Mersana Therapeutics, Inc.
Mersana Therapeutics, Inc. (MRSN) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · MRSN · as of Sep 30, 2025
Ownership Breakdown
49
Institutional Holders
▼ 36 vs Q2
$24.66M
Total Inst. Value
▲ $1.74M vs Q2
5.00M
Shares Outstanding
freeFloat 70.63%
3.18M
13F Shares Held
▼ 74.26M vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
MRSN largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
BARCLAYS PLC pharmaceutical preparations | 494.5K | 9.92% | 9.92% | $934.63M | Mar 19, 2026 | ▲ 484.7K |
NEXTECH INVEST, LTD. pharmaceutical preparations | 482.7K | 9.68% | 9.68% | $3.75B | Nov 14, 2025 | NEW |
ALAMEA VERWALTUNGS GMBH pharmaceutical preparations | 430.0K | 8.62% | 8.62% | $3.34B | Nov 13, 2025 | NEW |
BAIN CAPITAL LIFE SCIENCES INVESTORS, LLC pharmaceutical preparations | 346.5K | 6.95% | 6.95% | $2.69B | Nov 14, 2025 | NEW |
VANGUARD GROUP INC pharmaceutical preparations | 302.6K | 6.07% | 6.07% | $2.35B | Nov 7, 2025 | NEW |
SCHONFELD STRATEGIC ADVISORS LLC pharmaceutical preparations | 273.6K | 5.49% | 5.49% | $2.12B | Nov 14, 2025 | NEW |
ROCK SPRINGS CAPITAL MANAGEMENT LP pharmaceutical preparations | 152.6K | 3.06% | 3.06% | $1.18B | Nov 14, 2025 | NEW |
ACADIAN ASSET MANAGEMENT LLC pharmaceutical preparations | 142.4K | 2.85% | 2.85% | $1.10B | Nov 13, 2025 | NEW |
SILVERARC CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 133.6K | 2.68% | 2.68% | $1.04B | Nov 12, 2025 | NEW |
683 CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 100.0K | 2.01% | 2.01% | $776.00M | Nov 14, 2025 | NEW |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
1
Increased
+484.7K shares42
New Positions
first time holders7
Decreased
−1.00M shares0
Sold Out
fully exitedNet shares change (top 50)
517.0K
+484.7K / −1.00M
Net new holders
+36
42 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
MRSN insider trading · insider activity
Source: SEC Form 4
0
Buy transactions
151
Sell transactions
0.00
Buy/Sell ratio
$1M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 2,460 | $9.08 | $22.3K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 1,000 | $107.75 | $107.8K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 368 | $572.50 | $210.7K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 1,800 | $90.50 | $162.9K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 2,088 | $125.00 | $261.0K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 734 | $216.00 | $158.5K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 2,200 | $56.50 | $124.3K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 1,002 | $372.50 | $373.2K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 400 | $306.75 | $122.7K | 0 | Form 4 ↗ |
Hack Andrew A. F. director | Jan 6, 2026 | D-Return | 118 | $527.25 | $62.2K | 0 | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Mersana Therapeutics, Inc. (MRSN) is primarily owned by institutional investors, who hold approximately 63.6% of total shares outstanding. Company insiders own approximately 29.37%, while retail and public investors account for the remaining 7.03%.
The largest institutional shareholder of Mersana Therapeutics, Inc. is BARCLAYS PLC, holding approximately 494,516 shares — equal to 9.92% of outstanding shares — as of September 30, 2025.
A total of 49 institutional investors currently hold MRSN stock, with a combined institutional value of approximately $24,661,797 as of the most recent 13F filing period.
Frequently asked questions
MRSN ownershipMersana Therapeutics, Inc. (MRSN) is primarily owned by institutional investors, who hold approximately 63.6% of shares. The largest shareholder is BARCLAYS PLC with a 9.92% stake. Company insiders hold 29.37%. Data sourced from SEC Form 13F as of September 30, 2025.