ZENAS BIOPHARMA INC ZBIO
COM · Common Stock · CUSIP 98937L105
- SectorHealth care
- IndustryPharmaceutical Preparations
- HeadquartersWaltham, MA
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($74.6k this quarter). Holder counts are more reliable. Shares outstanding: 65.2m as of 2026-07-31, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $25.28. Options: 4 managers hold calls ($7.6m notional), 2 hold puts ($487.3k).
Trends to Q2 2026
Institutional holders
Managers reporting a position, each quarter
Numbers
| Quarter | Holders |
|---|---|
| Q3 2024 | 45 |
| Q4 2024 | 66 |
| Q1 2025 | 68 |
| Q2 2025 | 74 |
| Q3 2025 | 80 |
| Q4 2025 | 119 |
| Q1 2026 | 140 |
| Q2 2026 | 145 |
Buyers vs sellers
Managers adding to or starting a position, vs cutting or selling out
Numbers
| Quarter | Bought or added | Cut or sold out |
|---|---|---|
| Q4 2024 | 43 | 20 |
| Q1 2025 | 25 | 29 |
| Q2 2025 | 44 | 17 |
| Q3 2025 | 38 | 27 |
| Q4 2025 | 78 | 32 |
| Q1 2026 | 102 | 45 |
| Q2 2026 | 89 | 61 |
Calls vs puts
Options held, notional value, last 4 quarters. P/C = puts ÷ calls
Numbers
| Quarter | Calls | Puts | P/C |
|---|---|---|---|
| Q3 2025 | $224.2k | $0 | 0.00 |
| Q4 2025 | $9.7m | $6.4m | 0.66 |
| Q1 2026 | $3.5m | $2.7m | 0.78 |
| Q2 2026 | $7.6m | $487.3k | 0.06 |
Biggest buyers
| PRICE T ROWE ASSOCIATES INC /MD/ | Added | +869.7k |
| BANK OF AMERICA CORP /DE/ | Added | +842.8k |
| BlackRock, Inc. | Added | +648.7k |
| STATE STREET CORP | Added | +584.2k |
| TWO SIGMA INVESTMENTS, LP | Added | +540.1k |
| FMR LLC | Added | +424.7k |
| WELLINGTON MANAGEMENT GROUP LLP | Added | +347.8k |
| GEODE CAPITAL MANAGEMENT, LLC | Added | +226.9k |
| ALLIANCEBERNSTEIN L.P. | Added | +206.1k |
| MILLENNIUM MANAGEMENT LLC | Added | +183.7k |
Biggest sellers
| SILVERARC CAPITAL MANAGEMENT, LLC | Reduced | -626.1k |
| GREAT POINT PARTNERS LLC | Sold out | -524.1k |
| Jefferies Financial Group Inc. | Sold out | -219.9k |
| UBS Group AG | Reduced | -189.3k |
| MARSHALL WACE, LLP | Reduced | -178.5k |
| SEB Asset Management AB | Sold out | -163.9k |
| Monashee Investment Management LLC | Sold out | -150.0k |
| Maven Securities LTD | Sold out | -150.0k |
| Polar Capital Holdings Plc | Reduced | -135.7k |
| Sio Capital Management, LLC | Reduced | -123.2k |
Biggest calls
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Added | $5.7m226.2k shares |
| JANE STREET GROUP, LLC | Added | $989.8k39.0k shares |
| CITADEL ADVISORS LLC | Added | $784.2k30.9k shares |
| SIMPLEX TRADING, LLC | Added | $58.4k2.3k shares |
Biggest puts
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Reduced | $479.7k18.9k shares |
| SIMPLEX TRADING, LLC | Reduced | $7.6k300 shares |
Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.
Major shareholders (over 5%)
Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.
| Holder | Stake |
|---|---|
| FMR LLC 13G · institution +3.3 pts · filed 2026-02-05 | 14.3% |
| InnoCare Pharma Inc. 13G · passive investor +1.0 pts · filed 2026-09-08 | 10.4% |
| WELLINGTON MANAGEMENT GROUP LLP 13G · institution new · filed 2026-09-08 | 10.1% |
SR ONE CAPITAL MANAGEMENT, LLC
13D · may seek influence
-1.7 pts · filed 2026-08-17
Stated purposeNot applicable. Full filing |
7.7% |
MOULDER LEON O JR
13D · may seek influence
+0.3 pts · filed 2026-05-05
Stated purposeThe information set forth in Item 3 of this Statement is incorporated herein by reference. Mr. Moulder serves as the Chairman of the Issuer's Board of Directors and as its Chief Executive Officer. In such capacity, Mr. Moulder has influence over the corporate activities of the Issuer, including activities that may relate to items described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. Except as described herein, the Reporting Persons have no present plans or proposals that relate to or would result in any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. However, the Reporting Persons reserve the right to formulate in the future plans or proposals which may relate to or result in the transactions described in subparagraphs (a) through … Full filing |
5.1% |
| BlackRock, Inc. 13G · institution new · filed 2026-10-27 | 5.0% |
Fell to 5% or below in the last year: Enavate Sciences GP, LLC (4.9%, 2026-08-19), Novo Holdings A/S (4.7%, 2025-11-14)
Insider purchases and sales since 1 Apr 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q4 2024 | 1 | $867.0k | 0 | — | — |
| Q1 2025 | 2 | $244.3k | 0 | — | — |
| Q2 2025 | 0 | — | 0 | — | — |
| Q3 2025 | 0 | — | 0 | — | — |
| Q4 2025 | 5 | $15.2m | 0 | — | — |
| Q1 2026 | 4 | $9.3m | 0 | — | — |
| Q2 2026 | 1 | $2.1m | 0 | — | — |
| Q3 2026 | 0 | — | 0 | — | — |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-05-18 | MOULDER LEON O JR Chief Executive Officer, director · See Footnote | Bought | $1.0m60.0k shares |
| 2026-04-29 | MOULDER LEON O JR Chief Executive Officer, director · See Footnote | Bought | $616.7k35.0k shares |
| 2026-04-28 | MOULDER LEON O JR Chief Executive Officer, director · See Footnote | Bought | $450.5k25.0k shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q2 2026
| Manager | Shares | Change |
|---|---|---|
| FMR LLC 0.01% of their portfolio | 9.5m $241.3m | Added +424.7k |
| SR One Capital Management, LP 12.31% of their portfolio | 5.0m $127.9m | Unchanged |
| NEA Management Company, LLC 6.43% of their portfolio | 4.0m $102.1m | Unchanged |
| ENAVATE SCIENCES GP, LLC 28.80% of their portfolio | 3.9m $99.5m | Unchanged |
| FEDERATED HERMES, INC. 0.11% of their portfolio | 3.1m $79.1m | Reduced -10.2k |
| BlackRock, Inc. 0.00% of their portfolio | 2.7m $68.2m | Added +648.7k |
| Capital International Investors 0.01% of their portfolio | 2.5m $63.5m | Added +68.9k |
| Polar Capital Holdings Plc 0.17% of their portfolio | 2.4m $61.2m | Reduced -135.7k |
| Royalty Pharma Sub-Manager, LLC 25.05% of their portfolio | 2.4m $60.6m | Unchanged |
| Fairmount Funds Management LLC 3.96% of their portfolio | 2.4m $59.9m | Unchanged |
| STATE STREET CORP 0.00% of their portfolio | 2.1m $52.2m | Added +584.2k |
| NVP ASSOCIATES, LLC 14.22% of their portfolio | 1.8m $46.7m | Unchanged |
| WELLINGTON MANAGEMENT GROUP LLP 0.01% of their portfolio | 1.6m $40.5m | Added +347.8k |
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 1.4m $34.4m | Added +109.5k |
| BANK OF AMERICA CORP /DE/ 0.00% of their portfolio | 1.2m $31.2m | Added +842.8k |
| PRICE T ROWE ASSOCIATES INC /MD/ 0.00% of their portfolio | 1.2m $31.1m | Added +869.7k |
| ALLIANCEBERNSTEIN L.P. 0.01% of their portfolio | 1.1m $21.6m | Added +206.1k |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 882.7k $22.4m | Added +226.9k |
| TWO SIGMA INVESTMENTS, LP 0.02% of their portfolio | 815.1k $20.7m | Added +540.1k |
| EcoR1 Capital, LLC 0.99% of their portfolio | 789.5k $20.0m | Unchanged |
| MILLENNIUM MANAGEMENT LLC 0.01% of their portfolio | 660.5k $16.8m | Added +183.7k |
| Woodline Partners LP 0.05% of their portfolio | 590.5k $15.0m | Added +14 |
| Balyasny Asset Management L.P. 0.03% of their portfolio | 576.7k $14.6m | Reduced -90.4k |
| ArrowMark Colorado Holdings LLC 0.61% of their portfolio | 573.3k $14.6m | Reduced -85.6k |
| SILVERARC CAPITAL MANAGEMENT, LLC 1.44% of their portfolio | 509.8k $12.9m | Reduced -626.1k |
| Rock Springs Capital Management LP 0.62% of their portfolio | 502.1k $12.7m | Unchanged |
| Pivotal bioVenture Partners Investment Advisor LLC 4.05% of their portfolio | 490.8k $12.5m | Reduced -101.2k |
| NEXTBio Capital Management LP 4.98% of their portfolio | 426.7k $10.8m | Unchanged |
| Vestal Point Capital, LP 0.22% of their portfolio | 365.0k $9.3m | Added +165.0k |
| MARSHALL WACE, LLP 0.01% of their portfolio | 323.4k $8.2m | Reduced -178.5k |
| JENNISON ASSOCIATES LLC 0.00% of their portfolio | 314.0k $8.0m | Added +64.0k |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.00% of their portfolio | 304.9k $7.7m | Added +53.5k |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.00% of their portfolio | 302.1k $7.7m | Added +77.7k |
| NORTHERN TRUST CORP 0.00% of their portfolio | 281.1k $7.1m | Added +86.5k |
| GOLDMAN SACHS GROUP INC 0.00% of their portfolio | 271.2k $6.9m | Reduced -110.3k |
| VANGUARD FIDUCIARY TRUST CO 0.00% of their portfolio | 254.6k $6.5m | Added +75.2k |
| SPHERA FUNDS MANAGEMENT LTD. 0.84% of their portfolio | 230.8k $5.9m | Added +16.5k |
| iA Global Asset Management Inc. 0.06% of their portfolio | 215.1k $5.5m | Reduced -700 |
| Walleye Capital LLC 0.03% of their portfolio | 209.1k $5.3m | Added +83.8k |
| Sio Capital Management, LLC 0.91% of their portfolio | 208.6k $5.3m | Reduced -123.2k |
| CITADEL ADVISORS LLC 0.00% of their portfolio | 195.8k $5.0m | Added +128.9k |
| UBS Group AG 0.00% of their portfolio | 178.1k $4.5m | Reduced -189.3k |
| Voleon Capital Management LP 0.08% of their portfolio | 167.1k $4.2m | Added +137.5k |
| BNP PARIBAS FINANCIAL MARKETS 0.00% of their portfolio | 151.1k $3.8m | Added +141.1k |
| MORGAN STANLEY 0.00% of their portfolio | 135.0k $3.4m | Added +41.6k |
| Squarepoint Ops LLC 0.01% of their portfolio | 125.2k $3.2m | Added +82.3k |
| BARCLAYS PLC 0.00% of their portfolio | 116.0k $2.9m | Added +86.4k |
| SEVEN GRAND MANAGERS, LLC 0.10% of their portfolio | 100.0k $2.5m | Unchanged |
| Birchview Capital, LP 1.11% of their portfolio | 93.6k $2.4m | Added +23.6k |
| Verition Fund Management LLC 0.01% of their portfolio | 73.0k $1.9m | New |
| Bank of New York Mellon Corp 0.00% of their portfolio | 70.5k $1.8m | Added +9.6k |
| J. Goldman & Co LP 0.06% of their portfolio | 68.2k $1.7m | Added +31.4k |
| CSM Advisors, LLC 0.04% of their portfolio | 67.6k $1.7m | New |
| Nuveen, LLC 0.00% of their portfolio | 66.6k $1.7m | Reduced -1.1k |
| ALPS ADVISORS INC 0.01% of their portfolio | 63.7k $1.6m | Added +20.0k |
| Swiss National Bank 0.00% of their portfolio | 53.2k $1.4m | Added +21.6k |
| Exome Asset Management LLC 0.82% of their portfolio | 52.4k $1.3m | Reduced -28.3k |
| Jump Financial, LLC 0.01% of their portfolio | 51.0k $1.3m | Reduced -9.0k |
| CITIGROUP INC 0.00% of their portfolio | 49.5k $1.3m | Added +39.6k |
| LOS ANGELES CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 48.5k $1.2m | New |
| XTX Topco Ltd 0.01% of their portfolio | 40.0k $1.0m | Added +20.7k |
| Burkehill Global Management, LP 0.04% of their portfolio | 40.0k $1.0m | Unchanged |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC 0.00% of their portfolio | 37.8k $959.1k | Added +22.3k |
| Rafferty Asset Management, LLC 0.00% of their portfolio | 37.5k $952.0k | Reduced -10.7k |
| Atom Investors LP 0.08% of their portfolio | 37.1k $942.8k | Reduced -69.9k |
| RHUMBLINE ADVISERS 0.00% of their portfolio | 34.2k $869.1k | Added +7.4k |
| BOOTHBAY FUND MANAGEMENT, LLC 0.02% of their portfolio | 33.3k $844.6k | New |
| AQR CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 31.1k $789.3k | Reduced -19.9k |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM 0.00% of their portfolio | 29.5k $748.0k | Added +13.7k |
| DEUTSCHE BANK AG\ 0.00% of their portfolio | 28.9k $733.0k | Added +9.6k |
| DCF Advisers, LLC 0.19% of their portfolio | 28.2k $715.3k | New |
| STATE OF WISCONSIN INVESTMENT BOARD 0.00% of their portfolio | 26.9k $683.3k | Added +6.1k |
| WELLS FARGO & COMPANY/MN 0.00% of their portfolio | 26.0k $659.8k | Added +17.1k |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 24.4k $660.5k | Reduced -664 |
| VANGUARD ASSET MANAGEMENT, Ltd 0.00% of their portfolio | 20.6k $523.4k | Added +10.0k |
| Legal & General Group Plc 0.00% of their portfolio | 20.0k $508.2k | Added +9.6k |
| Invesco Ltd. 0.00% of their portfolio | 19.0k $481.1k | Reduced -94.5k |
| China Universal Asset Management Co., Ltd. 0.03% of their portfolio | 18.8k $478.4k | Added +5.3k |
| PROFUND ADVISORS LLC 0.01% of their portfolio | 18.8k $478.1k | Reduced -2.6k |
| ALLSTATE CORP 0.00% of their portfolio | 18.2k $463.0k | Added +18 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. 0.00% of their portfolio | 17.4k $442.9k | Added +3.0k |
| Y-Intercept (Hong Kong) Ltd 0.01% of their portfolio | 17.3k $439.9k | New |
| MetLife Investment Management, LLC 0.00% of their portfolio | 17.0k $432.5k | Added +4.1k |
| Virtus Investment Advisers, LLC 0.10% of their portfolio | 16.5k $419.4k | Added +9.8k |
| Point72 Asset Management, L.P. 0.00% of their portfolio | 16.1k $409.5k | New |
| Vanguard Global Advisers, LLC 0.00% of their portfolio | 15.3k $389.1k | Reduced -5.5k |
| NORDEA INVESTMENT MANAGEMENT AB 0.00% of their portfolio | 15.1k $382.9k | New |
| Brevan Howard Capital Management LP 0.01% of their portfolio | 14.7k $372.4k | New |
| Engineers Gate Manager LP 0.00% of their portfolio | 13.0k $329.4k | New |
| Russell Investments Group, Ltd. 0.00% of their portfolio | 12.7k $323.3k | Added +10.0k |
| Creative Planning 0.00% of their portfolio | 11.7k $297.5k | Reduced -935 |
| VARCOV Co. 0.10% of their portfolio | 10.5k $266.6k | New |
| NEW YORK STATE COMMON RETIREMENT FUND 0.00% of their portfolio | 10.3k $261.4k | Added +4.1k |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ 0.00% of their portfolio | 9.1k $229.8k | New |
| Scientech Research LLC 0.19% of their portfolio | 9.0k $229.1k | Reduced -3.9k |
| HRT FINANCIAL LP 0.00% of their portfolio | 8.9k $225.0k | Reduced -16.9k |
| DIMENSIONAL FUND ADVISORS LP 0.00% of their portfolio | 8.9k $225.2k | New |
| Quantinno Capital Management LP 0.00% of their portfolio | 8.6k $217.8k | Reduced -12.5k |
| State of New Jersey Common Pension Fund D 0.00% of their portfolio | 8.6k $217.5k | New |
| SG Americas Securities, LLC 0.00% of their portfolio | 8.4k $214.0k | New |