Simplex Trading Portfolio holdings
Simplex Trading, founded in 2004 and headquartered in Chicago, Illinois, is a technology-driven proprietary trading firm specializing in market-making and liquidity provision, primarily in U.S. equity options and futures options. Leveraging advanced proprietary software and data-driven analysis, the firm optimizes trading strategies and develops innovative solutions to capitalize on financial market opportunities, maintaining a competitive edge through automation and a collaborative team of technologists and traders. With a workforce exceeding 300 and led by CEO Erik Swanson since 2014, Simplex operates with a low-ego, high-intelligence culture, focusing on minimal bureaucracy and rapid execution, while also making strategic venture capital investments in fintech startups. Recognized as a top workplace in Chicago by Built In’s 2025 awards, Simplex continues to evolve, blending cutting-edge technology with a commitment to market efficiency and growth.
Top Buys
| Rank | Stock | Value |
|---|---|---|
| 1 |
Netflix
NFLX
|
+$73.1M |
| 2 |
Western Digital
WDC
|
+$51.8M |
| 3 |
iShares Semiconductor ETF
SOXX
|
+$46M |
| 4 |
Meta Platforms (Facebook)
META
|
+$41.8M |
| 5 |
Alibaba
BABA
|
+$37.1M |
Top Sells
| Rank | Stock | Value |
|---|---|---|
| 1 |
NVIDIA
NVDA
|
+$262M |
| 2 |
Microsoft
MSFT
|
+$194M |
| 3 |
iShares Russell 2000 ETF
IWM
|
+$149M |
| 4 |
Apple
AAPL
|
+$119M |
| 5 |
Amazon
AMZN
|
+$107M |
Sector Composition
| Rank | Sector | Weight |
|---|---|---|
| 1 | Technology | 0.59% |
| 2 | Consumer Discretionary | 0.21% |
| 3 | Healthcare | 0.2% |
| 4 | Industrials | 0.18% |
| 5 | Communication Services | 0.16% |
| Name | Market Value | Portfolio Weight | Shares or Principal |
Change in Stake | Capital Flow | |
|---|---|---|---|---|---|---|
4001
PUT
AdaptHealth
AHCO
$1.47B
| $250K | ﹤0.01% |
25,100
| – | – |
|
4002
CALL
Azenta
AZTA
$1.3B
| $249K | ﹤0.01% |
7,500
+7,300
| +3,650% | +$239K |
|
|
BDN
4003
Brandywine Realty Trust
BDN
$521M
| $249K | ﹤0.01% |
85,348
+54,356
| +175% | +$185K |
|
4004
CALL
BeyondSpring
BYSI
$48.1M
| $249K | ﹤0.01% |
152,700
-5,900
| -4% | -$11.3K |
|
|
KDK
4005
Kodiak AI
KDK
$798M
| $249K | ﹤0.01% |
+22,779
| New | +$182K |
|
4006
Marathon Digital Holdings
MARA
$4.02B
| $248K | ﹤0.01% |
+27,666
| New | +$408K |
|
4007
CALL
Keros Therapeutics
KROS
$198M
| $248K | ﹤0.01% |
12,200
-36,600
| -75% | -$642K |
|
|
NFBK
4008
PUT
DELISTED
Northfield Bancorp
NFBK
| $248K | ﹤0.01% |
21,700
| – | – |
|
4009
Deckers Outdoor
DECK
$14.1B
| $248K | ﹤0.01% |
+2,389
| New | +$224K |
|
4010
CALL
Prothena Corp
PRTA
$442M
| $247K | ﹤0.01% |
25,900
-37,600
| -59% | -$383K |
|
|
ORCX
4011
Defiance Daily Target 2X Long ORCL ETF
ORCX
$205M
| $247K | ﹤0.01% |
4,784
+4,711
| +6,453% | +$399K |
|
4012
PUT
AnaptysBio
ANAB
$1.54B
| $247K | ﹤0.01% |
5,100
-9,900
| -66% | -$386K |
|
4013
CALL
CryoPort
CYRX
$751M
| $247K | ﹤0.01% |
25,700
-42,700
| -62% | -$403K |
|
4014
Tarsus Pharmaceuticals
TARS
$2.53B
| $247K | ﹤0.01% |
3,013
+1,419
| +89% | +$106K |
|
4015
CALL
Scholar Rock
SRRK
$5.91B
| $247K | ﹤0.01% |
5,600
-91,300
| -94% | -$3.42M |
|
4016
Direxion Daily CSI 300 China A Share Bull 2X ETF
CHAU
$88.4M
| $247K | ﹤0.01% |
11,735
-80,104
| -87% | -$1.63M |
|
4017
CALL
Fulcrum Therapeutics
FULC
$246M
| $247K | ﹤0.01% |
21,800
+19,400
| +808% | +$197K |
|
4018
CALL
Quince Therapeutics
QNCX
$21.1M
| $246K | ﹤0.01% |
367
+286
| +353% | +$144K |
|
4019
CALL
Natural Gas Services Group
NGS
$458M
| $246K | ﹤0.01% |
7,300
-83,100
| -92% | -$2.48M |
|
4020
CALL
Zymeworks
ZYME
$1.62B
| $245K | ﹤0.01% |
9,300
-23,900
| -72% | -$521K |
|
|
MREO
4021
PUT
Mereo BioPharma
MREO
$50.4M
| $245K | ﹤0.01% |
586,400
+577,000
| +6,138% | +$1.1M |
|
4022
PUT
Paylocity
PCTY
$7.9B
| $244K | ﹤0.01% |
+1,600
| New | +$238K |
|
4023
Beam Therapeutics
BEAM
$2.72B
| $244K | ﹤0.01% |
8,802
-5,530
| -39% | -$141K |
|
4024
CALL
NCR Atleos
NATL
$3.51B
| $244K | ﹤0.01% |
6,400
-2,900
| -31% | -$109K |
|
4025
CALL
1-800-Flowers.com
FLWS
$257M
| $244K | ﹤0.01% |
62,000
+36,900
| +147% | +$145K |
|
Similar funds
Simplex Trading's Q4 2025 Portfolio in Review
As of Q4 2025, Simplex Trading held 10,526 positions worth $177B, down 9% from $195B the previous quarter. Its ten largest holdings account for 49% of the portfolio.
Simplex Trading withdrew a net $23.2B in Q4 2025, closing 2,184 positions and reducing 4,088 holdings. Its most notable exit was iShares Russell 2000 ETF, an estimated $149M position sold in full.
By sector, the portfolio is most concentrated in Technology at 0.59% of assets, down from 0.79% a quarter earlier, followed by Consumer Discretionary and Healthcare.
Against the trend, Simplex Trading opened a new position in Western Digital worth $58.9M.
- Simplex Trading's largest Q4 2025 buy was Western Digital: 341,762 shares worth $58.9M.
- Simplex Trading added most to Netflix in Q4 2025, an estimated $73.1M increase.
- Simplex Trading's biggest Q4 2025 reduction was NVIDIA, cutting an estimated $262M.
- Simplex Trading fully exited iShares Russell 2000 ETF in Q4 2025, selling an estimated $149M.
- Simplex Trading's ten largest holdings make up 49% of its $177B portfolio in Q4 2025.
- Simplex Trading opened 1,476 new positions and closed 2,184 in Q4 2025.
- Simplex Trading's portfolio value fell 9% quarter-over-quarter to $177B.
Based on Simplex Trading's 13F filing for Q4 2025, filed 11 Feb 2026.