Security key
84833T103
Spero Therapeutics, Inc. - Common Stock, par value $0.001 per share (SPRO)
CUSIP: 84833T103
Q1 2021 13F Holders as of 31 Mar 2021
- Security type / class
- Equity / Common Stock, par value $0.001 per share
- Total 13F shares
- 18,548,675
- Total 13F value
- $273,055,350
- Share change
- +824,228
- Put/Call ratio
- 201%
- SEC-reported price per share
- $14.72
- Number of holders
- 89
- Value change
- +$11,246,827
- Number of buys
- 37
- Number of sells
- 34
- Shares outstanding
- 55,705,828
Holder snapshot
7 signals
Open additional details 1 more signal available
Security identity
Names, identifiers, and filing context for this profile.
1 source field
Report period
Q1 2021
Institutions
89
Top holders
10
SPRO full security history
Ownership snapshot
Full 13F holder table
Newer quarter: Q2 2026
Spero Therapeutics, Inc. SEC filings
Spero Therapeutics, Inc. company facts
Broader feeds
Reporting periods
Holder history for CUSIP 84833T103
Recent filing periods:
Ownership snapshot
Top reported holders of SPRO - Spero Therapeutics, Inc. - Common Stock, par value $0.001 per share (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
Aquilo Capital Management...
Disclosed value leader
Aquilo Capital Management...
Comparable rows
15/15
Latest evidence
31 Dec 2020
13F
Lead comparable stake: 7.1%
Showing 1-6 of 15 holder rows.
Quick read
Aquilo Capital Management, LLC leads the comparable SEC ownership view at 7.1%.
15 of 15 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 Aquilo Capital Management, LLC's linked filing trail.
Comparable ownership
Top 5
Aquilo Capital Management, LLC
7.1%
BVF INC/IL
4%
BlackRock Finance, Inc.
3.1%
Atlas Venture Associates IX, LLC
2.5%
Rock Springs Capital Management LP
2.2%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-6 of 15 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Aquilo Capital Management, LLC |
13F
Company
|
7.1%
|
$76,246,000
3,932,209 shares
|
— | 31 Dec 2020 |
| BVF INC/IL |
13F
Company
|
4%
|
$43,497,000
2,243,278 shares
|
— | 31 Dec 2020 |
| BlackRock Finance, Inc. |
13F
Company
|
3.1%
|
$33,576,000
1,731,600 shares
|
— | 31 Dec 2020 |
| Atlas Venture Associates IX, LLC |
13F
Company
|
2.5%
|
$26,700,000
1,376,968 shares
|
— | 31 Dec 2020 |
| Rock Springs Capital Management LP |
13F
Company
|
2.2%
|
$23,947,000
1,235,000 shares
|
— | 31 Dec 2020 |
| VANGUARD GROUP INC |
13F
Company
|
2%
|
$21,925,000
1,130,730 shares
|
— | 31 Dec 2020 |
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.
13F holder rows
Institutional holders as of Q1 2021
Investor-level positions for this CUSIP, loaded as an interactive table.
Institutions
89
Shares
18,548,675
Rows available
89
| Investor | Option | Weight % | Change % | SEC-reported value | * Price | Shares | Share Change | Activity | Report Period |
|---|
* SEC-reported price is the security price as of the portfolio date and can indicate the last known price at which the security was still held. The marker flags a reported price that did not pass the local price check.
Compare Q1 2021 vs Q1 2021 Across Filers
Q1 2021 holders
89
Q1 2021 holders
89
Holder diff
0
| Investor | Q1 2021 Shares | Q1 2021 Shares | Share Diff | Share Chg % | Q1 2021 value | Q1 2021 value | Value change | Value Chg % |
|---|
Trend: ostatnie 8 kwartałów (+ wybrane okresy porównania).
Quarterly Holders Trend
Quarterly Value Trend
Quarterly Shares Trend