CD&D National Editor and Staff Reports

Researchers have discovered a potential mechanism by which briefly cutting off, then restoring, blood flow to arteries prior to a heart attack lessens the damage caused, according to a study published in the journal Cardiovascular Research.

The researchers say the new mechanism points to how future drugs could provide protection ahead of heart attacks and strokes for those at highest risk. In the near term, they say the work may help to prevent damage caused when heart surgeons temporarily cut off blood flow 450,000 to perform coronary artery bypass graft surgeries.

It is known that clearing of a blocked artery and reperfusion of blood throws off cellular chemistry, creating a burst of "free radicals" that tear apart cell components and cause cells to self-destruct, producing inflammation and potential heart failure.

In 1986 Chuck Murry, a student at Duke University (Durham, North Carolina), described a technique called ischemic preconditioning (IPC), which cuts off then restores blood flow to the heart but protected heart tissue against the damage caused by subsequent, prolonged blood vessel blockages. In the current study, researchers have determined how IPC works, by causing a key molecule, nitro-linoleic acid (LNO2), to be made in ischemic cells.

"LNO2 appears to be important in the mechanism by which IPC triggers the body's natural defense mechanisms against heart attack before the major attack comes," said Paul Brookes, PhD, associate professor of anesthesiology and of pharmacology and physiology at the University of Rochester Medical Center (Rochester, New York).

"Obviously, this natural response, when it follows a major heart attack, is often too little too late," he said. "Our hope is that boosting the effect in patients at high risk, perhaps by administering LNO2 beforehand, will reduce heart attack damage in the future. Even sooner, we may be able dramatically reduce reperfusion injury suffered in surgical settings."

It has been thought that a group of proteins in the mitochondrial membrane act as a "safety valve" by dissipating too large proton gradients when necessary, which slows free radical generation. The current study identified a novel mechanism involving LNO2, by which IPC turns on this safety valve.

Given their results, the study authors propose the following protective mechanism: temporary ischemia causes the generation of nitrated lipids inside the mitochondria via unknown mechanisms involving metabolites of nitric oxide (NO). These lipids, including LNO2, then become attached to two proteins – adenine nucleotide translocase and uncoupling protein 2 – changing their shape so that they allow a proton leak across the mitochondrial membrane. The leak lowers the proton gradient just enough to lessen free radical production.

The major finding of the study is that LNO2 is formed naturally in mitochondria during IPC in an isolated rat heart, and that adding extra LNO2 protects heart muscle cells from IR injury. The team measured the ability of isolated rat heart cells to survive ischemia using a dye that the live cells keep out, but that dead cells take in. That enabled researchers to count how many cells survived with and without LNO2 added.

In normal cells following ischemia 70% died, but for those receiving extra LNO2 (0.5 micromolar), only 30% died. The amount of the LNO2 added was not much more than naturally occurs, suggesting that its effect is "extremely potent," researchers said.

The LNO2-related proton leak also occurs at the protein level within seconds, a vital quality of any future therapy, considering that IR injury greatly increases with each second it is allowed to proceed.

"Our interest in this area stems from the fact that many different stimuli appear to funnel down into the mitochondria where they may trigger LNO2 production, any of which may suggest a new way to prevent damage," Freeman said. "Along with IPC, olive oil has been shown to produce LNO2 in the stomach, offering an explanation for the value of the Mediterranean diet."

American Society of Hematology reports

A variety of studies presented at the recent 50th annual meeting of the American Society of Hematology (ASH; Washington) in San Francisco reported advances in a variety of therapeutics.

• Soliris (eculizumab), a terminal complement inhibitor developed by Alexion Pharmaceuticals (Cheshire, Connecticut) was observed by investigators to reduce blood measures associated with undiagnosed blood clots and inflammation in patients with PNH. Results showed that prior to treatment with Soliris, patients with PNH exhibited a hypercoagulable state as indicated by elevated levels of key inflammatory and pro-thrombotic measures.

Soliris treatment was associated with statistically significant decreases in key blood measures, including LDH levels, D-dimers, thrombin-antithrombin complex or TAT, interleukin 6 or Il-6, and tissue factor microparticles or TFMP during the four-week induction phase of treatment. All decreases in D-dimers were sustained in the maintenance phase of treatment.

A separate study found that Soliris reduced indicators of pulmonary artery hypertension (PAH) in patients with paroxysmal nocturnal hemoglobinuria (PNH), according to a new analysis of clinical trial data. Research titled "Eculizumab Reduces Pulmonary Hypertension through Inhibition of Hemolysis-Associated Nitric Oxide Consumption in Patients with Paroxysmal Nocturnal Hemoglobinuria" was presented in an oral session at the ASH meeting by Anita Hill, MD, of the department of hematology at Bradford Royal Infirmary (Bradford, UK).

Using data from the Phase III TRIUMPH study of Soliris, Hill and her colleagues evaluated the efficacy of Soliris in the regulation of cell-free plasma hemoglobin levels, nitric oxide depletion and subsequent cardiovascular morbidities in patients with PNH.

This analysis found that 47% of patients with PNH (34 of 73) suffered from pulmonary hypertension before starting the trial. In this study, PAH was measured by an elevated blood level of NT-proBNP, which has been shown to be highly predictive of PAH and an independent predictor of mortality in other hemolytic diseases.

• Patients with non-valvular atrial fibrillation (AF) receiving either 30 mg or 60 mg once-daily dose of DU-176b, an investigational oral Factor Xa inhibitor, experienced comparable safety and tolerability compared to those taking warfarin, according to new Phase II data. The findings are the first results from a Phase II clinical study evaluating an oral Factor Xa inhibitor in AF patients. DU-176b is being developed by Daiichi Sankyo (Parsippany, New Jersey).

While the incidence of major and clinically relevant non-major bleeding events was significantly higher in the twice-daily DU-176b treatment groups (30 mg or 60 mg twice per day), compared with warfarin, the incidence reported in the once-daily DU-176b treatment groups (30 mg or 60 mg once per day) was similar to that in the warfarin-treated patient group.

The incidence of major and clinically relevant non-major bleeding events was significantly higher with the 30 mg and 60 mg twice-daily DU-176b regimens than it was in patients given warfarin. In contrast, the incidence of major and clinically relevant non-major bleeding events with the 30 mg and 60 mg once-daily DU-176b regimens was comparable to that with warfarin.

There were no significant differences in the numbers of patients with elevated liver enzymes or bilirubin across all treatment groups. Although the study was not powered to detect efficacy, there were no significant differences in the rates of secondary efficacy endpoints across treatment groups.

Results from a pre-specified pooled analysis of the RECORD clinical trial program confirmed that the novel oral anticoagulant Xarelto (rivaroxaban), taken as one tablet, once-daily, was superior to enoxaparin-based treatment regimens for the prevention of venous thromboembolism (VTE) after total knee or hip replacement surgery with low rates of major bleeding that were not statistically different from the comparator. Pooled results from the four RECORD trials, involving more than 12,500 patients. RECORD is the largest clinical trial program ever conducted of an oral anticoagulant in the prevention of VTE after such surgeries.

The RECORD studies evaluated Xarelto (10 mg given as one tablet, once-daily), a joint development of Bayer (Leverkusen, Germany) and Johnson & Johnson (New Brunswick, New Jersey) in the prevention of VTE following elective total knee replacement surgery (TKR) or total hip replacement surgery (THR) against enoxaparin at various doses and treatment durations. The pooled analysis had a primary composite efficacy endpoint of symptomatic VTE [symptomatic deep vein thrombosis (DVT) and symptomatic non-fatal pulmonary embolism (PE)] and all-cause mortality, which was analyzed at three different time points.

At the three time points, patients treated with rivaroxaban demonstrated a statistically significant reduction of more than 50% in the composite primary efficacy endpoint compared to patients treated with enoxaparin. Results for the composite endpoint of major and clinically relevant non-major bleeding were also low but statistically significantly different for the total treatment duration time period.

However, the rates were not statistically significantly different in the head-to-head treatment pool, which included the majority of reported bleeding cases in these criteria, 2.8% for Xarelto vs. 2.5% for enoxaparin.

Lipitor boosted by ACCOMPLISH

Pfizer (New York) reported the results of an observational study, Avoiding Cardiovascular Events through Combination Therapy in Patients Living with Systolic Hypertension (ACCOMPLISH), showing that patients taking Lipitor (atorvastatin calcium) had a significant 13% reduction in the relative risk of experiencing a cardiovascular event compared with patients taking ocor (simvastatin). The patients in this study did not have evident cardiovascular disease and were newly initiated on either treatment.

The study was performed in conjunction with HealthCore, the health outcomes research subsidiary of Wellpoint (Indianapolis). Results of this study, from a U.S. managed care claims database of more than 219,000 adult patients, appeared in the December issue of Mayo Clinic Proceedings.

The study examined data for patients 18 to 64 years old who had no prior statin use or medical claims related to cardiovascular disease in the 12 months preceding initiation of statin therapy. The average doses in the study were 29 mg of simvastatin and 17 mg of Lipitor.

Terry Jacobson, professor of medicine at Emory University (Atlanta) and director of the Office of Health Promotion and Disease Prevention, Grady Health Systems (also Atlanta), said the data from ACCOMPLISH "suggests that statins with greater potency may result in greater cardiovascular risk reductions. Economic assessments should be performed to determine the potential impact of this study on cost of care to patients."

In addition to the significant reduction in the risk of overall cardiovascular events, individual event rates of secondary endpoints, first heart attack and hospitalizations for heart failure, were significantly lower for patients initiating Lipitor compared with patients initiating simvastatin. There was no significant difference between the groups for the secondary endpoints of stroke, revascularization surgery or peripheral vascular disease.

The retrospective analysis examined administrative claims for statin prescriptions filed between January 2003 and December 2005. The longer mean treatment duration of patients who took Lipitor vs. simvastatin (nine and seven months, respectively) might have impacted the difference in cardiovascular event reduction.

Pfizer said that the study results complement a large body of evidence from multiple clinical trials demonstrating the cardiovascular benefits of Lipitor in patients without heart disease and are in alignment with findings from previously published observational studies.

In brief …

• Ablynx (Ghent, Belgium) said results of a 25-patient Phase Ib study showed that ALX-0081, when added to a standard antithrombotic regimen in patients undergoing percutaneous coronary intervention, was safe and well tolerated. ALX-0081 is a first-in-class therapeutic Nanobody targeting von Willebrand Factor developed to reduce the risk of thrombosis in patients with acute coronary syndrome. The company said the positive Phase Ib results will support the progress of ALX-0081 into Phase II development in 2009.
• ARYx Therapeutics (Fremont, California) reported results of a pharmacokinetic study of ATI-5923 and showed that exposure and elimination rate of ATI-5923 are unaffected by CYP 2C9/3A4 inhibitor fluconazole (FCZ) treatment, while the levels of warfarin were dramatically increased by FCZ treatment. In addition, data from a study of ATI-5923 in 66 patients with atrial fibrillation indicate that patients had more stable control of anticoagulation with ATI-5923 than with prior warfarin therapy, and that patients with CYP2C9 (a gene involved in warfarin metabolism) genetic variations exhibited even greater improvement in the control of anticoagulation when on ATI-5923 than when on warfarin.

ARYx is conducting a Phase II/III trial of ATI-5923, a novel vitamin K epoxide reductase inhibitor for the treatment of patients at risk of forming dangerous blood clots, against warfarin and it expects data to be available by the first half of 2009. All data were presented at the American Heart Association (Dallas) scientific sessions in New Orleans this past November.

• The Medicines Co. (Parsippany, New Jersey) said an analysis of the Acute Catheterization and Urgent Intervention Triage StrategegY (ACUity) trial showed that total hospital stay costs were lowest with Angiomax (bivalirudin) monotherpay and was associated with an initial cost savingts of $572 per patient and a total 30-day cost savings of $442 per patients when compared to heparin and GPI administered prior to catheterization in patients with moderate and high-risk acute coronary syndrome.
• Nile Therapeutics (San Francisco) reported positive preliminary data from its recently completed multi-center, open-label, ascending-dose Phase Ib study of CD-NP, a novel chimeric natriuretic peptide, in patients with heart failure. Results of this study showed CD-NP was well tolerated at doses of up to 20 ng/kg/min; blood pressure effects were dose dependent and well characterized; it demonstrated diuretic effects comparable to furosemide; and produced statistically significant changes on biomarkers consistent with enhanced renal function. A Phase IIb trials is planned for this year.