On Tuesday, Silence Therapeutics presented what seemed like positive data on zerlasiran, its experimental drug for reducing cardiovascular risk, at the annual meeting of the American Heart Association. Then, its stock fell 36%.
Investors had several worries. Zerlasiran is an RNA-silencing drug that reduced levels of Lp(a), a cholesterol-related compound thought to increase the risk of heart attacks and strokes, by 80%, according to the study data presented. It is given by injection.
But at the same AHA meeting, Eli Lilly presented positive study results on its own Lp(a)-lowering drug. That drug, called muvalapin, is given orally — a potential advantage.
Two patients in the zerlasiran also had elevated liver enzyme levels, although levels of bilirubin, another blood test result used in measuring liver safety, were not elevated. A risk of liver toxicity weighing on zerlasiran might make it more challenging for Silence to find a Big Pharma partner willing to help pay for the expensive development of the drug.
Analysts at BMO Capital Markets defended Silence, writing, “We believe the stock reaction is overdone and see no safety or competitive threat concerns.” On Wednesday, at least, investors disagreed.
