Latest Period
Q4 2025
Security Snapshot
Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN) Institutional Ownership
CUSIP: 59045L205
13F Institutional Holders and Ownership History from Q2 2025 to Q1 2026
Institutions Reporting
47
Shares (Excl. Options)
2,118,900
Price
$28.93
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- Type / Class
- Equity / Common Stock, par value $0.0001 per share
- Symbol
- MRSN
- Shares outstanding
- 4,996,999
- Price per share
- $29.00
- All holders as of 31 Dec 2025
- Q4 2025
- Total 13F shares
- 2,118,900
- Total reported value
- $61,288,183
- % of total 13F portfolios
- 0%
- Share change
- -579,869
- Value change
- -$938,648
- Number of holders
- 47
Reported Shares, Excluding Options vs Price
Reported Value, Excluding Options
Total Investors
Quick Takeaways
- MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share is tracked under CUSIP 59045L205.
- 47 institutions reported positions in Q4 2025.
- 2 significant owners is listed from Schedule 13D/13G reporting.
What Changed
- Holder count moved from 47 to 1 between Q4 2025 and Q1 2026.
- Reported value moved from $61,288,183 to $87.
Why This Matters
- You can quickly see who holds this security, then open quarter and manager detail pages for full evidence.
- 13F and Schedule 13D/13G sections are kept together so you can cross-check institutional and beneficial ownership context.
Source Evidence
Source: SEC Form 13F
Open SEC Evidence
Latest holder context comes from 47 institutions filings for Q4 2025.
Investment Quick Answers
What is CUSIP 59045L205?
CUSIP 59045L205 identifies MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share in SEC 13F datasets.
Where can I see the latest institutional holders?
Review the Q4 2025 holders report and the ownership history table below.
Next ownership checks
Use the next link that matches the question you still need to answer about this security.
- Latest 13F filings when you want to inspect fresh institutional portfolio moves.
- Latest Schedule 13D/13G reports when you need large-owner changes outside the 13F cycle.
- All institutional ownership pages to compare this security with other holder-history pages.
Recent Quarterly Holder Reports
Open recent reporting periods for CUSIP 59045L205:
Significant Owners of Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN) based on Schedule 13D/G filings
| Filer | Ownership | Change % | Holdings Value | Net Change | Nb Shares | Change % | Reporting Name | Report Period |
|---|---|---|---|---|---|---|---|---|
| 683 Capital Management, LLC | 7% | +31% | $10,215,484 | +$2,264,431 | 351,289 | +28% | 683 Capital Management, LLC | 31 Dec 2025 |
| VANGUARD GROUP INC | 4.2% | $6,082,136 | 210,301 | The Vanguard Group | 31 Dec 2025 |
As of 31 Dec 2025, 47 institutional investors reported holding 2,118,900 shares of Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN). This represents 42% of the company’s total 4,996,999 outstanding shares.
Top 25 Institutional Shareholders
The largest institutional shareholders of Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN) together control 42% of the company’s outstanding shares — a level of ownership often associated with strong institutional conviction and long‑term capital commitment.
| Institution | Ownership % | Shares Held | Share Change % | Portfolio % | Holdings Value |
|---|---|---|---|---|---|
| Nextech Invest, Ltd. | 9.7% | 482,689 | 0% | 1.3% | $13,964,193 |
| Bain Capital Life Sciences Investors, LLC | 6.9% | 346,545 | 0% | 0.77% | $10,025,547 |
| VANGUARD GROUP INC | 4.2% | 210,301 | -30% | 0% | $6,084,008 |
| Rock Springs Capital Management LP | 3.1% | 152,586 | 0% | 0.23% | $4,414,313 |
| ACADIAN ASSET MANAGEMENT LLC | 2.2% | 110,882 | -22% | 0.01% | $3,207,000 |
| Affinity Asset Advisors, LLC | 2% | 100,000 | 0.21% | $2,893,000 | |
| BlackRock, Inc. | 1.4% | 69,210 | -28% | 0% | $2,002,245 |
| BANK OF AMERICA CORP /DE/ | 1.3% | 65,749 | -0.98% | 0% | $1,902,119 |
| MILLENNIUM MANAGEMENT LLC | 1.3% | 63,305 | -19% | 0% | $1,831,414 |
| Groupe la Francaise | 1.2% | 61,488 | 0.03% | $1,778,848 | |
| Rangeley Capital, LLC | 1.1% | 57,098 | 1.4% | $1,651,845 | |
| GABELLI FUNDS LLC | 0.95% | 47,300 | 0.01% | $1,368,389 | |
| GEODE CAPITAL MANAGEMENT, LLC | 0.88% | 43,920 | +5.5% | 0% | $1,270,972 |
| CREDIT INDUSTRIEL ET COMMERCIAL | 0.83% | 41,392 | 0.17% | $1,197,471 | |
| AQR CAPITAL MANAGEMENT LLC | 0.75% | 37,264 | -20% | 0% | $1,078,047 |
| MACKENZIE FINANCIAL CORP | 0.68% | 33,834 | -29% | 0% | $967,437 |
| Yakira Capital Management, Inc. | 0.65% | 32,663 | 0.32% | $944,940 | |
| CITADEL ADVISORS LLC | 0.45% | 22,493 | 0% | $650,722 | |
| STATE STREET CORP | 0.39% | 19,543 | -35% | 0% | $565,379 |
| MORGAN STANLEY | 0.37% | 18,496 | -62% | 0% | $535,089 |
| DELTEC ASSET MANAGEMENT LLC | 0.36% | 18,000 | 0.09% | $520,740 | |
| IEQ CAPITAL, LLC | 0.26% | 12,955 | -15% | 0% | $374,788 |
| XTX Topco Ltd | 0.24% | 11,948 | 0.01% | $345,656 | |
| Point72 Asset Management, L.P. | 0.21% | 10,364 | 0% | $299,831 | |
| GAMCO INVESTORS, INC. ET AL | 0.2% | 10,000 | 0% | $289,300 |