Atara Biotherapeutics (ATRA)
Atara Biotherapeutics on one page: short interest, daily short volume, fails to deliver, planned sales, large holders, 13F holders, earnings dates and insider trades. Listed on Nasdaq, classified by the SEC as biological products, (no diagnostic substances).
350K
Short interest
settlement 2026-10-15
8.7
Days to cover
+0.6 days vs prior
71.4%
Short share of volume
2026-11-03
2,836
Fails to deliver
settlement 2026-10-14
Wed 11 Nov
Next earnings
estimated date
$959K
Insider flow, 90 days
1 buys, 1 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 ATRA is 350,260 shares, down 54,010 shares over the last month. Over the last 48 readings it ranged from 128,849 shares (15 October 2025) to 1,016,616 shares (15 January 2026). At the reported average volume of 40K shares a day that is 8.7 days to cover.
Embed this chart.The embed keeps its attribution line.
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| Settlement | Shares short | Change | Avg daily volume | Days to cover |
|---|---|---|---|---|
| 2026-10-15 | 350,260 | +8.8% | 40,263 | 8.70 |
| 2026-09-30 | 321,792 | -20.4% | 39,657 | 8.11 |
| 2026-09-15 | 404,270 | -5.4% | 55,057 | 7.34 |
| 2026-08-31 | 427,435 | -10.4% | 38,619 | 11.07 |
| 2026-08-14 | 477,268 | -11.1% | 51,842 | 9.21 |
| 2026-07-31 | 536,897 | -7.0% | 57,166 | 9.39 |
| 2026-07-15 | 577,635 | +59.8% | 92,530 | 6.24 |
| 2026-06-30 | 361,520 | -26.6% | 91,505 | 3.95 |
| 2026-06-15 | 492,405 | +1.6% | 78,554 | 6.27 |
| 2026-05-29 | 484,391 | -11.4% | 166,237 | 2.91 |
| 2026-05-15 | 546,470 | +78.5% | 7,386,437 | 1.00 |
| 2026-04-30 | 306,093 | -3.7% | 50,142 | 6.10 |
| 2026-04-15 | 317,953 | -2.8% | 77,634 | 4.10 |
| 2026-03-31 | 327,066 | +4.4% | 108,635 | 3.01 |
| 2026-03-13 | 313,290 | -5.2% | 864,901 | 1.00 |
| 2026-02-27 | 330,524 | +57.9% | 155,018 | 2.13 |
| 2026-02-13 | 209,287 | -25.9% | 87,228 | 2.40 |
| 2026-01-30 | 282,525 | -72.2% | 351,029 | 1.00 |
| 2026-01-15 | 1,016,616 | +500.8% | 1,101,087 | 1.00 |
| 2025-12-31 | 169,201 | +1.4% | 66,178 | 2.56 |
| 2025-12-15 | 166,856 | +1.3% | 82,905 | 2.01 |
| 2025-11-28 | 164,713 | -6.8% | 58,956 | 2.79 |
| 2025-11-14 | 176,777 | +4.9% | 74,588 | 2.37 |
| 2025-10-31 | 168,549 | +30.8% | 45,357 | 3.72 |
| 2025-10-15 | 128,849 | -13.9% | 61,142 | 2.11 |
| 2025-09-30 | 149,590 | -7.4% | 59,707 | 2.51 |
| 2025-09-15 | 161,507 | -7.1% | 45,951 | 3.51 |
| 2025-08-29 | 173,825 | -11.4% | 55,087 | 3.16 |
| 2025-08-15 | 196,215 | -6.8% | 44,671 | 4.39 |
| 2025-07-31 | 210,641 | -21.4% | 86,105 | 2.45 |
| 2025-07-15 | 268,036 | +0.5% | 35,061 | 7.64 |
| 2025-06-30 | 266,647 | -6.7% | 36,962 | 7.21 |
| 2025-06-13 | 285,774 | -22.2% | 59,317 | 4.82 |
| 2025-05-30 | 367,405 | -11.0% | 76,593 | 4.80 |
| 2025-05-15 | 412,857 | -20.9% | 71,740 | 5.75 |
| 2025-04-30 | 522,139 | -21.1% | 39,037 | 13.38 |
| 2025-04-15 | 662,188 | -0.7% | 54,624 | 12.12 |
| 2025-03-31 | 666,785 | -7.8% | 49,245 | 13.54 |
| 2025-03-14 | 723,264 | +1.1% | 59,127 | 12.23 |
| 2025-02-28 | 715,084 | +6.0% | 81,444 | 8.78 |
| 2025-02-14 | 674,628 | -4.5% | 120,982 | 5.58 |
| 2025-01-31 | 706,465 | +29.0% | 616,635 | 1.15 |
| 2025-01-15 | 547,760 | +2.6% | 233,832 | 2.34 |
| 2024-12-31 | 533,616 | -3.2% | 94,986 | 5.62 |
| 2024-12-13 | 551,465 | +1.4% | 80,554 | 6.85 |
| 2024-11-29 | 543,952 | +4.7% | 79,912 | 6.81 |
| 2024-11-15 | 519,528 | -18.4% | 177,066 | 2.93 |
| 2024-10-31 | 636,280 | -0.5% | 100,465 | 6.33 |
Daily short volume
FINRA Reg SHO, the last 30 sessions. JSONAs of 3 November 2026, the short share of ATRA volume is 71.4%, down 10.7 points over the last five sessions. Over the last 30 readings it ranged from 16.8% (12 October 2026) to 90.9% (13 October 2026). The latest reading is 23.9 points above the 30-session average of 47.5%, on 3K shares reported.
| Date | Short volume | Total volume | Short share | Exempt |
|---|---|---|---|---|
| 2026-11-03 | 2K | 3K | 71.4% | 0 |
| 2026-11-02 | 5K | 11K | 41.0% | 1 |
| 2026-10-30 | 5K | 14K | 37.1% | 0 |
| 2026-10-29 | 2K | 6K | 36.1% | 90 |
| 2026-10-28 | 3K | 5K | 61.4% | 0 |
| 2026-10-27 | 2K | 2K | 82.1% | 0 |
| 2026-10-26 | 7K | 13K | 51.0% | 0 |
| 2026-10-23 | 1K | 6K | 24.2% | 0 |
| 2026-10-22 | 1K | 4K | 37.1% | 0 |
| 2026-10-21 | 978 | 3K | 37.7% | 0 |
| 2026-10-20 | 1K | 4K | 30.0% | 0 |
| 2026-10-19 | 1K | 3K | 49.5% | 0 |
| 2026-10-16 | 888 | 2K | 44.9% | 0 |
| 2026-10-15 | 3K | 5K | 52.6% | 34 |
| 2026-10-14 | 2K | 10K | 21.8% | 0 |
| 2026-10-13 | 11K | 12K | 90.9% | 0 |
| 2026-10-12 | 3K | 15K | 16.8% | 0 |
| 2026-10-09 | 2K | 5K | 34.0% | 0 |
| 2026-10-08 | 1K | 4K | 29.9% | 0 |
| 2026-10-07 | 1K | 4K | 29.7% | 0 |
| 2026-10-06 | 3K | 11K | 26.8% | 0 |
| 2026-10-05 | 8K | 16K | 50.8% | 0 |
| 2026-10-02 | 24K | 32K | 74.5% | 0 |
| 2026-10-01 | 28K | 46K | 61.7% | 100 |
| 2026-09-30 | 9K | 14K | 66.5% | 149 |
| 2026-09-29 | 11K | 33K | 32.8% | 45 |
| 2026-09-28 | 2K | 8K | 24.3% | 0 |
| 2026-09-25 | 9K | 11K | 83.0% | 0 |
| 2026-09-24 | 2K | 3K | 66.3% | 0 |
| 2026-09-23 | 6K | 9K | 58.4% | 0 |
Fails to deliver
SEC, the last 30 settlement dates with a fail. JSONAs of 14 October 2026, the fails-to-deliver balance in ATRA is 2,836 shares, up 1,129 shares over the last settlement date. Over the last 30 readings it ranged from 164 shares (3 August 2026) to 12,537 shares (7 July 2026).
| Settlement | Shares failed | Price | Value |
|---|---|---|---|
| 2026-10-14 | 2,836 | $9.31 | $26K |
| 2026-10-13 | 1,707 | $9.38 | $16K |
| 2026-10-08 | 216 | $9.37 | $2K |
| 2026-10-06 | 283 | $9.40 | $3K |
| 2026-10-05 | 3,180 | $9.48 | $30K |
| 2026-10-01 | 1,735 | $8.50 | $15K |
| 2026-09-29 | 194 | $8.37 | $2K |
| 2026-09-28 | 3,906 | $8.81 | $34K |
| 2026-09-24 | 828 | $8.56 | $7K |
| 2026-09-17 | 2,316 | $10.11 | $23K |
| 2026-09-08 | 805 | $9.76 | $8K |
| 2026-09-01 | 1,255 | $8.90 | $11K |
| 2026-08-21 | 2,100 | $9.38 | $20K |
| 2026-08-20 | 1,158 | $9.60 | $11K |
| 2026-08-19 | 1,955 | $8.72 | $17K |
| 2026-08-18 | 2,016 | $8.36 | $17K |
| 2026-08-17 | 1,603 | $8.09 | $13K |
| 2026-08-13 | 1,050 | $9.23 | $10K |
| 2026-08-12 | 1,017 | $8.94 | $9K |
| 2026-08-11 | 358 | $8.61 | $3K |
| 2026-08-06 | 1,748 | $8.54 | $15K |
| 2026-08-03 | 164 | $8.38 | $1K |
| 2026-07-29 | 2,312 | $7.81 | $18K |
| 2026-07-27 | 1,400 | $7.90 | $11K |
| 2026-07-24 | 1,731 | $8.17 | $14K |
| 2026-07-21 | 1,823 | $8.29 | $15K |
| 2026-07-15 | 4,081 | $8.04 | $33K |
| 2026-07-13 | 974 | $9.76 | $10K |
| 2026-07-08 | 5,649 | $10.26 | $58K |
| 2026-07-07 | 12,537 | $10.88 | $136K |
Insider trades
SEC Form 4, newest first. JSONOver the last 90 days ATRA insiders reported 1 open-market buy ($1000K) against 1 sell ($41K), so the dollar flow leans toward buying. Latest filing: Cherry Brian N (Director) on 2026-09-04.
| Date | Insider | Title | Type | Shares | Price | Value | Owned after |
|---|---|---|---|---|---|---|---|
| 2026-09-04 | Cherry Brian N | Director | Buy | 104K | $9.60 | $1000K | 166K |
| 2026-08-17 | Nguyen AnhCo | President and CEO | Sell | 5K | $8.08 | $41K | 133K |
| 2026-07-22 | Redmile Group, LLC | Director | Tax withholding | 60 | price not stated in the filing | not stated | 637K |
| 2026-07-22 | Redmile Group, LLC | Director | Exercise or conversion | 195K | price not stated in the filing | not stated | 637K |
| 2026-06-11 | Cherry Brian N | Director | Grant | 24K | $0.00 | $0 | 62K |
| 2026-06-09 | HEIDEN WILLIAM K | Director | Grant | 12K | $0.00 | $0 | 34K |
| 2026-06-09 | Fust Matthew K | Director | Grant | 12K | $0.00 | $0 | 30K |
| 2026-06-09 | Ciongoli Gregory Austin | Director, 10% owner, See Remarks | Grant | 12K | $0.00 | $0 | 12K |
| 2026-05-18 | Nguyen AnhCo | President and CEO | Sell | 5K | $9.13 | $48K | 138K |
| 2026-05-18 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 2K | $9.13 | $22K | 50K |
| 2026-05-07 | Panacea Innovation Ltd | 10% owner | Sell | 313K | $10.10 | $3.2M | 1.0M |
| 2026-05-07 | EcoR1 Capital, LLC | 10% owner | Buy | 507K | $9.35 | $4.7M | 1.6M |
| 2026-03-17 | Panacea Innovation Ltd | 10% owner | Tax withholding | 5 | $5.23 | $26 | 308K |
| 2026-03-17 | Panacea Innovation Ltd | 10% owner | Exercise or conversion | 259K | $0.00 | $26 | 308K |
| 2026-03-09 | Nguyen AnhCo | President and CEO | Grant | 81K | $0.00 | $0 | 143K |
| 2026-03-09 | Grant-Huerta Yanina | Chief Accounting Officer | Grant | 20K | $0.00 | $0 | 52K |
| 2026-03-02 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 100 | $5.08 | $508 | 32K |
| 2026-03-02 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 377 | $5.08 | $2K | 32K |
| 2026-03-02 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 2K | $5.08 | $8K | 32K |
| 2026-03-02 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 24 | $5.08 | $122 | 34K |
| 2026-03-02 | Nguyen AnhCo | President and CEO | Sell | 1K | $5.09 | $7K | 62K |
| 2026-03-02 | Nguyen AnhCo | President and CEO | Sell | 1K | $5.09 | $7K | 63K |
| 2026-03-02 | Nguyen AnhCo | President and CEO | Sell | 58 | $5.08 | $295 | 65K |
| 2026-03-02 | Nguyen AnhCo | President and CEO | Sell | 198 | $5.08 | $1K | 65K |
| 2026-01-12 | Huang James | Director,TenPercentOwner | Sell | 81K | $6.07 | $489K | 1.3M |
| 2026-01-12 | Panacea Innovation Ltd | 10% owner | Sell | 81K | $6.07 | $489K | 1.3M |
| 2025-11-28 | Panacea Innovation Ltd | 10% owner | Tax withholding | 1 | $14.03 | $14 | 49K |
| 2025-11-28 | Panacea Innovation Ltd | 10% owner | Exercise or conversion | 49K | $0.00 | $5 | 49K |
| 2025-11-17 | Nguyen AnhCo | President and CEO | Sell | 56 | $13.19 | $739 | 65K |
| 2025-11-17 | Nguyen AnhCo | President and CEO | Sell | 3K | $13.19 | $38K | 65K |
| 2025-11-17 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 74 | $13.19 | $976 | 33K |
| 2025-11-17 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 85 | $13.19 | $1K | 34K |
| 2025-11-17 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 2K | $13.19 | $22K | 34K |
| 2025-08-18 | Nguyen AnhCo | President and CEO | Sell | 2K | $11.62 | $19K | 68K |
| 2025-08-18 | Nguyen AnhCo | President and CEO | Sell | 1K | $11.62 | $15K | 70K |
| 2025-08-18 | Nguyen AnhCo | President and CEO | Sell | 57 | $11.61 | $662 | 71K |
| 2025-08-18 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 2K | $11.61 | $19K | 35K |
| 2025-08-18 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 86 | $11.61 | $999 | 37K |
| 2025-08-18 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 55 | $11.61 | $638 | 37K |
| 2025-08-15 | Panacea Innovation Ltd | 10% owner | Buy | 55K | $12.19 | $670K | 1.4M |
| 2025-07-17 | Huang James | Director,TenPercentOwner | Buy | 19K | $9.64 | $186K | 1.4M |
| 2025-07-17 | Panacea Innovation Ltd | 10% owner | Buy | 19K | $9.64 | $186K | 1.4M |
| 2025-06-10 | Gallagher Carol Giltner | Director | Grant | 8K | $0.00 | $0 | 33K |
| 2025-06-10 | Fust Matthew K | Director | Grant | 8K | $0.00 | $0 | 18K |
| 2025-06-10 | Touchon Pascal | Director | Grant | 8K | $0.00 | $0 | 78K |
| 2025-06-10 | Roncarolo Maria Grazia | Director | Grant | 8K | $0.00 | $0 | 17K |
| 2025-06-10 | MALLIK AMEET | Director | Grant | 8K | $0.00 | $0 | 17K |
| 2025-06-10 | HEIDEN WILLIAM K | Director | Grant | 8K | $0.00 | $0 | 22K |
| 2025-05-16 | Adiumentum Capital Fund I GP LLC | Director,TenPercentOwner,Other | Grant | 76K | $6.61 | $500K | 1.2M |
| 2025-05-16 | Nguyen AnhCo | President and CEO | Sell | 3K | $6.76 | $22K | 71K |
| 2025-05-16 | Grant-Huerta Yanina | Chief Accounting Officer | Sell | 2K | $6.76 | $15K | 37K |
| 2025-03-03 | Henrich Jill | EVP, Chief Regulatory Officer | Sell | 1K | $7.00 | $7K | 19K |
| 2025-03-03 | Hyllengren Eric J | EVP, CFO and COO | Sell | 1K | $7.00 | $8K | 56K |
| 2025-03-03 | Nguyen AnhCo | President and CEO | Sell | 3K | $7.00 | $23K | 74K |
| 2025-01-27 | Hyllengren Eric J | EVP, CFO and COO | Grant | 34K | $0.00 | $0 | 57K |
| 2024-11-18 | Nguyen AnhCo | President and CEO | Sell | 2K | $11.20 | $19K | 77K |
| 2024-11-18 | Hyllengren Eric J | EVP, CFO and COO | Sell | 1K | $11.20 | $15K | 23K |
| 2024-11-18 | Henrich Jill | EVP, Chief Regulatory Officer | Sell | 1K | $11.20 | $11K | 19K |
| 2024-09-09 | Nguyen AnhCo | President and CEO | Grant | 45K | $0.00 | $0 | 79K |
| 2024-08-16 | Henrich Jill | EVP, Global Head RA & Quality | Sell | 831 | $6.63 | $6K | 21K |
| 2024-08-16 | Henrich Jill | EVP, Global Head RA & Quality | Sell | 132 | $6.63 | $875 | 20K |
| 2024-08-16 | Hyllengren Eric J | EVP, CFO | Sell | 1K | $6.63 | $7K | 25K |
| 2024-08-16 | Hyllengren Eric J | EVP, CFO | Sell | 29 | $6.63 | $192 | 25K |
| 2024-08-16 | Murugan Amar | EVP, Chief Legal Officer | Sell | 192 | $6.63 | $1K | 27K |
| 2024-08-16 | Murugan Amar | EVP, Chief Legal Officer | Sell | 89 | $6.63 | $590 | 27K |
| 2024-08-16 | Murugan Amar | EVP, Chief Legal Officer | Sell | 877 | $6.63 | $6K | 27K |
| 2024-08-16 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 56 | $6.63 | $371 | 34K |
| 2024-08-16 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 1K | $6.63 | $10K | 34K |
| 2024-08-16 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 297 | $6.63 | $2K | 34K |
| 2024-08-16 | Touchon Pascal | President and CEO | Sell | 3K | $6.63 | $18K | 70K |
| 2024-08-16 | Touchon Pascal | President and CEO | Sell | 276 | $6.63 | $2K | 70K |
| 2024-05-16 | Henrich Jill | EVP, Global Head RA & Quality | Sell | 26K | $0.62 | $16K | 529K |
| 2024-05-16 | Hyllengren Eric J | EVP, CFO | Sell | 29K | $0.62 | $18K | 646K |
| 2024-05-16 | Murugan Amar | EVP, Chief Legal Officer | Sell | 32K | $0.62 | $20K | 695K |
| 2024-05-16 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 43K | $0.62 | $27K | 898K |
| 2024-05-16 | Touchon Pascal | President and CEO | Sell | 82K | $0.62 | $51K | 1.8M |
| 2024-03-31 | MALLIK AMEET | Director | Grant | 150K | $0.00 | $0 | 228K |
| 2024-03-31 | Gallagher Carol Giltner | Director | Grant | 150K | $0.00 | $0 | 630K |
| 2024-03-31 | Roncarolo Maria Grazia | Director | Grant | 150K | $0.00 | $0 | 239K |
| 2024-03-31 | HEIDEN WILLIAM K | Director | Grant | 150K | $0.00 | $0 | 359K |
| 2024-03-31 | Fust Matthew K | Director | Grant | 150K | $0.00 | $0 | 259K |
| 2024-03-04 | Henrich Jill | EVP, Global Head RA & Quality | Sell | 4K | $0.72 | $3K | 555K |
| 2024-03-04 | Hyllengren Eric J | EVP, CFO | Sell | 5K | $0.72 | $4K | 674K |
| 2024-03-04 | Hyllengren Eric J | EVP, CFO | Sell | 1K | $0.72 | $1K | 680K |
| 2024-03-04 | Murugan Amar | EVP, Chief Legal Officer | Sell | 10K | $0.72 | $7K | 728K |
| 2024-03-04 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 11K | $0.72 | $8K | 941K |
| 2024-03-04 | Touchon Pascal | President and CEO | Sell | 25K | $0.72 | $18K | 1.9M |
| 2024-01-08 | Henrich Jill | EVP, Global Head RA & Quality | Grant | 450K | $0.00 | $0 | 559K |
| 2024-01-08 | Hyllengren Eric J | EVP, CFO | Grant | 475K | $0.00 | $0 | 681K |
| 2024-01-08 | Murugan Amar | EVP, Chief Legal Officer | Grant | 475K | $0.00 | $0 | 738K |
| 2024-01-08 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Grant | 675K | $0.00 | $0 | 952K |
| 2024-01-08 | Touchon Pascal | President and CEO | Grant | 1.3M | $0.00 | $0 | 1.9M |
| 2023-11-16 | Henrich Jill | EVP, Global Head RA & Quality | Sell | 3K | $0.39 | $1K | 104K |
| 2023-11-16 | Hyllengren Eric J | SVP, CFO | Sell | 12K | $0.39 | $5K | 206K |
| 2023-11-16 | Joshi Manher | EVP, Chief Medical Officer | Sell | 12K | $0.39 | $5K | 171K |
| 2023-11-16 | Murugan Amar | EVP, Chief Legal Officer | Sell | 8K | $0.39 | $3K | 257K |
| 2023-11-16 | Nguyen AnhCo | EVP, Chief Sci. & Tech Officer | Sell | 9K | $0.39 | $3K | 277K |
| 2023-11-16 | Touchon Pascal | President and CEO | Sell | 20K | $0.39 | $8K | 655K |
| 2023-11-14 | Gallagher Carol Giltner | Director | Buy | 91K | $0.31 | $28K | 459K |
| 2023-11-13 | Gallagher Carol Giltner | Director | Buy | 179K | $0.22 | $39K | 368K |
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.
Planned sales (Form 144)
Newest first. JSON9 Form 144 notices on file for ATRA worth $3.6M at the prices reported; 1 in the last 90 days worth $42K. Latest: Nguyen AnhCo filed on 2026-08-26 to sell 5,062 shares ($42K) from 2026-08-17.
| Filed | Seller | Shares | Market value | Of outstanding | Sale from | Broker |
|---|---|---|---|---|---|---|
| 2026-08-26 | Nguyen AnhCoDirector, Officer | 5K | $42K | 0.050% | 2026-08-17 | Morgan Stanley Smith Barney LLC |
| 2026-05-18 | Nguyen AnhCoDirector, Officer | 6K | $63K | 0.064% | 2026-05-18 | Morgan Stanley Smith Barney LLC |
| 2026-05-18 | Grant-Huerta YaninaOfficer | 3K | $29K | 0.029% | 2026-05-18 | Morgan Stanley Smith Barney LLC |
| 2026-05-07 | Panacea Innovation Ltd10% Stockholder | 313K | $3.2M | 3.833% | 2026-05-07 | Cantor Fitzgerald |
| 2026-03-02 | Nguyen AnhCoDirector, Officer | 3K | $18K | 0.046% | 2026-03-02 | Morgan Stanley Smith Barney LLC |
| 2026-03-02 | Grant-Huerta YaninaOfficer | 2K | $13K | 0.032% | 2026-03-02 | Morgan Stanley Smith Barney LLC |
| 2026-01-12 | Panacea Innovation Ltd10% Stockholder | 40K | $235K | 0.555% | 2026-01-12 | Cantor Fitzgerald |
| 2025-11-17 | Nguyen AnhCoDirector, Officer | 3K | $46K | 0.046% | 2025-11-17 | Morgan Stanley Smith Barney LLC |
| 2025-11-17 | Grant-Huerta YaninaOfficer | 2K | $28K | 0.029% | 2025-11-17 | Morgan Stanley Smith Barney LLC |
Large holders (13D and 13G)
One row per reporting person with its latest filing, newest first. JSON17 holders report 5% or more of ATRA in their latest filing, 8 on Schedule 13D (active intent). The largest reported stake is EcoR1 Capital, LLC at 17.4% of the class (1,552,000 shares), filed 2026-05-07 for an event on 2026-05-07.
| Filed | Form | Holder | Shares | Of class | Event |
|---|---|---|---|---|---|
| 2026-08-14 | 13G/Ano. 1 | Point72 Asset Management, L.P.partnership | 688K | 7.6% | 2026-06-30 |
| 2026-08-14 | 13G/Ano. 1 | Steven A. Cohenindividual | 688K | 7.6% | 2026-06-30 |
| 2026-08-14 | 13G/Ano. 1 | Point72 Capital Advisors, Inc.corporation | 688K | 7.6% | 2026-06-30 |
| 2026-07-24 | 13D/Ano. 3 | Redmile Group, LLCinvestment adviser, other entity | 951K | 9.9% | 2026-07-22 |
| 2026-07-24 | 13D/Ano. 3 | Green Jeremyindividual, parent holding company | 951K | 9.9% | 2026-07-22 |
| 2026-07-24 | 13D/Ano. 3 | Redmile Biopharma Investments II, L.P.partnership | 631K | 6.6% | 2026-07-22 |
| 2026-07-24 | 13D/Ano. 3 | Redmile Strategic Long Only Trading Sub, Ltd.corporation | 402K | 4.2% | 2026-07-22 |
| 2026-05-14 | 13D/Ano. 2 | Jeremy C. Greenindividual, parent holding company | 951K | 9.9% | 2026-05-12 |
| 2026-05-13 | 13G | Adage Capital Management, L.P.investment adviser, partnership | 700K | 8.6% | 2026-03-31 |
| 2026-05-13 | 13G | Robert Atchinsonparent holding company, individual | 700K | 8.6% | 2026-03-31 |
| 2026-05-13 | 13G | Phillip Grossparent holding company, individual | 700K | 8.6% | 2026-03-31 |
| 2026-05-11 | 13D/Ano. 3 | James Huangindividual | 1.3M | 16.1% | 2026-05-07 |
| 2026-05-11 | 13D/Ano. 3 | Panacea Innovation Limitedcorporation | 1.3M | 16.1% | 2026-05-07 |
| 2026-05-11 | 13D/Ano. 3 | Panacea Venture Healthcare Fund II GP Company, Ltd.corporation | 1.0M | 12.4% | 2026-05-07 |
| 2026-05-11 | 13D/Ano. 3 | Panacea Venture Healthcare Fund II, L.P.partnership | 1.0M | 12.4% | 2026-05-07 |
| 2026-05-11 | 13D/Ano. 3 | Panacea Opportunity Fund I GP Company, Ltd.corporation | 308K | 3.8% | 2026-05-07 |
| 2026-05-11 | 13D/Ano. 3 | Panacea Opportunity Fund I, L.P.partnership | 308K | 3.8% | 2026-05-07 |
| 2026-05-07 | 13G/Ano. 3 | EcoR1 Capital, LLCinvestment adviser, other entity | 1.6M | 17.4% | 2026-05-07 |
| 2026-05-07 | 13G/Ano. 3 | Oleg Nodelmanparent holding company, individual | 1.6M | 17.4% | 2026-05-07 |
| 2026-05-07 | 13G/Ano. 3 | EcoR1 Capital Fund Qualified, L.P.partnership | 1.4M | 16.2% | 2026-05-07 |
| 2025-11-14 | 13D/Ano. 1 | RedCo I, L.P.partnership | 347K | 4.7% | 2025-11-12 |
13F holders
Tracked managers holding ATRA at their latest 13F. JSON3 of the 30 tracked managers held ATRA at their latest 13F, $8.2M in total at quarter-end prices. Point72 Asset Management is the largest at $7.9M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 2 added shares and 1 cut.
| Fund | Quarter | Shares | Value | Of portfolio | Change in shares |
|---|---|---|---|---|---|
| Point72 Asset Management | 2026-06-30 | 688K | $7.9M | 0.01% | +493K |
| Millennium Management | 2026-06-30 | 13K | $146K | 0.00% | -35K |
| Citadel Advisors | 2026-06-30 | 10K | $117K | 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
Atara Biotherapeutics 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 Atara Biotherapeutics (ATRA), SEC CIK 1604464, listed on Nasdaq, classified by the SEC as biological products, (no diagnostic substances). 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 2026-10-14.JSON and CSV
- Planned sales
- SEC EDGAR Form 144Source: SEC.New notices appear shortly after the SEC posts them; a notice is filed on or before the sale. Latest 2026-08-26.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 2026-08-14.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 2026-08-12.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 2026-09-04.JSON and CSV
- Company record
- EDGAR filing index for CIK 1604464Ticker, 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 biological products, (no diagnostic substances)
Other company pages
Datasets
Frequently Asked Questions
How much of ATRA is sold short?
350,260 shares were held short at the 2026-10-15 settlement, 8.7 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 ATRA's daily short volume?
On 2026-11-03, 2,285 of the 3,202 ATRA shares reported to FINRA were sold short, 71.4% of the day's reported volume. Short volume is a flow for one day, not a position.
Does ATRA have fails to deliver?
The SEC's latest file shows 2,836 ATRA shares failed to deliver at settlement 2026-10-14. Fails are reported per settlement date and published twice a month with a lag.
Are ATRA insiders buying or selling?
Over the last 90 days ATRA insiders reported 1 open-market buy ($1000K) against 1 sell ($41K), so the dollar flow leans toward buying. Latest filing: Cherry Brian N (Director) on 2026-09-04.
Have ATRA insiders filed to sell?
9 Form 144 notices on file for ATRA worth $3.6M at the prices reported; 1 in the last 90 days worth $42K. Latest: Nguyen AnhCo filed on 2026-08-26 to sell 5,062 shares ($42K) from 2026-08-17.
Who owns 5% or more of ATRA?
17 holders report 5% or more of ATRA in their latest filing, 8 on Schedule 13D (active intent). The largest reported stake is EcoR1 Capital, LLC at 17.4% of the class (1,552,000 shares), filed 2026-05-07 for an event on 2026-05-07.
Which tracked 13F managers own ATRA?
3 of the 30 tracked 13F managers held ATRA shares at their latest filing, $8.2M in all. The largest: Steve Cohen's Point72 Asset Management (688K shares, $7.9M), Izzy Englander's Millennium Management (13K shares, $146K), Ken Griffin's Citadel Advisors (10K shares, $117K).
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.