Metabolism and excretion of a novel p38 MAP kinase inhibitor pamapimod in healthy male subjects.

OBJECTIVE: This study investigated the pharmacokinetics, excretion, and metabolism of pamapimod following a single oral dose in healthy male subjects. MATERIALS: Nonradio-labeled pamapimod was supplied as bulk powder, [14C]-labeled pamapimod was supplied as ethanol solution. Pamapimod, metabolic synthetic standards, and the internal standard were supplied by Roche. METHODS: This was an open-label, singledose mass balance study. Healthy male subjects received a single oral dose of 300 mg [14C]-labeled pamapimod. Quantification of pamapimod and metabolites was determined by a validated liquid chromatography/tandem mass spectrometry method (LC/MS/ MS). Urine, blood, and feces were collected for metabolic profiling and radioactivity analysis. Profiling was done using high performance liquid chromatography (HPLC)/ LC/MS/MS. Radioactivity determination was by liquid scintillation counting. RESULTS: Six subjects completed the study. Mean Cmax was 4,120 ng/ml at tmax of 2.8 h, and mean AUCinf was 19,800 ng·h/ml. The t1/2 of pamapimod was 7.2 h. Mean drug recovery was 100 ± 2% by 120 h, of which 76.5% was recovered in urine and 23.9% in feces. Unchanged pamapimod accounted for 15.3% excreta, indicating metabolism is the major elimination pathway. Five metabolites were identified in plasma, urine, and feces. In urine, 41.1% of the dose was excreted as carboxylate metabolite (RO4498496), 19.2% as lactol metabolite (RO4493992), and 12.5% as pamapimod. In feces, 18.5% was excreted as RO4498496, 2.8% as pamapimod. CONCLUSIONS: The majority of dose was renally cleared. Urinary and fecal metabolites accounted for > 80% radioactivity. These results indicate hepatic metabolism followed by renal excretion is the major elimination pathway of pamapimod.

A phase Ib dose-escalation study of erlotinib, capecitabine and oxaliplatin in metastatic colorectal cancer patients.

BACKGROUND: Dysregulation of the epidermal growth factor receptor (HER1/EGFR) has been reported in colorectal cancer (CRC). Erlotinib is a potent inhibitor of HER1/EGFR-mediated signaling. This trial of patients with metastatic CRC (MCRC) examined the safety, maximum tolerated dose (MTD) and pharmacokinetics (PK) of erlotinib in combination with capecitabine and oxaliplatin (XELOX), a regimen with established efficacy. PATIENTS AND METHODS: Patients previously untreated or treated with one line of 5-fluorouracil and/or irinotecan received escalating oral doses of erlotinib (daily), capecitabine (days 1-14) and i.v. oxaliplatin (day 1 of a 21-day cycle). RESULTS: The first six patients in cohort 1 (erlotinib 100 mg/day, capecitabine 825 mg/m(2) twice daily, oxaliplatin 130 mg/m(2)) had no dose-limiting toxicities (DLTs). In cohort 2 (capecitabine increased to 1000 mg/m(2) twice daily), two of six patients had DLTs. When cohort 2 was expanded to 11 patients two further DLTs occurred, exceeding the definition of MTD. Cohort 1 was expanded to 12 patients, and no DLTs occurred. The most common adverse events (AEs) were diarrhea and rash. There was a trend for reduced capecitabine concentrations in the presence of erlotinib. While this was not statistically significant, the possibility of an interaction affecting capecitabine PK cannot be excluded. Antitumor activity was observed in both cohorts (one complete and four partial responses, and stable disease in 11 patients). CONCLUSION: The MTD for this combination in MCRC is capecitabine 825 mg/m(2) twice daily days 1-14, oxaliplatin 130 mg/m(2) day 1 and erlotinib 100 mg/day of a 21-day cycle. The combination was well tolerated at the MTD, with no unexpected AEs. The use of this combination in MCRC warrants further investigation.

Phase I trial of 40-kd branched pegylated interferon alfa-2a for patients with advanced renal cell carcinoma.

PURPOSE: Pegylated (40 kd) interferon alfa-2a (IFNalpha2a) (PEGASYS, Hoffman-La Roche, Nutley, NJ; PEG-IFN) is a modified form of recombinant human IFNalpha2a with sustained absorption and prolonged half-life after subcutaneous administration. A phase I study of PEG-IFN with pharmacokinetic and pharmacodynamic evaluations was conducted in previously untreated patients with advanced renal cell carcinoma (RCC). PATIENTS AND METHODS: Twenty-seven patients were enrolled onto cohorts of three or six patients. PEG-IFN was administered on a weekly basis by subcutaneous injection. The dose was escalated from 180 microg/wk to a maximum of 540 microg/wk in 90-microg increments. Serial venous blood samples were drawn to assess concentrations of PEG-IFN and two immunologic surrogates, neopterin and 2'-5' oligoadenylate synthetase (OAS). RESULTS: The maximum-tolerated dose was determined as 540 microg/wk, because two patients experienced dose-limiting toxicity within 28 days of starting treatment. One developed serum grade 3 ALT elevation, and a second developed grade 3 fatigue. Six patients were treated at 450 microg/wk without dose-limiting toxicity. Over the course of treatment, the side-effect profile was mostly mild to moderate in intensity. Adverse events included fatigue, fever, headache, myalgia, nausea, and decreased appetite. Five patients (19%) achieved a partial response. The mean maximum serum concentration increased from 5.0 to 27 ng/mL, and mean area under the curve increased from 247 to 2,981 ng/h/mL, with dose escalation from 180 microg/wk to 540 microg/wk. Serum concentration of PEG-IFN was sustained at close to peak during the dosing interval, and steady-state was achieved in approximately 5 weeks. The immunologic surrogates, neopterin and OAS, were induced at all doses with a sustained concentration profile similar to PEG-IFN. CONCLUSION: PEG-IFN is a modified form of IFNalpha2a with distinct pharmacokinetic advantages and immunomodulatory and antitumor activity for patients with advanced RCC. A dose of 450 microg/wk by subcutaneous administration was determined as a suitable dose for further study. PEG-IFN is more convenient to administer than IFNalpha and has potential for increased efficacy, less toxicity, or both. The efficacy and toxicity of PEG-IFN will be further assessed in clinical trials and compared with IFNalpha.

Down-regulation of the pharmacokinetic-pharmacodynamic response to interleukin-12 during long-term administration to patients with renal cell carcinoma and evaluation of the mechanism of this "adaptive response" in mice.

BACKGROUND: Interleukin-12 (IL-12) is a cytokine that promotes type-1 helper T-cell responses and may have therapeutic utility in the treatment of cancer, asthma, and a variety of infectious diseases. METHODS: In a phase I trial, recombinant human IL-12 (rHuIL-12) was administered subcutaneously once a week at a fixed dose of 0.1 to 1.0 microg/kg to 24 patients with renal cell carcinoma. A similar study was later performed in mice to evaluate the mechanism of down-regulation of pharmacokinetic-pharmacodynamic response observed in patients with cancer. RESULTS: Adverse events, serum IL-12 levels, and serum levels of interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) produced in response to IL- 12 were all maximum in the week after the first dose of rHuIL-12 and decreased after long-term administration. Similar to these results, repetitive subcutaneous administration of recombinant mouse IL-12 (rMoIL-12) to normal mice led to down-regulation of serum levels of IL-12 and IFN-gamma measured 5 hours after rMoIL-12 injection. Down-regulation of IL-12 serum levels was inversely correlated with the up-regulation of IL-12 receptor expression and may be the result of increased clearance of rMoIL-12 from serum by binding to lymphoid cells expressing increased amounts of IL-12 receptor. The down-regulation of serum IFN-gamma levels correlated with decreased IFN-gamma messenger ribonucleic acid expression and may result from feedback inhibition of IL-12 signaling or from a more specific inhibition of IFN-gamma synthesis. CONCLUSION: Administration of rHuIL-12 in fixed weekly doses resulted in decreased serum levels of IL-12 and of IFN-gamma, a secondary cytokine believed to be critical to response of IL-12. A better understanding of the complex regulation of the pharmacokinetic-pharmacodynamic response to IL-12 should facilitate the development of more effective dosing regimens for its use in the clinic.

Characterization of AUCs from sparsely sampled populations in toxicology studies.

PURPOSE: The objective of this work was to develop and validate blood sampling schemes for accurate AUC determination from a few samples (sparse sampling). This will enable AUC determination directly in toxicology studies, without the need to utilize a large number of animals. METHODS: Sparse sampling schemes were developed using plasma concentration-time (Cp-t) data in rats from toxicokinetic (TK) studies with the antiepileptic felbamate (F) and the antihistamine loratadine (L); Cp-t data at 13-16 time-points (N = 4 or 5 rats/time-point) were available for F, L and its active circulating metabolite descarboethoxyloratadine (DCL). AUCs were determined using the full profile and from 5 investigator designated time-points termed "critical" time-points. Using the bootstrap (re-sampling) technique, 1000 AUCs were computed by sampling (N = 2 rats/point, with replacement) from the 4 or 5 rats at each "critical" point. The data were subsequently modeled using PCNONLIN, and the parameters (ka, ke, and Vd) were perturbed by different degrees to simulate pharmacokinetic (PK) changes that may occur during a toxicology study due to enzyme induction/inhibition, etc. Finally Monte Carlo simulations were performed with random noise (10 to 40%) applied to Cp-t and/or PK parameters to examine its impact on AUCs from sparse sampling. RESULTS: The 5 time-points with 2 rats/point accurately and precisely estimated the AUC for F, L and DCL; the deviation from the full profile was approximately 10%, with a precision (%CV) of approximately 15%. Further, altered kinetics and random noise had minimal impact on AUCs from sparse sampling. CONCLUSIONS: Sparse sampling can accurately estimate AUCs and can be implemented in rodent toxicology studies to significantly reduce the number of animals for TK evaluations. The same principle is applicable to sparse sampling designs in other species used in safety assessments.

Pharmacokinetic-pharmacodynamic (PK-PD) modeling for a new antihypertensive agent (neutral metalloendopeptidase inhibitor SCH 42354) in patients with mild to moderate hypertension.

SCH 42354, a neutral metalloendopeptidase (NEP) inhibitor, is the pharmacologically active form of the prodrug SCH 42495. It exerts antihypertensive effects by potentiating atrial natriuretic peptide (ANP) activity through inhibition of its hydrolysis by NEP. The objective of this study was to characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of SCH 42354 in hypertensive males. SCH 42495 12.5 to 400 mg was administered orally to hypertensive men twice daily in a double-blind, placebo controlled multiple-dose parallel group design. Plasma SCH 42354 concentration and diastolic blood pressure (DBP) data were used to develop a PK-PD model using two approaches. In the first (non-integrated) approach, the ¿link¿ model was used to predict effect-site concentrations, and was applied to data obtained at the 300 and 400 mg BID doses only; data at the other (lower) doses were not amenable to modeling because of high variability. Effect-site concentration and DBP data were then fit to a sigmoid Emax PD model. For the 300 mg BID dose, PD parameters were: maximum effect (Emax), 8.1 mmHg; no-drug effect (Eo), 3.6 mmHg; concentration corresponding to 50% of maximum response (EC50), 0.87 microgram x ml(-1); and gamma, 3.9. In the second (time-integrated) approach, plasma SCH 42354 concentration and effect data obtained over the entire dose range were integrated with respect to time. Average plasma concentration and DBP data were then fit to a simple Emax PD model. PD parameters obtained over the dose range were: Emax, 10.3 mmHg; Eo, 2.0 mmHg; and EC50 0.7 microgram x ml(-1). These were similar to the estimates obtained from the first approach, demonstrating that the integrated (average) data allow PK-PD modeling over the (entire) dose range. The analysis showed that, at steady-state, a 400 mg BID dose of SCH 42495 produced an approximate 10 mmHg decrease in DBP in hypertensive males; the average plasma SCH 42354 concentration attained at this dose was approximately 1.8 microgram x ml(-1).