Zenas BioPharma (ZBIO)
Zenas BioPharma on one page: short interest, daily short volume, fails to deliver, large holders, 13F holders, earnings dates and insider trades. Listed on Nasdaq, classified by the SEC as pharmaceutical preparations.
12.5M
Short interest
settlement 2026-10-15
18.8
Days to cover
+3.3 days vs prior
45.6%
Short share of volume
2026-11-03
606
Fails to deliver
settlement 2026-10-08
Wed 11 Nov
Next earnings
estimated date
$0
Insider flow, 90 days
0 buys, 0 sells
As of 2026-11-03.
Short interest
FINRA, twice a month. The newest 48 settlements in the table, 48 in the chart. JSONAs of 15 October 2026, short interest in ZBIO is 12,538,549 shares, up 667,203 shares over the last month. Over the last 48 readings it ranged from 635,745 shares (31 October 2024) to 12,538,549 shares (15 October 2026). The latest reading sits at the top of that range. At the reported average volume of 666K shares a day that is 18.8 days to cover.
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| Settlement | Shares short | Change | Avg daily volume | Days to cover |
|---|---|---|---|---|
| 2026-10-15 | 12,538,549 | +5.0% | 666,058 | 18.83 |
| 2026-09-30 | 11,941,601 | +0.6% | 771,653 | 15.48 |
| 2026-09-15 | 11,871,346 | +1.4% | 529,251 | 22.43 |
| 2026-08-31 | 11,702,288 | +0.4% | 825,023 | 14.18 |
| 2026-08-14 | 11,658,986 | -0.8% | 553,670 | 21.06 |
| 2026-07-31 | 11,753,566 | -3.4% | 850,076 | 13.83 |
| 2026-07-15 | 12,169,907 | -0.2% | 976,880 | 12.46 |
| 2026-06-30 | 12,196,436 | +9.6% | 1,264,717 | 9.64 |
| 2026-06-15 | 11,131,739 | +2.3% | 575,802 | 19.33 |
| 2026-05-29 | 10,879,470 | +1.8% | 599,922 | 18.13 |
| 2026-05-15 | 10,687,286 | -1.5% | 501,405 | 21.31 |
| 2026-04-30 | 10,853,674 | +6.2% | 452,799 | 23.97 |
| 2026-04-15 | 10,223,630 | +9.2% | 826,420 | 12.37 |
| 2026-03-31 | 9,362,107 | +21.4% | 1,251,928 | 7.48 |
| 2026-03-13 | 7,709,823 | -3.9% | 346,574 | 22.25 |
| 2026-02-27 | 8,023,712 | +2.9% | 749,549 | 10.70 |
| 2026-02-13 | 7,801,280 | +18.8% | 927,276 | 8.41 |
| 2026-01-30 | 6,568,745 | +7.9% | 580,250 | 11.32 |
| 2026-01-15 | 6,086,840 | +27.4% | 2,020,663 | 3.01 |
| 2025-12-31 | 4,779,373 | -3.5% | 401,626 | 11.90 |
| 2025-12-15 | 4,950,866 | +1.9% | 286,029 | 17.31 |
| 2025-11-28 | 4,858,909 | +5.5% | 338,392 | 14.36 |
| 2025-11-14 | 4,607,781 | -3.3% | 373,343 | 12.34 |
| 2025-10-31 | 4,766,849 | +9.9% | 702,385 | 6.79 |
| 2025-10-15 | 4,336,248 | -22.8% | 440,066 | 9.85 |
| 2025-09-30 | 5,616,578 | +1.2% | 279,570 | 20.09 |
| 2025-09-15 | 5,551,112 | -3.6% | 310,361 | 17.89 |
| 2025-08-29 | 5,760,485 | +9.4% | 209,120 | 27.55 |
| 2025-08-15 | 5,265,933 | +0.8% | 117,689 | 44.74 |
| 2025-07-31 | 5,225,303 | +3.0% | 125,978 | 41.48 |
| 2025-07-15 | 5,072,285 | -0.6% | 202,636 | 25.03 |
| 2025-06-30 | 5,100,082 | +3.9% | 182,621 | 27.93 |
| 2025-06-13 | 4,910,375 | +1.1% | 264,537 | 18.56 |
| 2025-05-30 | 4,856,506 | -1.2% | 116,396 | 41.72 |
| 2025-05-15 | 4,915,974 | +1.0% | 145,554 | 33.77 |
| 2025-04-30 | 4,868,705 | +10.9% | 138,696 | 35.10 |
| 2025-04-15 | 4,391,730 | +14.7% | 281,006 | 15.63 |
| 2025-03-31 | 3,829,081 | +2.5% | 224,408 | 17.06 |
| 2025-03-14 | 3,735,691 | +9.4% | 149,182 | 25.04 |
| 2025-02-28 | 3,413,513 | -1.6% | 122,851 | 27.79 |
| 2025-02-14 | 3,467,374 | +5.1% | 164,586 | 21.07 |
| 2025-01-31 | 3,298,451 | -1.2% | 233,369 | 14.13 |
| 2025-01-15 | 3,337,191 | +3.8% | 189,062 | 17.65 |
| 2024-12-31 | 3,216,251 | +51.0% | 624,033 | 5.15 |
| 2024-12-13 | 2,130,663 | +44.9% | 362,161 | 5.88 |
| 2024-11-29 | 1,470,292 | +83.9% | 406,491 | 3.62 |
| 2024-11-15 | 799,397 | +25.7% | 86,940 | 9.19 |
| 2024-10-31 | 635,745 | +55.5% | 159,971 | 3.97 |
Daily short volume
FINRA Reg SHO, the last 30 sessions. JSONAs of 3 November 2026, the short share of ZBIO volume is 45.6%, down 25.1 points over the last five sessions. Over the last 30 readings it ranged from 34.0% (15 October 2026) to 82.0% (9 October 2026). The latest reading is 16.1 points below the 30-session average of 61.7%, on 178K shares reported.
| Date | Short volume | Total volume | Short share | Exempt |
|---|---|---|---|---|
| 2026-11-03 | 81K | 178K | 45.6% | 0 |
| 2026-11-02 | 58K | 147K | 39.6% | 12 |
| 2026-10-30 | 64K | 126K | 51.1% | 1 |
| 2026-10-29 | 64K | 100K | 64.0% | 0 |
| 2026-10-28 | 74K | 110K | 66.9% | 0 |
| 2026-10-27 | 102K | 144K | 70.7% | 0 |
| 2026-10-26 | 48K | 83K | 57.2% | 0 |
| 2026-10-23 | 57K | 109K | 51.8% | 0 |
| 2026-10-22 | 62K | 111K | 55.3% | 0 |
| 2026-10-21 | 119K | 177K | 66.9% | 0 |
| 2026-10-20 | 161K | 228K | 70.8% | 0 |
| 2026-10-19 | 216K | 283K | 76.3% | 0 |
| 2026-10-16 | 190K | 238K | 79.6% | 1,520 |
| 2026-10-15 | 71K | 209K | 34.0% | 0 |
| 2026-10-14 | 75K | 129K | 58.3% | 0 |
| 2026-10-13 | 132K | 182K | 72.4% | 0 |
| 2026-10-12 | 73K | 125K | 58.2% | 0 |
| 2026-10-09 | 124K | 151K | 82.0% | 0 |
| 2026-10-08 | 110K | 145K | 75.9% | 0 |
| 2026-10-07 | 79K | 112K | 70.2% | 0 |
| 2026-10-06 | 90K | 126K | 71.3% | 0 |
| 2026-10-05 | 585K | 775K | 75.6% | 0 |
| 2026-10-02 | 626K | 1.1M | 55.8% | 0 |
| 2026-10-01 | 237K | 373K | 63.6% | 0 |
| 2026-09-30 | 118K | 189K | 62.4% | 0 |
| 2026-09-29 | 70K | 157K | 44.5% | 0 |
| 2026-09-28 | 148K | 253K | 58.4% | 0 |
| 2026-09-25 | 160K | 327K | 48.9% | 1,177 |
| 2026-09-24 | 191K | 356K | 53.7% | 7,617 |
| 2026-09-23 | 120K | 169K | 70.7% | 161 |
Fails to deliver
SEC, the last 30 settlement dates with a fail. JSONAs of 8 October 2026, the fails-to-deliver balance in ZBIO is 606 shares, up 559 shares over the last settlement date. Over the last 30 readings it ranged from 1 share (10 July 2026) to 99,794 shares (1 July 2026). The latest reading sits at the bottom of that range.
| Settlement | Shares failed | Price | Value |
|---|---|---|---|
| 2026-10-08 | 606 | $28.18 | $17K |
| 2026-10-05 | 47 | $28.30 | $1K |
| 2026-10-02 | 4,569 | $27.94 | $128K |
| 2026-09-30 | 1,030 | $26.76 | $28K |
| 2026-09-29 | 544 | $27.55 | $15K |
| 2026-09-24 | 1,550 | $29.63 | $46K |
| 2026-09-16 | 45 | $31.93 | $1K |
| 2026-09-15 | 149 | $31.91 | $5K |
| 2026-09-08 | 427 | $32.88 | $14K |
| 2026-08-26 | 8,151 | $33.77 | $275K |
| 2026-08-19 | 2,600 | $31.91 | $83K |
| 2026-08-18 | 7 | $30.50 | $214 |
| 2026-07-30 | 292 | $31.09 | $9K |
| 2026-07-28 | 310 | $32.82 | $10K |
| 2026-07-20 | 1,780 | $29.53 | $53K |
| 2026-07-17 | 32,548 | $28.24 | $919K |
| 2026-07-16 | 36 | $29.41 | $1K |
| 2026-07-10 | 1 | $29.43 | $29 |
| 2026-07-09 | 9,993 | $28.77 | $287K |
| 2026-07-08 | 22,978 | $27.68 | $636K |
| 2026-07-07 | 45,099 | $26.45 | $1.2M |
| 2026-07-02 | 347 | $28.00 | $10K |
| 2026-07-01 | 99,794 | $25.38 | $2.5M |
| 2026-06-30 | 52,399 | $25.55 | $1.3M |
| 2026-06-29 | 35,787 | $25.87 | $926K |
| 2026-06-26 | 13,338 | $24.67 | $329K |
| 2026-06-24 | 1,442 | $20.21 | $29K |
| 2026-06-18 | 11 | $18.58 | $204 |
| 2026-06-15 | 2,450 | $19.80 | $49K |
| 2026-06-12 | 2,692 | $17.76 | $48K |
Insider trades
SEC Form 4, newest first. JSONNo open-market insider trades were reported for ZBIO in the last 90 days. The most recent filings are listed below. Latest filing: MOULDER LEON O JR (Chief Executive Officer) on 2026-05-18.
| Date | Insider | Title | Type | Shares | Price | Value | Owned after |
|---|---|---|---|---|---|---|---|
| 2026-05-18 | MOULDER LEON O JR | Chief Executive Officer | Buy | 60K | $16.88 | $1.0M | 97K |
| 2026-04-29 | MOULDER LEON O JR | Chief Executive Officer | Buy | 35K | $17.62 | $617K | 1.8M |
| 2026-04-28 | MOULDER LEON O JR | Chief Executive Officer | Buy | 25K | $18.02 | $451K | 1.8M |
| 2026-03-31 | Kiselak Tomas | Director | Buy | 150K | $20.00 | $3.0M | 2.4M |
| 2026-03-31 | MOULDER LEON O JR | Chief Executive Officer | Buy | 34K | $19.31 | $657K | 1.7M |
| 2026-03-31 | Lu Hongbo | Director | Buy | 75K | $20.00 | $1.5M | 423K |
| 2026-03-31 | Fairmount Funds Management LLC | Director | Buy | 150K | $20.00 | $3.0M | 2.4M |
| 2026-03-31 | Lu Hongbo | Director | Buy | 4K | $18.63 | $70K | 427K |
| 2026-03-30 | MOULDER LEON O JR | Chief Executive Officer | Buy | 20K | $18.23 | $365K | 1.7M |
| 2026-02-13 | Allen Patricia L | Director | Buy | 4K | $26.36 | $110K | 20K |
| 2026-02-12 | Allen Patricia L | Director | Buy | 5K | $26.50 | $133K | 16K |
| 2026-02-12 | Allen Patricia L | Director | Buy | 6K | $24.34 | $139K | 11K |
| 2026-02-12 | Allen Patricia L | Director | Buy | 5K | $23.77 | $119K | 5K |
| 2026-02-11 | Lu Hongbo | Director | Buy | 26K | $22.50 | $585K | 348K |
| 2026-02-05 | Fox Jennifer A. | See Remarks | Grant | 2K | $13.35 | $21K | 2K |
| 2026-02-05 | Farmer Joseph L | See Remarks | Grant | 974 | $13.35 | $13K | 974 |
| 2026-02-02 | MOULDER LEON O JR | Chief Executive Officer | Buy | 57K | $17.96 | $1.0M | 423K |
| 2026-01-09 | MOULDER LEON O JR | Chief Executive Officer | Buy | 20K | $16.55 | $331K | 366K |
| 2026-01-08 | MOULDER LEON O JR | Chief Executive Officer | Buy | 30K | $16.30 | $489K | 346K |
| 2026-01-07 | MOULDER LEON O JR | Chief Executive Officer | Buy | 50K | $16.38 | $819K | 316K |
| 2025-10-09 | Nunn Jason Raleigh | Director | Buy | 63K | $19.00 | $1.2M | 1.2M |
| 2025-10-09 | SR ONE CAPITAL MANAGEMENT, LLC | 10% owner | Buy | 63K | $19.00 | $1.2M | 1.9M |
| 2025-10-09 | SR ONE CAPITAL MANAGEMENT, LLC | 10% owner | Buy | 63K | $19.00 | $1.2M | 1.2M |
| 2025-10-09 | ENRIGHT PATRICK G | Director | Buy | 12K | $20.85 | $250K | 12K |
| 2025-10-09 | ENRIGHT PATRICK G | Director | Buy | 105K | $19.00 | $2.0M | 1.8M |
| 2025-10-07 | Harwin Peter Evan | Director | Buy | 316K | $19.00 | $6.0M | 2.2M |
| 2025-10-07 | MOULDER LEON O JR | See Remarks | Buy | 37K | $20.85 | $770K | 37K |
| 2025-10-07 | Lu Hongbo | Director | Buy | 263K | $19.00 | $5.0M | 322K |
| 2025-10-07 | Fairmount Funds Management LLC | Director | Buy | 316K | $19.00 | $6.0M | 2.2M |
| 2025-02-18 | MOULDER LEON O JR | Chief Executive Officer | Buy | 25K | $6.67 | $167K | 266K |
| 2025-02-07 | Xiao Ting | Director | Buy | 10K | $7.76 | $78K | 10K |
| 2025-02-07 | Xiao Ting | Director | Buy | 10K | $7.76 | $78K | 47K |
| 2024-12-04 | MOULDER LEON O JR | Chief Executive Officer | Buy | 45K | $9.98 | $449K | 241K |
| 2024-12-03 | MOULDER LEON O JR | Chief Executive Officer | Buy | 25K | $10.76 | $269K | 196K |
| 2024-11-19 | MOULDER LEON O JR | Chief Executive Officer | Buy | 3K | $14.57 | $36K | 171K |
| 2024-11-18 | MOULDER LEON O JR | Chief Executive Officer | Buy | 8K | $15.00 | $113K | 169K |
| 2024-09-20 | MOULDER LEON O JR | Chief Executive Officer | Buy | 2K | $17.88 | $42K | 1.7M |
| 2024-09-20 | MOULDER LEON O JR | Chief Executive Officer | Buy | 3K | $18.97 | $50K | 1.7M |
| 2024-09-19 | MOULDER LEON O JR | Chief Executive Officer | Buy | 5K | $17.89 | $89K | 1.7M |
| 2024-09-18 | MOULDER LEON O JR | Chief Executive Officer | Buy | 10K | $17.91 | $179K | 1.7M |
| 2024-09-16 | Nunn Jason Raleigh | Director | Buy | 441K | $17.00 | $7.5M | 1.1M |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | 10% owner | Buy | 441K | $17.00 | $7.5M | 1.9M |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 165K | price not stated in the filing | not stated | 165K |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 108K | price not stated in the filing | not stated | 108K |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 372K | price not stated in the filing | not stated | 537K |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 48K | price not stated in the filing | not stated | 157K |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | TenPercentOwner | Buy | 1.4M | $17.00 | $23.0M | 1.9M |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | TenPercentOwner | Conversion | 1.5M | price not stated in the filing | not stated | 1.5M |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | TenPercentOwner | Buy | 441K | $17.00 | $7.5M | 1.1M |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | TenPercentOwner | Conversion | 669K | price not stated in the filing | not stated | 669K |
| 2024-09-16 | SR ONE CAPITAL MANAGEMENT, LLC | TenPercentOwner | Conversion | 502K | price not stated in the filing | not stated | 502K |
| 2024-09-16 | Harwin Peter Evan | Director | Conversion | 41K | price not stated in the filing | not stated | 41K |
| 2024-09-16 | Harwin Peter Evan | Director | Conversion | 253K | price not stated in the filing | not stated | 294K |
| 2024-09-16 | Harwin Peter Evan | Director | Conversion | 710K | price not stated in the filing | not stated | 1.0M |
| 2024-09-16 | Harwin Peter Evan | Director | Buy | 300K | $17.00 | $5.1M | 1.6M |
| 2024-09-16 | Harwin Peter Evan | Director | Conversion | 301K | price not stated in the filing | not stated | 1.3M |
| 2024-09-16 | Nunn Jason Raleigh | Director | Buy | 441K | $17.00 | $7.5M | 1.9M |
| 2024-09-16 | Nunn Jason Raleigh | Director | Conversion | 669K | price not stated in the filing | not stated | 669K |
| 2024-09-16 | Nunn Jason Raleigh | Director | Conversion | 1.5M | price not stated in the filing | not stated | 1.5M |
| 2024-09-16 | ENRIGHT PATRICK G | Director | Conversion | 1.0M | price not stated in the filing | not stated | 1.7M |
| 2024-09-16 | ENRIGHT PATRICK G | Director | Conversion | 724K | price not stated in the filing | not stated | 724K |
| 2024-09-16 | ENRIGHT PATRICK G | Director | Buy | 440K | $17.00 | $7.5M | 775K |
| 2024-09-16 | ENRIGHT PATRICK G | Director | Conversion | 335K | price not stated in the filing | not stated | 335K |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 372K | price not stated in the filing | not stated | 1.7M |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 165K | price not stated in the filing | not stated | 1.3M |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 108K | price not stated in the filing | not stated | 113K |
| 2024-09-16 | MOULDER LEON O JR | Chief Executive Officer | Conversion | 48K | price not stated in the filing | not stated | 161K |
| 2024-09-16 | Fairmount Funds Management LLC | Director | Buy | 300K | $17.00 | $5.1M | 1.9M |
| 2024-09-16 | Fairmount Funds Management LLC | Director | Conversion | 41K | price not stated in the filing | not stated | 329K |
| 2024-09-16 | Fairmount Funds Management LLC | Director | Conversion | 253K | price not stated in the filing | not stated | 582K |
| 2024-09-16 | Fairmount Funds Management LLC | Director | Conversion | 301K | price not stated in the filing | not stated | 1.6M |
| 2024-09-16 | Fairmount Funds Management LLC | Director | Conversion | 710K | price not stated in the filing | not stated | 1.3M |
| 2024-09-16 | Zebra Aggregator, LP | TenPercentOwner | Buy | 882K | $17.00 | $15.0M | 3.8M |
| 2024-09-16 | Zebra Aggregator, LP | TenPercentOwner | Conversion | 2.9M | price not stated in the filing | not stated | 2.9M |
| 2024-09-16 | Wellington Biomedical Innovation Master Investors (Cayman) I L.P. | TenPercentOwner | Conversion | 201K | price not stated in the filing | not stated | 802K |
| 2024-09-16 | Wellington Biomedical Innovation Master Investors (Cayman) I L.P. | TenPercentOwner | Conversion | 181K | price not stated in the filing | not stated | 181K |
| 2024-09-16 | Wellington Biomedical Innovation Master Investors (Cayman) I L.P. | TenPercentOwner | Conversion | 420K | price not stated in the filing | not stated | 601K |
| 2024-09-13 | Lu Hongbo | Director | Buy | 59K | $17.00 | $1000K | 59K |
Form 4 filings are due within two business days of the trade. Insiders sell for many reasons that say nothing about the company; open-market buys are rarer.
Large holders (13D and 13G)
One row per reporting person with its latest filing, newest first. JSON13 holders report 5% or more of ZBIO in their latest filing, 3 on Schedule 13D (active intent). The largest reported stake is FMR LLC at 14.3% of the class (7,652,255 shares), filed 2026-02-05 for an event on 2025-12-31.
| Filed | Form | Holder | Shares | Of class | Event |
|---|---|---|---|---|---|
| 2026-10-27 | 13G | BlackRock, Inc.parent holding company | 3.3M | 5.0% | 2026-09-30 |
| 2026-09-08 | 13G | Wellington Management Group LLPparent holding company | 6.6M | 10.1% | 2026-08-31 |
| 2026-09-08 | 13G | Wellington Group Holdings LLPparent holding company | 6.6M | 10.1% | 2026-08-31 |
| 2026-09-08 | 13G | Wellington Investment Advisors Holdings LLPparent holding company | 6.6M | 10.1% | 2026-08-31 |
| 2026-09-08 | 13G | Wellington Management Company LLPinvestment adviser | 6.6M | 9.9% | 2026-08-31 |
| 2026-09-08 | 13G/Ano. 1 | InnoCare Pharma Limitedother entity | 7.0M | 10.4% | 2026-08-26 |
| 2026-09-08 | 13G/Ano. 1 | InnoCare Pharma Inc.corporation | 7.0M | 10.4% | 2026-08-26 |
| 2026-09-08 | 13G/Ano. 1 | Ocean Prominent Limitedother entity | 7.0M | 10.4% | 2026-08-26 |
| 2026-08-19 | 13D/Ano. 2 | Enavate Sciences GP, LLCother entity | 3.2M | 4.9% | 2026-08-19 |
| 2026-08-19 | 13D/Ano. 2 | Zebra Aggregator, LPpartnership | 3.2M | 4.9% | 2026-08-19 |
| 2026-08-17 | 13D/Ano. 2 | Simeon Georgeindividual | 5.0M | 7.7% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital Management, LLCother entity | 5.0M | 7.7% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital Partners II, LPpartnership | 1.9M | 3.0% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital Fund II Aggregator, LPpartnership | 1.9M | 3.0% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | AMZL, LPpartnership | 1.9M | 2.9% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital SMA Partners, LPpartnership | 1.9M | 2.9% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital Opportunities Partners I, LPpartnership | 1.2M | 1.8% | 2026-08-13 |
| 2026-08-17 | 13D/Ano. 2 | SR One Capital Opportunities Fund I, LPpartnership | 1.2M | 1.8% | 2026-08-13 |
| 2026-05-05 | 13D | MOULDER LEON O JRindividual | 3.2M | 5.1% | 2026-04-29 |
| 2026-05-05 | 13D | Tellus BioVentures, LLCother entity | 1.8M | 2.9% | 2026-04-29 |
| 2026-05-05 | 13D | Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008other entity | 37K | 0.1% | 2026-04-29 |
| 2026-04-02 | 13D/Ano. 1 | Leon O. Moulder, Jr.individual | 3.0M | 4.8% | 2026-03-31 |
| 2026-02-05 | 13G/Ano. 4 | FMR LLCparent holding company | 7.7M | 14.3% | 2025-12-31 |
| 2026-02-05 | 13G/Ano. 4 | Abigail P. Johnsonindividual | 7.7M | 14.3% | 2025-12-31 |
| 2025-11-14 | 13G/Ano. 1 | Novo Holdings A/Scorporation | 2.0M | 4.7% | 2025-09-30 |
| 2025-10-14 | 13D/Ano. 1 | Patrick G. Enrightindividual | 2.6M | 4.9% | 2025-10-09 |
| 2025-10-14 | 13D/Ano. 1 | Juliet Tammenoms Bakkerindividual | 2.6M | 4.9% | 2025-10-09 |
| 2025-10-14 | 13D/Ano. 1 | Longitude Capital Partners IV, LLCother entity | 1.8M | 3.4% | 2025-10-09 |
| 2025-10-14 | 13D/Ano. 1 | Longitude Venture Partners IV, L.P.partnership | 1.8M | 3.4% | 2025-10-09 |
| 2025-10-14 | 13D/Ano. 1 | Longitude Prime Fund, L.P.partnership | 775K | 1.4% | 2025-10-09 |
| 2025-10-14 | 13D/Ano. 1 | Longitude Prime Partners, LLCother entity | 775K | 1.4% | 2025-10-09 |
13F holders
Tracked managers holding ZBIO at their latest 13F. JSON5 of the 30 tracked managers held ZBIO at their latest 13F, $43.6M in total at quarter-end prices. Two Sigma Investments is the largest at $20.7M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 4 added shares and 1 cut.
| Fund | Quarter | Shares | Value | Of portfolio | Change in shares |
|---|---|---|---|---|---|
| Two Sigma Investments | 2026-06-30 | 815K | $20.7M | 0.01% | +540K |
| Millennium Management | 2026-06-30 | 660K | $16.8M | 0.01% | +184K |
| Citadel Advisors | 2026-06-30 | 196K | $5.0M | 0.00% | +129K |
| AQR Capital Management | 2026-06-30 | 31K | $789K | 0.00% | -20K |
| Point72 Asset Management | 2026-06-30 | 16K | $410K | 0.00% | new |
Only the 30 tracked managers on the funds hub; a 13F reports long positions in US listed stock at quarter end, 45 days late, and says nothing about shorts or positions sold since.
What this page is
Zenas BioPharma in the regulatory record
Regulators publish company data in separate files that never sit next to each other: FINRA's twice-monthly short interest, its daily short sale volume, the SEC's fails-to-deliver counts, and each insider's Form 4. A company page puts those series for one ticker on one URL, with planned sales, large holders, 13F holders and financials beside them, so the short position, the daily flow, the settlement fails and what insiders are doing can be read together.
Each section has its own history table, a one-line summary of the latest figures and its own JSON and CSV links, and says when its source last updated.
This page follows Zenas BioPharma (ZBIO), SEC CIK 1953926, listed on Nasdaq, classified by the SEC as pharmaceutical preparations. The cross-market tables live on the short interest and insider transactions hubs.
Source and updates
- Short interest
- FINRA consolidated short interestSource: FINRA.Twice a month, about eight business days after settlement. Latest 2026-10-15.JSON and CSV
- Daily short volume
- FINRA Reg SHO daily filesSource: FINRA.Every trading day, the morning after FINRA posts it. Latest 2026-11-03.JSON and CSV
- Fails to deliver
- SEC fails-to-deliver dataSource: SEC.Twice a month, a few weeks after the half month ends. Latest 2026-10-08.JSON and CSV
- Large holders
- SEC EDGAR Schedule 13D and 13GSource: SEC.New filings appear shortly after the SEC posts them. A 13D is due within five business days of crossing 5%; a 13G follows the passive schedule. Latest 2026-10-27.JSON and CSV
- 13F holders
- SEC EDGAR Form 13F-HRSource: SEC.Quarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
- Earnings dates
- SEC EDGAR 8-K filings (Item 2.02)Source: SEC.Twice a day. Reported dates come from the company's 8-K filings; the next date is marked as an estimate until the 8-K arrives. Latest 2026-08-13.JSON and CSV
- Insider trades
- SEC EDGAR Form 4Source: SEC.New filings appear shortly after the SEC posts them; they're due two business days after the trade. Latest 2026-05-18.JSON and CSV
- Company record
- EDGAR filing index for CIK 1953926Ticker, name and exchange from the SEC's company list, refreshed weekly.
- Rate limits
- 10 requests a minute without a key, 30 with a free key from a free account.
How to read it
- Read the position against the flow: rising short interest with a high daily short share is new shorting; rising short interest with a normal short share is old shorts holding on.
- Insider buys next to a large short position are rare and stand out; insider sells next to one are common and mean little.
- Fails to deliver matter relative to the float, not in absolute shares; a million failed shares in a mega cap is noise.
Analysis of what the data shows, not advice. XOOMAR does not recommend buying, selling or holding anything.
Other companies the SEC classifies as pharmaceutical preparations
Other company pages
Datasets
Frequently Asked Questions
How much of ZBIO is sold short?
12,538,549 shares were held short at the 2026-10-15 settlement, 18.8 days of average volume. FINRA publishes the next count about eight business days after the 15th and the last business day of the month.
What is ZBIO's daily short volume?
On 2026-11-03, 81,148 of the 177,937 ZBIO shares reported to FINRA were sold short, 45.6% of the day's reported volume. Short volume is a flow for one day, not a position.
Does ZBIO have fails to deliver?
The SEC's latest file shows 606 ZBIO shares failed to deliver at settlement 2026-10-08. Fails are reported per settlement date and published twice a month with a lag.
Are ZBIO insiders buying or selling?
No open-market insider trades were reported for ZBIO in the last 90 days. The most recent filings are listed below. Latest filing: MOULDER LEON O JR (Chief Executive Officer) on 2026-05-18.
Who owns 5% or more of ZBIO?
13 holders report 5% or more of ZBIO in their latest filing, 3 on Schedule 13D (active intent). The largest reported stake is FMR LLC at 14.3% of the class (7,652,255 shares), filed 2026-02-05 for an event on 2025-12-31.
Which tracked 13F managers own ZBIO?
5 of the 30 tracked 13F managers held ZBIO shares at their latest filing, $43.6M in all. The largest: Two Sigma Investments (815K shares, $20.7M), Izzy Englander's Millennium Management (660K shares, $16.8M), Ken Griffin's Citadel Advisors (196K shares, $5.0M), Cliff Asness's AQR Capital Management (31K shares, $789K), Steve Cohen's Point72 Asset Management (16K shares, $410K).
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.