Gastrin-Releasing Peptide Receptor Silencing Impairs Mitochondrial Metabolism via Serine Hydroxymethyltransferase 2 in Neuroblastoma

Background: [68Ga]Ga-RM2 is a potent Gastrin-Releasing Peptide-receptor (GRP-R) antagonist for imaging prostate cancer and breast cancer, currently under clinical evaluation in several specialized centers around the world. Targeted radionuclide therapy of GRP-R-expressing tumors is also being investigated. We here report the characteristics of a kit-based formulation of RM2 that should ease the development of GRP-R imaging and make it available to more institutions and patients. Methods: Stability of the investigated kits over one year was determined using LC/MS/MS and UV-HPLC. Direct 68Ga-radiolabeling was optimized with respect to buffer (pH), temperature, reaction time and shaking time. Conventionally prepared [68Ga]Ga-RM2 using an automated synthesizer was used as a comparator. Finally, the [68Ga]Ga-RM2 product was assessed with regards to hydrophilicity, affinity, internalization, membrane bound fraction, calcium mobilization assay and efflux, which is a valuable addition to the in vivo literature. Results: The kit-based formulation, kept between 2 °C and 8 °C, was stable for over one year. Using acetate buffer pH 3.0 in 2.5–5.1 mL total volume, heating at 100 °C during 10 min and cooling down for 5 min, the [68Ga]Ga-RM2 produced by kit complies with the requirements of the European Pharmacopoeia. Compared with the module production route, the [68Ga]Ga-RM2 produced by kit was faster, displayed higher yields, higher volumetric activity and was devoid of ethanol. In in vitro evaluations, the [68Ga]Ga-RM2 displayed sub-nanomolar affinity (Kd = 0.25 ± 0.19 nM), receptor specific and time dependent membrane-bound fraction of 42.0 ± 5.1% at 60 min and GRP-R mediated internalization of 24.4 ± 4.3% at 30 min. The [natGa]Ga-RM2 was ineffective in stimulating intracellular calcium mobilization. Finally, the efflux of the internalized activity was 64.3 ± 6.5% at 5 min. Conclusion: The kit-based formulation of RM2 is suitable to disseminate GRP-R imaging and therapy to distant hospitals without complex radiochemistry equipment.

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Female gastrin-releasing peptide receptor (GRP-R)-deficient mice exhibit altered social preference for male conspecifics: implications for GRP/GRP-R modulation of GABAergic function

Brain Research ◽

10.1016/s0006-8993(01)02032-7 ◽

2001 ◽

Vol 894 (2) ◽

pp. 281-287 ◽

Cited By ~ 16

Author(s):

Kazuyuki Yamada ◽

Etsuko Wada ◽

Keiji Wada

Keyword(s):

Social Preference ◽

Peptide Receptor ◽

Gastrin Releasing Peptide ◽

Gabaergic Function ◽

Deficient Mice

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In Vivo Biodistribution and Efficacy Evaluation of NeoB, a Radiotracer Targeted to GRPR, in Mice Bearing Gastrointestinal Stromal Tumor

Cancers ◽

10.3390/cancers13051051 ◽

2021 ◽

Vol 13 (5) ◽

pp. 1051

Author(s):

Christopher Montemagno ◽

Florian Raes ◽

Mitra Ahmadi ◽

Sandrine Bacot ◽

Marlène Debiossat ◽

...

Keyword(s):

Therapeutic Agent ◽

Tumor Volume ◽

Tumor Regression ◽

Efficacy Evaluation ◽

Peptide Receptor ◽

Gastrin Releasing Peptide ◽

Target Organs ◽

G Protein Coupled ◽

Complete Tumor

NeoB is a radiotracer targeting the gastrin-releasing peptide receptor (GRPR), a G-protein–coupled receptor expressed in various cancers. The aim of the present study was to evaluate the biodistribution and efficacy of this new therapeutic agent in Gastrointestinal Stromal Tumors (GIST). Eighty-two SCID mice bearing GIST-882 tumors were employed. [177Lu]Lu-NeoB biodistribution was evaluated up to seven days by organ sampling (200 pmol/0.8 MBq, i.v.). For efficacy evaluation, mice received either saline, 400 pmol or 800 pmol of [177Lu]Lu-NeoB (37MBq, 1/w, 3 w, i.v.). SPECT/CT imaging was performed at 24 h, and tumor volume was determined up to 100 days. Elevated and specific [177Lu]Lu-NeoB uptake was found in the GIST tumor, as demonstrated by in vivo competition (19.1 ± 3.9 %ID/g vs. 0.3 ± 0.1 %ID/g at 4h). [177Lu]Lu-NeoB tumor retention (half-life of 40.2 h) resulted in elevated tumor-to-background ratios. Tumor volumes were significantly reduced in both treated groups (p < 0.01), even leading to complete tumor regression at the 400 pmol dose. [177Lu]Lu-NeoB exhibited excellent pharmacokinetics with elevated and prolonged tumor uptake and low uptake in non-target organs such as pancreas. The potential of this new theragnostic agent in different indications, including GIST, is under evaluation in the FIH [177Lu]Lu-NeoB clinical trial.

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