Alirocumab slashed cholesterol but not plaque in transplanted hearts

Adding the cholesterol-lowering drug alirocumab to a statin early after a heart transplant drove LDL cholesterol far below what the statin alone achieved — and made no measurable difference to the growth of plaque in the transplanted heart's arteries over the first year [s1]. It is a clean null on the outcome that matters, from a trial the drug's maker did not run.

Cardiac allograft vasculopathy — a diffuse, accelerated narrowing of the coronary arteries in a transplanted heart — is an important cause of death after heart transplantation, and abnormal cholesterol is a major contributor to its development [s1]. Statins are standard, but whether adding a PCSK9 inhibitor to lower cholesterol further could actually hold back the disease was not established [s1]. CAVIAR tested exactly that.

What the trial did

CAVIAR was an investigator-initiated, prospective, multicentre, double-blind randomised trial — the label matters, because it means the study was designed and run independently of the company that sells the drug [s1]. Participants were randomised soon after heart transplantation to receive either alirocumab or placebo on top of rosuvastatin [s1]. Before randomisation and again at one year, every participant underwent an invasive coronary work-up: angiography, fractional flow reserve, coronary flow reserve, the index of microcirculatory resistance, and intravascular ultrasound with near-infrared spectroscopy [s1]. The prespecified primary endpoint was the change in coronary artery plaque volume from baseline to one year, measured by serial intravascular ultrasound, and lipid values were assessed at baseline and at prespecified intervals [s1]. That imaging-based design is demanding — it commits every participant to two invasive coronary procedures a year apart — but it is also what lets the trial say something concrete about the disease process rather than about a blood test alone [s1]. In all, 114 transplant recipients took part, 57 assigned to alirocumab and 57 to placebo, with baseline characteristics well matched [s1]. The trial was registered before enrolment [s2].

What it found

The drug did what a PCSK9 inhibitor is supposed to do. LDL cholesterol fell sharply in the alirocumab arm, from 72.7±31.7 to 31.5±20.7 mg/dL (P<0.001), while it did not budge on placebo, going from 69.0±22.4 to 69.2±28.1 mg/dL (P=0.92) [s1].

That biochemical success did not translate into slower disease. Plaque volume increased numerically in both groups over 12 months — from 176.3±95.2 to 184.5±105.4 mm³ with alirocumab (P=0.23) and from 173.7±96.7 to 183.1±109.8 mm³ with placebo (P=0.15) — and the change in plaque volume did not differ between the arms, with a mean difference in differences of 1.01 (0.89–1.14) and a P value of 0.86 [s1]. The physiological measures of coronary function — fractional flow reserve, coronary flow reserve, and the index of microcirculatory resistance — also did not change significantly with the addition of alirocumab [s1]. On safety, there were no significant adverse events related to the drug [s1].

How to read it

This is a textbook example of why a surrogate is not an outcome. Alirocumab moved the number everyone watches — LDL cholesterol — dramatically, and moved the thing that number is supposed to stand in for — plaque burden and coronary function — not at all, at least within a year in patients whose LDL was already fairly low to begin with [s1]. The authors' own conclusion is blunt: PCSK9 inhibition safely lowered LDL cholesterol but did not reduce coronary artery plaque progression at one year compared with statin therapy alone [s1].

Several caveats keep this from being the last word. The trial was small, at 114 patients, and followed people for only one year — a short window in which to detect changes in a disease that unfolds over years [s1]. A null in this setting is not proof the drug is useless in transplant recipients; it is evidence that, over one year and at these cholesterol levels, adding it on top of a statin did not visibly bend the disease [s1].

Related coverage has examined an oral PCSK9 inhibitor tested head-to-head against injectables, the first oral PCSK9 pill to reach the market, and what large reviews say about statin side-effects.

What to watch

The useful next questions are whether a larger trial, a longer follow-up, or patients starting with higher cholesterol would show something CAVIAR could not, and whether any imaging change would ever map onto the outcome that counts — survival free of allograft vasculopathy [s1]. For now, the finding is a caution against assuming that harder cholesterol-lowering automatically buys protection in a transplanted heart.

This article describes trial results and is not medical advice. Post-transplant medication decisions are for treating clinicians.

Sources

• Cardiac Allograft Vasculopathy Inhibition With Alirocumab: The CAVIAR Trial — Circulation, 10 November 2025
• CAVIAR trial registration (NCT03537742) — ClinicalTrials.gov, first posted 25 May 2018