Clinical Feature: Clinical Trial Evidence for the Role of Reducing Inflammation for Cardiovascular Disease Prevention

Introduction

Despite significant advances in detection and treatment, cardiovascular disease (CVD) is the leading cause of death and disability worldwide.(1,2) The 3-hydroxymethylglutaryl coenzyme A (HMGCoA) reductase inhibitors (aka statins) ushered in a new era for prevention of cardiovascular disease. The first statin, lovastatin, became commercially available in 1987. This was followed in 1994 by the landmark Scandinavian Simvastatin Survival Study (4S), which demonstrated that lowering low-density lipoprotein cholesterol (LDL-C) led to significant reductions in major atherosclerotic CVD and atherosclerotic cardiovascular disease (ASCVD) events.(2,3) Since then, statin therapy has remained the cornerstone of ASCVD prevention and has been coined “the single most important advance in the therapeutic armamentarium against CVD.”(4) Despite statins’ remarkable benefits, approximately 60% to 70% of ASCVD events continue to occur in statintreated patients, an observation referred to as residual cardiovascular risk.(5,6) Recent studies involving the cholesterol absorption inhibitor ezetimibe and the proprotein convertase subtilisin-like/kexin type 9 (PCSK9) inhibitors evolocumab and alirocumab have confirmed that lower LDL-C is associated with reduced ASCVD events, regardless of the agent used and proportional to the degree of LDL-C lowering.(7-10) Yet, even with aggressive LDL-C reduction, vascular events continue to occur at an alarming rate, suggesting that there are additional important factors at play. This review will focus on inflammation as a risk factor for — and therapeutic target of — ASCVD residual risk reduction.

Inflammatory markers linked to ASCVD Several lines of evidence — ranging from epidemiologic to genetic, experimental and clinical trials — have linked inflammation to all phases of atherosclerosis.(11,12) Broadly, the inflammatory mediators can be classified into those involving a central pathway or an alternative pathway. The central inflammatory pathway involves activation of the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, resulting in BRUCE A. WARDEN, PharmD, BCPS-AQ Center for Preventive Cardiology Knight Cardiovascular Institute Oregon Health and Science University Portland, OR CEZARY WOJCIK, MD, PhD, DsC, FNLA Department of Family Medicine Oregon Health and Science University Portland, OR Diplomate, American Board of Clinical Lipidology MICHAEL D. SHAPIRO, DO, FNLA Center for Preventive Cardiology Knight Cardiovascular Institute Oregon Health and Science University Portland, OR Diplomate, American Board of Clinical Lipidology Discuss this article at www.lipid.org/lipidspin 8 LipidSpin • Volume 17, Issue 1 • January 2019 the production of interleukin-1® (IL-1®), which binds to its specific interleukin-1 (IL-1) receptor, initiating the production of interleukin-6 (IL-6) and other downstream mediators, including the non-specific liverderived acute-phase reactant C-reactive protein (CRP)(see Fig. 1). Interestingly, cholesterol crystals within atherosclerotic plaque activate the NLRP3 inflammasome to initiate this cascade of events, providing a mechanistic link between hypercholesterolemia and vascular inflammation. The alternative inflammatory pathway involves lipoprotein-associated phospholipase A2 (Lp-PLA2), secretory PLA2 (sPLA2), P-selectin, 5-lipoxygenase (5-LO) and other mediators.(13)

Clinical Trial Evidence Agents targeting the central immune signaling pathway The CRP molecule is now well stablished as a downstream biomarker of inflammation, associated with risk of ASCVD and independent of traditional risk factors. High-sensitivity CRP (hsCRP) levels <1, 1-3 and >3 mg/L confer low, moderate and high vascular risk, respectively (12). Statins lower CRP independently of LDL-C reduction. In fact, in the Cholesterol and Recurrent Events (CARE) trial, greater ASCVD reduction was noted in those subjects with higher baseline hsCRP levels.(14) This observation was recapitulated in several other statin trials.(15-18) The consistency of this finding gave birth to the notion of dual targets — greatest ASCVD risk reduction realized with a combination of reduced LDL-C (<70 mg/dl) and hsCRP (<2 mg/L). (15-18) Moreover, the concept of dual targets has been extended in trials of nonstatin therapies, including ezetimibe in the Improved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT) and evolocumab in the Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER ) trials.(19, 20) While ezetimibe appears to share at least some anti-inflammatory effects with statins, PCSK9 inhibitors do not reduce hsCRP or other inflammatory markers, despite dramatic LDL-C lowering.(19)

Ten years ago, the landmark Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial went beyond evaluation of the incremental prognostic value of hsCRP. JUPITER was a randomized, doubleblind, placebo-controlled, multicenter trial that enrolled 17,802 apparently healthy (primary prevention) subjects (age ≥50 years for men and ≥60 years for women, LDL-C <130 mg/dl and hsCRP ≥2 mg/L), who would not otherwise qualify for guideline-directed statin therapy.(6) Subjects were randomized to rosuvastatin 20 mg or placebo. The trial was terminated prematurely after a median follow-up of 1.9 years because of significant cardiovascular event reduction among rosuvastatin recipients. At the time of study termination, those in the rosuvastatin group experienced a 49% LDL-C reduction (to 55 mg/dl) and a 48% reduction in hsCRP (to 2.2 mg/L). The primary endpoint (non-fatal myocardial infarction [MI], non-fatal stroke, hospitalization for unstable angina [UA], arterial revascularization or cardiovascular [CV] death) occurred in 0.77% vs. 1.36% [hazard ratio (HR) 0.56; 95% confidence interval (CI) (0.46-0.69), number needed to treat (NNT) of 95] in the rosuvastatin vs. placebo groups, respectively. All-cause mortality also was reduced 20%, relative to placebo. As previously discussed in the context of other clinical trials, the greatest absolute risk reduction with rosuvastatin occurred in those with the highest levels of hsCRP.(21) Importantly, the lowest event rates were observed in those who achieved both an LDL-C <70 mg/dl and hs-CRP <2 mg/L. Whether the benefit seen in JUPITER was because of LDL-C lowering, reduction in inflammation or both was not clear.

Thus, the JUPITER trial did not prove the inflammatory hypothesis for reduction of ASCVD risk. Nevertheless, American and European guidelines both endorse hsCRP as a biomarker to refine risk estimates in select patients.(22, 23)

On the heels of JUPITER, the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) was the first trial to prospectively test the inflammatory hypothesis of ASCVD.(24) CANTOS enrolled 10,061 subjects with a past history of MI and hsCRP ≥2 mg/L on stable background medical therapy and randomized them to placebo or one of three doses of canakinumab, a fully human monoclonal antibody that inhibits IL-1β, every 3 months. Median LDL-C and hsCRP at baseline were 82 mg/dl and 4.2 mg/L, respectively. As compared to placebo, hsCRP was reduced by 26%, 37% and 41% in the canakinumab 50 mg, 150 mg and 300 mg groups, respectively. Similar trends were seen for reductions in IL-6 levels without significant reduction in LDL-C. Over a median follow-up of 3.7 years, the primary efficacy endpoint (non-fatal MI, non-fatal stroke, CV death) was 4.5%, 4.11%, 3.86% and 3.9% among the placebo, canakinumab 50 mg, 150 mg and 300 mg groups. Canakinumab, 150 mg subcutaneously every 3 months, met the primary endpoint with a 15% reduction of non-fatal MI, nonfatal stroke or cardiovascular death, an effect size strikingly similar to what was seen in the cardiovascular outcomes trials with the PCSK9 inhibitors.(8-10) Additionally, subjects randomized to canakinumab 150 mg every 3 months achieved significant reductions in MI, hospitalization for UA leading to urgent revascularization and any coronary revascularization. There was no impact on CV or all-cause death. Remarkably, fatal cancers (especially lung), arthritis and gout were reduced with canakinumab. The most important adverse event observed with canakinumab Official Publication of the National Lipid Association 9 was a higher rate of fatal infection or sepsis, 0.18% vs. 0.28-0.34% placebo vs. canakinumab, respectively. A posthoc subanalysis evaluated outcomes stratified by achieved hsCRP.(25) Subjects randomized to canakinumab who achieved hsCRP <2 mg/L vs ≥2 mg/L demonstrated a statistically significant relative risk reduction (RRR) of 25% in the primary efficacy endpoint of CANTOS vs. a nonsignificant RRR of 10%, respectively. Allcause and CV death also were significantly reduced in those with on-treatment hsCRP < 2 mg/L. Thus, on-treatment hsCRP value may prove to be a useful tool to determine continued treatment with canakinumab. However, the U.S. Food and Drug Administration (FDA) recently decided not to approve canakinumab for a new indication of CV risk reduction. The FDA is seeking additional data in the responder population. For the first time, CANTOS provides proof of concept that targeting inflammation — without impacting lipoprotein levels — can further reduce ASCVD events, and it opens the door for future investigation into the therapeutic modulation of inflammation for CV risk reduction.

Figure 1. Overview of the role of inflammation in the development of atherosclerotic plaque. Circulating monocytes penetrate the arterial wall and enter the subendothelial space through diapedesis to become macrophages. As these arterial wall macrophages engulf low-density lipoprotein particles, they transform into foam cells, which elaborate several inflammatory mediators, acting both locally and systemically. Lipidladen foam cells undergo cell death, contributing to the necrotic core of the growing plaque, while smooth muscle cells proliferate and migrate from the media toward the intima. Different stages of the inflammatory process involve specific mediators, which are targets (orange boxes) of different categories of drugs (white boxes) discussed in the article. Graphic created by Dr. Thomas Dayspring has been modified and used with his permission.

In this regard, the medical community waits with interest for the results of the Cardiovascular Inflammation Reduction Trial (CIRT). CIRT enrolled 4,786 subjects with prior MI, diabetes mellitus or metabolic syndrome and randomized them to oral low-dose methotrexate (target dose of 15-20 mg per week) vs. placebo (26). The CIRT trial was terminated prematurely on March 13, 2018. The results were presented at the American Heart Association meeting in November 2018.(27)

Agents targeting alternative immune signaling pathways Modulation of non-central inflammatory pathways has yet to produce promising clinical results. While lipoproteinassociated phospholipase A2 (Lp-PLA2) has been validated as a risk marker (28), Lp-PLA2 inhibitors have failed to demonstrate benefit in three Phase III cardiovascular outcome trials.(29-31) The Vascular Inflammation Suppression to Treat Acute Coronary Syndrome for 16 Weeks (VISTA-16) trial enrolled 5,145 ACS patients who were randomly allocated to placebo or varespladib, an oral secretory PLA2 (sPLA2) inhibitor. Active therapy was associated with modest reductions in LDL-C and CRP compared to placebo, but the study was prematurely terminated because of futility and possible harm (excess MI rates, 3.4% vs. 2.2%, HR 1.66 ; 95% CI 1.16-2.39) (29). The second agent, darapladib, which is an oral Lp-PLA2 inhibitor, failed to demonstrate benefit in 15,828 subjects with stable CAD over 3.7 years in the Stabilization of Atherosclerotic plaque by Initiation of Darapladib Therapy (STABILITY) trial and in 13,026 subjects presenting with an ACS over 2.5 years in the Stabilization of Plaque Using Darapladib — Thrombolysis in Myocardial Infarction-52 (SOLID-TIMI 52) trial (30, 31). The STABILITY trial did reduce the secondary endpoints of major and total coronary events (p=0.0045 and 0.02, respectively). However, the significance of these findings remains unclear given the lack of effect on the primary cardiovascular endpoint. Moreover, in both STABILITY and SOLID-TIMI 52, more patients discontinued therapy because of adverse events.

Inclacumab, a monoclonal antibody targeting P-selectin, a cell adhesion molecule expressed on endothelial cells and platelets that promotes leukocyte recruitment and thrombus growth and stabilization, revealed promising results in a small Phase II trial, Effects of the P-Selectin Antagonist Inclacumab on Myocardial Damage After Percutaneous Coronary Intervention for Non-ST-Segment Elevation Myocardial Infarction (SELECTACS) by reducing troponin and creatine kinase-myocardial band.(32) However, inclacumab failed to reduce vein graft disease progression in a Phase II trial involving patients undergoing coronary artery bypass, Effects of P-Selectin Antagonist Inclacumab in Patients Undergoing Coronary Artery Bypass Graft Surgery (SELECT-CABG).(33) No Phase III trials of inclacumab have been conducted to date.

Succinobucol, a derivative of probucol, is an orally active antioxidant without the QT-prolonging effect. Succinobucol was evaluated in a Phase III trial, Aggressive Reduction of Inflammation Stops Events (ARISE), of 6,144 subjects presenting with ACS. (34) The trial did not meet its primary endpoint but demonstrated statistically significant reductions in some of the secondary and tertiary outcomes. However, several safety concerns were noted, including increases in hospitalizations for heart failure, newonset atrial fibrillation, bleeding, anemia, diarrhea and increases in LDL-C and hsCRP.

The p38 Mitogen-activated proteinkinase (MAPK) is an enzyme expressedin endothelial cells, myocytes and macrophages that magnifies the inflammatory cascade through overproduction of various cytokines, and it may be linked to atherogenesis development and plaque destabilization. Losmapimod, an oral p38 MAPK inhibitor, was evaluated in 3,503 ACS patients in the Phase III trial Losmapimod to Inhibit p38 MAP Kinase as a Therapeutic Target and Modify Outcomes After an Acute Coronary Syndrome (LATITUDE–TIMI 60). Losmapimod did not reduce the primary cardiovascular outcome in the smaller exploratory efficacy analysis and, thus, the investigators did not proceed with a larger efficacy analysis.(35)

Emerging Therapies

There are numerous other antiinflammatory therapies that are in various stages of evaluation for ASCVD risk reduction. Colchicine, an oral anti-inflammatory agent that inhibits neutrophil function through inhibition of tubulin polymerization, significantly reduced CV events in a small unblinded trial — Low-Dose Colchicine (LoDoCo). Two additional Phase III studies testing colchicine in this context include the Colchicine Cardiovascular Outcome Trial (COLCOT) and the Low-Dose Colchicine for Secondary Prevention of Cardiovascular Disease (LoDoCO2) trial.(11) COLCOT will evaluate subjects with ACS with an anticipated completion date of fall 2019. The interleukin-1 receptor antagonists (IL1RA), anakinra and rilonacept, are subcutaneously administered and currently are being evaluated in Phase II trials in ACS and chronic kidney disease patients, respectively.(36) These agents currently have no Phase III studies under way.

An early Phase I/II trial, Controlled Level Everolimus in Acute Coronary Syndromes (CLEVER-ACS) will examine the oral mammalian target of rapamycin (mTOR) inhibitor everolimus in ACS patients to determine its ability to reduce infarct size, myocardial function and inflammation.(36) Estimated study completion date is winter 2019. Of note, mTOR inhibitor use in solid organ transplant recipients has been associated with profound dyslipidemias, potentially limiting its role in ASCVD management.

The 5-LO inhibitor (Atreleuton,VIA-2291) was evaluated in three Phase II studies. While therapy was associated with a reduction in inflammatory markers and new coronary calcification, it failed to demonstrate a difference in inflammatory cell infiltration in subjects undergoing carotid endarterectomy.(11)

Finally, salsalate, an anti-inflammatory derivative of aspirin that does not inhibit cyclooxygenase (and, thus, has no effect on bleeding or platelet aggregation), reduces leukocyte counts, likely as a result of its effect on NF-κB.(11) Earlier studies with salsalate demonstrated reductions in hsCRP. Salsalate is now being evaluated in the Phase II/III Targeting Inflammation Using Salsalate in Cardiovascular Disease (TINSAL-CVD) trial in subjects with established CAD to determine if this therapy can promote plaque regression. The anticipated study completion date is winter 2019.(36)

Summary

Despite remarkable achievements in therapeutic LDL-C lowering with concomitant decline in atherosclerotic events, residual cardiovascular risk remains unacceptably high. In the wake of the CANTOS trial, there is renewed enthusiasm for orthogonal approaches to ASCVD risk reduction, particularly with respect to targeting inflammation. Numerous trials now are under way, testing a variety of other anti-inflammatory agents to determine if this will be an effective means by which to further erode residual CV risk.

Disclosure statement: Dr. Warden has no financial disclosures to report. Dr. Wojcik has no financial disclosures to report. Dr. Shapiro has received honoraria from Kastle, Novartis and Regeneron.