Similarly, for HDAC10 (Figure ), interactions of the hydroxamic acid group with His136 and His137, alongside chelation with the Zn 2+ ion, are also observed. The tricyclic tetrahydro-γ-carboline capping group of tubastatin A has been shown to interact with residues E24 and W205. In contrast, the residue E274 can form electrostatic interactions with the tertiary amine in the capping group. Notably, E24 and E274 are critical for HDAC10 selectivity, facilitating the deep insertion of tubastatin A into the HDAC10 catalytic pocket. In light of these documented observations, tubastatin A emerges as a promising ligand candidate for developing dual degraders targeting both class IIb HDACs.