Medicure has developed a transdermal delivery formulation of its lead drug, Aggrastat (tirofiban HCl). The ability to administer a drug transdermally provides a convenient way to deliver a stable, therapeutic level of medication to the patient. Aggrastat and other antiplatelet drugs of its class (known as glycoprotein IIb/IIIa inhibitors or GPIs) are currently only administered by intravenous infusion. In vivo proof of principle for the transdermal delivery of therapeutic levels of Aggrastat's active ingredient, tirofiban, was recently established in animal studies conducted in collaboration with 4P Therapeutics. The latter has entered into an agreement with Medicure's subsidiary, Medicure International, to further develop transdermal tirofiban.
Medicure's initial target use for transdermal tirofiban is the treatment of acute coronary syndromes for which the drug is already approved by the FDA and currently receives a class I recommendation from the nationally recognised ACCF/AHA treatment guidelines. The delivery of tirofiban by a novel, transdermal method has potential to provide significant advantages over the current treatments used in this setting, including the potential for increased use prior to hospitalisation.
The global market for antiplatelet drugs is over US$8 billion per year, of which Aggrastat and the other intravenous GPIs make up approximately US$500 million per year. The largest share of the market is held by oral antiplatelet drugs, such as clopidogrel (Plavix) and ASA (Aspirin), which by virtue of their route of administration can be used in a variety of settings where intravenous administration is not feasible. While these treatments will continue to serve an important role in cardiovascular therapy, the use of oral antiplatelet drugs for some patients and conditions is limited by a number of drawbacks including inter-individual variability, resistance, drug-drug interactions and delays in reversal of effect. Transdermal tirofiban has the potential to avoid these problems and to carry the benefits of a GPI, including the ability to dissolve and to directly prevent formation of platelet aggregates (blood clots).
If successful in advancing transdermal tirofiban, Medicure may also look to expand the development and application of this product to other indications that are not satisfactorily treated with current antiplatelet drugs. One such potential application may be in providing platelet inhibition to patients who have been required to stop use of oral platelet inhibitors prior to surgery (commonly referred to as "bridging therapy"). Tirofiban's properties as a broadly effective, rapidly reversible, small-molecule platelet inhibitor, combined with a simple means of delivering the drug outside of a hospital setting, make this a promising opportunity.
Aggrastat, in combination with heparin, is indicated for the treatment of acute coronary syndrome, including patients who are to be managed medically and those undergoing PTCA or atherectomy. In this setting, Aggrastat has been shown to decrease the rate of a combined endpoint of death, new myocardial infarction or refractory ischaemia/repeat cardiac procedure. Aggrastat has been studied in a setting that included aspirin and heparin.