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Atara Biotherapeutics, Inc.

ATRA
Exchange
Nasdaq
Industry
Biological Products, (No Diagnostic Substances)
SEC CIK
0001604464

In the last 90 days, Atara Biotherapeutics, Inc. insiders filed 1 open-market purchase and 1 sale; 36 institutions reported holding it in 13F filings for Q2 2026, worth $51.3M in total; no superinvestor holds it.

Four kinds of short-selling data, each measuring something different:

  • Short interest: shares sold short and not yet bought back, as of a settlement date. FINRA publishes it twice a month, about eight business days after the settlement date.
  • Daily short volume: shares sold short each day in off-exchange trades reported to FINRA. It counts trades, not open positions, and is published the next day.
  • Fails-to-deliver: shares not delivered by the settlement date. The SEC publishes them twice a month, about two weeks late.
  • ATS (dark pool) volume: weekly volume on alternative trading systems and other off-exchange venues. FINRA publishes it two to four weeks after the week.

More in the glossary.

Short interest

Shares sold short and not yet bought back, from FINRA, on every settlement date in the last two years.

Short interest
296.7K
Shares, settlement Oct 30, 2026
Change
−53.6K
−15.3% vs. Oct 15, 2026
Days to cover
13.43
Short interest ÷ average daily volume
Average daily volume
22.1K
Shares, as reported by FINRA
Short interest by settlement date
Oct 31, 2024: 636,280 sharesNov 15, 2024: 519,528 sharesNov 29, 2024: 543,952 sharesDec 13, 2024: 551,465 sharesDec 31, 2024: 533,616 sharesJan 15, 2025: 547,760 sharesJan 31, 2025: 706,465 sharesFeb 14, 2025: 674,628 sharesFeb 28, 2025: 715,084 sharesMar 14, 2025: 723,264 sharesMar 31, 2025: 666,785 sharesApr 15, 2025: 662,188 sharesApr 30, 2025: 522,139 sharesMay 15, 2025: 412,857 sharesMay 30, 2025: 367,405 sharesJun 13, 2025: 285,774 sharesJun 30, 2025: 266,647 sharesJul 15, 2025: 268,036 sharesJul 31, 2025: 210,641 sharesAug 15, 2025: 196,215 sharesAug 29, 2025: 173,825 sharesSep 15, 2025: 161,507 sharesSep 30, 2025: 149,590 sharesOct 15, 2025: 128,849 sharesOct 31, 2025: 168,549 sharesNov 14, 2025: 176,777 sharesNov 28, 2025: 164,713 sharesDec 15, 2025: 166,856 sharesDec 31, 2025: 169,201 sharesJan 15, 2026: 1,016,616 sharesJan 30, 2026: 282,525 sharesFeb 13, 2026: 209,287 sharesFeb 27, 2026: 330,524 sharesMar 13, 2026: 313,290 sharesMar 31, 2026: 327,066 sharesApr 15, 2026: 317,953 sharesApr 30, 2026: 306,093 sharesMay 15, 2026: 546,470 sharesMay 29, 2026: 484,391 sharesJun 15, 2026: 492,405 sharesJun 30, 2026: 361,520 sharesJul 15, 2026: 577,635 sharesJul 31, 2026: 536,897 sharesAug 14, 2026: 477,268 sharesAug 31, 2026: 427,435 sharesSep 15, 2026: 404,270 sharesSep 30, 2026: 321,792 sharesOct 15, 2026: 350,260 sharesOct 30, 2026: 296,651 shares
Short interest in ATRA by settlement date
Settlement dateShort interestChangeChange %Avg. daily volumeDays to cover
Oct 30, 2026296.7K−53.6K−15.3%22.1K13.43
Oct 15, 2026350.3K+28.5K+8.9%40.3K8.70
Sep 30, 2026321.8K−82.5K−20.4%39.7K8.11
Sep 15, 2026404.3K−23.2K−5.4%55.1K7.34
Aug 31, 2026427.4K−49.8K−10.4%38.6K11.07
Aug 14, 2026477.3K−59.6K−11.1%51.8K9.21
Jul 31, 2026536.9K−40.7K−7.1%57.2K9.39
Jul 15, 2026577.6K+216.1K+59.8%92.5K6.24
Jun 30, 2026361.5K−130.9K−26.6%91.5K3.95
Jun 15, 2026492.4K+8.01K+1.7%78.6K6.27
May 29, 2026484.4K−62.1K−11.4%166.2K2.91
May 15, 2026546.5K+240.4K+78.5%7.39M1.00
Apr 30, 2026306.1K−11.9K−3.7%50.1K6.10
Apr 15, 2026318.0K−9.11K−2.8%77.6K4.10
Mar 31, 2026327.1K+13.8K+4.4%108.6K3.01
Mar 13, 2026313.3K−17.2K−5.2%864.9K1.00
Feb 27, 2026330.5K+121.2K+57.9%155.0K2.13
Feb 13, 2026209.3K−73.2K−25.9%87.2K2.40
Jan 30, 2026282.5K−734.1K−72.2%351.0K1.00
Jan 15, 20261.02M+847.4K+500.8%1.10M1.00
Dec 31, 2025169.2K+2.35K+1.4%66.2K2.56
Dec 15, 2025166.9K+2.14K+1.3%82.9K2.01
Nov 28, 2025164.7K−12.1K−6.8%59.0K2.79
Nov 14, 2025176.8K+8.23K+4.9%74.6K2.37
Oct 31, 2025168.5K+39.7K+30.8%45.4K3.72
Oct 15, 2025128.8K−20.7K−13.9%61.1K2.11
Sep 30, 2025149.6K−11.9K−7.4%59.7K2.51
Sep 15, 2025161.5K−12.3K−7.1%46.0K3.51
Aug 29, 2025173.8K−22.4K−11.4%55.1K3.16
Aug 15, 2025196.2K−14.4K−6.9%44.7K4.39
Jul 31, 2025210.6K−57.4K−21.4%86.1K2.45
Jul 15, 2025268.0K+1.39K+0.5%35.1K7.64
Jun 30, 2025266.6K−19.1K−6.7%37.0K7.21
Jun 13, 2025285.8K−81.6K−22.2%59.3K4.82
May 30, 2025367.4K−45.5K−11.0%76.6K4.80
May 15, 2025412.9K−109.3K−20.9%71.7K5.75
Apr 30, 2025522.1K−140.0K−21.2%39.0K13.38
Apr 15, 2025662.2K−4.60K−0.7%54.6K12.12
Mar 31, 2025666.8K−56.5K−7.8%49.2K13.54
Mar 14, 2025723.3K+8.18K+1.1%59.1K12.23
Feb 28, 2025715.1K+40.5K+6.0%81.4K8.78
Feb 14, 2025674.6K−31.8K−4.5%121.0K5.58
Jan 31, 2025706.5K+158.7K+29.0%616.6K1.15
Jan 15, 2025547.8K+14.1K+2.7%233.8K2.34
Dec 31, 2024533.6K−17.8K−3.2%95.0K5.62
Dec 13, 2024551.5K+7.51K+1.4%80.6K6.85
Nov 29, 2024544.0K+24.4K+4.7%79.9K6.81
Nov 15, 2024519.5K−116.8K−18.4%177.1K2.93
Oct 31, 2024636.3K−2.88K−0.5%100.5K6.33

Fails-to-deliver

Shares that weren't delivered by the settlement date, from the SEC, for the last 30 dates with fails. The price is the previous day's closing price published by the SEC.

Fails-to-deliver in ATRA by settlement date
Settlement dateSharesPriceValue
Oct 14, 20262,836$9.31$26.4K
Oct 13, 20261,707$9.38$16.0K
Oct 8, 2026216$9.37$2.02K
Oct 6, 2026283$9.40$2.66K
Oct 5, 20263,180$9.48$30.1K
Oct 1, 20261,735$8.50$14.7K
Sep 29, 2026194$8.37$1.62K
Sep 28, 20263,906$8.81$34.4K
Sep 24, 2026828$8.56$7.09K
Sep 17, 20262,316$10.11$23.4K
Sep 8, 2026805$9.76$7.86K
Sep 1, 20261,255$8.90$11.2K
Aug 21, 20262,100$9.38$19.7K
Aug 20, 20261,158$9.60$11.1K
Aug 19, 20261,955$8.72$17.0K
Aug 18, 20262,016$8.36$16.9K
Aug 17, 20261,603$8.09$13.0K
Aug 13, 20261,050$9.23$9.69K
Aug 12, 20261,017$8.94$9.09K
Aug 11, 2026358$8.61$3.08K
Aug 6, 20261,748$8.54$14.9K
Aug 3, 2026164$8.38$1.37K
Jul 29, 20262,312$7.81$18.1K
Jul 27, 20261,400$7.90$11.1K
Jul 24, 20261,731$8.17$14.1K
Jul 21, 20261,823$8.29$15.1K
Jul 15, 20264,081$8.04$32.8K
Jul 13, 2026974$9.76$9.51K
Jul 8, 20265,649$10.26$58.0K
Jul 7, 202612,537$10.88$136.4K

Daily short volume

Off-exchange short-sale volume, not short interest: shares sold short each day in trades reported to FINRA, for the last 30 trading days.

The short volume ratio isn't a sentiment gauge: market makers sell short to fill buy orders and to hedge, so short sales are usually about half of off-exchange volume.

Off-exchange short volume in ATRA by trade date
Trade dateShort volumeShort exemptOff-exchange volumeShort volume ratio
Nov 13, 20261,08902,35346.3%
Nov 12, 20261,42903,86037.0%
Nov 11, 20261,0122001,95451.8%
Nov 10, 20263,07204,21073.0%
Nov 9, 20261,30505,54723.5%
Nov 6, 20261,32406,77119.6%
Nov 5, 20264,028249,48542.5%
Nov 4, 202659191,05656.0%
Nov 3, 20262,28503,20271.4%
Nov 2, 20264,690111,44441.0%
Oct 30, 20265,134013,83037.1%
Oct 29, 20262,255906,25036.1%
Oct 28, 20263,18305,18261.4%
Oct 27, 20261,71402,08882.1%
Oct 26, 20266,780013,29851.0%
Oct 23, 20261,46506,04924.2%
Oct 22, 20261,36503,68037.1%
Oct 21, 202697802,59637.7%
Oct 20, 20261,24804,15730.0%
Oct 19, 20261,37202,77049.5%
Oct 16, 202688801,98044.8%
Oct 15, 20262,702345,13352.6%
Oct 14, 20262,195010,06621.8%
Oct 13, 202611,020012,12490.9%
Oct 12, 20262,544015,16316.8%
Oct 9, 20261,69204,97634.0%
Oct 8, 20261,10503,69029.9%
Oct 7, 20261,31804,44429.7%
Oct 6, 20263,039011,35726.8%
Oct 5, 20267,947015,65550.8%

ATS (dark pool) volume

Weekly volume on alternative trading systems (ATS) and other off-exchange (OTC) venues, from FINRA, for the last 12 weeks. ATS share is ATS volume ÷ (ATS + OTC volume), not a share of all trading.

Weekly ATS and OTC volume in ATRA
Week ofTierATS sharesATS tradesOther OTC sharesOther OTC tradesATS share
Oct 5, 2026T212,05997232,56253727.0%
Sep 28, 2026T285,8871,51848,87663863.7%
Sep 21, 2026T223,76793722,96959250.9%
Sep 14, 2026T251,6981,84228,13196064.8%
Sep 7, 2026T220,6711,21861,11576025.3%
Aug 31, 2026T221,8501,094135,21539313.9%
Aug 24, 2026T216,29373248,7141,18625.1%
Aug 17, 2026T229,6411,02753,12249435.8%
Aug 10, 2026T245,73997375,10072837.9%
Aug 3, 2026T229,77583137,44376844.3%
Jul 27, 2026T247,0331,27657,64583944.9%
Jul 20, 2026T245,2491,05665,8291,58240.7%