- New Paper Documents Previously Presented Proof-of-Concept Results in Mouse Model of Acute Intermittent Porphyria (AIP) -

- RNAi Therapeutics Targeting ALAS-1 Completely Block Production of Toxic Heme Biosynthesis Intermediates that Cause Symptoms and Disease Pathology -

CAMBRIDGE, Mass.--(BUSINESS WIRE)-- Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today the publication in the Proceedings of the National Academy of Sciences (PNAS) of pre-clinical results with RNAi therapeutics targeting aminolevulinic acid synthase-1 (ALAS-1) for the treatment of hepatic porphyrias, including acute intermittent porphyria (AIP). In the paper, titled "RNAi-mediated silencing of hepatic Alas1 effectively prevents and treats the induced acute attacks in acute intermittent porphyria mice," Alnylam scientists and collaborators at the Icahn School of Medicine at Mount Sinai in New York City documented results from pre-clinical models of the human disease showing that RNAi therapeutics targeting ALAS-1 can completely block the abnormal production of toxic intermediates of the heme biosynthesis pathway that cause the symptoms and disease pathology of AIP. This new paper provides proof of concept for an RNAi therapeutic for the treatment of AIP.

"Our data in a mouse model of AIP, now published in PNAS, demonstrate that RNAi therapeutics targeting ALAS-1 can achieve potent, rapid, and durable suppression of the toxic heme biosynthesis intermediates that cause the symptoms and disease pathology of AIP. As such, these findings provide key pre-clinical proof-of-concept data for our ALN-AS1 program. We believe ALN-AS1 has the potential to be a transformative therapy for patients with hepatic porphyrias including AIP, an ultra-rare genetic disease with enormous unmet medical need," said Rachel Meyers, Ph.D., Vice President, Research and RNAi Lead Development of Alnylam. "We are currently advancing our Development Candidate for ALN-AS1, which employs our Enhanced Stabilization Chemistry-GalNAc-conjugate technology. This technology enables subcutaneous dosing with improved potency and durability, and a wide therapeutic index, and is now clinically validated based on results from our hemophilia program. We are on track to file an Investigational New Drug application for ALN-AS1 in late 2014 or early 2015, and look forward to advancing this investigational medicine to patients."

The acute hepatic porphyrias, including AIP, are ultra-rare orphan diseases caused by loss-of-function mutations in enzymes involved in heme biosynthesis, leading to accumulation of toxic heme intermediate precursors. In the case of AIP, there are approximately 5,000 patients in the U.S. and Europe that suffer acute, life-threatening porphyria attacks every year; there are approximately 500 patients afflicted with recurrent debilitating attacks, often occurring once per month. Treatment options for AIP patients suffering from an attack are limited, and include the use of heme preparations that show limited efficacy and are associated with a number of complications including phlebitis, iron overload, and infections related to the need for central venous access in some patients. Currently, there are no approved drugs available to prevent attacks from occurring. Alnylam's approach is to knock down ALAS-1, an enzyme upstream of porphobilinogen deaminase (PBGD), the defective gene in AIP. RNAi-mediated silencing of hepatocyte ALAS-1 could reduce the abnormal production of the toxic heme intermediates, specifically aminolevulinic acid (ALA) and porphobilinogen (PBG), which mediate the symptoms and disease pathology in AIP patients as well as in some of the other acute hepatic porphyrias. Alnylam believes that a subcutaneously administered RNAi therapeutic targeting ALAS-1 has the potential to be used as a prophylactic approach to prevent attacks, and also as a therapy for acute attacks.

In the new paper published in PNAS, Alnylam scientists and collaborators at the Icahn School of Medicine at Mount Sinai documented their results from studies performed in a mouse model of AIP. Prophylactic administration of an ALAS-1 specific siRNA completely protected AIP mice from phenobarbital-induced up-regulation of hepatic ALAS-1 mRNA and protein, as well as the resulting accumulation of the neurotoxic ALA and PBG heme biosynthesis precursors. This protective effect was dose responsive and durable, with a single dose administration resulting in a protective effect that lasted for at least two weeks. This feature provides an advantage over prophylactic hemin - the current standard of care in AIP - which is infused as often as twice a week in patients with frequent attacks. Further, in a treatment model, a single dose of ALAS-1 siRNA rapidly reduced the high levels of plasma ALA and PBG that were elevated during a phenobarbital-induced acute attack. In addition, preliminary comparative studies show that ALAS-1 siRNA administration was more effective than heme administration in the treatment of an acute attack, as seen by the more extensive and rapid lowering of both ALA and PBG with its administration. New results from rotarod studies showed that treatment with an ALAS-1 siRNA was associated with a significant improvement in performance as compared with animals treated with a control siRNA, suggesting that treatment with the drug can protect against symptoms of neuromotor impairment associated with AIP attacks. Finally, data were shown demonstrating that administration of ALAS-1 siRNA was not associated with a hepatic heme deficiency or altered liver hemoprotein activity.

"AIP is caused by an inherited deficiency in porphobilinogen deaminase that can result in accumulation of toxic intermediates in the heme biosynthesis pathway. Patients with AIP present with acute, and at times recurrent attacks that are characterized by severe abdominal pain, peripheral and autonomic neuropathy, neuropsychiatric manifestations, and in very severe cases paralysis and respiratory failure," said Robert J. Desnick, M.D., Ph.D., Dean for Genetics and Genomic Medicine and Professor and Chair Emeritus of the Department of Genetics and Genomic Sciences at the Icahn School of Medicine at Mount Sinai in New York City. "Our pre-clinical work in a mouse model of AIP has shown that RNAi-mediated silencing of ALAS-1 results in rapid and effective normalization of the toxic heme biosynthesis intermediates ALA and PBG that cause the symptoms and pathophysiology of the disease. In addition, treatment with ALAS-1 siRNA in the model led to more rapid and effective lowering of ALA and PBG than a single hemin infusion, which is the standard of care for patients who have acute hepatic porphyria attacks. We have also now shown that RNAi knockdown of ALAS-1 improves the neuromotor impairment associated with acute attacks, and is not associated with a hepatic heme deficiency."

"RNAi therapeutics are promising as a novel treatment for AIP, and the other acute hepatic porphyrias, where there is a clear need for new therapies," said Makiko Yasuda, M.D., Ph.D., Assistant Professor in the Department of Genetics and Genomic Sciences at the Icahn School of Medicine at Mount Sinai in New York City. "We look forward to continuing our very close collaborative efforts with Alnylam on the advancement of this program to the clinic."

Alnylam is currently advancing ALN-AS1, a subcutaneously administered RNAi therapeutic targeting ALAS-1 for the treatment of porphyria, including AIP. ALN-AS1 utilizes the company's proprietary Enhanced Stabilization Chemistry (ESC)-GalNAc-conjugate technology, which enables subcutaneous dosing with increased potency and durability, and a wide therapeutic index. ESC-GalNAc conjugates are a clinically validated platform based on recent results from the company's ALN-AT3 program in a Phase 1 study. At the 9^th Annual Meeting of the Oligonucleotide Therapeutics Society in October 2013, the company presented results in non-human primates (NHP), showing that multi-dose administration of an ESC-GalNAc-siRNA targeting ALAS-1 led to rapid, dose-dependent, and long-lasting knockdown of the ALAS-1 mRNA in NHPs, with an ED₅₀ of approximately 1.25 mg/kg. Further, in a rat model of AIP, ALN-AS1 administration at doses as low as 2.5 mg/kg resulted in a complete blunting of phenobarbital-induced over-production of PBG and ALA, the toxic heme intermediates in AIP. Alnylam is currently conducting additional studies with ALN-AS1 and expects to file an Investigational New Drug (IND) application or IND equivalent in late 2014 or early 2015.

Dr. Robert Desnick and Dr. Makiko Yasuda are named with Alnylam Pharmaceuticals as co-inventors on a pending patent covering compositions and methods for inhibiting the ALAS-1 gene. In addition, Dr. Desnick receives financial compensation as a consultant for Alnylam Pharmaceuticals, and owns equity in Alnylam Pharmaceuticals in the form of stock options.

About Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) is an ultra-rare autosomal dominant disease caused by loss-of-function mutations in porphobilinogen deaminase (PBGD), an enzyme in the heme biosynthesis pathway. Exposure of AIP patients to certain drugs, dieting, or hormonal changes can trigger strong induction of aminolevulinic acid synthase-1 (ALAS-1), another enzyme in the heme biosynthesis pathway, which can lead to accumulation of heme intermediates upstream of PBGD that precipitate attack symptoms. Patients with AIP can suffer acute and/or recurrent life-threatening attacks with severe abdominal pain, peripheral and autonomic neuropathy, neuropsychiatric manifestations, and possibly death if left untreated. Approximately 5,000 patients in the U.S. and Europe suffer acute porphyria attacks annually, and approximately 500 patients are afflicted with recurrent debilitating attacks. Treatment options for AIP patients suffering from an acute attack are limited; patients are treated with intravenous heme analogues that have a slow onset and can result in severe thrombophlebitis and iron overload. Currently there is no approved prophylactic treatment available to prevent recurrent attacks, which often occur monthly in women associated with menses. There exists a significant need for therapies for AIP patients.

About GalNAc Conjugates and Enhanced Stabilization Chemistry (ESC)-GalNAc Conjugates

GalNAc-siRNA conjugates are a proprietary Alnylam delivery platform and are designed to achieve targeted delivery of RNAi therapeutics to hepatocytes through uptake by the asialoglycoprotein receptor. Alnylam's Enhanced Stabilization Chemistry (ESC)-GalNAc-conjugate technology enables subcutaneous dosing with increased potency and durability, and a wide therapeutic index. This delivery platform is being employed in several of Alnylam's genetic medicine programs, including programs in clinical development.

About LNP

Alnylam has licenses to Tekmira LNP intellectual property for use in RNAi therapeutic products using LNP technology.

About RNAi

RNAi (RNA interference) is a revolution in biology, representing a breakthrough in understanding how genes are turned on and off in cells, and a completely new approach to drug discovery and development. Its discovery has been heralded as "a major scientific breakthrough that happens once every decade or so," and represents one of the most promising and rapidly advancing frontiers in biology and drug discovery today which was awarded the 2006 Nobel Prize for Physiology or Medicine. RNAi is a natural process of gene silencing that occurs in organisms ranging from plants to mammals. By harnessing the natural biological process of RNAi occurring in our cells, the creation of a major new class of medicines, known as RNAi therapeutics, is on the horizon. Small interfering RNA (siRNA), the molecules that mediate RNAi and comprise Alnylam's RNAi therapeutic platform, target the cause of diseases by potently silencing specific mRNAs, thereby preventing disease-causing proteins from being made. RNAi therapeutics have the potential to treat disease and help patients in a fundamentally new way.

About Alnylam Pharmaceuticals

Alnylam is a biopharmaceutical company developing novel therapeutics based on RNA interference, or RNAi. The company is leading the translation of RNAi as a new class of innovative medicines with a core focus on RNAi therapeutics as genetic medicines, including programs as part of the company's "Alnylam 5x15^TM" product strategy. Alnylam's genetic medicine programs are RNAi therapeutics directed toward genetically defined targets for the treatment of serious, life-threatening diseases with limited treatment options for patients and their caregivers. These include: patisiran (ALN-TTR02), an intravenously delivered RNAi therapeutic targeting transthyretin (TTR) for the treatment of TTR-mediated amyloidosis (ATTR) in patients with familial amyloidotic polyneuropathy (FAP); ALN-TTRsc, a subcutaneously delivered RNAi therapeutic targeting TTR for the treatment of ATTR in patients with TTR cardiac amyloidosis, including familial amyloidotic cardiomyopathy (FAC) and senile systemic amyloidosis (SSA); ALN-AT3, an RNAi therapeutic targeting antithrombin (AT) for the treatment of hemophilia and rare bleeding disorders (RBD); ALN-CC5, an RNAi therapeutic targeting complement component C5 for the treatment of complement-mediated diseases; ALN-AS1, an RNAi therapeutic targeting aminolevulinic acid synthase-1 (ALAS-1) for the treatment of hepatic porphyrias including acute intermittent porphyria (AIP); ALN-PCS, an RNAi therapeutic targeting PCSK9 for the treatment of hypercholesterolemia; ALN-AAT, an RNAi therapeutic targeting alpha-1 antitrypsin (AAT) for the treatment of AAT deficiency-associated liver disease; ALN-TMP, an RNAi therapeutic targeting TMPRSS6 for the treatment of beta-thalassemia and iron-overload disorders; ALN-ANG, an RNAi therapeutic targeting angiopoietin-like 3 (ANGPTL3) for the treatment of genetic forms of mixed hyperlipidemia and severe hypertriglyceridemia; ALN-AC3, an RNAi therapeutic targeting apolipoprotein C-III (apoCIII) for the treatment of hypertriglyceridemia; and other programs yet to be disclosed. As part of its "Alnylam 5x15" strategy, as updated in early 2014, the company expects to have six to seven genetic medicine product candidates in clinical development - including at least two programs in Phase 3 and five to six programs with human proof of concept - by the end of 2015. Alnylam is also developing ALN-HBV, an RNAi therapeutic targeting the hepatitis B virus (HBV) genome for the treatment of HBV infection. The company's demonstrated commitment to RNAi therapeutics has enabled it to form major alliances with leading companies including Merck, Medtronic, Novartis, Biogen Idec, Roche, Takeda, Kyowa Hakko Kirin, Cubist, GlaxoSmithKline, Ascletis, Monsanto, The Medicines Company, and Genzyme, a Sanofi company. In March 2014, Alnylam acquired Sirna Therapeutics, a wholly owned subsidiary of Merck. In addition, Alnylam holds an equity position in Regulus Therapeutics Inc., a company focused on discovery, development, and commercialization of microRNA therapeutics. Alnylam scientists and collaborators have published their research on RNAi therapeutics in over 200 peer-reviewed papers, including many in the world's top scientific journals such as Nature, Nature Medicine, Nature Biotechnology, Cell, the New England Journal of Medicine, and The Lancet. Founded in 2002, Alnylam maintains headquarters in Cambridge, Massachusetts. For more information, please visit www.alnylam.com.

About "Alnylam 5x15™" and Genetic Medicines

The "Alnylam 5x15" strategy, launched in January 2011, establishes a path for development and commercialization of novel RNAi therapeutics as genetic medicines. Alnylam's genetic medicine programs are RNAi therapeutics directed toward genetically defined targets for the treatment of diseases with high unmet medical need. These programs share several key characteristics including: a genetically defined target and disease expressed in the liver; the potential to have a major impact in a high unmet need population; the ability to leverage the existing Alnylam RNAi platform with clinically proven delivery to the liver; the opportunity to monitor an early biomarker in Phase 1 clinical trials for human proof of concept; and the existence of clinically relevant endpoints for the filing of a new drug application (NDA) with a focused patient database and possible accelerated paths for commercialization. As updated in early 2014, the company expects to have six to seven genetic medicine product candidates in clinical development - including at least two programs in Phase 3 and five to six programs with human proof of concept - by the end of 2015. The "Alnylam 5x15" programs include: patisiran (ALN-TTR02), an intravenously delivered RNAi therapeutic targeting transthyretin (TTR) in development for the treatment of TTR-mediated amyloidosis (ATTR) in patients with familial amyloidotic polyneuropathy (FAP); ALN-TTRsc, a subcutaneously delivered RNAi therapeutic targeting TTR in development for the treatment of ATTR in patients with TTR cardiac amyloidosis, including familial amyloidotic cardiomyopathy (FAC) and senile systemic amyloidosis (SSA); ALN-AT3, an RNAi therapeutic targeting antithrombin (AT) in development for the treatment of hemophilia and rare bleeding disorders (RBD); ALN-CC5, an RNAi therapeutic targeting complement component C5 in development for the treatment of complement-mediated diseases; ALN-AS1, an RNAi therapeutic targeting aminolevulinic acid synthase-1 (ALAS-1) in development for the treatment of hepatic porphyrias including acute intermittent porphyria (AIP); ALN-PCS, an RNAi therapeutic targeting PCSK9 in development for the treatment of hypercholesterolemia; ALN-AAT, an RNAi therapeutic targeting alpha-1 antitrypsin (AAT) for the treatment of AAT deficiency-associated liver disease; ALN-TMP, an RNAi therapeutic targeting TMPRSS6 in development for the treatment of beta-thalassemia and iron-overload disorders; ALN-ANG, an RNAi therapeutic targeting angiopoietin-like 3 (ANGPTL3) for the treatment of genetic forms of mixed hyperlipidemia and severe hypertriglyceridemia; ALN-AC3, a subcutaneously administered RNAi therapeutic targeting apolipoprotein C-III (apoCIII) for the treatment of hypertriglyceridemia; and other programs yet to be disclosed. In 2014, Alnylam and Genzyme, a Sanofi company, formed a multi-product geographic alliance on Alnylam's genetic medicine programs. Specifically, Alnylam will lead development and commercialization of programs in North America and Europe, while Genzyme will develop and commercialize products in the rest of world. In addition, Alnylam and Genzyme will co-develop and co-commercialize ALN-TTRsc in North America and Europe.

Alnylam Forward-Looking Statements

Various statements in this release concerning Alnylam's future expectations, plans and prospects, including without limitation, Alnylam's views with respect to the potential for RNAi therapeutics, including ALN-AS1 for the treatment of porphyria including acute intermittent porphyria (AIP), its expectations with respect to timing, and success of its clinical trials, including with ALN-AS1, its expectations regarding the potential market opportunity for ALN-AS1, its expectations regarding its "Alnylam 5x15" product strategy, and its plans regarding commercialization of RNAi therapeutics, constitute forward-looking statements for the purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including, without limitation, Alnylam's ability to manage operating expenses, Alnylam's ability to discover and develop novel drug candidates and delivery approaches, successfully demonstrate the efficacy and safety of its drug candidates, the pre-clinical and clinical results for its product candidates, which may not support further development of product candidates, actions of regulatory agencies, which may affect the initiation, timing and progress of clinical trials, obtaining, maintaining and protecting intellectual property, Alnylam's ability to enforce its patents against infringers and defend its patent portfolio against challenges from third parties, obtaining regulatory approval for products, competition from others using technology similar to Alnylam's and others developing products for similar uses, Alnylam's ability to obtain additional funding to support its business activities and establish and maintain strategic business alliances and new business initiatives, Alnylam's dependence on third parties for development, manufacture, marketing, sales and distribution of products, the outcome of litigation, and unexpected expenditures, as well as those risks more fully discussed in the "Risk Factors" filed with Alnylam's most recent Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) and in other filings that Alnylam makes with the SEC. In addition, any forward-looking statements represent Alnylam's views only as of today and should not be relied upon as representing its views as of any subsequent date. Alnylam explicitly disclaims any obligation to update any forward-looking statements.

Alnylam Pharmaceuticals, Inc.
Cynthia Clayton, 617-551-8207
Vice President, Investor Relations and
Corporate Communications
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Source: Alnylam Pharmaceuticals, Inc.

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