Findings from a new show that an experimental ‘gene silencing’ therapy reduced blood levels of lipoprotein(a) by up 98%. This is significant as lipoprotein(a) is a key cardiovascular risk driver which is determined largely by genetics and not modifiable lifestyle factors, and which cannot be lowered by current medical means.
Findings from the Cleveland Clinic-led phase 1 trial were published in the Journal of the American Medical Association.
Trial participants receiving higher doses of SLN360 – a small interfering RNA (siRNA) therapeutic that ‘silences’ the gene responsible for lipoprotein(a) production – saw their lipoprotein(a) levels drop by as much as 96%-98%. Five months later, these participants’ lipoprotein(a) – also known as Lp(a) – levels remained 71%-81% lower than baseline.
The findings suggest this siRNA therapy could be a promising treatment to help prevent premature heart disease in people with high levels of Lp(a), which is estimated to affect 64 million people in the United States and 1.4 billion people worldwide.
“These results showed the safety and strong efficacy of this experimental treatment at reducing levels of Lp(a), a common, but previously untreatable, genetically-determined risk factor that leads to premature heart attack, stroke and aortic stenosis,” said the study’s lead author Steven E. Nissen, MD “We hope that further development of this therapy also will be shown to reduce the consequences of Lp(a) in the clinical setting through future studies.”
Lp(a) has similarities to LDL. Lp(a) is made in the liver, where an extra protein called apolipoprotein(a) is attached to an LDL-like particle. Unlike other types of cholesterol particles, Lp(a) levels are 80 to 90% genetically determined. The structure of the Lp(a) particle causes the accumulation of plaques in arteries, which play a significant role in heart disease. Elevated Lp(a) greatly increases the risk of heart attacks and strokes.
Although cardiovascular risk-reduction therapies that lower LDL cholesterol and other lipids exist, there are treatments to lower Lp(a). Since Lp(a) levels are genetically determined, lifestyle changes such as diet or exercise have no effect. In the current study, the siRNA therapy reduces Lp(a) levels by “silencing” the gene responsible for Lp(a) production and blocking creation of apolipoprotein(a) in the liver.
In the APOLLO trial, researchers enrolled 32 participants with Lp(a) levels above 15 nmol/L, with a median level of 224nmol/L (75nmol/L or less is considered normal). Eight participants received a placebo and the remaining received one of four doses of SLN360 via a single subcutaneous injection. The doses were 30mg, 100mg, 300mg and 600mg. Participants were closely observed for the first 24 hours after their injection and then followed up for five months.
Compared to baseline, participants receiving 300mg and 600mg of SLN360 experienced a maximum of 96% and 98% reduction in Lp(a) levels, and a reduction of 71% and 81% at five months. Those receiving a placebo saw no change in Lp(a) levels. The highest doses also reduced LDL cholesterol by about 20%-25%. There were no major safety consequences reported and the most common side effect was temporary soreness at the injection site. The study was extended and researchers will continue to follow participants for a total of one year.
Source: Cleveland Clinic