An object of the present invention is to provide novel
apoptosis inhibitors and therapeutic agents for
inner ear hearing impairment. As a pharmaceutical agent for this purpose,
biguanide compounds represented by the following
structural formula (I) or a rapamycin derivative represented by the following
structural formula (II) as an
active ingredient is provided:wherein R1 to R7 are each independently selected from a
hydrogen atom, a
halogen atom, or a C1-6
alkyl group, a C3-8 cycloalkyl group, a C6-10
aryl group, a 5- or 6-membered heteroaryl group, or a 5- or 6-membered non-aromatic heterocyclic group, each of which may have a
substituent selected from a
halogen atom, a cyano group, a C1-6
alkyl group, a C1-6
alkoxy group, a C1-6 alkoxy
carbonyl group, a C3-8 cycloalkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group, and a
phenyl group;wherein R1 is a C1-6
alkyl or a C3-6 alkynyl, R2 is H, —CH2-OH or —CH2—CH2OH, and X is ═O, (H, H) or (H, OH).