Comparative analysis of ligand binding affinities and functional profiles at recombinant human β-adrenergic receptor subtypes 1, 2, and 3

β-adrenergic receptors (β x AR) are GPCRs with major physiological and therapeutic relevance in cardiovascular and respiratory conditions. Although numerous ligands have been investigated, binding affinities and functional annotations remain incomplete and fragmented across databases. This review systematically integrates ligand binding affinities and functional profiles at recombinant human β x AR from the PDSP K i database and the IUPHAR/BPS Guide to Pharmacology, with a focus on clinically important ligands, receptor selectivity, and characteristic patterns. Database agreement, affinity patterns, stereoisomer-specific information and concordance with primary literature are evaluated. In total, 156 ligands with pK i ≥ 5 were collected. Median pK i values were 6.6 for hβ 1 AR, 6.15 for hβ 2 AR, and 5.8 for hβ 3 AR. A pronounced overlap between hβ 1 AR and hβ 2 AR was observed, reflected in similar median affinities and shared ligand profiles, whereas hβ 3 AR showed narrower data coverage and a more distinct affinity distribution. Most ligands were listed for more than one hβ x AR, and 37 ligands had binding data for all three hβ x AR. Functional characterization was available for 90 ligands, whereas 61 lacked annotations. Database comparison revealed low overlap in ligand listings (28.8%). Stereoisomer data were highly incomplete, and in several cases, affinity-based stereoisomer comparisons differed from literature-reported stereoisomeric superiority. Summarized, substantial similarity between hβ 1 AR and hβ 2 AR ligand binding patterns is observed, while hβ 3 AR appears less extensively characterized. Considerable fragmentation, incomplete receptor profiling and methodological heterogeneity limit the evaluation of receptor and ligand characteristics. Binding affinity and functional behavior must be interpreted as context-dependent parameters influenced by experimental systems, G-protein coupling conditions and stereochemical specification.