Aims: To examine the relationship between polymorphisms in the platelet receptor glycoprotein (GP) Ib(alpha) and recurrent ischaemic events, and assess their impact on response to anti-platelet treatment.
Methods and results: 1014 patients presenting with unstable coronary syndrome were recruited from the OPUS-TIMI 16 clinical trial of the platelet GPIIb/IIIa antagonist, orbofiban. The subjects were genotyped for two polymorphisms in the gene for GPIb(alpha). These were a T-5C polymorphism in the 5' untranslated Kozak region of the GPIb(alpha) gene, and the variable number of tandem repeats (VNTR) in the macroglycopeptide region.165 patients had events (recurrent ischaemia, urgent revascularisation, myocardial infarction (MI), stroke and death). There was no effect of the number of -5C alleles on composite endpoint frequency among Caucasian subjects (test for trend, p = 0.47). However, MI risk increased with the number of -5C alleles carried, with MI occurring in 2.3% of patients with the -5T/-5T genotype, 5.0% of -5T/-5C, and 16.7% of -5C/-5C (p < 0.01). The effect of treatment on MI outcome was not significantly modified by genotype (test for interaction, p = 0.10). The overall risk of bleeding was not strongly influenced by either the -5C or the VNTR polymorphisms.
Conclusion: In an unstable coronary syndrome population the T-5C polymorphism in GPIb(alpha) influences risk of subsequent MI.