Purity >98%. Pyr3, a novel pyrazole, selectively inhibits TRPC3 channels. In B lymphocytes, Pyr3 eliminated the B cell receptor-induced Ca2+ oscillation regulated by TRPC3-mediated Ca2+ influx. In the cardiac system, Pyr3 attenuates activation of nuclear factor of activated T cells and hypertrophic growth in myocytes and pressure overloaded-induced hypertrophy in vivo.