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Importance: Lipoprotein(a) (Lp[a]) is an important risk factor for atherothrombotic cardiovascular disease and aortic stenosis, for which there are no treatments approved by regulatory authorities., Objectives: To assess adverse events and tolerability of a short interfering RNA (siRNA) designed to reduce hepatic production of apolipoprotein(a) and to assess associated changes in plasma concentrations of Lp(a) at different doses., Design, Setting, and Participants: A single ascending dose study of SLN360, an siRNA targeting apolipoprotein(a) synthesis conducted at 5 clinical research unit sites located in the US, United Kingdom, and Australia. The study enrolled adults with Lp(a) plasma concentrations of 150 nmol/L or greater at screening and no known clinically overt cardiovascular disease. Participants were enrolled between November 18, 2020, and July 21, 2021, with last follow-up on December 29, 2021., Interventions: Participants were randomized to receive placebo (n = 8) or single doses of SLN360 at 30 mg (n = 6), 100 mg (n = 6), 300 mg (n = 6), or 600 mg (n = 6), administered subcutaneously., Main Outcomes and Measures: The primary outcome was evaluation of safety and tolerability. Secondary outcomes included change in plasma concentrations of Lp(a) to a maximum follow-up of 150 days., Results: Among 32 participants who were randomized and received the study intervention (mean age, 50 [SD, 13.5] years; 17 women [53%]), 32 (100%) completed the trial. One participant experienced 2 serious adverse event episodes: admission to the hospital for headache following SARS-CoV-2 vaccination and later for complications of cholecystitis, both of which were judged to be unrelated to study drug. Median baseline Lp(a) concentrations were as follows: placebo, 238 (IQR, 203-308) nmol/L; 30-mg SLN360, 171 (IQR, 142-219) nmol/L; 100-mg SLN360, 217 (IQR, 202-274) nmol/L; 300-mg SLN360, 285 (IQR, 195-338) nmol/L; and 600-mg SLN360, 231 (IQR, 179-276) nmol/L. Maximal median changes in Lp(a) were -20 (IQR, -61 to 3) nmol/L, -89 (IQR, -119 to -61) nmol/L, -185 (IQR, -226 to -163) nmol/L, -268 (IQR, -292 to -189) nmol/L, and -227 (IQR, -270 to -174) nmol/L, with maximal median percentage changes of -10% (IQR, -16% to 1%), -46% (IQR, -64% to -40%), -86% (IQR, -92% to -82%), -96% (IQR, -98% to -89%), and -98% (IQR, -98% to -97%), for the placebo group and the 30-mg, 100-mg, 300-mg, and 600-mg SLN360 groups, respectively. The duration of Lp(a) lowering was dose dependent, persisting for at least 150 days after administration., Conclusions and Relevance: In this phase 1 study of 32 participants with elevated Lp(a) levels and no known cardiovascular disease, the siRNA SLN360 was well tolerated, and a dose-dependent lowering of plasma Lp(a) concentrations was observed. The findings support further study to determine the safety and efficacy of this siRNA., Trial Registration: ClinicalTrials.gov Identifier: NCT04606602; EudraCT Identifier: 2020-002471-35.

The American Medical Association House of Delegates adopted a set of diagnostic and therapeutic recommendations concerning the management of disorders of cholesterol, triglyceride, and lipoprotein metabolism at its annual meeting in 1994. In recognition of the advances made during the past decade in the prevention and management of coronary heart disease, these recommendations updated those made previously. In addition, recommendations concerning the management of clinical risk factors for coronary heart disease were expanded to include infants, children, and adolescents.

Recent clinical trials indicate that reduction of plasma cholesterol concentrations in individuals with increased levels of low-density lipoproteins reduces their risk of myocardial infarction and death. Therefore, the question of "whether to treat" should be shifted to "whom to treat" and "how best to treat". The understanding of normal lipid transport via the plasma lipoproteins has grown to a sophisticated level over the past 20 years. Plasma cholesterol, required for cellular membrane integrity, and plasma triglycerides, the primary mammalian energy source, are carried in lipoprotein particles that vary in size, density, lipid composition, and apolipoprotein content. Some lipoprotein particles (low-density lipoproteins) play a causal role in the atherosclerotic process, while other particles (high-density lipoproteins) appear to prevent this process. Utilizing this understanding of the plasma lipoproteins, a systematic approach to the management of the patient with hyperlipoproteinemia has been developed which may lead to the normalization of plasma lipoprotein concentrations in the majority of hyperlipoproteinemic patients.