Merrimack Pharmaceuticals Announces Data from an Investigator-Sponsored Phase 1 Study Showing Acceptable Safety Profile for MM-398 in High-Grade Glioma

CHICAGO, June 1, 2015 /PRNewswire/ -- Merrimack Pharmaceuticals, Inc. (Nasdaq: MACK) today announced data for MM-398 (irinotecan liposome injection), also known as ''nal-IRI,'' in a Phase 1 investigator-sponsored study at the University of California, San Francisco for high-grade glioma. Data were presented at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, IL. Results from this study show a tolerable safety profile of MM-398 in patients with high-grade glioma when given intravenously. 

Based in part on the data from this Phase 1 study, investigators at the University of California, San Francisco initiated a new Phase 1 study in November 2014 that is assessing the safety of highly concentrated MM-398 when administered by convection-enhanced drug delivery (CED) in patients with recurrent high-grade glioma. In this new 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. The study is being conducted at a single center at the University of California, San Francisco and will enroll up to 30 patients with recurrent high-grade glioma. A trials-in-progress poster was presented at ASCO detailing the design of this study. For more information visit www.clinicaltrials.gov (Identifier: NCT02022644).

"High-grade glioma is an aggressive disease that often grows and progresses despite surgery and standard of care chemotherapies. These current results from the investigator-sponsored study of MM-398 show promise for the safety of the drug in this indication," said Daryl Drummond, Ph.D., Vice President of Discovery at Merrimack Pharmaceuticals. "We are pleased with the progress of this study and will continue to move MM-398 forward in areas of high unmet medical need, as well as explore novel delivery techniques like CED administration that will best utilize the nanoliposomal design of the drug."

To view the posters presented at ASCO, visit our website at www.merrimackpharma.com.

Methodology and Results

A Phase I trial of intravenous liposomal irinotecan in patients with recurrent high-grade gliomas

MM-398 is a nanoliposomal encapsulation of irinotecan that 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.

• This phase 1 study enrolled patients with recurrent malignant glioma, stratified by UGT1A1*28 genotyping with no prior treatment with irinotecan. Arm 1 of this study enrolled patients with homozygous UGT1A1*28 genotypes with dose increments of 120 mg/m2 from intravenous dosage levels of 120 mg/m2 to 240 mg/m2. Arm 2 of this study enrolled patients with heterozygous UGT1A1*28 genotypes with dose increments of 60 mg/m2 from intravenous dosage levels of 60 mg/m2 to 180 mg/m2.
• Tolerability was similar between the two study arms and was consistent with data from the original phase I study in solid tumors. The maximum tolerated dose (MTD) in Arm 1 was 120 mg/m2; the MTD in Arm 2 was 150 mg/m2.
• MM-398 had no unexpected toxicities when given intravenously. Dose limiting toxicities in both arms of the study included diarrhea, often accompanied by dehydration and/or fatigue.
• The median progression free survival for all patients treated with an initial dose of at least 120 mg/m2 was 43 days.
• The toxicity profile of the drug was considered acceptable enough to move forward with an additional study using convection-enhanced delivery into intracranial tumors, the Phase I study that is currently enrolling at the University of California, San Francisco.

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 has multiple oncology therapeutics in clinical development and additional candidates in late stage preclinical development. Merrimack has submitted a New Drug Application to the U.S. Food and Drug Administration for its lead product candidate, MM-398, for the treatment of patients with metastatic adenocarcinoma of the pancreas who have been previously treated with gemcitabine-based therapy. For more information, please visit Merrimack's website at www.merrimackpharma.com or connect on Twitter at @MerrimackPharma.

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.  PharmaEngine, Inc. (Taipei, Taiwan) holds the rights to commercialize MM-398 in Taiwan.

Forward-Looking Statement

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," and similar expressions. In this press release, Merrimack's forward-looking statements include, among others, statements about the potential effectiveness and tolerability of its investigational therapeutics in certain patient populations or subpopulations. 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 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 May 7, 2015 and other reports Merrimack files with the SEC.

CONTACT: Media Contact:Debbie Tseng, Merrimack617-441-7659[email protected]

Investor Contact:Geoffrey Grande, CFAMerrimack617-441-7602[email protected]

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SOURCE Merrimack Pharmaceuticals, Inc.