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Pfizer’s Spero Therapeutics SPRO Stock Holding History

Pfizer’s Portfolio SPRO Stock Details SPRO Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$5.5M Hold
2,362,348
– – 2.31% 9
2025
Q4 		$5.5M Hold
2,362,348
– – 2.33% 11
2025
Q3 		$4.44M Hold
2,362,348
– – 1.02% 13
2025
Q2 		$6.85M Hold
2,362,348
– – 1.19% 10
2025
Q1 		$1.7M Hold
2,362,348
– – 0.34% 14
2024
Q4 		$2.43M Buy
+2,362,348
New +$2.81M 0.09% 17

Other funds holding SPRO

GP
GSK plc London $599M AUM
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
Renaissance Technologies
Renaissance Technologies New York $63.9B AUM 45.56% 1-Year Est. Return
AI
Alphabet Inc Mountain View, California $4.02B AUM 215.74% 1-Year Est. Return
Two Sigma Investments
Two Sigma Investments New York $124B AUM 33.93% 1-Year Est. Return
AFM
Anson Funds Management Dallas, Texas $2.29B AUM 370.24% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return
BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
Citadel Advisors
Citadel Advisors Miami, Florida $618B AUM 30.34% 1-Year Est. Return
Susquehanna International Group
Susquehanna International Group Bala Cynwyd, Pennsylvania $893B AUM 36.07% 1-Year Est. Return

Pfizer's SPRO Position: Q1 2026 in Review

Pfizer held its Spero Therapeutics (SPRO) position steady in Q1 2026 at 2,362,348 shares worth $5.5M. The position accounts for 2.31% of the portfolio, ranked #9.

Pfizer first reported a position in SPRO in Q4 2024 and has held it in 6 quarters since. The position peaked at $6.85M in Q2 2025. 50 funds tracked by Wall St. Rank hold SPRO as of Q1 2026.

  • Pfizer held 2,362,348 shares of Spero Therapeutics worth $5.5M as of Q1 2026.
  • Pfizer left its Spero Therapeutics share count unchanged in Q1 2026.
  • Spero Therapeutics made up 2.31% of Pfizer's portfolio in Q1 2026, its #9 holding.
  • Pfizer first reported a position in Spero Therapeutics in Q4 2024 and has held it in 6 quarters since.
  • Pfizer's Spero Therapeutics position peaked at $6.85M in Q2 2025.
  • 50 funds tracked by Wall St. Rank held Spero Therapeutics as of Q1 2026.

Based on Pfizer's 13F filing for Q1 2026, filed 12 May 2026.