Amarnath Sharma

Phase I Dose Escalation Study of the Anti–Insulin-Like Growth Factor-I Receptor Monoclonal Antibody CP-751,871 in Patients with Refractory Solid Tumors

Purpose: This phase I study was undertaken to define the maximum tolerated dose, safety, and pharmacokinetic profile of CP-751,871. Experimental Design: Using a rapid dose escalation design, patients with advanced nonhematologic malignancies were treated with CP-751,871 in four dose escalation cohorts. CP-751,871 was administered i.v. on day 1 of each 21-day cycle. Pharmacokinetic evaluation was done in all treatment cohorts during cycles 1 and 4. Results: Twenty-four patients received 110 cycles at four dose levels. The maximum tolerated dose exceeded the maximal feasible dose of 20 mg/kg and, thus, was not identified. Treatment-related toxicities were generally mild. The most common adverse events were hyperglycemia, anorexia, nausea, elevated aspartate aminotransferase, elevated γ-glutamyltransferase, diarrhea, hyperuracemia, and fatigue. At 20 mg/kg, 10 of 15 patients experienced stability of disease. Two of these patients experienced long-term stability. There were no objective responses. Pharmacokinetic analysis revealed a dose-dependent increase in CP-751,871 exposure and ∼2-fold accumulation on repeated dosing in 21-day cycles. Plasma concentrations of CP-751,871 attained were several log-fold greater than the biologically active concentration. Treatment with CP-751,871 increased serum insulin and human growth hormone levels, with modest increases in serum glucose levels. Conclusions: CP-751,871 has a favorable safety profile and was well tolerated when given in continuous cycles. At the maximal feasible dose of 20 mg/kg, there was a moderate accumulation in plasma exposure, and most of the treated patients experienced stability of disease.

Steady-State Pharmacokinetic and Safety Profiles of Voriconazole and Ritonavir in Healthy Male Subjects

ABSTRACT Since there is a likelihood of coadministration of voriconazole and ritonavir, two studies were conducted to evaluate the potential of drug interaction. Study A was a randomized, placebo-controlled, two-period, parallel-group trial (n = 34). Study B had the same design without the placebo group (n = 17). In period 1, subjects received 200 mg voriconazole or placebo twice daily (BID) for 3 days (400 mg BID on day 1). In period 2, following a 7-day washout, subjects received ritonavir alone at 400 mg BID (study A) or 100 mg BID (study B) for 10 days (days 11 to 20), and then ritonavir was coadministered with 200 mg BID voriconazole or placebo for the next 10 days (days 21 to 30). Serial plasma samples were collected on days 3, 20, and 30, and safety data were collected throughout the study. High-dose (400 mg BID) ritonavir substantially reduced the steady-state mean voriconazole exposure (area under the concentration-time curve from 0 to 12 h [AUC0-12], −82%; maximum concentration [Cmax], −66%). However, the effect of low-dose (100 mg BID) ritonavir was less pronounced (AUC0-12, −39%; Cmax, −24%). The decrease in voriconazole exposure was probably due to the induction of CYP2C19 and CYP2C9 by ritonavir. It is interesting that one subject in each study exhibited the opposite effect of ritonavir on voriconazole exposure (a 2.5- to 3-fold increase), probably due to lack of CYP2C19. Voriconazole had no apparent effect on the exposure of high-dose ritonavir but slightly decreased the exposure of low-dose ritonavir (AUC0-12, −14%; Cmax, −24%). The safety profile of combination therapy was not notably different from that of voriconazole or ritonavir alone. Due to the significant effect of ritonavir on voriconazole exposure, coadministration of voriconazole with 400 mg BID ritonavir is contraindicated; coadministration with 100 mg BID ritonavir should be avoided, unless an assessment of the benefit/risk to the patient justifies the use.

Pharmacokinetic Interaction Between Voriconazole and Efavirenz at Steady State in Healthy Male Subjects

A randomized, placebo–controlled (with respect to voriconazole), 2‐period, multiple‐dose intragroup fixed‐dose sequence study was conducted in 34 healthy male subjects to evaluate the interactions between voriconazole (triazole antifungal agent) and efavirenz (reverse transcriptase inhibitor). In period 1, subjects received 200 mg twice‐daily (bid) voriconazole (n = 17) or placebo (n = 17) for 3 days (400‐mg bid loading doses on day 1). In period 2, following a 7‐day washout, subjects received 400 mg once‐daily (qd) efavirenz alone for 10 days (days 11–20). Then efavirenz was coadministered with 200 mg bid voriconazole or placebo for the next 9 days (days 21–29). Serial plasma voriconazole and efavirenz concentrations were measured on days 3, 19, and 29, and the safety data were collected throughout the study. The 400‐mg qd efavirenz dose substantially reduced the steady‐state mean voriconazole area under the curve over the dosing interval (AUC0–12) by 80% (90% confidence interval [CI], 75%–84%) and peak concentration (Cmax) by 66% (90% CI, 57%–73%). The decrease in voriconazole exposure during coadministration is probably mainly due to the induction of CYP2C19 and CYP2C9 by efavirenz. The 200 mg bid voriconazole increased the steady‐state mean AUC0–24 and Cmax of efavirenz by 43% (90% CI, 36%–51%) and 37% (90% CI, 29%–46%), respectively. The increase in efavirenz exposure during coadministration is probably due to the inhibition of CYP3A4 by voriconazole. Coadministration of 200 mg bid voriconazole with 400 mg (or higher) qd efavirenz is contraindicated due to the clinically significant effect of efavirenz on voriconazole pharmacokinetics.

Comparative Pharmacokinetics of Azithromycin in Serum and White Blood Cells of Healthy Subjects Receiving a Single-Dose Extended-Release Regimen versus a 3-Day Immediate-Release Regimen

ABSTRACT The pharmacokinetic profiles of azithromycin given as a single-dose regimen (2.0-g extended-release microspheres) were characterized in serum and white blood cells (WBC) and compared with those of a 3-day regimen (a 500-mg immediate-release tablet once daily; total dose, 1.5 g) in an open-label, randomized, parallel-group study of 24 healthy adult subjects. Serial blood samples were collected up to 5 days after the start of dosing for both regimens. Safety assessments were conducted throughout the study. A single 2.0-g dose of azithromycin microspheres achieved significantly higher exposures in serum and WBC during the first 24 h after the start of dosing than a 3-day regimen: an approximately threefold higher area under the curve from time zero to 24 h postdose (AUC0-24) and an approximately twofold higher mean peak concentration on day 1. The single-dose regimen provided total azithromycin exposures in serum and WBC similar to those of the 3-day regimen, as evidenced by the similar AUC0-120 and trough azithromycin concentrations in serum and WBC (mononuclear leukocytes [MNL] and polymorphonuclear leukocytes [PMNL]). For both regimens, the average total azithromycin exposures in MNL and PMNL were approximately 300- and 600-fold higher than those in serum. Azithromycin concentrations in MNL and PMNL remained above 10 μg/ml for at least 5 days after the start of dosing for both regimens. This “front-loading” of the dose on day 1 is safely achieved by the extended-release microsphere formulation, which maximizes the drug exposure at the time when the bacterial burden is likely to be highest.

CYP3A and P-glycoprotein activity induction with St. John's Wort in healthy volunteers from 6 ethnic populations.

I has been reported that St. John’s Wort (SJW) may have inducing effects on the cytochrome P450 enzyme system, specifically the CYP3A4 isoform (CYP3A4) and the intestinal P-glycoprotein (Pgp) efflux membrane transporter. This may have profound implications on patients taking medications that are substrates for Pgp and/or CYP3A4. Ethnic difference is an important factor to determine drug metabolism and response. Varying results have been reported in studies evaluating ethnic differences in the pharmacokinetic disposition of Pgp/CYP3A4 substrates and suggest that these differences may be attributed to ethnically associated differences in intestinal Pgp and CYP3A4 activity. Fexofenadine and midazolam have been widely used as probes for intestinal and hepatic Pgp transporter and CYP3A enzyme activities in human interaction studies. In vivo studies examining SJW induction on CYP3A4 and Pgp substrates’ pharmacokinetic (PK) parameters and its relationship among various ethnic groups have not been examined extensively. The purpose of the current study was to investigate whether any differences in the inducibility of Pgp and CYP3A by SJW are present among 6 ethnic groups in healthy volunteers using fexofenadine and midazolam as probes.

Pharmacokinetic Interaction between Voriconazole and Methadone at Steady State in Patients on Methadone Therapy

ABSTRACT This trial was aimed to estimate the pharmacokinetic interaction between voriconazole and methadone at steady state in male patients on methadone therapy and to characterize the safety and tolerability profile during the coadministration. Twenty-three patients on individualized methadone therapy (30 to 100 mg once daily) were enrolled into this randomized, patient- and investigator-blind, placebo-controlled, parallel-group study. Methadone pharmacokinetic samples were collected from patients receiving methadone alone as the baseline before they were randomized to coadminister either 200 mg voriconazole twice daily (BID) (400-mg BID loading doses on the first day) (n = 16) or matching placebo (n = 7) for the next 5 days. Pharmacokinetic samples for methadone and voriconazole were collected on the last day of voriconazole dosing. The safety data were collected throughout the study. Voriconazole increased the steady-state exposure of pharmacologically active enantiomer (R)-methadone: the mean area under the concentration-time curve from 0 to 24 h (AUC0-24) was increased by 47.2% (90% confidence intervals [CI]: 37.7%, 57.4%), and the mean peak concentration (Cmax) was increased by 30.7% (90% CI: 22.2%, 39.8%). The magnitude of increase in (S)-methadone exposure was greater than that of (R)-methadone: the AUC0-24 was increased by 103.4% (90% CI: 85.0%, 123.6%), and the Cmax was increased by 65.4% (90% CI: 52.6%, 79.2%). Methadone appeared to have no effect on the steady-state voriconazole pharmacokinetics compared to the historical data for voriconazole alone. Methadone patients receiving voriconazole showed no signs or symptoms of significant opioid withdrawal or overdose. Coadministration of 200 mg voriconazole BID with methadone was generally safe and well tolerated. Nevertheless, caution should be exercised when voriconazole is coadministered with methadone due to the increase in (R)-methadone exposure, which in turn may require a dose reduction of methadone.

Clinical Pharmacokinetics and Gastrointestinal Tolerability of a Novel Extended-Release Microsphere Formulation of Azithromycin

Background and objectiveA novel oral, extended-release, microsphere formulation of azithromycin (AZSR) was developed to improve the gastrointestinal tolerability profile while allowing administration of an entire treatment course of azithromycin in a single dose. Several phase I clinical pharmacology studies were conducted to (i) identify a well-tolerated single-dose formulation that met a predefined exposure target; and (ii) evaluate the effect of food and antacid on the absorption of this formulation. Of these, five pivotal studies are described here.MethodsThe pharmacokinetic profile of AZSR was compared with that of the commercially available immediate-release azithromycin formulation (AZM) in an open-label, crossover, single-dose study (Study A), and their gastrointestinal tolerability profiles were compared in an observer-blind, parallel group, single-dose study (Study B). The effects of food (a high-fat meal and a standard meal) and antacid (a single 20mL dose of Maalox® Regular Strength, containing magnesium hydroxide, aluminium hydroxide and simethicone) on the absorption of azithromycin from AZSR were evaluated in three separate open-label, crossover, single-dose studies (Studies C, D and E). Healthy adult subjects were enrolled in all five studies, and all subjects were evaluable for tolerability. The dose used for all azithromycin formulations was 2.0g. Serum azithromycin concentrations were determined using a validated high-performance liquid chromatography/electrochemical detection method, and pharmacokinetic parameters were analysed using noncompartmental methods.Results377 subjects received a single 2.0g dose of azithromycin as AZSR and/or AZM in the five studies. Compared with AZM, AZSR had a slower absorption rate (57% decrease in the mean peak concentration [Cmax] and an approximate 2.5-hour delay in the time to reach Cmax [tmax]), with a mean relative bioavailability of 82.8%, which met the predefined exposure target (at least 80% bioavailability relative to AZM). Compared with AZM, AZSR was associated with significantly lower rates of nausea and vomiting. A high-fat meal increased the mean area under the serum concentration-time curve [AUC] from time zero to 72 hours post-dose (AUC72h) by 23% and increased the Cmax of azithromycin by 115%. A standard meal increased the mean Cmax by 119% but had no clinically significant effect on the AUC72h. AZSR appeared to be better tolerated in the fasted state than in the fed state. The AUC72h and Cmax of AZSR were not significantly affected by co-administration with a single dose of antacid.ConclusionsThe extended-release microsphere formulation of azithromycin, AZSR, allows administration of an entire therapeutic course of azithromycin as a well-tolerated single 2.0g dose. This formulation should be administered on an empty stomach and can be co-administered with antacids.

Phase 1 and Pharmacokinetic Study of Intravenous Irinotecan in Refractory Solid Tumor Patients with Hepatic Dysfunction

Purpose: To determine the recommended starting doses and pharmacokinetics of irinotecan in cancer patients with impaired liver function treated on a weekly schedule. Experimental Design: Patients with solid tumors who had impaired liver function were enrolled into four groups based on baseline serum total bilirubin and aspartate aminotransferase (AST)/alanine aminotransferase (ALT): Group 1 (n = 19): total bilirubin 1.5 to 3.0 × institutional upper limit of normal (IULN) and ALT/AST ≤5.0 × IULN; Group 2 (n = 7): total bilirubin 3.1 to 5.0 × IULN and ALT/AST ≤5.0 × IULN; Group 3 (n = 6): total bilirubin ≤1.5 × IULN and ALT/AST 5.1 to 20.0 × IULN; Group 4 (n = 10): total bilirubin 1.5 to 3.0 × IULN and ALT/AST 5.1 to 20.0 × IULN. Irinotecan was given as a 90-minute i.v. infusion weekly for the first 4 weeks in each 6-week cycle at starting doses which escalated from 40 to as much as 75 mg/m2. After the first treatment, doses were adjusted based on individual patient toxicities. Starting doses for patients with hepatic dysfunction were derived from the maximum tolerated doses noted in the four hepatic dysfunction groups. Results: Forty-two patients were treated. Among the most frequent adverse events were neutropenia (41%, grades 3/4), diarrhea (15%, grades 3/4), nausea (10%, grade 3), and vomiting (5%, grades 3/4). Two patients died from drug-induced neutropenic sepsis. Two patients had objective tumor responses (complete response, liver metastases from unknown primary; partial response, colon cancer). Hepatic dysfunction reduced irinotecan clearance while increasing relative exposure to the active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). SN-38 exposures in patients receiving doses of 40 to 75 mg/m2 were comparable to exposures in patients with normal liver function treated with a starting dose of 125 mg/m2. Conclusions: Irinotecan starting doses that seem to be safe for hepatically impaired patients treated with the weekly schedule are 60, 50, 60, and 40 mg/m2 for groups 1 to 4, respectively. At these starting doses, exposure to SN-38 and the adverse event profile are similar to that observed in patients with normal liver function and antitumor activity can be observed.

CYP3A and P-glycoprotein induction with St. John's wort in healthy volunteers of selected ethnic populations

Clinical Pharmacology & Therapeutics (2003) 73, P93–P93; doi:

PI-13Pharmacokinetics and pharmacodynamics of a HER2 tyrosine kinase inhibitor CP-724714 in patients with advanced malignant HER2 positive solid tumors

To evaluate the pharmacokinetics (PK) and pharmacodynamics (PD) of CP‐724714, a novel HER2 tyrosine kinase inhibitor under development for the treatment of advanced HER2‐overexpressing cancers.