Multiple-dose pharmacokinetics and safety of trovafloxacin in healthy volunteers

Transcription

1 Journal of Antimicrobial Chemotherapy (1996) 37, Multiple-dose pharmacokinetics and safety of trovafloxacin in healthy volunteers Renli Teng, Theodore E. Liston and Stephen C. Harris Central Research Division, Pfizer Inc., Groton, CT 06340, USA The multiple-dose pharmacokinetics and safety of trovafloxacin (CP-99,219), a new fluoroquinolone antibacterial agent, were evaluated in healthy male volunteers. Trovafloxacin was administered orauy at 100 or 300 mg as a single dose followed by a 3 day washout period, and then was dosed once-daily for 14 consecutive days. Multiple serum and urine samples were collected on days 1 and 17 and were analysed for trovafloxacin concentrations by HPLC-UV. Following single doses, the mean C» values (mean ± S.D.) were 1.0 ± 0.3 and 2.9 ± 0.4 mg/l for the 100 and 300 mg, respectively; those after 14-day consecutive daily dosing (day 17) were 1.1 ±0.2 and 3.3 ± 0.5 mg/l, respectively. Trovafloxacin was rapidly absorbed and reached " approximately 1 h after dosing. The mean values of T m associated with the 100 and 300 mg doses were 9.2 ± 1.2 on day 1 and 10.5 ± 0.7 h on day 17; those after the 300 mg doses were 10.5 ± 1.4 and 12.2 ± 1.9 h, respectively. The cumulative urinary recovery of unchanged drug averaged 5.3% of the administered dose. Trovafloxacin renal clearance was 0.43 ± 0.09 L/h. The free fraction of the drug in plasma was 23.8 ± 6.1 %. The renal clearance, half-life and unbound fraction did not change over the course of 2 weeks of multiple dosing. Steady-state serum concentrations were attained by the third daily dose, with approximately 1.3-fold accumulation. Both doses of trovafloxacin were well tolerated, and no significant changes in any laboratory safety parameters were detected. This study shows that the pharmacokinetics of trovafloxacin are linear and stationary and that steady-state serum concentrations above the MICs for most susceptible pathogens attained. Introduction Trovafloxacin, 7-(3-azabicyclo[3,1,0]hexyl)-naphthyridone (CP-99,219), is a new synthetic fluoroquinolone antibiotic agent. It has shown a number of favourable characteristics in preclinical in-vitro tests and in-vivo animal tests. In broth susceptibility studies, trovafloxacin demonstrates a broad spectrum of in-vitro activity against Gram-positive and Gram-negative bacteria and can be differentiated from ciprofloxacin, ofloxacin and other marketed fluoroquinolones by its greater potency against many clinically significant Gram-positive organisms, most notably streptococci such as Streptococcus pneumoniae (Eliopoulos et al., 1993; Gooding and Johns, 1993; Gootz et al., 1994; Neu & Chin, 1994). Trovafloxacin administered orally was able to control systemic infections with Gram-positive and Gram-negative organisms in mice; it is appreciably more potent than temafloxacin, ciprofloxacin and ofloxacin in /96/ $12.00/0 "96 The British Society for Antimicrobial Chemotherapy

2 956 R. Teng et al. protecting mice against lethal infections with S. pneumoniae and Streptococcus pyogenes (Girard, Bighty & Gootz, 1993). In addition to its excellent in-vitro activity and in-vivo efficacy, previous animal pharmacokinetic studies showed that trovafloxacin was rapidly and well absorbed, with oral bioavailability of 60-85%, and was well tolerated in rats, dogs and monkeys (Teng et al., 1993; Girard et al., 1993). A single-dose pharmacokinetic study in healthy male subjects showed that trovafloxacin was rapidly absorbed and well tolerated at doses of 300 mg or below (Teng et al., 1995a). The long 7*1,2 (10 h) in humans suggests the possibility of once-daily dosing. The present study was designed to evaluate the pharmacokinetics and safety of trovafloxacin following multiple oral dosing to healthy male subjects in a double-blind, placebo-controlled trial. Preliminary results from this study have been presented previously (Teng et al., 19956). Subjects Methods Twenty healthy male volunteers (aged years, mean 31 and weighing kg, mean 74.9) were enrolled in the study. Volunteers were evaluated for general good health as determined by medical history and physical examination, electrocardiogram, blood chemistry profiles, complete urinalysis and haematology studies. Subjects were excluded from the study if they had a history of drug or alcohol abuse or were not within 10% of ideal body weight for age, height and frame as established in the 1983 Metropolitan Life Insurance Height and Weight Tables. Subjects did not receive any prescription or over-the-counter medication for at least 2 weeks, or any investigational drugs for at least 4 weeks prior to participation in the study. Subjects were confined to the clinical study unit under continuous medical or paramedical observation from 12 h before the first dose until 72 h after the last dose of drug. The study protocol was reviewed and approved by the Institutional Review Board (Medical and Technical Research Associates, Boston, MA). Each subject provided written informed consent before entering the study. Study design In this double-blind, placebo-controlled trial, trovafloxacin was administered orally to healthy male volunteers at either 100 or 300 mg. Each subject received a total of 15 doses of trovafloxacin or placebo. A single dose was administered on day 1 followed by once-daily dosing on days 4 through 17. Each dosing group consisted of ten subjects, with eight randomized to receive active drug and two to receive placebo. No subject was allowed to participate in more than one dosing group. Trovafloxacin was supplied as the mesylate salt, and formulated as 100 mg tablets. Placebo and trovafloxacin tablets were identical in appearance. Trovafloxacin or placebo tablets were administered in the morning following an overnight fast of at least 8 h duration, and at least 2 h prior to ingestion of breakfast. Tolerability All subjects were under close, continuous observation in the study unit throughout the studies. Blood pressure, pulse rate and oral temperature were recorded daily just before

3 Phannacokinetics and safety of trovafloxacin 957 and 1 h after dosing, and at the same times on non-dosing days until discharged from the clinical research unit. Electrocardiograms were repeated 1 h after dosing on days 7 and 17. The haematological tests and blood chemistry profiles performed during screening were repeated just before administration of the drug on days 1, 7, 10, 18 and following collection of the last serum sample on day 20. Urine crystal examinations were performed on urine samples collected just before the morning dose and during the 0-2, 2-4, 4-8, 8-12, 12-24, and h post-dose urine collections on days 1 and 17. In addition, subjects answered written open-ended questions about drug effects approximately 4 h after dosing on days 1, 4, 6, 10, and 17. At the end of the study, subjects were asked to indicate whether they thought they had received placebo or active drug and to explain the basis for their answer. Sample collection Blood samples for determination of trovafloxacin content were collected in evacuated tubes, containing no anticoagulants or preservatives, before dosing and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 18, 24, 36, 48, 60 and 72 h post-dose on days 1 and 17. Blood samples were also obtained just before dosing on days 6, 10 and 14. Whole blood samples were allowed to clot for 45 min at room temperature and then spun in a refrigerated centrifuge to separate clot from serum. The harvested serum samples were immediately frozen at 20 C until analysis. Additionally, blood samples used to assess plasma protein binding were collected in heparinized tubes just before dosing on days 1 and 17. Plasma was prepared from each sample for subsequent assay. Urine samples were obtained from all subjects before dosing and at 0-2, 2-4, 4-8, 8-12, 12-24, and h after the dosing on days 1 and 17. At the end of each collection interval, the total volume for the interval was measured and after thoroughly mixing, a 10-mL aliquot from each collection period was frozen at 80 C until analysis. Subjects were instructed to drink 240 ml of water approximately 2 h after dosing to help ensure adequate urine collection over the 2-4 h collection interval. Analysis of trovafloxacin in serum and urine The concentrations of trovafloxacin in serum and urine were determined by high performance liquid chromatography (HPLC) with UV detection, as reported previously (Teng et al., 1993). Briefly, following solid-phase extraction, chromatographic separation was accomplished using a C 8 column and a phosphate mobile phase. Trovafloxacin and the internal standard (a methyl derivative of trovafloxacin) were detected by ultraviolet absorbance at 275 nm. The calibration curves were linear over a concentration range of 0.1 to 20.0 mg/l (R 2 = ). The average recoveries were over 70% for both compounds. The intra-day and inter-day coefficients of variation in both urine and serum were generally less than 5%. Plasma protein binding The plasma protein binding of trovafloxacin was determined by equilibrium dialysis. Plasma samples (1.0 ml) obtained just prior to drug administration on days 1 and 17 were spiked with [ l4 C]trovafloxacin (47.7 /ici/mg, 99% radiochemical purity). Additionally, unlabelled trovafloxacin was added to the day 1 plasma samples resulting

4 958 R. Teng et al. in final trovafloxacin concentrations that were comparable to the mean predose serum concentrations on day 17. The spiked samples were dialyzed against equal volumes of 0.1 M sodium phosphate buffer (ph = 7.4) for 6 h at 37 C using a single layer of Spectra/Por2 molecular porous membrane (m.w. cutoff of 12,000-14,000) in dialysis cell blocks. At the end of dialysis, aliquots from the plasma and the buffer sides were counted in 18 ml of scintillation cocktail using a liquid scintillation analyzer. Each plasma sample evaluated was dialyzed in duplicate, with plasma and post-dialysis buffer samples being counted in triplicate. The percentage of trovafloxacin free in plasma was estimated with adjustment for osmotically induced volume shifts across the membrane (Boudinot & Jusko, 1984). Pharmacokinetic analysis Pharmacokinetic parameters were calculated by standard noncompartmental methods (Gibaldi & Perrier, 1982). The terminal phase elimination rate constant (Az) was estimated using linear regression of the natural logarithm of the trovafloxacin concentrations in serum as function of time over the terminal log-linear phase. The half-life (T ]/2 ) was calculated from the equation T l/2 = Ln(2)/Az. The area under the concentration-time curve (AUC) was calculated by the linear trapezoidal rule. The AUC for day 1 was extrapolated to infinity with addition of the term of Ct/Xz, where Ct represents the concentration of the last sample with quantifiable concentration. The maximum serum concentration (C^,) was obtained directly from the serum concentration data, with T^ defined as the time of the first occurrence of C^. Geometric means and standard deviations for CM, and AUCo- m are presented. Renal clearance (C/ r ) was calculated as the ratio of the amount of trovafloxacin excreted in urine (X u ) divided by the AUC over the dosing interval, i.e., X^JAUCo-24- The percentage of drug excreted in urine (F c ) was calculated by dividing the amount of trovafloxacin excreted in urine through 72 h after a single dose on day 1 or the amount excreted over the 24 h dosing interval on day 17 by the dose. The extent of accumulation was calculated as the ratio of (AUCo^Wi? to (AUCO-MWI- The projected mean serum concentrations resulting from daily dosing were generated from the day 1 serum concentrations/pharmacokinetic data using the principle of superposition. Results The mean (±S.D.) serum trovafloxacin concentrations for the 100 and 300 mg dosing groups are depicted in Figure 1. A dose-dependent increase in trovafloxacin serum concentrations was observed when the dose increased from 100 mg to 300 mg on either day 1 and day 17. Mean trough serum levels in subjects receiving 100 mg were 0.2, 0.2, 0.2 and 0.2 mg/ml on days 6, 10, 14 and 17, respectively; those in subjects given 300 mg were 0.5, 0.6, 0.7 and 0.7 mg/ml, respectively. Visual inspection of the predose trovafloxacin concentrations on days 6, 10, 14 and 17 indicated that steady-state at both dose levels had been attained by the 3rd daily dose. Using the superposition principle, the projected serum concentrations following 14 consecutive daily doses of either 100 or 300 mg are comparable to observed values (Figures 2 and 3). Peak serum concentrations of trovafloxacin were attained approximately 1 h after dosing for the two groups on days 1 and 17 (Table). Mean (±S.D.) C,, values for the 100 and 300 mg doses

5 Phannacokioetics and safety of frovafloxacin Time (h) Figure 1. Mean serum concentrations of trovafloxacin in healthy male volunteers following oral administration of a single dose of either 100 ( ) or 300 (A) mg and daily doses of either 100 (O) or 300 (A) mg. were 1.0 ± 0.3 and 2.9 ± 0.4mg/L, respectively. Following daily dosing for 14 days, the mean C^ (day 17) were 1.1 ±0.2 mg/l for the 100 mg group and 3.3 ± 0.5 mg/l for the 300 mg group. C, increased dose-dependently. The group mean AUCo^, of trovafloxacin increased predictably relative to the estimates at 100 mg when 300 mg dose was administered. The AUCo-24 after the single dose was 9.4 ± 1.5 mg.h/l in the 100 mg group and 26.2 ±4.5 mg.h/l in the 300 mg group; it increased to 11.8 ± 1.8 and 34.6 ± 6.5 mg.h/l, respectively, after 14 consecutive daily dosing. The mean extents of accumulation for the 100 and 300 mg dosing groups were 1.26 and 1.32, respectively. The mean (±S.D.) T xa estimates associated with the 100 mg doses were 9.2 ± 1.2 on day 1 and 10.5 ± 0.7 h on day 17; those after the 300 mg doses were 10.5 ± 1.4 and 12.2 ± 1.9 h, respectively. The T [l2 appeared to be independent of the dose and time Time (day) Figure 2. Trovafloxacin concentrations in serum predicted by superposition ( ) and observed (#) during repeated oral doses (100 mg).

6 960 R. Teng et al Time (day) Figure 3. Trovafloxacin concentrations in serum predicted by superposition (- repeated oral doses (300 mg). ) and observed ( ) during Mean concentrations of trovafloxacin in urine collected 0-2 h after the 100 mg dose were 4.0 mg/l on day 1 and 4.4 mg/l on day 17; concentrations at h after dosing were 2.0 mg/l on day 1 and 2.1 mg/l on day 17 (Figure 4). After the 300 mg dose, urinary trovafloxacin concentrations at 0-2 and h, respectively, were 17.9 and 4.1 mg/l on day 1 and 18.0 at 0-2 on day 17 (Figure 5). On day 1, the percentages of the administered doses recovered in urine were 5.3 ± 0.6% and 5.1 ± 1.6% at the 100 and 300 mg doses, respectively. Most of the drug excreted in urine was recovered within 24 h after dosing. On day 17, 5.5% of the administered dose was recovered in urine for the 100 mg dose, respectively. There was no appreciable difference in the percentages recovered at the 100 mg dose level on any of the 2 days. The mean Cl, for trovafloxacin after the 100 mg doses was 0.44 ± 0.08 and 0.47 ± 0.11 L/h for day 1 and day 17, respectively; those following the 300 mg doses were 0.44 ± 0.08 and Table. Pharmacokinetic parameters (mean ± S.D.) for trovafloxacin following oral administration at single and multiple doses of 100 and 300 mg to healthy male volunteers Pharmacokinetic parameters C«, (mg/l) ' max AUC^24 (mg.h/l) AUCV % (mg.h/l) a, (L/h) f. (%) /" (%) 7", 2 (h) day 1 («= 8) 1.0 ± ± ± ± ± ± ± ± 1.2 Include all subjects in dose groups. '12-24 h urine samples were lost. 'Excluded the day 17 data. 100 day (n = ± ± ± Trovafloxacin 17 8) day (n = dose (mg) ) 2.9 ± ± ± ± ± ± ± ± 1.4 day 17 (n- = 6) 3.3 ± ± ± ± ±0.7" 28.3 ± ±1.9 Mean«1.1 ± ± ± 1.1' 23.8 ± ± 1.9

7 Pharmacokinetics and safety of trovafloxacin Time (h) Figure 4. Mean urinary concentrations of trovafloxacin determined in healthy male volunteers following oral administration of single ( ) and multiple ( ) doses of 100 mg ml/min, respectively. The renal clearance of trovafloxacin was apparently constant regardless of study dose and day. Slightly lower Cl, values observed at the 300 mg dose on day 1 was due to the loss of h urine samples in 5/6 subjects. The mean unbound fraction (/ ) in the predose plasma samples was 20.3% on day 1 and 22.0% on day 17 at the 100 mg dose level; the corresponding estimates after the 300 mg doses were 25.6% and 28.3%, respectively. Following oral administration of 100 and 300 mg single and multiple doses, trovafloxacin was well tolerated. There were no clinically significant changes in any clinical chemistry or hematological parameters evaluated. No drug-related adverse experiences were reported at the dose of 100 mg daily for 2 weeks. At the 300 mg daily dose, eight subjects experienced mild lightheadedness lasting less than 3 h, four subjects experienced headache, three subjects experienced drowsiness, one subject experienced ocular pain and one subject experienced pruritus and rash that resulted in Time fh) Figure 5. Mean urinary concentrations of trovafloxacin determined in healthy male volunteers following oral administration of single ( ) and multiple ( ) doses of 300 mg. *No sample collected.

8 962 R. Teng et al. discontinuation of treatment. Two subjects received placebo experienced dizziness and mild diarrhoea. One subject in the 100 mg dosing group showed an increase in neutrophils. No crystalluria was observed in this study. Discussion Consistent with the finding in the previous single dose study, the drug was well tolerated at the 100 and 300 mg dose levels, and peak serum levels of trovafloxacin were dose proportional (Teng et al., I995a,b). The mean CM, values (mean ± S.D.) after the single dose were 1.0 ± 0.3 and 2.9 ± 0.4 mg/l for the 100 and 300 mg doses, respectively; those after 14-day consecutive daily dosing (day 17) were 1.1 ± 0.2 and mg/l, respectively. Trovafloxacin was rapidly absorbed and reached Cm, approximately 1 h after dosing. Following daily oral doses of either 100 or 300 mg of trovafloxacin, steady-state serum concentrations were attained by the third daily dosing, with trough serum concentrations of 0,2 and 0.6 mg/l, respectively. The mean daily accumulation factors of were consistent with those of a drug with a mean terminal phase elimination half-life of approximately 10 h. The anticipated mean serum concentrations over 14 consecutive days of dosing of either 100 or 300 mg were consistent with the observed mean values, indicating that the pharmacokinetics of trovafloxacin were linear and stationary throughout the multiple dosing regimens. Approximately 5% of the dose given was recovered in urine as unchanged drug. Most of the drug excreted in urine was recovered within the 24 h after dosing. Trovafloxacin concentrations in urine 0-2 h after the 100 and 300 mg doses were approximately 4 and 18 mg/l, levels many fold higher than the MICs for most of organisms responsible for urinary tract infections. At h after administration of the 100 mg dose, concentrations in urine were 2 mg/l, which is still much higher than the MIC levels for those pathogens. The high urine concentrations of unchanged drug were maintained over a long period and represented an important pharmacokinetic characteristic of trovafloxacin for the treatment of urinary tract infections. The mean renal clearance observed in this study was at least 15-fold less than those for other fluoroquinolones, and about 5% of the administered dose was excreted into the urine, in contrast to 40-90% for other fluoroquinolones (Fitton, 1992). The low renal clearance for trovafloxacin may be attributable, at least in part, to its plasma protein binding (76%), which is higher than those reported for other fluoroquinolones (10-35%). The mean Cl, values observed in the study ranged from L/h, suggesting that repetitive daily dosing did not affect renal clearance appreciably at either dose level. Since ca. 24% of the total drug was bound to plasma proteins, the renal clearance of free drug was much smaller than the mean glomerular filtration rate, i.e., these Cl, values were lower than the mean predicted renal filtration clearance values of 1.7 L/h (/ u xgfr, where GFR was assumed to be 7.2 L/h and/ u is the mean unbound fraction). This indicated that net reabsorption would take place in the kidneys. In conclusion, the unique pharmacokinetic properties of trovafloxacin, especially the longer T h2 and greater systemic exposure, combined with the improved antibacterial spectrum may allow for once-daily dosing in humans for most indications including infections of the upper and lower respiratory tract, skin or related soft tissue and urinary tract. Clinical trials are in progress to confirm the expected clinical utility of trovafloxacin.

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