DT-678 inhibits platelet activation with lower tendency for bleeding compared to existing P2Y12 antagonists

The first in-human study to evaluate the antiplatelet properties of the clopidogrel conjugate DT-678 in acute coronary syndrome patients and healthy volunteers

BACKGROUND AND PURPOSE

DT-678 is a novel antiplatelet prodrug, capable of releasing the antiplatelet active metabolite of clopidogrel (AM) upon exposure to glutathione. In this study, we investigated factors responsible for clopidogrel high on-treatment platelet reactivity (HTPR) in acute coronary syndrome (ACS) patients and evaluated the capacity of DT-678 to overcome HTPR.

EXPERIMENTAL APPROACH

A total of 300 consecutive ACS patients naive to P2Y12 receptor inhibitors were recruited and genotyped for CYP2C19 alleles. Blood samples were drawn before and after administration of 600-mg clopidogrel. Platelet reactivity index (PRI) and plasma AM concentrations were determined and grouped according to their CYP2C19 genotypes. DT-678 was applied ex vivo to whole blood samples to examine its inhibitory effects. To further examine the antiplatelet effectiveness of DT-678 in vivo, 20 healthy human subjects were recruited in a Phase I clinical trial, and each received a single dose of either 3-mg DT-678 or 75-mg clopidogrel. The pharmacokinetics and pharmacodynamics in different CYP2C19 genotype groups were compared.

KEY RESULTS

Statistical analyses revealed that CYP2C19 genotype, body mass index, hyperuricaemia, and baseline PRI were significantly associated with a higher risk of clopidogrel HTPR in ACS patients. The addition of DT-678 ex vivo decreased baseline PRI regardless of CYP2C19 genotypes, overcoming clopidogrel HTPR. This observation was further confirmed in healthy volunteers receiving 3 mg of DT-678.

CONCLUSION AND IMPLICATIONS

These results suggest that DT-678 effectively overcomes clopidogrel HTPR resulting from genetic and/or clinical factors in Chinese ACS patients, demonstrating its potential to improve antiplatelet therapy.

Evaluation of the Efficacy and Safety of Antiplatelet Therapeutics in Rabbits

Hemostasis is a multifactorial process that involves vasoconstriction of blood vessels, activation of the coagulation cascade, and platelet aggregation. Inappropriate activation of hemostatic processes can result in thrombosis and tissue ischemia. In patients at risk for thrombotic events, antiplatelet therapeutic agents inhibit platelet activation, thereby reducing the incidence of pathologic clot formation. Platelets are activated by several endogenous chemical mediators, including adenosine diphosphate, thrombin, and thromboxane. These activation pathways serve as attractive drug targets. The protocols described in this article are designed to evaluate the preclinical efficacy and safety of novel antiplatelet therapeutics in rabbits. Here, we provide two protocols for blood collection, two for determining platelet activation, and one for assessing bleeding safety. Together, these protocols can be used to characterize the efficacy and safety of antiplatelet agents for hemostasis. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Blood collection via the central ear artery Alternative Protocol 1: Blood collection via the jugular vein Basic Protocol 2: Platelet aggregation assessment via light transmission aggregometry Alternative Protocol 2: Platelet activation assessment via flow cytometry Basic Protocol 3: Determination of tongue bleeding time.

Pleiotropic effects of clopidogrel

Clopidogrel is a widely prescribed prodrug with anti-thrombotic activity through irreversible inhibition of the P2Y₁₂ receptor on platelets. It is FDA-approved for the clinical management of thrombotic diseases like unstable angina, myocardial infarction, stroke, and during percutaneous coronary interventions. Hepatic clopidogrel metabolism generates several distinct metabolites. Only one of these metabolites is responsible for inhibiting the platelet P2Y₁₂ receptor. Importantly, various non-hemostatic effects of clopidogrel therapy have been described. These non-hemostatic effects are perhaps unsurprising, as P2Y₁₂ receptor expression has been reported in multiple tissues, including osteoblasts, leukocytes, as well as vascular endothelium and smooth muscle. While the "inactive" metabolites have been commonly thought to be biologically inert, recent findings have uncovered P2Y₁₂ receptor-independent effects of clopidogrel treatment that may be mediated by understudied metabolites. In this review, we summarize both the P2Y₁₂ receptor-mediated and non-P2Y₁₂ receptor-mediated effects of clopidogrel and its metabolites in various tissues.

Clopidogrel treatment inhibits P2Y2-Mediated constriction in the rabbit middle cerebral artery

Clopidogrel is an effective purinergic 2Y12 receptor (P2Y12) antagonist used to prevent arterial thrombosis, but its use is associated with adverse bleeding. Clinical studies have demonstrated that clopidogrel users have an increased risk of cerebral microbleeds and intracerebral hemorrhage. Our previous studies suggest that non-platelet mechanisms mediate these adverse bleeding events; we hypothesize that clopidogrel or one of its metabolites interacts with blood vessels directly to cause bleeding. New Zealand white rabbits (1.9-2.7 kg) were treated orally with vehicle or clopidogrel (3 or 10 mg/kg) for three days. On the fourth day, the rabbits were anesthetized for blood collection and then euthanized. The brain was collected, and the middle cerebral arteries were isolated. We used light transmission aggregometry and pressure myography to elucidate the mechanisms of the off-target effects associated with clopidogrel treatment. We confirmed that inhibition of P2Y12 activation by clopidogrel inhibited ADP-induced platelet aggregation but had no impact on P2Y12-independent arachidonic acid- or collagen-induced platelet aggregation. Analysis of middle cerebral arteries from clopidogrel treated rabbits showed that clopidogrel did not affect P2Y4, P2Y6, and P2Y14 receptor-mediated contraction but attenuated the contractile response after P2Y2 receptor activation. Further analysis determined P2Y2-mediated constriction was endothelium-dependent. Vasoconstriction is a primary component of hemostasis, and impaired vasoconstriction can prolong bleeding. These results suggest clopidogrel inhibits the endothelial P2Y2 receptor in the middle cerebral artery, which provides a mechanistic explanation for the adverse cerebral bleeding associated with the drug.

Clopidogrel Resistance in a Murine Model of Diet-Induced Obesity Is Mediated by the Interleukin-1 Receptor and Overcome With DT-678

OBJECTIVE

Clopidogrel is a commonly used P2Y₁₂ inhibitor to treat and prevent arterial thrombotic events. Clopidogrel is a prodrug that requires bioactivation by CYP (cytochrome P450) enzymes to exert antiplatelet activity. Diabetes mellitus is associated with an increased risk of ischemic events, and impaired ability to generate the active metabolite (AM) from clopidogrel. The objective of this study is to identify the mechanism of clopidogrel resistance in a murine model of diet-induced obesity (DIO). Approach and Results: C57BL/6J mice and IL-1R^-/- mice were given high-fat diet for 10 weeks to generate a murine model of diet-induced obesity. Platelet aggregation and carotid arterial thrombosis were assessed in response to clopidogrel treatment. Wild-type DIO mice exhibited resistance to antiplatelet and antithrombotic effects of clopidogrel that was associated with reduced hepatic expression of CYP genes and reduced generation of the AM. IL (Interleukin)-1 receptor-deficient DIO (IL1R^-/- DIO) mice showed no resistance to clopidogrel. Lack of resistance was accompanied by increased exposure of the clopidogrel AM. This resistance was also absent when wild-type DIO mice were treated with the conjugate of the clopidogrel AM, DT-678.

CONCLUSIONS

These findings indicate that antiplatelet effects of clopidogrel may be impaired in the setting of diabetes mellitus due to reduced prodrug bioactivation related to IL-1 receptor signaling. Therapeutic targeting of P2Y₁₂ in patients with diabetes mellitus using the conjugate of clopidogrel AM may lead to improved outcomes.