Coordination-Mediated Synthesis of 67Ga-Labeled Purification-Free

Aug 10, 2018 - A large excess of unlabeled ligands over gallium-67 (67Ga) provide 67Ga-labeled probes with high radiochemical yields in short reaction...
0 downloads 0 Views 675KB Size
Subscriber access provided by Kaohsiung Medical University

Article 67

Coordination-Mediated Synthesis of Ga-Labeled PurificationFree Trivalent Probes for In Vivo Imaging of Saturable Systems Holis Abdul Holik, Tomoya Uehara, Soki Nemoto, Takemi Rokugawa, Yuumi Tomizawa, Ayako Sakuma, Yuki Mizuno, Hiroyuki Suzuki, and Yasushi Arano Bioconjugate Chem., Just Accepted Manuscript • DOI: 10.1021/acs.bioconjchem.8b00337 • Publication Date (Web): 10 Aug 2018 Downloaded from http://pubs.acs.org on August 13, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Bioconjugate Chemistry

Coordination-Mediated Synthesis of 67Ga-Labeled Purification-Free Trivalent Probes for In Vivo Imaging of Saturable Systems Holis A. Holik†,‡, Tomoya Uehara†*, Soki Nemoto†, Takemi Rokugawa†, Yuumi Tomizawa†, Ayako Sakuma†, Yuki Mizuno†,§, Hiroyuki Suzuki†, and Yasushi Arano† †

Laboratory of Molecular Imaging and Radiotherapy, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan



Department of Pharmaceutical Analysis and Medicinal Chemistry, Faculty of Pharmacy,

Universitas Padjadjaran, Jl. Raya Bandung-Sumedang KM 21, Sumedang 46363, Indonesia §

Laboratory of Physical Chemistry, Showa Pharmaceutical University, 3-3165 HigashiTamagawagakuen, Machida, Tokyo 194-8543, Japan.

Keywords: gallium-67, SPECT, PET, schiff base

ACS Paragon Plus Environment

1

Bioconjugate Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 33

ABSTRACT

A large excess of unlabeled ligands over gallium-67 (67Ga) provide 67Ga-labeled probes with high radiochemical yields in short reaction time. However, the unlabeled ligand hinders target accumulation of radiolabeled probes by competing for target molecules. To circumvent the problem, we investigated the way to prepare 67Ga-labeled multivalent probes from monovalent ligands. The reaction of a bi- or tri-dentate ligand with [67Ga]Ga-citrate resulted in 67Ga-labeled probes of insufficient stability. However, the reaction of [67Ga]Ga-citrate with a mixture of RGDconjugated salicylaldehyde and triamine provided a

67

Ga-labeled trivalent probe with stability

sufficient for in vivo applications. Since the free Schiff base ligand decomposed rapidly upon injection, the

67

Ga-labeled trivalent probe visualized murine tumor without post-labeling

purification, which was not achieved with a 67Ga-labeled trivalent probe from a trivalent ligand. These findings indicate the availability of Schiff base ligands to prepare

67

Ga-labeled trivalent

probes by a simple radiolabeling procedure.

ACS Paragon Plus Environment

2

Page 3 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Bioconjugate Chemistry

INTRODUCTION Bioactive molecules labeled with metallic radionuclides such as gallium-67/68 (67/68Ga), technetium-99m (99mTc) and indium-111 have been developed and used in preclinical and clinical studies.1-4 These radiolabeled probes are generally prepared by conjugating an appropriate chelator to a biomolecule of interest (referred to as “ligand”) and subsequent complexation reaction with metallic radionuclides to ensure high in vivo stability. The radiolabeled ligands are synthesized in the presence of a large excess of ligands over metallic radionuclides to ensure high radiochemical yields in short reaction time, due to the low concentration of metallic radionuclides (67Ga: 37 MBq/mL corresponding to 2.5 × 10-8 M) (Figure 1C).1 The presence of a large excess of unlabeled ligands in the injectate impairs target uptake of the radiolabeled ligands by competing for target molecules, which results in poor images of the target molecules of low expression levels.5-9 The free ligands can be removed from the radiolabeled ligands by HPLC or other purification methods. However, such manipulation significantly wastes time and radioactivity and impairs the practical utility and advantages of using metallic radionuclides. To circumvent the problem, we recently developed a new design concept of metal coordinationmediated synthesis of 99mTc-labeled trivalent probes using [99mTc][Tc(CO)3(OH2)3]+ and isonitrileconjugated

RGD

peptide

(CN-RGD).8

In

this

design,

three

water

molecules

in

[99mTc][Tc(CO)3(OH2)3]+ are displaced with the three monovalent ligands (CN-RGD) to prepare a trivalent [99mTc][Tc(CO)3(CN-RGD)3]+ probe. [99mTc][Tc(CO)3(CN-RGD)3]+ acquired higher integrin αvβ3 binding affinity than its monovalent ligand (Figure 1A-1). In SPECT imaging studies, [99mTc][Tc(CO)3(CN-RGD)3]+ clearly visualized murine tumors without removing the unlabeled ligands. However, a 99mTc-labeled monovalent probe prepared from a monovalent ligand failed to

ACS Paragon Plus Environment

3

Bioconjugate Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 33

(A) In situ multivalent “1 to 3” or “1 to 2” designs Reaction solution

A-1

1:3 reaction

M

M

M (