BOTHELL, WA--(Marketwire - May 24, 2011) - Marina Biotech, Inc. (NASDAQ: MRNA), a leading RNA-based drug discovery and development company, reported data demonstrating increased hybridization affinity and activity with the Company's proprietary Conformationally Restricted Nucleotide (CRN) technology. When substituted into an oligonucleotide complementary to miR-21, the melting temperature (Tm) was increased significantly; resulting in > 90% inhibition compared to 30% inhibition for a matched all-DNA version. MicroRNA-21 has established roles as an oncomiR in cancer and in proliferative conditions such as cardiac disease. Effective in vivo inhibition of miR-21 is expected to lead to increased expression of known miR-21 target genes. The inhibition of miR-21 and resulting increased gene expression could lead to the development of novel nucleic acid-based therapeutics for the treatment of cancers and other diseases. The data were presented by Michael V. Templin, Ph.D., Senior Vice President, Preclinical Development at Marina Biotech, Inc., at TIDES Oligonucleotide and Peptide® Research, Technology and Product Development May 22 - 25, 2011 in Boston, MA.

"These data represent a significant milestone in the advancement of our CRN technology," stated Dr. Templin. "Nucleic acid-based therapeutics are comprised of a diverse set of oligonucleotide constructs, and CRNs provide a fundamental capability within this space. Increased affinity with CRN substitution allows for the development of highly specific and potent double-stranded and single-stranded oligonucleotides, the latter of which can be delivered in saline-based formulations. CRNs, in conjunction with our other proprietary chemistry and delivery technologies, represent the diverse breadth of nucleic acid-based approaches available to Marina Biotech and its partners, and positions us uniquely in this field."

Conformationally Restricted Nucleotides are analogs in which a chemical bridge connects the C2' and C4' carbons of ribose. Ribose, a five-carbon ring-like structure, forms the central region of a nucleotide (comprised of a nucleobase, ribose, and phosphate group). The chemical bridge in the ribose of a CRN locks the ribose in a fixed position, which in turn restricts the flexibility of the nucleobase and phosphate group. Substitution of a CRN within an RNA- or DNA-based oligonucleotide has the advantages of increased hybridization affinity and enhanced resistance to nuclease degradation. CRN technology provides a direct means of developing highly potent and specific nucleic acid-based therapeutics to target messenger RNAs or microRNAs. These targets represent disease pathways that are typically "undruggable" or "difficult to target" by small molecule or monoclonal antibodies, and are appropriate for disease areas with significant unmet needs, such as inflammation, metabolic disease, and cancers. The CRN patent estate consists of two issued patents broadly covering CRN compounds and CRN containing oligonucleotides, and one pending patent application covering additional applications of CRN's.

About Marina Biotech, Inc.
Marina Biotech is a biotechnology company, focused on the development and commercialization of RNA interference- (RNAi) and RNA-based therapeutics. The Marina Biotech pipeline currently includes a clinical program in Familial Adenomatous Polyposis (a precancerous syndrome) and two preclinical programs -- in bladder cancer and malignant ascites. Marina Biotech has recently entered an exclusive agreement with the Debiopharm Group for the development and commercialization of the bladder cancer program. Marina Biotech's goal is to improve human health through the development of RNAi and RNA-based compounds and drug delivery technologies that together provide superior therapeutic options for patients. Additional information about Marina Biotech is available at http://www.marinabio.com.

Forward-Looking Statements

Statements made in this news release may be forward-looking statements within the meaning of Federal Securities laws that are subject to certain risks and uncertainties and involve factors that may cause actual results to differ materially from those projected or suggested. Factors that could cause actual results to differ materially from those in forward-looking statements include, but are not limited to: (i) the ability of Marina Biotech to obtain additional funding; (ii) the ability of Marina Biotech to attract and/or maintain manufacturing, research, development and commercialization partners; (iii) the ability of Marina Biotech and/or a partner to successfully complete product research and development, including preclinical and clinical studies and commercialization; (iv) the ability of Marina Biotech and/or a partner to obtain required governmental approvals; and (v) the ability of Marina Biotech and/or a partner to develop and commercialize products that can compete favorably with those of competitors. Additional factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statements are contained in Marina Biotech's most recent periodic reports on Form 10-K and Form 10-Q that are filed with the Securities and Exchange Commission. Marina Biotech assumes no obligation to update and supplement forward-looking statements because of subsequent events.