Zymeworks Inc. has 9 Schedule 13D or 13G filings on record since 2025-07-16. 4 holders' latest filing reports 5% or more of common stock, $0.00001 par value per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| EcoR1 Capital, LLC | 30.7% | 22,970,388 | SCHEDULE 13D/A, 2025-11-19 | 2025-11-16 |
| Rubric Capital Management LP | 9.49% | 7,000,000 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 |
| Perceptive Advisors LLC | 5.4% | 3,974,579 | SCHEDULE 13G, 2026-04-15 | 2026-04-08 |
| Bvf Partners L P | 5.2% | 3,938,641 | SCHEDULE 13G/A, 2025-11-14 | 2025-09-30 |
| Redmile Group, LLC | 4.9% | 3,705,750 | SCHEDULE 13G/A, 2025-11-14 | 2025-09-30 |
| BlackRock, Inc. | 4.8% | 3,559,828 | SCHEDULE 13G/A, 2025-07-16 | 2025-06-30 |
| Morgan Stanley | 3.4% | 2,519,243 | SCHEDULE 13G/A, 2026-02-12 | 2025-12-31 |
Purpose of Transaction (Item 4)
EcoR1 Capital, LLC
Scott Platshon, one of EcoR1's employees, resigned from the Issuer's board of directors as of November 16, 2025. Concurrently with his resignation, Mr. Platshon was appointed as the Issuer's Acting Chief Investment Officer. Oleg Nodelman, the manager of EcoR1, is a member of the Issuer's board of directors. The reporting persons acquired the Stock for investment purposes based on their belief that the Issuer's Common Stock, when purchased, was undervalued and represented an attractive investment opportunity. The reporting persons will routinely monitor the Issuer regarding a wide variety of factors that affect their investment considerations, including, current and anticipated future trading prices of the Common Stock and other securities, the Issuer's operations, assets, prospects, financial position, and business development, Issuer's management, Issuer-related competitive and strategic matters, general economic, financial market and industry conditions, and other investment considerations. Depending on their evaluation of various factors, the reporting persons may take such actions regarding their holdings of the Issuer's securities as they deem appropriate in light of circumstances existing from time to time. Such actions may include purchasing additional Common Stock in the open market, through privately negotiated transactions with third parties or otherwise, and selling at any time, in the open market, through privately negotiated transactions with third parties …The first part of Item 4 of the SCHEDULE 13D/A filed 2025-11-19; the filing has the rest
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-07-16 | BlackRock, Inc. | 4.8% | SCHEDULE 13G/A |
| 2025-08-14 | Redmile Group, LLC | 5.6% | SCHEDULE 13G/A |
| 2025-11-14 | Bvf Partners L P | 5.2% | SCHEDULE 13G/A |
| 2025-11-14 | Redmile Group, LLC | 4.9% | SCHEDULE 13G/A |
| 2025-11-19 | EcoR1 Capital, LLC | 30.7% | SCHEDULE 13D/A |
| 2026-02-12 | Morgan Stanley | 3.4% | SCHEDULE 13G/A |
| 2026-02-13 | Rubric Capital Management LP | 7.68% | SCHEDULE 13G/A |
| 2026-04-15 | Perceptive Advisors LLC | 5.4% | SCHEDULE 13G |
| 2026-05-15 | Rubric Capital Management LP | 9.49% | SCHEDULE 13G/A |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.