Spero Therapeutics, Inc. (SPRO) Institutional Ownership

Ownership Summary

Recent 13F filings as of December 2025 show that 55 institutional investors hold a position in Spero Therapeutics, Inc. (NASDAQ:SPRO).

• These investors collectively held 38.1% of the company's total shares outstanding in December 2025, up from 20.3% in September 2025.
• Institutional share ownership changed by 92.53% QoQ, while the number of institutional owners saw an increase of 10.00% YoY.
• During the quarter, 30 institutions bought more Spero Therapeutics shares, 11 sold shares, and 14 of the 55 total investors held their position steady.
• The total number of shares held by institutions in Spero Therapeutics increased to 21.13Mn as of December 2025, a net change of up by 10.16Mn shares quarter on quarter, and up 5.45Mn shares year over year.
• GSK plc continues to be the largest institutional holder of Spero Therapeutics as of December 31, 2025, with a position of 9.19Mn shares, representing 16.56% of the company's outstanding stock.
• Among the most significant buyers of Spero Therapeutics during December 2025 were GSK plc (9.19Mn), CITADEL ADVISORS LLC (397.86K), TWO SIGMA INVESTMENTS, LP (323.17K), SUSQUEHANNA INTERNATIONAL GROUP, LLP (293.70K), TWO SIGMA ADVISERS, LP (216.60K).
• Leading sellers of Spero Therapeutics stock in December 2025 included Anson Funds Management LP (978.51K), RENAISSANCE TECHNOLOGIES LLC (173.24K), Informed Momentum Co LLC (64.36K), MORGAN STANLEY (43.06K), Assenagon Asset Management S.A. (18.36K).
• The top 10 institutional holders of Spero Therapeutics for the quarter ending December 2025 included GSK plc (9.19Mn), PFIZER INC (2.36Mn), VANGUARD GROUP INC (2.08Mn), RENAISSANCE TECHNOLOGIES LLC (1.28Mn), Alphabet Inc. (889.98K), Anson Funds Management LP (625.06K), GEODE CAPITAL MANAGEMENT, LLC (529.20K), BlackRock, Inc. (433.62K), CITADEL ADVISORS LLC (397.86K), TWO SIGMA INVESTMENTS, LP (372.57K).