Long-term lipid lowering with evolocumab (Repatha) further reduces cardiovascular events, including CV death, without a safety signal, according to results from the FOURIER open-label extension (OLE) study.
In the parent FOURIER trial, treatment with the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor over a median of 2.2 years reduced the primary efficacy endpoint by 15% but showed no CV mortality signal, compared with placebo, in patients with atherosclerotic disease on background statin therapy.
Now with follow-up out to 8.4 years – the longest to date in any PCSK9 study – cardiovascular mortality was cut by 23% in patients who remained on evolocumab, compared with those originally assigned to placebo (3.32% vs. 4.45%; hazard ratio, 0.77; 95% confidence interval, 0.60-0.99).
The Kaplan-Meier curves during FOURIER were “essentially superimposed and it was not until the open-label extension period had begun with longer-term follow up that the benefit in terms of cardiovascular mortality reduction became apparent,” said principal investigator Michelle O’Donoghue, MD, MPH, of Brigham and Women’s Hospital, Boston.
The results were reported at the annual congress of the European Society of Cardiology and published simultaneously in Circulation.
Pivotal statin trials have median follow-up times of 4-5 years and demonstrated both a lag effect, meaning clinical benefit grew over time, and a legacy effect, where clinical benefit persisted in extended follow-up after the parent study, Dr. O’Donoghue observed.
With shorter follow-up in the parent FOURIER trial, there was evidence of a lag effect with the risk reduction in CV death, MI, and stroke increasing from 16% in the first year to 25% over time with evolocumab.
FOURIER-OLE enrolled 6,635 patients (3355 randomly assigned to evolocumab and 3280 to placebo), who completed the parent study and self-injected evolocumab subcutaneously with the choice of 140 mg every 2 weeks or 420 mg monthly. Study visits were at week 12 and then every 24 weeks. Median follow-up was 5 years.
Their mean age was 62 years, three-fourths were men, a third had diabetes. Three-fourths were on a high-intensity statin at the time of enrollment in FOURIER, and median LDL cholesterol at randomization was 91 mg/dL (2.4 mmol/L).
At week 12, the median LDL cholesterol was 30 mg/dL (0.78 mmol/L), and this was sustained throughout follow-up, Dr. O’Donoghue reported. Most patients achieved very low LDL cholesterol levels, with 63.2% achieving levels less than 40 mg/dL (1.04 mmol/L) and 26.6% less than 20 mg/dL (0.52 mmol/L).
Patients randomly assigned in the parent trial to evolocumab versus placebo had a 15% lower risk of the primary outcome of CV death, MI, stroke, hospitalization for unstable angina, or coronary revascularization (15.4% vs. 17.5%; HR, 0.85; 95% CI, 0.75-0.96).
Their risk of CV death, MI, or stroke was 20% lower (9.7% vs. 11.9%; HR, 0.80; 95% CI, 0.68-0.93), and, as noted previously, 23% lower for CV death.
When major adverse cardiovascular events data were parsed out by year, the largest LDL cholesterol reduction was in years 1 and 2 of the parent study (delta, 62 mg/dL between treatment arms), “highlighting that lag of benefit that continued to accrue with time,” Dr. O’Donoghue said.
“There was then carryover into the extension period, such that there was legacy effect from the LDL [cholesterol] delta that was seen during the parent study,” she said. “This benefit was most apparent early on during open-label extension and then, as one might expect when all patients were being treated with the same therapy, it began to attenuate somewhat with time.”
Although early studies raised concerns that very low LDL cholesterol may be associated with an increased risk of hemorrhagic stroke and neurocognitive effects, the frequency of adverse events did not increase over time with evolocumab exposure.
Annualized incidence rates for patients initially randomized to evolocumab did not exceed those for placebo-treated patients for any of the following events of interest: serious safety events (10% vs. 13%), hemorrhagic stroke (0.04% vs. 0.05%), new-onset diabetes (1.2% vs. 2.3%), muscle-related events (1.2% vs. 1.9%), injection-site reactions (0.4% vs. 0.7%), and drug-related allergic reactions (0.6% vs. 1.1%).
“Long-term use of evolocumab with a median follow-up of more than 7 years appears both safe and well tolerated,” Dr. O’Donoghue said.
Taken together with the continued accrual of cardiovascular benefit, including CV mortality, “these findings argue for early initiation of a marked and sustained LDL cholesterol reduction to maximize benefit,” she concluded.