Comparable stake leader
GSK plc
SEC ownership of Spero Therapeutics, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001701108.
Disclosed value leader
GSK plc
Comparable rows
50/50
Latest evidence
30 Jun 2026
- Public ticker
- SPRO on Nasdaq
- Parsed ownership sources
-
13F, 13D/G, and 3/4/5
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
GSK plc
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
50 of 50
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
GSK plc
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
30 Jun 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001701108
- Issuer location
- Cambridge, MA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of Spero Therapeutics, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
GSK plc
Disclosed value leader
GSK plc
Comparable rows
50/50
Latest evidence
30 Jun 2026
13F
13D/G
3/4/5
Lead comparable stake: 16%
13D/G row: GSK plc
Showing 1-8 of 50 holder rows.
Quick read
GSK plc leads the comparable SEC ownership view at 16%.
50 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens GSK plc's linked filing trail.
Comparable ownership
Top 5
GSK plc
16%
Anson Funds Management LP
2.9%
Ankit Mahadevia
1.3%
PFIZER INC
4.2%
VANGUARD CAPITAL MANAGEMENT LLC
3.7%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| GSK plc |
13F
13D/G
3/4/5
Company · 10%+ Owner
|
16%
from 13D/G
|
$20,311,239
9,190,606 shares
|
— | 30 Jun 2026 |
| Anson Funds Management LP |
13D/G
|
2.9%
|
$4,587,932
1,615,469 shares
|
$0 | 30 Jun 2025 |
| Ankit Mahadevia |
3/4/5
Director
|
1.3%
|
$1,385,489
703,294 shares
|
— | 28 Aug 2025 |
| PFIZER INC |
13F
Company
|
4.2%
|
$5,338,906
2,362,348 shares
|
— | 30 Jun 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC |
13F
Company
|
3.7%
|
$4,500,059
2,036,226 shares
|
— | 30 Jun 2026 |
| RENAISSANCE TECHNOLOGIES LLC |
13F
Company
|
1.7%
|
$2,094,868
947,904 shares
|
— | 30 Jun 2026 |
| Alphabet Inc. |
13F
Company
|
1.6%
|
$1,966,854
889,979 shares
|
— | 30 Jun 2026 |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP |
13F
Company
|
1.4%
|
$1,678,031
759,290 shares
|
— | 30 Jun 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Net insider flow leans to selling over the last 12 months. Net value: -$552,042.
Buys
$0
Insiders: 0
Sells
$552,042
Insiders: 2
Net
-$552,042
Shares: -237,107
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 237,107
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 25,240 | $0 | $63,352 | -$63,352 |
| 6-9 | 0 | 171,597 | $0 | $393,250 | -$393,250 |
| 9-12 | 0 | 40,270 | $0 | $95,440 | -$95,440 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-20 of 20 reporting-owner rows connected to Spero Therapeutics, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
20
Largest Forms 3/4/5 holder
GSK plc
Net 12M change
-$552,042
Latest report
03 Aug 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| GSK plc | 10%+ Owner | $11,672,070 | Mixed | 07 Nov 2022 | ||
| Aquilo Capital Management, LLC | 10%+ Owner | $4,342,682 | Mixed | 22 Sep 2022 | ||
| Esther Rajavelu | Chief Executive Officer, Chief Financial Officer and Chief Business Officer | $2,476,996 | -$406,849 | -14% | Filing P/S | 04 May 2026 |
| Timothy Keutzer | Chief Operating Officer | $1,752,314 | -$145,193 | -7.7% | Filing P/S | 06 Feb 2026 |
| Ankit Mahadevia | Director | $1,385,489 | Filing P/S | 28 Aug 2025 | ||
| Sath Shukla | CEO & President | $1,354,769 | Filing P/S | 03 Feb 2025 | ||
| Kamal Hamed | Chief Medical Officer | $1,079,720 | Filing P/S | 01 Feb 2024 | ||
| Tamara L. Joseph | Chief Legal Officer | $728,313 | Filing P/S | 01 Feb 2024 | ||
| Debra Jeske Zack | Chief Medical Officer | $358,707 | Median | 03 Aug 2026 | ||
| Milind Deshpande | Director | $237,402 | Mixed | 23 Jun 2026 | ||
| John C. Pottage Jr. | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Frank E. Thomas | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Kathleen Tregoning | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Cynthia Smith | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Patrick V.j.j. Vink | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Scott Thomas Jackson | Director | $198,900 | Mixed | 23 Jun 2026 | ||
| Cristina Larkin | Chief Operating Officer | $140,321 | Mixed | 01 Feb 2022 | ||
| David A. Melnick | Chief Medical Officer | $138,416 | Mixed | 01 Feb 2022 | ||
| Jean Francois Formela | Director | $8,400 | Mixed | 17 Aug 2021 | ||
| Stephen J. DiPalma | Interim Chief Financial Officer Exhibit 24.1 - Power of Attorney | Mixed | 15 Jul 2023 |
Recent insider transactions for Spero Therapeutics, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Debra Jeske Zack | SPRO | Common Stock | Award | 162,311 | 162,311 | 03 Aug 2026 | Direct | |||
| Debra Jeske Zack | SPRO | Stock option (right to buy) | Award | 324,675 | 324,675 | 03 Aug 2026 | Direct | |||
| Milind Deshpande | SPRO | Common Stock | Award | 10.9% | 10,000 | 101,454 | 23 Jun 2026 | Direct | ||
| Milind Deshpande | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Kathleen Tregoning | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| Kathleen Tregoning | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Cynthia Smith | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| Cynthia Smith | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Patrick V.j.j. Vink | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| Patrick V.j.j. Vink | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Frank E. Thomas | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| Frank E. Thomas | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Scott Thomas Jackson | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| Scott Thomas Jackson | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| John C. Pottage Jr. | SPRO | Common Stock | Award | 13.3% | 10,000 | 85,000 | 23 Jun 2026 | Direct | ||
| John C. Pottage Jr. | SPRO | Stock Option (right to buy) | Award | 20,000 | 20,000 | 23 Jun 2026 | Direct | |||
| Esther Rajavelu | SPRO | Common Stock | Sale | -2.49% | $63,352 | $2.51 | -25,240 | 986,851 | 04 May 2026 | Direct |
| Esther Rajavelu | SPRO | Common Stock | Sale | -7.99% | $207,484 | $2.36 | -87,917 | 1,012,091 | 06 Feb 2026 | Direct |
| Timothy Keutzer | SPRO | Common Stock | Sale | -2.45% | $44,019 | $2.36 | -18,652 | 742,506 | 06 Feb 2026 | Direct |
| Timothy Keutzer | SPRO | Common Stock | Sale | -0.45% | $7,775 | $2.24 | -3,471 | 761,158 | 04 Feb 2026 | Direct |
| Timothy Keutzer | SPRO | Common Stock | Sale | -3.07% | $51,839 | $2.14 | -24,224 | 764,629 | 03 Feb 2026 | Direct |
| Esther Rajavelu | SPRO | Common Stock | Sale | -1.65% | $40,572 | $2.20 | -18,442 | 1,100,008 | 02 Feb 2026 | Direct |
| Esther Rajavelu | SPRO | Common Stock | Award | 28.6% | 249,000 | 1,118,450 | 02 Feb 2026 | Direct | ||
| Esther Rajavelu | SPRO | Stock Option (Right to Buy) | Award | 498,000 | 498,000 | 02 Feb 2026 | Direct | |||
| Timothy Keutzer | SPRO | Common Stock | Sale | -2.34% | $41,560 | $2.20 | -18,891 | 788,853 | 02 Feb 2026 | Direct |
| Timothy Keutzer | SPRO | Common Stock | Award | 9.19% | 68,000 | 807,744 | 02 Feb 2026 | Direct | ||
| Timothy Keutzer | SPRO | Stock Option (Right to Buy) | Award | 137,000 | 137,000 | 02 Feb 2026 | Direct | |||
| Esther Rajavelu | SPRO | Common Stock | Sale | -4.43% | $95,440 | $2.37 | -40,270 | 869,450 | 07 Nov 2025 | Direct |
* marks a reported price that did not pass the local price check.