Alnylam Presents Pre-Clinical Data on RNAi Therapeutics at ISA

– TTR Knockdown Shown to be Highly Correlated with Regression of TTR Deposits in Mouse Disease Model – – Comparative Studies Exhibit Superior Activity of RNAi Over Stabilizers Toward Regression of TTR Deposits in Mouse Disease Model – – Comparative Studies Establish Greater TTR Knockdown with Over 100-Fold Lower Tissue Exposure for RNAi Therapeutics versus Antisense Oligonucleotides (ASO) – Alnylam Pharmaceuticals, Inc.

, a leading RNAi therapeutics company, announced today the presentation of new pre-clinical data on RNAi therapeutics targeting transthyretin (TTR) for the treatment of TTR-mediated amyloidosis (ATTR). These data were presented at the International Symposium on Amyloidosis (ISA) held April 27 – May 1, 2014 in Indianapolis, Indiana. In a poster titled “Preclinical Evaluation of RNAi Therapeutics for the Treatment of ATTR: An Update,” Alnylam scientists presented data confirming that the degree of TTR knockdown in a mouse disease model was highly correlated with regression of TTR tissue deposits. Further, comparative studies were performed with the TTR stabilizer tafamidis and a TTR-specific antisense oligonucleotide (ASO). In these pre-clinical studies, RNAi therapeutics targeting TTR were shown to have superior pharmacologic profiles. “We believe that these new pre-clinical data highlight the potential for RNAi therapeutics targeting TTR to emerge as the optimal approach for the treatment of ATTR. First, in a mouse model of ATTR, we've demonstrated that the degree of TTR suppression at steady state knockdown is highly correlated with regression of TTR deposits in multiple tissues. These data suggest that the 80% TTR knockdown target level achieved with patisiran and ALN-TTRsc could facilitate a reduced pathogenic accumulation of TTR amyloid and possibly even a regression of TTR amyloid in patients with ATTR,” said Rachel Meyers, Ph.D., Vice President, Research and RNAi Lead Development at Alnylam. “Moreover, our scientists and collaborators presented comparative studies of RNAi therapeutics with a TTR stabilizer and an antisense oligonucleotide (ASO). In a mouse model of ATTR, treatment with the TTR stabilizer tafamidis resulted in a trend for regression of TTR deposits in a limited number of tissues, while administration of an RNAi therapeutic led to a statistically significant regression in all tissues evaluated. Additional comparative studies were performed with a TTR-specific ASO and showed that RNAi therapeutics achieve a more rapid, potent, and robust knockdown of TTR than the ASO, with an over 100-fold lower drug exposure in liver and ‘bystander' tissues such as kidney. We believe that the ability of RNAi therapeutics to achieve potent TTR knockdown with lower tissue exposure could result in a more favorable efficacy and tolerability profile.” New data presented at ISA are based on studies performed in transgenic mice expressing the amyloidogenic mutant human V30M TTR. These mice exhibit deposition of TTR at greater than 12 months of age in similar target organs to those seen in ATTR human disease, including dorsal root ganglion (DRG), sciatic nerve, duodenum, esophagus, stomach, and colon. Animals at greater than 14 months of age, where there is established tissue deposition of TTR, were treated with increasing doses of siTTRsc, a GalNAc-siRNA conjugate specific for TTR. Results showed that the degree of TTR reduction at steady state knockdown was highly correlated in a linear relationship with regression of TTR deposits (p<0.01 in each tissue). Specifically, regression of TTR deposits was greater with every additional level of plasma TTR knockdown, and was most pronounced at the highest dose of siTTRsc tested, which achieved over 95% TTR knockdown. Also, even at a dose that resulted in only about 50% TTR knockdown, TTR tissue deposits were shown to be significantly reduced compared with PBS-treated control animals. These results confirm that TTR knockdown of greater than 50% can lead to regression of TTR tissue deposits, but that the highest levels of TTR knockdown achievable remains the therapeutic objective for RNAi therapeutics. Additional pre-clinical studies were performed to compare the pharmacologic properties of RNAi therapeutics with those of the TTR stabilizer tafamidis and an ASO targeting TTR. First, studies in the V30M transgenic mouse were performed comparing LNP-siTTR, a lipid nanoparticle-formulated TTR-specific siRNA, with tafamidis. LNP-siTTR was administered at a dose that achieved a robust knockdown of serum TTR by greater than 95%, while tafamidis was administered at a dose that provided a greater than 100% increase in TTR tetramer stabilization, similar to that achieved at clinical doses. Results with LNP-siTTR showed that TTR deposition in all affected tissues (esophagus, stomach, duodenum, colon, DRG, and sciatic nerve) was reduced by mean levels greater than 75% and maximum levels of greater than 95% as compared to controls (p<0.0001 by ANOVA). In contrast, tafamidis administration resulted in only modest TTR deposit regression in only the DRG and sciatic nerve (mean levels of 35% and 64%, respectively), with only the latter achieving statistical significance relative to control. Finally, a study was performed comparing ALN-TTRsc with a TTR-specific ASO; both RNA therapeutics were administered with identical subcutaneous dosing regimens. ALN-TTRsc achieved greater than 90% knockdown of TTR by day 3 at a dose of 10 mg/kg and by day 10 at a dose of 2.5 mg/kg, with resulting liver and kidney concentrations of 1 and 0.6 µg/g, respectively, 24 hours after the final dose. In contrast, 10 mg/kg doses of the ASO achieved nadir of only about 70% knockdown by day 24, with no knockdown effect observed at 2.5 mg/kg. At the 10 mg/kg ASO dose, the corresponding liver and kidney concentrations were 151 and 420 µg/g, respectively. These results demonstrate that ALN-TTRsc achieves more rapid and greater TTR knockdown at 100-fold lower target tissue exposure as compared with an ASO. Taken together, these comparative pharmacologic results demonstrate a favorable profile for RNAi therapeutics as compared with a TTR stabilizer and an ASO. Alnylam is currently advancing patisiran (ALN-TTR02), an intravenously delivered RNAi therapeutic targeting TTR for the treatment of ATTR in patients with familial amyloidotic polyneuropathy (FAP), in the Phase 3 APOLLO trial in patients with FAP. In addition, the company is advancing ALN-TTRsc, a subcutaneously delivered RNAi therapeutic targeting TTR for the treatment of ATTR in patients with TTR cardiac amyloidosis, in a Phase 2 trial in patients with familial amyloidotic cardiomyopathy (FAC) and senile systemic amyloidosis (SSA). The company is also evaluating additional cohorts in the Phase 1 study of ALN-TTRsc to confirm a fixed dose regimen for further development. The company plans to initiate a Phase 3 trial for ALN-TTRsc in patients with TTR cardiac amyloidosis by the end of 2014.