TAILOR-PCI: Clopidogrel Genotyping Trial Narrowly Misses Endpoint

Sue Hughes  

March 28, 2020

The largest trial to date investigating the clinical utility of using genetic testing to detect clopidogrel loss-of-function genotype to guide antiplatelet therapy in patients undergoing percutaneous coronary intervention (PCI) missed its primary endpoint of a 50% reduction in cardiovascular events at 1 year.

However, the TAILOR-PCI trial did show a 34% reduction in such events at 1 year, as well as a statistically significant 40% reduction in the total number of events per patient receiving genetically guided treatment compared with patients who received standard treatment.

In addition, a post hoc analysis found a significant 79% reduction in the rate of adverse events in the first 3 months of treatment among patients who received genetically guided therapy compared with those who did not.

The study was presented March 28 during the "virtual" American College of Cardiology 2020 Scientific Session (ACC.20)/World Congress of Cardiology.

"Although these results fell short of the effect size that we predicted, they nevertheless provide a signal that offers support for the benefit of genetically guided therapy, with approximately one-third fewer adverse events in the patients who received genetically guided treatment compared with those who did not," concluded Naveen L. Pereira, MD, professor of medicine at the Mayo Clinic in Rochester, Minnesota, and co-principal investigator of the study.

Pereira said the post hoc analysis of the first 3 months of treatment was particularly interesting. "This period immediately after PCI is when patients are at the highest risk for adverse events. We now know that antiplatelet drug therapy is critical during the first 3 months after PCI. Our findings suggest that the lion's share of the benefit of genetically guided therapy may occur during this high-risk period," he noted.  

However, he added, "Because this wasn't a preplanned analysis, we can't draw firm conclusions from it, but it merits further study."

Asked during an ACC virtual press conference how these results may influence clinical practice, Pereira said he hopes it changes practice toward genotyping. 

"We set a very high standard in trying to achieve a 50% reduction in events, but we did see a 34% reduction. I think the probability of the results being true is very high," he said. "I hope people pay attention to that. I'm not sure what the guidelines will do, but I believe if clopidogrel genetic information is made available to the physician, not changing therapy in a patient who has the loss-of-function gene will now be very difficult."

Discussant of the trial, Roxana Mehran, MD, Mount Sinai Hospital, New York City, said she thought the results were good enough clinically to justify using genotyping to guide therapy.

"The trial showed an absolute 1.8% reduction and a relative 34% reduction in cardiovascular events, which did not quite meet the P value for significance, and they are supported by a significant reduction in multiple events, and a large difference at 3 months, although these are not primary analyses. So, for me this trial has shown that tailoring antiplatelet therapy by genetic testing is beneficial," she said.  

Another outside commentator, Patrick O'Gara, MD, Brigham and Women's Hospital, Boston, Massachusetts, described TAILOR-PCI as a "terrific study."

"Together with the study presented last year showing genotype-guided clopidogrel treatment was noninferior to ticagrelor/prasugrel in STEMI [non-ST-segment elevation myocardial infarction] patients, it chips away at the biologic appropriateness of targeting therapies based on genetic risk," he said.

"I would hate people to focus on the fact the primary endpoint was missed by one hundredth of a percentage point but hope they would rather consider the bigger picture of making this genotype test more available and accessible to inform clinical decision making," O'Gara added. "It just makes too much sense to ignore this potential."

The TAILOR-PCI trial enrolled 5302 patients from 40 centers in the United States, Canada, Mexico, and South Korea who had undergone PCI with stenting. They were randomly assigned to genetic testing for the clopidogrel loss-of-function variant or a group that received standard treatment (clopidogrel) without genetic testing.

In the genetic testing group, 35% of patients were found to have the clopidogrel loss-of-function variant and were therefore prescribed ticagrelor, whereas those without the loss-of-function variant received clopidogrel.

After 1 year, the primary endpoint, a composite of cardiovascular death, MI, stroke, definite or probable stent thrombosis, and severe recurrent ischemia, occurred in 35 patients (4%) of the group that received genetically guided treatment, compared with 54 (5.9%) in the conventionally treated group (adjusted hazard ratio [HR], 0.66; 95% confidence interval [CI], 0.43 - 1.02; P = .56).

A prespecified analysis of total events (rather than just analysis of first event per patient) showed a 40% reduction in the genotyped group (HR, 0.60; 95% CI, 0.41 - 0.89; P = .011).

"Multiple adverse events represent a higher burden on the patient, so it is encouraging to see a significant reduction in cumulative events with genetically guided therapy," Pereira said.

There was no difference in the safety endpoint of TIMI major bleeding or minor bleeding between the two groups: 1.9% in the genetically guided group vs 1.6% in the conventional treatment group. 

The results did not differ between various subgroups in the trial, including race or ethnicity. Although Asian patients have a higher occurrence of the clopidogrel loss-of-function gene, the event risk reductions were similar in Asian and white patients in the study.

Pereira said the study may have been underpowered because of recent improvements in care. When the TAILOR-PCI trial was designed in 2012, around 10% to 12% of patients who received a stent could be expected to have a major adverse event, but during the trial, greater use of drug-coated stents and other treatments significantly reduced the expected rate of adverse events and made it more difficult for the trial to reach its goal of a 50% reduction in adverse events with the number of patients enrolled, he explained.

As part of the discussion, Mehran pointed out that more than 80% of the patients in the trial had acute coronary syndrome (ACS) and yet were being sent home on clopidogrel, which she said she found "daunting."

"This begs the question of whether they were lower-risk patients and not really the hot unstable ACS patients with large thrombus burden where we see higher event rates," Mehran commented.  

She also noted the results must be considered in the new era of platelet monotherapy, where aspirin is being withdrawn, and asked whether clopidogrel monotherapy would be considered safe without aspirin on board.

The researchers are planning a cost-effectiveness analysis of genetically guided therapy based on these data, and they are also continuing to follow patients over the longer term. 

The TAILOR-PCI study was funded by the Mayo Clinic in collaboration with the National Heart, Lung, and Blood Institute. Spartan Bioscience Inc supplied the genetic tests used. Pereira reports no relevant disclosures.

American College of Cardiology 2020 Scientific Session (ACC.20)/World Congress of Cardiology. Abstract 20-LB-20309-ACC.  Presented March 28, 2020.

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