Spero Therapeutics, Inc.
US ˙ NasdaqGS ˙ US84833T1034

SecuritySPRO / Spero Therapeutics, Inc.
InstitutionBlackRock, Inc.
Latest Disclosed Ownership690,753 shares
Ownership 2.10%
BlackRock, Inc. ownership in SPRO / Spero Therapeutics, Inc.

2022-07-08 - BlackRock, Inc. has filed an SC 13G form with the Securities and Exchange Commission (SEC) disclosing ownership of 690,753 shares of Spero Therapeutics, Inc. (US:SPRO). This represents 2.1 percent ownership of the company. In their previous filing dated 2022-02-03 , BlackRock, Inc. had reported owning 1,798,777 shares, indicating a decrease of -61.60 percent.

Institutional Ownership: 13D/G Filings

This table shows a history of the 13D/G filings made by the investor and/or investor group. Note that the share values in this table are not directly comparable to any numbers shown in the 13F table (if any).

File
Date		Effective
Date		Form Prev
Shares		 Latest
Shares		 ΔShares
(Percent)		 Ownership
(Percent)		 ΔOwnership
(Percent)
2022-07-08 2022-07-08 13G 1,798,777 690,753 -61.60 2.10 -62.50
2022-02-03 2022-02-03 13G/A 1,731,600 1,798,777 3.88 5.60 -12.50
2021-02-02 2021-02-02 13G 1,731,600 6.40

Important Note: One of the primary uses of the 13D/G filings is to evaluate the ability of a firm to control a company (ie, the "beneficial ownership"). To that end, firms are required to report not just direct holdings in companies, but indirect holdings that they control. For investment firms, these indirect holdings can include shares in funds they manage, advisory accounts, and in the case of activist campaigns, pledged votes. Therefore, share counts listed in 13D/G filings can differ significantly than share counts listed in 13F filings.

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)
2026-05-13 2026-03-31 13F SPERO THERAPEUTICS COM 84833T103 433,202 -414 -0.10 1,014 0.30 0.0000
2026-02-12 2025-12-31 13F SPERO THERAPEUTICS COM 84833T103 433,616 -1,152 -0.26 1,010 23.62 0.0000
2025-11-12 2025-09-30 13F SPERO THERAPEUTICS COM 84833T103 434,768 0 0.00 817 -35.16 0.0000
2025-08-12 2025-06-30 13F SPERO THERAPEUTICS COM 84833T103 434,768 -47,314 -9.81 1,261 263.11 0.0000
2025-05-02 2025-03-31 13F SPERO THERAPEUTICS COM 84833T103 482,082 -3,270 -0.67 347 -30.46 0.0000
2025-02-07 2024-12-31 13F SPERO THERAPEUTICS COM 84833T103 485,352 532 0.11 500 -23.11 0.0000
2024-11-13 2024-09-30 13F SPERO THERAPEUTICS COM 84833T103 484,820 1,418 0.29 650 3.34 0.0000
2024-08-13 2024-06-30 13F SPERO THERAPEUTICS COM 84833T103 483,402 6,506 1.36 628 -23.41 0.0000
2024-05-10 2024-03-31 13F SPERO THERAPEUTICS COM 84833T103 476,896 -3,703 -0.77 820 16.15 0.0000
2024-02-13 2023-12-31 13F SPERO THERAPEUTICS COM 84833T103 480,599 -1,210 -0.25 706 21.31 0.0000
2023-11-13 2023-09-30 13F SPERO THERAPEUTICS COM 84833T103 481,809 -41,995 -8.02 583 -23.32 0.0000
2023-08-11 2023-06-30 13F SPERO THERAPEUTICS COM 84833T103 523,804 33,991 6.94 760 6.90 0.0000
2023-05-12 2023-03-31 13F SPERO THERAPEUTICS COM 84833T103 489,813 1,730 0.35 710 -15.88 0.0000
2023-02-13 2022-12-31 13F SPERO THERAPEUTICS COM 84833T103 488,083 -204,055 -29.48 844 -39.06 0.0000
2022-11-14 2022-09-30 13F SPERO THERAPEUTICS COM 84833T103 692,138 1,385 0.20 1,385 169.98 0.0000
2022-08-12 2022-06-30 13F SPERO THERAPEUTICS COM 84833T103 690,753 -1,103,328 -61.50 513 -96.71 0.0000
2022-05-12 2022-03-31 13F SPERO THERAPEUTICS COM 84833T103 1,794,081 -4,696 -0.26 15,609 -45.80 0.0004
2022-02-10 2021-12-31 13F SPERO THERAPEUTICS COM 84833T103 1,798,777 -3,751 -0.21 28,799 -13.22 0.0007
2021-11-09 2021-09-30 13F SPERO THERAPEUTICS COM 84833T103 1,802,528 23,706 1.33 33,185 33.63 0.0009
2021-08-11 2021-06-30 13F SPERO THERAPEUTICS COM 84833T103 1,778,822 2,226 0.13 24,833 -5.04 0.0007
2021-05-07 2021-03-31 13F SPERO THERAPEUTICS COM 84833T103 1,776,596 44,996 2.60 26,152 -22.11 0.0008
2021-02-05 2020-12-31 13F SPERO THERAPEUTICS COM 84833T103 1,731,600 654,438 60.76 33,576 179.33 0.0011
2020-11-06 2020-09-30 13F SPERO THERAPEUTICS COM 84833T103 1,077,162 126,906 13.35 12,020 -6.51 0.0004
2020-08-14 2020-06-30 13F SPERO THERAPEUTICS COM 84833T103 950,256 69,025 7.83 12,857 80.58 0.0005
2020-05-01 2020-03-31 13F SPERO THERAPEUTICS COM 84833T103 881,231 125,966 16.68 7,120 -1.94 0.0003
2020-02-13 2019-12-31 13F SPERO THERAPEUTICS COM 84833T103 755,265 76,316 11.24 7,261 0.88 0.0003
2019-11-08 2019-09-30 13F SPERO THERAPEUTICS COM 84833T103 678,949 22,171 3.38 7,198 -4.78 0.0003
2019-08-22 2019-06-30 13F/A-1 SPERO THERAPEUTICS COM 84833T103 656,778 235,691 55.97 7,559 40.11 0.0003
2019-08-13 2019-06-30 13F SPERO THERAPEUTICS COM 84833T103 656,778 7,559
2019-05-09 2019-03-31 13F SPERO THERAPEUTICS COM 84833T103 421,087 27,457 6.98 5,395 122.84 0.0002
2019-02-08 2018-12-31 13F SPERO THERAPEUTICS COM 84833T103 393,630 21,161 5.68 2,421 -38.16 0.0001
2018-11-09 2018-09-30 13F SPERO THERAPEUTICS COM 84833T103 372,469 30,470 8.91 3,915 -21.97 0.0002
2018-08-09 2018-06-30 13F SPERO THERAPEUTICS COM 84833T103 341,999 89,698 35.55 5,017 39.52 0.0002
2018-05-09 2018-03-31 13F SPERO THERAPEUTICS COM 84833T103 252,301 11,427 4.74 3,596 27.07 0.0002
2018-02-09 2017-12-31 13F SPERO THERAPEUTICS COM 84833T103 240,874 240,874 2,830 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.