Bedside testing of CYP2C19 gene for treatment of patients with PCI with antiplatelet therapy

Background

To mitigate the risk of stent thrombosis, patients treated by percutaneous coronary intervention (PCI) are administered dual anti-platelet therapy comprising aspirin and a platelet P2Y₁₂ receptor inhibitor. Clopidogrel is a prodrug requiring activation by the cytochrome P450 enzyme, CYP2C19. In Saudi Arabia, it has been reported that approximately 26% of the population carries CYP2C19*2 and/or *3 loss-of-function polymorphisms in addition to a high prevalence of CVD.

Methods

This prospective (April 2013–December 2020) parallel assignment clinical trial focuses on ST-Elevation Myocardial Infarction (STEMI) patient outcomes. The clinical trial includes 1500 STEMI patients from two hospitals in the Eastern Province of Saudi Arabia. Patients are assigned to one of two groups; the control arm receives conventional therapy with clopidogrel, while in the active arm the Spartan RX CYP2C19 assay is used to determine the *2 genotype. Carriers of a CYP2C19*2 loss-of-function allele receive prasugrel or ticagrelor, while non-carriers are treated with clopidogrel. Follow-up is one year after primary PCI. The primary end point is the number of patients who develop an adverse major cardiovascular event, including recurrent MI, non-fatal stroke, cardiovascular death, or major bleeding one year after PCI.

Discussion

The risk of stent thrombosis in PCI patients is usually reduced by dual anti-platelet therapy, comprising aspirin and a P2Y12 inhibitor, such as clopidogrel. However, clopidogrel requires activation by the cytochrome P450 enzyme, CYP2C19. Approximately 20% of the population are unable to activate clopidogrel as they possess the CYP2C19*2 loss-of function (LoF) allele. The primary goal of this trial is to study the benefits of treating only those patients that cannot activate clopidogrel with an alternative that has shown to be a more effective platelet inhibitor and does not require bioactivation by the cytochrome P450 enzyme. We expect an improvement in net clinical benefit outcome in the active arm patients, thus supporting pharmacogenetic testing in PCI patients post STEMI.

Trial registration

Trial registration name is “Bedside Testing of CYP2C19 Gene for Treatment of Patients with PCI with Antiplatelet Therapy” (number NCT01823185) retrospectively registered with clinicaltrials.gov on April 4, 2013. This trial is currently at the patient recruitment stage.

Perioperative management of antithrombotic therapy in patients receiving cardiovascular implantable electronic devices: a network meta-analysis

PURPOSE

Network meta-analysis (NMA) has advantages including being able to simultaneously compare and rank multiple treatments over traditional meta-analysis. We evaluated by a NMA the optimal antithrombotic strategy during the perioperative period of implantation of cardiovascular implantable electronic devices (CIEDs).

METHODS

We performed a network meta-analysis of observational studies (cohort and case-control studies). The eligible studies tested the following antithrombotic therapy during the CIED placement: aspirin, clopidogrel, warfarin, novel oral anticoagulants (NOACs), and heparin bridging.

RESULTS

Thirty-one observational studies with 119 study arms were included (41,174 patients receiving long-term antithrombotic therapy; median age, 72.6 years; 70.1% males; median follow-up, 3.6 years). Aspirin (4.26 [2.88-7.22]), warfarin (3.37 [2.17-5.23]), and clopidogrel (3.30 [1.49-5.88]) reduced the risk of bleeding as compared with heparin bridging, and there was no significance difference between continued NOACs and heparin bridging (0.67 [0.21-2.18]). The comparison of commonly used protocols in the management of anticoagulant therapy revealed that continued warfarin (0.38 [0.20-0.74]), continued NOACs (0.19 [0.04-0.89]), and heparin bridging therapy (0.01 [0.05-0.21]) increased the risk of bleeding as compared that of control, and continued warfarin (3.74 [1.96-7.16]), interrupted warfarin (4.89 [2.20-10.88]), and interrupted NOACs (12.5 [1.25-100]) reduced the risk of bleeding compared with that of heparin bridging.

CONCLUSIONS

Among various antithrombotic drugs, aspirin had the lowest bleeding risk, followed by warfarin, clopidogrel and NOACs, and heparin, with the greatest bleeding risk. NOACs therapy appears safe and effective, and interrupted NOACs may be the optimal anticoagulation protocol for use during the perioperative period of CIED implantation.

The putative role of Rhipicephalus microplus salivary serpins in the tick-host relationship

Inflammation and hemostasis are part of the host's first line of defense to tick feeding. These systems are in part serine protease mediated and are tightly controlled by their endogenous inhibitors, in the serpin superfamily (serine protease inhibitors). From this perspective ticks are thought to use serpins to evade host defenses during feeding. The cattle tick Rhipicephalus microplus encodes at least 24 serpins, of which RmS-3, RmS-6, and RmS-17 were previously identified in saliva of this tick. In this study, we screened inhibitor functions of these three saliva serpins against a panel of 16 proteases across the mammalian defense pathway. Our data confirm that Pichia pastoris-expressed rRmS-3, rRmS-6, and rRmS-17 are likely inhibitors of pro-inflammatory and pro-coagulant proteases. We show that rRmS-3 inhibited chymotrypsin and cathepsin G with stoichiometry of inhibition (SI) indices of 1.8 and 2.0, and pancreatic elastase with SI higher than 10. Likewise, rRmS-6 inhibited trypsin with SI of 2.6, chymotrypsin, factor Xa, factor XIa, and plasmin with SI higher than 10, while rRmS-17 inhibited trypsin, cathepsin G, chymotrypsin, plasmin, and factor XIa with SI of 1.6, 2.6, 2.7, 3.4, and 9.0, respectively. Additionally, we observed the formation of irreversible complexes between rRmS-3 and chymotrypsin, rRmS-6/rRmS-17 and trypsin, and rRmS-3/rRmS-17 and cathepsin G, which is consistent with typical mechanism of inhibitory serpins. In blood clotting assays, rRmS-17 delayed plasma clotting by 60 s in recalcification time assay, while rRmS-3 and rRmS-6 did not have any effect. Consistent with inhibitor function profiling data, 2.0 μM rRmS-3 and rRmS-17 inhibited cathepsin G-activated platelet aggregation in a dose-responsive manner by up to 96% and 95% respectively. Of significant interest, polyclonal antibodies blocked inhibitory functions of the three serpins. Also notable, antibodies to Amblyomma americanum, Ixodes scapularis, and Rhipicephalus sanguineus tick saliva proteins cross-reacted with the three R. microplus saliva serpins, suggesting the potential of these proteins as candidates for universal anti-tick vaccines.

[Retrospective study on bleeding and thromboembolic complications related to tooth extraction, in 93 patients usually treated by antithrombotic therapy]

INTRODUCTION

Tooth extraction for patients treated by AVK and/or platelet aggregation inhibitor is performed according to local habits rather than to a consensus. We had for objective to assess hemorrhagic and thromboembolic risks for patients for whom treatment with AVK and/or platelet aggregation inhibitor was modified before tooth extraction.

MATERIALS AND METHODS

Ninety-three patient files were examined retrospectively. The following data was collected: epidemiological data, ASA score, nature and changes of antithrombotic therapy, preoperative INR, number teeth extracted, postoperative complications (bleeding and thromboembolic events).

RESULTS

Thirty-seven patients were treated with oral anticoagulants, 41 by a platelet aggregation inhibitor, 10 by double platelet aggregation inhibitor therapy, and 5 by an AVK-platelet aggregation inhibitor combination. At D0, the mean INR was decreased to 1.4, 4 patients with high thromboembolic risk had received heparin relay treatment; the treatment was stopped for 9 of the 56 patients on monotherapy with antiplatelet therapy, 4 were switched from clopidogrel to lysine acetylate; clopidogrel was stopped for 7 patients under combination therapy. Seven hundred and twenty-six avulsions (mean 8.1 per patient) were performed, 41 patients presented with mild/moderate bleeding, easily resolved. A patient presented with delayed hemorrhage at D6 (AVK overdose). No thromboembolic complication was reported.

DISCUSSION

The modification of antithrombotic treatment, as for surgery at high risk of bleeding, seems to limit the risk of bleeding without increasing thromboembolic risk.