Distribution, metabolism and pharmacokinetics of drugs

Research

It is now well recognised that the selection of robust candidates from lead optimisation programmes requires a balance of good potency, safety and drug metabolism and pharmacokinetic (DMPK) properties. These compound characteristics should be optimised as early as possible in the drug discovery process so that cycle times and progression to humans is as uneventful as possible. My group has implemented industry standard assays coupled with state of the art UPLCMSMS technology for supporting hit to lead and lead optimisation programmes. Our capabilities include in silico absorption, distribution, metabolism and excretion (ADME) models, together with a range of in vitro and in vivo tools, selected in order to provide a good overall assessment of the developability profile of compounds early in the optimisation process.   

Our available in vitro assays include assessment of metabolic stability (intrinsic clearance) using liver microsomes, hepatocytes or cytosol from a range of preclinical species and human; assessment of drug-drug interaction and bioactivation risk using human liver microsomes, evaluating CYP450 inhibition, metabolism dependent inhibition, glutathione trapping and performing reaction phenotyping to give a preliminary understanding of the enzymology involved in the metabolism of a new compound; aqueous and simulated gastric fluid (SGF) solubility using nephelometry; determination of compound stability in different matrices (blood, SGF, buffer etc) and plasma protein and brain tissue binding determination using equilibrium dialysis in a 96-well format. Assessing plasma protein and brain tissue binding allows for correction to the free plasma and free brain concentration, both of which may be more meaningful indicators of the true efficacious concentration of a compound and so aid in understanding of pharmacokinetic/pharmacodynamic (PK/PD) relationships and, through calculation of theoretical receptor occupancy, enable better initial design of pharmacodynamic (PD) experiments.

Together with these in vitro assays, my group, on a routine basis, performs in vivo pharmacokinetics (PK), and brain penetration studies in rodents, usually mice. My in vivo pharmacologists have the expertise to perform serial blood sampling in mice so that a full PK profile can be obtained from a single animal.  Additionally they can perform in vivo assessment of Pgp interaction using mdr1a deficient mice; hepatic portal vein sampling in rats in order to obtain information on fraction absorbed and hepatic extraction that can aid in more rapidly identifying the key issues for poor bioavailability and can provide PK/PD support using oral and/or a number of parenteral dose routes (i.v., s.c., i.p., i.m) as required to determine drug exposure in order to ensure optimal PD study design and build a better understanding of the PK/PD relationship within projects.

Our capability to perform metabolite identification from in vitro incubates or from biological matrices obtained following in vivo PK experiments has recently been enhanced through purchase of a UPLC Xevo Qtof MSMS.

My group is also responsible for running the animal efficacy studies in support of all our neglected tropical disease programmes. This allows a more nimble progression through to in vivo efficacy if a compound is identified as having appropriate pharmacokinetics to deliver efficacy at a well tolerated dose.  Furthermore, with the need to rapidly validate targets in vivo, we use, when viable, HRN^TM (CYP450 hepatic null) mice and/or implanted osmotic pumps in efficacy studies on those targets with poorly optimized chemistry in order to achieve and maintain prolonged efficacious free concentration of a compound in a mouse without the need for compound optimisation apriori.

Teaching

Publications

1. Polli JW, Humphreys JE, Wring SA, Burnette TC, Read KD, Hersey A, Butina D, Bertolotti L, Pugnaghi F and Serabjit-Singh CS (2000) A comparison of MDCK and bovine brain endothelial cells (BBECs) as a blood-brain barrier screen in early drug discovery.  In Progress in Reduction, Refinement and Replacement of Animal Experimentation (M.Balls, A.M Van Zeller and M. Halder, eds), Elsevier, New York, p271-289
2. Abbott NJ, Reichel A, Chishty M, Read KD, Taylor JA and Begley DJ (2001) Measurement and prediction of blood-brain barrier permeability: In vivo, in silico and in vitro approaches.  In blood-brain barrier delivery and brain pathology (D. Kobiler and S. Lustig, eds), Kluwer Academic/Plenum Publishers
3. Polli JW, Baughman TM, Humphreys JE, Jordan KH, Mote AL, Webster LO,Barnaby RJ, Vitulli G, Bertolotti L, Read KD and Serabjit-Singh CS (2004)
4. The systemic exposure of an N-methyl-D-aspartate receptor antagonist is limited in mice by the P-glycoprotein and breast cancer resistance protein efflux transporters. Drug Metabolism and Disposition 32 (7), 722-726
5. Schaddelee MP, Read KD, Cleypool CGJ, Ijzerman AP, Danhof M and de Boer, AG. (2005). Brain penetration of synthetic adenosine A1 receptor agonists in situ: Role of the rENT1 nucleoside transporter and binding to blood constituents. Eur. J. Pharm. Sci. 24, 59-66
6. Summerfield S, Read KD, Begley DJ, Obradovic T, Hidalgo IJ, Coggon S, Lewis         AV, Porter RA and Jeffrey P. (2007). Central nervous system drug disposition: The relationship between in situ brain permeability and brain free fraction. JPET 322, 205-213
7. Gunn RN, Summerfield SG, Salinas C, Read KR, Searle G, Ruffo AD, Parker C, Stevens AJ, Bonasea T, Jeffrey PM and Laruelle MA (2007). Combining PET and equilibrium dialysis to assess blood-brain barrier transport. J. Cerebral Blood Flow and Metabolism 27, (SUPPL.1), P004-014
8. Charlton ST, Whetstone J, Fayinka ST, Read KD, Illum L and Davis SS (2008). Evaluation of the mechanism of direct transport of glycine receptor antagonists and an angiotensin antagonist from the nasal cavity to the central nervous system. Pharm. Res. 25 (7), 1531-1543
9. Summerfield SG, Lucas AJ, Porter RA, Jeffrey P, Gunn RN, Read KR, Stevens AJ, Metcalf AC, Osuna MC, Kilford PJ, Passchier J and Ruffo AD (2008). Toward an Improved Prediction of Human in vivo Brain Penetration. Xenobiotica 38(12), 1518-1535
10. Watson JM, Wright S, Lucas A, Clarke KL, Viggers J, Cheetham S, Jeffrey P, Porter RA and Read KD (2009). Receptor occupancy and brain free fraction. Drug Metabolism and Disposition 37, 753-760
11. Large CH, Kalinichev M, Lucas A, Carignani C, Bradford A,  Garbati N, Sartori I, Austin N, Ruffo A, Jones DNC, Alvaro G and Read KD (2009). The relationship between sodium channel inhibition and anticonvulsant activity in a model of generalised seizure in the rat. Epilepsy Research, 85 (1), 96-106
12. Read KD and Braggio S (2010). Assessing brain free fraction in early drug discovery. Expert Opin. Drug Metab. Toxicol. 6 (3), 337-344
13. Frearson JA, Brand S, McElroy SP, Cleghorn LAT,  Smid O,  Stojanovski L, Price HP, Guther MLS, Torrie LS, Robinson DA, Hallyburton I, Mpamhanga CP, Brannigan JA, Wilkinson AJ, Hodgkinson M, Hui R, Qiu W, Raimi OG, Van Aalten DMF, Brenk R, Gilbert IH, Read KD, Fairlamb AH, Ferguson MAJ, Smith DF,  Wyatt PG (2010). N-myristoyltransferase inhibitors as new leads to treat sleeping sickness. Nature, 464, 728-732.
14. Micheli M, Cavanni P, Arban R, Benedetti R, Bertani B, Bettati M, Bettelini L, Bonanomi G, Braggio S, Checchia A, Davalli S, Di Fabio R, Fazzolari E, Fontana S, Marchioro C, Minick D, Negri M, Oliosi B, Read KD, Sartori I, Tedesco G, Tarsi L, Terreni S,Visentini F, Zocchi A and Zonzini L (2010). 1-(Aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes and 6-(Aryl)-6-[alkoxyalkyl]-3 azabicyclo[3.1.0]hexanes: a new series of potent and selective triple re-uptake inhibitors. J.Med. Chem. 53(6), 2534-2551
15. Kalinichev M, Bradford A, Bison S, Lucas A, Sartori I, Garbati N, Andreetta F, Bate S, Austin NE, Jones DNC, Read KD, Alvaro G and Large CH (2010). Potentiation of the anticonvulsant efficacy of sodium channel blockers by an NK1 receptor antagonist in the rat. Epilepsia, 51(8), 1543-1551
16. Sokolova A, Wyllie S, Patterson S, Oza SL, Read KD and Fairlamb AH (2010). Cross-resistance to nitro drugs and implications for treatment of human African trypanosomiasis. Antimicrobial Agents and Chemotherapy 54(7), 2893-2900
17. Ruda GF, Wong PE, Alibu VP, Norval S, Read KD, Barrett MP and Gilbert IH (2010). Aryl Phosphoramidates of 5-phosho erythronohydroxamic acid, a new class of potent trypanocidal agents.  J. Med. Chem. 53(16), 6071-6078
18. Micheli F, Cavanni P, Andreotti D, Arban R, Benedetti R, Bertani B, Bettati M, Bettelini L, Bonanomi G, Braggio S, Carletti R, Checchia A, Corsi M, Fazzolari E, Fontana S, Marchioro C, Merlo-Pich E, Negri M, Oliosi B, Ratti E, Read KD, Roscic M, Sartori I, Spada S, Tedesco G, Tarsi L, Terreni S, Visentini F, Zocchi A, Zonzini L and Di Fabio R (2010). 6-(3,4-dichlorophenyl)-1-[(methyloxy)methyl]-3-azabicyclo[4.1.0]heptane: A new potent and selective triple reuptake inhibitor. J.Med.Chem 53 (13), 4989-5001
19. Jones DC, Hallyburton I, Stojanovski L, Read KD, Frearson JA and Fairlamb AH (2010). Identification of a k-opioid agonist as a potent and selective lead for drug development against human African trypanosomiasis.  Biochem. Pharmacol. 80 (10), 1478-1486
20. Dorfmueller HC, Borodkin VS, Schimpl M, Zheng X, Kime R, Read KD and Van Aalten  DMF (2010). Cell penetrant nanomolar 0-GlcNAcase inhibitors selective against lysosomal hexosaminidases. Chemistry and Biology 17 (11), 1250-1255