Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share (MRSN)

Q: What does CUSIP 59045L106 represent in this 13F holders report?

CUSIP 59045L106 is the security identifier for MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share used to aggregate holder disclosures.

Q: How many institutions held MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share in Q3 2025?

5 institutional investors reported MRSN - Mersana Therapeutics, Inc. - Common Stock, par value $0.0001 per share for Q3 2025. Use the holders table for investor-level position and value details.

CUSIP: 59045L106

Q3 2025 13F Holders as of 30 Sep 2025

Security type / class: Equity / Common Stock, par value $0.0001 per share
Total 13F shares: 55,398
Total 13F value: $410,881
Share change: -77,126,542
SEC-reported price per share: $7.76
Number of holders: 5
Value change: -$31,447,580
Number of sells: 77
Shares outstanding: 4,992,318

Security key

59045L106

Report period

Q3 2025

Institutions

Top holders

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

Latest 13F filings Latest 13D/G filings Investors directory

Reporting periods

Holder history for CUSIP 59045L106

Newer quarter: Q4 2025

Recent filing periods:

Q1 2026 Q4 2025

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

Nextech Crossover I GP S....

Disclosed value leader

Crossover I. Scsp Nextech

Comparable rows

4/15

Latest evidence

30 Jun 2025

13D/G 13F 3/4/5 Lead comparable stake: 10% 11 rows are not safely comparable across share classes. 13D/G row: Nextech Crossover I GP S.a r.l. Showing 1-6 of 15 holder rows.

Quick read

Nextech Crossover I GP S.a r.l. leads the comparable SEC ownership view at 10%.

4 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 Nextech Crossover I GP S.a r.l.'s linked filing trail.

Comparable ownership Top 4

Nextech Crossover I GP S.a r.l. 10%

VANGUARD GROUP INC 6.7%

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 1-6 of 15 holder rows

Holder	Evidence	Ownership %	Position	12M Net Δ	As of
Nextech Crossover I GP S.a r.l.	13D/G 13D/G	10% Reported 13D/G · 20 Dec 2024	$4,344,209 12,067,246 shares	$0	20 Dec 2024
VANGUARD GROUP INC	13D/G 13F The Vanguard Group · Company 13D/G 13F	6.7% Reported 13D/G · 31 Mar 2025	$3,015,996 8,377,767 shares	$0	31 Mar 2025
BlackRock, Inc.	13F 13D/G Company 13F 13D/G	3% Reported 13D/G · 30 Jun 2025	$1,113,973 3,763,419 shares	—	30 Jun 2025
Venrock Healthcare Capital Partners III, L.P.	13D/G 13D/G	2.9% Reported 13D/G · 31 Mar 2025	$1,286,757 3,574,325 shares	-$2,406,047	31 Mar 2025
Crossover I. Scsp Nextech	3/4/5 10%+ Owner 3/4/5	— denominator unverified	$22,927,767 12,067,246 shares	—	20 Dec 2024
EcoR1 Capital, LLC	3/4/5 10%+ Owner 3/4/5	— mixed-class rows	$21,523,200 19,364,688 shares mixed-class rows	—	19 Dec 2024

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 Q3 2025

Investor-level positions for this CUSIP, loaded as an interactive table.

Institutions

55,398

Rows available

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 Q3 2025 vs Q4 2025 Across Filers

Q4 2025 holders

Q3 2025 holders

Holder diff

Investor	Q4 2025 Shares	Q3 2025 Shares	Share Diff	Share Chg %	Q4 2025 value	Q3 2025 value	Value change	Value Chg %

Trend: ostatnie 8 kwartałów (+ wybrane okresy porównania).

Quarterly Holders Trend

Quarterly Value Trend

Quarterly Shares Trend