STOP-DAPT 2 ACS: 1 month DAPT followed by clopidogrel monotherapy does not quite cut it when it comes to ACS

Key Points:

• The original STOP-DAPT trial randomized patients to receive either 12 months of dual antiplatelet therapy after percutaneous coronary intervention or one month of dual antiplatelet therapy followed by clopidogrel monotherapy, and found significantly less cardiovascular and bleeding events in the shorter DAPT group.
• As only 38% of the participants of the original STOP-DAPT 2 trial had acute coronary syndrome (ACS), STOP-DAPT 2 ACS was designed to assess the outcomes of a shorter DAPT duration in patients with ACS.
• After pooling patients from STOP-DAPT 2 and STOP-DAPT 2 ACS, one month of DAPT failed to meet noninferiority when compared to 12 months for a composite outcome of cardiovascular and bleeding events.
• Participants who received one month of DAPT had a trend toward higher cardiovascular events yet lower bleeding events, as would be expected.

Given the abundance of data surrounding shorter durations of dual antiplatelet therapy (DAPT) following percutaneous coronary intervention, yet another trial attempted to answer whether one month of DAPT is sufficient and safe in patients with acute coronary syndrome (ACS). However unlike its predecessor, STOP-DAPT 2, in which all-comers receiving one month of dual antiplatelet therapy followed by clopidogrel monotherapy had improved cardiovascular and bleeding outcomes, STOP-DAPT 2 failed to meet noninferiority when accounting for more patients with ACS.

The results of the trial were presented in a Hot Line presentation at the 2021 European Society of Cardiology Conference today, by primary investigator Dr. Hirotoshi Watanabe. After receiving percutaneous coronary intervention (PCI) for ACS using a durable polymer Cobalt chromium everolimus eluting stent (Xience, Abbott), participants were randomized in a 1:1 fashion to receive one month of aspirin and a P2Y12 inhibitor followed by clopidogrel monotherapy or twelve months of aspirin and clopidogrel in total.  Of note, patients on oral anticoagulation, prior intracranial hemorrhage and in-hospital complications from the PCI were excluded.  In total 3008 participants were enrolled into the trial, and combined with the 1161 participants of the original STOP-DAPT 2 trial, which had and identical study protocol.

Participants were mostly men (79%), with a mean age of 67 years. A majority of the ACS in either arm was ST segment elevation myocardial infarction (MI), and 30% of participants in either arm had diabetes. Almost all (>97%) of the stents were placed with IVUS or OCT guidance. For the primary composite endpoint of CV death, MI, stroke, definite stent thrombosis, or major or minor bleeding, the shorter DAPT group was found to have higher event rates (3.2% vs, 2.8% [HR 1.15; 95% CI 0.80-1.62]). The MI rate in the short DAPT group was higher, (1.59% vs 0.85%, HR 1.91; 95% CI 1.06-3.44) and, as expected, the bleeding rate was lower (0.54% vs 1.17%, HR 0.46; 95% CI: 0.23-0.94).

In his presentation, Dr. Watanabe concluded “One-month DAPT and subsequent clopidogrel monotherapy failed to achieve noninferiority for net clinical benefit compared with standard 12-month DAPT after ACS. There was a trend toward an increase in cardiovascular events despite a reduction in major bleeding events.”

The panelists then discussed the differences between this trial and MASTER-DAPT, which inconclusively showed safety in a shorter duration of DAPT earlier in this conference. Dr. Kurt Huber (Vienna) noted that MASTER DAPT did not exclude patients on oral anticoagulation, used a resorbable polymer stent (Terumo Ultimaster) and was primarily done in high bleeding risk patients. The panelists ultimately reiterated that the current ESC guidelines recommend 1 year of dual antiplatelet therapy for all patients (Class 1A) with clopidogrel reserved as monotherapy only in patients who cannot tolerate prasugrel or ticagrelor (Class 1C).