Comparable stake leader
VANGUARD GROUP INC
SEC ownership of Mersana Therapeutics, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001442836.
Disclosed value leader
Crossover I. Scsp Nextech
Comparable rows
3/14
Latest evidence
06 Jan 2026
- Parsed ownership sources
-
13D/G and 3/4/5
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
VANGUARD GROUP INC
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
3 of 14
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
VANGUARD GROUP INC
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
06 Jan 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001442836
- 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 Mersana 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
VANGUARD GROUP INC
Disclosed value leader
Crossover I. Scsp Nextech
Comparable rows
3/14
Latest evidence
06 Jan 2026
13D/G
3/4/5
Lead comparable stake: 4.2%
11 rows are not safely comparable across share classes.
13D/G row: VANGUARD GROUP INC
Showing 1-8 of 14 holder rows.
Quick read
VANGUARD GROUP INC leads the comparable SEC ownership view at 4.2%.
3 of 14 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 VANGUARD GROUP INC's linked filing trail.
Comparable ownership
Top 3
VANGUARD GROUP INC
4.2%
BlackRock, Inc.
3%
Venrock Healthcare Capital Partne...
2.9%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 14 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| VANGUARD GROUP INC |
13D/G
The Vanguard Group
|
4.2%
|
$6,082,136
210,301 shares
|
$0 | 31 Dec 2025 |
| BlackRock, Inc. |
13D/G
|
3%
|
$1,103,358
3,761,876 shares
|
-$1,338,033 | 30 Jun 2025 |
| Venrock Healthcare Capital Partners III, L.P. |
13D/G
|
2.9%
|
$1,286,757
3,574,325 shares
|
-$2,406,047 | 31 Mar 2025 |
| Crossover I. Scsp Nextech |
3/4/5
10%+ Owner
|
—
class O/S missing
|
$22,927,767
12,067,246 shares
|
— | 20 Dec 2024 |
| EcoR1 Capital, LLC |
3/4/5
10%+ Owner
|
—
mixed-class rows
|
$21,523,200
19,364,688 shares
mixed-class rows
|
— | 19 Dec 2024 |
| Brian DeSchuytner |
3/4/5
SVP, COO & CFO
|
—
mixed-class rows
|
$194,332
62,500 shares
mixed-class rows
|
— | 06 Jan 2026 |
| Alejandra Carvajal |
3/4/5
SVP, Chief Legal Officer
|
—
mixed-class rows
|
$166,917
54,167 shares
mixed-class rows
|
— | 06 Jan 2026 |
| Timothy B. Lowinger |
3/4/5
SVP, Chief Sci.&Tech. Officer
|
—
mixed-class rows
|
$166,917
54,167 shares
mixed-class rows
|
— | 06 Jan 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: -$762.
Buys
$0
Insiders: 0
Sells
$762
Insiders: 1
Net
-$762
Shares: -77
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 77
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 77 | $0 | $762 | -$762 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-18 of 18 reporting-owner rows connected to Mersana Therapeutics, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
18
Largest Forms 3/4/5 holder
Crossover I. Scsp Nextech
Net 12M change
-$762
Latest report
06 Jan 2026
Recent insider transactions for Mersana 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 |
|---|---|---|---|---|---|---|---|---|---|---|
| Andrew A. F. Hack | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -346,545 | 0 | 06 Jan 2026 | See Footnote | ||
| Andrew A. F. Hack | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -578 | 0 | 06 Jan 2026 | Direct | ||
| Andrew A. F. Hack | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -12,609 | 0 | 06 Jan 2026 | Direct | ||
| Kristen Hege | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -578 | 0 | 06 Jan 2026 | Direct | ||
| Kristen Hege | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -14,082 | 0 | 06 Jan 2026 | Direct | ||
| Allene M. Diaz | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -578 | 0 | 06 Jan 2026 | Direct | ||
| Allene M. Diaz | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -9,181 | 0 | 06 Jan 2026 | Direct | ||
| Willard H. Dere | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -1,567 | 0 | 06 Jan 2026 | Direct | ||
| Willard H. Dere | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -11,996 | 0 | 06 Jan 2026 | Direct | ||
| Alejandra Carvajal | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -3,131 | 0 | 06 Jan 2026 | Direct | ||
| Alejandra Carvajal | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -4,483 | 0 | 06 Jan 2026 | Direct | ||
| Alejandra Carvajal | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -31,497 | 0 | 06 Jan 2026 | Direct | ||
| Mohan Bala | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -2,927 | 0 | 06 Jan 2026 | Direct | ||
| Mohan Bala | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -4,950 | 0 | 06 Jan 2026 | Direct | ||
| Mohan Bala | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -32,546 | 0 | 06 Jan 2026 | Direct | ||
| Lawrence M. Alleva | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -84 | 0 | 06 Jan 2026 | See Footnote | ||
| Lawrence M. Alleva | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -578 | 0 | 06 Jan 2026 | Direct | ||
| Lawrence M. Alleva | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -15,247 | 0 | 06 Jan 2026 | Direct | ||
| Martin H. Huber Jr. | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -9,573 | 0 | 06 Jan 2026 | Direct | ||
| Martin H. Huber Jr. | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -21,924 | 0 | 06 Jan 2026 | Direct | ||
| Martin H. Huber Jr. | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -87,257 | 0 | 06 Jan 2026 | Direct | ||
| Ashish Mandelia | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -2,300 | 0 | 06 Jan 2026 | Direct | ||
| Ashish Mandelia | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -1,570 | 0 | 06 Jan 2026 | Direct | ||
| Ashish Mandelia | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -13,602 | 0 | 06 Jan 2026 | Direct | ||
| Anna Protopapas | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -12,499 | 0 | 06 Jan 2026 | See footnote | ||
| Anna Protopapas | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -6,721 | 0 | 06 Jan 2026 | Direct | ||
| Anna Protopapas | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -64,088 | 0 | 06 Jan 2026 | Direct | ||
| Timothy B. Lowinger | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -10,466 | 0 | 06 Jan 2026 | Direct | ||
| Timothy B. Lowinger | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -4,608 | 0 | 06 Jan 2026 | Direct | ||
| Timothy B. Lowinger | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -43,445 | 0 | 06 Jan 2026 | Direct | ||
| David M. Mott | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -383 | 0 | 06 Jan 2026 | See Footnote | ||
| David M. Mott | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -23,546 | 0 | 06 Jan 2026 | Direct | ||
| David M. Mott | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -12,948 | 0 | 06 Jan 2026 | Direct | ||
| Brian DeSchuytner | MRSN | Common Stock | Disposition pursuant to a tender of shares in a change of control transaction | -100% | -5,015 | 0 | 06 Jan 2026 | Direct | ||
| Brian DeSchuytner | MRSN | Restricted Stock Units | Disposed to Issuer | -100% | -5,300 | 0 | 06 Jan 2026 | Direct | ||
| Brian DeSchuytner | MRSN | Stock Option (right to buy) | Disposed to Issuer | -100% | -50,393 | 0 | 06 Jan 2026 | Direct | ||
| Mohan Bala | MRSN | Common Stock | Sale | -2.57% | $762 | $9.90 | -77 | 2,922 | 27 Oct 2025 | Direct |
| Mohan Bala | MRSN | Common Stock | Options Exercise | 9.09% | 250 | 2,999 | 25 Oct 2025 | Direct | ||
| Mohan Bala | MRSN | Restricted Stock Unit | Options Exercise | -100% | -250 | 0 | 25 Oct 2025 | Direct |
* marks a reported price that did not pass the local price check.