Alnylam Reports Positive ALN-TTR02 Clinical Data, with Robust Knockdown of Serum Transthyretin (TTR) of up to 94% After Single Dose

Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, announced today the achievement of positive clinical results from its Phase I trial with ALN-TTR02, an RNAi therapeutic targeting the transthyretin (TTR) gene for the treatment of TTR-mediated amyloidosis (ATTR). The data were presented today in a seminar by Alnylam scientists at Boston University School of Medicine. Results from this study show that administration of ALN-TTR02 leads to robust knockdown of serum TTR protein levels of up to 94%; the overall results were highly significant (p<0.00001 by ANOVA). Suppression of TTR, the disease-causing protein in ATTR, was found to be rapid, dose dependent, durable, and specific after just a single dose. Alnylam recently reported that it has initiated a Phase II study of ALN-TTR02 in patients with ATTR and has guided that its goal is to start a pivotal trial in 2013.

“We are very excited with these new ALN-TTR02 results, where we have achieved very robust effects, including up to 94% reduction of serum TTR and a nearly 80% level of suppression sustained at one month with just a single dose. These results document an unprecedented level of clinical activity for RNAi therapeutics and strongly support advancement of this innovative program to meet the needs of ATTR patients,” said Akshay Vaishnaw, M.D., Ph.D., Executive Vice President and Chief Medical Officer of Alnylam. “Knockdown of circulating TTR is a validated endpoint in ATTR based on data from patients receiving liver transplants. Further, evidence from other systemic amyloidotic diseases shows that as little as a 50 percent reduction of the disease-causing protein can result in disease improvement or stabilization. Accordingly, these data with ALN-TTR02 provide key human proof of concept with associated clinical relevance as we advance this medicine to patients for the treatment of ATTR, a debilitating orphan genetic disease. We look forward to continuing to share clinical data from our ALN-TTR02 program, and, assuming positive results in the current Phase II study, we plan to advance to a pivotal trial in 2013.”

“I am very encouraged by these new data with ALN-TTR02, an RNAi therapeutic for the treatment of ATTR. Specifically, I am impressed with the almost complete knockdown of TTR after just a single dose of drug, which is important since TTR protein reduction in patients with ATTR has the potential to delay or even reverse disease progression with associated clinical benefits,” said Teresa Coelho, M.D., Director, Unidade Clinica de Paramiloidose. “I look forward to the continued advancement of RNAi therapeutics in clinical trials for the treatment of ATTR, as there are currently few options for patients suffering from this devastating disease.”

The Phase I trial of ALN-TTR02 was conducted in the U.K. as a randomized, single-blind, placebo-controlled, single-ascending dose study, and enrolled 17 healthy volunteer subjects. The primary objective of the study was to evaluate the safety and tolerability of a single dose of ALN-TTR02, with subjects being enrolled into five sequential cohorts of increasing doses ranging from 0.01 to 0.50 mg/kg. In addition, pharmacodynamic activity was evaluated with serial measurements of serum TTR protein levels through at least day 56. Serum TTR levels were measured by an ELISA assay and also by a turbidometric assay method.

Preliminary data from this study showed that a single dose of ALN-TTR02 resulted in rapid, dose-dependent, durable, and specific knockdown of serum TTR levels. Even at doses as low as 0.15 mg/kg, substantial serum TTR suppression was achieved, with a mean 81.9% knockdown at nadir. At a dose of 0.30 mg/kg, an 86.8% mean knockdown was achieved at nadir, with a mean 66.7% reduction still observed 28 days post-dose. In the one subject treated at 0.50 mg/kg, knockdown of 93.8% was observed at nadir, with 76.8% reduction maintained at day 28. ALN-TTR02 exhibited a rapid onset of action; over 50% knockdown in TTR was achieved by day three in all of the 0.15, 0.30, and 0.50 mg/kg subjects, and nadir levels were achieved by day 10 to 14. In addition, time courses for TTR reduction showed highly consistent pharmacologic effects, with minimal inter-subject variability in maximal levels of TTR suppression (<5% relative standard deviation among 0.15 and 0.30 mg/kg subjects). Using a turbidometric assay method to measure TTR, 3 of 4 (75%) subjects receiving ALN-TTR02 in the 0.30 and 0.50 mg/kg dose groups showed undetectable levels of serum TTR on one or more post-dose days. As expected, serum TTR reductions were highly correlated with parallel changes in retinol binding protein (RBP) (r²=0.83) and vitamin A levels (r²=0.86). The effects of ALN-TTR02 were also determined to be specific, as subjects (n=6) treated at a 0.4 mg/kg dose of an siRNA targeting PCSK9 in the identical lipid nanoparticle (LNP) formulation showed no significant serum TTR reduction in a separate, recently completed Phase I study. As a result of the positive pharmacology seen at doses as low as 0.15 mg/kg, dosing at 0.50 mg/kg was limited to one patient, allowing for the start of the Phase II study with ALN-TTR02 in ATTR patients. Alnylam believes that these robust and durable knockdown data support a once-a-month or possibly once-every-other month dosing regimen, and intends to examine this further in the ongoing Phase II study. The key results from the Phase I study are summarized in the table below.

ALN-TTR02 was found to be generally safe and well tolerated in this Phase I study, consistent with Alnylam’s broader clinical experience with LNP-formulated siRNA which now includes 102 patients or subjects, 334 total doses administered, and a length of treatment exceeding two years. There were no serious adverse events or discontinuations in the study related to ALN-TTR02 and there were no significant adverse events associated with drug up through 0.30 mg/kg. A moderate acute infusion reaction was observed in one subject receiving ALN-TTR02 at 0.50 mg/kg who was able to complete dosing with slowing of the infusion rate. There were no laboratory abnormalities, including no changes in liver function tests, cytokines, or C-reactive protein (CRP).

“In our continued efforts to advance RNAi therapeutics to patients, we believe these data with ALN-TTR02 establish new industry milestones. First, these results demonstrate the highly robust level of target gene knockdown and attractive pharmacologic profile achievable with RNAi therapeutics. Further and for the first time, we have generated data using a control siRNA from a parallel study documenting the specificity for RNAi therapeutics in humans,” said John Maraganore, Ph.D., Chief Executive Officer of Alnylam. “Finally, these results mark important progress in our overall ‘Alnylam 5x15’ product strategy efforts. While there is more to do in our efforts to bring RNAi therapeutics to patients in need, we are very encouraged by this significant step forward.”

Alnylam is advancing ALN-TTR02 in a Phase II study which is designed as an open-label, multi-center, multi-dose, dose-escalation trial expected to enroll approximately 20 ATTR patients. Patients will be enrolled into cohorts of increasing doses and will receive drug once every four weeks for two cycles. The primary objectives of the study are to evaluate the safety and tolerability of multiple doses of ALN-TTR02 and to measure clinical activity based on serial measurement of circulating serum TTR levels. For more information about this study see “About ALN-TTR Program” below.

Conference Call Information

Alnylam will host a conference call on Monday, July 16 at 8:30 a.m. ET to discuss the clinical results from its ALN-TTR02 Phase I clinical trial. To access the call, please dial 800-706-7745 (domestic) or 617-614-3472 (international) five minutes prior to the start time and provide the passcode 34291970. A replay of the call will be available beginning at 10:30 a.m. ET on July 16. To access the replay, please dial 888-286-8010 (domestic) or 617-801-6888 (international), and provide the passcode 87724320.

A live audio webcast of the call will also be available on the News & Investors page of the company’s website, www.alnylam.com. An archived webcast will be available on the Alnylam website approximately two hours after the event.

About Transthyretin-Mediated Amyloidosis

Transthyretin (TTR)-mediated amyloidosis (ATTR) is a hereditary, systemic disease caused by mutations in the TTR gene. TTR protein is produced primarily in the liver and is normally a carrier for thyroid hormones and retinol binding proteins. Mutations in TTR cause abnormal amyloid proteins to accumulate and damage body organs and tissue such as the peripheral nerves and heart, resulting in intractable peripheral sensory neuropathy, autonomic neuropathy, and/or cardiomyopathy. In its severest form, ATTR represents a major unmet medical need with significant morbidity and mortality as an orphan disease; FAP (familial amyloidotic polyneuropathy) affects approximately 10,000 people worldwide and FAC (familial amyloidotic cardiomyopathy) affects at least 40,000 people worldwide. ATTR patients with FAP have a mean life expectancy of five to 15 years from symptom onset and the only treatment options for early stage disease are liver transplantation and tafamidis (approved in Europe); as a result there is a significant need for novel therapeutics to treat patients who have inherited mutations in the TTR gene.

About ALN-TTR Program

ALN-TTR02 is a systemically delivered RNAi therapeutic targeting the transthyretin (TTR) gene for the treatment of TTR-mediated amyloidosis (ATTR). Alnylam is currently conducting a Phase II trial with ALN-TTR02 in Europe, and is in the process of adding more sites in other geographies. The study is aimed at evaluating safety, tolerability, and potential clinical activity of multiple once-monthly doses of ALN-TTR02 in ATTR patients. The potential clinical activity of ALN-TTR02 will be evaluated based on measurement of serum levels of TTR, the disease-causing protein in patients with ATTR. For more information about this study and the recruiting sites, visit www.clinicaltrial.gov.

ALN-TTR02 is formulated in a proprietary second-generation lipid nanoparticle technology, using the “MC3” lipid. Assuming positive results from the Phase II study, Alnylam expects to start a pivotal trial for ALN-TTR02 in 2013. Alnylam also plans to advance ALN-TTRsc, which utilizes a GalNAc-conjugate delivery approach and subcutaneous dose administration. Alnylam’s goal is to advance ALN-TTRsc to an investigational new drug (IND) filing in the second half of 2012 with data in the first half of 2013.

About RNA Interference (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 RNAs (siRNAs), 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 for the treatment of genetically defined diseases, including ALN-TTR for the treatment of transthyretin-mediated amyloidosis (ATTR), ALN-AT3 for the treatment of hemophilia, ALN-PCS for the treatment of severe hypercholesterolemia, ALN-HPN for the treatment of refractory anemia, and ALN-TMP for the treatment of hemoglobinopathies. As part of its “Alnylam 5x15^TM” strategy, the company expects to have five RNAi therapeutic products for genetically defined diseases in clinical development, including programs in advanced stages, on its own or with a partner by the end of 2015. Alnylam has additional partnered programs in clinical or development stages, including ALN-RSV01 for the treatment of respiratory syncytial virus (RSV) infection, ALN-VSP for the treatment of liver cancers, and ALN-HTT for the treatment of Huntington’s disease. The company’s leadership position on RNAi therapeutics and intellectual property have enabled it to form major alliances with leading companies including Merck, Medtronic, Novartis, Biogen Idec, Roche, Takeda, Kyowa Hakko Kirin, Cubist, and Ascletis. In addition, Alnylam and Isis co-founded Regulus Therapeutics Inc., a company focused on discovery, development, and commercialization of microRNA therapeutics; Regulus has formed partnerships with GlaxoSmithKline and Sanofi. Alnylam has also formed Alnylam Biotherapeutics, a division of the company focused on the development of RNAi technologies for applications in biologics manufacturing, including recombinant proteins and monoclonal antibodies. Alnylam’s VaxiRNA™ platform applies RNAi technology to improve the manufacturing processes for vaccines; GlaxoSmithKline is a collaborator in this effort. Alnylam scientists and collaborators have published their research on RNAi therapeutics in over 100 peer-reviewed papers, including many in the world’s top scientific journals such as Nature, Nature Medicine, Nature Biotechnology, and Cell. Founded in 2002, Alnylam maintains headquarters in Cambridge, Massachusetts. For more information, please visit www.alnylam.com.

About “Alnylam 5x15™”

The “Alnylam 5x15” strategy, launched in January 2011, establishes a path for development and commercialization of novel RNAi therapeutics to address genetically defined diseases with high unmet medical need. Products arising from this initiative share several key characteristics including: a genetically defined target and disease; the potential to have a major impact in a high unmet need population; the ability to leverage the existing Alnylam RNAi delivery platform; the opportunity to monitor an early biomarker in Phase I 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. By the end of 2015, the company expects to have five such RNAi therapeutic programs in clinical development, including programs in advanced stages, on its own or with a partner. The “Alnylam 5x15” programs include ALN-TTR for the treatment of transthyretin-mediated amyloidosis (ATTR), ALN-AT3 for the treatment of hemophilia, ALN-PCS for the treatment of severe hypercholesterolemia, ALN-HPN for the treatment of refractory anemia, and ALN-TMP for the treatment of hemoglobinopathies. Alnylam intends to focus on developing and commercializing certain programs from this product strategy itself in the United States and potentially certain other countries; the company will seek development and commercial alliances for other core programs both in the United States and in other global territories.

Alnylam Forward-Looking Statements

Various statements in this release concerning Alnylam’s future expectations, plans and prospects, including without limitation, statements regarding Alnylam’s views with respect to the potential for RNAi therapeutics, including ALN-TTR02 and ALN-TTRsc, its expectations with respect to the timing and success of its clinical trials for ALN-TTR02 and the expected timing and initiation of its Phase I clinical trial for ALN-TTRsc, its expectations regarding the reporting of data from its ALN-TTR02 and ALN-TTRsc clinical trials, and Alnylam’s expectations regarding its “Alnylam 5x15” product strategy, 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 discover and develop novel drug candidates, successfully demonstrate the efficacy and safety of its drug candidates, including ALN-TTR02 and ALN-TTRsc, the pre-clinical and clinical results for these product candidates, which may not support further development of such product candidates, actions of regulatory agencies, which may affect the initiation, timing and progress of clinical trials for such product candidates, obtaining, maintaining and protecting intellectual property, obtaining regulatory approval for products, competition from others using technology similar to Alnylam’s and others developing products for similar uses, and Alnylam’s ability to establish and maintain strategic business alliances and new business initiatives, as well as those risks more fully discussed in the “Risk Factors” section of its most recent quarterly report on Form 10-Q on file with the Securities and Exchange Commission. 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 does not assume any obligation to update any forward-looking statements.