Pelacarsen misses cardiovascular endpoint despite lowering Lp(a), Novartis reports

Novartis reported on September 4 that its experimental medicine pelacarsen missed the primary cardiovascular endpoint in the phase 3 Lp(a)HORIZON trial, despite lowering participants’ lipoprotein(a), or Lp(a). The finding is a consequential setback for an approach intended to reduce cardiovascular risk that persists despite established preventive treatment.

The announcement concerns clinical events, including heart attacks and strokes, rather than simply a laboratory measurement. For healthspan research, that distinction matters: changing a biological risk marker must ultimately translate into fewer illnesses or deaths to establish clinical benefit.

What the trial tested

The peer-reviewed design paper describes a multinational, randomized, double-blind, placebo-controlled study involving 8,323 people with established cardiovascular disease and Lp(a) concentrations of at least 70 mg/dL. Pelacarsen is an antisense oligonucleotide, a medicine designed to reduce production of its molecular target.

The primary outcome combined cardiovascular death, nonfatal heart attack, nonfatal stroke and urgent coronary revascularization requiring hospitalization. Participants were receiving other cardiovascular treatments, so the study tested whether pelacarsen could add protection beyond that background care.

The trial framework also included evaluation in participants with Lp(a) of at least 90 mg/dL. The public announcement does not provide numerical results for that population, making it premature to draw conclusions about whether higher starting levels affected the treatment response.

This was a study of people who already had cardiovascular disease. Its findings cannot directly answer whether starting an Lp(a)-lowering intervention earlier in life, before established disease, would change long-term outcomes.

Earlier evidence measured a different outcome

The rationale for testing pelacarsen included an earlier randomized trial published online in the New England Journal of Medicine on January 1, 2020. That study enrolled 286 patients with cardiovascular disease and elevated Lp(a), comparing several treatment regimens with placebo.

Its primary endpoint was the percentage change in Lp(a) after approximately six months. Mean reductions across active-treatment groups ranged from 35% to 80%, compared with 6% for placebo. Those findings established substantial activity against the blood marker; they did not establish prevention of heart attacks or strokes.

Lp(a) levels are genetically influenced, and elevated concentrations are associated with cardiovascular disease. Nevertheless, evidence identifying a risk factor and evidence showing that a particular treatment improves outcomes answer different questions. HORIZON was designed to address the latter.

What remains undisclosed

The September 4 disclosures do not supply the cardiovascular event counts, hazard ratios, confidence intervals or detailed component results needed to assess the size and precision of the treatment effect. Missing a primary endpoint does not, by itself, establish that the true effect is exactly zero.

Ionis, which discovered and initially developed pelacarsen, described its safety profile as acceptable in a contemporaneous filing. That remains the company’s characterization: without detailed adverse-event tables, readers cannot independently assess the balance of benefits and harms. The companies said full results would be presented at an upcoming medical congress.

The available information therefore supports a narrow conclusion: the sponsor reports that this trial did not demonstrate cardiovascular protection in the overall population. It does not establish why the endpoint was missed or settle the prospects of every intervention targeting Lp(a).

For prevention and healthy aging, the next useful evidence will be the complete clinical results, including absolute event rates, uncertainty estimates, safety findings and prespecified analyses. Those data will determine how much this result changes the interpretation of Lp(a) lowering as a strategy for preserving cardiovascular health.