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Ustekinumab exposure and fecal-calprotectin turnover

Conditional ustekinumab distribution, latent p40 binding and target-dependent fecal-calprotectin turnover in fixed research profiles.

Ustekinumab Dosing Individualization in Crohn’s Disease Guided by a Population Pharmacokinetic–Pharmacodynamic Model ↗
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How do the fixed ustekinumab schedules change concentration and response?

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390 mg IV induction, 90 mg SC every 8 weeks

Follow a fixed induction at day 0 and SC doses at days 56, 112 and 168.

0–224 d

Scenario details

390 mg IV induction, 90 mg SC every 8 weeks

Follow a fixed induction at day 0 and SC doses at days 56, 112 and 168.

Readouts

Free central ustekinumab · nmol/L
Algebraic free central drug concentration. Multiply nmol/L by 0.149 for mg/L for a 149 kDa antibody.
Fecal calprotectin · mg/kg
Biomarker concentration in mg/kg; a 100 mg/kg threshold is biochemical, not an endoscopic endpoint.
Free latent central P40 · nmol/L
Algebraic unbound target concentration; p40 was not measured in the source cohort.
Accounted drug amount · nmol
Depot plus central drug plus peripheral drug plus accumulated drug loss, compared with bioavailable delivered input at the same event side.
Target amount ledger · nmol
Central target amount plus peripheral target amount plus accumulated target loss minus accumulated target synthesis; initialized to the baseline target pool.

Study purpose

  • Follow a fixed induction at day 0 and SC doses at days 56, 112 and 168.

Assumptions

  • Interpret patterns within this model and starting configuration; do not treat them as clinical predictions or treatment recommendations.

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Simulation time
d
d
224 → 168

Time between reported samples.

d
0.25 → 1

2 changes · Variation 1

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Biology

Conditional ustekinumab distribution, latent p40 binding and target-dependent fecal-calprotectin turnover in fixed research profiles.

Conditional ustekinumab distribution, latent p40 binding and target-dependent fecal-calprotectin turnover in fixed research profiles.

Model details

16 parameters · 10 states · 10 equations · 12 derived outputs

Classification & API access
Therapeutic
ustekinumab
Modality
Monoclonal antibody
Target
IL-12, IL-23 p40
Disease / scope
Crohn disease, fixed research profiles
ParameterDefaultUnitDescription
C50c502.46nmol/LFree-target concentration giving half the maximum production stimulation. Fixed with its matched scenario context.
Systemic clearancecl0.277L/dClearance multiplying free central drug concentration. Fixed with its matched scenario context.
Maximum effectemax2.19—Maximum fractional stimulation of fecal-calprotectin production. Fixed with its matched scenario context.
FC0fc0213mg/kgFecal-calprotectin baseline used jointly with target equilibrium initialization. Fixed with its matched scenario context.
Absorption rate constantka0.3811/dFirst-order absorption from the bioavailable SC depot. Fixed with its matched scenario context.
Dissociation constantkd0.168nmol/LQuasi-equilibrium drug-target dissociation concentration. Fixed with its matched scenario context.
Degradation ratekdeg9.26e-101/dFirst-order degradation of unbound central latent target. Fixed with its matched scenario context.
Target internalization ratekint0.000002831/dFirst-order internalization of drug-target complex. Fixed with its matched scenario context.
Turnover loss ratekout0.05811/dFirst-order fecal-calprotectin turnover. Fixed with its matched scenario context.
Target synthesis rateksyn9.86e-9nmol/L/dZero-order synthesis of total central latent p40 concentration. Fixed with its matched scenario context.
Intercompartmental clearanceq1.89L/dReversible exchange of free drug between central and peripheral drug spaces. Fixed with its matched scenario context.
Qtqt0.493L/dReversible exchange of free target between its apparent central and peripheral spaces. Fixed with its matched scenario context.
Central distribution volumevc3.57LApparent volume defining total central drug concentration and complex-mediated drug loss. Fixed with its matched scenario context.
Vctvct2.44LApparent target volume used for central target exchange and the target amount ledger. Fixed with its matched scenario context.
Peripheral distribution volumevp3.3LApparent volume defining free peripheral drug concentration. Fixed with its matched scenario context.
Vptvpt11LApparent volume defining free peripheral target concentration. Fixed with its matched scenario context.

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