In a closely watched trial, a drug did exactly what it was designed to do to a blood marker — and it still didn’t help patients’ hearts. Novartis and Ionis’s pelacarsen sharply lowered lipoprotein(a), or Lp(a), but failed to reduce cardiovascular events.
Lp(a) is a largely genetic risk factor for heart disease that affects roughly one in five people worldwide, and unlike LDL cholesterol, there’s no approved drug to lower it. Pelacarsen — an antisense drug — had shown it could drastically cut Lp(a). But in the Phase 3 HORIZON trial, that reduction did not translate into fewer cardiovascular deaths, heart attacks or strokes versus placebo.
Why the result stings
The trial was a major test of the “Lp(a) hypothesis” — the widely held idea that lowering Lp(a) should reduce cardiovascular events, much as lowering LDL does. Pelacarsen’s failure to show benefit despite hitting its biomarker target raises hard questions: was the reduction not deep enough, the patients or follow-up not right, or is Lp(a) less directly causal than believed? Other Lp(a)-lowering drugs (from Amgen, Lilly and others) are still in late-stage testing, and their results are now even more pivotal for the field.
Why it matters
Millions have high Lp(a) with no treatment option, and a positive result would have been a landmark. This setback doesn’t necessarily doom the entire approach, but it’s a sobering reminder that moving a risk marker isn’t the same as helping patients — the reason large outcome trials matter.