Security key
59045L106
Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN)
CUSIP: 59045L106
Q4 2023 13F Holders as of 31 Dec 2023
- Security type / class
- Equity / Common Stock, par value $0.0001 per share
- Total 13F shares
- 113,095,763
- Total 13F value
- $262,379,163
- Share change
- +248,919
- Put/Call ratio
- 3.1%
- SEC-reported price per share
- $2.32
- Number of holders
- 104
- Value change
- +$21,039,242
- Number of buys
- 49
- Number of sells
- 73
- Shares outstanding
- 4,992,318
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
Q4 2023
Institutions
104
Top holders
10
MRSN full security history
Ownership snapshot
Full 13F holder table
Newer quarter: Q4 2025
Mersana Therapeutics, Inc. SEC filings
Mersana Therapeutics, Inc. company facts
Broader feeds
Reporting periods
Holder history for CUSIP 59045L106
Recent filing periods:
Ownership snapshot
Top reported holders of MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 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
EcoR1 Capital, LLC
Disclosed value leader
EcoR1 Capital, LLC
Comparable rows
15/15
Latest evidence
30 Sep 2023
13F
Lead comparable stake: 388%
Showing 1-6 of 15 holder rows.
Quick read
EcoR1 Capital, LLC leads the comparable SEC ownership view at 388%.
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 EcoR1 Capital, LLC's linked filing trail.
Comparable ownership
Top 5
EcoR1 Capital, LLC
388%
Venrock Adviser, LLC
227%
Bain Capital Life Sciences Invest...
174%
BlackRock Finance, Inc.
160%
VANGUARD GROUP INC
124%
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 |
|---|---|---|---|---|---|
| EcoR1 Capital, LLC |
13F
Company
|
388%
|
$24,593,154
19,364,688 shares
|
— | 30 Sep 2023 |
| Venrock Adviser, LLC |
13F
Company
|
227%
|
$14,386,560
11,328,000 shares
|
— | 30 Sep 2023 |
| Bain Capital Life Sciences Investors, LLC |
13F
Company
|
174%
|
$11,002,865
8,663,673 shares
|
— | 30 Sep 2023 |
| BlackRock Finance, Inc. |
13F
Company
|
160%
|
$10,125,278
7,972,660 shares
|
— | 30 Sep 2023 |
| VANGUARD GROUP INC |
13F
Company
|
124%
|
$7,856,376
6,186,123 shares
|
— | 30 Sep 2023 |
| Bellevue Group AG |
13F
Company
|
105%
|
$6,627,654
5,218,625 shares
|
— | 30 Sep 2023 |
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 Q4 2023
Investor-level positions for this CUSIP, loaded as an interactive table.
Institutions
104
Shares
113,095,763
Rows available
104
| 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 Q4 2023 vs Q4 2025 Across Filers
Q4 2025 holders
3
Q4 2023 holders
104
Holder diff
101
| Investor | Q4 2025 Shares | Q4 2023 Shares | Share Diff | Share Chg % | Q4 2025 value | Q4 2023 value | Value change | Value Chg % |
|---|
Trend: ostatnie 8 kwartałów (+ wybrane okresy porównania).
Quarterly Holders Trend
Quarterly Value Trend
Quarterly Shares Trend