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Merrimack Pharmaceuticals Announces Initiation of Phase 1 Clinical Study of MM-398 for Brain Cancer

CAMBRIDGE, Mass., Nov. 6, 2014 (GLOBE NEWSWIRE) -- Merrimack Pharmaceuticals, Inc. (Nasdaq:MACK) today announced that the first patient has been enrolled in a Phase 1 clinical study of MM-398 (nanoliposomal irinotecan injection) in a highly concentrated formulation in patients with recurrent high grade glioma, a type of aggressive brain tumor with poor prognosis. The study is being sponsored and conducted by Dr. Nicholas Butowski, M.D., Associate Professor of Neurological Surgery and Principal Investigator of the study at the University of California, San Francisco, and is supported by research grants from the National Institutes of Health and Merrimack.

"There are few options for patients with recurrent high grade gliomas, as these types of aggressive brain tumors often grow back after surgery and radiotherapy," said Daryl Drummond, Vice President of Discovery at Merrimack. "We have seen encouraging results administering this highly concentrated formulation of MM-398 in a veterinary study of canines diagnosed with spontaneous brain tumors, where MM-398 was shown to extend quality of life and survival, and we are pleased to support Dr. Butowski's research."

The Phase 1, dose-escalating, open label study will assess the safety of highly concentrated MM-398 when administered by convection-enhanced drug delivery in patients with recurrent high grade glioma. In this study, MM-398 will be administered with gadoteridol, an MRI imaging agent to enable the real time visualization of drug distribution in the brain, through a small catheter that allows for the drug to be injected directly into the brain tumor – an approach called convection-enhanced drug delivery. Due to the small injection volume required for this method of delivery, a highly concentrated formulation of MM-398 was specifically developed by Merrimack. The study is being conducted at a single center at the University of California, San Francisco and will enroll up to 36 patients with recurrent high grade glioma. For more information visit www.clinicaltrials.gov (Identifier: NCT02022644).

"The blood-brain barrier is known to limit the effective delivery of anti-cancer therapies," said Dr. Butowski. "By utilizing an imaging-guided, direct-injection technique to deliver MM-398, we hope to increase the cytotoxic effects of the drug on the tumor with less peripheral toxicity and fewer side effects. MM-398 is an excellent candidate for convection-enhanced delivery due to its nanoliposomal design, which may allow the drug to be stably deposited in the tumor, thereby prolonging exposure of the tumor to the drug."

Additional preclinical research completed by collaborators at the University of California, San Francisco, has shown that convection-enhanced delivery of MM-398 results in tumor-drug concentrations up to 100-fold higher than concentrations achieved with standard intravenous injection, as well as significantly enhanced activity, which could translate into an increase in drug activation and duration of benefit in tumors cells.

MM-398, also known as "nal-IRI," is an investigational drug candidate being developed for the treatment of patients with metastatic pancreatic cancer previously treated with a gemcitabine-based therapy. Merrimack is currently preparing a New Drug Application for MM-398.

About High Grade Glioma

High grade gliomas are the most common form of brain tumors in adults, with a diagnosis rate of 15,000 cases per year in the United States. Current treatments for high grade gliomas include radiation and chemotherapy after surgical removal, but prognosis remains poor despite standard therapy. The median survival for patients with anaplastic astrocytomas and glioblastoma multiforme, the two subtypes of high grade glioma, is 24-36 months and 6-12 months, respectively.

About MM-398

MM-398 (irinotecan liposome injection), also known as "nal-IRI," is a nanoliposomal encapsulation of the chemotherapeutic irinotecan. MM-398 has demonstrated extended circulation in comparison to free irinotecan in the clinical setting. The activated form of irinotecan is SN-38, which functions by inhibiting topoisomerase I (an essential enzyme involved in DNA transcription and replication) and promoting cell death. In 2014, Merrimack and Baxter International's biopharmaceutical business (NYSE:BAX) entered into an exclusive licensing agreement to develop and commercialize MM-398 outside of the United States and Taiwan. PharmaEngine, Inc. (Taipei, Taiwan) holds the rights to commercialize MM-398 in Taiwan.

About Merrimack

Merrimack is a biopharmaceutical company discovering, developing and preparing to commercialize innovative medicines paired with companion diagnostics for the treatment of cancer. Merrimack seeks to gain a deeper understanding of underlying cancer biology through its systems biology-based approach and develop new insights, therapeutics and diagnostics to improve outcomes for cancer patients. Merrimack currently has six oncology therapeutics in clinical development and three additional candidates in late stage preclinical development. Merrimack's lead product candidate, MM-398, recently completed a Phase 3 trial in post-gemcitabine pancreatic cancer. Based on the results of this trial, Merrimack is currently preparing a New Drug Application for MM-398. For more information, please visit Merrimack's website at www.merrimackpharma.com or connect with us on Twitter at @MerrimackPharma.

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 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," "hope" and similar expressions. In this press release, Merrimack's forward-looking statements include statements about the potential effectiveness and safety profile of MM-398 in general and in the context of this clinical trial. 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, availability of data from ongoing clinical trials, expectations for regulatory approvals, development progress of Merrimack's companion diagnostics and other matters that could affect the availability or commercial potential of Merrimack's drug 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 August 11, 2014 and other reports Merrimack files with the SEC.

CONTACT: Media Contacts: Debbie Tseng, Merrimack 617-441-7659 dtseng@merrimackpharma.com Liz Bryan, Spectrum 202-955-6222 lbryan@spectrumscience.com

Source:Merrimack Pharmaceuticals