A method of synthesising a biomolecule-drug-conjugate, the method comprising: (i) either: (a) contacting a biomolecule having a pendent -NRH group with a support that is functionalised with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group; or (b) contacting a biomolecule having a pendent -NRH group with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group to produce a photocleavable group-biomolecule conjugate, and then immobilising the photocleavable group-biomolecule conjugate to a support; to provide an immobilised photocleavable group-biomolecule conjugate: (ii) optionally contacting the immobilised photocleavable group-biomolecule conjugate with a chemical modification agent or activating agent to provide an immobilised photocleavable group-biomolecule conjugate that is chemically modified or activated at the biomolecule portion; (iii) contacting the immobilised photocleavable group-biomolecule conjugate of step (i) or the chemically modified or activated immobilised photocleavable group-biomolecule conjugate of step (ii) with a drug component to form an immobilised photocleavable group-biomolecule-drug-conjugate: (iv) irradiating the immobilised photocleavable group-biomolecule-drug-conjugate of step (iii) with radiation thereby releasing the biomolecule-drug-conjugate wherein: -A- is absent or is a spacer group; -B- is absent or is a spacer group; 'Photocleavable group' comprises any residue that is able to cleave upon exposure to radiation to allow release of the biomolecule-drug-conjugate; R is selected from the group consisting of: H, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, C 1 -C 8 haloalkyl, -(CR a R a) n -C 3 -C 6 cycloalkyl, -(CR a R a) n -C 3 -C 6 heterocycloalkyl, -(CR a R a) n -C 3 -C 6 halocycloalkyl, -(CR a R a) n -aryl, and -(CR a R a) n -heteroaryl; R a is independently at each occurrence selected from: H, Me, CF 3 and F; n is an integer independently selected at each occurrence from 0, 1, 2 and 3; and 'Drug' is a residue of a drug molecule selected from the group consisting of tubulin inhibitors and DNA interacting agents. (i) either: (a) contacting a biomolecule having a pendent -NRH group with a support that is functionalised with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group; or (b) contacting a biomolecule having a pendent -NRH group with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group to produce a photocleavable group-biomolecule conjugate, and then immobilising the photocleavable group-biomolecule conjugate to a support; to provide an immobilised photocleavable group-biomolecule conjugate: (a) contacting a biomolecule having a pendent -NRH group with a support that is functionalised with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group; or (b) contacting a biomolecule having a pendent -NRH group with a photocleavable group under conditions suitable to covalently bond the biomolecule to the photocleavable group to produce a photocleavable group-biomolecule conjugate, and then immobilising the photocleavable group-biomolecule conjugate to a support; (ii) optionally contacting the immobilised photocleavable group-biomolecule conjugate with a chemical modification agent or activating agent to provide an immobilised photocleavable group-biomolecule conjugate that is chemically modified or activated at the biomolecule portion; (iii) contacting the immobilised photocleavable group-biomolecule conjugate of step (i) or the chemically modified or activated immobilised photocleavable group-biomolecule conjugate of step (ii) with a drug component to form an immobilised photocleavable group-biomolecule-drug-conjugate: (iv) irradiating the immobilised photocleavable group-biomolecule-drug-conjugate of step (iii) with radiation thereby releasing the biomolecule-drug-conjugate wherein: -A- is absent or is a spacer group; -B- is absent or is a spacer group; 'Photocleavable group' comprises any residue that is able to cleave upon exposure to radiation to allow release of the biomolecule-drug-conjugate; R is selected from the group consisting of: H, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, C 1 -C 8 haloalkyl, -(CR a R a) n -C 3 -C 6 cycloalkyl, -(CR a R a) n -C 3 -C 6 heterocycloalkyl, -(CR a R a) n -C 3 -C 6 halocycloalkyl, -(CR a R a) n -aryl, and -(CR a R a) n -heteroaryl; R a is independently at each occurrence selected from: H, Me, CF 3 and F; n is an integer independently selected at each occurrence from 0, 1, 2 and 3; and 'Drug' is a residue of a drug molecule selected from the group consisting of tubulin inhibitors and DNA interacting agents. -A- is absent or is a spacer group; -B- is absent or is a spacer group; 'Photocleavable group' comprises any residue that is able to cleave upon exposure to radiation to allow release of the biomolecule-drug-conjugate; R is selected from the group consisting of: H, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, C 1 -C 8 haloalkyl, -(CR a R a) n -C 3 -C 6 cycloalkyl, -(CR a R a) n -C 3 -C 6 heterocycloalkyl, -(CR a R a) n -C 3 -C 6 halocycloalkyl, -(CR a R a) n -aryl, and -(CR a R a) n -heteroaryl; R a is independently at each occurrence selected from: H, Me, CF 3 and F; n is an integer independently selected at each occurrence from 0, 1, 2 and 3; and 'Drug' is a residue of a drug molecule selected from the group consisting of tubulin inhibitors and DNA interacting agents.