A pyrazine derivative represented by the following formula (I) or a pharmaceutically acceptable salt thereof, or one of its solvates: * (See formula) ** where, X1 represents a nitrogen atom or CH； R1 represents a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a halogen atom, a trifluoromethyl group, a group difluoromethyl, a cyano group, a C2-C7 alkylcarbonyl group, a C1-C6 alkyl sulfonyl group, a nitro group, an amino group, a di (C1-C6 alkyl) amino group, a formyl group, a hydroxyl group, a C1-C6 alkoxy group, a C1-C6 alkylthio group or a phenyl group or a phenoxy group that may be substituted with 1 to 3 Ra； Ra represents a halogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group or a C1-C6 alkoxy group； R2 represents a C1-C6 alkyl group, a C3-C6 cycloalkyl group or a C1-C6 alkoxy group； p represents any integer from 0 to 2； R3 represents a hydrogen atom, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a C1-C6 alkoxy group, an alkylcarbonyl group of C2-C7, a C1-C6 alkylthio group, a halogen atom, a trifluoromethyl group, a difluoromethyl group, a cyano group, a phenyl group, a pyridyl group, a phenoxy group or a COORb； ...Un derivado de pirazina representado por la siguiente fórmula (I) o una de sus sales farmacéuticamente aceptables, o uno de sus solvatos: *(Ver fórmula)** donde, X1 representa un átomo de nitrógeno o CH； R1 representa un átomo de hidrógeno, un grupo alquilo de C1-C6, un grupo cicloalquilo de C3-C6, un grupo alquenilo de C2-C6, un grupo alquinilo de C2-C6, un átomo de halógeno, un grupo trifluorometilo, un grupo difluorometilo, un grupo ciano, un grupo alquilcarbonilo de C2-C7, un grupo alquilsulfonilo de C1-C6, un grupo nitro, un grupo amino, un grupo di(alquil de C1-C6)amino, un grupo formilo, un grupo hidroxilo, un grupo alcoxi de C1-C6, un grupo alquiltio de C1-C6 o un grupo fenilo o un grupo fenoxi que puede estar sustituido con 1 a 3
