Verifying Death Reports in the Platelet Inhibition and Patient Outcomes (PLATO) Trial.

BACKGROUND: Excess vascular deaths in the PLATO trial comparing ticagrelor to clopidogrel have been repeatedly challenged by the Food and Drug Administration (FDA) reviewers and academia. Based on the Freedom of Information Act, BuzzFeed won a court order and shared with us the complete list of reported deaths for the ticagrelor FDA New Drug Application (NDA) 22-433. This dataset was matched against local patient-level records from PLATO sites monitored by the sponsor. STUDY QUESTION: Whether FDA death data in the PLATO trial matched the local site records. STUDY DESIGN: The NDA spreadsheet contains 938 precisely detailed PLATO deaths. We obtained and validated local evidence for 52 deaths among 861 PLATO patients from 14 enrolling sites in 8 countries and matched those with the official NDA dataset submitted to the FDA. MEASURES AND OUTCOMES: Existence, precise time, and primary cause of deaths in PLATO. RESULTS: Discrepant to the NDA document, sites confirmed 2 extra unreported deaths (Poland and Korea) and failed to confirm 4 deaths (Malaysia). Of the remaining 46 deaths, dates were reported correctly for 42 patients, earlier (2 clopidogrel), or later (2 ticagrelor) than the actual occurrence of death. In 12 clopidogrel patients, cause of death was changed to "vascular," whereas 6 NDA ticagrelor "nonvascular" or "unknown" deaths were site-reported as of "vascular" origin. Sudden death was incorrectly reported in 4 clopidogrel patients, but omitted in 4 ticagrelor patients directly affecting the primary efficacy PLATO endpoint. CONCLUSIONS: Many deaths were inaccurately reported in PLATO favoring ticagrelor. The full extent of mortality misreporting is currently unclear, while especially worrisome is a mismatch in identifying primary death cause. Because all PLATO events are kept in the cloud electronic Medidata Rave capture system, securing the database content, examining the dataset changes or/and repeated entries, identifying potential interference origin, and assessing full magnitude of the problem are warranted.

Pharmacokinetics and pharmacodynamics of the antiplatelet combination aspirin (acetylsalicylic acid) plus extended-release dipyridamole are not altered by coadministration with the potent CYP2C19 inhibitor omeprazole.

BACKGROUND: The fixed-dose combination of aspirin (acetylsalicylic acid) 25 mg plus extended-release dipyridamole 200 mg (ASA+ER-DP) is used for long-term secondary stroke prevention in patients who have experienced non-cardioembolic stroke or transient ischemic attack. Although the theoretical risk is low that the antiplatelet activity of ASA+ER-DP will be affected by concomitant use of a proton pump inhibitor (PPI), no formal drug-drug interaction studies have been conducted. OBJECTIVE: This study aimed to determine whether the PPI omeprazole influences the pharmacokinetic (PK) and pharmacodynamic (PD) behavior of ASA+ER-DP. STUDY DESIGN AND SETTING: This was a randomized, open-label, multiple-dose, crossover, drug-drug interaction study carried out in a clinical trial unit. PARTICIPANTS: Sixty healthy male and female volunteers aged 18-50 years were included in the study. INTERVENTION: Participants were randomized to one of two treatment sequences (ABCD or CDAB), each comprising four 7-day treatments with a washout of ≥14 days between the second and third treatments. Treatment A=ASA+ER-DP 25 mg/200 mg (Aggrenox®) twice daily (BID) alone; B=ASA+ER-DP 25 mg/200 mg BID+omeprazole (Prilosec®) 80 mg once daily (QD) following ASA+ER-DP alone for 7 days; C=omeprazole 80 mg QD alone; D=omeprazole 80 mg QD+ASA+ER-DP 25 mg/200 mg BID following omeprazole alone for 7 days. MAIN OUTCOME MEASURES: The main outcome measures were systemic PK exposure to ER-DP and ASA inhibition of arachidonic acid-induced platelet aggregation. RESULTS: Systemic exposure to ER-DP was similar with and without omeprazole, based on steady-state area under the concentration-time curve (AUC) from 0 to 12 h (AUC0-12,ss, ng·h/mL) and maximum plasma concentration (Cmax,ss, ng/mL). For the treatment comparison D versus A, the percent mean ratios were 96.38 (90% confidence interval [CI] 90.96-102.13) for AUC0-12,ss and 92.03 (86.95-97.40) for Cmax,ss. The ER-DP concentration versus time profiles were nearly superimposable. There was no effect on the PDs of the ASA component: the extent of ASA inhibition of arachidonic acid-induced platelet aggregation was almost identical with and without omeprazole, with a percent mean ratio for treatment D versus A = 99.02 (90 % CI 98.32-99.72) at 4 h after last dose. All treatments were well tolerated. CONCLUSION: The PK and PD behavior of ASA + ER-DP was not altered by concurrent administration of omeprazole.

Monocyte chemotactic protein-1 as a potential biomarker for early anti-thrombotic therapy after ischemic stroke.

Inflammation following ischemic brain injury is correlated with adverse outcome. Preclinical studies indicate that treatment with acetylsalicylic acid + extended-release dipyridamole (ASA + ER-DP) has anti-inflammatory and thereby neuroprotective effects by inhibition of monocyte chemotactic protein-1 (MCP-1) expression. We hypothesized that early treatment with ASA + ER-DP will reduce levels of MCP-1 also in patients with ischemic stroke. The EARLY trial randomized patients with ischemic stroke or TIA to either ASA + ER-DP treatment or ASA monotherapy within 24 h following the event. After 7 days, all patients were treated for up to 90 days with ASA + ER-DP. MCP-1 was determined from blood samples taken from 425 patients on admission and day 8. The change in MCP-1 from admission to day 8 did not differ between patients treated with ASA + ER-DP and ASA monotherapy (p > 0.05). Comparisons within MCP-1 baseline quartiles indicated that patients in the highest quartile (>217-973 pg/mL) showed improved outcome at 90 days if treated with ASA + ER-DP in comparison to treatment with ASA alone (p = 0.004). Our data does not provide any evidence that treatment with ASA + ER-DP lowers MCP-1 in acute stroke patients. However, MCP-1 may be a useful biomarker for deciding on early stroke therapy, as patients with high MCP-1 at baseline appear to benefit from early treatment with ASA + ER-DP.

Dipyridamole in antithrombotic treatment.

The antithrombotic activity of dipyridamole was initially discovered in an in vivo experiment about half a century ago. At that time science had not appreciated the complexity of the regulation of local thrombus formation. Inhibition of platelets has been the main focus for the prevention of arterial thrombus formation. Unfortunately, established in vitro test systems have to take away several important components of the hemostatic system. Rather than directly inhibiting platelet aggregation, dipyridamole amplifies endogenous antithrombotic systems and modulates or downregulates prothrombotic processes. While for many years the main focus had been on preventing acute thrombus formation in the case of a rupture of an atherosclerotic plaque in large coronary arteries, it now has been appreciated that perfusion of tissue and patency of small vessels and capillaries is equally important for preventing further damage to the tissue. Here dipyridamole was experimentally shown to improve perfusion and function in chronic hypoperfused tissue unrelated to its vasodilatory properties. Recently, several clinical trials have shown the benefit of dipyridamole when given in a formulation that assures a sufficient plasma concentration. Its potential to scavenge particularly peroxy radicals, its direct reduction of innate inflammation, and a chronic elevation of interstitial adenosine seems to be of more importance for the prevention of vascular and tissue damage than its adenosine- and prostacyclin-mediated antithrombotic effect. In its extended-release preparation with the tartaric acid nucleus, not only does it not seem to add significantly to the risk of bleeding, but seems to hold potential for protecting tissue from oxidative and metabolic stress.

Assessment of additional endpoints for trials in acute stroke - what, when, where, in who?

Functional outcome in acute stroke trials among others is usually measured on the modified Rankin Scale. However, new onset of depression, cognitive decline, and communication deficits alone or in combination affect more than 25% of patients. This report summarizes the findings and conclusions of a workshop by the European Stroke Organization held in February 2011 We propose that assessment of mood disorders, cognitive impairment/dementia, language or communication dysfunction, and quality of life should supplement outcome measures after acute stroke.

Dipyridamole Treatment Prior to Stroke Onset: Examining Post-stroke Cerebral Circulation and Outcome in Rabbits.

Clinical observations have indicated that secondary treatment with dipyridamole (DIP) may ameliorate stroke severity. The purpose of this study was to explore the effect of pre-stroke DIP treatment on stroke outcome in a rabbit model of embolic occlusion. Twenty male New Zealand white rabbits were randomly selected for intravenous treatment with DIP (n = 10) or saline (n = 10) for 7 days prior to an embolic cerebral occlusion by an autologous blood clot. Multiple computed tomography perfusion scans were acquired out to 28 days post-stroke to map cerebrohemodynamics, in conjunction with neurological assessments and histopathology. The DIP-treated group fared better than the saline group on several accounts: 66% of them survived to 28 days, whilst saline animals all had to be euthanized by day 7 due to severe neurological deficits. They presented with significantly more viable tissue in the ischemic hemisphere as well as fewer neurological deficits on days 4 and 7. Furthermore, DIP-treated animals exhibited improved cerebrohemodynamics by 24 h and had less incidence of haemorrhage within their infarcted regions (p < 0.05). DIP treatment prior to stroke onset can significantly improve neurological outcome, cerebral hemodynamics, and final infarct volume.

Dabigatran: an oral novel potent reversible nonpeptide inhibitor of thrombin.

Dabigatran is a highly selective, reversible, and potent thrombin inhibitor and is orally available as the prodrug, dabigatran etexilate. It has shown antithrombotic efficacy in animal models of thrombosis, with a rapid onset of action and predictable pharmacodynamic response. Peak plasma concentrations of dabigatran occur 1 to 2 hours after ingestion of the prodrug. The terminal half-life of dabigatran is 12 to 14 hours in elderly volunteers. Dabigatran is not metabolized by cytochrome P450 isoenzymes and does not interact with food. Dabigatran has a low potential for drug-drug interactions and is predominantly renally excreted. Dabigatran etexilate as chronic therapy effectively prevents the recurrence of venous thromboembolism and cardioembolic stroke. For the first time, it has been demonstrated clinically that there may be an effective and safe alternative to warfarin.

Dipyridamole bioavailability in subjects with reduced gastric acidity.

Dipyridamole (DP) is an antiplatelet agent that shows decreased oral bioavailability with increased gastric pH that occurs with commonly prescribed antacids. An extended-release (ER) formulation of DP that employs tartaric acid to improve bioavailability of DP in the presence of elevated gastric pH was developed as a combination antiplatelet product with immediate-release aspirin. This crossover-designed study examined the relative bioavailability of DP from the composite product compared to conventional DP tablets during reduced gastric acidity. Gastric pH was increased (pH > 4.0) in 20 healthy subjects with lansoprazole (30 mg/d for 5 days). Dipyridamole systemic exposure over 12 hours was compared after oral administration of a single composite ER capsule (200 mg DP + 25 mg aspirin) versus two 100-mg conventional DP tablets given 6 hours apart combined with 81 mg aspirin. DP relative bioavailability was reduced 53% with conventional tablets compared to the composite buffered ER capsule in reduced gastric acid conditions. Peak DP plasma concentrations were 57% lower with immediate-release tablets compared to the composite formulation with high stomach pH. Substituting generic DP plus low-dose aspirin may be less effective than the buffered DP composite product in patients with concomitant antacid therapies.

Accumulation of radiolabelled platelets and fibrin on the carotid artery of rabbits after angioplasty: effects of heparin and dipyridamole.

We investigated the dynamic accumulation of platelets and fibrin after balloon injury of the carotid arteries in rabbits in vivo. In addition, effects of heparin and dipyridamole treatment were also tested. Autologous (99m)Tc-labelled platelet and (123)I-labelled fibrin accumulation was measured at one minute intervals for 4 hours following balloon injury of the carotid artery. Platelet accumulation occurred rapidly, with an approximately 125% increase occurring within 30 min after injury. There was no further activity for up to 4 hours. This accumulation could be inhibited with an intravenous infusion of PGI2 (500 ng/kg/hr). Fibrin accumulation occurred slowly and continuously over the 4 hour measurement period. Injection of an anti-fibrin antibody inhibited fibrin accumulation. Heparin (25 U/kg/hr for 4 hrs) administration resulted in a significant 82 +/- 19% and 68 +/- 13% reduction in platelet and fibrin accumulation, respectively. This dose of heparin was associated with a 2-fold prolongation of the aPTT. Dipyridamole (0.45 mg/kg/hr for 4 hrs) resulted in a 46 +/- 12% and 70 +/- 25% reduction of platelet and fibrin accumulation, respectively. Thus, we demonstrated that the dynamics of platelet and fibrin accumulation following balloon injury in rabbits are very different. The vessel wall continues to be thrombogenic for fibrin up to 4 hours after injury even though platelet accumulation has ceased after one hour. We conclude that the local thrombotic events following balloon injury are complex and that not only platelets but also fibrin is important in regulating responses to injury.