Megha Kureti

A PHARMACODYNAMIC COMPARISON OF PRASUGREL VERSUS TICAGRELOR IN PATIENTS WITH TYPE 2 DIABETES MELLITUS AND CORONARY ARTERY DISEASE: THE OPTIMUS (OPTIMIZING ANTIPLATELET THERAPY IN DIABETES MELLITUS)-4 STUDY

Background: Patients with diabetes mellitus (DM) are at increased risk of atherothrombotic events, underscoring the importance of effective platelet inhibiting therapies. Prasugrel and ticagrelor reduce thrombotic complications to a greater extent than clopidogrel. Subgroup analyses of pivotal clinical trials testing prasugrel and ticagrelor versus clopidogrel showed DM patients to have benefits that were consistent with the overall trial populations, although the magnitude of the ischemic risk reduction appeared to be enhanced with prasugrel. Whether these findings may be attributed to differences in the pharmacodynamic profiles of these drugs in DM patients remains poorly explored and represented the aim of this study. Methods: In this prospective, randomized, double-blind, double-dummy, crossover pharmacodynamic study, aspirin-treated DM patients (n=50) with coronary artery disease were randomly assigned to receive prasugrel (60 mg loading dose [LD]/10 mg maintenance dose once daily) or ticagrelor (180 mg LD/90 mg maintenance dose twice daily) for 1 week. Pharmacodynamic assessments were conducted using 4 different assays, including VerifyNow P2Y12, vasodilator-stimulated phosphoprotein, light transmittance aggregometry, and Multiplate, which allowed us to explore ADP- and non–ADP-induced (arachidonic acid-, collagen-, thrombin receptor-activating, peptide-induced) platelet signaling pathways. The acute (baseline, 30 minutes, and 2 hours post-LD) and maintenance (1 week) effects of therapy were assessed. The primary end point of the study was the comparison of P2Y12 reaction units determined by VerifyNow P2Y12 at 1 week between prasugrel and ticagrelor. Results: ADP- and non–ADP-induced measures of platelet reactivity reduced significantly with both prasugrel and ticagrelor LD and maintenance dose. P2Y12 reaction units defined by VerifyNow were similar between prasugrel and ticagrelor at 30 minutes and 2 hours post-LD. At 1 week, P2Y12 reaction units were significantly lower with ticagrelor than with prasugrel (52 [32–72] versus 83 [63–103]; least-square means difference: –31; 95% confidence interval, –57 to –4; P=0.022; primary end point). Pharmacodynamic assessments measured by vasodilator-stimulated phosphoprotein, light transmittance aggregometry, and Multiplate were similar between prasugrel and ticagrelor at each time point, including at 1 week. Rates of high on-treatment platelet reactivity were similar between groups with all assays at all time points. Conclusions: In DM patients with coronary artery disease, ticagrelor exerts similar or greater inhibition of ADP-induced platelet reactivity in comparison with prasugrel in the acute and chronic phases of treatment, whereas the inhibition of measures of non–ADP-induced platelet reactivity was not significantly different between the 2 agents. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01852214.

Role of genetic testing in patients undergoing percutaneous coronary intervention.

ABSTRACT Introduction: Variability in individual response profiles to antiplatelet therapy, in particular clopidogrel, is a well-established phenomenon. Genetic variations of the cytochrome P450 (CYP) 2C19 enzyme, a key determinant in clopidogrel metabolism, have been associated with clopidogrel response profiles. Moreover, the presence of a CYP2C19 loss-of-function allele is associated with an increased risk of atherothrombotic events among clopidogrel-treated patients undergoing percutaneous coronary interventions (PCI), prompting studies evaluating the use of genetic tests to identify patients who may be potential candidates for alternative platelet P2Y12 receptor inhibiting therapies (prasugrel or ticagrelor). Areas covered: The present manuscript provides an overview of genetic factors associated with response profiles to platelet P2Y12 receptor inhibitors and their clinical implications, as well as the most recent developments and future considerations on the role of genetic testing in patients undergoing PCI. Expert commentary: The availability of more user-friendly genetic tests has contributed towards the development of many ongoing clinical trials and personalized medicine programs for patients undergoing PCI. Results of pilot investigations have shown promising results, which however need to be confirmed in larger-scale studies to support the routine use of genetic testing as a strategy to personalize antiplatelet therapy and improve clinical outcomes.

Pharmacodynamic Effects of Switching From Ticagrelor to Clopidogrel in Patients With Coronary Artery Disease: Results of the SWAP-4 Study

Background: Switching between different classes of P2Y12 inhibitors, including de-escalation from ticagrelor to clopidogrel, commonly occurs in clinical practice. However, the pharmacodynamic profiles of this strategy have been poorly explored. Methods: This was a prospective, randomized, open-label study conducted in patients on maintenance dosing (MD) of aspirin (81 mg/d) and clopidogrel (75 mg/d). After a 7-day run-in with ticagrelor (180 mg loading dose [LD] followed by 90 mg twice daily MD), patients (n=80) were randomized into 1 of 4 groups: group A, clopidogrel 600 mg LD 24 hours after the last MD of ticagrelor (C-600 mg-24h); group B, clopidogrel 600 mg LD 12 hours after the last MD of ticagrelor (C-600 mg-12h); group C, clopidogrel 75 mg/d MD 24 hours after the last MD of ticagrelor (C-75 mg-24h); and group D, ticagrelor 90 mg twice daily MD (T-90 mg twice daily). MD of the randomized treatment was maintained for 10±3 days. Pharmacodynamic assessments were performed at baseline, after run-in, and at 2, 24, 48, and 72 hours and 10 days with P2Y12 reaction units by VerifyNow; platelet reactivity index was assessed by vasodilator-stimulated phosphoprotein; and maximal platelet aggregation was determined by light transmittance aggregometry. Results: T-90 mg twice daily led to lower platelet reactivity than any clopidogrel regimen using all assays at all time points. P2Y12 reaction unit levels were similar between the C-600 mg-24h (group A) and the C-75 mg-24h (group C) (P=0.29), including at 48 hours (primary end point; least mean difference, −6.9; 95% confidence interval, −38.1 to 24.3; P=0.66). P2Y12 reaction unit levels were lower with C-600 mg-12h (group B) than with C-75 mg-24h (group C; P=0.024). Maximal platelet aggregation over time was lower with both C-600 mg-24h (group A; P=0.041) and C-600 mg-12h (group B; P=0.028) compared with C-75 mg-24h (group C). Platelet reactivity index profiles paralleled those observed with P2Y12 reaction units. There were no pharmacodynamic differences for all tests between C-600 mg-24h (group A) and C-600 mg-12h (group B). In group C (C-75 mg-24h), platelet reactivity increased compared with baseline as early as 24 hours, reaching statistical significance at 48 and 72 hours and up to 10 days. These pharmacodynamic findings were delayed and blunted in magnitude with the administration of an LD, regardless of the timing of administration. Conclusions: De-escalation from ticagrelor to clopidogrel therapy is associated with an increase in platelet reactivity. The use of an LD before the initiation of an MD regimen of clopidogrel mitigates these observations, although this is not affected by the timing of its administration after ticagrelor discontinuation. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02287909.

IN VITRO PHARMACODYNAMIC EFFECTS OF CANGRELOR ON PLATELET P2Y12 RECEPTOR MEDIATED SIGNALING IN TICAGRELOR TREATED PATIENTS

Variability in the onset of platelet inhibitory effects induced by oral P2Y12 receptor antagonists, including ticagrelor, has been shown in high-risk settings. These findings underscore the need for intravenous P2Y12 inhibiting therapies, such as cangrelor, with immediate effects. However, to date