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Xceleron - all rights reserved ©2012 Graham Lappin Chief Scientific Officer Xceleron Inc
Xceleron - all rights reserved ©2012 Summary Importance of mAb-target engagement and rate of target production in the body Is the target druggable? Dosing regimen Measurement of target production in the body In the presence of mAb Prior to mAb development IMPACT (Innovative Measurement of Proteins using AMS to Characterise Targets) : a pre-competitive collaboration
Xceleron - all rights reserved ©2012 Target interaction Target Downstream pharmacology
Xceleron - all rights reserved ©2012 Target mediated disposition Jin & Krzyzanski AAPS Pharma Sci 2004: 6 (1) 1-8 Drug- receptor complex Receptor on target K on K off Elimination K elim Therapeutic protein free in plasma Dose Target is neutralised
Xceleron - all rights reserved ©2012 Target Engagement of therapeutic antibody with target mAb Plasma space mAb dosed
Xceleron - all rights reserved ©2012 Target mAb Plasma space mAb dosed Elimination Target unsaturated Engagement of therapeutic antibody with target
Xceleron - all rights reserved ©2012 Target mAb Plasma space mAb dosed Target saturated Elimination In this case dose is based on concentration of target present Engagement of therapeutic antibody with target
Xceleron - all rights reserved ©2012 Target Rate of target production mAb Plasma space Elimination Depending on how quickly the target returns then another dose of mAb required Target re-synthesised The rate of production of target is the more important parameter in setting dose
Xceleron - all rights reserved ©2012 Clarification of terms Rate of target production The amount of target produced in the body and presented to the therapeutic antibody per time. Turnover rate: The amount of target removed versus the rate of target produced per time. Measurement of turnover assumes steady-state conditions apply. Steady-state conditions may not necessarily be present in every case and so to keep the terminology consistent, this presentation will use target production, although purists may point out the error!
Xceleron - all rights reserved ©2012 Target burden Understanding mAb-target engagement is fundamental for biopharmaceuticals Target burden Target engagement Rate of target production Important in ascertaining dose and its regimen Dose required for therapeutic effect Regimen may be unsustainable
Xceleron - all rights reserved ©2012 Target mAb Plasma space mAb dosed Measure free target and drug-target complex over time to obtain information on target production calculated by inference using mathematical model Measuring rate of target production
Xceleron - all rights reserved ©2012 Measuring rate of target production Target production rate measured in presence of mAb Can only be measured once mAb is in the clinic No information on intrinsic target production rate Absence of mAb (ie normal state) Absence of mAb in disease state Target production rate may be unsuitable but only known once in the clinic GMP manufacture of mAb required – which can be expensive
Xceleron - all rights reserved ©2012 Often little to no information on target production rate prior to clinical trials. Only data are on concentration of target Target concentration says nothing about production rate A dose of mAb based purely on existing target concentration can be very misleading For example, low target concentration may lead one to believe a low mAb dose will be sufficient to neutralise If the production rate is high however, the low dose of mAb may be swept away by newly generated target The amount of mAb required for some targets may be excessive One case of a required dose of 10mg/kg/day! to neutralise the target Measuring rate of target production
Xceleron - all rights reserved ©2012 Early target production data Intrinsic target production rate (in absence or mAb) might indicate if target is druggable Target production rate in healthy and disease state is also useful in assessing target druggability Animal models useful but data in humans more reliable Target production rate in pathological state particularly useful In vitro will give information on mAb-target interaction but not on target production rate in vivo Targets can be proteins or even cell populations. Cell-tracking studies can be very informative but also challenging to perform
Xceleron - all rights reserved ©2012 Measuring target production prior to mAb manufacture To measure target production rate of any biological entity (small molecule, protein or cell population) the target has to be labelled, typically isotopically The clearance of the label is measured (using an isotopic assay) The total amount of target is measured Target production rate (turnover - more accurately in this case) is the product of isotopic clearance and total target concentration
Xceleron - all rights reserved ©2012 Target production rate Plasma space Measure total concentration of target
Xceleron - all rights reserved ©2012 Plasma space Measure presence of labelled target over time to calculate clearance Measure total concentration of target Target production rate
Xceleron - all rights reserved ©2012 Labelling targets Classical labels are high specific activity (short half-life) radioisotopes – 125 I 99m Tc Short half-lives limit duration of experiments 125 I t ½ = 60.25 days 99m Tc t ½ = 6 hours If administered to humans, radioactive burden can be high For small molecules 14 C is the isotope of choice 14 C t ½ = 5760 years, so sensitivity is problematic for large molecules
Xceleron - all rights reserved ©2012 Using 14 C to label proteins 14 C is a long half-life and so few time restrictions experimentally Low energy ß-emitter Lower radioactive burden for human subjects 125 I in particular requires iodine wash-out Reduced autoradiolysis Fewer safety issues in laboratory handling But scintillation assay sensitivity with 14 C and large molecules problematic Requires a highly sensitive 14 C assay : accelerator mass spectrometry (AMS)
Xceleron - all rights reserved ©2012 AMS is exquisitely sensitive to 14 C AMS Atoms separated 12 C, 13 C and 14 C atoms individually counted by differences in mass/charge and energy -Decay of 14 C atom Detected by scintillation counting as photons of light in photomultiplier tube 0.012% of 14 C decays per annum; 2.3 billion 14 C atoms 1 dpm Key Sample containing 12 C 13 C and 14 C atoms 1000 14 C atoms required for valid measurement Scintillation counting
Xceleron - all rights reserved ©2012 AMS instrument 250kV AMS based at Xceleron, Germantown, Maryland
Xceleron - all rights reserved ©2012 14 C-targets and AMS Labelling of mAb 14 C 13 C Bioactivity assay Analysis MALDI-TOF-MS (using 13 C as marker) SDS-PAGE Target administered to humans. Very low levels of radioactivity (classified as non-radioactive study) Very low mass of target so as not to perturb naturally occurring pool
Xceleron - all rights reserved ©2012 Announcement of IMPACT A pre-competitive research collaboration between Xceleron, Hammersmith Medicines Research and the Biopharma Industry Two targets as examples to demonstrate the technique TNF- T-lymphocytes IMPACT is a proposed programme of work, supported by a consortium of Biopharma companies
Xceleron - all rights reserved ©2012 Therapeutic proteins for treatment of rheumatoid arthritis (RA) AgentType AdalimumabRecombinant human IgG1 mAb EtanerceptSoluble TNF-receptor fusion protein InfliximabChimeric IgG1 CertolizumabRecombinant humanised Fab fragment of anti-TNF-antibody coupled to PEG GolimumabRecombinant human IgG1 mAb Target TNF-
Xceleron - all rights reserved ©2012 Some targets in rheumatoid arthritis T-cell Activated macrophage Cytokines TNF- Osteoclasts Synovial tissue Adalimumab Etanercept Infliximab Certolizumab Golimumab Abatacept Scott (2012) Clin Pharm Ther 91(1) 30-43 Inflammation
Xceleron - all rights reserved ©2012 IMPACT: measurement of TNF- production Healthy volunteers 14 C-TNF- lipopolysaccharide (LPS) challenge RA patients Samples of plasma and a limited number of synovial fluid samples over time Measure total TNF- and 14 C-TNF to calculate target production rate
Xceleron - all rights reserved ©2012 TNF- AMS assay Size exclusion SDS-PAGE Assay specificity – probably better than ELISA Assay sensitivity likely to be at least 2 orders of magnitude better than ELISA
Xceleron - all rights reserved ©2012 Rate of target production in healthy volunteers and in disease state TNF- already an established target but shows proof of concept Nevertheless rates of production of TNF- in the absence of a therapeutic antibody have not been fully investigated Data can be used retrospectively – ie what information would it provide on doses and dose regimens in the context of known effective therapeutic treatments Data outputs
Xceleron - all rights reserved ©2012 IMPACT: cell tracking studies 99m Tc Cell tracking studies (plasma lymph) Half-life of 99m Tc = 6 h Interference with the cell? Radiolytic stability? 14 C Half-life 14 C = 5760 years Interference with cell less likely Likely to be radiolytically more stable Low radioactive burden in humans. Track cells in plasma and lymph (or anywhere a sample can be taken) by measurement of 14 C with AMS
Xceleron - all rights reserved ©2012 T-Cell assay Blood sample Cell separation 14 C-labelling AMS Blood lymph etc
Xceleron - all rights reserved ©2012 Rate of T-cell production and transfer between circulation and lymph Comparison with 99m Tc studies – are they reliable? Longer-term tracking from systemic to lymph and perhaps back again? Data outputs
Xceleron - all rights reserved ©2012 Conclusions Target production rate is important in assessing the druggability of the target and the dosing regimen Usually measured via mAb-target complex and modelling, after target selection and manufacture of mAb for clinic 14 C-labelling and AMS allows target production rate to be measured prior to mAb development Intrinsic target production rate in healthy and disease state possible IMPACT: pre-competitive collaboration to develop methods to measure intrinsic target production rate in humans prior to full antibody development
Xceleron - all rights reserved ©2012 Joe Balthasar (University at Buffalo) Malcolm Boyce, Hammersmith Medicines Research, London Members and potential members of the biopharma consortium Acknowledgements Questions gratefully received Graham Lappin Xceleron Inc firstname.lastname@example.org
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