ATRA Atara Biotherapeutics, Inc.

NASDAQ
$9.71

Atara Biotherapeutics, Inc. (ATRA) Insider Activity

What the officers, directors and large holders did with their own shares. Only open-market purchases and sales count toward the totals — grants, option exercises and shares withheld for tax are compensation mechanics, not decisions, and they're listed separately below.

30D 90D 6M 1Y
Insider signal Bullish Insiders bought more than they sold over this window — uncommon at any size.
Cluster activity 1 buyer in the last 30 days 1 buyer in the last 90 days 1 seller in the last 90 days
Insiders buying
2
2 transactions
Insiders selling
3
18 transactions
Purchases
$5.7M
611,573 shares
Sales
$3.9M
416,536 shares
Net activity
$1.9M
purchases less sales

How much of that selling was preplanned? 0% planned / 100% discretionary

10b5-1 plan sales $0 0 transactions · 0 shares
Discretionary sales $3.9M 18 transactions · 416,536 shares

Largest single sale: $3.2M.

Where they traded

Buy Sell Dot area is proportional to transaction value.

Last open-market purchase: September 4, 2026 , by Cherry Brian N .

Recent open-market activity

Date Insider Role Action Shares Price Value Held after
Cherry Brian N Director Buy 104,166 $9.60 $1000.0K 166,486
Nguyen AnhCo President and CEO Sell 5,062 $8.08 $40.9K 132,775 −3.7% of holding
Nguyen AnhCo President and CEO Sell 5,241 $9.13 $47.8K 137,837 −3.7% of holding
Grant-Huerta Yanina Chief Accounting Officer Sell 2,414 $9.13 $22.0K 49,636 −4.6% of holding
EcoR1 Capital, LLC 10% Owner Buy 507,407 $9.35 $4.7M 1,552,000
Sell 313,446 $10.10 $3.2M 1,011,000 −23.7% of holding
Nguyen AnhCo 4 fills President and CEO Sell 2,996 $5.09 $15.2K 64,776 −4.4% of holding
Grant-Huerta Yanina 4 fills Chief Accounting Officer Sell 2,104 $5.08 $10.7K 33,830 −5.9% of holding
Sell 80,554 $6.07 $489.0K 1,324,446 −5.7% of holding
Nguyen AnhCo 2 fills President and CEO Sell 2,915 $13.19 $38.4K 65,030 −4.3% of holding
Grant-Huerta Yanina 3 fills Chief Accounting Officer Sell 1,804 $13.19 $23.8K 33,613 −5.1% of holding

Form 4s are due within two business days of a transaction, so this is close to real time — unlike the quarterly 13F data on the Institutional tab. A single large sale often reflects a prearranged 10b5-1 plan rather than a fresh view, so read a pattern of sales rather than any one of them.