Seaport Therapeutics SPTX Insider Ownership

Updated Oct 10, 2026

Across the past 12 months, open-market trades by Seaport Therapeutics insiders were all purchases, totaling $20.04 million (1.11Mn shares).

• Seaport Therapeutics' open-market purchases in the past 12 months came from 2 insiders; no insider sold.
• Among SPTX's insiders, Arch Venture Partners XII, LLC (10% owner) was the top open-market buyer in the past 12 months, with $19.8 million of stock purchased (1.1Mn shares) and the latest purchase on May 4, 2026.
• The newest open-market trade among Seaport Therapeutics insiders came on June 22, 2026, when Robert J. Hombach (Director) made a purchase of 13K shares for $235,768.
• Outside the open market, Seaport Therapeutics insiders acquired 21.77Mn shares through option exercises and conversions over the past 12 months.
• Per Business Quant data, Seaport Therapeutics insiders hold 26.66Mn shares in total based on their latest Form 4 filings, or 49.81% of the 53.53Mn shares outstanding; that total is unchanged from 26.66Mn shares at the end of Q2 2026.
• Seaport Therapeutics insiders hold 920.01K shares directly (3.45% of their total) and 25.74Mn shares (96.55%) indirectly, through entities such as trusts and partnerships.
• The insider holdings in Seaport Therapeutics belong to 10 insiders who have reported on Form 4 within the past two years.
• Seaport Therapeutics' three largest insider shareholders, based on their latest Form 4 filings, are Puretech Health PLC (10% owner, 16.69Mn shares), Arch Venture Partners XII, LLC (10% owner, 6.29Mn shares) and James Healy (Director, 2.73Mn shares).
• Puretech Health PLC holds 62.57% of the combined insider position in Seaport Therapeutics.
• In the last 12 months, 15 Form 4 filings with transactions in SPTX stock came from 14 insiders.
• These insider figures for Seaport Therapeutics are based on Form 4 filings through June 24, 2026.