Silence Therapeutics is mum no more on its short interfering RNA therapy, which has been found to significantly reduce levels of an independent risk factor for cardiovascular disease.
The London biotech said its siRNA, dubbed SLN360, reduced lipoprotein(a), or Lp(a), in healthy adults who had elevated levels of the substance that carries cholesterol through the bloodstream. The therapy reduced Lp(a) between 46% to 98% depending on which of the four doses patients received during the phase 1 study. Lp(a) consists of an LDL-like particle that is wrapped inside another protein named apolipoprotein, hence the 'a'. LDL is colloquially known as bad cholesterol.
About 20% of people experience high levels of Lp(a), which is seen as a genetic risk factor for cardiovascular disease, Silence said. There are no approved treatments to lower Lp(a).
SLN360 led to "no clinically important safety concerns," Silence said Wednesday. Low grade adverse events were seen at the injection site, most notably at the highest dose of 600mg.
The study's 32 adults, who had no known cardiovascular disease, either received a single dose delivered under the skin or placebo and were observed for up to 150 days. At that time, some patients had an 81% reduction in Lp(a). Silence will extend the follow-up period to a full 12 months to analyze duration, with that data slated for the third quarter, the biotech said.
Silence plans to start a phase 2 study of SLN360 in patients with atherosclerotic cardiovascular disease, or ASCVD, in the second half of this year. The biotech is also working to ink global partnerships to "scale up" development of the drug, said Mark Rothera, CEO and president, in a statement.
The small biotech, which has been through multiple challenges over its 20-plus-year existence, will have to face stiff competition from Big Pharma if the drug makes it to the market. The FDA approved Novartis' siRNA therapy Leqvio in late-December 2021 as an adjunct treatment to diet and statins to help patients lower their bad cholesterol. The drug, also approved in the EU, is intended for people with ASCVD or heterozygous familial hypercholesterolemia.
The Swiss pharma also has pelacarsen (TQJ230) in a phase 3 trial looking at lowering Lp(a) and reducing cardiovascular risk. It will likely be a while before Novartis drops data on the drug, though. The study is slated to collect final primary outcome data in May 2025.
RELATED: Chinese biopharma powerhouse continues charge into siRNA with Silence R&D pact
Silence has inked some big deals in recent years for work on its RNA interference drugs. Hansoh Pharmaceutical dished out $16 million upfront and up to $1.3 billion in biobucks in October 2021. AstraZeneca, which initially teamed up with Silence 15 years ago, paid $60 million in cash for five targets in March 2020 in a deal that could balloon to $2 billion in milestones. That all comes on top of a more than $2 billion biobucks deal with Mallinckrodt in 2019.