Panitumumab is a recombinant, fully human IgG2 monoclonal antibody directed against the epidermal growth factor receptor (EGFR). It is indicated for use as monotherapy in the treatment of patients with EGFR-expressing metastatic colorectal cancer after disease progression with standard chemotherapy. The currently indicated dose is 6 mg/kg given every 2 weeks. Panitumumab is mainly distributed into the vascular space and exhibits nonlinear pharmacokinetics that are consistent with target-mediated drug disposition, involving saturable binding to EGFR and subsequent internalization and degradation inside the cells. Panitumumab is also cleared in a linear fashion by the reticuloendothelial system, similarly to other endogenous immunoglobulins. After single-dose administration of panitumumab as a 1-hour intravenous infusion, the area under the serum concentration-time curve increases in a greater-than-dose-proportional manner as the dose increases from 0.75 to 5 mg/kg; however, at doses above 2 mg/kg, the exposure to panitumumab increases in a dose-proportional manner. Panitumumab pharmacokinetics are not meaningfully affected by the tumour type, EGFR membrane expression, tumour KRAS mutation, sex, age, race or renal or hepatic dysfunction. In addition, irinotecan-containing and paclitaxel/carboplatin-containing chemotherapeutic regimens do not appear to affect panitumumab pharmacokinetics. The results of population pharmacokinetic analyses have shown that bodyweight is the most influential covariate on panitumumab exposure, supporting the current use of bodyweight-adjusted doses (mg/kg). The relationship between the weekly dose of panitumumab and skin rash, an on-target pharmacodynamic effect of EGFR inhibition, reaches a plateau at 2.5 mg/kg, indicating that this is the optimal weekly dose. Two less-frequent dosing regimens (6 mg/kg given every 2 weeks and 9 mg/kg given every 3 weeks) achieve steady-state serum trough concentrations similar to those achieved by 2.5 mg/kg given every week, ensuring maximal EGFR coverage. Anti-panitumumab antibody production is uncommon and does not appear to have an impact on the pharmacokinetics of panitumumab.

Introduction: Daratumumab is a first-in-class human anti-CD38 IgG1 monoclonal antibody in clinical development across the multiple myeloma (MM) disease spectrum. A population pharmacokinetics (PK) analysis was conducted (1) to characterize the target-mediated drug disposition (TMDD) and the variability associated with daratumumab disposition, (2) to evaluate the effects of individual demographic characteristics and other factors (e.g., laboratory tests and baseline disease status) on the disposition of daratumumab, (3) to understand daratumumab exposure in special populations (e.g., patients with renal or hepatic impairment and elderly patients), and (4) to predict target saturation and its relationship with daratumumab exposure. Methods: A total of 2,572 daratumumab concentration measurements from 223 patients enrolled in a Phase 1/2 study (GEN501 [NCT00574288]) and a Phase 2 study (MMY2002 [NCT01985126]) were included in the population PK modeling. Daratumumab doses ranged from 0.1 to 24 mg/kg, and 150 of these patients received 16 mg/kg. A mixed-effects 2-compartment pharmacokinetic model based on Michaelis-Menten approximation TMDD was developed. Model-based covariate analyses and simulations were conducted to evaluate the influence of individual characteristics/factors on exposure to daratumumab. Results: The population PK model suggested that the disposition of daratumumab was concentration- and dose-dependent, i.e., lower clearance at higher daratumumab concentrations. The model further revealed that the nonlinear concentration-dependent clearance decreased over time, which could be described as a first-order process. The concentration- and time-dependency of daratumumab clearance suggested that the dynamics of target/tumor burden significantly influenced daratumumab disposition in MM patients. The estimated target binding affinity (ie, concentration at 50% target saturation) was 2.38 µg/mL. The population PK model predicted that a concentration of 21.4 µg/mL and 236 µg/mL would be needed to achieve 90% and 99% target saturation, respectively. The estimated linear clearance (0.17 L/day) was very close to the clearance of non-specific endogenous IgG described in the literature and the volume of distribution of central compartment (V1) approached plasma volume, confirming the robustness of the model. The clearance and V1 of daratumumab significantly increased with increasing body weight. Consequently, exposure to daratumumab was relatively consistent across the range of body weights of MM patients after administration on a mg/kg basis. Age, race, renal impairment, and mild hepatic impairment had neither statistically significant nor clinically relevant effects on exposure to daratumumab. In addition, exposure was consistent across the different subgroups for performance status (ECOG), refractory status, and number of prior lines of therapy. Although baseline albumin levels, type of myeloma (IgG vs non-IgG), sex, and drug products had a statistically significant effect on daratumumab pharmacokinetics, further analyses demonstrated that these covariates had no clinically relevant impact on efficacy or safety profiles. Conclusion: The population PK model revealed a concentration- and time-dependent clearance of daratumumab, suggesting the presence of TMDD. A serum daratumumab concentration of 236 μg/mL was predicted to yield 99% target (CD38) saturation. This analysis suggests that body weight-based dosing is a feasible strategy for MM patients. No clinically relevant demographic or clinical characteristics were identified. Therefore, no dose adjustment based on these factors is recommended. Disclosures Yan: Janssen: Employment. Clemens:Janssen: Employment. Puchalski:Janssen: Employment. Lonial:Novartis: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Onyx: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Lokhorst:Genmab: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Amgen: Honoraria. Orlowski:Millennium Pharaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Onyx Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acetylon Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Array Biopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Spectrum: Research Funding; Biotheryx: Membership on an entity's Board of Directors or advisory committees; Forma Therapeutics: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees. Losic:Genmab A/S: Employment. Khan:Janssen: Employment. Jansson:Janssen: Employment. Ahmadi:Janssen: Employment. Lantz:Janssen: Employment. Perez Ruixo:Janssen: Employment. Zhou:Janssen: Employment. Xu:Janssen: Employment.

Cytoreductive surgery combined with HIPEC is a feasible technique that might increase patient survival. It represents a potential cure for selected patients who have no other alternatives.

A population pharmacokinetic (PK)-pharmacodynamic (PD) model was developed using data from 345 patients with cancer. The population PK-PD model evaluated the effect of erdafitinib total and free plasma concentrations on serum phosphate concentrations after once-daily oral continuous (0.5-12 mg) and intermittent (10-12 mg for 7 days on/7 days off) dosing, and investigated the potential covariates affecting erdafitinib-related changes in serum phosphate levels.Phosphate is used as a biomarker for erdafitinib's efficacy and safety: increases in serum phosphate were observed after dosing with erdafitinib, which were associated with fibroblast growth factor receptor target engagement via inhibition of renal fibroblast growth factor 23-mediated signaling. PK-PD model-based simulations were performed to assess the approved PD-guided dosing algorithm of erdafitinib (8 mg once-daily continuous dosing, with up-titration to 9 mg based on phosphate levels [<5.5 mg/dl] and tolerability at 14-21 days of treatment). The serum phosphate concentrations increased after the first dose and reached near maximal level after 14 days of continuous treatment. Serum phosphate increased with erdafitinib free drug concentrations: doubling the free concentration resulted in a 1.8-fold increase in drug-related phosphate changes. Dose adjustment after at least 14 days of dosing was supported by achievement of >95% maximal serum phosphate concentration. The peak-to-trough fluctuation within a dosing interval was limited for serum phosphate concentrations (5.68-5.65 mg/dl on Day 14), supporting phosphate monitoring at any time relative to dosing. Baseline phosphate was higher in women, otherwise, none of the investigated covariateparameter relationships were considered clinically relevant. Simulations suggest that the starting dose of 8-mg with up-titration to 9-mg on Days 14-21 maximized the number of patients within the target serum phosphate concentrationsThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

A population pharmacokinetic and pharmacodynamic model (PK/PD) of darbepoetin alfa following intravenous (IV) or subcutaneous (SC) administration in participants with chronic kidney disease (CKD) was developed. Darbepoetin alfa concentrations from 96 CKD participants, who received IV or SC darbepoetin alfa, and Hgb concentration from 332 CKD participants not on dialysis, who received SC doses of darbepoetin alfa, were used to develop the PK/PD model. An open 2-compartment model with sequential zero- and first-order absorption was used to characterize darbepoetin alfa pharmacokinetics. Darbepoetin alfa was assumed to trigger concentration-dependent stimulation of production of progenitor cells of red blood cells (RBCs) in bone marrow, which become red blood cells and died after life span expiration. Model evaluation was performed through nonparametric bootstrap and posterior predictive checks. Absolute bioavailability, total mean absorption time, clearance, and volume of distribution were estimated to be 44%, 52 h, 3.4 L/d/70 kg, and 5.9 L/70 kg, respectively. The estimates of drug potency, efficacy, and RBC life span were 0.41 ng/mL, 64%, and 77 days, respectively. Pharmacokinetic or pharmacodynamic parameters of darbepoetin alfa were not affected by age and sex. The qualified model supports the use of darbepoetin alfa administered biweekly (SC) in CKD patients for anemia correction and monthly (SC) for hemoglobin maintenance. In addition, the model is deemed appropriate to conduct simulations to support dose selection for additional clinical studies.