Mersana Therapeutics (United States)

Overview

• IndustryPharmaceutical Preparations¹
• HeadquartersCambridge¹
• Websitewww.mersana.com
• Incorporated inDE³
• Business address840 Memorial Drive, Cambridge, Ma 02139³
• Filer categoryNon-accelerated filer, Smaller reporting company³

See how the biggest companies compare on our leaderboards

We are a clinical-stage biopharmaceutical company focused on developing antibody-drug conjugates, or ADCs, that offer a clinically meaningful benefit for cancer patients with significant unmet need. We have leveraged decades of industry learnings to develop two proprietary and differentiated ADC platforms: Dolasynthen and Immunosynthen. Dolasynthen is our cytotoxic ADC platform that is designed to generate site-specific, homogeneous ADCs. Dolasynthen allows for drug-to-antibody ratios, or DARs, to be optimized for specific targets and utilizes a proprietary auristatin payload that has been shown clinically to avoid dose-limiting severe neutropenia, peripheral neuropathy and ocular toxicity. Immunosynthen is our proprietary STING (stimulator of interferon genes)-agonist platform that is designed to generate systemically administered ADCs that locally activate STING signaling in both antig…⁴ From its latest annual report

Corporate structure

Mersana Therapeutics (United States) sits at the top of its group. 1 entity, 1 country on record. Switch between the flow chart and the network, and select any entity to see its details.

Built from major holders from Schedules 13D and 13G. Each entity in the chart links to its source.

What it owns

What Mersana Therapeutics (United States) reports owning in its annual reports to the SEC: buildings, land and equipment, real estate and locations, investments, intangible assets and inventory, at the end of its latest fiscal year and a year before.

Property and equipment

Investments

Properties, in its own words

Our corporate headquarters are located in Cambridge, Massachusetts. We occupy approximately 45,000 square feet of office and laboratory space that we lease in a multi-tenant building in which our corporate headquarters are located. The lease for the substantial majority of this space expires in March 2026. We are in the process of negotiating a possible extension of the lease term with our landlord. We believe that this office and laboratory space is sufficient to meet our current needs and that suitable additional or alternative space will be available as, if and when needed.

Item 2 of the 10-K filed Mar 3, 2025.⁴

Leadership

Who has led Mersana Therapeutics (United States), and when. Pick a name to see everywhere that person has worked.

• Chief executive officerMartin H. Huber Jr. Sep 13, 2023 to now¹³
• Chief executive officerAnna Protopapas Jun 27, 2017 to Jan 18, 2023¹⁴
• PresidentMartin H. Huber Jr. Sep 13, 2023 to now¹³
• PresidentAnna Protopapas Jun 27, 2017 to Jan 18, 2023¹⁴
• Chief financial officerBrian Deschuytner Jan 19, 2022 to now¹⁵
• Chief financial officerDavid A. Spellman Mar 14, 2018 to Jan 25, 2019¹⁶
• Chief operating officerBrian Deschuytner Sep 7, 2023 to now¹⁷

Former names

• MERSANA THERAPEUTICS INCAug 12, 2008 to Apr 8, 2014³

Timeline

1. Jan 6, 20268-K Ended a material agreement; Completed an acquisition or sale; Listing notice or transfer³⁸
2. Nov 14, 20258-K Results of operations³⁹
3. Nov 13, 20258-K Entered a material agreement; Other events⁴⁰
4. Sep 5, 20258-K Listing notice or transfer⁴¹
5. Aug 13, 20258-K Results of operations⁴²
6. Jul 24, 20258-K Change to shareholders' rights; Bylaws or fiscal year changed⁴³
7. Jul 3, 20258-K Ended a material agreement⁴⁴
8. Jun 13, 20258-K Shareholder vote⁴⁵
9. Jun 2, 20258-K Regulation FD disclosure; Other events⁴⁶
10. May 15, 20258-K Results of operations⁴⁷
11. May 6, 20258-K Exit or restructuring costs; Regulation FD disclosure; Other events⁴⁸
12. Mar 3, 20258-K Results of operations; Regulation FD disclosure⁴⁹
13. Sep 13, 2023New chief executive Martin H. Huber Jr. becomes CEO¹³
14. Jun 27, 2017New chief executive Anna Protopapas becomes CEO¹⁴
15. 2001Founded Founded¹

Calendar

When it reported results

1. Nov 14, 2025Reported quarterly or annual results³⁹
2. Aug 13, 2025Reported quarterly or annual results⁴²
3. May 15, 2025Reported quarterly or annual results⁴⁷
4. Mar 3, 2025Reported quarterly or annual results⁴⁹
5. Nov 13, 2024Reported quarterly or annual results⁵⁰
6. Aug 13, 2024Reported quarterly or annual results⁵¹
7. May 9, 2024Reported quarterly or annual results⁵²
8. Feb 28, 2024Reported quarterly or annual results⁵³

Upcoming dates from Nasdaq's calendar; past results from the company's 8-K filings (Item 2.02). The full markets calendar

Filings

346 filings to the SEC since October 2021: 4 annual reports, 13 quarterly reports, 57 major events, 150 insider forms, 48 large holders, 74 other. The latest 20:

1. May 15, 2026SCHEDULE 13G/A EDGAR
2. Feb 17, 2026SCHEDULE 13G/A EDGAR
3. Feb 17, 2026SCHEDULE 13G/A EDGAR
4. Jan 30, 2026SCHEDULE 13G/A EDGAR
5. Jan 16, 202615-12G EDGAR
6. Jan 9, 2026SCHEDULE 13G/A EDGAR
7. Jan 8, 2026EFFECT EDGAR
8. Jan 8, 2026SCHEDULE 13D/A EDGAR
9. Jan 6, 20264 EDGAR
10. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
11. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
12. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
13. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
14. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
15. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
16. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
17. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
18. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
19. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR
20. Jan 6, 20264 OWNERSHIP DOCUMENT EDGAR

Every filing from the last five years, summarized. The full record is on SEC EDGAR.

Insider trades

71 open-market trades by officers, directors and large owners since October 2021: 16 buys and 55 sales. Grants, option exercises and gifts are left out.

From Forms 4 filed with the SEC.

Major holders

Investors who own more than 5% of the shares must tell the SEC: a 13D if they may seek to influence the company, a 13G if they hold passively.

• 683 Capital Management, LLCSCHEDULE 13G/A, 3 filings Nov 24, 2025 to May 15, 2026⁵⁴
• Schonfeld Strategic Advisors LLCSCHEDULE 13G/A, 4 filings May 15, 2025 to Feb 17, 2026⁵⁵
• VANGUARD GROUP INCSCHEDULE 13G/A, 5 filings Feb 10, 2022 to Jan 30, 2026⁵⁶
• Crossover I. Gp S.a R.l. NextechSCHEDULE 13G/A, 4 filings May 17, 2024 to Jan 9, 2026⁵⁷
• Bain Capital Life Sciences Fund II, L.P.SCHEDULE 13D/A, 7 filings Jan 3, 2022 to Jan 8, 2026⁵⁸
• EcoR1 Capital, LLCSCHEDULE 13G/A, 3 filings Jul 27, 2023 to May 15, 2025⁵⁹
• Venrock Healthcare Capital Partners III, L.P.SCHEDULE 13G/A, 4 filings Aug 7, 2023 to May 15, 2025⁶⁰
• BlackRockSCHEDULE 13G/A, 1 filing Feb 5, 2025⁶¹
• BALYASNY ASSET MANAGEMENT L.P.SC 13G/A, 2 filings Feb 14, 2024 to Nov 14, 2024⁶²
• SILVERARC CAPITAL MANAGEMENT, LLCSC 13G/A, 2 filings Feb 14, 2024 to Oct 15, 2024⁶³
• Avoro Capital Advisors LLCSC 13G/A, 2 filings Feb 14, 2023 to Feb 14, 2024⁶⁴
• ORBIMED ADVISORS LLCSC 13G/A, 2 filings Feb 14, 2023 to Feb 14, 2024⁶⁵
• State Street CorporationSC 13G/A, 3 filings Feb 11, 2022 to Jan 22, 2024⁶⁶
• BB BiotechSC 13G/A, 1 filing Feb 14, 2023⁶⁷
• Rho Ventures V, L.P.SC 13G/A, 1 filing Feb 14, 2023⁶⁸
• Wellington Management CompanySC 13G/A, 2 filings Feb 4, 2022 to Feb 6, 2023⁶⁹
• MILLENNIUM MANAGEMENT LLCSC 13G/A, 2 filings Feb 17, 2022 to Jan 19, 2023⁷⁰

Executive pay

What the company paid its top executives, from the summary compensation table in its proxy statement. Total pay includes salary, bonus, stock and option awards and other pay, as the company valued them.

SEC filer profile

How Mersana Therapeutics (United States) is registered with the Securities and Exchange Commission, from its EDGAR record and the cover page of its latest annual report.

• Name on EDGARMersana Therapeutics, Inc.²
• CIK0001442836
• Employer ID (EIN)04-3562403⁴
• Filer statusNon-accelerated filer not an emerging growth company; a smaller reporting company; not a shell company⁴
• Incorporated inDelaware⁴
• Fiscal year endsDecember 31²
• Industry code (SIC)2834 Pharmaceutical Preparations²
• SEC reviewing officeOffice of Life Sciences, Division of Corporation Finance²
• Business address840 Memorial Drive, Cambridge, MA 02139²
• Phone617-498-0020²
• Shares outstanding4,998,750 as of Nov 7, 2025¹¹
• Public float$226.3M as of Jun 28, 2024⁴
• AuditorErnst & Young LLP, Boston, Massachusetts PCAOB ID 42; no auditor attestation of internal control over financial reporting⁴
• On EDGAR sinceAug 12, 2008²
• Filings704 in all: 4 (291), 8-K (113), 3 (34), SC 13G/A (31), 10-Q (26), SC 13G (25), 144 (20), SCHEDULE 13G/A (15)²
  All 51 form types

  CORRESP (11), SC 13D/A (11), 424B5 (9), S-8 (9), S-8 POS (9), 10-K (8), DEF 14A (8), DEFA14A (8), UPLOAD (7), D (6), EFFECT (6), SC TO-C (4), ARS (3), D/A (3), DRSLTR (3), PRE 14A (3), S-3 (3), SCHEDULE 13G (3), CT ORDER (2), DRS/A (2), POS AM (2), REGDEX (2), S-3/A (2), SC 13D (2), SC 14D9/A (2), SC TO-T/A (2), SC14D9C (2), SCHEDULE 13D/A (2), 15-12G (1), 25-NSE (1), 3/A (1), 4/A (1), 424B4 (1), 8-A12B (1), CERTNAS (1), DRS (1), POSASR (1), S-1 (1), S-1/A (1), S-3ASR (1), S-3MEF (1), SC 14D9 (1), SC TO-T (1)

• Latest filingsAnnual report (10-K) Mar 3, 2025
  Quarterly report (10-Q) Nov 14, 2025
  Proxy statement (DEF 14A) Apr 29, 2025
  Latest 8-K (8-K) Jan 6, 2026

Securities registered for trading

From the cover page of the 10-K filed Mar 3, 2025 (Section 12(b) of the Exchange Act).⁴

Risk factors and legal proceedings

The risks Mersana Therapeutics (United States) names in Item 1A of its 10-K filed Mar 3, 2025: 72 risks under these headings, as written.⁴

• Risks Related to our Financial Position and Need for Additional Capital
• We will require substantial additional financing to achieve our goals, and a failure to obtain this necessary capital when needed could force us to delay, limit, reduce or terminate our product development or future commercialization efforts.
• Our recurring losses from operations raise substantial doubt regarding our ability to continue as a going concern.
• We have incurred net losses since our inception, we have no products approved for commercial sale and we anticipate that we will continue to incur substantial operating losses for at least the next several years. We may never achieve or sustain profitability.
• Raising additional capital may cause dilution to our existing stockholders, restrict our operations or require us to relinquish rights to our technologies or ADC product candidates.
• We have a credit facility that requires us to comply with certain affirmative and negative covenants and places restrictions on our operating and financial flexibility.
• We may expend our resources to pursue a particular product candidate and fail to capitalize on product candidates that may be more profitable or for which there is a greater likelihood of success.
• Risks Related to Development and Approval of Our Antibody-Drug Conjugate, or ADC, Product Candidates
• We are currently evaluating a limited number of ADC product candidates in clinical trials. A failure of any of our product candidates in clinical development would adversely affect our business and may require us to discontinue development of other ADC product candidates based on the same technology.
• Failure of a discovery program or product candidate may occur at any stage of preclinical, non-clinical or clinical development, and, because our and our collaborators' discovery programs and our product candidates are in early stages of preclinical or clinical development, there is a high risk of failure. We or our collaborators may never succeed in obtaining regulatory approval and generating revenue from such discovery programs or product candidates.
• Preliminary, initial, interim and top-line data from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.
• Events that may delay or prevent successful commencement, enrollment or completion of clinical trials of our product candidates could result in increased costs to us as well as a delay in obtaining, or failure to obtain, regulatory approval, or cause us to suspend or terminate a clinical trial, which could prevent us from commercializing our product candidates on a timely basis, or at all.

Legal proceedings

From time to time, we may become subject to various legal proceedings and claims that arise in the ordinary course of our business activities. Regardless of outcome, litigation can have an adverse impact on our business, financial condition, results of operations and prospects because of defense and settlement costs, diversion of management resources and other factors. We are not currently party to any material legal proceedings.

The opening of Item 3, Legal Proceedings.⁴

Links

• Websitewww.mersana.com¹
• WikidataQ104481119
• SEC EDGARCIK 1442836