adjusted research and development expense (non-GAAP) and adjusted general and administrative expense (non-GAAP) for the three-year period ending December 31, 2028, excluding any potential acquisition-related expenses or new partnerships and collaborations and other information that is not historical information.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

These diverse royalty and milestone cash flows improve our ability to sustain long-term investment in our wholly-owned R D pipeline, pursue additional strategic acquisitions and partnerships, and continue returning capital to shareholders through our share repurchase program.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

Leveraging Partnerships and External Innovation The Company is advancing strategic initiatives to maximize the value of its proprietary Pan-RAS antibody-drug conjugate (ADC) platform, including evaluating the formation of a separate, dedicated entity with third-party capital participation.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

The Company has engaged MTS Healthcare to evaluate strategic partnering opportunities to fund further development for ZW191 with the objective of maximizing long-term value.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

The Company continues its evaluation of additional business development opportunities consistent with its capital allocation strategy.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

Consistent with this evolution, the Company no longer intends to provide cash runway guidance, and expects to increasingly focus on providing guidance on operating performance and long-term growth.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

The above assumptions, risks and uncertainties are not exhaustive.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026

A reconciliation of anticipated adjusted gross operating expense, adjusted research and development expense, and adjusted general and administrative expense to the most directly comparable GAAP measures is not available without unreasonable effort due to the uncertainty of expenses that may be incurred in the future, and we are also unable to predict the probable significance of such adjusted measures.

SEC original ↗Zymeworks — Earnings release (8-K exhibit)EX-99Aug 6, 2026