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EcoR1 Capital’s Atara Biotherapeutics ATRA Stock Holding History

EcoR1 Capital’s Portfolio ATRA Stock Details ATRA Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$17.8M Buy
1,552,000
+1,452,407
+1,458% +$11.6M 0.87% 18
2026
Q1 		$471K Sell
99,593
-473,590
-83% -$2.89M 0.02% 29
2025
Q4 		$10.4M Hold
573,183
– – 0.47% 22
2025
Q3 		$8.21M Hold
573,183
– – 0.39% 24
2025
Q2 		$4.42M Hold
573,183
– – 0.26% 32
2025
Q1 		$3.4M Buy
573,183
+41,049
+8% +$358K 0.2% 33
2024
Q4 		$7.08M Buy
532,134
+63,196
+13% +$666K 0.27% 41
2024
Q3 		$3.81M Buy
468,938
+62,259
+15% +$533K 0.13% 49
2024
Q2 		$3.46M Sell
406,679
-3
-0% -$45 0.11% 48
2024
Q1 		$7.06M Buy
406,682
+4,000
+1% +$71K 0.18% 48
2023
Q4 		$5.16M Buy
+402,682
New +$9.39M 0.13% 38
2017
Q2 		– Sell
-17,392
Closed -$8.94M – 37
2017
Q1 		$8.94M Buy
17,392
+8,760
+101% +$3.63M 2.26% 12
2016
Q4 		$3.06M Buy
+8,632
New +$3.65M 0.98% 17
2015
Q4 		– Sell
-32,138
Closed -$25.3M – 32
2015
Q3 		$25.3M Sell
32,138
-10,390
-24% -$12.7M 11.5% 2
2015
Q2 		$56.1M Hold
42,528
– – 18.7% 1
2015
Q1 		$44.2M Buy
42,528
+27,123
+176% +$17.9M 14.73% 1
2014
Q4 		$10.1M Buy
+15,405
New +$9.41M 5.13% 8

Other funds holding ATRA

Adage Capital Partners
Adage Capital Partners Boston, Massachusetts $71.3B AUM 56.8% 1-Year Est. Return
Point72 Asset Management
Point72 Asset Management Stamford, Connecticut $90.7B AUM 77.13% 1-Year Est. Return
RG
Redmile Group San Francisco, California $1.49B AUM 208.7% 1-Year Est. Return
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Mackenzie Financial
Mackenzie Financial Toronto Ontario, Ontario, Canada $100B AUM 36.93% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.88T AUM 44.46% 1-Year Est. Return
SCA
STALEY CAPITAL ADVISERS Pittsburgh, Pennsylvania $2.57B AUM 26.96% 1-Year Est. Return
Vanguard Fiduciary Trust
Vanguard Fiduciary Trust Malvern, Pennsylvania $454B AUM
Acadian Asset Management
Acadian Asset Management Boston, Massachusetts $84.2B AUM 55.88% 1-Year Est. Return

EcoR1 Capital's ATRA Position: Q2 2026 in Review

EcoR1 Capital increased its Atara Biotherapeutics (ATRA) stake by 1,458% in Q2 2026, buying an estimated $11.6M and bringing the position to 1,552,000 shares worth $17.8M. The position accounts for 0.87% of the portfolio, ranked #18.

EcoR1 Capital first reported a position in ATRA in Q4 2014 and has held it in 17 quarters since. The position peaked at $56.1M in Q2 2015. 36 funds tracked by Wall St. Rank hold ATRA as of Q2 2026.

  • EcoR1 Capital held 1,552,000 shares of Atara Biotherapeutics worth $17.8M as of Q2 2026.
  • EcoR1 Capital bought 1,452,407 Atara Biotherapeutics shares in Q2 2026, an estimated $11.6M.
  • Atara Biotherapeutics made up 0.87% of EcoR1 Capital's portfolio in Q2 2026, its #18 holding.
  • EcoR1 Capital first reported a position in Atara Biotherapeutics in Q4 2014 and has held it in 17 quarters since.
  • EcoR1 Capital's Atara Biotherapeutics position peaked at $56.1M in Q2 2015.
  • 36 funds tracked by Wall St. Rank held Atara Biotherapeutics as of Q2 2026.

Based on EcoR1 Capital's 13F filing for Q2 2026, filed 14 Aug 2026.