Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

Nature of Business and Basis of Presentation

Mersana Therapeutics, Inc. is a clinical stage biopharmaceutical company focused on developing antibody drug conjugates (ADCs) that offer a clinically meaningful benefit for cancer patients with significant unmet need. The Company has leveraged over 20 years of industry learning in the ADC field to develop proprietary and differentiated technology platforms that enable it to design ADCs to have improved efficacy, safety and tolerability relative to existing ADC therapies. The Company’s innovative platforms, which include Dolaflexin and Dolasynthen, each delivering its DolaLock payload, as well as Immunosynthen, delivering the novel stimulator of interferon genes (STING) agonist ImmunoLock payload, together provide an efficient product engine that has enabled a robust discovery pipeline for the Company and its partners. The Company’s clinical candidates include upifitamab rilsodotin (UpRi) and XMT-1592. The Company's early stage programs include XMT-1660, a Dolasynthen ADC targeting B7-H4, as well as XMT-2056, a STING agonist ADC developed using the Company's Immunosynthen platform and targeting a novel epitope of human epidermal growth factor receptor 2 (HER2). The Company also has two earlier stage preclinical candidates, XMT-2068 and XMT-2175, both of which leverage the Company's Immunosynthen platform and target tumor-associated antigens.

The Company's lead product candidate, UpRi, is a first-in-class Dolaflexin ADC targeting NaPi2b, an antigen broadly expressed in ovarian cancer and other cancers. The Company is currently evaluating UpRi in platinum-resistant ovarian cancer in a single-arm registrational trial, referred to as UPLIFT, for which the Company expects to complete enrollment in the third quarter of 2022. The Company is also conducting a Phase 1/2 umbrella combination trial, referred to as UPGRADE. The first combination the Company is exploring is the combination of UpRi with carboplatin, a standard platinum chemotherapy broadly used in the treatment of platinum-sensitive ovarian cancer. The Company may explore other combinations in the future. The Company expects to report interim data from UPGRADE in the second half of 2022. In the second quarter of 2022, the Company expects to initiate enrollment in a randomized placebo-controlled Phase 3 trial, referred to as UP-NEXT, to evaluate UpRi as single agent maintenance treatment in patients with recurrent platinum-sensitive ovarian cancer that have high NaPi2b expression.

The Company's second clinical candidate, XMT-1592, is a NaPi2b-targeted ADC leveraging the Dolasynthen platform. The Company is conducting a Phase 1 dose exploration trial in patients with ovarian cancer and non-small cell lung cancer, or NSCLC, which it expects to complete in the second half of 2022.

The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, the need for additional capital, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval and reimbursement for any drug product candidate that it may identify and develop, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development of technological innovations by competitors, reliance on third party manufacturers and the ability to transition from pilot-scale production to large-scale manufacturing of products.

The Company has incurred net losses since inception. The Company’s net loss was $170,060, $88,045 and $28,208 for the years ended December 31, 2021, 2020 and 2019, respectively. The Company expects to continue to incur operating losses for at least the next several years. As of December 31, 2021, the Company had an accumulated deficit of $450,479. The future success of the Company is dependent on, among other factors, its ability to identify and develop its product candidates and ultimately upon its ability to attain profitable operations. The Company has devoted substantially all of its financial resources and efforts to research and development and general and administrative expense to support such research and development. Net losses and negative operating cash flows have had, and will continue to have, an adverse effect on the Company’s stockholders’ equity and working capital.

The Company believes that its currently available funds will be sufficient to fund the Company’s operations through at least the next twelve months from the issuance of this Annual Report on Form 10-K. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) and the rules and regulations of the Securities and Exchange Commission (SEC).

Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (FASB). All dollar amounts, except per share data in the text and tables herein, are stated in thousands unless otherwise indicated.