177Lu-AMBA: Synthesis and characterization of a selective 177Lu-labeled GRP-R agonist for systemic radiotherapy of prostate cancer

Lantry, Laura E; Cappelletti, Enrico; Maddalena, Mary Ellen; Fox, Jaclyn S; Feng, Weiwei; Chen, Jianqing; Thomas, Regi; Eaton, Stephen M; Bogdan, Nancy J; Arunachalam, Thangavel; Reubi, Jean Claude; Raju, Natarajan; Metcalfe, Edmund C; Lattuada, Luciano; Linder, Karen E; Swenson, Rolf E; Tweedle, Michael F; Nunn, Adrian D (2006). 177Lu-AMBA: Synthesis and characterization of a selective 177Lu-labeled GRP-R agonist for systemic radiotherapy of prostate cancer. Journal of nuclear medicine, 47(7), pp. 1144-52. New York, N.Y.: Society of Nuclear Medicine

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Gastrin-releasing peptide receptors (GRP-R) are upregulated in many cancers, including prostate, breast, and lung. We describe a new radiolabeled bombesin (BBN) analog for imaging and systemic radiotherapy that has improved pharmacokinetics (PK) and better retention of radioactivity in the tumor. METHODS: DO3A-CH2CO-G-4-aminobenzoyl-Q-W-A-V-G-H-L-M-NH2 (AMBA) was synthesized and radiolabeled. The human prostate cancer cell line PC-3 was used to determine the binding (Kd), retention, and efflux of 177Lu-AMBA. Receptor specificity was determined by in vitro autoradiography in human tissues. PK and radiotherapy studies were performed in PC-3 tumor-bearing male nude mice. RESULTS: 177Lu-AMBA has a high affinity for the GRP-R (Kd, 1.02 nmol/L), with a maximum binding capacity (Bmax) of 414 fmol/10(6) cells (2.5 x 10(5) GRP-R/cell). Internalization was similar for 177Lu-AMBA (76.8%), 177Lu-BBN8 (72.9%), and 125I-[Tyr4]-BBN (74.9%). Efflux was markedly lower for 177Lu-AMBA (2.9%) compared with 177Lu-BBN8 (15.9%) and 125I-[Tyr4]-BBN (46.1%). By receptor autoradiography, Lu-AMBA binds specifically to GRP-R (0.8 nmol/L) and to the neuromedin B receptor (NMB-R) (0.9 nmol/L), with no affinity for the bb3 receptor (>1,000 nmol/L). 177Lu-AMBA was renally excreted (55 %ID 1 h [percentage injected dose at 1 h]); tumor uptake at 1 and 24 h was 6.35 %ID/g and 3.39 %ID/g, respectively. One or 2 doses of 177Lu-AMBA (27.75 MBq/dose) significantly prolonged the life span of PC-3 tumor-bearing mice (P < 0.001 and P < 0.0001, respectively) and decreased PC-3 tumor growth rate over controls. When compared using World Health Organization criteria, mice receiving 2 doses versus 1 dose of 177Lu-AMBA demonstrated a shift away from stable/progressive disease toward complete/partial response; by RECIST (Response Evaluation Criteria in Solid Tumors), median survival increased by 36% and time to progression/progression-free survival increased by 65%. CONCLUSION: 177Lu-AMBA binds with nanomolar affinity to GRP-R and NMB-R, has low retention of radioactivity in kidney, demonstrates a very favorable risk-benefit profile, and is in phase I clinical trials.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Service Sector > Institute of Pathology

UniBE Contributor:

Reubi, Jean-Claude

ISSN:

0161-5505

ISBN:

16818949

Publisher:

Society of Nuclear Medicine

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:48

Last Modified:

17 Mar 2015 21:49

PubMed ID:

16818949

Web of Science ID:

000238879300017

URI:

https://boris.unibe.ch/id/eprint/20297 (FactScience: 3553)

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