MARKET:    A case for Phenotype testing

Which is right for you: Plavix?  Or Effient? Or Brilinta? Or Aspirin or a combination?

“We’ve always had platelet function testing available with the gold standard, light transmission aggregometry.  Using that method, I can tell if the patient’s inhibited, whether they’re on aspirin, clopidogrel, or prasugrel, but I can’t do it quickly,” said Sanfelippo. “It takes anywhere from an hour-and-a-half to two hours to complete, from the time the blood arrives in the lab.”* - Marshfield Labs

“If a patient’s baseline is

60 percent inhibition, we know we’ll probably

have to wait at least five days prior to

going to surgery. If they’re that high, we’ll

start testing every 24 hours until they get to

less than 20 percent. On the other hand, if

their baseline is 28 percent,

we’ll test every 12 hours,

or even every six hours.*” –Huntsville Hosp.

The standard therapy has been aspirin plus clopidogrel (brand name Plavix) for 2-6 months after bare metal stents and a year or more after drug-eluting stents.

But in July 2009, the FDA approved a new and more potent antiplatelet drug: prasugrel (brand name Effient). One caution about prasugrel has been that, because it is more powerful, it may have pose an increased risk of bleeding complications for the patient.

Effient: “Compared to clopidogrel (Plavix), prasugrel inhibits adenosine diphosphate–induced platelet aggregation more rapidly, more consistently, and to a greater extent than do standard and higher doses of clopidogrel in healthy volunteers and in patients with coronary artery disease, including those undergoing PCI“  -Wiviott SD, Braunwald E, McCabe CH et al (2007). "Prasugrel versus clopidogrel in patients with acute coronary syndromes". N Engl J Med 357 (20): 2001–15. doi:10.1056/NEJMoa0706482

Brilinta was approved by the US Food and Drug Administration on July 20, 2011  “Ticagrelor is the only one in the group that has shown a reduction in mortality, and I always put a lot of weight into that. Saving lives is what you want to do,” Faxon said. “The bleeding rates are probably more significant than the papers would have you realize, but it seems to have a better profile than prasugrel. It has a relatively short half-life. So you can administer the drug and it works right away, and you can stop it and it goes away very quickly.” -David P. Faxon, MD, vice chair of medicine for strategic planning at the Brigham and Women’s Hospital, Boston, and Cardiology Today Editorial Board member

Other Drugs:  cangrelor, an IV-administered thienopyridine that is a direct and reversible P2Y12 inhibitor. This drug has the advantage of having an even more rapid onset and offset than ticagrelor due to IV administration.

Basic FAQ and Background of Platelets and Drugs:

Why do we take Aspirin?
To reduce the risk of a heart attack, stroke or other cardio events.

Why do we take Plavix or Effient?
For those considered “at risk” who have already experienced a heart attack or other cardio event, aspirin alone isn’t enough protection so Plavix is prescribed and sometimes both Plavix and aspirin are prescribed in combination.

How does aspirin and Plavix ‘work’.
By limiting the ‘clotting’  of platelets, the blood cells that are responsible for wound care when bleeding.  Sometimes platelets become ‘sticky’ and build up internally along blood vessels and can form clots that result in a heart attack or stroke.

PROBLEM OUTLINED:
How does the patient or physician know if the drugs are working? 
Clinical studies show that there is a significant portion, 20-30+% of the population that are resistant to aspirin and plavix.  Clinical data suggests that for those who are resistant to aspirin, there is a 4 times greater chance of a heart attack, stroke or death.

How does the physician know how much aspirin or Plavix to prescribe?
To date there is not an accurate, reliable, easy diagnostic test to determine if patients who are taking aspiring or Plavix.  The goal of antiplatelet drugs are to inhibit platelet function.  Platelets are ‘inhibited’ from activating and clotting – thereby reducing the chances of a heart attack.

How can we test for platelet function now?
The current ‘gold standard’ test is a laboratory test.  It requires several vials of a blood sample drawn from the patient’s arm.  The laboratory device is expensive and requires a trained lab technician for an hour.  This is an accurate test, but is hardly practical and is expensive.

How can we test for platelet function now?
The current ‘gold standard’ test is a laboratory test.  It requires several vials of a blood sample drawn from the patient’s arm.  The laboratory device is expensive and requires a trained lab technician for an hour.  This is an accurate test, but is hardly practical and is expensive.

What is measured in a platelet function test?
The ‘gold standard’ laboratory test that is the most credible according to the indusry’s Key Opinion Leaders (KOL) measure the % of platelet inhibition…meaning what % of the platelets that are non-functioning.  The more inhibited platelets are, the less likely they will be ‘sticky’, reducing the chances of a heart attack or stroke.

Why is measuring important?
Patients want to know if aspirin and Plavix are working.  Physicians need to know to determine the optimal amount of drugs to prescribe.

Is aspirin and Plavix safe?
Not for everyone.  Recent studies show that there are significant risks for some people taking aspirin as well as Plavix.  In addition to stomach and intestinal problems, too much platelet inhibition can mean that a patient may experience bleeding with no way of stopping the bleeding.

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