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Challenging the FDA Black Box Warning for High Aspirin Dose with Ticagrelor in Patients with Diabetes James J

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Challenging the FDA Black Box Warning for High Aspirin Dose with Ticagrelor in Patients with Diabetes James J PERSPECTIVES IN DIABETES Challenging the FDA Black Box Warning for High Aspirin Dose With Ticagrelor in Patients With Diabetes James J. DiNicolantonio and Victor L. Serebruany – Ticagrelor, a novel reversible antiplatelet agent, has a Food and ASA 300 325 mg (53.6%) in the U.S. compared with the Drug Administration (FDA) black box warning to avoid mainte- rest of the world (1.7%) was the only factor to explain nance doses of aspirin (ASA) .100 mg/daily. This restriction is (out of 37 variables explored) the regional interaction based on the hypothesis that ASA doses .100 mg somehow de- that ticagrelor was less effective and potentially more creased ticagrelor’s benefit in the Platelet Inhibition and Patient harmful than clopidogrel (2). However, this interaction Outcomes (PLATO) U.S. cohort. However, these data are highly was not significant, is highly postrandomized, comes postrandomized, come from a very small subgroup in PLATO from a very small subgroup of PLATO, and makes no (57% of patients in the U.S. site), and make no biological sense. biological sense (3). Moreover, the ticagrelor-ASA interaction was not significant by any multivariate Cox regression analyses. The Complete Re- sponse Review for ticagrelor indicates that for U.S. PLATO patients, an ASA dose .300 mg was not a significant interaction TICAGRELOR-ASA HYPOTHESIS for vascular outcomes. In the ticagrelor-ASA .300 mg cohort, all- The claimed ticagrelor-ASA interaction states that ticagrelor cause and vascular mortality were not significantly increased fi – P plus low-dose ASA is bene cial, whereas increasing doses (hazard ratio [HR] 1.27 [95% CI 0.84 1.93], = 0.262 and 1.39 of ASA in combination with ticagrelor produces adverse [0.87–2.2], P = 0.170), respectively. Furthermore, for major ad- verse cardiovascular events (MACEs), 30-day all-cause mortality, effects. Ticagrelor, having nearly complete P2Y12 platelet and 30-day vascular mortality, the strongest interaction is the receptor blockade, does not exhibit the added anti- diabetes-ASA interaction. That is, patients who had diabetes aggregatory benefit derived from ASA, in contrast to what had significantly fewer MACEs through study end (0.49 [0.34– is seen with clopidogrel. Moreover, it is postulated that 0.63], P , 0.0001), significantly less 30-day all-cause mortality the incomplete and variable P2Y12 blockade seen with (0.33 [0.20–0.56], P , 0.0001), and significantly less 30-day vas- clopidogrel derives more benefitfromASAwithless cular mortality (0.35 [0.22–0.55], P , 0.0001), respectively, when display of adverse effects. This hypothesis distinguishes given high-dose (300–325 mg) ASA, regardless of treatment (clo- between ASA-mediated effects in platelets versus tar- pidogrel or ticagrelor) assignment. The black box warning for the geting endothelial cells in the vessel wall; that is, in use of maintenance ASA doses .100 mg with ticagrelor is inap- ’ propriate for patients with diabetes and not evidence based. platelets, ASA s inhibition of cyclooxygenase (COX)-1 Diabetes 62:669–671, 2013 causes a decrease in thromboxane A2 formation, inhib- iting platelet aggregation. However, at higher doses, ASA also blocks the COX-2– mediated production of the va- sodilator prostacyclin, causing an increase in vascular icagrelor was compared with clopidogrel in the resistance. PLATO trial, which randomized 18,624 patients The PLATO sponsor conducted a study in anesthetized with acute coronary syndrome (ACS) to either dogs in an attempt to show vascular effects secondary to Tticagrelor (180 mg loading dose plus 90 mg twice inhibition of prostacyclin production. The study showed daily maintenance dose) plus ASA versus clopidogrel no difference between ticagrelor and ASA compared (300–600mgloadingdoseplus75mgoncedailymain- with clopidogrel and ASA combination or ASA alone tenance dose) plus ASA (1). Ticagrelor lead to a signifi- when absolute blood flow was examined. The FDA cant reduction in the primary end point (a composite of records indicate that “there is no clear explanation why death from vascular causes, myocardial infarction, or ASA’s proposed inhibition of endothelial prostacyclin is stroke) compared with clopidogrel (9.8 vs. 11.7%; 95% CI able to outweigh ticagrelor’s, but not clopidogrel’s 0.77–0.92, P , 0.001, respectively). Importantly, the benefit beneficial effects of thromboxane-A2 inhibition, platelet of ticagrelor was driven equally by the reduction of vascular inhibition, and interactions with phosphodiesterase death (P , 0.001) and myocardial infarction (P , 0.005), isoforms” (3). It is entirely unclear why ASA adds to with 89 events favoring ticagrelor each, but not stroke (P = the lower platelet inhibition produced by clopidogrel 0.22), with 19 fewer events in the clopidogrel arm (1). but not to the greater platelet inhibition produced by A post hoc secondary analysis from the PLATO trial ticagrelor and why ASA’s ability at higher dosages to was undertaken to suggest that the increased use of block COX-2–mediated production of the vasodilator prostacyclin produces vasoconstriction would only mani- fest in ticagrelor patients. In short, there is no clear expla- nation of why the reduced prostacyclin vasoconstriction From Wegman’s Pharmacy, Ithaca, New York. Corresponding author: James J. DiNicolantonio, [email protected]. should be relevant selectively and exclusively only to Received 6 June 2012 and accepted 8 July 2012. ticagrelor. The other major weakness of this hypothesis is DOI: 10.2337/db12-0746 that the platelet aggregation assay results aren’t consistent Ó 2013 by the American Diabetes Association. Readers may use this article as with the clinical bleeding rates in PLATO, for which higher long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by ASA dosage is associated with more bleeding and likely -nc-nd/3.0/ for details. a more additive effect upon bleeding with ticagrelor than See accompanying commentary, p. 709. with clopidogrel (3). diabetes.diabetesjournals.org DIABETES, VOL. 62, MARCH 2013 669 ASA AND TICAGRELOR IN PATIENTS WITH DIABETES TICAGRELOR-ASA INTERACTION IS NOT SIGNIFICANT IN to consider and analyze the effects of before choosing one, PLATO SHORT-TERM RESULTS BUT OTHER it should not be surprising that one, or more, associations INTERACTIONS, INCLUDING DIABETES, ARE may be “significant.” Importantly, the definition of ASA The FDA Complete Response Review states that the most dosage is completely post hoc and derived after the study striking PLATO result was the reported long-term mortal- was unblinded and analyzed. Besides the definition not ity benefit of ticagrelor. PLATO provides much less sub- being obvious, there are problems with the PLATO stantial evidence of short-term benefits and beneficial determinations of ASA dosage. The FDA report indicates effects on thrombotic events. This combination of results that some drugs (carbasalate [a calcium salt of acetyl- is inconsistent with those of all earlier platelet inhibitor salicylate used in Europe], anoprin [miscoded to chlor- ACS trials, which have shown strong short-term benefits phenamine], and “inj loparin” [enoxaparin]) had been and smaller or no later benefits particularly regarding miscoded to ASA (3). mortality. The ticagrelor-ASA interaction is not significant Finally, there is a converse problem with handling for the short-term results and not significant for mortality “missing” values. In PLATO, sites recorded concomitant results regardless whether short- or long-term. The short- drugs, including ASA, if the patient received the drug. term results and mortality results demonstrate that three There was no specific place to record that a drug was not other interactions are more important and creditable than given. Moreover, while examining the case report forms of the ticagrelor-ASA interaction. These interactions are the patients without ASA records, there was not infrequently following: a statement recorded justifying why ASA was not given. These patients also had higher baseline rates of histories 1) Patients with diabetes appear to benefit from higher of gastrointestinal bleeding and peptic ulcer disease (3). ASA dosage regardless of treatment arm. 2) Ticagrelor interacts favorably with statins—or inappro- CONCLUSIONS priate restriction of statin dosages was detrimental to The aforementioned data clearly indicate that it is in- clopidogrel patients in PLATO. 3 appropriate to follow a black box warning for ASA dosages ) Ticagrelor patients undergoing early percutaneous cor- .100 mg with ticagrelor in patients with diabetes. A more onary intervention fare worse than clopidogrel patients. plausible argument is that high-dose ASA improves clopi- dogrel benefit and may partially explain the disadvantage The FDA transcript summarizes that when applying Cox with ticagrelor versus clopidogrel in the U.S. Patients regressions analyses the interaction term for ticagrelor and – fi assigned to high-dose ASA (300 325 mg) in the random- region is insigni cant in all regressions. For short-term ized Clopidogrel Optimal Loading Dose Usage to Reduce results there is no major U.S. versus rest of the world Recurrent Events/Optimal Antiplatelet Strategy for Inter- discrepancy that requires explanation. The interaction fi fi ventions (CURRENT-OASIS 7) trial had a signi cant re- term for ticagrelor and ASA dosage is insigni cant in all duction in recurrent ischemia (0.3 vs. 0.5%, P = 0.02) and regressions. The short-term results do not support worse all-cause mortality (2.2 vs. 2.5%, P = 0.1 [just missing outcomes with higher ASA dosage in ticagrelor patients statistical significance]) compared with low-dose (75–100 alone. mg) ASA (4). Although high-dose ASA increased minor bleeds (5.0 vs. 4.4%, P =0.04),itdidnotsignificantly increase major bleeding events. Thus, randomized evi- TICAGRELOR-ASA INTERACTION IS SIGNIFICANT FOR dence shows that high-dose ASA in the U.S. cohort SPONSOR’S PRIMARY END POINT BUT A SPURIOUS would most likely have reduced mortality in the clopi- CORRELATION CANNOT BE RULED OUT dogrel cohort rather than increased mortality in the The Complete Response Review states that the proposed ticagrelor cohort.
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