LONDON– Silence Therapeutics plc, Nasdaq: SLN (“Silence” or “the Company”), a leader in the discovery, development and delivery of novel short interfering ribonucleic acid (“siRNA”) therapeutics for the treatment of diseases with significant unmet medical need, today announced positive topline results in its phase 1 single-ascending dose study of SLN360, an siRNA targeting lipoprotein(a) (“Lp(a)”), in healthy adults with high Lp(a).
High Lp(a), defined as ≥ 50 mg/dL (c.125nmol/L), affects approximately 20% of the world’s population and is a genetic risk factor for cardiovascular disease. There are no approved medicines that selectively lower Lp(a). SLN360 is a siRNA that is designed to lower Lp(a) production by targeting messenger RNA transcribed from the LPA gene.
“These first-in-human data for SLN360, which align with our pre-clinical findings, reinforce our confidence in its potential to substantially lower Lp(a) levels with long-lasting action and address a major unmet need in cardiovascular disease,” said Giles Campion, M.D., EVP, Head of R&D and Chief Medical Officer at Silence. “More broadly, siRNA is proving to be a powerful modality for treating genetic conditions, both common and rare, by precisely engaging targets that have previously been considered ‘undruggable’.”
This phase 1 study evaluated the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics of SLN360 at escalating doses in 32 adults with plasma concentrations at screening of Lp(a) ≥150 nmol/L (approximately ≥ 60 mg/dL) with no known cardiovascular disease. Individuals were randomly assigned to receive a single subcutaneous dose of SLN360 (30 mg, 100 mg, ≤ 300 mg or ≤ 600 mg) or placebo and were observed for up to 150 days.
The primary safety objective was assessment of treatment-emergent adverse events. No clinically important safety concerns were identified. Low grade adverse events at the injection site were observed, most prominently at the highest dose. As expected, systemic exposures (PK) of SLN360 increased in a broadly dose-proportional manner.
The key efficacy assessment was percent change from baseline in Lp(a). SLN360 reduced Lp(a) in a dose dependent manner from 46% up to a maximum of 98% with up to an 81% reduction persisting at 150 days. The study follow-up period has been extended from 150 days to 365 days to further assess the duration of action. Silence anticipates data from the extended follow-up period in the third quarter of 2022.
“These very encouraging results for our wholly owned SLN360 program mark the second positive study from our proprietary mRNAi GOLD™ platform, further underscoring its potential to safely and substantially reduce levels of disease-related proteins in liver cells,” said Mark Rothera, President and Chief Executive Officer at Silence. “There is currently no specific treatment option approved for high Lp(a), a genetically determined cardiovascular risk factor affecting 20% of the world’s population. Today’s announcement brings us one step closer to addressing a major unmet need in cardiovascular disease. We are engaged in global partnership discussions to ensure we are well positioned to scale up SLN360 development and future commercialization.”
Detailed results from the SLN360 phase 1 single-ascending dose study will be presented by principal investigator and Professor of Cardiovascular Medicine at the Cleveland Clinic, Steven E. Nissen, MD, at the American College of Cardiology (ACC) Annual Scientific Session & Expo on April 3, 2022.
Patient enrollment continues in the multiple-ascending dose portion of the SLN360 phase 1 study in patients with high Lp(a) that have a confirmed history of stable atherosclerotic cardiovascular disease (“ASCVD”). Silence remains on-track to initiate the SLN360 phase 2 ASCVD study in the second half of 2022, pending regulatory discussions.
