Fosciclopirox clinical proof of concept in patients with nonmuscle invasive and muscle-invasive bladder cancer

e16557

Background: Fosciclopirox (F) is being developed for the treatment of non-muscle invasive (NMIBC) and muscle invasive (MIBC) bladder cancer. F is a prodrug which is rapidly and completely metabolized in blood to its active metabolite, ciclopirox (CPX). In preclinical models of bladder cancer, CPX acts in part as a γ-secretase inhibitor by binding to γ-secretase complex proteins Presenilin 1 and Nicastrin, resulting in Notch and Wnt inhibition. The F Recommended Phase 2 Dose (RP2D), 900 mg/m2 administered IV over 20 minutes, was identified in the Phase 1 dose escalation trial (NCT03348514) in advanced solid tumor patients. Methods: The F RP2D was investigated in two early phase NMIBC and MIBC clinical proof of concept trials. In NCT04608045, neoadjuvant F was administered as monotherapy in cisplatin-ineligible (C-I) MIBC patients and in combination with gemcitabine + cisplatin in chemotherapy-eligible (C-E) MIBC patients. Clinical stage was assessed in pre-treatment (TURBT/CT) and post-treatment pathological state determined at radical cystectomy, (RC). The steady-state plasma and urine pharmacokinetics of F were also characterized. In NCT04525131, F was administered once daily for five days prior to TURBT. Pre- and post-treatment (at TURBT) bladder tumor samples underwent single cell sequencing to identify treatment effects on gene expression. Plasma, urine, and bladder tumor concentrations of F and its metabolites were determined in samples collected at TURBT. Results: Five C-E and 4 C-I MIBC patients received neoadjuvant F prior to RC. Twelve NMIBC patients received F prior to TURBT. There were no treatment-related serious adverse events observed in either study. Each patient experienced at least one treatment-emergent adverse event (TEAE), none of which resulted in study discontinuation. The most common TEAEs were nausea, fatigue, and constipation. Pathologic downstaging (< ypT2) of bladder tumors was observed in 3 C-E MIBC patients with 2 CRs (ypT0). Two of 4 C-I patients had evident clinical response by CT scan with only microscopic residual ypT2 disease. Treatment-related changes in expression of Notch 1, Notch 2, Hes 1, Hey-1, c-Myc, ß-catenin and survivin were observed in the majority of NMIBC patients. F disappeared from plasma within 2 hours of administration. The mean CPX elimination half-life of CPX, apparent systemic clearance, and volume of distribution values were 8.8 hours, 46 L/hr and 549 L, respectively. Mean plasma, tumor and urine concentrations of CPX at TURBT were approximately 27, 9 and 100 µM, respectively. Conclusions: To date, fosciclopirox is well tolerated and achieves sufficient systemic, tumor, and urine CPX exposure at the RP2D. Evidence of target inhibition was demonstrated in NMIBC tumors and preliminary signs of clinical activity observed in MIBC patients. Safety and efficacy trials are planned to confirm and expand findings in NMIBC and MIBC patients. Clinical trial information: NCT04608045; NCT04525131.

Phase Ib/IIa trial of CEND‐1 in combination with neoadjuvant FOLFIRINOX-based therapies in pancreatic, colorectal, and appendiceal cancers (CENDIFOX)

TPS4195

Background: The efficacy of chemotherapy is often compromised due to poor penetration of drugs in solid tumors. The tumor microenvironment, which is characterized by dense extracellular matrix‐rich stroma that creates a physical barrier to penetration of anti‐cancer drugs, is especially pronounced in Pancreatic Ductal Adenocarcinoma (PDAC) and in peritoneal metastases from Colorectal/Appendiceal Adenocarcinoma. CEND‐1 is a tumor‐penetrating peptide (scientifically also known as iRGD) that has preclinically demonstrated to enhance the tumor penetration of chemotherapy agents through binding and activation of alphav-integrins and neuropilin‐1 (NRP-1). The 2-step mechanism leads to a higher delivery and concentration of chemotherapeutics selectively in the tumor, while sparing normal tissue. Hence CEND-1 therapy has the potential to improve the efficacy of anti‐cancer therapies and reduce side effects through increased tumor access, specificity, and sensitivity. We hypothesize that CEND‐1 may become a powerful adjuvant that safely enhances standard anti‐neoplastic therapy in the neoadjuvant setting for the above populations. Methods: A safety lead-in 6-9 patients (Phase Ib) will be followed by an open label, single arm, parallel (3 cohorts) Phase IIa study. A total of 50 patients (20 PDAC, 15 colorectal/appendiceal with peritoneal metastases, 15 oligometastatic colorectal) will be enrolled. A starting CEND-1 dose of 3.2 mg/kg in combination with the standard doses of FOLFIRINOX (+/- Panitumumab if RAS/RAF wild type) will be used for the safety lead-in. CEND-1 dose will be lowered for Phase IIa if > 1/6 patients experienced DLTs. Participants enrolled will receive standard doses of FOLFIRINOX q2w +/- Panitumumab q2w 6mg/kg IV q2w (14-day cycles) for Cycles 1-3. After a subsequent research biopsy, the CEND-1 + chemotherapy combo will be continued at RP2D q2w for cycles 4-6, followed by CEND-1 +/- Panitumumab ̃72h prior to resection. Assessment of tumor response using RECIST v1.1 will be done every 3 cycles. Up to 10 patients may receive Panitumumab. Eligible Pts are untreated, newly diagnosed, resectable/borderline resectable PDAC or colorectal/appendiceal adenocarcinoma with peritoneal metastases or oligometastases eligible for cytoreductive surgery, as determined by multidisciplinary evaluation. Inclusion criteria also include ECOG PS 0-1, adequate organ function, measurable or evaluable disease. Primary objectives are safety and biological activity of CEND‐1. Secondary objectives include ORR, R0 resection rate, DFS, OS. Exploratory objectives include pathologic response, tissue immune response, EGFR expression, tumor tissue-to-plasma concentration of Panitumumab pre and post CEND-1 treatment. Enrollment to the CENDIFOX trial is currently ongoing. Clinical trial information: NCT05121038.

Phase 1B/2A safety, pharmacokinetics, and pharmacodynamics study of fosciclopirox alone and in combination with cytarabine in patients with relapsed/refractory acute myeloid leukemia

TPS7069

Background: Fosciclopirox (F) is a γ-secretase inhibitor being developed for the treatment of acute myeloid leukemia (AML). Following intravenous (IV) administration, F is rapidly and completely metabolized to its active metabolite, ciclopirox (CPX). CPX binds to γ-secretase complex proteins Presenilin 1 and Nicastrin, which are essential for Notch activation. In HL60 cells, CPX inhibits Notch 1 and Notch 2 expression, reduces levels of γ-secretase complex proteins Presenilin 1 and Nicastrin, and decreases expression of the downstream Notch target gene Hes-1. Utilizing Notable Labs predictive precision medicine platform, bone marrow (BM) and peripheral blood (PB) samples obtained from 10 AML patients treated with CPX demonstrated significant blast count reductions. Methods: Study CPX-POM-003 (NCT04956042) is an open-label Phase 1B/2A, trial designed to characterize the efficacy, safety, and PK/PD of F alone and in combination with cytarabine (ara-C) in patients with relapsed/refractory AML (R/R AML). Eligible patients must be 18 years of age or older with relapsed AML after complete remission or with primary refractory AML refractory to at least two cycles of induction therapy. There will be up to three cohorts of patients, approximately 42 R/R AML patients, evaluated. If disease response to F alone (Cohort 1a) is observed in at least 4 of 14 patients, an additional 14 patients will be enrolled in Cohort 1b. If disease response is not observed following F alone, the study may be terminated or a second cohort, Cohort 2a, may be initiated to evaluate the combination of F + ara-C. If disease response to F + ara-C is observed in at least 4 of 14 patients, an additional 14 patients will be enrolled in Cohort 2b. If response to F + ara-C is not observed in at least 4 of 14 patients, the study will be stopped for futility. F is being administered as 900 mg/m2 once daily as a 20-minute IV infusion on Days 1 to 5 of each 21-day treatment cycle. Ara-C is administered as 1 gm/m2 once daily on Days 1 to 5 of each cycle. BM and PB samples are collected prior to and during Cycles 1 (C1) and 2 (C2) for disease response assessment and blast count determination. Additional BM and PB samples are obtained after every two cycles beyond C2 for patients continuing treatment. Disease response is determined based on Döhner et al, Blood 2017;129(4)424-447. Next Generation Sequencing (NGS) profiles will be determined prior to and at the end of C1, and thereafter as clinically indicated. Immunohistochemistry will be performed on BM samples to elucidate drug mechanism. Ex vivo Drug Sensitivity Screening (DSS) will be performed on BM and PB samples obtained prior to treatment as well as on C1 Days 8 and 21. The steady-state plasma pharmacokinetics of F are being characterized during C1. Enrollment began in October 2022 with four patients enrolled to date. Clinical trial information: NCT04956042.

Abstract 6405: Fosciclopirox suppresses growth of high-grade urothelial cancer by targeting Notch signaling

Ciclopirox (CPX) is a FDA-approved topical antifungal agent that has demonstrated preclinical anticancer activity in solid and hematologic malignancies. It's clinical utility as an anticancer agent, however, is limited by poor oral bioavailability, gastrointestinal toxicity, and poor water solubility. Fosciclopirox, the phosphoryloxymethyl ester of CPX (Ciclopirox Prodrug, CPX-POM), is rapidly and completely metabolized to CPX, the active metabolite, which subsequently undergoes renal elimination resulting in urine concentrations of CPX that exceed in vitro IC50's several-fold. We characterized the activity of CPX-POM and its major metabolites in vitro utilizing authenticated human T24, HT-1376, and UM-UC-3 high-grade urothelial cancer cell lines. CPX inhibited cell proliferation, clonogenicity, and spheroid formation, and increased cell cycle arrest at S and G0/G1 phases. Mechanistically, CPX suppressed activation of Notch signaling, which was partially rescued by ectopic expression of the intracellular domain of Notch1. Molecular modeling and cellular thermal shift assays demonstrated CPX binding to γ-secretase complex proteins Presenilin1 and Nicastrin, which are essential for Notch activation. Interrogation of The Cancer Genome Atlas (TCGA) database demonstrated that both proteins were upregulated in bladder tumor tissue, and that higher levels of Presenilin1 and Nicastrin were significantly associated with lower overall survival in muscle invasive bladder cancer (MIBC) patients. To establish in vivo preclinical proof of principle, we tested fosciclopirox in the validated N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) mouse bladder cancer model in two separate studies. Intraperitoneal (IP) administration of CPX-POM once daily for four weeks at doses ranging from 25 to 200 mg/kg significantly decreased bladder weight and resulted in a migration to lower stage tumors in CPX-POM treated animals compared to untreated animals. This was coupled with a reduction in proliferation index, as well as reductions in Presenilin1 and Hey1 expression in bladder tumor tissues in CPX-POM treated animals. A similar anti-tumor response was observed following once daily versus three times weekly IP CPX-POM in this chemical carcinogen mouse model of bladder cancer. The safety, dose tolerance, pharmacokinetics and pharmacodynamics of intravenous (IV) CPX-POM were characterized in a US multi-center, First-in-Human, Phase 1, open-label, dose escalation study (NCT03348514). Eight cohorts of 19 patients received IV CPX-POM doses ranging from 30 to 1200 mg/m2 for as many as six 21-day treatment cycles. Adequate systemic and urinary tract CPX exposures were achieved at the maximum tolerated dose of 900 mg/m2 with evidence of Notch inhibition. An expansion cohort study in 12 cisplatin-ineligible MIBC patients receiving two treatment cycles of CPX-POM prior to radical cystectomy (RC) is underway. Evidence of pharmacologic activity is being characterized in bladder tumor tissues obtained at RC.

Citation Format: Scott James Weir, Prasad Dandawate, Prabhu Ramamoorthy, Parthasarathy Ranjarajan, Robyn Wood, Amanda Brinker, Benjamin Woolbright, Mehmet Tanol, Tammy Ham, William McCulloch, Michael Dalton, Michael J. Baltezor, Roy A. Jensen, John A. Taylor, Shrikant Anant. Fosciclopirox suppresses growth of high-grade urothelial cancer by targeting Notch signaling [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6405.

Window of opportunity trial to characterize the safety, pharmacokinetics, and pharmacodynamics of fosciclopirox (CPX-POM) in cisplatin-ineligible muscle invasive bladder cancer patients

TPS604

Background: Fosciclopirox (Ciclopirox Prodrug, CPX-POM) is being developed for the treatment of non-muscle invasive and muscle invasive (MIBC) bladder cancer. CPX-POM selectively delivers its active metabolite, ciclopirox (CPX), to the entire urinary tract following systemic administration. In a validated, chemical carcinogen mouse model of bladder cancer, CPX-POM treatment results in significant decreases in bladder weight, a clear migration to lower stage tumors, dose-dependent reductions in Ki67 and PCNA staining, and inhibition of Notch 1 and Wnt signaling. The safety, dose tolerance, pharmacokinetics and pharmacodynamics of IV CPX-POM have recently been characterized in 19 patients with advanced solid tumors (CPX-POM-001, NCT03348514). The safety and dose tolerance of IV CPX-POM was characterized across a dose range of 30 to 1200 mg/m2. The CPX-POM Recommended Phase 2 Dose (PR2D) of 900 mg/m2 administered IV over 20 minutes on Days 1-5 every 21 days was selected. Methods: Twelve cisplatin ineligible MIBC patients (Stage >T2, NO-N1, M0), scheduled for radical cystectomy (RC) will be enrolled in this window of opportunity study. Patients will receive two 21-day treatment cycles followed by RC within 14 days of completion of the second cycle. Safety and tolerability assessments will be made based on observed adverse and serious adverse events, physical examination, vital signs, electrocardiogram, clinical laboratory tests, and concomitant medications. Assessment of complete and partial pathologic response will be determined at RC. Ki67, Notch and Wnt signaling, and CD8+ lymphocyte tumor infiltration will be determined by immunohistochemistry. An unbiased approach to characterizing CPX-POM mechanisms of action will also be employed using RNAseq and ChIPseq. Serial blood (plasma) and complete urine specimens will be collected on Days 5-6 of Cycle 1 for determination of drug and metabolite concentrations by LC-MS/MS. Plasma and urine steady-state pharmacokinetics of CPX-POM, CPX and ciclopirox glucuronide will be characterized. Urine ß-glucuronidase activity is also being determined by ELISA. Clinical trial information: NCT03348514.

Safety, dose tolerance, pharmacokinetics, and pharmacodynamics of fosciclopirox (CPX-POM) in patients with advanced solid tumors

518

Background: Fosciclopirox (CPX-POM) is being developed for the treatment of non-muscle invasive and muscle invasive bladder cancer. CPX-POM selectively delivers its active metabolite, ciclopirox (CPX), to the entire urinary tract following systemic administration. In a chemical carcinogen mouse model of bladder cancer, CPX-POM treatment resulted in significant decreases in bladder weight, migration to lower stage tumors, inhibition of cell proliferation as well as Notch 1 and Wnt signaling pathways. Methods: Study CPX-POM-001 (NCT03348514) is US multi-site, Phase I, open-label, dose escalation study characterizing the safety, dose tolerance, pharmacokinetics (PK) and pharmacodynamics of IV CPX-POM in advanced solid tumor patients. The PK of CPX-POM, CPX and ciclopirox glucuronide (CPX-G), were characterized in plasma and urine. Circulating biomarkers of Wnt and Notch, IL-6, IL-8 and VEGF were determined. Results: Nineteen patients were enrolled in the study. The starting dose of 30 mg/m2 was administered once daily on Days 1-5 of each 21-day treatment cycle. Doses were escalated to 1200 mg/m2. The MTD was determined to be 900 mg/m2. Overall, the number of treatment-related AE's tended to increase in frequency with dose, nausea and vomiting being the most common. Grade 3 confusion was observed in the 1200 mg/m2 cohort. Four AE's of Grade 1 confusion at 600 and 900 mg/m2. There was no evidence of QTc prolongation or other ECG abnormality. One patient in the 240 mg/m2 dose cohort, with a diagnosis of indolent primary fallopian tube tumor, achieved a partial response per RECIST 1.1. Metabolism of CPX-POM was rapid and complete. The clearance of CPX was dose proportional and time-independent. At MTD, steady-state 24-hour urine CPX concentrations of 215 µM were achieved. Evidence of Notch and Wnt inhibition was observed. Conclusions: IV CPX-POM was well tolerated with treatment-related AEs primarily CNS-related. At MTD, systemic and urinary CPX exposures exceeding in vitro IC50 values by several-fold. The 900 mg/m2 dose is currently being evaluated in an expansion cohort study in cisplatin-ineligible muscle invasive bladder cancer patients scheduled for cystectomy. Clinical trial information: NCT03348514.

Pharmacokinetics of ciclopirox prodrug, a novel agent for the treatment of bladder cancer, in animals and humans

e14705

Background: Ciclopirox Prodrug (CPX-POM) is a novel anticancer agent currently being evaluated in patients with advanced solid tumors participating in a First-in-Human, Phase 1 safety, dose tolerance, pharmacokinetics (PK) and pharmacodynamics trial at four US sites. In vitro and in vivo preclinical proof of principle was established in high grade human urothelial cancer cell lines as well as a mouse model of bladder cancer.Methods: A series of in vivo PK studies were conducted in mice, rats and dogs to characterize the absolute bioavailability of CPX following intravenous (IV), subcutaneous (SC) and oral administration of CPX-POM. The single dose and steady-state plasma and urine pharmacokinetics of CPX-POM are also currently being characterized in patients participating in the ongoing Phase 1 trial. Plasma and urine concentrations of the prodrug and metabolites were determined by LC-MS/MS validated in each specie and matrix. Non-parametric pharmacokinetic parameters were generated from resultant plasma and urine drug and metabolite concentration-time data. Results: CPX-POM is rapidly and completely metabolized to CPX in blood via circulating phosphatases in animals and humans. CPX is completely bioavailable following IV CPX-POM administration in mice, rats and dogs. CPX and its major inactive glucuronide metabolite (CPX-G) are extensively eliminated in urine in all animal species. SC administration of CPX-POM demonstrated excellent bioavailability in rats and dogs. Following IV administration of 30-900 mg/m2CPX-POM to patients, the apparent elimination half-life of CPX ranged from 2 to 8 hours, CPX systemic exposure was dose-proportional and time-independent in cancer patients, and a major portion of the dose was eliminated as CPX-G. Conclusions: IV CPX-POM achieves plasma and urine CPX exposures that exceed in vitro IC50 values several-fold at well tolerated doses in animals and humans. CPX pharmacokinetics observed in animals were predictive of human systemic clearance based on allometric scaling. Clinical trial information: NCT03348514.

Repurposing ethacrynic acid for the treatment of bladder cancer

521

Background: Bladder cancer is a common cancer in the US. Approximately seventy-five percent of new cases present as non-muscle invasive bladder cancer (NMIBC) with a high recurrence rate. Our group has demonstrated in well-characterized human NMIBC cell lines that ethacrynic acid (EA) suppresses growth by inhibiting proliferation, clonogenicity, spheroid formation and inducing apoptosis. Additionally, EA affects markers of stemness and may work through the NOTCH signaling pathway. We present a clinical trial characterizing the safety and urinary tract exposure to EA and metabolites following oral administration in patients undergoing transurethral resection of bladder tumor (TURBT). Methods: Institutional review board approval (#3674) was obtained for a Pilot trial in patients with presumed non-muscle invasive bladder cancer undergoing TURBT. All participants were given a single, 50 mg oral dose of EA in the pre-operative bay. Urine was collected at baseline, upon insertion of cystoscope (30-60 minutes post dose), and post-operatively. Urine concentrations of EA and metabolites were determined using a fully-validated UPLC-MS/MS-based analytical method. Participants were monitored for adverse events. Results: Twelve participants participated in the trial between August 2016 and February 2017. Eleven male and one female patient (median age 70.5 years) were enrolled. Final pathology demonstrated urothelial carcinoma in 5/12 (42%) subjects, three with high grade T1 and two with low-grade Ta tumors. Urine concentrations of EA and conjugates observed 30-60 minutes post-dose were as follows: EA 0.1 ug/mL, EA-glutathione 0.2 ug/mL, EA-cysteine 3 ug/mL, and EA-mercapturate 2 ug/mL. No drug-related adverse events were observed following oral EA administration. Conclusions: Despite EA receiving FDA approval over 40 years ago, our pilot trial describes for the first time, urinary tract exposure of EA and its active metabolites in bladder cancer patients after a single oral dose. These data are guiding ongoing preclinical proof of principle studies evaluating EA alone and in combination with standard of care agents in bladder cancer models. These studies warrant further studies of EA in patients with non-muscle invasive bladder cancer. Clinical trial information: NCT02852564.

A mortality event in wrasse species (Labridae) associated with the presence of viral haemorrhagic septicaemia virus

Viral haemorrhagic septicaemia (VHS) is an infectious disease of farmed and wild fish and has an extensive host range in both freshwater and marine environments. In December 2012, a wrasse population consisting of ballan, Labrus bergylta (Ascanius), corkwing, Symphodus melops (L.), cuckoo, Labrus mixtus L., goldsinny, Ctenolabrus rupestris (L.), and rock cook, Centrolabrus exoletus (L.), held at a marine hatchery in the Shetland Isles, Scotland, experienced a mortality event. Approximately 10 000 wrasse were being held at the facility on behalf of an Atlantic salmon, Salmo salar L., aquaculture company prior to being deployed for the biological control of parasites on marine pen Atlantic salmon, aquaculture sites. Fish Health Inspectors from Marine Scotland Science initiated a diagnostic investigation, and subsequent diagnostic testing confirmed the site to be VHSV positive by qRT-PCR and virus isolation followed by ELISA. A VHSV genotype-specific qRT-PCR assay revealed that the isolates belonged to genotype III, the European marine strain of the virus. The virus genotype was further confirmed by nucleic acid sequencing of the partial nucleoprotein (N) and glycoprotein (G) genes followed by BLAST nucleotide searches. This study reports for the first time the detection of VHSV within multiple wrasse species and highlights the need for a comprehensive risk-based approach to the use of wrasse and other finfish species as biological controls within the aquaculture industry.

The repositioning of the anti-fungal agent ciclopirox olamine as a novel therapeutic agent for the treatment of haematologic malignancy

WHAT IS KNOWN AND OBJECTIVE

6-Cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone (ciclopirox) and specifically its olamine salt 6-cyclohexyl-1-hydroxy-4-methyl-2(1H)-pyridone 2-aminoethanol salt (ciclopirox olamine) are anti-fungal agents currently used for the treatment of mild to moderate cutaneous fungal infection. Our objective is to comment on the opportunity to rapidly reposition ciclopirox and its olamine for the treatment of haematologic malignancy by leveraging its prior published toxicology and pharmacology data.

COMMENT

Ciclopirox olamine chelates intracellular iron and displays preclinical efficacy in the treatment of haematologic malignancy. Currently, an ongoing study is evaluating topical ciclopirox olamine for the treatment of cervical cancer. Doses of ciclopirox olaine required for a systemic anti-cancer effect appear pharmacologically achievable. However, caution is required as at the highest doses tested in animal toxicology studies, irreversible cardiac degeneration was observed.

WHAT IS NEW AND CONCLUSION

The existing pharmacology and toxicology data suggest that systemic ciclopirox olamine could be repositioned as a new investigational anti-cancer agent. The available pharmacology and toxicology data should aid in the design of phase I clinical trials of this agent in patients with refractory haematologic malignancies.

Steady-state pharmacokinetics of high-dose diltiazem hydrochloride (Cardizem CD) administered once daily in healthy volunteers

The once-daily formulation of diltiazem hydrochloride (Cardizem CD) is marketed for the treatment of essential hypertension and stable angina pectoris. The steady-state pharmacokinetics of once-daily diltiazem and its metabolites, desacetyldiltiazem (DAD) and N-desmethyldiltiazem (MA), were examined in two groups of eight healthy subjects each. The first group (group A) received 240, 480, and 720 mg diltiazem once daily for 7 days in a single-blind, stair-step, dose-escalation design. The second group (group B) received 180, 360, and 720 mg diltiazem in a similar manner. At each dose level, serial blood samples were collected for up to 24 hours after the last (seventh) dose. Plasma samples were analyzed for diltiazem and the metabolites by high-performance liquid chromatography. The disposition of diltiazem, DAD, and MA was nonlinear over the 240- to 720-mg (group A) and 180- to 720-mg (group B) diltiazem dose ranges studied. In group A, mean diltiazem area under the plasma concentration-time curve (AUC) at the 240-mg dose level was 2410 h.ng/mL compared with 10,167 h.ng/mL at the 720-mg dose level. In group B, mean diltiazem AUC at the 180-mg dose level was 1092 h.ng/mL compared with 8398 h.ng/mL at the 720-mg dose level. The apparent oral clearance decreased 35% over a threefold dose range (group A) and 51% over a fourfold dose range (group B). Mean ratios of AUCDAD/AUC(DILT) were similar at all dose levels. Mean AUCMA/AUC(DILT) ratios, however, decreased with increasing diltiazem dose, suggesting that the nonlinear disposition of MA may be less pronounced than that of parent drug.

Single and multiple dose pharmacokinetics of rifapentine in man: part II

OBJECTIVE

To characterize the pharmacokinetics of rifapentine following single, multiple, and intermittent doses.

DESIGN

Twenty-three healthy male volunteers were randomized in a two-period, incomplete block, crossover design to receive two of four possible treatments: single daily oral rifapentine doses of 150, 300, or 600 mg given on day 1 and again on days 4-10, or a single oral 600 mg dose given on days 1, 4, 7, and 10.

RESULTS

Maximum rifapentine plasma concentrations were observed in 4-5 hours. Mean rifapentine t(1/2) ranged from 13.2-14.1 hours and was similar across the 150-600 mg dose range. The changes in rifapentine Cmax (R = 0.86) and AUC(0-->infinity) (R + 0.90) were dose linear. The active 25-desacetyl metabolite appeared slowly in plasma, with mean Tmax of 14.4-17.8 hours. Mean t(1/2) for 25-desacetyl-rifapentine ranged from 13.3-24.3 hours. Disproportionate, dose-dependent increases in rifapentine and 25-desacetyl-rifapentine AUC were observed as single doses of rifapentine increased from 150 to 600 mg. At steady state, however, the magnitude of dose dependency was much less.

CONCLUSION

Maximum plasma rifapentine concentrations were well above minimum inhibitory concentrations for Mycobacterium tuberculosis and M. avium following single 600 mg doses. In addition, the extended t(1/2) of rifapentine and its active metabolite support clinical investigation of once or twice-weekly rifapentine dosage regimens of rifapentine for the management of tuberculosis.

Enzyme induction observed in healthy volunteers after repeated administration of rifapentine and its lack of effect on steady-state rifapentine pharmacokinetics: part I

OBJECTIVE

To determine the effects of rifapentine on hepatic mixed function oxidase activity and to assess the effect of enzyme induction on the steady-state pharmacokinetics of rifapentine.

STUDY DESIGN

Twenty-three healthy males were randomized to receive two of the following treatments in a two-period, four-treatment, incomplete block, crossover design: single daily oral rifapentine doses of 150 mg (group A), 300 mg (group B), or 600 mg (group C) on study days 1 and 4-10, or single oral rifapentine 600 mg doses given every 3 days for a total of four doses (group D). Serial blood samples were collected after the first and last rifapentine dose and assayed for rifapentine and its active metabolite, 25-desacetyl-rifapentine. Urine was collected for determination of cortisol and 6-hydroxycortisol concentrations.

RESULTS

The ratio of 6beta-hydroxycortisol:cortisol increased during rifapentine administration (+229%, +317%, and +357% on day 10 for groups A, B, and C, respectively). Ratios returned to baseline 2 weeks after the last dose. The per cent increase in the ratio of 6beta-hydroxycortisol:cortisol following daily doses (+357%) was much higher compared with every 72-hour dosing (+236%). Single-dose and steady-state comparisons of AUCss(0-24) and AUC(0-->infinity) for both rifapentine and 25-desacetyl-rifapentine were similar (P = NS) at corresponding doses of rifapentine. Mean t(1/2) at steady-state was 84-98% of corresponding single-dose values.

CONCLUSION

Rifapentine is a potent inducer of CYP3A activity. However, single-dose pharmacokinetics of rifapentine predict steady-state exposure, indicating no autoinduction of rifapentine metabolism with repeated administration. Enzyme activity returns to predose levels within 2 weeks of the last daily dose of rifapentine.

Pharmacokinetics of rifapentine in subjects seropositive for the human immunodeficiency virus: a phase I study

Rifapentine is undergoing development for the treatment of pulmonary tuberculosis. This study was conducted to characterize the single-dose pharmacokinetics of rifapentine and its 25-desacetyl metabolite and to assess the effect of food on the rate and extent of absorption in participants infected with human immunodeficiency virus (HIV). Twelve men and four women, mean age, 38.6 +/- 6.9 years, received a single 600-mg oral dose of rifapentine in an open-label, randomized two-way, complete crossover study. Each volunteer received rifapentine following a high-fat breakfast or during a fasting period. Serial blood samples were collected for 72 h and both rifapentine and its metabolite were assayed by a validated high-performance liquid chromatography method. Pharmacokinetics of rifapentine and 25-desacetylrifapentine were determined by noncompartmental methods. Mean (+/- the standard deviation) maximum concentrations of rifapentine in serum and areas under the curve from time zero to infinity following a high-fat breakfast were 14.09 +/- 2.81 and 373.63 +/- 78.19 micrograms/ml, respectively, and following a fasting period they were 9.42 +/- 2.67 and 256.10 +/- 86.39 micrograms. h/ml, respectively. Pharmacokinetic data from a previously published healthy volunteer study were used for comparison. Administration of rifapentine with a high-fat breakfast resulted in a 51% increase in rifapentine bioavailability, an effect also observed in healthy volunteers. Although food increased the exposure of these patients to rifapentine, the infrequent dosing schedule for the treatment of tuberculosis (e.g., once- or twice-weekly dosing) would be unlikely to lead to accumulation. Additionally, autoinduction has been previously studied and has not been demonstrated with this compound, unlike with rifabutin and rifampin. Rifapentine was well tolerated by HIV-infected study participants. The results of our study suggest that no dosage adjustments may be required for rifapentine in HIV-infected patients (Centers for Disease Control and Prevention classification A1, A2, B1, or B2) undergoing treatment for tuberculosis.

Pharmacokinetics of dolasetron with coadministration of cimetidine or rifampin in healthy subjects

PURPOSE

Dolasetron is a selective 5-HT3 receptor antagonist. The purpose of this study was to determine the effect of cimetidine and rifampin on the steady-state pharmacokinetics of orally administered dolasetron and its active reduced metabolite, hydrodolasetron.

METHODS

A group of 18 healthy men (22 to 44 years old) were randomized to receive each of the following three treatments in a three-period cross-over design: 200 mg dolasetron daily (treatment A); 200 mg dolasetron daily plus 300 mg cimetidine four times daily (treatment B); or 200 mg dolasetron daily plus 600 mg rifampin daily (treatment C). Each study period was separated by a 14-day washout period. Serial blood samples were collected before the first dose (baseline) on day 1 and at frequent intervals up to 48 h after the morning dose on day 7 for quantification of dolasetron and its metabolites, hydrodolasetron (both isomers), 5'OH hydrodolasetron, and 6'OH hydrodolasetron. Serial urine samples were also collected at baseline and during the periods 0-24 and 24-48 h following the morning dose on day 7, and analyzed for dolasetron and its metabolites.

RESULTS

Plasma and urine dolasetron concentrations were below quantifiable concentrations for all three treatments. Mean steady-state area under the plasma concentration-time curve (AUCss(0-24)) of hydrodolasetron increased by 24%, mean apparent clearance (CLapp.po) decreased by 19%, and maximum plasma hydrodolasetron concentration (Cmax,ss) increased by 15% when dolasetron was coadministered with cimetidine. When dolasetron was given with rifampin, mean hydrodolasetron AUCss(0-24) decreased by 28%, CLapp.po, increased by 39%, and hydrodolasetron Cmax,ss decreased by 17%. Small differences were found in mean tmax (0.7 to 0.8 h), CLr (2.0 to 2.6 ml/min per kg), and t1/2 (7.4 to 8.8 h) for hydrodolasetron between treatment periods. Approximately 20% and 2% of the dolasetron dose were excreted in urine as the R(+) isomer and S(-) isomer of hydrodolasetron, respectively, across all three treatments. Dolasetron mesylate was well tolerated in this study during all three treatment periods, with the highest incidence of adverse events reported during the control period when dolasetron mesylate was given alone.

CONCLUSION

Based on the small changes in the pharmacokinetic parameters of dolasetron and its active metabolites, as well as the favorable safety results, no dosage adjustments for dolasetron mesylate are recommended with concomitant administration of cimetidine or rifampin.

Intravenous pharmacokinetics and absolute oral bioavailability of dolasetron in healthy volunteers: part 1

In this first part of a two-part investigation, the intravenous dose proportionality of dolasetron mesylate, a 5-HT3 receptor antagonist, and the absolute bioavailability of oral dolasetron mesylate were investigated. In an open-label, randomized, four-way crossover design, 24 healthy men between the ages of 19 and 45 years received the following doses: 50, 100, or 200 mg dolasetron mesylate administered by 10-min intravenous infusion or 200 mg dolasetron mesylate solution administered orally. Serial blood and urine samples were collected for 48 h after dosing. Following intravenous administration, dolasetron was rapidly eliminated from plasma, with a mean elimination half-life (t1/2) of less than 10 min. Dolasetron was rarely detected in plasma after oral administration of the 200 mg dose. Hydrodolasetron, the active primary metabolite of dolasetron, appeared rapidly in plasma following both oral and intravenous administration of dolasetron mesylate, with a mean time to maximum concentration (t(max)) of less than 1 h. The mean t1/2 of hydrodolasetron ranged from 6.6-8.8 h. The plasma area under the concentration-time curve (AUC0-infinity)) for both dolasetron and hydrodolasetron increased proportionally with dose over the intravenous dose range of 50-200 mg dolasetron mesylate. Approximately 29-33%) and 22% of the dose was excreted in urine as hydrodolasetron following intravenous and oral administration of dolasetron, respectively. For dolasetron as well as hydrodolasetron, mean systemic clearance (C1), volume of distribution (Vd), and t1/2 were similar at each dolasetron dose. The mean 'apparent' bioavailability of dolasetron calculated using plasma concentrations of hydrodolasetron was 76%. The R(+) enantiomer of hydrodolasetron represented the majority of drug in plasma (> 75%) and urine (> 86%). Dolasetron was well tolerated following both oral and intravenous administration.

Single- and multiple-dose pharmacokinetics of oral dolasetron and its active metabolites in healthy volunteers: part 2

The single- and multiple-dose pharmacokinetics and dose-proportionality of oral dolasetron and its active metabolites over the therapeutic dose range was investigated in 18 healthy men. In an open-label, randomized, complete three-way crossover design, each subject received three separate doses: 50, 100, and 200 mg doses of dolasetron mesylate solution given orally. Each dose was administered on the morning of Days 1 and 3-7 during each of the three treatment periods. Serial blood and urine samples were collected for 48 h after the first and last doses. Blood was analysed for dolasetron and hydrodolasetron concentrations; urine was analysed for dolasetron, the R(+) and S(-)-enantiomers of hydrodolasetron, and the 5'-hydroxy and 6'-hydroxy metabolites of hydrodolasetron. Dolasetron was rarely detected in plasma. Hydrodolasetron was formed rapidly, with a time to maximum concentration (t(max)) of less than 1 h. Steady-state conditions for hydrodolasetron were reached 2-3 days after starting once-daily dosing. Although statistical significance was found for hydrodolasetron AUC(0->infinity) and C(max) between dose groups after both single and multiple doses of dolasetron, the differences were small and unlikely to be of clinical significance. About 17-22% of the dose was excreted in urine as hydrodolasetron, with the majority (> 83%) as the R(+) enantiomer.

Dose proportionality and comparison of single and multiple dose pharmacokinetics of fexofenadine (MDL 16455) and its enantiomers in healthy male volunteers

The pharmacokinetics and dose proportionality of fexofenadine, a new non-sedating antihistamine, and its enantiomers were characterized after single and multiple-dose administration of its hydrochloride salt. A total of 24 healthy male volunteers (31 +/- 8 years) received oral doses of 20, 60, 120 and 240 mg fexofenadine HCl in a randomized, complete four-period cross-over design. Subjects received a single oral dose on day 1, and multiple oral doses every 12 h on day 3 through the morning on day 7. Treatments were separated by a 14-day washout period. Serial blood and urine samples were collected for up to 48 h following the first and last doses of fexofenadine HCl. Fexofenadine and its R(+) and S(-) enantiomers were analysed in plasma and urine by validated HPLC methods. Fexofenadine pharmacokinetics were linear across the 20-120 mg dose range, but a small disproportionate increase in area under the plasma concentration-time curve (AUC) (< 25%) was observed following the 240 mg dose. Single-dose pharmacokinetics of fexofenadine were predictive of steady-state pharmacokinetics. Urinary elimination of fexofenadine played a minor role (10%) in the disposition of this drug. A 63:37 steady-state ratio of R(+) and S(-) fexofenadine was observed in plasma. This ratio was essentially constant across time and dose. R(+) and S(-) fexofenadine were eliminated into urine in equal rates and quantities. All doses of fexofenadine HCl were well tolerated after single and multiple-dose administration.

Steady-state pharmacokinetics of diltiazem and hydrochlorothiazide administered alone and in combination

Diltiazem and hydrochlorothiazide are widely used to treat cardiovascular disease, often in combination. The purpose of this investigation was to determine whether a drug-drug pharmacokinetic interaction exists between diltiazem and hydrochlorothiazide. In a randomized, crossover, open study, multiple doses of diltiazem (60 mg four times daily for 21 doses) and hydrochlorothiazide (25 mg twice daily for 11 doses) were administered alone and in combination on three separate occasions to 20 healthy male volunteers. Trough and serial blood samples were collected and plasma was assayed for diltiazem, hydrochlorothiazide, and diltiazem metabolites (desacetyldiltiazem and N-desmethyldiltiazem) using HPLC. Total urine was also collected and quantified for hydrochlorothiazide. Coadministered hydrochlorothiazide did not significantly (p > 0.05) alter diltiazem (alone versus combination) steady-state maximum plasma concentration (Css(max); 145 versus 158 ng mL(-1), respectively), time to maximum plasma concentration (t(max); 3.0 versus 2.8 h, respectively); area under the plasma concentration-time curve (AUCss; 688 versus 771 ng x h mL(-1)), oral clearance (Cl(oral); 96.2 versus 88.0 L h(-1)), or elimination half-life (t(1/2); 5.2 versus 5.2 h). Similarly, administration of diltiazem did not significantly (p > 0.05) influence hydrochlorothiazide (alone versus combination) Css(max) (221 versus 288 ng mL(-1)), t(max) (1.8 versus 2.0 h), AUCss (1194 versus 1247 ng x h mL(-1)), Cl(oral) (22.4 versus 21.2 L h(-1)); t(1/2) (9.8 versus 9.6 h), or renal Cl (15.5 versus 15.2 L h(-1)). In conclusion, a clinically significant pharmacokinetic interaction between diltiazem and hydrochlorothiazide does not exist.

Pharmacokinetics of oral and intravenous dolasetron mesylate in patients with renal impairment

In an open-label, randomized, two-way complete crossover study, the influence of renal impairment on the pharmacokinetics of dolasetron and its primary active metabolite, hydrodolasetron, were evaluated. Patients with renal impairment were stratified into three groups of 12 based on their 24-hour creatinine clearance (Cl(cr)): group 1, mild impairment (Cl(cr) between 41 and 80 mL/min); group 2, moderate impairment (Cl(cr) between 11 and 40 mL/min); and group 3, endstage renal impairment (Cl(cr) < or = 10 mL/min). Twenty-four healthy volunteers from a previous study served as the control group. Each participant received a single intravenous or oral 200-mg dose of dolasetron mesylate on separate occasions. Serial blood samples were collected up to 60 hours after dose for determination of dolasetron and hydrodolasetron, and urine samples were collected in intervals up to 72 hours for determination of dolasetron, hydrodolasetron, and the 5' and 6'-hydroxy metabolites of hydrodolasetron. Because plasma concentrations were low and sporadic, pharmacokinetic parameters of dolasetron were not calculated after oral administration. Although some significant differences in area under the concentration-time curve (AUC0-infinity), volume of distribution (Vd), systemic clearance (Cl), and elimination half-life (t1/2) of the parent drug were observed between control subjects and patients with renal impairment, there were no systematic findings related to degree of renal dysfunction. The elimination pathways of hydrodolasetron include both hepatic metabolism and renal excretion. Consistent increases in mean Cmax, AUC0-infinity, and t1/2 and decreases in renal and total apparent clearance of hydrodolasetron were seen with diminishing renal function after intravenous administration of dolasetron mesylate. No consistent changes were found after oral administration. Urinary excretion of hydrodolasetron and its metabolites decreased with decreasing renal function, but the profile of metabolites remained constant. Dolasetron was well tolerated in all three groups of patients. Based on these findings, no dosage adjustment for dolasetron is recommended in patients with renal impairment.

Single-dose pharmacokinetics of rifapentine in elderly men

PURPOSE

This study was undertaken to characterize the pharmacokinetic profiles of rifapentine and its active metabolite, 25-desacetlyl rifapentine, in elderly men.

METHODS

Fourteen healthy, nonsmoking male volunteers between the ages of 65 and 82 years received a single oral 600 mg dose of rifapentine. Plasma samples were collected at frequent intervals for up to 72 hours postdose. The control group consisted of 20 healthy, young (18-45 years) males volunteers from a previous, single-dose (600 mg) rifapentine pharmacokinetic study.

RESULTS

Plasma rifapentine concentrations above the minimum inhibitory concentration for M. tuberculosis were observed at 2 hours after dosing. Disposition of rifapentine was monophasic with a mean terminal half-life of 19.6 hours. The peak plasma concentration of 25 desacetyl-rifapentine was found 21.7 hours, on average, after the rifapentine dose; the mean 25-desacetyl-rifapentine t1/2 was 22.9 hours. Compared to the younger subjects, apparent oral clearance of rifapentine (24%) was lower in the elderly male (p < 0.05), and Cmax (28%) was higher. The only adverse event reported in both the older and younger subjects in these single-dose studies was discoloration of the urine.

CONCLUSIONS

Because the aged-related changes in the pharmacokinetic profile of rifapentine observed in this study were modest and unlikely to be associated with toxicity, no dosage adjustments for this antibiotic are recommended in elderly patients.

Disposition and metabolism of 14C-rifapentine in healthy volunteers

Rifapentine is a long-acting cyclopentyl-derivative of rifampin. This study was designed to investigate the mass balance and biotransformation of 14C-rifapentine in humans. Four healthy male volunteers received a single 600-mg oral dose of 14C-rifapentine in a hydroalcoholic solution. Whole blood, urine, and fecal samples were collected before and at frequent intervals after drug administration. Amount of radioactivity recovered in urine and feces was assessed for up to 18 days postdose. Metabolite characterization in urine and feces was conducted using high-performance liquid chromatography with radiometric detection and liquid chromatography/mass spectroscopy. The total recovery of radioactive dose was 86.8%, with the majority of the radioactive dose recovered in feces (70.2%). Urine was a minor pathway for excretion (16.6% of the dose recovered). More than 90% of the excreted radioactivity was profiled as 14C chromatographic peaks and 50% was structurally characterized. These characterized compounds found in feces and urine were rifapentine, 25-desacetyl-rifapentine, 3-formyl-rifapentine, and 3-formyl-25-desacetyl-rifapentine. The 25-desacetyl metabolite, formed by esterase enzymes found in blood, liver, and other tissues, was the most abundant compound in feces and urine, contributing 22% to the profiled radioactivity in feces and 54% in urine. The 3-formyl derivatives of rifapentine and 25-desacetyl-rifapentine, formed by nonenzymatic hydrolysis, were also prominent in feces and, to a lesser extent, in urine. In contrast to the feces and urine, rifapentine and 25-desacetyl-rifapentine accounted for essentially all of the plasma radioactivity (99% of the 14C area under the concentration-time curve), indicating that 25-desacetyl-rifapentine is the primary metabolite in plasma. It appears, therefore, that the nonenzymatic hydrolysis of rifapentine to 3-formyl byproducts occurs primarily in the gut and the acidic environment of the urine.

Pharmacokinetics of rifapentine in patients with varying degrees of hepatic dysfunction

In this open-label investigation, the pharmacokinetics of rifapentine and its active metabolite, 25-desacetyl-rifapentine, were characterized in patients with varying degrees of hepatic dysfunction. Eight patients with mild-to-moderate chronic, stable hepatic dysfunction and seven patients with moderate-to-severe hepatic dysfunction received single oral 600-mg doses of rifapentine. Maximum plasma concentration of rifapentine was lower, time to maximum plasma concentration (tmax) was greater, and elimination half-life (t 1/2) was longer in the patients with moderate-to-severe hepatic dysfunction than in those with mild-to-moderate dysfunction. However, mean area under the concentration-time curve extrapolated to infinity (AUC0-infinity) for the two groups was similar. AUC0-infinity values in patients with hepatic dysfunction were 19% to 25% higher than values previously reported for healthy volunteers. The 25-desacetyl metabolite appeared in plasma slowly after the single oral dose of rifapentine. Similar to findings for the parent drug, comparable plasma exposures of 25-desacetyl-rifapentine based on AUC0-infinity were found in the two groups of patients with mild-to-moderate and moderate-to-severe hepatic dysfunction. Rifapentine was well tolerated in this patient population, irrespective of the etiology or severity of hepatic dysfunction. These safety and pharmacokinetic results suggest that no dosage adjustments for rifapentine are needed in patients with hepatic impairment.

Relative bioavailability of Cardizem CD and Tiazac controlled-release diltiazem dosage forms after single and multiple dosing in healthy volunteers

The purpose of this study was to determine the relative bioavailability of Cardizem CD compared to Tiazac after single and multiple doses. Twenty-three healthy males were enrolled in this open-label, two-way, complete crossover investigation. During each of the two treatment periods, a single 240-mg dose of diltiazem HCl was given in the morning on study day 1, then once daily on days 3 through 9. Serial plasma samples were obtained and pharmacokinetic parameters were calculated from the single-dose and steady-state concentration-time profiles. After single doses, mean diltiazem maximum plasma concentration (Cmax ) was 46% higher with the Tiazac formulation compared with Cardizem CD, and the mean area under the plasma concentration-time profile (AUC) was 19% higher with Tiazac. At steady-state, similar Cmax and AUC for the 24-hour dosing interval were found for Cardizem CD and Tiazac. However, Tiazac produced a 21% lower diltiazem minimum plasma concentration, a 28% lower trough concentration (the concentration in the plasma sample obtained just before the daily dose was given), and a 1.5-times higher fluctuation in maximum to minimum diltiazem plasma concentration compared with Cardizem CD. The pharmacokinetic profiles of the two pharmacologically active diltiazem metabolites, desacetyldiltiazem and N-desmethyldiltiazem, followed that of parent drug after single and multiple doses of Cardizem CD and Tiazac. From these results, it is concluded that the pharmacokinetic profiles of Tiazac and Cardizem CD are significantly different.

Single-dose pharmacokinetics of rifapentine in women

Gender can be an important variable in the absorption and disposition of some drugs. In this open-label study, 15 healthy, nonsmoking women received a single 600-mg oral dose of rifapentine. Plasma samples were obtained at frequent intervals for up to 72 hr after the dose to determine the pharmacokinetic (PK) parameters of rifapentine and its active metabolite, 25-desacetyl-rifapentine. Peak plasma rifapentine concentrations (Cmax) were observed 5.9 hr after ingestion of the single dose. The mean area under the rifapentine plasma concentration-time curve [AUC(0-->infinity)] was 325 micrograms.hr ml and the mean elimination half-life (t1/2) was 16.3 hr. Plasma concentrations for the 25-desacetyl metabolite peaked at 15.4 hr after the rifapentine dose and declined with a terminal half-life of 17.3 hr. These rifapentine and 25-desacetyl-rifapentine PK data in women were compared to data generated previously in healthy men. Striking similarities in the PK profiles of parent drug and metabolite were found in the two populations. Mean differences in rifapentine CL/F (12%) and t1/2 (2%) were small. The only adverse event reported in the female subjects was discoloration of the urine. Based on these PK and safety data, no dosage adjustments for rifapentine based on gender are recommended.

Selection of doses for phase II clinical trials based on pharmacokinetic variability consideration

Pharmacokinetic variability is an important component of the total variability in drug response, but Phase II dose-response trials frequently are designed without considering this important factor. Mixed-effects model simulation was performed to examine overlap of patient area under the concentration-time curve (AUC) values between doses for drugs with differing inter- and intrapatient pharmacokinetic variability. Based on the results of this simulation, a dose increment of at least threefold is needed to ensure that drug exposure does not overlap in at least 50% of the patient population for a drug that exhibits greater than 25% variability. In contrast, an increment factor of 2 is normally sufficient to produce the same degree of resolution when the variability is less than 25%. These results suggest that a more aggressive choice of administration increments could lead to a better separation in systemic drug exposure between doses. This needs to be balanced against the therapeutic window of an individual drug product.

Pharmacokinetics of MDL 26479, a novel benzodiazepine inverse agonist, in normal volunteers

MDL 26479 is a new drug undergoing clinical evaluation for the treatment of depression and for memory loss associated with Alzheimer's disease. As part of a dose tolerance trial, the single- (SD) and multiple-dose (MD) pharmacokinetics of MDL 26479 were evaluated in healthy male volunteers. SDs ranging from 2 to 465 mg, and doses of 30, 60, and 120 mg administered twice daily for 28 d, were examined. Serial blood samples were collected for up to 48 h. Plasma MDL 26479 concentrations were determined by HPLC. Plasma MDL 26479 concentration versus time profiles increased rapidly, followed by multiexponential decline. Time to maximum plasma concentration increased over the 230-fold SD range from 0.5 to 3.8 h. Maximum concentrations and areas under the concentration versus time curves increased disproportionately with dose. Apparent oral clearance estimates decreased from 52.9 to 13.8 Lh-1. MD pharmacokinetic parameters for doses from 30 to 120 mg were consistent with those observed following SD, thus indicating that SD pharmacokinetics are predictive of MD. SD and MD terminal half-life estimates were similar and independent of dose.

An investigation of the dose proportionality of deflazacort pharmacokinetics

The dose proportionality of deflazacort was assessed following single-dose oral administration at doses of 3, 6, and 36 mg to 24 healthy young adult volunteers. The active metabolite of deflazacort (21-desacetyl deflazacort) was monitored in plasma using a sensitive, semi-microbore liquid chromatographic method. Cmax averaged 10.4 +/- 5.0, 19.8 +/- 7.5, and 132.6 +/- 52.5 ng mL-1 for the 3, 6, and 36 mg doses, respectively. AUC(0-infinity) averaged 38.5 +/- 37.1, 64.9 +/- 20.8, and 411.7 +/- 148.5 ng h mL-1 for the same three doses, respectively. Elimination half-life ranged from 1.9 +/- 0.5 h at the 6 mg dose to 2.4 +/- 1.5 h at the 36 mg dose. Regression analyses of dose versus Cmax and AUC(0-infinity) yielded intercepts which were not significantly different from zero (p > 0.05) and slopes which were significant (p < 0.05). Regression analysis of dose versus apparent oral clearance yielded a slope which was not significantly different from zero (p > 0.05). These data indicate that deflazacort exhibits dose-proportional pharmacokinetics.

Percutaneous absorption of ketoprofen from different anatomical sites in man

PURPOSE

The purpose of this study was to investigate the percutaneous absorption of ketoprofen applied topically to different anatomical sites on the body.

METHODS

The study design was a randomized, four-way crossover in 24 healthy male subjects. One gram of ketoprofen 3% gel (30 mg dose) was applied every six hours for 25 doses over a 100 cm2 of the back, arm, and knee. A 0.5 ml of ketoprofen solution (60 mg/ml) was applied to the back as a reference treatment. Plasma and urine samples were obtained for the assay of racemic ketoprofen and ketoprofen enantiomers (S and R), respectively.

RESULTS

The relative bioavailabilities of ketoprofen gel were 0.90 +/- 0.50, 1.08 +/- 0.63, and 0.74 +/- 0.38 when applied to the back, arm, and knee, respectively. The plasma ketoprofen C(max) for gel applied to the back and arm are similar (p > 0.05) but C(max) was lower when applied to the knee (p < 0.05). The time to C(max) ranged from 2.7 to 4.0 hours and was similar for gel treatments on the back and arm, but no longer for the knee treatment. The fraction of dose excreted in urine as total S and R enantiomers ranged from 5.41 to 9.10%.

CONCLUSIONS

The percutaneous absorption of ketoprofen was similar when applied to either the back or arm but was lower when applied to the knee.

The relative bioavailability of two marketed controlled release diltiazem dosage forms at steady state in healthy volunteers

This study was conducted to determine the relative bioavailability of Dilacor XR capsules compared to Cardizem CD capsules at both low (180 mg d-1) and high (540 mg d-1) dose levels. Trough and serial plasma samples were obtained and pharmacokinetic parameters were calculated from the steady state concentration-time profiles. Mean steady state plasma diltiazem concentrations (AUCss(0-24)) of Dilacor XR were 19% and 26% lower than those of Cardizem CD for the 180 mg d-1 and 540 mg d-1 dose levels, respectively. In addition, Dilacor XR had lower mean Cmax,ss, Tmax,ss, Cmin,ss, and trough values than Cardizem CD with percentage differences ranging from 17% to 29%. The variability (%CV) in the data from the Dilacor XR treatments was higher for each calculated pharmacokinetic parameter compared to the Cardizem CD treatments. The %CV for Dilacor XR ranged from 34% to 104% while the %CV for Cardizem CD ranged from 21% to 49%. From these results, it may be concluded that Dilacor XR is not bioequivalent to Cardizem CD at steady state doses of 180 mg d-1 and 540 mg d-1.

Pharmacokinetics of 5-aminosalicylic acid from controlled-release capsules in man

One gram single dose of Pentasa controlled-release capsules was administered to 24 healthy volunteers under fasting condition. Mean plasma 5-aminosalicylic acid (5-ASA) and acetyl 5-ASA concentrations peaked at 0.53 microgram.ml-1 and 1.33 micrograms.ml-1 from 3 to 4 hours following dosing, respectively. The half-lives of both compounds could not be determined as absorption of 5-ASA was continuous throughout the gastrointestinal tract. An average of 29.4% (CV: 27%) of the dose was excreted in the urine primarily as acetyl 5-ASA. Up to 91.1% of the dose was released from the capsules. Forty percent of the dose (CV: 40%) was eliminated in the feces, with 8.9% of the dose remained as formulation bounded 5-ASA, indicating that controlled-release capsules continue to release drug throughout the GI tract. 5-ASA contributed 46.7% of the salicylates eliminated in the feces and acetyl 5-ASA accounted for the balance. Controlled-release capsules produced three times more total salicylates and 10 times more total and free 5-ASA in the feces than did 5-ASA suspension. Thus, while lower systemic levels of salicylates were absorbed, greater therapeutic quantities of 5-ASA were available in the bowel.

Population pharmacokinetics of teicoplanin in patients with endocarditis

Teicoplanin is a new glycopeptide antibiotic, active against aerobic and anaerobic gram-positive bacteria. The drug is intended for the treatment of systemic infections including endocarditis. In two U.S. clinical safety and efficacy trials, loading doses of 6 to 30 mg/kg doses of teicoplanin were administered initially to 197 patients, followed by once-a-day treatment of approximately the same doses over several weeks. Blood samples were collected sporadically during the study to monitor serum teicoplanin concentrations either by FPIA or microbiological assay. Nonlinear mixed-effects modeling was performed on these data to characterize the population pharmacokinetics of teicoplanin that were best described by a two-compartment model. Patient body weight, concomitant gram-positive drug treatment, and serum creatinine had significant influences on systemic clearance (CL) of the glycopeptide. In addition, body weight affected the volume of distribution of the central compartment (Vc). Other demographic factors such as age, gender, etc., had no effects. The FPIA assay method was more precise than the microbiological assay.

A comparison of population and standard two-stage pharmacokinetic analyses of vigabatrin data

Vigabatrin (VGB), an irreversible inhibitor of GABA, is being developed as an add-on therapy for uncontrolled complex partial seizure. A single-dose study was conducted in three groups of subjects with normal, mild-to-moderate, and moderate-to-severe renal impairment to examine the effect of renal function on the pharmacokinetics of VGB. Serial blood samples were collected up to 60 h following a single 750 mg oral dose of VGB for the quantitation of drug concentrations. The plasma VGB concentration-time data were analyzed by mixed-effects modeling to estimate population pharmacokinetic parameters and to identify any significant demographic covariates. The parameters of VGB were also calculated by standard two-stage techniques and then compared to the results obtained using the mixed-effects analysis. Population VGB plasma concentration-time profiles were best described by a two-compartment model with zero-order absorption. Creatinine clearance was observed to significantly affect the oral clearance of VGB (p < 0.05), i.e. a linear increasing relationship existed between the two variables. Other demographic factors had no influence on VGB pharmacokinetics. There were agreements in the oral clearance, apparent volume of distribution during elimination, and half-life estimates calculated by both methods. In addition, the conventional technique identified a linear relationship between oral and creatinine clearances. In summary, mixed-effects modeling of serial vigabatrin data validated results determined by the standard two-stage technique.

Single and multiple oral dose pharmacokinetics of clentiazem in normal volunteers

This study was designed to determine the pharmacokinetics and dose proportionality of clentiazem (CLZ) after single doses (SD) of 20, 40, and 80 mg and multiple dose administration (SS) of 40, 80, and 160 mg/day for 5 days. The study was an open-label, randomized four-period complete crossover design. Twenty-four healthy male volunteers participated in the study, and blood samples were drawn over 48 hours after both SD and SS. Plasma samples were analyzed for CLZ and three metabolites by high-pressure liquid chromatography. After SD, the area under the plasma concentration-time curve (AUC0-infinity) and maximum concentration (Cmax) increased disproportionately with the increase in dose. At steady-state, a twofold increase in dose (20 to 40 mg twice daily and 40 to 80 mg twice daily) resulted in an increase in AUCss of 2.14- and 2.51-fold, respectively. Oral clearance of CLZ decreased (203.8 L/h at 40 mg/d to 140.2 L/h at 160 mg/d) and bioavailability increased (0.35 at 40 mg/d to 0.50 at 160 mg/d) with increasing doses. The terminal half-life of CLZ remained unchanged with increasing doses (13.7-15.5 hours). The ratios of AUCss to AUC0-infinity at SD ranged from 1.13 to 1.27, indicating no significant accumulation of CLZ (P > .05). The AUC ratio of N-desmethyl CLZ to that of CLZ remained constant after SD. On SS, however, there was a small decrease in this ratio with increasing dose (0.77 at 40 mg/d to 0.61 at 160 mg/d). These results indicate that the degree of nonlinearity observed with CLZ pharmacokinetics may largely be due to saturable first-pass metabolism.

Pharmacokinetics of clentiazem after intravenous and oral administration in healthy subjects

This study characterized the pharmacokinetics of clentiazem (CLZ) after a single intravenous bolus (IV) and oral (PO) dose in humans. Twenty-four healthy male subjects (28.5 +/- 5.2 years; 77 +/- 8.2 kg) received IV (20 mg) and PO (80 mg) doses of CLZ as part of a four-way, randomized, complete crossover study. Serial blood samples were drawn up to 48 hours after administration of the drug. Plasma samples were analyzed for CLZ and three metabolites by a high-pressure liquid chromatography method. The values (mean [CV, %]) for systemic clearance, volume of distribution at steady-state, and half-life of CLZ were 63.6 L/hour (23.5), 756.1 L (19.1), and 10.6 hours (33.1), respectively, after IV administration. The peak plasma CLZ concentration (Cmax) and time to Cmax were 37.0 ng/mL (38.7) and 3.7 hours (22.9), respectively, with a lag time after PO administration. The absolute bioavailability of PO CLZ was 45% (30.7). The ratio of area under the curve of N-desmethyl CLZ to that of CLZ increased from 0.15 (57.0) after IV to 0.60 (21.4) after PO administration, suggesting a significant first-pass effect. The mean residence time and mean absorption time of CLZ were 12.3 hours (24.3) and 3.1 hours (88.1), respectively. The plasma concentration-time data of CLZ can be described by either a one- or two-compartment pharmacokinetic model.

Pharmacokinetics and pharmacodynamics of intravenous diltiazem in patients with atrial fibrillation or atrial flutter

BACKGROUND

Diltiazem, a calcium channel blocker, has been shown to be safe and effective in the treatment of patients in atrial fibrillation and/or atrial flutter. However, there have been no pharmacokinetic/pharmacodynamic studies of diltiazem in these patients.

METHODS AND RESULTS

The pharmacokinetics and pharmacodynamics of intravenous diltiazem were determined in 32 patients with atrial fibrillation or atrial flutter (mean +/- SD age, 66 +/- 7 years; mean baseline heart rate, 131 +/- 10 beats per minute) after 20 mg or 20 mg followed by 25-mg bolus doses and a 10 and 15 mg/hr infusion for 24 hours. After the 10 and 15 mg/hr infusions of diltiazem, mean +/- SD elimination half-life was 6.8 +/- 1.8 and 6.9 +/- 1.5 hours, volume of distribution was 411 +/- 151.8 and 299 +/- 70.8 I, and systemic clearance was 42 +/- 12.4 and 31 +/- 8.3 l/hr, respectively. Percentages of the plasma concentrations of the principal metabolites desacetyldiltiazem and N-desmethyldiltiazem to diltiazem were < 15% and < 10%, respectively. Thirty of 32 patients maintained response throughout the 24-hour infusion of diltiazem. Using a sigmoidal Emax pharmacodynamic model, a strong relation (mean +/- SD r2, 0.78 +/- 0.2) was observed between plasma diltiazem concentration and percent heart rate reduction. Mean +/- SD Emax (maximum percent reduction in heart rate from baseline) and EC50 (plasma diltiazem concentration that achieves half Emax) were 52 +/- 17% and 110 +/- 84 ng/ml, respectively. The model predicts that mean plasma diltiazem concentration of 79, 172, and 294 ng/ml are required to produce a 20%, 30%, and 40% reduction in heart rate, respectively. A relation between plasma diltiazem concentration and percent change in systolic blood pressure (SBP) or diastolic blood pressure (DBP) from baseline was not observed (mean +/- SD r2, SBP/DBP: 0.35 +/- 0.24/0.36 +/- 0.2). There were no untoward side effects observed.

CONCLUSIONS

First, the pharmacokinetics of diltiazem in patients with atrial fibrillation or atrial flutter is nonlinear with an apparent dose-dependent decrease in systemic clearance with increasing infusion rate. Second, using a sigmoidal Emax model, there is a strong relation between plasma diltiazem concentration and percent heart rate reduction. Third, the plasma concentrations of the principal metabolites desacetyldiltiazem and N-desmethyldiltiazem are low and are not expected to contribute significantly to the pharmacodynamics of intravenous diltiazem in these patients.

Amiodarone pharmacokinetics. III. Influence of thyroid dysfunction on amiodarone absorption and disposition

Hypothyroid, hyperthyroid and euthyroid rats were given 45 or 80 mg/kg i.v. or 100 mg/kg p.o. of amiodarone hydrochloride to determine the effects of thyroid dysfunction on the absorption and disposition characteristics of amiodarone. Serial blood samples were obtained for 48 hr and assayed for amiodarone and desethylamiodarone by high-performance liquid chromatography. In the hypothyroid rats, reductions in amiodarone clearance (CL) of 73% (26.9-7.3 ml/min/kg) and 61% (18.7-7.3 ml/min/kg) were observed with the 45- and 80-mg/kg i.v. bolus doses, respectively. Accompanying the decreases in CL were increases in the terminal disposition half-life (T1/2 gamma), 89% (18-34 hr) with the 45-mg/kg dose and 185% (20-57 hr) after the 80-mg/kg dose. The steady state (Vss) and apparent (Vd) volumes of distribution were smaller at the lower dose but were invariant after administration of the larger dose. Furthermore, the central compartment volume was not altered. In the hyperthyroid rats, a 67% increase in CL (12.8-21.4 ml/min/kg) and 75 to 80% increases in Vss (15.5-27.1 liters/kg) and Vd (25.0-44.8 liters/kg) were observed with the 45-mg/kg of amiodarone dose. However, no changes in CL, Vd and Vss were seen with the 80-mg/kg dose. Furthermore, gamma, T1/2 gamma and central compartment volume were not altered in the hyperthyroid rats. The effects of thyroid dysfunction on the p.o. bioavailability characteristics of amiodarone were minor. These studies demonstrated that the disposition kinetics of amiodarone are altered in hypo- and hyperthyroidism.

Amiodarone pharmacokinetics. II. Disposition kinetics following subchronic administration in rats

A 30 mg kg-1 intravenous bolus of 14C-amiodarone (19 microCi kg-1) was given to male Sprague-Dawley rats pretreated with 0 (vehicle), 25 or 100 mg kg-1 day-1 of amiodarone HCl orally for 37-42 days to determine the effects of dose and duration of administration on the disposition kinetics of amiodarone. Serial blood samples and total urine were collected over 48 hours and assayed for 14C-amiodarone by liquid scintillation counting following separation by HPLC. In all three groups, the blood 14C-amiodarone concentration-time curves declined bioexponentially with terminal half-lives (t1/2 beta) ranging from 14-22 hours. No differences in beta, t1/2 beta, or central compartment volume (Vc) were observed between the three groups of rats. In the rats pretreated with 100 mg kg-1 day-1 of amiodarone HCl for 5-6 weeks, amiodarone clearance (CL) and steady state volume of distribution (Vss) were reduced 52 per cent (12.2 to 5.9 ml min-1 kg-1) and 41 per cent (11.73 to 6.97 l kg-1), respectively. At the lower amiodarone daily dose, no changes in CL or Vss were observed. Negligible levels of radioactivity were detected in the urine. Amiodarone accounted for approximately 30-40 per cent of the total radioactivity in each blood specimen. This study demonstrated that CL and Vss were dose-dependent, and that beta, t1/2 beta and Vc were dose-independent. The results further suggested that the disposition kinetics of amiodarone were independent of the duration of drug administration.

Amiodarone pharmacokinetics. I. Acute dose-dependent disposition studies in rats

Single intravenous bolus doses of amiodarone hydrochloride of 30, 60, 90 and 120 mg/kg were administered to male Sprague-Dawley rats to determine the effects of dose on amiodarone pharmacokinetics. Serial blood samples and total urine were collected over 48 hr and assayed for amiodarone and desethylamiodarone by HPLC. The blood amiodarone concentration-time curves for the four doses were best described by a triexponential equation with terminal half-lives (t1/2 gamma) ranging from 17 to 20 hr. Over the dose range studied, no changes in gamma, t1/2 gamma, or central compartment volume (Vc = 1.2-1.4 L/kg) were observed. On the other hand, reductions in amiodarone clearance (CL) and steady-state volume of distribution (Vss) of 44% (17.7 to 10.0 ml/min per kg) and 50% (16.4 to 8.2 L/kg), respectively, were noted as the dose of amiodarone increased. The conversion of amiodarone to desethylamiodarone (fm) was dose-independent and amounted to approximately 10% of each amiodarone dose. No amiodarone or desethylamiodarone was detected in the urine of any of the treated animals. The blood-to-plasma concentration ratio of amiodarone was concentration-independent and therefore did not account for the dose-dependent changes in Vss and CL observed. The data suggested that the dose-dependent changes noted were due to an alteration in the volume (s) of the peripheral tissue compartment(s).

Sorption of amiodarone to polyvinyl chloride infusion bags and administration sets

The loss of amiodarone from i.v. admixtures to flexible polyvinyl chloride (PVC) infusion bags and i.v. administration sets was studied. Admixtures containing amiodarone hydrochloride 600 micrograms/mL and either 5% dextrose injection or 0.9% sodium chloride injection were stored at room temperature in glass bottles (both with and without contact of the drug solution with the rubber bottle closure), in flexible PVC bags, or in rigid PVC bottles. After 120 hours, the contents of each flexible PVC bag were emptied and replaced by methanol, which was allowed to remain in the bag for an additional 120 hours and was then analyzed for amiodarone content. To determine availability of amiodarone after infusion through a 1.8-m PVC i.v. administration set, solutions stored in glass containers were run through the set at 0.5 mL/min for 90 minutes. Samples of drug solutions were collected at appropriate intervals and analyzed by a stability-indicating high-performance liquid chromatography (HPLC) assay. Admixtures containing 0.9% sodium chloride injection were not stable; visual incompatibility was evident after 24 hours of storage in glass bottles, and no further testing was performed. In admixtures containing 5% dextrose injection that were stored in 50-mL flexible PVC bags, 60% of the initial amiodarone concentration remained after 120 hours; approximately half of the lost drug was recovered with the methanol. In effluent collected from the PVC administration set, 82% of the initial amiodarone concentration remained. Amiodarone concentrations did not decrease appreciably, after storage in glass or rigid PVC bottles, indicating that drug loss was probably affected by the plasticizer, di-2-ethylhexyl phthalate.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid liquid chromatographic assay for the determination of amiodarone and its N-deethyl metabolite in plasma, urine, and bile

A rapid high-performance liquid chromatographic assay was developed for the determination of amiodarone (1) and its N-deethyl metabolite (desethylamiodarone, 2) in plasma, urine, and bile. Analysis was performed on a C18 reversed-phase column and precolumn using a mobile phase consisting of methanol:water:58% ammonium hydroxide (94:4:2) delivered at a flow rate of 1.5 mL/min. The eluant was monitored at 244 nm. Under these conditions, 1, 2, and the internal standard eluted with retention times of 5.5, 4.6, and 6.8 min, respectively. Samples (100 microL) of plasma were prepared by precipitating the plasma proteins with acetonitrile containing the internal standard and injecting an aliquot of the supernatant directly onto the column. Samples (100 microL) of urine and bile were prepared for injection by acidifying the sample with concentrated HCl and then extracting the mixture with six volumes of 2,2-dimethoxyproprane. The recovery of 1 and 2 from plasma was virtually complete. The recovery from urine and bile was 80-90% for 1 and 60-65% for 2. The limit of sensitivity of both compounds in plasma was 100 ng/mL. For urine and bile, the detection limits were 1 and 5 micrograms/mL, respectively. Over the plasma concentration range of 0.1-10.0 micrograms/mL, the within-day CV ranged from 1 to 10% for 1 and from 1 to 8% for 2. The between-day CV ranged from 2 to 12% and from 1 to 17% for 1 and 2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)