XOOMAR

Atara Biotherapeutics, Inc. (ATRA)

Every FINRA and SEC series the site collects for Atara Biotherapeutics, Inc.: short interest with days to cover, daily short sale volume, fails to deliver and Form 4 insider trades. Listed on Nasdaq.

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477K

Short interest

settlement 2026-08-14

9.2

Days to cover

-11.1% vs prior

45.4%

Short share of volume

2026-09-11

1,050

Fails to deliver

settlement 2026-08-13

$959K

Insider flow, 90 days

1 buys, 1 sells

As of 2026-09-11.

Short interest

FINRA, twice a month; the last 12 months shown, all 48 settlements in the JSON

As of 14 August 2026, short interest in ATRA is 477,268 shares, down 100,367 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 52K shares a day that is 9.2 days to cover, elevated.

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SettlementShares shortChangeAvg daily volumeDays to cover
2026-08-14477,268-11.1%51,8429.21
2026-07-31536,897-7.0%57,1669.39
2026-07-15577,635+59.8%92,5306.24
2026-06-30361,520-26.6%91,5053.95
2026-06-15492,405+1.6%78,5546.27
2026-05-29484,391-11.4%166,2372.91
2026-05-15546,470+78.5%7,386,4371.00
2026-04-30306,093-3.7%50,1426.10
2026-04-15317,953-2.8%77,6344.10
2026-03-31327,066+4.4%108,6353.01
2026-03-13313,290-5.2%864,9011.00
2026-02-27330,524+57.9%155,0182.13
2026-02-13209,287-25.9%87,2282.40
2026-01-30282,525-72.2%351,0291.00
2026-01-151,016,616+500.8%1,101,0871.00
2025-12-31169,201+1.4%66,1782.56
2025-12-15166,856+1.3%82,9052.01
2025-11-28164,713-6.8%58,9562.79
2025-11-14176,777+4.9%74,5882.37
2025-10-31168,549+30.8%45,3573.72
2025-10-15128,849-13.9%61,1422.11
2025-09-30149,590-7.4%59,7072.51
2025-09-15161,507-7.1%45,9513.51
2025-08-29173,825-11.4%55,0873.16

Daily short volume

FINRA Reg SHO, last 60 sessions. JSON

As of 11 September 2026, the short share of ATRA volume is 45.4%, down 37.4 points over the last five sessions. Over the last 52 readings it ranged from 3.0% (4 September 2026) to 82.8% (3 September 2026). The latest reading is 3.2 points below the 30-session average of 48.6%, on 6K shares reported.

DateShort volumeTotal volumeShort shareExempt
2026-09-113K6K45.4%0
2026-09-102K8K28.2%1
2026-09-0913K37K34.9%0
2026-09-0815K29K51.5%42
2026-09-043K111K3.0%0
2026-09-038K10K82.8%0
2026-09-023K5K56.1%0
2026-09-0111K21K54.4%0
2026-08-313K9K32.7%0
2026-08-283K4K67.4%0
2026-08-273K9K38.2%0
2026-08-2612K25K48.0%0
2026-08-259K19K45.9%0
2026-08-245K8K68.7%0
2026-08-212K10K18.7%0
2026-08-203K10K29.3%0
2026-08-1914K25K54.4%0
2026-08-185K8K64.0%0
2026-08-1721K28K73.1%11,663
2026-08-144K13K32.8%361
2026-08-1311K39K29.0%2,754
2026-08-1221K36K57.4%0
2026-08-117K9K80.5%0
2026-08-109K21K39.9%0
2026-08-074K8K55.9%0
2026-08-064K7K53.4%0
2026-08-057K12K57.4%0
2026-08-048K18K43.2%0
2026-08-039K22K41.7%0
2026-07-319K13K69.5%0

Fails to deliver

SEC, by settlement date. JSON

As of 13 August 2026, the fails-to-deliver balance in ATRA is 1,050 shares, up 33 shares over the last settlement date. Over the last 52 readings it ranged from 83 shares (18 March 2026) to 33,902 shares (10 March 2026). The latest reading sits at the bottom of that range.

SettlementShares failedPriceValue
2026-08-131,050$9.23$10K
2026-08-121,017$8.94$9K
2026-08-11358$8.61$3K
2026-08-061,748$8.54$15K
2026-08-03164$8.38$1K
2026-07-292,312$7.81$18K
2026-07-271,400$7.90$11K
2026-07-241,731$8.17$14K
2026-07-211,823$8.29$15K
2026-07-154,081$8.04$33K
2026-07-13974$9.76$10K
2026-07-085,649$10.26$58K
2026-07-0712,537$10.88$136K
2026-07-0211,929$11.37$136K
2026-07-011,400$11.48$16K
2026-06-301,000$11.17$11K
2026-06-291,826$10.51$19K
2026-06-267,404$10.22$76K
2026-06-25505$10.55$5K
2026-06-231,147$10.61$12K
2026-06-225,339$10.07$54K
2026-06-186,788$9.67$66K
2026-06-17236$9.62$2K
2026-06-161,142$9.96$11K
2026-06-12277$10.46$3K
2026-06-11344$9.86$3K
2026-06-10456$9.77$4K
2026-06-09612$9.58$6K
2026-06-082,480$9.92$25K
2026-06-021,438$10.28$15K

Insider trades

SEC Form 4, newest first. JSON

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 on 2026-09-04.

DateInsiderTitleTypeSharesPriceValueOwned after
2026-09-04Cherry Brian Nn/aBuy104K$9.60$1000K166K
2026-08-17Nguyen AnhCoPresident and CEOSell5K$8.08$41K133K
2026-06-11Cherry Brian Nn/aGrant24K$0.00$062K
2026-06-09HEIDEN WILLIAM Kn/aGrant12K$0.00$034K
2026-06-09Fust Matthew Kn/aGrant12K$0.00$030K
2026-06-09Ciongoli Gregory Austinn/aGrant12K$0.00$012K
2026-05-18Nguyen AnhCoPresident and CEOSell5K$9.13$48K138K
2026-05-18Grant-Huerta YaninaChief Accounting OfficerSell2K$9.13$22K50K
2026-05-07Panacea Innovation Ltdn/aSell313K$10.10$3.2M1.0M
2026-05-07EcoR1 Capital, LLCn/aBuy507K$9.35$4.7M1.6M
2026-03-17Panacea Innovation Ltdn/aTax withholding5$5.23$26308K
2026-03-17Panacea Innovation Ltdn/aOption exercise259K$0.00$26308K
2026-03-09Nguyen AnhCoPresident and CEOGrant81K$0.00$0143K
2026-03-09Grant-Huerta YaninaChief Accounting OfficerGrant20K$0.00$052K
2026-03-02Grant-Huerta YaninaChief Accounting OfficerSell100$5.08$50832K
2026-03-02Grant-Huerta YaninaChief Accounting OfficerSell377$5.08$2K32K
2026-03-02Grant-Huerta YaninaChief Accounting OfficerSell2K$5.08$8K32K
2026-03-02Grant-Huerta YaninaChief Accounting OfficerSell24$5.08$12234K
2026-03-02Nguyen AnhCoPresident and CEOSell1K$5.09$7K62K
2026-03-02Nguyen AnhCoPresident and CEOSell1K$5.09$7K63K
2026-03-02Nguyen AnhCoPresident and CEOSell58$5.08$29565K
2026-03-02Nguyen AnhCoPresident and CEOSell198$5.08$1K65K
2026-01-12Panacea Innovation Ltdn/aSell81K$6.07$489K1.3M
2025-11-28Panacea Innovation Ltdn/aTax withholding1$14.03$1449K
2025-11-28Panacea Innovation Ltdn/aOption exercise49K$0.00$549K
2025-11-17Nguyen AnhCoPresident and CEOSell56$13.19$73965K
2025-11-17Nguyen AnhCoPresident and CEOSell3K$13.19$38K65K
2025-11-17Grant-Huerta YaninaChief Accounting OfficerSell74$13.19$97633K
2025-11-17Grant-Huerta YaninaChief Accounting OfficerSell85$13.19$1K34K
2025-11-17Grant-Huerta YaninaChief Accounting OfficerSell2K$13.19$22K34K
2025-08-18Nguyen AnhCoPresident and CEOSell2K$11.62$19K68K
2025-08-18Nguyen AnhCoPresident and CEOSell1K$11.62$15K70K
2025-08-18Nguyen AnhCoPresident and CEOSell57$11.61$66271K
2025-08-18Grant-Huerta YaninaChief Accounting OfficerSell2K$11.61$19K35K
2025-08-18Grant-Huerta YaninaChief Accounting OfficerSell86$11.61$99937K
2025-08-18Grant-Huerta YaninaChief Accounting OfficerSell55$11.61$63837K
2025-08-15Panacea Innovation Ltdn/aBuy55K$12.19$670K1.4M
2025-07-17Panacea Innovation Ltdn/aBuy19K$9.64$186K1.4M
2025-06-10Gallagher Carol Giltnern/aGrant8K$0.00$033K
2025-06-10Fust Matthew Kn/aGrant8K$0.00$018K
2025-06-10Touchon Pascaln/aGrant8K$0.00$078K
2025-06-10Roncarolo Maria Grazian/aGrant8K$0.00$017K
2025-06-10MALLIK AMEETn/aGrant8K$0.00$017K
2025-06-10HEIDEN WILLIAM Kn/aGrant8K$0.00$022K

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 the rarer, stronger signal.

Planned sales (Form 144)

Newest first. JSON

1 Form 144 notice on file for ATRA worth $42K 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.

FiledSellerSharesMarket valueOf outstandingSale fromBroker
2026-08-26Nguyen AnhCoDirector, Officer5K$42K0.050%2026-08-17Morgan Stanley Smith Barney LLC

Large holders (13D and 13G)

One row per reporting person, newest filing first. JSON

4 holders above 5% have filed on ATRA, 4 on Schedule 13D (active intent). The largest reported stake is Redmile Group, LLC at 9.9% of the class (950,994 shares), filed 2026-07-24 for an event on 2026-07-22.

FiledFormHolderSharesOf classEvent
2026-07-2413D/Ano. 3Redmile Group, LLCinvestment adviser, other entity951K9.9%2026-07-22
2026-07-2413D/Ano. 3Green Jeremyindividual, parent holding company951K9.9%2026-07-22
2026-07-2413D/Ano. 3Redmile Biopharma Investments II, L.P.partnership631K6.6%2026-07-22
2026-07-2413D/Ano. 3Redmile Strategic Long Only Trading Sub, Ltd.corporation402K4.2%2026-07-22

13F holders

Tracked managers holding ATRA at their latest 13F. JSON

3 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 1 added shares and 2 cut.

FundQuarterSharesValueOf portfolioChange in shares
Point72 Asset Management2026-06-30688K$7.9M0.01%+493K
Millennium Management2026-06-3013K$146K0.00%-35K
Citadel Advisors2026-06-3010K$117K0.00%-5K

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, Inc. 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 pulls every series the site collects for one ticker onto one URL, keyed by the SEC's own ticker list, 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 summary sentence built from the rows (last value, change, range with dates) and its own JSON and CSV links. Nothing on the page is written by a model; the sentences change only when the data does. A page exists only for companies with data in at least two series, and every section says when its source last updated.

This page follows Atara Biotherapeutics, Inc. (ATRA), SEC CIK 1604464, listed on Nasdaq. The cross-market tables live on the short interest and insider transactions hubs.

Source and method

Short interest
FINRA consolidated short interestTwice a month, about eight business days after settlement. Latest 2026-08-14.JSON and CSV
Daily short volume
FINRA Reg SHO daily filesEvery trading day, loaded the following morning. Latest 2026-09-11.JSON and CSV
Fails to deliver
SEC fails-to-deliver dataTwice a month, a few weeks after the half month ends. Latest 2026-08-13.JSON and CSV
Planned sales
SEC EDGAR Form 144EDGAR read every 30 minutes; a notice is filed on or before the sell order. Latest 2026-08-26.JSON and CSV
Large holders
SEC EDGAR Schedule 13D and 13GEDGAR read every 30 minutes; 13D within five business days of crossing 5%, 13G on the passive schedule. Latest 2026-07-24.JSON and CSV
13F holders
SEC EDGAR Form 13F-HRQuarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
Insider trades
SEC EDGAR Form 4EDGAR read every 30 minutes; filings are 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
30 requests a minute without a key, 120 a minute with a key from a free account.

Data checks. Every dataset is checked against its source once a day. This dataset passed the last run, 13 Sep 05:40 UTC.

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 crowded short are the combination that has historically preceded squeezes; insider sells next to a crowded short 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 company pages

Datasets

Frequently Asked Questions

How much of ATRA is sold short?
477,268 shares were held short at the 2026-08-14 settlement, 9.2 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 2026-09-11, 2,794 of the 6,155 ATRA shares reported to FINRA were sold short, 45.4% 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 1,050 ATRA shares failed to deliver at settlement 2026-08-13. 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 on 2026-09-04.
Have ATRA insiders filed to sell?
1 Form 144 notice on file for ATRA worth $42K 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 more than 5% of ATRA?
4 holders above 5% have filed on ATRA, 4 on Schedule 13D (active intent). The largest reported stake is Redmile Group, LLC at 9.9% of the class (950,994 shares), filed 2026-07-24 for an event on 2026-07-22.
Which funds hold ATRA?
3 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 1 added shares and 2 cut.

Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.