Table 1 [35–38] summarizes binding affinities (IC50) for somatostatin-14 and for 5 somatostatin analogs. Somatastain-14 binds to all 5 sstrs with similar binding affinity, while both octreotide and lanreotide exhibit relative selectivity for sstr2. This selectivity profile is consistent with studies that have ascribed the efficacy of octreotide and lanreotide at inhibiting growth hormone release from somatotroph adenomas to their activity at sstr2 [39].
Table 1 Binding affinities (IC50) for various somatostatin analogs at the 5 known somatostatin receptor subtypes
Binding affinity (IC50), nmol/L
Analog sstr1 sstr2 sstr3 sstr4 sstr5
 Somatostatin-14 0.93 0.15 0.56 1.5 0.29
 Octreotide 280 0.38 7.1 >1000 6.3
 Lanreotide 180 0.54 14 230 17
 Vapreotide >1000 5.4 31 45 0.7
 Pasireotide 9.3 1.0 1.5 >100 0.16
 Somatoprim [35] >1000 3 >100 7 6