Ticagrelor resistance: a case series and algorithm for management of non-responders

Dual Antiplatelet Non-Responder: Resistance to Clopidogrel and Ticagrelor

Background

Dual antiplatelet therapy is often required for neurointerventional procedures, especially when a stent or flow diverter is placed in the cervical and intracranial vessels. Patients are usually started on aspirin and clopidogrel given the simplicity of the once daily regimen with reasonable cost. Unfortunately, about a third of patients do not show the desired antiplatelet response to clopidogrel and another agent needs to be introduced. Ticagrelor is a potent antiplatelet medication that has a favorable pharmacological profile and has emerged as a reliable alternative to clopidogrel in recent years. Despite ticagrelor non-responders being rare, they do exist, and identification of these patients is important.

Results

A 74-year-old female was incidentally found to harbor a right posterior communicating aneurysm which was successfully treated electively with stent-assisted coiling. Platelet inhibition testing revealed non-responsiveness to Clopidogrel. Ticagrelor was initiated but the patient's platelet reactivity unit remained in the normal range. Management algorithms to maximize a patient's ticagrelor response by facilitating enteral absorption were applied but no platelet inhibition was achieved. The patient was eventually identified as a true ticagrelor non-responder.

Conclusion

Resistance to antiplatelet medication can result in devastating complications with permanent neurological deficits. Ticagrelor non-responders are rare but do exist. Platelet inhibition testing should be part of the preprocedural workup for neurointerventions.

Ticagrelor Versus Clopidogrel in Endovascular Therapy for Cerebral Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND

Antiplatelet therapy is pivotal in endovascular treatment for intracranial aneurysms. However, there is a lack of studies comparing ticagrelor to clopidogrel in patients with aneurysms undergoing endovascular therapy. Additionally, the existing literature lacks adequate sample size, significant subgrouping, and follow-up, making our study important to cover these gaps.

METHODS

We searched 5 databases to collect all relevant studies. Categorical outcomes were pooled as relative risk (R.R.) with a 95% confidence interval (CI). In the single-arm meta-analysis, outcomes were pooled as proportions and their corresponding 95% CI.

RESULTS

This comprehensive analysis of 18 studies involving 2,427 patients. For thromboembolic events, the pooled (R.R.) did not show significant differences, whether considering overall events. A similar pattern was observed for thromboembolic events stratified by aneurysmal rupture status, with no significant differences in overall events. Hemorrhagic events did not also exhibit significant differences in previously mentioned stratifications. Furthermore, there were no substantial differences in death and mRS (0-2) on discharge between Ticagrelor and Clopidogrel. Single-arm meta-analyses for Ticagrelor demonstrated low rates of thromboembolic events, hemorrhage, death, and favorable mRS scores, with associated confidence intervals (CIs). Main line of endovascular treatment did not significantly affect either thromboembolic or hemorrhagic outcomes with Ticagrelor and Clopidogrel.

CONCLUSIONS

We found no significant differences in key outcomes like thromboembolic events, hemorrhagic events, mortality rates, and favorable mRS (0-2) upon discharge in the studied patients between Ticagrelor and Clopidogrel. Moreover, the single-arm meta-analysis for Ticagrelor revealed low rates of thromboembolic events, hemorrhage, mortality, and high rates of favorable mRS scores.

Efficacy and Safety Outcomes for Acute Ischemic Stroke Patients Treated with Intravenous Infusion of Tirofiban After Emergent Carotid Artery Stenting

INTRODUCTION

Emergent stenting of the extracranial internal carotid artery (ICA) in stroke patients requires antiplatelet therapy to prevent in-stent thrombosis with a higher risk of intracranial haemorrhage.

AIM OF THE STUDY

Assess the efficacy and safety of emergent carotid stenting with intravenous tirofiban in acute ischemic stroke patients.

METHODS

Primary endpoint: symptomatic hemorrhage. Secondary endpoints: 90-day functional outcome and mortality.

RESULTS

Of the 62 patients, 21 (34%) received tirofiban as a single antiplatelet, and 41 (66%) received combined therapy. Premedication with anticoagulants and antiplatelets was significantly more frequent in the tirofiban-only group. The rate of symptomatic haemorrhage was significantly lower in the tirofiban-only group than in the combined group (4.8% vs. 27%, p = 0.046). The patients with tirofiban alone had a significantly better functional outcome at day 90 than the combined group (52% vs. 24%, p = 0.028). Mortality was equal (24%) in both groups. Pre-interventional NIHSS score (p = 0.003), significant blood pressure fluctuations (p = 0.012), tandem occlusion (p = 0.023), and thrombolysis (p = 0.044) showed relevant influence on the rate of symptomatic hemorrhage in the entire patient cohort.

CONCLUSIONS

A single antiplatelet therapy with tirofiban regardless of the premedication may improve the functional outcome in patients with stroke due to acute extracranial carotid lesion and emergent carotid stenting with lower rates of serious intracranial haemorrhage. For patients with high pre-interventional NIHSS score, tandem occlusion and after pre-interventional thrombolysis, caution is advised. Additionally, strict blood pressure monitoring should be conducted during the first 72 h after intervention.

Propensity-score-matched analysis of dual antiplatelet treatment and alternative antiplatelet regimens after transcarotid revascularizations

OBJECTIVE

Dual antiplatelet therapy (DAPT) continues to be the preferred medication regimen after the placement of a carotid stent using the transcarotid revascularization (TCAR) technique despite a dearth of quality data. Therefore, this investigation was performed to define the risks associated with antiplatelet choice.

METHODS

We queried all patients who underwent TCAR captured by the Vascular Quality Initiative from September 2016 to June 2022, to determine the association between antiplatelet choice and outcomes. Patients maintained on DAPT were compared with those receiving alternative regimens consisting of single antiplatelet, anticoagulation, or a combination of the two. A 1:1 propensity-score match was performed with respect to baseline comorbidities, functional status, anatomic/physiologic risk, medications, and intraoperative characteristics. In-hospital and 1-year outcomes were compared between the groups.

RESULTS

During the study period, 29,802 procedures were included in our study population, with 24,651 (82.7%) receiving DAPT and 5151 (17.3%) receiving an alternative antiplatelet regimen. A propensity-score match with respect to 29 variables generated 4876 unique pairs. Compared with patients on DAPT, in-hospital ipsilateral stroke was significantly higher in patients receiving alternative antiplatelet regimens (1.7% vs 1.1%, odds ratio [95% confidence interval]: 1.54 [1.10-2.16], P = .01), whereas no statistically significant difference was noted with respect to mortality (0.6% vs 0.5%, 1.35 [0.72-2.54], P = .35). A composite of stroke/death was also more likely in patients receiving an alternative regimen (2.4% vs 1.7%, 1.47 [1.12-1.93], P = .01). Immediate stent thrombosis (2.75 [1.16-6.51]) and a nonsignificant trend toward increased return to the operating room were more common in the alternative patients. Conversely, the incidence of perioperative myocardial infarction was lower in the alternative regimen group (0.4% vs 0.7%, 0.53 [0.31-0.90], P = .02). At 1 year after the procedure, we observed an increased risk of mortality (hazard ratio [95% confidence interval]: 1.34 [1.11-1.63], P < .01) but not stroke (0.52 [0.27-0.99], P = .06) in patients treated with an alternative medication regimen.

CONCLUSIONS

This propensity-score-matched analysis demonstrates an increased risk of in-hospital stroke and 1-year mortality after TCAR in patients treated with an alternative medication regimen instead of DAPT. Further studies are needed to elucidate the drivers of DAPT failure in patients undergoing TCAR to improve outcomes for carotid stenting patients.

Ticagrelor Resistance in Cardiovascular Disease and Ischemic Stroke

Ticagrelor, acting as a reversible platelet aggregation inhibitor of P2Y12 receptors (P2Y12R), is regarded as one of the first-line antiplatelet drugs for acute cardiovascular diseases. Though the probability of ticagrelor resistance is much lower than that of clopidogrel, there have been recent reports of ticagrelor resistance. In this review, we summarized the clinical application of ticagrelor and then presented the criteria and current status of ticagrelor resistance. We further discussed the potential mechanisms for ticagrelor resistance in terms of drug absorption, metabolism, and receptor action. In conclusion, the incidences of ticagrelor resistance fluctuated between 0 and 20%, and possible mechanisms mainly arose from its absorption and receptor action. Specifically, a variety of factors, such as the drug form of ticagrelor, gut microecology, and the expression and function of P-glycoprotein (P-gp) and P2Y12R, have been shown to be associated with ticagrelor resistance. The exact mechanisms of ticagrelor resistance warrant further exploration, which may contribute to the diagnosis and treatment of ticagrelor resistance.

Effect of CYP4F2 Polymorphisms on Ticagrelor Pharmacokinetics in Healthy Chinese Volunteers

Background: Ticagrelor belongs to a new class of P2Y₁₂ receptor inhibitor that has been widely used for antiplatelet therapy. This study aimed to explore the effect of single nucleotide polymorphisms (SNPs) in metabolic enzymes, transporters, and other relevant variants on the pharmacokinetics (PK) of ticagrelor and its active metabolite, AR-C124910XX.

Methods: The study population comprised 68 healthy Chinese volunteers who were enrolled in a ticagrelor bioequivalence clinical trial. The PK profile of ticagrelor was evaluated after orally administering a single 90-mg dose of ticagrelor in tablet form. The plasma concentrations of ticagrelor and AR-C124910XX were determined through liquid chromatography–tandem mass spectrometry. Plasma DNA samples were used to explore the effect of gene polymorphisms on the PK of ticagrelor and AR-C124910XX with whole-exome sequencing.

Results: Female participants had a higher maximum plasma concentration/weight ratio (C_max/W; p < 0.001) and a shorter half-life (T_1/2; p < 0.05) for ticagrelor than their male counterparts. In addition, a higher area under the curve/weight ratio (AUC/W; p < 0.001), and longer T_1/2 (p < 0.001) and time to reach the maximum plasma concentration (T_max; p < 0.001), as well as a lower apparent drug clearance (CL/F; p < 0.001), were observed among healthy volunteers in the fed trial compared to those enrolled in the fasting trial. For AR-C124910XX, higher C_max/W (p < 0.001) and AUC/W (p < 0.001) but lower CL/F (p < 0.001) and apparent volume of distribution (V_d/F; p < 0.001) were observed among female participants. Healthy volunteers enrolled in the fasting trial exhibited higher C_max/W (p < 0.001) and AUC/W (p < 0.01), shorter T_max (p < 0.001), and lower CL/F (p < 0.001) and V_d/F (p < 0.001) than those enrolled in the fed trial. Upon confirmation through multivariate analysis, the CYP4F2 rs2074900 A/A carriers were associated with higher C_max/W and AUC/W and lower CL/F and V_d/F than the CYP4F2 rs2074900 A/G and G/G carriers.

Conclusion: This study is the first to show that the CYP4F2 rs2074900 SNP had a remarkable effect on ticagrelor PK, which is significant since it adds to the limited pharmacogenetic information on ticagrelor.