Insider buying report — Thursday, September 17, 2026: 67 open-market buys worth $234.4M
On Thursday, September 17, 2026 the SEC published 67 open-market insider purchases worth $234.4M across 45 companies, against 58 insider sales of $1M or more worth $4.53B. By dollar value the selling outweighed the buying, which is the usual state of affairs — executives at large companies sell on schedule, and buy only on purpose.
The largest purchase
Kolchinsky Peter (director · 10% owner) at Tyra Biosciences, Inc. (TYRA) filed the day's largest purchase: 9,078,529 shares at $22.03, $200.0M in total, transacted on Sep 15, 2026 and filed Sep 17, 2026. What makes it notable: it is the largest purchase this insider has ever filed; the stock was at least 25% below its recent high when they bought.
Behind it: Life Insurance Co Nippon at CRBG ($7.4M), Hrt Financial Lp at USO ($6.8M), Troim Tor Olav at BORR ($4.3M).
Top ten insider buys
| Filed | Insider | Company | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| 2026-09-17 | Kolchinsky Peterdiplargest ever Director · 10% owner | TYRA Tyra Biosciences, Inc. | Bought | 9,078,529 | $22.03 | $200.0M |
| 2026-09-17 | Life Insurance Co Nippon 10% owner | CRBG Corebridge Financial, Inc. | Bought | 210,903 | $35.02 | $7.4M |
| 2026-09-17 | Hrt Financial Lp 10% owner | USO United States Oil Fund, LP | Bought | 43,638 | $155.30 | $6.8M |
| 2026-09-17 | Troim Tor Olavdip Director | BORR Borr Drilling Ltd | Bought | 1,000,000 | $4.30 | $4.3M |
| 2026-09-17 | Pappa Milena Mariaclusterfirst buy Director | SBLK Star Bulk Carriers Corp. | Bought | 74,400 | $28.27 | $2.1M |
| 2026-09-17 | Pappas Alexandrosclusterfirst buy Insider | SBLK Star Bulk Carriers Corp. | Bought | 74,400 | $28.27 | $2.1M |
| 2026-09-17 | Zagari Raffaeleclusterfirst buy Director | SBLK Star Bulk Carriers Corp. | Bought | 60,000 | $28.27 | $1.7M |
| 2026-09-17 | Avenue Capital Management II, L.P.clusterfirst buydip 10% owner | XBP XBP Global Holdings, Inc. | Bought | 527,606 | $2.83 | $1.5M |
| 2026-09-17 | John Jr Rakolta Director | ADC AGREE REALTY CORP | Bought | 20,000 | $68.78 | $1.4M |
| 2026-09-17 | Campos Luisclusterlargest ever Director · 10% owner | BWMX BETTERWARE DE MEXICO, S.A.P.I. DE C.V | Bought | 80,000 | $16.34 | $1.3M |
Showing 10 of 67 open-market purchases filed on 2026-09-17. The full list, sortable and filterable by role and size, is in the members Filings Browser; the same rows are available as JSON through the API.
Signals in the day's buying
Of the purchases filed: 12 purchases by a chief executive (ADAG, ADC, AIM, BENF, BWMX, DLPN); 1 by a CFO (XBP); 31 that belong to an active cluster (AFCG, ALP, BENF, BUKS, BWMX, COO); 35 first-ever purchases by the insider; 34 bought at least 25% below the recent high. These are the flags the members area scores on — a CFO buying with their own money has historically been the strongest single-insider signal, and a cluster of three or more buyers the strongest of all. The cluster guide explains the scoring.
TYRA — two years of insider activity on the price
CRBG — two years of insider activity on the price
USO — two years of insider activity on the price
Largest insider sales ($1M and up)
| Filed | Insider | Company | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| 2026-09-17 | Greth Lyndal 10% owner | FANG Diamondback Energy, Inc. | Sold | 9,079,675 | $205.26 | $1.86B |
| 2026-09-17 | Greth Lyndal 10% owner | FANG Diamondback Energy, Inc. | Sold | 9,079,675 | $205.26 | $1.86B |
| 2026-09-17 | Liu Chitung CFO & SVP | UMC UNITED MICROELECTRONICS CORP | Sold | 1,600,000 | $143.00 | $228.8M |
| 2026-09-17 | Uber Technologies, Inc 10% owner | AUR Aurora Innovation, Inc. | Sold | 29,369,611 | $6.21 | $182.2M |
| 2026-09-17 | Gores Tom 10% owner | INGM Ingram Micro Holding Corp | Sold | 1,968,750 | $27.19 | $53.5M |
The largest sale was Greth Lyndal at Diamondback Energy, Inc. (FANG), $1.86B. Sales are shown from $1M upward only; below that they are overwhelmingly scheduled 10b5-1 plans and tax-driven, and listing them would bury the signal.
Context: the market-wide picture
For the week starting Sep 7, 2026, 26% of open-market insider filings across the whole market were buys (236 buys against 673 sales). The long-run average sits near a third, because insiders buy for one reason and sell for many. The full weekly series since 2019 is on the insider sentiment index.
Questions this post answers
Which insiders bought stock on Sep 17, 2026?
67 open-market purchases were filed with the SEC on Sep 17, 2026, worth $234.4M across 45 companies. The largest was Kolchinsky Peter at Tyra Biosciences, Inc. (TYRA), $200.0M. The ten largest are listed above.
Were insiders net buyers or net sellers on Sep 17, 2026?
By dollar value, sellers: $234.4M bought against $4.53B in sales of $1M or more. Selling normally dominates because executives sell on pre-set schedules; what matters is the buying, which is voluntary.
What counts as an insider buy here?
Only Form 4 transactions with code P — an open-market purchase paid for with the insider's own money. Grants (A), option exercises (M) and shares withheld for tax (F) are excluded, because they follow vesting schedules set years earlier and say nothing about what the insider thinks of the price.
How current is this?
The SEC publishes Form 4 filings through about 10 pm Eastern each business day. This report covers everything published on Sep 17, 2026 and was generated early the next morning from the same data the members area uses.