Novel molecular imaging of atherosclerosis with gallium-68-labeled apolipoprotein A-I mimetic peptide and positron emission tomography.

BACKGROUND: High-density lipoprotein (HDL) plays a major role in reverse cholesterol transport. Many researchers have been working to enhance the biochemical function of HDL for use in therapy. Although HDL therapy using injections of apolipoprotein (apo)-A-I mimetics, apo A-I Milano or full-length apo A-I is dramatically effective, it is still unclear whether apo A-I or apo A-I mimetics actually enter atherosclerotic plaque and remove cholesterol from the lipid burden. We synthesized a novel 24-amino acid apo A-I mimetic peptide (known as FAMP) that potently removes cholesterol via specific ATP-binding cassette transporter A1. We then investigated the potential of FAMP to image developing plaque lesions in vivo. METHODS AND RESULTS: FAMP was modified with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and radiolabeled with gallium-68 ((68)Ga) for noninvasive positron emission tomography (PET) in an animal model (familial hypercholesterolemic myocardial infarction-prone rabbits: WHHL-MI) with atherosclerotic lesions. The (68)Ga-DOTA-FAMP was dramatically taken up by atherosclerotic tissues in the blood vessels and aorta of WHHL-MI rabbits, but not the control rabbits. CONCLUSIONS: An apo A-I mimetic peptide with (68)Ga-DOTA is a promising candidate diagnostic tracer for PET imaging of the atherosclerotic lipid burden and may contribute to the development of a tool for the diagnosis of plaque with PET.

[Microdose clinical trial--impact of PET molecular imaging].

Microdose (MD) clinical trial and exploratory IND study including sub-therapeutic dose and therapeutic dose which are higher than microdoses are expected to bring about innovations in drug development. The outlines of guidances for microdose clinical trial and ICH-M3 (R2) issued by the MHLW in June, 2008, and February, 2010, are first explained, respectively, and some examples of their application to clinical developments of therapeutic drugs in the infection and cancer fields are introduced. Especially, thanks to the progress of molecular imaging research, a new field of drug development is explored by using imaging biomarkers for efficacy or safety evaluation which visualize biomarkers by PET imaging agents. Finally, the roadmap for drug development in infection and cancer fields utilizing PET molecular imaging is discussed.

Comparison of pharmacokinetics of newly discovered aromatase inhibitors by a cassette microdosing approach in healthy Japanese subjects.

The aim of the present study is to investigate the pharmacokinetics of our newly developed aromatase inhibitors (cetrozole and TMD-322) in healthy subjects by a cassette microdose strategy. A cocktail of cetrozole and TMD-322 was administered intravenously or orally (1.98 µg for each drug) to six healthy volunteers in a crossover fashion. Anastrozole (1.98 µg) was also included in the oral cocktail. Total body clearance and bioavailability were 12.1 ± 7.1 mL/min/kg and 34.9 ± 32.3% for cetrozole, and 16.8 ± 3.5 mL/min/kg and 18.4 ± 12.2% for TMD-322, respectively. The area under the plasma concentration-time curves of cetrozole and TMD-322 after oral administration was markedly lower than that of anastrozole because of their high hepatic clearance. Two subjects out of six exhibited 4- and 17-fold larger exposure of cetrozole than the others following intravenous and oral administration, respectively. Such variation was not observed for TMD-322 and anastrozole. Extensive metabolism of cetrozole and TMD-322 was observed in the CYP2C19 expression system among the test CYP isoforms (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4). We report the first clinical investigation of our aromatase inhibitors by a cassette microdose strategy in healthy Japanese subjects. This strategy offers an optional approach for candidate selection as a phase zero study in drug development.

A purification system for 64Cu produced by a biomedical cyclotron for antibody PET imaging.

Ion exchange is a simple and efficient method for separating no-carrier-added 64Cu from an irradiated Ni target. We developed a semi-automated two-round 64Cu separation system equipped with a strong-base anion exchange resin column. We first verified the efficiency of the system using a non-radioactive substitute consisting of 25 mg of Ni and 127 ng of Cu, and confirmed that Cu was completely eluted at the second round of the separation step. After the bombardment, separation of 64Cu from the Ni target was achieved with high radiochemical purity. 64Cu produced and separated in this study had an extremely low level of Ni impurity. It could be used for labeling monoclonal antibodies for antibody positron emission tomography imaging and synthesizing radiopharmaceuticals.