[³H]UR‐DE257: Development of a Tritium‐Labeled Squaramide‐Type Selective Histamine H₂ Receptor Antagonist

Abstract

A series of new piperidinomethylphenoxypropylamine-type histamine H2 receptor (H2 R) antagonists with different substituted "urea equivalents" was synthesized and characterized in functional in vitro assays. Based on these data as selection criteria, radiosynthesis of N-[6-(3,4-dioxo-2-{3-[3-(piperidin-1-ylmethyl)phenoxy]propylamino}cyclobut-1-enylamino)hexyl]-(2,3-(3) H2 )propionic amide ([(3) H]UR-DE257) was performed. The radioligand (specific activity: 63 Ci mmol(-1) ) had high affinity for human, rat, and guinea pig H2 R (hH2 R, Sf9 cells: Kd , saturation binding: 31 nM, kinetic studies: 20 nM). UR-DE257 revealed high H2 R selectivity on membranes of Sf9 cells, expressing the respective hHx R subtype (Ki values: hH1 R: >10000 nM, hH2 R: 28 nM, hH3 R: 3800 nM, hH4 R: >10000 nM). In spite of insurmountable antagonism, probably due to rebinding of [(3) H]UR-DE257 to the H2 R (extended residence time), the title compound proved to be a valuable pharmacological tool for the determination of H2 R affinities in competition binding assays.

NanoBRET binding assay for histamine H2 receptor ligands using live recombinant HEK293T cells

“…The synthesis of precursor UR-DE36 (6, Fig. 1) was carried out as previously reported in five steps 28,29 . Subsequently, 6 was treated with the respective labeling reagent (13)(14)(15)Fig.…”

“…1), a potent and long-acting histamine H 2 receptor antagonist developed by Brystol-Myers in the 1980s 26 , and radioligand [ 3 H]UR-DE257 (7, Fig. 1) from our laboratory 27,28 . These fluorescent tracers were tested for their suitability in the BRET binding assay.…”

Highly Potent, Stable, and Selective Dimeric Hetarylpropylguanidine-Type Histamine H2 Receptor Agonists

“…To investigate the affinities of 5 , 53 – 63 , 127 – 141 , and 145 at the four h HR subtypes, competition binding studies were performed using the radioligands [ 3 H]mepyramine ( h H 1 R), [ 3 H]tiotidine or [ 3 H]UR-DE257 21 ( h H 2 R), [ 3 H] N α -methylhistamine ( h H 3 R), and [ 3 H]histamine ( h H 4 R). The imidazol-4-yl-type homodimeric ligands 56 and 57 , containing a decamethylene and a dodecamethylene spacer, respectively, exhibited the highest affinities at every HR subtype with the following selectivity profile: p K i H 1 R < H 2 R ≈ H 3 R ≈ H 4 R ( Table 1 ).…”

Initial Characterization of Transgenic Mice Overexpressing Human Histamine H2Receptors

“…Slides with mounted cryosections were immediately placed in a chamber at 100% humidity and covered with binding buffer. After 10-15 minutes, the binding buffer was carefully removed, followed by covering the sections with binding buffer containing the selective H 2 receptor antagonist [ 3 H]UR-DE257 (Baumeister et al, 2015) (30 nM) (total binding) or binding buffer containing [ 3 H]UR-DE257 (30 nM) and the histamine H 2 receptor antagonist famotidine (9 mM) (unspecific binding). The sections were incubated in a humidity chamber at room temperature for 60 minutes, followed by a previously described washing and drying procedure (Keller et al, 2008).…”