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 R 1 to R 7 are each independently selected from a hydrogen atom, a halogen atom, or a C 1 - 6 alkyl group, a C 3 - 8 cycloalkyl group, a C 6 - 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 C 1 - 6 alkyl group, a C 1 - 6 alkoxy group, a C 1 - 6 alkoxy carbonyl group, a C 3 - 8 cycloalkyl group, a C 2 - 6 alkenyl group, a C 2 - 6 alkynyl group, and a phenyl group； wherein R 1 is a C 1 - 6 alkyl or a C 3 - 6 alkynyl, R 2 is H, -CH2-OH or -CH 2 -CH 2 -OH, and X is =O, (H, H) or (H, OH).
