DM/PK-guided Lead ptimization A Historical Perspective of a Paradigm Shift Dhiren R. Thakker School of Pharmacy UC-Chapel Hill EDMDG Gerald Miwa Retirement Symposium April 9, 2007
Current Paradigm ptimizing Biology and ADME Synchronously C. Breneman, Krisitn Bennett, J. Bi., M. Song, M. Embrechts Rensselaer Polytechnic Institute www.drugmining.com
DM/PK Research Interface at Glaxo Late 1980 s Early 1990 s Clinical DM/PK Preclinical DM/PK Research Safety Assessment Research DM/PK Group
Rapid ffset of Action Within 5 to 10 minutes after the discontinuation of ULTIVA, no residual analgesic activity is present. Ultra Short Acting pioid Remifentanil - Source: Ultiva product label Chemical vs. Enzymatic Hydrolytic Rates
Use of in vitro metabolism screen to identify Metabolic Hot Spot
Rationale for Incorporating Metabolic Studies Early in the Discovery Program Potential metabolic hot spot H H Cl H C β-blockade H Phosphodiesterase Inhibition Dihydropyridazinone DHP-1
PK of Parent and the Amine Metabolite Following ral Administration of DHP-1 (5 mg/kg) to Male Beagle Dog Suggests First Pass Metabolism Serum Conc. (μg/ml) 1.0 0.1 Parent Amine 10 20 30 40 Time (hrs)
Major Metabolite of DHP-1 H H Cl H C H The Amine Metabolite
Relative Rates of In Vitro Metabolism for Dihydropyridazinone Leads Remaining Substrate (%) 100 50 DHP-1 DHP-3 DHP-2 Improved metabolic stability 10 20 30 40 Incubation Time (min)
Functional Group Contributing to the Metabolic Hot Spot for Dihydropyridazinones H H Cl H C DHP-1-like compounds H H H Cl H DHP-2,3-like compounds H
Stabilizing a metabolic hot spot can uncover a secondary hot spot H (CH 2 ) n H R 2 H R 1 H R 3 R 3 secondary C primary Metabolic Hot Spots
Rationally designed in vitro metabolism study, based on a good understanding of likely metabolic pathways, could lead to a rapid solution
Phospholipase A-2 Inhibitors for Inflammatory Diseases (Arthritis, Asthma) Glycerophospholipid derivatives Major problem Poor bioavailability in rats First pass metabolism was implicated absorption (permeability) was not a problem (Caco-2 studies, in vivo studies with radiolabeled compounds) Background
Likely Metabolic Hot Spots Hydrolysis xidation R P -
Evidence for xidative and Hydrolytic Metabolism of the Lead Compound xidative metabolism Incubation with liver homogenates + ADPH Hydrolytic metabolism Incubation with liver homogenates - ADPH
In Vitro Metabolism of the Lead Compound by Rat Liver Enzymes and Caco-2 Cells LIVER HMGEATE 1) ω hydroxylation ester cleavage 2) fatty acid oxidation R P - LIVER HMGEATE & CAC-2 CELLS ester + phosphonate cleavage
Modification of Metabolic Hot Spots F F F F F R P -
In vitro studies do not provide guidance for improving in vivo metabolic clearance A case for n-in-one in vivo PK studies
Dutasteride for BPH The terminal elimination half-life of dutasteride is 5 weeks at steady state Frank Lee et al.
Profile of the Lead Series Alpha-1 antagonists for BPH nce-a-day dosing MW: 400-600, basic, clogp 5-7 Well-absorbed Short half-life Elimination predominantly by metabolism Highly protein bound F F F R 1 S 2 HR
Dog Microsomal Metabolism Screen Poor correlation between in vitro metabolism rate and in vivo T 1/2 or CL Several possible reasons considered» Sequential metabolism» Phase II metabolism» Protein binding Follow-up studies showed that none of these reasons could explain the lack of correlation between in vitro and in vivo studies
PK of Mixtures????? rigin of Cassette Dosing The Challenge Screen over 150 compounds to find a lead appropriate for once-a-day dosing The only predictive screen was in vivo PK in dogs In vivo screen would be too slow The Solution In vivo PK studies of mixtures!!! Judd Berman
Cassette Dosing Validation (5-in-ne) Five compounds of known CL, V SS, and T 1/2 administered concomitantly to a dog Dose=0.25 mg each compound/kg IV» 1/4 th the dose of compounds administered individually Plasma samples assayed by LC/MS/MS» Assay for simultaneous analysis of 5 compounds without interference from any of the metabolites Pharmacokinetic parameters compared to those previously obtained
5-in-ne Dog vs. Individual Dosing Half-life comparison Half-life (hr)--individual Dosing 5 4 3 2 1 0 y = 0.8342x + 0.2875 R 2 = 0.9021 0 1 2 3 4 5 Half-life (hr)--5-in-ne Dosing
-in-one in vivo screen worked Good correlation in PK parameters. Useful for ranking compounds 125 compounds screened in 10 dog studies in 2 months. Approximate structure-pk relationships developed Compounds with a wide range of T 1/2 could be identified from which leads could be selected for further evaluation
Half-lives of 125 Compounds in Dogs as Determined by Cassette Dosing 18 16 Half-life (h) 14 12 10 8 6 F F F R 1 S 2 HR 4 2 0
Acknowledgments Kim Adkison Charley Boehlert Ken Brouwer Lawrence Gan Kathy Halm Frank Lee Diane Levesque Doug Rickert Archie Sinhababu Bob St. Claire Cosette Serabjit-Singh Tim Tippin Steve Unger John Walsh Souzan Yanni Judd Berman Paul Feldman Steve Frye Jeff Leighton Joel Shaffer Elizabeth Sugg Peter Myers Leslie Hudson Gerald Miwa