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Zang R, Barth A, Wong H, Marik J, Shen J, Lade J, Grove K, Durk MR, Parrott N, Rudewicz PJ, Zhao S, Wang T, Yan Z, Zhang D. Design and Measurement of Drug Tissue Concentration Asymmetry and Tissue Exposure-Effect (Tissue PK-PD) Evaluation. J Med Chem 2022; 65:8713-8734. [PMID: 35790118 DOI: 10.1021/acs.jmedchem.2c00502] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The "free drug hypothesis" assumes that, in the absence of transporters, the steady state free plasma concentrations equal to that at the site of action that elicit pharmacologic effects. While it is important to utilize the free drug hypothesis, exceptions exist that the free plasma exposures, either at Cmax, Ctrough, and Caverage, or at other time points, cannot represent the corresponding free tissue concentrations. This "drug concentration asymmetry" in both total and free form can influence drug disposition and pharmacological effects. In this review, we first discuss options to assess total and free drug concentrations in tissues. Then various drug design strategies to achieve concentration asymmetry are presented. Last, the utilities of tissue concentrations in understanding exposure-effect relationships and translational projections to humans are discussed for several therapeutic areas and modalities. A thorough understanding in plasma and tissue exposures correlation with pharmacologic effects can provide insightful guidance to aid drug discovery.
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Affiliation(s)
- Richard Zang
- IDEAYA Biosciences, South San Francisco, California 94080, United States
| | - Aline Barth
- Global Blood Therapeutics, South San Francisco, California 94080, United States
| | - Harvey Wong
- The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Jan Marik
- Genentech, South San Francisco, California 98080, United States
| | - Jie Shen
- AbbVie, Irvine, California 92612, United States
| | - Julie Lade
- Amgen Inc., South San Francisco, California 94080, United States
| | - Kerri Grove
- Novartis, Emeryville, California 94608, United States
| | - Matthew R Durk
- Genentech, South San Francisco, California 98080, United States
| | - Neil Parrott
- Roche Innovation Centre, Basel CH-4070, Switzerland
| | | | | | - Tao Wang
- Coherus BioSciences, Redwood City, California 94605, United States
| | - Zhengyin Yan
- Genentech, South San Francisco, California 98080, United States
| | - Donglu Zhang
- Genentech, South San Francisco, California 98080, United States
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2
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Muglia P, Hannestad J, Brandt C, DeBruyn S, Germani M, Lacroix B, Majoie M, Otoul C, Sciberras D, Steinhoff BJ, Van Laere K, Van Paesschen W, Webster E, Kaminski RM, Werhahn KJ, Toledo M. Padsevonil randomized Phase IIa trial in treatment-resistant focal epilepsy: a translational approach. Brain Commun 2020; 2:fcaa183. [PMID: 33241213 PMCID: PMC7677606 DOI: 10.1093/braincomms/fcaa183] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 09/09/2020] [Accepted: 09/14/2020] [Indexed: 11/13/2022] Open
Abstract
Therapeutic options for patients with treatment-resistant epilepsy represent an important unmet need. Addressing this unmet need was the main factor driving the drug discovery program that led to the synthesis of padsevonil, a first-in-class antiepileptic drug candidate that interacts with two therapeutic targets: synaptic vesicle protein 2 and GABAA receptors. Two PET imaging studies were conducted in healthy volunteers to identify optimal padsevonil target occupancy corresponding to levels associated with effective antiseizure activity in rodent models. Optimal padsevonil occupancy associated with non-clinical efficacy was translatable to humans for both molecular targets: high (>90%), sustained synaptic vesicle protein 2A occupancy and 10-15% transient GABAA receptor occupancy. Rational dose selection enabled clinical evaluation of padsevonil in a Phase IIa proof-of-concept trial (NCT02495844), with a single-dose arm (400 mg bid). Adults with highly treatment-resistant epilepsy, who were experiencing ≥4 focal seizures/week, and had failed to respond to ≥4 antiepileptic drugs, were randomized to receive placebo or padsevonil as add-on to their stable regimen. After a 3-week inpatient double-blind period, all patients received padsevonil during an 8-week outpatient open-label period. The primary endpoint was ≥75% reduction in seizure frequency. Of 55 patients randomized, 50 completed the trial (placebo n = 26; padsevonil n = 24). Their median age was 36 years (range 18-60), and they had been living with epilepsy for an average of 25 years. They were experiencing a median of 10 seizures/week and 75% had failed ≥8 antiepileptic drugs. At the end of the inpatient period, 30.8% of patients on padsevonil and 11.1% on placebo were ≥75% responders (odds ratio 4.14; P = 0.067). Reduction in median weekly seizure frequency was 53.7% and 12.5% with padsevonil and placebo, respectively (unadjusted P = 0.026). At the end of the outpatient period, 31.4% were ≥75% responders and reduction in median seizure frequency was 55.2% (all patients). During the inpatient period, 63.0% of patients on placebo and 85.7% on padsevonil reported treatment-emergent adverse events. Overall, 50 (90.9%) patients who received padsevonil reported treatment-emergent adverse events, most frequently somnolence (45.5%), dizziness (43.6%) and headache (25.5%); only one patient discontinued due to a treatment-emergent adverse event. Padsevonil was associated with a favourable safety profile and displayed clinically meaningful efficacy in patients with treatment-resistant epilepsy. The novel translational approach and the innovative proof-of-concept trial design maximized signal detection in a small patient population in a short duration, expediting antiepileptic drug development for the population with the greatest unmet need in epilepsy.
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Affiliation(s)
| | | | - Christian Brandt
- Department of General Epileptology, Bethel Epilepsy Centre, Mara Hospital, Bielefeld, Germany
| | | | | | | | - Marian Majoie
- Department of Neurology, Academic Center of Epileptology Kempenhaeghe, Maastricht University Medical Centre, Maastricht, The Netherlands
| | | | | | | | - Koen Van Laere
- Department of Imaging and Pathology, KU, Leuven, Belgium
| | | | | | | | | | - Manuel Toledo
- Epilepsy Unit, Department of Neurology, Vall d'Hebron Hospital, Barcelona, Spain
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3
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Goto A, Abe S, Koshiba S, Yamaguchi K, Sato N, Kurahashi Y. Current status and future perspective on preclinical pharmacokinetic and pharmacodynamic (PK/PD) analysis: Survey in Japan pharmaceutical manufacturers association (JPMA). Drug Metab Pharmacokinet 2019; 34:148-154. [PMID: 30827921 DOI: 10.1016/j.dmpk.2019.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 12/24/2018] [Accepted: 01/15/2019] [Indexed: 11/29/2022]
Abstract
Preclinical pharmacokinetic/pharmacodynamic (PK/PD) analysis is an efficient tool for the translational research and proof of mechanism/concept in animals. The questionnaire survey on the practice of preclinical PK/PD analysis was conducted in the member companies of the Japan Pharmaceutical Manufacturers Association (JPMA). According to the survey, 60% of companies conducted preclinical PK/PD analysis and its impact for drug development was different between each of the companies. The frequently analyzed therapeutic areas of preclinical PK/PD analysis were neurology, inflammation and metabolic disease, and those are different from the therapeutic area (infectious disease and oncology) in which PK/PD analysis was considered as effective by the present survey. Many companies which have used preclinical PK/PD analysis for the translation to human PK/PD and for the prediction of dose/regimen had good communication with other research & development (R&D) departments (e.g. pharmacology/clinical pharmacology). The increase in resources for preclinical PK/PD analysis including education was highly demanded. As a future perspective, the closer collaboration between pharmacokinetics scientists, pharmacologists, toxicologists and clinical pharmacologists and the increase in resources including upskilling and the comprehension of preclinical PK/PD analysis by the project team are considered to lead to efficient contributions to improve the success ratio of drug discovery and development.
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Affiliation(s)
- Akihiko Goto
- Non-Clinical Evaluation Expert Committee, Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA), 2-3-11, Nihombashi-honcho, Chuo-ku, Tokyo, 103-0023, Japan; Drug Metabolism and Pharmacokinetics Research Laboratories, Takeda Pharmaceutical Company Limited, 2-26-1, Muraoka-Higashi, Fujisawa, Kanagawa, 251-8555, Japan.
| | - Sadahiro Abe
- Non-Clinical Evaluation Expert Committee, Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA), 2-3-11, Nihombashi-honcho, Chuo-ku, Tokyo, 103-0023, Japan; Clinical Pharmacology, Clinical Research, Pfizer R&D Japan, Inc., Shinjuku Bunka Quint Building, 3-22-7, Yoyogi, Shibuya-ku, Tokyo, 151-8589, Japan
| | - Shoko Koshiba
- Non-Clinical Evaluation Expert Committee, Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA), 2-3-11, Nihombashi-honcho, Chuo-ku, Tokyo, 103-0023, Japan; Pharmacokinetic Research Laboratories, Translational Research Unit, R&D Division, Kyowa Hakko Kirin Co., Ltd., 1188 Shimotogari, Nagaizumi-cho, Sunto-gun, Shizuoka, 411-8731, Japan
| | - Koji Yamaguchi
- Non-Clinical Evaluation Expert Committee, Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA), 2-3-11, Nihombashi-honcho, Chuo-ku, Tokyo, 103-0023, Japan
| | - Nobuo Sato
- Non-Clinical Evaluation Expert Committee, Drug Evaluation Committee, Japan Pharmaceutical Manufacturers Association (JPMA), 2-3-11, Nihombashi-honcho, Chuo-ku, Tokyo, 103-0023, Japan; Pharmacokinetics and Analysis Laboratory, Pharmaceutical Research Center, Meiji Seika Pharma Co., Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama, 222-8567, Japan
| | - Yoshikazu Kurahashi
- Drug Metabolism & Pharmacokinetics Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., 1-1, Murasaki-cho Takatsuki, Osaka, 569-1125, Japan
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Yamamoto Y, Välitalo PA, van den Berg DJ, Hartman R, van den Brink W, Wong YC, Huntjens DR, Proost JH, Vermeulen A, Krauwinkel W, Bakshi S, Aranzana-Climent V, Marchand S, Dahyot-Fizelier C, Couet W, Danhof M, van Hasselt JGC, de Lange ECM. A Generic Multi-Compartmental CNS Distribution Model Structure for 9 Drugs Allows Prediction of Human Brain Target Site Concentrations. Pharm Res 2016; 34:333-351. [PMID: 27864744 PMCID: PMC5236087 DOI: 10.1007/s11095-016-2065-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/07/2016] [Indexed: 12/19/2022]
Abstract
Purpose Predicting target site drug concentration in the brain is of key importance for the successful development of drugs acting on the central nervous system. We propose a generic mathematical model to describe the pharmacokinetics in brain compartments, and apply this model to predict human brain disposition. Methods A mathematical model consisting of several physiological brain compartments in the rat was developed using rich concentration-time profiles from nine structurally diverse drugs in plasma, brain extracellular fluid, and two cerebrospinal fluid compartments. The effect of active drug transporters was also accounted for. Subsequently, the model was translated to predict human concentration-time profiles for acetaminophen and morphine, by scaling or replacing system- and drug-specific parameters in the model. Results A common model structure was identified that adequately described the rat pharmacokinetic profiles for each of the nine drugs across brain compartments, with good precision of structural model parameters (relative standard error <37.5%). The model predicted the human concentration-time profiles in different brain compartments well (symmetric mean absolute percentage error <90%). Conclusions A multi-compartmental brain pharmacokinetic model was developed and its structure could adequately describe data across nine different drugs. The model could be successfully translated to predict human brain concentrations. Electronic supplementary material The online version of this article (doi:10.1007/s11095-016-2065-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yumi Yamamoto
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Pyry A Välitalo
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Dirk-Jan van den Berg
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Robin Hartman
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Willem van den Brink
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Yin Cheong Wong
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Dymphy R Huntjens
- Quantitative Sciences, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium
| | - Johannes H Proost
- Division of Pharmacokinetics, Toxicology and Targeting, University of Groningen, Groningen, The Netherlands
| | - An Vermeulen
- Quantitative Sciences, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium
| | - Walter Krauwinkel
- Department of Clinical Pharmacology & Exploratory Development, Astellas Pharma BV, Leiden, The Netherlands
| | - Suruchi Bakshi
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | | | - Sandrine Marchand
- Department of Medicine and Pharmacy, University of Poitiers, Poitiers, France
| | - Claire Dahyot-Fizelier
- Department of Anaesthesiology and Intensive Care Medicine, University Hospital Center of Poitiers, Poitiers, France
| | - William Couet
- Department of Medicine and Pharmacy, University of Poitiers, Poitiers, France
| | - Meindert Danhof
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Johan G C van Hasselt
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands
| | - Elizabeth C M de Lange
- Division of Pharmacology, Cluster Systems Pharmacology, Leiden Academic Centre for Drug Research, Leiden University, Leiden, The Netherlands.
- Leiden University Gorlaeus Laboratories, Einsteinweg 55, 2333CC, Leiden, The Netherlands.
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5
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Raddad E, Chappell A, Meyer J, Wilson A, Ruegg CE, Tauscher J, Statnick MA, Barth V, Zhang X, Verfaille SJ. Occupancy of Nociceptin/Orphanin FQ Peptide Receptors by the Antagonist LY2940094 in Rats and Healthy Human Subjects. Drug Metab Dispos 2016; 44:1536-42. [DOI: 10.1124/dmd.116.070359] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 06/06/2016] [Indexed: 11/22/2022] Open
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Liu D, Ma X, Liu Y, Zhou H, Shi C, Wu F, Jiang J, Hu P. Quantitative prediction of human pharmacokinetics and pharmacodynamics of imigliptin, a novel DPP-4 inhibitor, using allometric scaling, IVIVE and PK/PD modeling methods. Eur J Pharm Sci 2016; 89:73-82. [PMID: 27108678 DOI: 10.1016/j.ejps.2016.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 04/18/2016] [Accepted: 04/19/2016] [Indexed: 12/14/2022]
Abstract
PURPOSE To predict the pharmacokinetic/pharmacodynamic (PK/PD) profiles of imigliptin, a novel DPP-4 inhibitor, in first-in-human (FIH) study based on the data from preclinical species. METHODS Imigliptin was intravenously and orally administered to rats, dogs, and monkeys to assess their PK/PD properties. DPP-4 activity was the PD biomarker. PK/PD profiles of sitagliptin and alogliptin in rats and humans were obtained and digitized from literatures. PK/PD profiles of all dose levels for each drug in each species were analyzed using modeling approach. Human CL, Vss and PK profiles of imigliptin were then predicted using Allometric Scaling (AS), in vitro in vivo extrapolation (IVIVE), and the steady-state plasma drug concentration - mean residence time (Css-MRT) methods. In vitro EC50 corrected by fu and in vivo EC50 in rats corrected by interspecies difference of sitagliptin and alogliptin were utilized separately to predict imigliptin human EC50. The prediction by integrating all above methods was evaluated by comparing observed and simulated PK/PD profiles in healthy subjects. RESULTS Full PK/PD profiles in animal were summarized for imigliptin, sitagliptin and alogliptin. Imigliptin CL, Vss, and Fa were predicted to be 19.1L/h, 247L, and 0.81 in humans, respectively. Predicted imigliptin AUCs, AUECs, and Emax in humans were within 0.8-1.2 times of observed values whereas other predicted PK/PD parameters were within 0.5-1.5 times of observed values. CONCLUSIONS By integrating available preclinical and clinical data, FIH PK/PD profiles of imigliptin could be accurately predicted.
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Affiliation(s)
- Dongyang Liu
- Clinical Pharmacology Research Center, Peking Union Medical College Hospital and Chinese Academy of Medical Sciences, Beijing, China
| | - Xifeng Ma
- XuanZhu Pharma Co., Ltd., Jinan, Shandong, China
| | - Yang Liu
- Clinical Pharmacology Research Center, Peking Union Medical College Hospital and Chinese Academy of Medical Sciences, Beijing, China
| | - Huimin Zhou
- XuanZhu Pharma Co., Ltd., Jinan, Shandong, China
| | - Chongtie Shi
- XuanZhu Pharma Co., Ltd., Jinan, Shandong, China
| | - Frank Wu
- XuanZhu Pharma Co., Ltd., Jinan, Shandong, China
| | - Ji Jiang
- Clinical Pharmacology Research Center, Peking Union Medical College Hospital and Chinese Academy of Medical Sciences, Beijing, China
| | - Pei Hu
- Clinical Pharmacology Research Center, Peking Union Medical College Hospital and Chinese Academy of Medical Sciences, Beijing, China.
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7
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Development of a Physiologically Based Pharmacokinetic/Pharmacodynamic Model to Predict the Impact of Genetic Polymorphisms on the Pharmacokinetics and Pharmacodynamics Represented by Receptor/Transporter Occupancy of Central Nervous System Drugs. Clin Pharmacokinet 2016; 55:957-69. [DOI: 10.1007/s40262-016-0367-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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8
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Auberson YP, Troxler T, Zhang X, Yang CR, Feuerbach D, Liu YC, Lagu B, Perrone M, Lei L, Shen X, Zhang D, Wang C, Wang TL, Briner K, Bock MG. From ergolines to indoles: improved inhibitors of the human H3 receptor for the treatment of narcolepsy. ChemMedChem 2014; 10:266-75. [PMID: 25394333 DOI: 10.1002/cmdc.201402418] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Indexed: 11/07/2022]
Abstract
Ergolines were recently identified as a novel class of H3 receptor (H3R) inverse agonists. Although their optimization led to drug candidates with encouraging properties for the treatment of narcolepsy, brain penetration remained low. To overcome this issue, ergoline 1 ((6aR,9R,10aR)-4-(2-(dimethylamino)ethyl)-N-phenyl-9-(pyrrolidine-1-carbonyl)-6,6a,8,9,10,10a-hexahydroindolo[4,3-fg]quinoline-7(4H)-carboxamide)) was transformed into a series of indole derivatives with high H3R affinity. These new molecules were profiled by simultaneous determination of their brain receptor occupancy (RO) levels and pharmacodynamic (PD) effects in mice. These efforts culminated in the discovery of 15 m ((R)-1-isopropyl-5-(1-(2-(2-methylpyrrolidin-1-yl)ethyl)-1H-indol-4-yl)pyridin-2(1H)-one), which has an ideal profile showing a strong correlation of PD effects with RO, and no measurable safety liabilities. Its desirably short duration of action was confirmed by electroencephalography (EEG) measurements in rats.
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Affiliation(s)
- Yves P Auberson
- Novartis Institutes for BioMedical Research, Novartis Pharma AG, 4058 Basel (Switzerland).
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9
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Zeiss CJ. Improving the predictive value of interventional animal models data. Drug Discov Today 2014; 20:475-82. [PMID: 25448761 DOI: 10.1016/j.drudis.2014.10.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 10/03/2014] [Accepted: 10/27/2014] [Indexed: 12/15/2022]
Abstract
For many chronic diseases, translational success using the animal model paradigm has reached an impasse. Using Alzheimer's disease as an example, this review employs a networks-based method to assess repeatability of outcomes across species, by intervention and mechanism. Over 75% of animal studies reported an improved outcome. Strain background was a significant potential confounder. Five percent of interventions had been tested across animals and humans, or examined across three or more animal models. Positive outcomes across species emerged for donepezil, memantine and exercise. Repeatable positive outcomes in animals were identified for the amyloid hypothesis and three additional mechanisms. This approach supports in silico reduction of positive outcomes bias in animal studies.
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Affiliation(s)
- Caroline J Zeiss
- Section of Comparative Medicine, Yale University School of Medicine, 375 Congress Ave, New Haven, CT 06520, USA.
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Development of (18)F-labeled radiotracers for neuroreceptor imaging with positron emission tomography. Neurosci Bull 2014; 30:777-811. [PMID: 25172118 DOI: 10.1007/s12264-014-1460-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Accepted: 06/02/2014] [Indexed: 12/14/2022] Open
Abstract
Positron emission tomography (PET) is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide routinely used in the radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109.8 min. The delivery of such radiotracers into the brain provides images of transport, metabolic, and neurotransmission processes on the molecular level. After a short introduction into the principles of PET, this review mainly focuses on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as described here provides molecular probes which not only are useful for imaging of human brain diseases, but also allow molecular neuroreceptor imaging studies in various small-animal models of disease, including genetically-engineered animals. Furthermore, they provide a powerful tool for in vivo pharmacology during the process of pre-clinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the pharmacokinetics and pharmacodynamics of drugs in vivo.
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