Table 3.

Physiochemical properties of radiolabeled carboxylic acid- and hydroxamic acid-based HDAC ligands.

Compound	MW	Log D	RCY	Target	IC50 for HDACs	In Vivo Properties in Rodents	Reference
[11C]13	87.11	1.02	31–50%	Class I	HDAC1: 16 μM HDAC2: 12 μM HDAC3: 9 μM HDAC8: 15 μM	–	[86,87]
[11C]14	149.18	−0.20	40–55%	Class I	HDAC1: 64 μM HDAC2: 65 μM HDAC3: 260 μM HDAC8: 93 μM	–	[86,87]
[11C]15	143.21	0.26	38–50%	Class I	HDAC1: 39 μM HDAC2: 62 μM HDAC3: 161 μM HDAC8: 1103 μM	–	[86,87]
[11C]16	331.37	2.03 1	9% 3	HDAC1–3/6	HDAC1: 5 nM HDAC2: 32 nM HDAC3: 3.4 nM HDAC6: 5 nM	Brain uptake: Around 0.1% ID/cc immediately after i.v. injection (rat)	[89]
[11C]17	348.43	2.66 1	3% 3	HDAC1–3/6	HDAC1: 0.2 nM HDAC2: 1.2 nM HDAC3: 0.4 nM HDAC6: 1.6 nM	Brain uptake: Around 0.15% ID/cc immediately after i.v. injection (rat)	[89]
[11C]18	295.33	2.61 1	5% 3	HDAC8	HDAC8: 18 nM	Brain uptake: Around 0.2% ID/cc immediately after i.v. injection (rat)	[89]
[11C]19	334.41	1.33 2	8%	HDAC6	HDAC1: 5.2 μM HDAC6: 1.4 nM	Brain uptake: Radioactivity peaked in forebrain at 0.44 SUV and in cerebellum at 0.48 SUV (rat)	[93,94]
[11C]20	334.41	1.33 2	16%	HDAC6	HDAC6: 4 nM Others: ≥1.3 μM	–	[82,95]
[64Cu]21	1009.02	–	≥98%	Class I/IIb/III	Class I, IIb, III: 94 nM	Brain uptake: Biodistribution study was performed but brain uptake was not assessed (tumor-bearing mouse)	[96]

¹ Log p. ² clog D. ³ Non-decay corrected. MW: molecular weight; RCY: radiochemical yield (decay corrected).