Abstract: The present disclosure provides bicyclic pyridine derivatives. A compound represented by formula I: or a pharmaceutically acceptable salt thereof, wherein X is a oxygen atom, sulfur atom, NR, or CR?R?, n is 0 or 1, R1, R2a, R2b, R2c, R2d, R, R? and R? are each independently a hydrogen atom, a halogen atom, optionally substituted C1-6 alkyl, or an optionally substituted C6-10 aryl, or two of R2a, R2b, R2c, R2d, R, R?, and R?, together with a carbon atom or a nitrogen atom to which they are attached, form a 3- to 6-membered saturated carbocyclic ring or saturated heterocyclic ring, and R3a, R3b, R3c and R5a and R5b, are as defined in the description.