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Merrimack to Present at the 2018 American Society of Clinical Oncology Annual Meeting

May 29, 2018

CAMBRIDGE, Mass., May 29, 2018 /PRNewswire/ -- Merrimack Pharmaceuticals, Inc. (Nasdaq: MACK), a clinical-stage oncology company focused on biomarker-defined cancers, today announced that it will present two posters at the American Society of Clinical Oncology (ASCO) Annual Meeting, June 1-5, 2018 at McCormick Place North/South in Chicago.

Of particular focus will be clinical data from one of the company's leading therapeutic candidates – seribantumab, also known as MM-121 – an anti-HER3 monoclonal antibody being tested in patients with high expression of heregulin. A poster with an analysis of pharmacokinetic and safety data comparing different dosing regimens from nine previous Phase 1 and Phase 2 studies of seribantumab in solid tumors will be presented. These data support the use of the seribantumab dosing regimen that is currently being evaluated in two ongoing randomized Phase 2 studies in patients with non-small cell lung cancer (NSCLC) and HR+/ HER2- metastatic breast cancer.

Seribantumab is Merrimack's wholly-owned, fully human monoclonal antibody targeting HER3 (ErbB3). By preventing heregulin from binding to the HER3 receptor, MM-121 effectively blocks HER3 activation and as such potently blocks downstream signaling activation and cancer cell survival. Heregulin-positive cancer cells are characterized by their ability to develop resistance to standard of care treatments and escape the effects of targeted, cytotoxic and anti-endocrine therapies. Identification of heregulin-positive cancer cells by RNA-ISH may identify tumors at risk for rapid clinical progression. Seribantumab, when used in the combination setting, is designed to make these cells more responsive to the effects of the combination therapy and deliver improved clinical outcomes.

Merrimack will also present a Trials-In-Progress poster for MM-310, an antibody-directed nanotherapeutic (ADN) targeting the EphA2 receptor, which is currently being evaluated in a Phase 1 study in patients with solid tumors.

Details of Merrimack Presentations:

Evaluation of fixed-dose regimens of seribantumab in patients with solid tumors
Abstract #: 2524
Session Title: Developmental Therapeutics—Clinical Pharmacology and Experimental Therapeutics
Session Subtrack: Antibodies
Date: Monday, June 4, 2018

A phase 1 study evaluating the safety, pharmacology and preliminary activity of MM-310 in patients with solid tumors
Abstract #: TPS2604
Session Title: Developmental Therapeutics—Clinical Pharmacology and Experimental Therapeutics
Session Subtrack: Immunoconjugates
Date: Monday, June 4, 2018

Full details for the 2018 ASCO Annual Meeting can be found at

About Merrimack

Merrimack is a biopharmaceutical company based in Cambridge, Massachusetts that is outthinking cancer to ensure that patients and their families live fulfilling lives. Its mission is to transform cancer care through the smart design and development of targeted solutions based on a deep understanding of cancer pathways and biological markers. All of Merrimack's development programs, including four clinical studies and six candidates in preclinical development, fit into its strategy of 1) understanding the biological problems it is trying to solve, 2) designing specific solutions and 3) developing those solutions for biomarker-selected patients. This three-pronged strategy seeks to ensure optimal patient outcomes. For more information, please visit Merrimack's website at

Forward Looking Statements

To the extent that statements contained in this press release are not descriptions of historical facts, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements include any statements about Merrimack's strategy, future operations, future financial position, future revenues and future expectations and plans and prospects for Merrimack, and any other statements containing the words "anticipate," "believe," "estimate," "expect," "intend," "may," "plan," "predict," "project," "target," "potential," "will," "would," "could," "should," "continue" and similar expressions. In this press release, Merrimack's forward-looking statements include, among others, statements about the potential effectiveness of MM-121, the ability to use heregulin as a predictive diagnostic and the ability to translate clinical data into future clinical success. Such forward-looking statements involve substantial risks and uncertainties that could cause Merrimack's clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the initiation of future clinical trials, availability of data from ongoing clinical trials, expectations for regulatory approvals, development progress of Merrimack's companion diagnostics, availability of funding sufficient for Merrimack's foreseeable and unforeseeable operating expenses and capital expenditure requirements, and other matters that could affect the availability or commercial potential of Merrimack's product candidates or companion diagnostics. Merrimack undertakes no obligation to update or revise any forward-looking statements. Forward-looking statements should not be relied upon as representing Merrimack's views as of any date subsequent to the date hereof. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Merrimack's business in general, see the "Risk Factors" section of Merrimack's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on May 8, 2018 and the other reports Merrimack files with the SEC.


Geoffrey Grande, CFA 

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SOURCE Merrimack Pharmaceuticals, Inc.