Population Pharmacokinetics and Exposure-Response Analysis of nab-Paclitaxel in Pediatric Patients With Recurrent or Refractory Solid Tumors

Pediatric malignancies are most commonly of primary central nervous system or hematopoietic origin. The main reason for cancer death in pediatrics is refractory and relapsed disease, and improved therapeutic options are needed in the pediatric population. Nanoparticle albumin-bound (nab)-paclitaxel (Abraxane) is a human albumin-stabilized formulation of paclitaxel and was designed to improve the chemotherapeutic effects of paclitaxel and to reduce toxicities. Although nab-paclitaxel pharmacokinetics (PK) has been extensively studied in adults, no information is available on its PK in children. ABI-007-PST-001 was the first nab-paclitaxel clinical trial conducted in pediatrics, and the current analysis is the first study of nab-paclitaxel PK in pediatrics. Our analyses suggested that ontogeny and maturation play a role in nab-paclitaxel PK disposition, as demonstrated by the finding that both blood clearance and volume of distribution increased from younger to older pediatric age groups and from pediatrics to adults. A 3-compartment population PK (PPK) model with saturable elimination was developed to describe the paclitaxel whole blood concentrations in pediatrics. The PPK model was customized by estimating the allometric function on PK parameters to take into account the ontogeny/maturation of patients. PPK estimates are consistent with the fast and deep distribution of paclitaxel that was previously observed in adults. Finally, the exposure-safety analysis showed an increased probability of drug-related adverse events (>grade 2) in cycle 1 and the first cycle of neutropenia (>grade 2) associated with higher doses. However, there is no statistically significant association between exposures (measured by area under the concentration-time curve) and the probabilities of either safety event.

Population Pharmacokinetics and Exposure Response Analysis of Pomalidomide in Subjects With Relapsed or Refractory Multiple Myeloma From the Novel Combination Treatment of Pomalidomide, Bortezomib, and Low-Dose Dexamethasone

Multiple myeloma is an incurable progressive neoplastic disease that accounts for 10% of all hematologic malignancies. Even though significant progress has been made in the treatment of newly diagnosed multiple myeloma, the disease follows a relapsing course in the majority of patients, and there is a need for more effective therapeutic options for the treatment of relapsed or refractory multiple myeloma. CC-4047-MM-005 and CC-4047-MM-007 were phase 1 and 3 studies to evaluate the novel combination of pomalidomide, bortezomib, and low-dose dexamethasone for the treatment of patients with relapsed or refractory multiple myeloma who have already received lenalidomide-based treatments early. This analysis was performed to characterize the population pharmacokinetics (PK) of pomalidomide from the combination treatment and to examine exposure-response relationships. Our analysis showed that pomalidomide concentration-time profiles from the combination treatment were adequately described with a 1-compartment PK model, with first-order absorption and elimination and pomalidomide exhibiting linear and time-invariant PK with moderate variability from the combination treatment. Except for the body surface area, none of the tested covariates had an effect on pomalidomide PK. Although body surface area was identified as a statistically significant covariate of pomalidomide PK, the impact was not deemed clinically relevant. A flat exposure-response curve was observed, consistent with a near-saturated drug effect at the tested exposure range suggesting an appropriately recommended clinical dose of 4 mg of pomalidomide for the combination treatment. Finally, pomalidomide exposure was not associated with higher probabilities of dose interruption during cycle 1 or dose reduction during the treatment period.

Population Pharmacokinetics and Exposure Response Assessment of CC-292, a Potent BTK Inhibitor, in Patients With Chronic Lymphocytic Leukemia

CC‐292, a potent Bruton tyrosine kinase inhibitor, is under development for the treatment of B‐cell malignancies. An analysis was performed to develop a population pharmacokinetic model of CC‐292 and assess the influence of demographics and disease‐related covariates on CC‐292 exposure and to assess the exposure‐response (overall response rate) relationship in patients with chronic lymphocytic leukemia. Population pharmacokinetic analysis was based on a 2‐compartment base model conducted in NONMEM. Categorical exposure‐response analysis was performed using logistic regression in SAS. The population pharmacokinetic analysis results indicated that CC‐292 pharmacokinetic disposition is similar between healthy subjects and patients. CC‐292 showed a larger central compartment volume of distribution than the peripheral compartment volume of distribution (158 L and 72 L, respectively) and a faster clearance than intercompartmental clearance (134 L/h and 18.7 L/h, respectively), indicating that for CC‐292, clearance from blood occurs faster than distribution into deep tissues and organs. CC‐292 clearance is not affected by demographics or baseline clinical lab factors, except for sex. Although sex significantly reduced variation of apparent clearance, the sex effect on apparent clearance is unlikely to be clinically relevant. The exposure‐response analysis suggested that higher drug exposure is linearly correlated with higher overall response rate. A twice‐daily dose regimen showed higher overall response rate as compared to once‐daily dosing, consistent with a threshold concentration of approximately 300 ng/mL, above which the probability of overall response rate significantly increases.