The synthesis and analysis of a bombesin analogue for radiotherapy of prostate cancer

University essay from KTH/Skolan för kemi, bioteknologi och hälsa (CBH)

Abstract: Targeted radionuclide therapy is becoming a widely used cancer treatment strategy. By radiolabeling receptor-specific peptides, cancer cells overexpressing the receptor can be selectively targeted, and the cytotoxic radionuclide can be delivered to the target cell or tissue for therapeutic or diagnostic purposes. Bombesin analogues have been previously developed and utilized to target the gastrin-releasing peptide receptor (GRPR), a receptor commonly overexpressed in prostate cancer cells. The RM26 analogue derived from the native bombesin is an antagonistic ligand of GRPR and a possible candidate for targeted radiotherapy. Prolonging the half-life of the molecule is an important aspect of developing a new protein therapeutic. Using albumin binding domain (ABD) for this purpose is an emerging strategy in recent years. ABD is able to bind to serum albumin and thus remains in the blood circulation for a long period of time. It is also a scaffold for protein engineering efforts and by coupling receptor-specific ligands to ABD, the target-specific binding along with extended in vivo halflife can be achieved. In this project, an RM26 analogue with a PEG linker and ABD with a DOTA chelator for future radiolabeling were synthesized with solid phase peptide synthesis (SPPS), conjugated, purified by RP-HPLC and analyzed by mass spectrometry. The binding properties of the conjugate were evaluated by SPR-based biosensory studies, and further experiments are planned for the testing the product and its potential application in radionuclide therapy.

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