SEAPORT THERAPEUTICS INC SPTX
COMMON STOCK · Common Stock · CUSIP 81221K108
- SectorHealth care
- IndustryPharmaceutical Preparations
- HeadquartersBoston, MA
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once. Holder counts are more reliable. Shares outstanding: 53.5m as of 2026-06-05, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $21.76.
Biggest buyers
| ARCH Venture Management, LLC | New | +6.3m |
| GENERAL ATLANTIC, L.P. | New | +6.1m |
| Sofinnova Investments, Inc. | New | +3.6m |
| GOLDMAN SACHS GROUP INC | New | +2.2m |
| TRV GP VI, LLC | New | +2.1m |
| CANADA PENSION PLAN INVESTMENT BOARD | New | +2.0m |
| JPMORGAN CHASE & CO | New | +1.8m |
| Foresite Capital Management VI LLC | New | +1.8m |
| PRICE T ROWE ASSOCIATES INC /MD/ | New | +1.3m |
| FMR LLC | New | +1.2m |
Biggest sellers
| None |
Major shareholders (over 5%)
Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.
| Holder | Stake |
|---|---|
| PureTech LYT, Inc. 13G · exempt (held before listing) new · filed 2026-08-14 | 31.2% |
ARCH Venture Fund XII, L.P.
13D · may seek influence
new · filed 2026-05-06
Stated purposeAVF XII and the other Reporting Persons acquired the Common Stock for investment purposes. Depending on market conditions, the continuing evaluation of the business and prospects of the Issuer and other factors, AVF XII and other Reporting Persons may dispose of or acquire additional shares of Common Stock of the Issuer. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in the matters set forth in subparagraphs (a) - (j) of Item 4 of Schedule 13D. Full filing |
11.9% |
GENERAL ATLANTIC, L.P.
13D · may seek influence
new · filed 2026-05-11
Stated purposeThe Reporting Persons acquired the common stock reported herein for investment purposes. Consistent with such purposes, the Reporting Persons may engage in communications with, without limitation, one or more shareholders of the Company, management of the Company, one or more members of the board of directors of the Company, and may make suggestions concerning the Company's operations, prospects, business and financial strategies, strategic transactions, assets and liabilities, business and financing alternatives, the composition of the board of directors of the Company and such other matters as the Reporting Persons may deem relevant to their investment in the common stock. The Reporting Persons expect that they will, from time to time, review their investment position in the common stoc… Full filing |
11.5% |
| Zohar Daphne 13G · exempt (held before listing) new · filed 2026-08-05 | 9.1% |
| PAUL STEVEN M 13G · exempt (held before listing) new · filed 2026-08-05 | 6.3% |
| GOLDMAN SACHS GROUP INC 13G · passive investor new · filed 2026-05-11 | 5.5% |
Insider purchases and sales since 1 Apr 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q4 2024 | 0 | — | 0 | — | — |
| Q1 2025 | 0 | — | 0 | — | — |
| Q2 2025 | 0 | — | 0 | — | — |
| Q3 2025 | 0 | — | 0 | — | — |
| Q4 2025 | 0 | — | 0 | — | — |
| Q1 2026 | 0 | — | 0 | — | — |
| Q2 2026 | 1 | $235.8k | 0 | — | — |
| Q3 2026 | 0 | — | 0 | — | — |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-06-22 | HOMBACH ROBERT J. Director · By Robert Joseph Hombach Revocable Trust | Bought | $235.8k13.0k shares |
| 2026-05-04 | CRANDELL KEITH +6 10% owner · By ARCH Venture Fund XII, L.P. | Bought | $19.8m1.1m shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q2 2026
| Manager | Shares | Change |
|---|---|---|
| ARCH Venture Management, LLC 12.42% of their portfolio | 6.3m $136.6m | New |
| GENERAL ATLANTIC, L.P. 4.56% of their portfolio | 6.1m $132.5m | New |
| Sofinnova Investments, Inc. 4.14% of their portfolio | 3.6m $77.4m | New |
| GOLDMAN SACHS GROUP INC 0.00% of their portfolio | 2.2m $47.3m | New |
| TRV GP VI, LLC 19.27% of their portfolio | 2.1m $44.8m | New |
| CANADA PENSION PLAN INVESTMENT BOARD 0.02% of their portfolio | 2.0m $42.9m | New |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 1.8m $40.9m | New |
| Foresite Capital Management VI LLC 6.02% of their portfolio | 1.8m $38.7m | New |
| PRICE T ROWE ASSOCIATES INC /MD/ 0.00% of their portfolio | 1.3m $28.4m | New |
| FMR LLC 0.00% of their portfolio | 1.2m $25.7m | New |
| Bellevue Group AG 0.50% of their portfolio | 1.1m $23.9m | New |
| Siren, L.L.C. 0.48% of their portfolio | 1.1m $23.8m | New |
| JENNISON ASSOCIATES LLC 0.01% of their portfolio | 1.1m $23.5m | New |
| RA CAPITAL MANAGEMENT, L.P. 0.13% of their portfolio | 700.0k $15.2m | New |
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 599.2k $13.0m | New |
| Woodline Partners LP 0.04% of their portfolio | 586.3k $12.7m | New |
| PERCEPTIVE ADVISORS LLC 0.17% of their portfolio | 500.0k $10.9m | New |
| BRAIDWELL LP 0.40% of their portfolio | 500.0k $10.9m | New |
| PRINCIPAL FINANCIAL GROUP INC 0.00% of their portfolio | 414.7k $9.0m | New |
| Aberdeen Group plc 0.01% of their portfolio | 310.4k $6.7m | New |
| UBS Group AG 0.00% of their portfolio | 279.2k $6.1m | New |
| BlackRock, Inc. 0.00% of their portfolio | 229.9k $5.0m | New |
| SEVEN GRAND MANAGERS, LLC 0.20% of their portfolio | 225.0k $4.9m | New |
| CITADEL ADVISORS LLC 0.00% of their portfolio | 191.1k $4.2m | New |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 175.9k $3.8m | New |
| Pier Capital, LLC 0.49% of their portfolio | 170.0k $3.7m | New |
| AMERIPRISE FINANCIAL INC 0.00% of their portfolio | 131.8k $2.9m | New |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.00% of their portfolio | 97.7k $2.1m | New |
| VANGUARD FIDUCIARY TRUST CO 0.00% of their portfolio | 87.8k $1.9m | New |
| Pentwater Capital Management LP 0.01% of their portfolio | 83.0k $1.8m | New |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE 0.00% of their portfolio | 82.6k $1.8m | New |
| Alyeska Investment Group, L.P. 0.00% of their portfolio | 75.0k $1.6m | New |
| ALPS ADVISORS INC 0.01% of their portfolio | 54.3k $1.2m | New |
| TD Asset Management Inc 0.00% of their portfolio | 47.9k $1.0m | New |
| MILLENNIUM MANAGEMENT LLC 0.00% of their portfolio | 45.3k $984.7k | New |
| GSA CAPITAL PARTNERS LLP 0.05% of their portfolio | 33.2k $721.0k | New |
| DAFNA Capital Management LLC 0.13% of their portfolio | 32.4k $703.7k | New |
| NORTHERN TRUST CORP 0.00% of their portfolio | 31.8k $690.7k | New |
| ADAR1 Capital Management, LLC 0.03% of their portfolio | 26.0k $564.7k | New |
| Ghisallo Capital Management LLC 0.01% of their portfolio | 25.0k $543.0k | New |
| Burkehill Global Management, LP 0.02% of their portfolio | 25.0k $543.0k | New |
| Squarepoint Ops LLC 0.00% of their portfolio | 24.8k $537.6k | New |
| HighTower Advisors, LLC 0.00% of their portfolio | 16.7k $362.0k | New |
| MORGAN STANLEY 0.00% of their portfolio | 11.7k $254.0k | New |
| XTX Topco Ltd 0.00% of their portfolio | 11.0k $238.6k | New |
| Weiss Asset Management LP 0.00% of their portfolio | 10.0k $217.2k | Not comparable |
| Zimmer Partners, LP 0.01% of their portfolio | 10.0k $217.2k | New |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.00% of their portfolio | 9.1k $197.2k | New |
| Vanguard Global Advisers, LLC 0.00% of their portfolio | 7.2k $155.5k | New |
| CITIGROUP INC 0.00% of their portfolio | 2.5k $53.3k | New |
| JONES FINANCIAL COMPANIES LLLP 0.00% of their portfolio | 2.3k $48.3k | New |
| ASSETMARK, INC 0.00% of their portfolio | 1.4k $31.1k | New |
| BARCLAYS PLC 0.00% of their portfolio | 837 $18.2k | New |
| Integrated Wealth Concepts LLC 0.00% of their portfolio | 32 $695 | New |