Ustekinumab
Ustekinumab, a biologic. Fully human IgG1κ mAb binding the p40 subunit common to IL-12 and IL-23 → blocks both Th1 (IFN-γ) and Th17… Subcutaneous half-life 21 d.
Fully human IgG1κ mAb binding the p40 subunit common to IL-12 and IL-23 → blocks both Th1 (IFN-γ) and Th17 (IL-17) axes by preventing receptor engagement. Approved for plaque psoriasis (first p40 blocker), PsA, Crohn's disease, and UC. Low immunogenicity and q8–12w dosing make it a favoured choice for IBD.
PK: ABSORPTION RATE AUTHORED FROM A VERBATIM PEAK TIME. This row carried no ka, so the solver substituted 1.0/h and the modelled peak landed at 6.6 h — for a slowly-absorbed subcutaneous product that is wrong by design, not by a little. Source: "corresponding to the Cmax (tmax) was 4.0-8.5 days" across Chinese and non-Chinese subjects. RANGE: the shorter endpoint is taken, which moves the curve partway to the truth and cannot overshoot. With the stored half-life fixing ke, Tmax solves uniquely for ka by inverting the model own definition, ln(ka/ke)/(ka-ke) = Tmax — ARITHMETIC, NOT AN ESTIMATE — giving 0.03513/h, which reproduces 96 h on substitution. EXPOSURE IS UNCHANGED: the absorption rate cancels out of AUC entirely, so only the shape moves.
Pharmacokinetics
- Subcutaneous — t½ 21.0 d · F 57% · ka 0.03513 h⁻¹ · Vd 7.7 L
- IV — t½ 21.0 d · F 100% · Vd 7.7 L
Sources: PMID:21084039, PMID:34460338, PMID:23512638