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|Objective||To evaluate whether adding niacin (nicotinic acid) to current best lipid-modifying treatment (including simvastatin ± ezetimibe) would reduce the risk of major cardiovascular events in high-risk patients with well-controlled low-density lipoprotein cholesterol (LDL-C) levels|
|Study design||Randomised, double-blind, placebo-controlled, parallel-group, multicentre, international trial.|
Patients aged 50-80 years with previous myocardial infarction (MI), cerebrovascular disease (ischemic stroke or transient ischemic attack), peripheral arterial disease; or diabetes with other coronary heart disease (CHD).
|Primary variable||Major vascular events, a composite of major coronary events (nonfatal myocardial infarction [MI] or coronary heart disease [CHD] death), stroke or revascularisation (coronary and non-coronary)|
Screened patients entered the LDL-C lowering phase and received simvastatin 40 mg/day (±ezetimibe). Patients who achieved a total cholesterol target of 3.5 mmol/L (135 mg/dL) then received active ER niacin plus laropiprant for one month. Patients who were compliant with this regimen were subsequently randomised to treatment with ER niacin/laropiprant (2 g/40 mg) or matching placebo.
Based on previous studies, these lipid differences would be expected to translate to a 10-15% reduction in vascular events.
There was no significant difference in the primary endpoint after 4 years of follow-up. This occurred in 14.5% on ER niacin/laropiprant versus 15.0% of patients on placebo (risk ratio [RR] 0.96, 95% CI 0.90 – 1.03, p=0.29). Most of the benefit was observed in European patients (absolute change in risk: -1.1% versus +0.3% in Chinese patients). Secondary endpoints are summarised in Table 2.
Table 2. Secondary endpoints in HPS2-THRIVE; no. (%) of patients
More patients were withdrawn due to adverse events with ER niacin/laropiprant than placebo (25.4% versus 16.6%, p<0.0001). There were significant excesses in serious adverse events relating to diabetes complications, gastrointestinal and musculoskeletal symptoms, skin, bleeding and infection (Table 3). Notably there was more than 4-fold increase in myopathy with ER niacin/laropiprant compared with statin alone. This was especially problematic in Chinese patients (absolute excess risk of any myopathy 0.53% per year with ER niacin/laropiprant versus 0.03% per year with statin alone).
Table 3. Summary of serious adverse events in HPS2-THRIVE
The Residual Risk Reduction Initiative (R3i) has already highlighted the need to manage the residual risk of cardiovascular events persisting in high-risk patients despite best evidence-based treatment.1 Niacin has been proposed as a possibility for combination with a statin, based on its broad spectrum of lipid-modifying activity, including lowering of elevated triglycerides and raising low plasma levels of high-density lipoprotein cholesterol (HDL-C). Indeed, imaging trials have shown that niacin stabilises or even regresses atherosclerosis in high-risk statin-treated patients.2-4
However, the results of HPS2-THRIVE are consistent with AIM-HIGH in failing to show benefit on clinical outcomes with the combination of niacin plus statin in high-risk patients with well-controlled LDL-C levels (median of 74 mg/dL or 1.91 mmol/L in AIM-HIGH and mean of 63 mg/dL or 1.64 mmol/L in HPS2-THRIVE). Some have argued that AIM-HIGH had methodological issues which may have compromised the study, including the incorporation of a low dose of niacin in the placebo (equating to 200 mg day in patients on 2 g of placebo) to maintain the study blind. This had the effect of raising HDL-C levels in both placebo and niacin-treated groups, thereby reducing the statistical power of the study to detect any potential benefit and/or harm.5 In contrast, HPS2-THRIVE was adequately powered; the average lipid changes over the course of the study (decreases of 10 mg/dL in LDL-C and 33 mg/dL in triglycerides and an increase of 6 mg/dL in HDL-C) were anticipated to translate to a 10-15% reduction in major vascular events.
HPS2-THRIVE population was a well-treated group for LDL-C, HDL-C (> 40 mg/dL or 1.0 mmol/L) and triglycerides (<150 mg/dL or 1.7 mmol/L) at baseline. It is worth emphasising that these patients did not have atherogenic dyslipidemia, an important driver of cardiovascular risk at all LDL-C levels.6 Indeed, in routine clinical practice, it is highly unlikely that such patients would have been prescribed niacin.
Where data are available for AIM-HIGH, the signals for adverse events in both AIM-HIGH and HPS2-THRIVE were consistent. Both studies showed an increase in stroke (ischemic stroke in AIM-HIGH, hemorrhagic stroke in HPS2-THRIVE), gastrointestinal side effects, and elevated blood glucose (consistent with an increase in new-onset diabetes) with niacin (±laropiprant). While it has been suggested that the safety issues in HPS2-THRIVE may be in part due to laropiprant, which attenuates niacin-associated flushing, this cannot be addressed in the absence of comparator arms for niacin or laropiprant monotherapy. Taken together, risk/benefit analysis based on data from both studies suggest that niacin is not an option for combination with a statin in high-risk patients, including those with insulin resistance and/or (pre)diabetes.
In conclusion, data from clinical trials with niacin imply that it is not suitable for combination with a statin in patients at high-risk of cardiovascular disease. The studies clearly reinforce the view of the R3i that other options are urgently needed to manage the high residual cardiovascular risk that persists in such patients.
1. Fruchart JC, Sacks FM, Hermans MP et al. The Residual Risk Reduction Initiative: a call to action to reduce residual vascular risk in dyslipidaemic patient. Diab Vasc Dis Res 2008;5:319-35.