Conjugate and photoimmunotherapy

A conjugate comprising:

• A) an antibody molecule linked to a
• a compound represented by the following formula (Ia):
• where:
• L represents a direct bond or a linker;
• Q represents a reactive group for forming a bond to the antibody molecule or the particle;
• R2, R3, R7, and R8 are each independently selected from a substituted or unsubstituted alkyl and a substituted or unsubstituted aryl;
• R4, R5, R6, R9, R10 and R11, when present, are each independently selected from hydrogen, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkanoyl, a substituted or unsubstituted alkoxycarbonyl, a substituted or unsubstituted alkylcarbamoyl, and a chelating ligand, wherein at least one of R4, R5, R6, R9, R10, or R11 contains a water-soluble group;
• R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, and R23 are each independently selected from hydrogen, a halogen, a substituted or unsubstituted alkylthio, a substituted or unsubstituted alkylamino, and a substituted or unsubstituted alkoxy, or at least one of i) R13 and R14, and carbon atoms to which R13 and R14 are bonded, ii) R17 and R18, and carbon atoms to which R17 and R18 are bonded, or iii) R21 and R22, and carbon atoms to which R21 and R22 are bonded, form a fused ring;
• and
• X2 and X3 each independently represent a C1 to C10 alkylene with or without an intervening heteroatom between carbon-carbon bonds;
• and
• B) a magnetic particle or a semiconductor particle having an average particle diameter of 100 nm or less, which is linked to the antibody molecule:
• wherein at least one of the antibody molecule or the particle is linked to a portion showing increase of hydrophobicity when irradiated with a light beam having a wavelength of from 500 nm to 900 nm.