THE PRESENT INVENTION RELATES TO A COMPOUND REPRESENTED BY THE FORMULA: WHEREIN A IS PYRIDYL GROUP HAVING AT LEAST ONE SUBSTITUENT WHEREIN R1, R2 AND R3 ARE EACH A HYDROGEN ATOM, A HALOGEN ATOM, A C1-6 ALKYL GROUP OPTIONALLY SUBSTITUTED BY HALOGEN OR A C1-6 ALKOXY GROUP OPTIONALLY SUBSTITUTED BY HALOGEN, R4 AND R6 ARE EACH A HYDROGEN ATOM, A HALOGEN ATOM OR A C1-6 ALKYL GROUP OPTIONALLY SUBSTITUTED BY HALOGEN, R5 IS A HYDROGEN ATOM, A HALOGEN ATOM, A C1-6 ALKYL GROUP OPTIONALLY SUBSTITUTED BY HALOGEN OR A C1-6 ALKOXY GROUP OPTIONALLY SUBSTITUTED BY HALOGEN, AND R7 IS A HYDROGEN ATOM OR A C1-6 ALKYL GROUP OPTIONALLY SUBSTITUTED BY HALOGEN OR A SALT THEREOF, OR A PHARMACEUTICAL COMPOSITION CONTAINING THE SAME.