Merrimack Announces Preliminary Data From Pilot Diagnostic Imaging Study of MM-398

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CAMBRIDGE, Mass., April 8, 2014 (GLOBE NEWSWIRE) -- Merrimack Pharmaceuticals, Inc. (Nasdaq:MACK) today announced Phase 1 results from a clinical pilot study demonstrating that ferumoxytol*, an iron oxide nanoparticle, was well tolerated when used as a tumor contrast agent prior to MM-398 treatment. Data from the first cohort of patients in this study were presented at the American Association of Cancer Research Annual Meeting, April 5-9, 2014, in San Diego, California.

"This application of ferumoxytol magnetic resonance imaging has the potential to become a minimally invasive predictive biomarker for liposomal therapies. We hope that the continuation and expansion of this approach will allow us to identify patients most likely to benefit from MM-398 treatment," said Jonathan Fitzgerald, Ph.D., Senior Director of Discovery at Merrimack. "Though our initial data are from a small sample of a diverse patient population, we are encouraged to see that almost all of the tumor lesions that shrank after MM-398 treatment were associated with higher levels of ferumoxytol, as seen on the MRI."

Ferumoxytol's propensity for uptake by tumor associated macrophages and similar distribution patterns to MM-398 in preclinical models led to the clinical feasibility study. The ability to image and analyze the levels of ferumoxytol in tumors may be correlated to estimating the MM-398 tumor concentration.

These data are also supported by Merrimack's proprietary Systems Biology approach, as computational modeling of ferumoxytol MRI was used to calculate parameters describing its behavior in tumor tissue. This modeling platform, coupled with the imaging approach with ferumoxytol MRI, may be useful as a predictive biomarker of nanotherapeutics such as MM-398. Primary objectives of this study are to evaluate the feasibility of ferumoxytol to identify tumor-associated macrophages, which may positively correlate with MM-398 activity, and to measure tumor levels of irinotecan and SN-38. The ongoing study has shown that there were no safety-related interactions between ferumoxytol and MM-398 in this preliminary patient population.

Methodology and Results

Pilot study in patients with advanced solid tumors to evaluate feasibility of ferumoxytol (FMX) as tumor imaging agent prior to MM-398, a nanoliposomal irinotecan (nal-IRI) (Poster #CT224)

  • To evaluate the feasibility and safety of ferumoxytol prior to MM-398 treatment, 12 eligible patients were enrolled with refractory solid tumors in multiple indications, including ER/PR-positive breast cancer, pancreatic cancer and ovarian cancer.
  • Scans were performed prior to and following ferumoxytol infusion at 1h, 24h, and 72h. Patients were biopsied at 72h to ferumoxytol high or low regions, and continued on MM-398 treatment at 80 mg/m2 biweekly until progression.
  • Ferumoxytol levels were quantified from Fe-MRI scans and biopsy images. Measurements of tumor tissue analyses and drug metabolites in this study confirmed previous analytics by pharmacokinetic modeling of tumor tissue permeability and binding to ferumoxytol, based on prior preclinical and clinical observations.
  • Overall, ferumoxytol was well tolerated, with no safety-related interactions with MM-398. Adverse events of MM-398 therapy were consistent with previous studies, and no adverse events were directly attributable to ferumoxytol.

About MM-398

MM-398 is a nanoliposomal formulation of irinotecan (nal-IRI). MM-398 is being evaluated in several clinical trials including a Phase 3 study in metastatic pancreatic cancer, a Phase 2 study in patients with metastatic colorectal cancer and a Phase 1 clinical pilot study. MM-398 is not approved for any indication by the U.S. Food and Drug Administration or any other regulatory agency. Under a 2011 agreement with PharmaEngine, Inc. (Taipei, Taiwan), Merrimack consolidated the worldwide development and commercialization rights to MM-398, with the exception of commercialization rights in Taiwan, which are held by PharmaEngine, Inc.

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 applies its systems biology-based approach to biomedical research throughout the research and development process. Merrimack currently has six oncology therapeutics in clinical development. For more information, please visit Merrimack's website at www.merrimackpharma.com.

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 tolerability of MM-398, the potential to develop ferumoxytol as a predictive diagnostic and the potential to identify patients most likely to benefit from MM-398. 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 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on March 4, 2014 and other reports Merrimack files with the SEC.

*Ferumoxytol, commercially available as Feraheme® (AMAG Pharmaceuticals),is an iron-oxide, super-paramagnetic nanoparticle, known to be taken up by macrophages and for exhibiting magnetic resonance imaging properties. The U.S. Food and Drug Administration has approved ferumoxytol for intravenous use as an iron replacement product for the treatment of iron deficiency anemia in adult patients with chronic kidney disease (CKD). The use of ferumoxytol in the pilot study mentioned above is for clinical investigational studies only.

CONTACT: Investor Contact: Geoffrey Grande, CFA Merrimack 617-441-7602 ggrande@merrimackpharma.com Media Contacts: Debbie Tseng Merrimack 617-441-7659 dtseng@merrimackpharma.com Heather Gitlitz Spectrum 202-955-6222 hgitlitz@spectrumscience.com

Source:Merrimack Pharmaceuticals