Novartis and Ionis's Pelacarsen Fails Phase 3 Lp(a)HORIZON Trial, Shaking the Lipoprotein(a) Hypothesis

Novartis and Ionis's Pelacarsen Fails Phase 3 Lp(a)HORIZON Trial, Shaking the Lipoprotein(a) Hypothesis

On September 4, 2026, Novartis and its partner Ionis Pharmaceuticals announced that their highly anticipated, pioneering cardiovascular outcomes trial, Lp(a)HORIZON, failed to meet its primary endpoint. The study evaluated pelacarsen, an investigational antisense oligonucleotide (ASO) designed to inhibit lipoprotein(a) [Lp(a)] production at its source. Although the drug successfully and substantially lowered Lp(a) levels, this reduction did not translate into a statistically significant decrease in major adverse cardiovascular events (MACE) compared to placebo.

The failure represents a massive clinical setback for Novartis and casts a shadow of doubt over the entire emerging class of Lp(a)-lowering therapies currently in development by competitors like Amgen (olpasiran) and Eli Lilly (lepodisiran).

Trial Design and Background Risk Management

The Lp(a)HORIZON trial (NCT04023552) was a randomized, double-blind, placebo-controlled study that enrolled 8,323 patients across 42 countries. Participants had established cardiovascular disease (CVD) and highly elevated Lp(a) levels (≥70 mg/dL). The primary endpoint was a 4-point composite of major adverse cardiovascular events: cardiovascular death, non-fatal myocardial infarction (MI), non-fatal stroke, and urgent coronary revascularization requiring hospitalization.

Crucially, the trial was conducted on a background of exceptionally well-managed standard preventive therapy:

"Study participants received guideline-directed treatments, including lipid lowering and antihypertensive therapies."

Cardiologists noted that the background risk in the study population was exceptionally well controlled, with a mean LDL-cholesterol (LDL-C) level of approximately 66 mg/dL. This highly optimized background care may have reduced the absolute risk of events so significantly that further lowering of Lp(a) provided no measurable incremental benefit.¹

Scientific and Market Implications

Elevated Lp(a) is an inherited, independent, and causal cardiovascular risk factor affecting roughly one in five people worldwide, with no currently approved targeted therapies. Because Lp(a) levels are approximately 90% genetically determined and unaffected by diet or lifestyle, the cardiovascular community had long viewed Lp(a) as "the holy grail" of lipid-lowering research, with peak sales forecasts for pelacarsen reaching $3 billion to $6 billion.

The trial's failure triggered immediate skepticism regarding the therapeutic value of targeting Lp(a):

"Although pelacarsen substantially lowered Lp(a) levels consistent with previous studies, we are disappointed that this did not translate to cardiovascular risk reduction," said Brett P. Monia, PhD, chief executive officer, Ionis.

Following the announcement, shares of Novartis fell, and competitor Amgen saw its stock drop by 10% as investors re-evaluated the commercial viability of the entire drug class. Shreeram Aradhye, President of Development and Chief Medical Officer for Novartis, acknowledged the disappointment but emphasized the scientific importance of the data:

"These are not the results we hoped for, but they provide important evidence that advances scientific understanding of the relationship between Lp(a) lowering and cardiovascular outcomes and may help inform future approaches to cardiovascular risk management."

The full data from the Lp(a)HORIZON trial is scheduled to be presented at an upcoming medical congress, where researchers will dissect subpopulation data (including patients with baseline Lp(a) ≥90 mg/dL) to determine if specific high-risk cohorts derived any benefit.