Seres Therapeutics MCRB Institutional Ownership

Ownership Summary

Seres Therapeutics, Inc. (NASDAQ:MCRB) has 33 institutional investors that have filed 13F reports for the period ending March 2026.

• These investors held 23064.7% of outstanding shares in March 2026, up from 27.7% in December 2025.
• They increased total shares held in Seres Therapeutics by 17.51% from last quarter, and the number of investors in MCRB decreased 49.23% annually.
• Of these 33 holders, 16 added to their stakes in Seres Therapeutics, 8 trimmed positions, and 9 made no changes.
• Altogether, these fund groups held 2.31Mn shares in MCRB by March 2026, up by 343.76K shares quarter on quarter, and down 818.54K shares year over year.
• As of March 31, 2026, the biggest holder of Seres Therapeutics is Flagship Pioneering, LLC at 1.16Mn shares, representing 11558.5% of shares outstanding.
• Top purchasers of MCRB stock for the quarter ending March 2026 included VANGUARD CAPITAL MANAGEMENT LLC (294.14K), AMERICAN CENTURY COMPANIES INC (46.04K), VANGUARD FIDUCIARY TRUST CO (39.64K), Vontobel Holding Ltd. (35.23K), MARSHALL WACE, LLP (19.36K).
• Leading sellers of Seres Therapeutics shares for the quarter ending March 2026 were SUSQUEHANNA INTERNATIONAL GROUP, LLP (74.59K), GEODE CAPITAL MANAGEMENT, LLC (11.31K), TWO SIGMA INVESTMENTS, LP (6.96K), Morgan Stanley (3.43K), BlackRock, Inc. (1.6K).
• Business Quant data shows the 10 biggest positions in Seres Therapeutics as of March 2026 are held by Flagship Pioneering, LLC (1.16Mn), VANGUARD CAPITAL MANAGEMENT LLC (294.14K), MARSHALL WACE, LLP (139.54K), Vontobel Holding Ltd. (138.47K), SUSQUEHANNA INTERNATIONAL GROUP, LLP (105.34K), BlackRock, Inc. (102.03K), GEODE CAPITAL MANAGEMENT, LLC (74.84K), AMERICAN CENTURY COMPANIES INC (62.32K), VANGUARD FIDUCIARY TRUST CO (39.64K), State Street Corp (33.9K).