Prediction of renal transporter mediated drug-drug interactions for pemetrexed using physiologically based pharmacokinetic modeling.

Pemetrexed, an anionic anticancer drug with a narrow therapeutic index, is eliminated mainly by active renal tubular secretion. The in vitro to in vivo extrapolation approach used in this work was developed to predict possible drug-drug interactions (DDIs) that may occur after coadministration of pemetrexed and nonsteroidal anti-inflammatory drugs (NSAIDs), and it included in vitro assays, risk assessment models, and physiologically based pharmacokinetic (PBPK) models. The pemetrexed transport and its inhibition parameters by several NSAIDs were quantified using HEK-PEAK cells expressing organic anion transporter (OAT) 3 or OAT4. The NSAIDs were ranked according to their DDI index, calculated as the ratio of their maximum unbound concentration in plasma over the concentration inhibiting 50% (IC50) of active pemetrexed transport. A PBPK model for ibuprofen, the NSAID with the highest DDI index, was built incorporating active renal secretion in Simcyp Simulator. The bottom-up model for pemetrexed underpredicted the clearance by 2-fold. The model we built using a scaling factor of 5.3 for the maximal uptake rate (Vmax) of OAT3, which estimated using plasma concentration profiles from patients given a 10-minute infusion of 500 mg/m(2) of pemetrexed supplemented with folic acid and vitamin B12, recovered the clinical data adequately. The observed/predicted increases in Cmax and the area under the plasma-concentration time curve (AUC0-inf) of pemetrexed when ibuprofen was coadministered were 1.1 and 1.0, respectively. The coadministration of all other NSAIDs was predicted to have no significant impact on the AUC0-inf based on their DDI indexes. The PBPK model reasonably reproduced pemetrexed concentration time profiles in cancer patients and its interaction with ibuprofen.

Assessment of glycemic response to an oral glucokinase activator in a proof of concept study: application of a semi-mechanistic, integrated glucose-insulin-glucagon model.

A proof of concept study was conducted to investigate the safety and tolerability of a novel oral glucokinase activator, LY2599506, during multiple dose administration to healthy volunteers and subjects with Type 2 diabetes mellitus (T2DM). To analyze the study data, a previously established semi-mechanistic integrated glucose-insulin model was extended to include characterization of glucagon dynamics. The model captured endogenous glucose and insulin dynamics, including the amplifying effects of glucose on insulin production and of insulin on glucose elimination, as well as the inhibitory influence of glucose and insulin on hepatic glucose production. The hepatic glucose production in the model was increased by glucagon and glucagon production was inhibited by elevated glucose concentrations. The contribution of exogenous factors to glycemic response, such as ingestion of carbohydrates in meals, was also included in the model. The effect of LY2599506 on glucose homeostasis in subjects with T2DM was investigated by linking a one-compartment, pharmacokinetic model to the semi-mechanistic, integrated glucose-insulin-glucagon system. Drug effects were included on pancreatic insulin secretion and hepatic glucose production. The relationships between LY2599506, glucose, insulin, and glucagon concentrations were described quantitatively and consequently, the improved understanding of the drug-response system could be used to support further clinical study planning during drug development, such as dose selection.

A phase I study of pemetrexed in patients with relapsed or refractory acute leukemia.

PURPOSE: To investigate the toxicity profile, activity, pharmacokinetics, and pharmacodynamics of pemetrexed in leukemia. PATIENTS AND METHODS: Patients with refractory or relapsed acute leukemia were eligible. A phase I 3+3 design was implemented. Pemetrexed was infused intravenously (IV) over 25 min with vitamin supplementation. Courses were repeated every 3 to 4 weeks according to toxicity and efficacy. The starting dose of 900 mg/m² was escalated by approximately 33% until the dose-limiting toxicity (DLT) was determined. RESULTS: Twenty patients with acute myeloid (AML) or lymphocytic (ALL) leukemia received therapy. The main non-hematologic adverse event was liver dysfunction at several dose levels, including 2 DLTs at 3,600 mg/m². One patient with ALL (3,600 mg/m² dose level) achieved a partial response. Pemetrexed pharmacokinetics were linear with escalated dosing. Elevated plasma deoxyuridine was observed in a subset of patients following pemetrexed infusion, but was not correlated with dose levels. Changes in the nucleotide pools of circulating mononuclear cells were observed, but were variable. CONCLUSIONS: The recommended phase II dose of pemetrexed for future leukemia studies is 2,700 mg/m(2) IV over 25 min every 3 to 4 weeks with vitamin supplementation. Deoxyuridine levels did not increase with increasing pemetrexed dose, suggesting pemetrexed inhibition of thymidylate synthase (TS) may be saturated by the 900 mg/m² dose level. However, no firm conclusion can be made regarding TS saturation in tumor cells. While tolerable, pemetrexed monotherapy had limited activity in this highly refractory population. Exploration of pemetrexed in combination with other active agents in leukemia is a reasonable future endeavor.

Phase I and pharmacokinetic study of pemetrexed with high-dose folic acid supplementation or multivitamin supplementation in patients with locally advanced or metastatic cancer.

PURPOSE: This phase I study evaluated the effect of folate supplementation on the toxicity, tolerability, and pharmacokinetics of pemetrexed in patients with locally advanced or metastatic cancer. It also examined two different types of vitamin supplementation and whether the extent of prior myelosuppressive therapy affected pemetrexed tolerability. PATIENTS AND METHODS: Patients received a 10-min infusion of 600 to 14,00 mg/m(2) pemetrexed every 3 weeks. Patients were stratified into cohorts by pretreatment status [lightly pretreated (LPT) or heavily pretreated (HPT)] and were supplemented with intermittent high-dose folic acid (HDFA) or with continuous daily multivitamins (MVI) containing nutritional doses of folic acid. Pemetrexed plasma pharmacokinetics were evaluated for cycle 1. RESULTS: Sixty-two HDFA patients (28 HPT and 34 LPT) were treated with 204 cycles of pemetrexed, and 43 MVI patients (20 HPT and 23 LPT) were treated with 182 cycles. Hematologic dose-limiting toxicities included grade 4 neutropenia (5 of 105 patients), grade 4 thrombocytopenia (4 of 105 patients), and febrile neutropenia (3 of 105 patients). Nonhematologic toxicities included fatigue, vomiting, diarrhea, and nausea. Pemetrexed doses of 800 and 1,050 mg/m(2) were well tolerated when administered with vitamin supplementation to HPT and LPT patients, respectively. There were no clinically relevant differences in toxicities or pemetrexed pharmacokinetics for LPT versus HPT patients or for patients receiving HDFA versus daily MVI supplementation. CONCLUSIONS: The pemetrexed doses tolerated in this study with vitamin supplementation were significantly higher than those tolerated in earlier studies without supplementation, and toxicities were independent of the type of vitamin supplementation or prior myelosuppressive treatment. The recommended dose of pemetrexed is 1,050 mg/m(2) in LPT patients and 800 mg/m(2) in HPT patients, irrespective of the type of vitamin supplementation.

Pemetrexed safety and pharmacokinetics in patients with third-space fluid.

PURPOSE: Pemetrexed is established as first-line treatment with cisplatin for malignant pleural mesothelioma and advanced nonsquamous non-small-cell lung cancer (NSCLC) and as single-agent second-line treatment for nonsquamous NSCLC. Because the structure and pharmacokinetics of pemetrexed are similar to those of methotrexate, and methotrexate is associated with severe toxicity in patients with third-space fluid (TSF), the safety of pemetrexed in patients with TSF was evaluated. EXPERIMENTAL DESIGN: Patients with TSF (pleural effusions, ascites) and relapsed, stage III/IV NSCLC or malignant pleural/peritoneal mesothelioma were treated with pemetrexed (500 mg/m2) on day 1 of each 21-day cycle. TSF was drained at any time only if clinically indicated. Plasma samples were collected during cycles 1 and 2 to compare pemetrexed concentrations with reference data from patients without TSF. RESULTS: Thirty-one patients with TSF received 123 pemetrexed doses (median, 4 cycles per patient; range, 1-11; mean dose intensity, 97.5%). Seven grade 3/4 drug-related toxicities, including four hematologic, were reported; there were no treatment-related deaths. There was no correlation between TSF amount and type, number, and sequelae of toxicities. Pemetrexed plasma concentrations were within the range of those in patients without TSF. Pemetrexed clearance and central volume of distribution were not statistically different between patients with and without TSF. CONCLUSIONS: No clinically relevant alterations of pemetrexed pharmacokinetics occurred in patients with TSF. Pemetrexed was well tolerated; toxicities were expected and manageable. The standard pemetrexed dose recommendations were adequate for patients with TSF in this study. These data suggest that draining TSF before administering pemetrexed is unnecessary.