Downstream or upstream administration of P2Y12 receptor blockers in non-ST elevated acute coronary syndromes: study protocol for a randomized controlled trial

DUBIUS is a phase 4, prospective, double randomized, active control, parallel arm, multicenter adaptive clinical investigation in a population of NSTE-ACS patients with an indication to undergo initial invasive evaluation, to be conducted at approximately 40 hospitals in Italy, including both academic and non-academic centers. Patients must meet all eligibility criteria (Table 1), including the following: (1) an initial diagnosis of NSTE-ACS (unstable angina or non-ST elevated myocardial infarction), with an onset of symptoms during the previous 24 h and positive troponin-I or troponin-T; (2) an invasive strategy is chosen, meaning that the patient is expected to undergo coronary angiography within 72 h from hospital admission; (3) patient is able to start therapy with a new P2Y12 inhibitor (prasugrel or ticagrelor) or is on a maintenance dose of clopidogrel or ticlopidine and is able to switch to a new P2Y12 inhibitor (prasugrel or ticagrelor); (4) patient is ≥ 18 and < 85 years old. Diagnosis of NSTE-ACS refers to unstable angina or non-ST elevated myocardial infarction (NSTEMI) as previously defined [4]. Exclusion criteria include having contraindications for receiving ticagrelor or prasugrel (e.g., history of stroke or transient ischemic attack, high bleeding risk) and having received a loading dose of a thienopyridine (ticlopidine, clopidogrel, or prasugrel) or a maintenance dose of prasugrel or ticlopidine or ticagrelor within 7 days of entry into the study. An updated list of participating study sites is available online (https://​gise.​it/​studi/​gise).

In order to achieve an adequate participant enrolment to reach target sample size, the study will include high-volume sites for referral of NSTE-ACS patients. Participating centers are asked to screen each consecutive patient referred for NSTE-ACS for potential enrolment in the DUBIUS trial.

Investigators of each participating site will be cardiologists or cardiology fellows and will assess eligibility, obtain patient informed consent prior to performing any study procedures, enroll eligible patients, and assign patients to interventions. The informed consent form is reported in Additional file 2. All subjects enrolled will be randomly assigned in a parallel 1:1 fashion to downstream administration strategy of P2Y12 receptor blockers (prasugrel or ticagrelor) or to an upstream administration strategy (only ticagrelor) (Fig. 1). The randomization to the upstream or the downstream arm should occur as soon as possible after admission. The patients of the downstream arm, who will undergo PCI, will be further randomized in a 1:1 fashion to downstream prasugrel versus downstream ticagrelor at the time of PCI. The second randomization (prasugrel versus ticagrelor) will occur after coronary angiography and before the PCI procedure. The allocation sequence of patients into study groups will be computer-generated by a central system located at the coordinating center. Allocation sequence will be concealed to investigators. Investigators will obtain the randomization information of patients enrolled at their site by a dedicated online system (https://​redcap.​dctv.​unipd.​it). Enrolled subjects and investigators will not be blinded to study treatments, so unblinding will not occur. In order to avoid imbalances between groups with respect to age, all randomizations will be blocked by age > 75 years or ≤ 75 years. On the consent form, participants will be asked if they agree to use of their data should they choose to withdraw from the trial. Participants will also be asked for permission for the research team to share relevant data with people from the Universities taking part in the research or from regulatory authorities, where relevant. This trial does not involve collecting biological specimens for storage. A centralized online system will be used for randomization. Once randomized, the subjects are considered enrolled in the study and analyzed as the intent-to-treat (ITT) population.

Subjects randomized to the upstream strategy arm will receive a loading dose of ticagrelor (180 mg) at admission as soon as possible after randomization. Those in the upstream arm already receiving a chronic therapy with clopidogrel should switch to ticagrelor therapy, starting with a loading dose of 180 mg of ticagrelor (timing from last clopidogrel dose based on clinician’s judgment). Patients randomized to downstream strategy will not receive any loading dose of P2Y12 receptor blockers before coronary angiography. In both treatment arms, adjunctive aspirin will be administered after randomization (100–300 mg oral or i.v. bolus only in naïve patient; maintenance therapy with ≥ 75 mg daily in all patients) as per standard of care. Patients in the downstream arm already on chronic clopidogrel therapy before randomization will continue maintenance clopidogrel 75 mg daily until coronary angiography, but without receiving any loading dose. The timing of myocardial revascularization (PCI or CABG) in this trial will be based upon judgment of the treating physician. For patients requiring PCI, both ad hoc and deferred procedures are allowed. In the downstream arm, it is recommended to administer the P2Y12 inhibitor as soon as possible after the indication to PCI is formulated and before performing PCI. Moreover, in order to facilitate a complete platelet inhibition before PCI is performed, a deferred PCI (> 2 h from P2Y12 administration) may be preferred. Patients requiring PCI in the downstream arm will receive a loading dose of prasugrel 60 mg or ticagrelor 180 mg according to the second randomization. All subjects treated by PCI will be treated with dual antiplatelet therapy including a minimum of 75 mg of aspirin daily and ticagrelor 90 mg b.i.d. or 10 mg of prasugrel daily (according to randomization) for at least 12 months in line with guideline recommendations. In patients > 75 years of age or with a body weight < 60 kg assigned to receive downstream prasugrel, after a 60-mg loading dose, the daily maintenance dose of prasugrel will be 5 mg. After angiography, if the patient does not have an indication for percutaneous or surgical coronary revascularization, and the diagnosis of NSTE-ACS is confirmed, subjects will maintain (upstream arm) or start (downstream arm) DAPT with ticagrelor based on the benefit of ticagrelor [12], but not prasugrel [13], over clopidogrel in medically treated NSTE-ACS patients. If the initial diagnosis of NSTE-ACS is not confirmed or an alternative diagnosis (e.g., myocarditis, tako-tsubo syndrome) is made, the antiplatelet treatment regimen will be defined at the discretion of the treating physician. In patients who have an indication to undergo coronary artery bypass graft (CABG), antiplatelet therapy will be managed according to current ESC guidelines [3, 14]. In the upstream treatment arm, if ticagrelor is discontinued prior to CABG, resumption of a P2Y12 inhibitor should be considered as soon as considered safe. In the downstream arm, a P2Y12 inhibitor should be started after CABG before patient discharge. Patients who are medically managed as well as those undergoing CABG will be not part of the per-treatment evaluable population but will be part of the intention-to-treat population. Related to allowed or prohibited concomitant medications, the use of GPIIb/IIIa inhibitors prior to randomization is not permitted and is an exclusion criterion. After randomization, a GPIIb/IIIa inhibitor can be used according to local practice. Anticoagulant therapy should be started as per local standard of care as soon as diagnosis of NSTE-ACS is made. Anticoagulants may include unfractionated heparin (UFH), fondaparinux, enoxaparin, and—at the time of PCI—bivalirudin (dosing according to latest ESC guidelines) [3].

The primary outcome measure (NACE, net adverse cardiac events) is a composite of death from vascular causes (death from cardiovascular causes or cerebrovascular causes and any death without another known cause), non-fatal MI, or non-fatal ischemic stroke, and BARC type 3, 4, and 5 bleeding. The rationale for choosing this composite endpoint was to use a balanced estimate of the effect regarding irreversible organ damage, that is, MI, stroke, plus an estimate of life-threatening and fatal bleedings. Cardiovascular death includes death with a demonstrable CV cause, or any death that is not clearly attributable to a non-CV cause. To be considered a primary endpoint event, an MI must be distinct from the index event. Definitions of spontaneous, PCI-related, and CABG-related MI will be adjudicated based on the third universal definition of myocardial infarction [15]. Stroke is defined as a rapid onset of a new persistent, neurological deficit that lasts for more than 24 h (excluding hemorrhagic stroke). Bleeding includes major, life-threatening, or fatal events according to BARC type 3, 4, and 5 definitions (Table 2). Secondary outcome measures include death from any cause and stent thrombosis. Stent thrombosis is based on Academic Research Consortium definitions and comprises angiographic or pathological confirmation, as well as clinical determination of stent thrombosis [16]. Secondary safety endpoints include BARC type 2, 3, 4, and 5 bleeding; any TIMI major, life-threatening, and minor bleeding; CABG surgery-related TIMI major and minor bleeding; and non-CABG surgery-related TIMI major and minor bleeding [17, 18].

The primary hypothesis will be tested comparing study groups in terms of the 30-day incidence of the combined efficacy and safety primary endpoint (NACE). A list of safety and efficacy endpoints is reported in Table 3.

The primary powered hypotheses include (1) superiority of a downstream administration strategy for P2Y12 receptor blockers over the upstream administration and (2) non-inferiority of prasugrel versus ticagrelor in the PCI group of the downstream strategy arm. The study is powered based on the primary endpoint of incidence at 30 days of the combined primary endpoint. For the comparison of upstream and downstream arms, the intent-to-treat (ITT) population will be considered. The study will provide 80% power to establish the superiority of the downstream strategy on the upstream strategy relative to the primary composite endpoint. These calculations are based on the following assumptions: (1) 8% of patients in downstream arm and 11% of patients in the upstream arm (odds ratio = 1.4) having a primary endpoint event within 30 days from randomization, based on extrapolations of previous data. In particular, in patients with NSTE-ACS pretreated with ticagrelor, the 30-day incidence of a composite efficacy endpoint (comprising cardiovascular death, MI, stroke, TIA, or other arterial thrombotic event) was 6.95%, while the rate of major bleeding was 4.05% [19]. In patients with NSTE-ACS not pretreated with a P2Y12 inhibitor, the observed incidence of the composite efficacy endpoint at 30 days (cardiovascular death, MI, stroke) was 7.2%, while the incidence of non-CABG-related TIMI major bleeds was 0.6% and the incidence of all TIMI major bleeds (CABG-related or non-CABG-related) was 1.5% [8]; (2) the time-to-first event analysis based on a 2-sided log-rank test used at a 2-sided significance level (α) of .05 to assess superiority; (3) a dropout rate of about 10%.

In order to compensate for discrepancies between expected and observed incidence of the primary endpoint, the sample size has been computed using an adaptive approach in three study stages. After each stage, a sample size reassessment will be performed. After having reached the sample size foreseen for each of the three stages, an evaluation using a 95% repeated confidence interval will be used. If the value 0 will be contained in the interval, a sample size reassessment will be performed based on actually observed incidence rates of NACE. Otherwise, data will be passed to the Executive Steering Committee to decide to continue in randomizing patients for the other two analyses or to stop the study. The critical values and the test characteristics of the design were calculated using the Farrington and Manning method [20].

As a second target, non-inferiority of prasugrel versus ticagrelor in the PCI group of the downstream strategy will be considered. Analyses will be performed at the study completion, so no ad interim evaluations are assumed for this study group. Assuming that at least 80% of the patients will have an indication for PCI in the downstream group, based on the above calculations, a sample of about 1000 should be available for randomization in this group. The following assumptions were considered: (i) two-sided non-inferiority test for rejecting the hypothesis that prasugrel and ticagrelor will differ for more than 4% in terms of NACE, (ii) an overall confidence bounds in non-inferiority testing at 0.95 level (α = 0.025), (iii) an overall sample size of 1000 patients (500 prasugrel + 500 ticagrelor), and (iv) an anticipated incidence rate of 5% in downstream ticagrelor and 8.5% in downstream prasugrel and a true difference in incidence rates of 1% between treatment groups [1, 2, 8]. This approach combines the target clinically relevant maximal difference between treatments of 1% with previous information on a relevant distance in terms of effects between treatments (8.5% versus 5%) [21]. This design corresponds to the Palesch and Tilley “futility design” [22, 23], aimed at screening out-of-target therapeutic approaches, in particular in the cardiovascular field [23]. Power calculations have been made using the R-system [24] and gsDesign libraries [25]. For time-to-event variables, survival curves will be constructed using Kaplan-Meier estimates, and log-rank test results will be displayed for descriptive purposes only. Demographics, procedural, imaging, laboratory, exercise testing, quality of life, and diary related data that are not part of the list of endpoints will be displayed for descriptive purposes only.

All analyses will be based on available data with missing data excluded. Any unused or spurious data will be noted as appropriate in the final report. Analyses will be compared with a multiple imputation approach to detect potential important influences in the study design due to missing values.

Any major changes to the statistical plan described above will be documented in amendment to the clinical investigation plan. Less significant changes to the planned analyses will be documented in the final report.

The full protocol, the participant-level dataset, and the statistical code may be shared or made public for specific purposes or upon participant’s request with approval of the steering committee. The datasets analyzed during the current study are available from the corresponding author on reasonable request.

The assessment of clinical endpoints and adverse events will take place during hospital stay, at hospital discharge, at 30 ± 7 days (office visit), and at 12 months ± 30 days (office visit) (Fig. 2). Data collection forms are available in the e-CRF at https://​redcap.​dctv.​unipd.​it. e-CRF printout is reported in Additional file 3. Investigators at each eligible site will be preliminarily trained by the coordinating center in order to promote data quality related to both clinical data and clinical events. Clinical documentation of each patient experiencing adverse events will be kept at the enrolling sites and made available for the clinical events committee. Investigators at each site will be trained to collect and report any additional reported adverse events and unintended effects of trial interventions or trial conduct by inclusion in the e-CRF or telephone/e-mail contact with the coordinating center, as appropriate. Outcome data of participants who discontinue or deviate from intervention protocols will be collected in a similar manner to those with a satisfactory adherence to study protocol. The responsible person for pharmacovigilance will be available 24/24 h 7/7 days at nucleoricercacli​nica@aopd.​veneto.​it and eudra.​vigilance@aopd.​veneto.​it, telephone +390498218314/4439, mobile +393484720898, and fax +390498217490. Data collection forms will be available in the e-CRF at https://​redcap.​dctv.​unipd.​it. The e-CRF printout is available in the Trial Master File and in each center in the appropriate section of Investigator’s Site File.

Investigators are requested to adopt strategies to increase the compliance of patients to study protocol and study treatments. At follow-up visits, investigators will actively monitor the adherence to antiplatelet therapy by means of a dedicated questionnaire included in the e-CRF and, when possible, by direct count of drug tablet consumption. For patients not presenting to follow-up visits, investigators will implement strategies of active promotion of the completeness of follow-up including telephone contact, e-mail/letter contact, or any other suitable procedure, as appropriate.

At study completion, each participating subject will receive additional drug treatments or diagnostic investigations according to the treating physician. Subjects who eventually suffered harm from study participation will be cared by the treating physician(s) and may receive compensation upon request to trial sponsor by means of a study-specific insurance policy.

The following is the sponsor contact: Azienda Ospedaliera di Padova, UOC Cardiologia, Via Giustiniani 1, 35128, Padova, Italy. Phone number +390498211844, fax number +390498212309; e-mail giuseppe.​tarantini.​1@gmail.​com

Coordinating investigator (or designees) will monitor the study over its duration according a pre-specified monitoring plan. The study monitor will visit each site at appropriate intervals to review investigational data for accuracy and completeness and ensure compliance with the protocol. The study monitor may inspect all documents and required records that are maintained by the investigator/site, including medical records (office, clinic, or hospital) for the subjects in this study. The investigator/site will permit access to such records. Source documentation must be available to substantiate proper informed consent procedures, adherence to protocol procedures, adequate reporting and follow-up of adverse events, accuracy of data collected on case report forms, and device information. A monitoring visit sign-in log will be maintained at the site. The investigator and/or research coordinator will be available for monitoring visits. It is expected that the investigator will provide the study monitor with a suitable working environment for review of study-related documents. On-site monitoring for the coordinating center will be performed by the sponsor’s Clinical Research Office while remote monitoring for the remaining centers will be performed by the Department of Cardiac, Thoracic, and Vascular Sciences and Public Health of the University of Padova, by means of its Service for Clinical Trials and Biometrics.

According to ICH E6 (R2) GCP, the frequency of monitoring visits is determined by a risk assessment of the trial performed by the sponsor. The first monitoring visit following initiation of the site and trial commencement will take place within approximately 2 weeks after the inclusion of the first patient. Subsequent monitoring visits will take place every 12 months (for the coordinating center) or every 3 months (for the remaining centers). The interval for monitoring visits may be longer or shorter than stated above, depending on subject enrolment rate, quality issues, trial site compliance, or other trial site issues. Any significant deviation from the planned monitoring timelines will be explained and documented in the monitoring visit report and the monitoring plan amended if appropriate. If the site does not enroll any patients or enrolment has stopped, regular monitoring visits will not be scheduled. If there is an extended gap in trial activity, the monitor should ensure that site staff are appropriately trained when trial activities recommence.

Frequency and procedures for auditing trial conduct are described in the monitoring plan. The audit process is independent from both investigators and the sponsor.

In the event that an investigator is contacted by a regulatory agency in relation to this study, the investigator will notify the coordinating investigator (or designees) immediately. The investigator and research coordinator must be available to respond to reasonable requests and inspection queries made during the inspection process. The investigator must provide the sponsor with copies of all correspondence that may affect the review of the current study. The sponsor will provide any needed assistance in response to regulatory inspections.

Source documents are defined as original documents, data, and records. Regulations require that the investigator maintains source documents in the subject’s medical records, which confirm the data entered on the case report forms.

Data collection based on source-documented hospital and/or clinic chart reviews will be performed accurately on the e-CRFs by site personnel trained to the protocol and e-CRF completion. Coordinating investigator (or designees) will provide monitoring of e-CRF completion.

Data entry will be performed in a web-based electronic data capture system accessible by username and password provided to each site’s principal investigator or designees. Each subject enrolled in the study will be identified by a numeric code made of study site code and progressive enrolling code; a subject screening and enrolling form will be filed in each study site and stored in a restricted area in a locked cabinet. e-CRF data are stored in a secured server at University of Padua undergoing regular back-up two times per day. In order to promote data quality, range checks for data values have been implemented in e-CRF system; data quality is also routinely performed at fixed timepoint according to monitoring plan both by means of a centralized data quality monitoring system and by manual data quality activities in order to distribute data queries to investigators and collaborators in each study site. Subjects’ privacy will be granted according to EU GDPR. Data management procedures are described in a separate document (e-CRF manual).

The investigator/site will maintain all records pertaining to this study for 3 years following study completion or as otherwise instructed by the coordinating investigator (or designees) or per local regulations if longer.