Spero Therapeutics, Inc.
US ˙ NasdaqGS ˙ US84833T1034

SecuritySPRO / Spero Therapeutics, Inc.
InstitutionDimensional Fund Advisors Lp
Latest Disclosed Ownership29,768 shares
Latest Disclosed Value $ 69,207
Dimensional Fund Advisors Lp ownership in SPRO / Spero Therapeutics, Inc.

On May 7, 2026 - Dimensional Fund Advisors Lp filed a 13F-HR form disclosing ownership of 29,768 shares of Spero Therapeutics, Inc. (US:SPRO) valued at $69,657 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 29,768 shares of Spero Therapeutics, Inc.. This represents a change in shares of 0.00% during the quarter. The current value of the position is $83,946 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-07 2026-03-31 13F SPERO THERAPEUTICS COM 84833T103 29,768 0 0.00 69 0.00 0.0000
2026-02-12 2025-12-31 13F SPERO THERAPEUTICS COM 84833T103 29,768 774 2.67 69 27.78 0.0000
2025-11-12 2025-09-30 13F SPERO THERAPEUTICS COM 84833T103 28,994 28,994 55 0.0000
2025-05-13 2025-03-31 13F SPERO THERAPEUTICS COM 84833T103 0 -10,003 -100.00 0 -100.00
2025-02-13 2024-12-31 13F SPERO THERAPEUTICS COM 84833T103 10,003 0 0.00 10 -23.08 0.0000
2024-11-07 2024-09-30 13F SPERO THERAPEUTICS COM 84833T103 10,003 0 0.00 13 0.00 0.0000
2024-08-09 2024-06-30 13F SPERO THERAPEUTICS COM 84833T103 10,003 0 0.00 13 -23.53 0.0000
2024-05-10 2024-03-31 13F SPERO THERAPEUTICS COM 84833T103 10,003 0 0.00 17 21.43 0.0000
2024-02-07 2023-12-31 13F SPERO THERAPEUTICS COM 84833T103 10,003 -1,750 -14.89 15 0.00 0.0000
2023-11-09 2023-09-30 13F SPERO THERAPEUTICS COM 84833T103 11,753 0 0.00 14 -17.65 0.0000
2023-08-09 2023-06-30 13F SPERO THERAPEUTICS COM 84833T103 11,753 0 0.00 17 0.00 0.0000
2023-05-12 2023-03-31 13F SPERO THERAPEUTICS COM 84833T103 11,753 0 0.00 17 0.0000
2023-02-09 2022-12-31 13F SPERO THERAPEUTICS COM 84833T103 11,753 1,750 17.49 0 -100.00 0.0000
2022-11-10 2022-09-30 13F SPERO THERAPEUTICS COM 84833T103 10,003 -274,953 -96.49 20 -90.57 0.0000
2022-08-12 2022-06-30 13F SPERO THERAPEUTICS COM 84833T103 284,956 -121,990 -29.98 212 -94.01 0.0001
2022-05-13 2022-03-31 13F SPERO THERAPEUTICS COM 84833T103 406,946 35,724 9.62 3,540 -40.43 0.0011
2022-02-09 2021-12-31 13F SPERO THERAPEUTICS COM 84833T103 371,222 41,589 12.62 5,943 -2.06 0.0018
2021-11-12 2021-09-30 13F SPERO THERAPEUTICS COM 84833T103 329,633 -44,810 -11.97 6,068 16.09 0.0020
2021-08-12 2021-06-30 13F SPERO THERAPEUTICS COM 84833T103 374,443 31,937 9.32 5,227 3.69 0.0017
2021-05-14 2021-03-31 13F SPERO THERAPEUTICS COM 84833T103 342,506 92,309 36.89 5,041 3.90 0.0017
2021-03-08 2020-12-31 13F/A-2 SPERO THERAPEUTICS COM 84833T103 250,197 19,188 8.31 4,852 88.28 0.0018
2021-02-11 2020-12-31 13F SPERO THERAPEUTICS COM 84833T103 250,197 19,188 4,852 1,752.2845
2020-11-12 2020-09-30 13F SPERO THERAPEUTICS COM 84833T103 231,009 16,854 7.87 2,577 -11.05 0.0011
2020-08-13 2020-06-30 13F SPERO THERAPEUTICS COM 84833T103 214,155 15,294 7.69 2,897 80.27 0.0013
2020-05-14 2020-03-31 13F SPERO THERAPEUTICS COM 84833T103 198,861 43,381 27.90 1,607 7.49 0.0008
2020-02-14 2019-12-31 13F SPERO THERAPEUTICS COM 84833T103 155,480 32,475 26.40 1,495 14.65 0.0005
2019-11-12 2019-09-30 13F SPERO THERAPEUTICS COM 84833T103 123,005 16,602 15.60 1,304 6.54 0.0005
2019-08-13 2019-06-30 13F SPERO THERAPEUTICS COM 84833T103 106,403 88,534 495.46 1,224 434.50 0.0005
2019-08-12 2019-03-31 13F/A-2 SPERO THERAPEUTICS COM 84833T103 17,869 17,869 229 0.0001
2019-05-10 2019-03-31 13F SPERO THERAPEUTICS COM 84833T103 17,869 229 0.0001
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.