Pharmacokinetics
Safety, Tolerability and Pharmacokinetic Profile of Single and Multiple Oral Doses of Arterolane (RBx11160) Maleate in Healthy Subjects
The Journal of Clinical Pharmacology 54(4) 386–393 © 2013, The American College of Clinical Pharmacology DOI: 10.1002/jcph.232
Nilanjan Saha, MD, DM1, Joerg J. Moehrle, PhD, MBA2, Anita Zutshi, MPharm1, Pradeep Sharma, MVSc3, Pawandeep Kaur, MD1, and Sunil S. Iyer, MPharm, PhD3
Abstract Arterolane (RBx11160, OZ277) maleate is a rapidly acting synthetic trioxolane anti‐malarial. This randomized, placebo controlled study was a phase I study to evaluate the clinical safety and tolerability as well as pharmacokinetics (PKs) of arterolane maleate including food effect. Eight single rising oral doses of arterolane (25, 50, 100, 150, 200, 300, 400, 600 mg), food effect under fed and fasting conditions at 100 mg dose and four multiple oral dose regimens (25, 50, 100, 200 mg) were administered once daily for 7 days in 64 healthy young males (Caucasian). A randomized, placebo‐ controlled study was also conducted in healthy elderly males and females (Caucasian) to investigate PKs, safety and tolerability of single oral dose (100 mg) of arterolane. All doses were well tolerated after oral administration. The initial peak of arterolane was apparent at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Thereafter, plasma arterolane concentration declined with a geometric mean t1/2 of approximately 2–4 hours. The PKs of arterolane appeared to be time‐invariant after repeated once‐daily dosing. The incidence of adverse events was similar for placebo and active treatments. Arterolane had similar PKs and tolerability in elderly and younger subjects and between elderly males and females.
Keywords arterolane maleate, OZ277, RBx11160, single rising dose, multiple rising dose, pharmacokinetics, safety
The chemotherapy of malaria has benefited greatly from the semi‐synthetic artemisinins. Artemisinin combination therapies (ACTs) are recommended as the first‐line treatment of uncomplicated malaria caused by Plasmodium falciparum. Artemisinin in these combinations produce a very rapid therapeutic response (reduction of the parasite biomass and resolution of symptoms).1,2 However, being plant‐derived, there is potential of mismatch in demand and supply and this led to the search of synthetic antimalarial compounds.3 A collaborative drug discovery project to identify antimalarials with a pharmacophoric peroxide bond in a unique 1,2,4‐trioxane hetrocycle resulted in the identification of arterolane. Arterolane, in comparison to semisynthetic artemisinins, exhibited structural simplicity, scalable synthesis, superior anti‐malarial activity and improved biopharmaceutical profile.4 Arterolane demonstrated an IC50 of 1.0 0.1 and 0.91 0.1 ng/ml (mean SEM) against K1 chloroquine resistant and NF54 chloroquine sensitive strains. After a single oral dose of 3 mg/kg, arterolane was more active than comparator drugs artesunate, artemether, mefloquine in murine (Plasmodium berghei) model of malaria.5 Arterolane demonstrated adequate safety margin between effective dose (ED) in animal malaria model and toxic doses evaluated in animals. Safety pharmaco-
logical studies indicated that arterolane was safe and did not produce any clinically significant effect on behavioral and cardiovascular parameters. Preliminary studies on the mechanism of antimalarial activity of arterolane illustrate that arterolane localizes to the parasite cytosol and food vacuoles and is dependent on Fe2þ for its activity.5,6 In addition, arterolane possibly generate C‐centered free radicals leading to alkylation of
1 Department of Medical Affairs and Clinical Research, Ranbaxy Research Laboratories, Plot # 77B, Sector 18, Gurgaon 122015, Haryana, India 2 Medicines for Malaria Venture‐MMV, International Center Cointrin, Block G, 3rd Floor, 20, Route de Pré‐Bois CH‐1215, Geneva 15, Switzerland 3 Clinical Pharmacology and Pharmacokinetics, Plot No GP‐5, Sector‐ 18, HSIDC, Old Delhi Gurgaon, Road, Gurgaon 122015, Haryana, India
Grant sponsor: Medicines for Malaria Venture (MMV) Geneva, Switzerland. Submitted for publication 19 July 2013; accepted 12 November 2013. Corresponding Author: Dr. Nilanjan Saha, Ranbaxy Laboratories Ltd., Plot # 90B, Sector 32, Gurgaon 122 001, Haryana, India. Email: [email protected]
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parasitic proteins. However, arterolane and artesunate act antagonistically against falciparum in vitro indicating difference in the mechanism of action of the two compounds.5–7 Also, Uhlemann et al demonstrated that the difference between the concentrations of drug needed to kill parasites as shown in measurements of IC50 values that are approximately 1.5 nM for RBx11160 and the potency of inhibition of PfATP6 suggests that there may be different mechanisms of action for RBx11160 and artemisinins.8 Pharmacokinetic (PK) studies indicated that arterolane is highly protein bound and has a high clearance (CL) with a large volume of distribution (Vd) in experimental animals. The elimination half‐life (t1/2) varied from 1 to 3 hours across the species. The bioavailability of the compound was found to be less at lower doses as compared to higher doses in animals.8 The two studies reported in this article were the phase I studies, where the safety, tolerability and PKs (including food effect) of arterolane maleate was investigated in healthy male (Caucasian) subjects and single dose study conducted in elderly male and female (Caucasian) subjects, where the effect of age and sex on the PKs and tolerance was determined. The efficacy and safety of fixed dose combination (FDC) of arterolane maleate þ Piperaquine phosphate has already been established in uncomplicated falciparum malaria and has been approved for marketing in India since 2012.
Materials and Methods Study Design Healthy adult subjects. This was a single center, Phase I, randomized, placebo‐controlled study, consisting of three parts (A, B, and C). Part A of the study (single rising dose escalation) was a four‐period, four‐way crossover ascending dose study in which single rising oral doses of arterolane maleate were investigated. Part B (food effect) was an open label two‐period crossover study in which the effect of food on the PK profile of single oral doses of arterolane was investigated. In Part C (multiple rising dose escalation), multiple oral doses were studied where once daily dose was administered for a period of 7 days. Both Part A and Part C of the study were conducted in a double blind manner. Elderly subjects. A single oral dose of arterolane was investigated in a double‐blind, randomized, placebo‐ controlled study. Subjects Healthy Caucasian adult males aged 18–45 years with a body mass index (BMI) between 19 and 28 kg/m2 were enrolled in parts A, B, and C of the trial. In elderly study healthy Caucasian elderly males and females aged 65
387 years, with a BMI between 19 and 28 kg/m2 were enrolled. Study subjects were negative for hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (anti‐HCV) and human immunodeficiency virus (HIV) I and II tests at screening, negative for drugs of abuse and alcohol at screening and admission, non‐smokers for at least 3 months. The subjects were enrolled after their consent to participate in the trial according to the ethical principles stated in the Declaration of Helsinki, the requirements of ICH‐GCP, the European Union Directive and local regulation. The study was conducted at Guy’s Drug Research Unit, Quintiles, United Kingdom (UK). The plasma analysis for arterolane quantitation was performed at the Bioanalytical Unit, Quintiles Limited (now Aptuit) at Edinburg. The study protocol and related documents of the adult study was approved by an Independent Ethics Committee (Brent Medical Ethics Committee) whereas for the elderly study, approval was obtained from the Guy’s Research Ethics Committee. Prior authorization for the conduct of Clinical studies was obtained from Medicines and Healthcare Products Regulatory Agency, United Kingdom in May 2004. Methodology Adult study. In Part A of the study, single rising oral doses of arterolane were investigated in a four‐period, four‐way crossover ascending dose study that comprised of two cohorts (Cohorts 1 and 2) of eight subjects each, enrolled in an alternating panel design. Two subjects in each cohort were randomized to receive placebo, and the remaining six subjects were to receive arterolane on the morning of Day 1 of each period, separated by an appropriate interval from the next period, to allow for thorough review and valuation of interim safety and PK data prior to proceeding to the next higher dose level. The dose range used in this study was decided after taking into account results from pre‐clinical safety studies. The no observed adverse effect levels (NOAELs) determined from 28‐day pre‐clinical toxicology studies were 30 and 60 mg/kg in dogs and rats, respectively. The initial single dose of 25 mg (in a 70 kg man) used in this study was 1/56 of the NOAEL in the 28‐day dog study and 1/112 of the NOAEL in the 28‐day rat study. Based on the species that showed the lowest NOAEL and the exposure comparison in repeated dose toxicity studies up to a ED90 dose exposure (60 mg/kg/day in rats, 25 times the exposure compared to the ED90 exposure dose), the human equivalent dose (HED) was considered to be 9.7 mg/kg/day. Accordingly, the maximum recommended starting dose in humans was considered to be 1.0 mg/kg. Six dose levels were investigated with a starting dose of 25 mg of arterolane. Planned doses of arterolane and placebo for Cohort 1 (Periods 3 and 4) and Cohort 2
388 (Periods 2, 3 and 4), were revised following review of draft safety data after administration of initial doses of arterolane and placebo. Actual doses of arterolane and placebo administered ranged between 25 and 300 mg in Cohorts 1 and 2. An additional cohort of eight subjects (Cohort A) was to receive arterolane at doses of 400, 600, and 800 mg. Actual doses of arterolane and placebo administered in Cohort A were 400 and 600 mg, following a three‐period three‐way crossover design. In Part B, the effect of food on the PK profile of single oral doses of arterolane, was investigated in eight young healthy males using an open‐label two‐period crossover design. Subjects received a single oral dose of 100 mg arterolane, under fed and fasted conditions, with doses being separated by a washout period of at least 7 days. Four subjects were randomized to each sequence group (fasted/fed or fed/fasted). The dose of arterolane administered was decided upon following review of safety and PK data from Part A of the study. In part C repeated oral doses of arterolane or placebo were administered to sequential groups of eight young healthy male subjects. Within each group of eight subjects, two were randomized to receive placebo and remaining six to receive arterolane. Repeated once daily oral dose of 25, 50, 100, and 200 mg were administered for 7 days. Elderly study. Twenty‐eight elderly subjects (14 males and 14 females) were enrolled in the study, where 12 males and 12 females were randomized to receive 100 mg of arterolane, and the remaining two males and two females to receive placebo in the morning of Day 1 of the treatment period. Dose Administration Doses were administered with 240 mL water after an overnight fast. Subjects were dosed whilst semi‐supine and were not permitted to lie supine for 2 hours post‐dose, except for study procedures or if clinically indicated. Safety Monitoring The safety and the general tolerability of the drug were judged based on adverse events (AEs), their time of onset, severity, duration, and possible relationship to the study drug. Safety evaluation also included physical examination, vital signs, electrocardiogram (ECG), audiometry results (Part C only), lead II ECG monitoring (Part A only), and clinical laboratory tests. Audiometry assessments and determination of brainstem auditory evoked potentials (BAEP) were performed at screening, and also in Part C at discharge in adult study. Audiometric assessments comprised the following: vestibular, middle ear and cochlear function, otoscopy and pure tone audiometry. BAEP were recorded using a Nicolet Compass Medium Averager according to standard clinical procedures.
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Pharmacokinetic Analysis Plasma arterolane was analyzed using protein precipitation followed by high‐performance liquid chromatography (HPLC) analysis on a tandem mass spectrometer. The objectives of this PK analysis was to characterize the single‐dose (during conduct of Part A, to assess dose proportionality) and multiple‐dose (during conduct of Part C to assess drug accumulation) PK of arterolane following once‐daily ascending oral doses, and to investigate the PK of arterolane following a single oral dose of 100 mg arterolane to healthy young male subjects under fed and fasting conditions (during conduct of Part B, to assess food effect). For elderly male and female subjects the effect of age and sex on the PK of arterolane was assessed. After each dose (including placebo; Part A), during each period (Part B) and Part C blood samples were taken as follows: pre‐dose and at 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 8.0, 10.0, 12.0, 16.0, and 24.0 hours post‐dose. The six subjects initially receiving 25 and 50 mg in Part A did not have samples taken at 4.5 and 5.5 hours post‐dose. In Part C, blood samples were also taken on Days 1 and 7 and additional pre‐dose blood samples were taken on Days 3, 4, 5, and 6. Blood samples for the PK analysis in the elderly study were also collected at 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 8.0, 10.0, 12.0, 16.0, and 24.0 hours post‐dose. The primary PK endpoints for assessing dose proportionality after a single dose of arterolane were AUC0–1 and Cmax for Parts A and after multiple dosing were Cmax, AUC0–t on Day 1 and AUC0–t on Day 7 of Part C. A non‐linear power model was used to assess dose proportionality. The primary PK endpoints for assessing the effect of food were AUC0–1, tmax and Cmax. The analysis of equivalence (to investigate whether a statistically relevant difference exists in the PK of arterolane when administered under fasted or fed conditions), was based on the log‐ transformed PK parameters (AUC and Cmax) using an analysis of variance (ANOVA) model with sequence, state (fed/fasted) and treatment period as fixed effects and subject as a random effect. The point estimates and 90% confidence intervals (CIs) for the ratio (fed/fasted) were calculated from the ANOVA model. The linearity with respect to time was characterized after repeated dosing by the observed accumulation ratio [RO], where RO ¼ AUC0–t (Day 7)/AUC0–t (Day 1), and linearity ratio [RLIN], where RLIN ¼ AUC0–t (Day 7)/ AUC0–1 (Day 1). In addition, the time to attain steady‐ state plasma levels was assessed visually from plots of individual and mean pre‐dose concentrations against sampling day. The primary PK parameters to assess the effects of age and sex on the PK of arterolane were AUC0–1 and Cmax.
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To assess the effect of sex on the PK of arterolane, a model was fitted to the log‐transformed AUC0–1 and Cmax data and included a fixed‐effect term for sex. The ratio of female/male geometric means was estimated and 95% confidence intervals for these ratios were calculated. Statistics Randomization was performed by Quintiles South Africa, using the SAS1 Version 8.02 computer software package. The SAS1 for Windows 95/NT (Version 8.02, SAS Institute, Cary, NC) software package was used for all statistical analyses. The non‐compartmental PK variables were calculated from plasma concentrations, using WinNonlin Pro (Version 4.0.1). Data were summarized descriptively by sex as well as by treatment groups (cohort) and dose level. Generally for continuous variables, descriptive statistics are presented where applicable (including number of subjects [N], arithmetic mean [mean], standard deviation [SD], coefficient of variation [CV%], median, minimum, and maximum).
Results In Part A, eight subjects each in Cohort 1 received placebo and arterolane at doses of 25, 100, and 200 mg, according a four‐period four‐way crossover design, where six subjects were randomized to arterolane and two subjects were randomized to placebo during each period of the study. In Cohort 2, placebo and arterolane were administered at doses of 50, 150, and 300 mg, following the same design as in Cohort 1. Subject 012 (Cohort 2) only received one dose each of 50 and 150 mg of arterolane, before being discontinued from the study. Eight subjects in Cohort A received placebo and arterolane at doses of 400 and 600 mg, following a three‐period, three‐way crossover design, where six subjects were randomized to receive arterolane, and two subjects to receive placebo during each period of the study. Subject 021 (Cohort A) received only one 400 mg dose of arterolane before being discontinued from the study. In Part B of the study, eight subjects received a single oral dose of 100 mg of arterolane, under fed and fasted conditions, separated by a wash‐out period of seven days. During Part C of the study subjects in Cohorts 4, 5, 6, and 7, respectively, received 25, 50, 100, or 200 mg arterolane or placebo once daily for a period of 7 days. Six subjects in each cohort were randomized to receive placebo and the remaining two to receive arterolane. In Cohort 7, one patient was discontinued from the study after receiving only two doses of placebo. In elderly study 28 healthy elderly subjects (14 males and 14 females) were randomized and completed the study according to the clinical study protocol.
389 Pharmacokinetic Results Plasma concentration–time profiles Part A Time to Cmax (tmax) was, on average (median) 5.0– 5.3 hours post‐dose. Double peaks were observed in the plasma arterolane concentration time profiles at each dose level. The initial peak was apparent at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Thereafter, plasma arterolane concentration declined with a geometric mean t1/2 of approximately 2– 4 hours. The exponents of the power model were 1.4 and 1.3 for AUC0–1 and Cmax respectively, indicating a greater than dose proportional relationship. Furthermore, there was statistically significant evidence for a non‐dose proportional increase in AUC0–1 and Cmax because the 95% CI around the mean exponent did not include unity. For a doubling of dose, systemic exposure to arterolane would be expected to increase 2.4‐ to 2.8‐fold. The increase in AUC0–1 and Cmax was greater and disproportionate to the increase in dose especially at the lower doses. At therapeutic doses, the increase from 100 to 200 mg in five subjects leads to a mean increase of 2.9 and 2.6 for AUC0–1 and Cmax, respectively (Figure 1). Part B The time to Cmax (tmax) was, on average (median) 4.5 hours post‐dose with and without concomitant ingestion of a high‐fat meal. There was little or no effect of food on the rate of systemic availability of arterolane. Irrespective of whether arterolane was administered under fed/fasted conditions, plasma arterolane concentrations declined with a geometric mean t1/2 of approximately 3 hours (Table 1). The extent of systemic availability (AUC0–1 and Cmax) of arterolane after oral administration of 100 mg arterolane with a high‐fat breakfast appeared to be greater than that under fasted conditions. The geometric mean ratios (fed/ fasted) for AUC0–1 and Cmax were 1.3 and 1.1,
Figure 1. Mean plasma arterolane concentration–time profiles following single oral administration of 25–600 mg arterolane to healthy young male subjects: Part A.
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Table 1. Geometric Mean Pharmacokinetic Parameters Following Administration of Single Oral Dose of 25, 50, 100, 150, 200, 300, 400, and 600 mg Arterolane (Part A) Under Fasting Condition Dose (mg) 25 50 100 150c 200d 300b 400 600b
Cmax (ng/mL) 5.5 13.2 44.4 61.1 116 172 186 398
tmaxa (h) 2.5 5 5 5.25 5 4.5 4.8 5
AUC0–1 (ng h/mL) b
37.7 91.1 327 601 1,089 1,526 1,512 3,211
t1/2 (hours) b
2.1 2.4 3.1 3.2 3.5 3.7 3.2 4.2
Dose Normalized AUC
Dose Normalized Cmax
1.5 1.8 3.3 4.0 5.5 5.1 3.8 5.4
0.2 0.3 0.4 0.4 0.6 0.6 0.5 0.7
a
Median. Mean of seven subjects. c Mean of two subjects. d Mean of five subjects. b
respectively and the 90% CIs were not included within the prescribed limits of 0.8–1.3. Therefore, an absence of a food effect could not be concluded. Figure 2 depicts the concentration–time profiles following single oral administration (100 mg of arterolane maleate) under fed and fasted condition. Part C Following single (Day 1) and repeated once‐daily (Day 7) dosing; the time to Cmax (tmax) was, on average (median), 4.5–5.0 hours post‐dose. Double peaks were observed in the plasma arterolane concentration–time profiles at each dose level. The initial peak was observed at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Plasma arterolane concentrations declined with a geometric mean t1/2 of approximately 3 hours (Table 2). Relationship between systemic exposure and dose. On Day 1, the estimated fold increase in AUC0–24h and Cmax for a doubling in dose was 2.9 (95% CI: 2.6, 3.2) and 2.6 (95% CI: 2.4, 2.8), respectively. On Day 7, the estimated fold increase for AUC0–24h and Cmax was 3.3 (95% CI: 2.9,
Figure 2. Mean plasma arterolane concentration–time profiles following single oral administration of 100 mg arterolane maleate to healthy young male subjects under fed and fasted conditions: Part B.
3.8) and 2.83 (95% CI: 2.5, 3.2), respectively. Therefore, for a doubling in dose, systemic exposure to arterolane would be expected to increase 2.3‐ to 3.8‐fold. Accumulation in Plasma Following repeated, once‐daily administration, systemic exposure to arterolane on Day 7 was not appreciably different to that on Day 1.9,10 The degree of accumulation of arterolane in plasma (RO) is given by the systemic exposure (AUC0–24h) after repeated once‐daily dosing (Day 7) relative to that on Day 1. On average, RO values were not appreciably different from unity (0.9–1.4), consistent with a short t1/2 relative to the dosing interval (24 hours). The linearity ratio (RLIN) was close to unity (mean values were 0.9–1.4), which is consistent with time‐ invariant PKs with the exception of the highest dose level, plasma concentrations at pre‐dose were close to or below the LOQ (limit of quantization). Pharmacokinetic Profile and Systemic Exposure in Elderly Subjects Maximum plasma concentrations were attained at 5.0 and 5.5 hours (median) post dose in elderly males and females respectively. Thereafter, plasma concentrations declined with a geometric mean t1/2 of approximately 2.7 and 3.2 hours in males and females respectively. Systemic exposure of elderly females compared to elderly males. Systemic exposure to arterolane (AUC0–1) in elderly female subjects and elderly male subjects appeared to be greater than that in elderly males. The geometric mean AUC0–1 value in females was approximately 36% greater than that in males, although this difference was not statistically significant. Mean PK parameters and ratios (females/males) with 95% CIs are summarized in Table 3. Systemic exposure of elderly males compared to young males. Systemic exposure to arterolane in elderly male subjects tended to be greater than that in young male subjects; however, but the difference was not statistically
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Table 2. Geometric Mean Pharmacokinetic Parameters of AUC0–1 and Cmax after 100 mg Arterolane Administered Under Fasted and Fed Conditions (N ¼ 8) Parameter
Fed or Fasted
AUC0–1 (ng h/mL)
Fed Fasted Fed Fasted
Cmax (ng/mL)
Geometric Mean
Geometric Mean Ratio (Fed/Fasted)
90% CI for Ratio
292 219 37.3 32.6
1.3
1.2, 1.5
1.1
1.0, 1.4
Fed/Fasted ratio with 90% CIs also presented (Part B).
Table 3. Geometric Mean PK Parameters Following First (Day 1) and seventh (Day 7) Oral Dose of 25, 50, 100, and 200 mg Arterolane (Mean of Six Subjects, Except Where Stated) (Part C) Tmaxa (hours)
Cmax (ng/mL)
AUC0–24 (ng h/mL)
AUC0–1 (ng h/mL)
t1/2 (hours)
Dose
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
25.0 50.0 100.0 200.0
4.7 10.9 32.1 79.4
3.1 10.7 30.5 90.7
4.5 4.5 4.5 4.5
4.5 5.0 4.5 5.0
25.2 70.5 242.0 563.0
17.0b 73.1 186.6 827.5
26.3c 72.2d 243.5 567.4
18.8 73.0 192.3 833.8
1.8c 2.3d 3.1 3.0
1.8 2.6 2.5 2.8
a
Median. Mean of five subjects. c Mean of four subjects. d Mean of three subjects. b
significant. Mean PK parameters and ratios (elderly males/ young males) with 95% CIs are summarized in Table 4. Safety Results There were no serious adverse events (SAEs) in any of the studies. The incidence of AEs was similar for placebo and active treatment and between different cohorts. There were no clinically significant findings in vital signs, ECGs, physical examination, audiometries and BAEP. Adverse Events (Healthy Adult Study) Most AEs reported in healthy adults were related to nervous system (headaches, postural dizziness, and somnolence), and gastrointestinal system (nausea, vomiting, diarrhea, dyspepsia) AEs. The AEs related to
gastrointestinal system were all reported in subjects who received the 600 mg dose of arterolane maleate. The AEs were not limited to either the fed or fasted period of dosing. There were also reports of skin and subcutaneous disorders (dermatitis, exfoliative dermatitis of the hands, a non‐specific rash and a skin reaction at the cannula dressing site). Except for the cannula site reaction (not related), all skin‐related AEs were thought to be possibly related to study medication. There were no relevant clinical abnormalities reported by audiometry findings and BAEP. No clinical significant changes from baseline were observed in the median values of laboratory parameters except the mentionable difference in the total bilirubin levels and median change from baseline for triglycerides was notably large. Triglyceride values were generally higher at screening, admission on
Table 4. Elderly Female/Male and Elderly Male/Young Male Mean Ratios and 90% Confidence Intervals of PK Parameters AUC0–1 and Cmax After Oral Administration of Arterolane Maleate 100 mg Parameter AUC0–1 (ng h/mL) Cmax (ng/mL) AUC0–1 (ng h/mL) Cmax (ng/mL)
Male or Female Subject
Geometric Mean
Geometric Mean Ratio (Females/Males)
EF/EM EF/EM EM/YM EM/YM
457/337 51.5/42.5 337/259 42.5/37
1.4 1.2 1.3 1.2
Note: EF, elderly female; EM, elderly male, YM, young male.
90% CI for Ratio 0.9, 0.9, 1.0, 0.9,
2.0 1.7 1.8 1.5
392 Day 1 and follow‐up than on Day 2, and were ascribed to the change in subjects’ diet whilst confined to the clinical research unit (CRU). Adverse Events (Elderly Study) Ten (35.7%) of the 28 subjects presented with a total of 12 AEs, all of which were reported as possibly related to the study medication. The majority of AEs reported were related to nervous system (headaches, sciatica, somnolence, paresthesia) and gastrointestinal system (nausea, diarrhea). All AEs were considered to be mild in severity. Overall the incidence of AEs was similar for male (25.0%) and female (33.3%) subjects. No clinically significant changes from baseline were observed in the median values of any of the laboratory parameters.
Discussion In this single and multiple dose study arterolane was administered to healthy subjects to investigate the safety, tolerability, food effect, and PKs of arterolane. The PK analysis indicated that the systemic exposure to arterolane increased greater than dose proportionately after single (25–600 mg) and repeated once daily (25– 200 mg) oral administration with moderate to low inter‐ subject variability but low intra‐subject variability. The bioavailability of arterolane increased with increases in dose which is consistent with the preclinical PK finding. This disproportionate increase in exposure of arterolane as compared to increases in dose of the drug administered may be due to saturation of the enzymes/transporter systems at higher doses or saturation of first pass metabolism which perhaps leads to higher bioavailability. The possible determinants of variability seen in PK estimates include body weight, age, sex, type of dosing (single or multiple‐dosing), and food intake. The PK study of other artemisinins (oral artemether) in man shows considerable inter‐individual variation in the PK of both the parent and the metabolite.9 The PKs of artesunate and DHA (dihydroartemisinin) have been studied in a single randomized three phase cross over model. It demonstrated that oral DHA was rapidly absorbed from gastrointestinal tract with marked interindividual variation. The PKs of DHA following 2 and 4 mg/kg body weight were similar and linearity in its PKs was observed.11 It was demonstrated that artemisinin exhibits time‐ dependant PKs in healthy subjects as well as malaria patients during repeated oral administration putatively caused by an auto‐induction of drug metabolism in man. The lower drug levels towards the end of a treatment period may in some individuals become insufficient for radical parasite CL.11 In contrast, the PKs of arterolane appeared to be time‐invariant after repeated once‐daily dosing. In vitro metabolism studies of arterolane with
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mouse, rat, dog, monkey and human microsomes showed that oxidation of the adamantane moiety is the major metabolic pathway in all the species. Metabolism in rat and human cryopreserved hepatocytes showed that the compound is more stable in human than in rat hepatocytes. CYP3A4 is the primary human CYP450 enzyme responsible for the microsomal degradation of arterolane. Plasma protein binding was similar (95%) in rat, mouse, dog, and human. Arterolane PK profile also demonstrated secondary peaks in the study after the maximum concentration (Cmax) in the plasma was attained. These may be related to regional absorption in the gut, enterohepatic cycling or variable gastric emptying. Following single oral dose of 100 mg arterolane under fed and fasted conditions, the geometric mean ratios (fed/ fasted) for AUC0–1 and Cmax were 1.33 and 1.14 respectively and the 90% CIs were not within the prescribed limits of 0.80–1.25. Therefore food increased the systemic availability of arterolane was concluded. Plasma arterolane concentration declined with a geometric mean t1/2 of approximately 3 hours irrespective of drug being administered with or without food. The systemic exposure to arterolane was similar in healthy young and elderly male subjects but was increased with healthy elderly female subjects. Overall single and multiple doses of arterolane were safe and well tolerated, in the dose range and subject population studied. Preclinical safety pharmacology studies indicated that arterolane maleate is a safe compound and did not produce any unwanted effect on behavioral parameters or cardiovascular system. At a relatively high oral dose (150 mg/kg) to the putative therapeutic dose, mild respiratory stimulation was observed and also single dose studies indicated higher dose levels are likely to cause central nervous system (CNS) related signs in both rats and mice. It showed no evidence of primary dermal irritation in rabbits or any photo toxicity reactions with in vitro cytotoxicity assay with Balb/c3T3 Cells. Arterolane maleate was found to be an “eye irritant” in primary eye irritation study conducted in rabbit preclinical models suggests a substantial safety margin between an ED for malaria and the toxic dose. In the present studies the subjects experienced nervous system related (headache, postural dizziness, and somnolence) and gastrointestinal AEs (nausea, vomiting, abdominal pain, and dyspepsia). No dose‐related changes in clinical laboratory, vital sign, or ECG parameters were observed. Adverse events reported throughout the study were mild to moderate in intensity, and either related to the nervous system (headaches, postural dizziness, and somnolence) or gastrointestinal tract (nausea, vomiting, diarrhea, dyspepsia). Adverse event rates were generally similar for placebo and active treatment, between different cohorts as well as between male and female subjects. None of the subjects developed any serious adverse event or
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required discontinuation of study drug as a result of drug‐ related adverse event. There were no clinically significant findings of note in any of the laboratory variables or any other safety parameters reported. Systemic exposure to arterolane maleate increases greater than dose proportionately after single (25– 600 mg) and repeated once‐daily (25–200 mg) oral administration in healthy volunteers. Cmax is achieved within 5.00–5.25 hours, thereafter plasma arterolane concentrations declines with a mean t1/2 of 2–4 hours. Between‐ subject (interindividual) variability in the extent of systemic exposure (Cmax and AUC0–8h) to arterolane in healthy young subjects was moderate to low, with coefficients of variation of 16–48%. The PKs of arterolane is time‐ invariant after repeated once‐daily dosing. Food marginally increased the systemic availability of the PKs of arterolane; however, sex and age have no apparent effect on it. Arterolane, as a single agent has been evaluated in patients suffering from uncomplicated falciparum malaria at doses of 50, 100 and 200 mg.12 A FDC of arterolane maleate and piperaquine phosphate had been evaluated in a multi‐center study in malaria endemic regions and undergoing registration process with regulatory authorities of malaria endemic countries. The FDC is already registered in India for the treatment of uncomplicated malaria. Acknowledgements Authors thank the volunteers and their caregivers for their participation in the study. We also wish to acknowledge Dr. Jyoti Paliwal (Troikaa Pharmaceuticals), Dr. Anirudh Gautam (Dr. Reddy’s Lab), Dr. Timothy Mant (Quintiles Drug Research Unit, Guy’s Hospital) for their contribution towards the study.
References 1. Report of the 2008 Artemisinin Enterprise Conference; October 8– 10 York UK accessed at http://www.york.ac.uk/org/cnap/artemisiaproject/pdfs/AEconference‐report‐web.pdf 2. WHO facts on ACTs (artemisinin‐based combination therapies); January 2006 update accessed at http://www.searo.who.int/LinkFiles/Drug_Policy_RBMInfosheet_9.pdf 3. Van Noorden R. Demand for malaria drug soars. Nature. 2010;466:672–673. 4. Vennerstrome JL, Arbe‐Barnes S, Brun R, et al. Identification of an antimalarial synthetic trioxolane drug development candidate. Nature. 2004;430:900–904. 5. Snyder C, Chollet J, Santo‐Tomas J, et al. In vitro and in vivo interaction of synthetic peroxide RBx11160 (OZ277) with piperaquine in Plasmodium models. Exp Parasitol. 2007;115:296–300. 6. Artemisinin consortium, Medicines for Malaria Venture, Annual Report 2006. URL: http://www.dfid.gov.uk/r4d/PDF/Outputs/ MMV/annual_report_2006.pdf (accessed on Nov 26, 2011). 7. Gautam A, Ahmed T, Sharma P, et al. Pharmacokinetics and pharmacodynamics of arterolane maleate following multiple oral doses in adult patients with P. falciparum malaria. J Clin Pharmacol. 2011;51:1519–1528. 8. Uhlemann AC, Wittlin S, Matile H, et al. Mechanism of antimalarial action of the synthetic trioxolane RBX11160 (OZ277). Antimicrob Agents Chemother. 2007;51:667–672. 9. Colburn WA. Estimating the accumulation of drugs. J Pharm Sci. 1983;72:833–834. 10. Gilbaldi M, Perrier D. Pharmacokinetics. 2nd edition. New York: Marcel Dekker, 1982. pp 117–119. 11. Bangchang KN, Karbwang J, Thomas CG, et al. Pharmacokinetics of artemether after oral administration to healthy Thai males and patients with acute, uncomplicated falciparum malaria Br J Clin Pharmacol. 1994;37:249–253. 12. Valecha N, Looareesuwan S, Martensson A, et al. Arterolane, a new synthetic trioxolane for treatment of uncomplicated Plasmodium falciparum malaria: a phase II, multicenter, randomized, dose‐ finding clinical trial. Clin Infect Dis. 2010;51: 684–691.
Funding
Supporting Information
Medicines for Malaria Venture (MMV) Geneva, Switzerland for providing financial support and co‐sponsoring the project.
Additional supporting information may be found in the online version of this article at the publisher’s web‐site.
Safety, Tolerability and Pharmacokinetic Profile of Single and Multiple Oral Doses of Arterolane (RBx11160) Maleate in Healthy Subjects
The Journal of Clinical Pharmacology 54(4) 386–393 © 2013, The American College of Clinical Pharmacology DOI: 10.1002/jcph.232
Nilanjan Saha, MD, DM1, Joerg J. Moehrle, PhD, MBA2, Anita Zutshi, MPharm1, Pradeep Sharma, MVSc3, Pawandeep Kaur, MD1, and Sunil S. Iyer, MPharm, PhD3
Abstract Arterolane (RBx11160, OZ277) maleate is a rapidly acting synthetic trioxolane anti‐malarial. This randomized, placebo controlled study was a phase I study to evaluate the clinical safety and tolerability as well as pharmacokinetics (PKs) of arterolane maleate including food effect. Eight single rising oral doses of arterolane (25, 50, 100, 150, 200, 300, 400, 600 mg), food effect under fed and fasting conditions at 100 mg dose and four multiple oral dose regimens (25, 50, 100, 200 mg) were administered once daily for 7 days in 64 healthy young males (Caucasian). A randomized, placebo‐ controlled study was also conducted in healthy elderly males and females (Caucasian) to investigate PKs, safety and tolerability of single oral dose (100 mg) of arterolane. All doses were well tolerated after oral administration. The initial peak of arterolane was apparent at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Thereafter, plasma arterolane concentration declined with a geometric mean t1/2 of approximately 2–4 hours. The PKs of arterolane appeared to be time‐invariant after repeated once‐daily dosing. The incidence of adverse events was similar for placebo and active treatments. Arterolane had similar PKs and tolerability in elderly and younger subjects and between elderly males and females.
Keywords arterolane maleate, OZ277, RBx11160, single rising dose, multiple rising dose, pharmacokinetics, safety
The chemotherapy of malaria has benefited greatly from the semi‐synthetic artemisinins. Artemisinin combination therapies (ACTs) are recommended as the first‐line treatment of uncomplicated malaria caused by Plasmodium falciparum. Artemisinin in these combinations produce a very rapid therapeutic response (reduction of the parasite biomass and resolution of symptoms).1,2 However, being plant‐derived, there is potential of mismatch in demand and supply and this led to the search of synthetic antimalarial compounds.3 A collaborative drug discovery project to identify antimalarials with a pharmacophoric peroxide bond in a unique 1,2,4‐trioxane hetrocycle resulted in the identification of arterolane. Arterolane, in comparison to semisynthetic artemisinins, exhibited structural simplicity, scalable synthesis, superior anti‐malarial activity and improved biopharmaceutical profile.4 Arterolane demonstrated an IC50 of 1.0 0.1 and 0.91 0.1 ng/ml (mean SEM) against K1 chloroquine resistant and NF54 chloroquine sensitive strains. After a single oral dose of 3 mg/kg, arterolane was more active than comparator drugs artesunate, artemether, mefloquine in murine (Plasmodium berghei) model of malaria.5 Arterolane demonstrated adequate safety margin between effective dose (ED) in animal malaria model and toxic doses evaluated in animals. Safety pharmaco-
logical studies indicated that arterolane was safe and did not produce any clinically significant effect on behavioral and cardiovascular parameters. Preliminary studies on the mechanism of antimalarial activity of arterolane illustrate that arterolane localizes to the parasite cytosol and food vacuoles and is dependent on Fe2þ for its activity.5,6 In addition, arterolane possibly generate C‐centered free radicals leading to alkylation of
1 Department of Medical Affairs and Clinical Research, Ranbaxy Research Laboratories, Plot # 77B, Sector 18, Gurgaon 122015, Haryana, India 2 Medicines for Malaria Venture‐MMV, International Center Cointrin, Block G, 3rd Floor, 20, Route de Pré‐Bois CH‐1215, Geneva 15, Switzerland 3 Clinical Pharmacology and Pharmacokinetics, Plot No GP‐5, Sector‐ 18, HSIDC, Old Delhi Gurgaon, Road, Gurgaon 122015, Haryana, India
Grant sponsor: Medicines for Malaria Venture (MMV) Geneva, Switzerland. Submitted for publication 19 July 2013; accepted 12 November 2013. Corresponding Author: Dr. Nilanjan Saha, Ranbaxy Laboratories Ltd., Plot # 90B, Sector 32, Gurgaon 122 001, Haryana, India. Email: [email protected]
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parasitic proteins. However, arterolane and artesunate act antagonistically against falciparum in vitro indicating difference in the mechanism of action of the two compounds.5–7 Also, Uhlemann et al demonstrated that the difference between the concentrations of drug needed to kill parasites as shown in measurements of IC50 values that are approximately 1.5 nM for RBx11160 and the potency of inhibition of PfATP6 suggests that there may be different mechanisms of action for RBx11160 and artemisinins.8 Pharmacokinetic (PK) studies indicated that arterolane is highly protein bound and has a high clearance (CL) with a large volume of distribution (Vd) in experimental animals. The elimination half‐life (t1/2) varied from 1 to 3 hours across the species. The bioavailability of the compound was found to be less at lower doses as compared to higher doses in animals.8 The two studies reported in this article were the phase I studies, where the safety, tolerability and PKs (including food effect) of arterolane maleate was investigated in healthy male (Caucasian) subjects and single dose study conducted in elderly male and female (Caucasian) subjects, where the effect of age and sex on the PKs and tolerance was determined. The efficacy and safety of fixed dose combination (FDC) of arterolane maleate þ Piperaquine phosphate has already been established in uncomplicated falciparum malaria and has been approved for marketing in India since 2012.
Materials and Methods Study Design Healthy adult subjects. This was a single center, Phase I, randomized, placebo‐controlled study, consisting of three parts (A, B, and C). Part A of the study (single rising dose escalation) was a four‐period, four‐way crossover ascending dose study in which single rising oral doses of arterolane maleate were investigated. Part B (food effect) was an open label two‐period crossover study in which the effect of food on the PK profile of single oral doses of arterolane was investigated. In Part C (multiple rising dose escalation), multiple oral doses were studied where once daily dose was administered for a period of 7 days. Both Part A and Part C of the study were conducted in a double blind manner. Elderly subjects. A single oral dose of arterolane was investigated in a double‐blind, randomized, placebo‐ controlled study. Subjects Healthy Caucasian adult males aged 18–45 years with a body mass index (BMI) between 19 and 28 kg/m2 were enrolled in parts A, B, and C of the trial. In elderly study healthy Caucasian elderly males and females aged 65
387 years, with a BMI between 19 and 28 kg/m2 were enrolled. Study subjects were negative for hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (anti‐HCV) and human immunodeficiency virus (HIV) I and II tests at screening, negative for drugs of abuse and alcohol at screening and admission, non‐smokers for at least 3 months. The subjects were enrolled after their consent to participate in the trial according to the ethical principles stated in the Declaration of Helsinki, the requirements of ICH‐GCP, the European Union Directive and local regulation. The study was conducted at Guy’s Drug Research Unit, Quintiles, United Kingdom (UK). The plasma analysis for arterolane quantitation was performed at the Bioanalytical Unit, Quintiles Limited (now Aptuit) at Edinburg. The study protocol and related documents of the adult study was approved by an Independent Ethics Committee (Brent Medical Ethics Committee) whereas for the elderly study, approval was obtained from the Guy’s Research Ethics Committee. Prior authorization for the conduct of Clinical studies was obtained from Medicines and Healthcare Products Regulatory Agency, United Kingdom in May 2004. Methodology Adult study. In Part A of the study, single rising oral doses of arterolane were investigated in a four‐period, four‐way crossover ascending dose study that comprised of two cohorts (Cohorts 1 and 2) of eight subjects each, enrolled in an alternating panel design. Two subjects in each cohort were randomized to receive placebo, and the remaining six subjects were to receive arterolane on the morning of Day 1 of each period, separated by an appropriate interval from the next period, to allow for thorough review and valuation of interim safety and PK data prior to proceeding to the next higher dose level. The dose range used in this study was decided after taking into account results from pre‐clinical safety studies. The no observed adverse effect levels (NOAELs) determined from 28‐day pre‐clinical toxicology studies were 30 and 60 mg/kg in dogs and rats, respectively. The initial single dose of 25 mg (in a 70 kg man) used in this study was 1/56 of the NOAEL in the 28‐day dog study and 1/112 of the NOAEL in the 28‐day rat study. Based on the species that showed the lowest NOAEL and the exposure comparison in repeated dose toxicity studies up to a ED90 dose exposure (60 mg/kg/day in rats, 25 times the exposure compared to the ED90 exposure dose), the human equivalent dose (HED) was considered to be 9.7 mg/kg/day. Accordingly, the maximum recommended starting dose in humans was considered to be 1.0 mg/kg. Six dose levels were investigated with a starting dose of 25 mg of arterolane. Planned doses of arterolane and placebo for Cohort 1 (Periods 3 and 4) and Cohort 2
388 (Periods 2, 3 and 4), were revised following review of draft safety data after administration of initial doses of arterolane and placebo. Actual doses of arterolane and placebo administered ranged between 25 and 300 mg in Cohorts 1 and 2. An additional cohort of eight subjects (Cohort A) was to receive arterolane at doses of 400, 600, and 800 mg. Actual doses of arterolane and placebo administered in Cohort A were 400 and 600 mg, following a three‐period three‐way crossover design. In Part B, the effect of food on the PK profile of single oral doses of arterolane, was investigated in eight young healthy males using an open‐label two‐period crossover design. Subjects received a single oral dose of 100 mg arterolane, under fed and fasted conditions, with doses being separated by a washout period of at least 7 days. Four subjects were randomized to each sequence group (fasted/fed or fed/fasted). The dose of arterolane administered was decided upon following review of safety and PK data from Part A of the study. In part C repeated oral doses of arterolane or placebo were administered to sequential groups of eight young healthy male subjects. Within each group of eight subjects, two were randomized to receive placebo and remaining six to receive arterolane. Repeated once daily oral dose of 25, 50, 100, and 200 mg were administered for 7 days. Elderly study. Twenty‐eight elderly subjects (14 males and 14 females) were enrolled in the study, where 12 males and 12 females were randomized to receive 100 mg of arterolane, and the remaining two males and two females to receive placebo in the morning of Day 1 of the treatment period. Dose Administration Doses were administered with 240 mL water after an overnight fast. Subjects were dosed whilst semi‐supine and were not permitted to lie supine for 2 hours post‐dose, except for study procedures or if clinically indicated. Safety Monitoring The safety and the general tolerability of the drug were judged based on adverse events (AEs), their time of onset, severity, duration, and possible relationship to the study drug. Safety evaluation also included physical examination, vital signs, electrocardiogram (ECG), audiometry results (Part C only), lead II ECG monitoring (Part A only), and clinical laboratory tests. Audiometry assessments and determination of brainstem auditory evoked potentials (BAEP) were performed at screening, and also in Part C at discharge in adult study. Audiometric assessments comprised the following: vestibular, middle ear and cochlear function, otoscopy and pure tone audiometry. BAEP were recorded using a Nicolet Compass Medium Averager according to standard clinical procedures.
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Pharmacokinetic Analysis Plasma arterolane was analyzed using protein precipitation followed by high‐performance liquid chromatography (HPLC) analysis on a tandem mass spectrometer. The objectives of this PK analysis was to characterize the single‐dose (during conduct of Part A, to assess dose proportionality) and multiple‐dose (during conduct of Part C to assess drug accumulation) PK of arterolane following once‐daily ascending oral doses, and to investigate the PK of arterolane following a single oral dose of 100 mg arterolane to healthy young male subjects under fed and fasting conditions (during conduct of Part B, to assess food effect). For elderly male and female subjects the effect of age and sex on the PK of arterolane was assessed. After each dose (including placebo; Part A), during each period (Part B) and Part C blood samples were taken as follows: pre‐dose and at 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 8.0, 10.0, 12.0, 16.0, and 24.0 hours post‐dose. The six subjects initially receiving 25 and 50 mg in Part A did not have samples taken at 4.5 and 5.5 hours post‐dose. In Part C, blood samples were also taken on Days 1 and 7 and additional pre‐dose blood samples were taken on Days 3, 4, 5, and 6. Blood samples for the PK analysis in the elderly study were also collected at 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 8.0, 10.0, 12.0, 16.0, and 24.0 hours post‐dose. The primary PK endpoints for assessing dose proportionality after a single dose of arterolane were AUC0–1 and Cmax for Parts A and after multiple dosing were Cmax, AUC0–t on Day 1 and AUC0–t on Day 7 of Part C. A non‐linear power model was used to assess dose proportionality. The primary PK endpoints for assessing the effect of food were AUC0–1, tmax and Cmax. The analysis of equivalence (to investigate whether a statistically relevant difference exists in the PK of arterolane when administered under fasted or fed conditions), was based on the log‐ transformed PK parameters (AUC and Cmax) using an analysis of variance (ANOVA) model with sequence, state (fed/fasted) and treatment period as fixed effects and subject as a random effect. The point estimates and 90% confidence intervals (CIs) for the ratio (fed/fasted) were calculated from the ANOVA model. The linearity with respect to time was characterized after repeated dosing by the observed accumulation ratio [RO], where RO ¼ AUC0–t (Day 7)/AUC0–t (Day 1), and linearity ratio [RLIN], where RLIN ¼ AUC0–t (Day 7)/ AUC0–1 (Day 1). In addition, the time to attain steady‐ state plasma levels was assessed visually from plots of individual and mean pre‐dose concentrations against sampling day. The primary PK parameters to assess the effects of age and sex on the PK of arterolane were AUC0–1 and Cmax.
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To assess the effect of sex on the PK of arterolane, a model was fitted to the log‐transformed AUC0–1 and Cmax data and included a fixed‐effect term for sex. The ratio of female/male geometric means was estimated and 95% confidence intervals for these ratios were calculated. Statistics Randomization was performed by Quintiles South Africa, using the SAS1 Version 8.02 computer software package. The SAS1 for Windows 95/NT (Version 8.02, SAS Institute, Cary, NC) software package was used for all statistical analyses. The non‐compartmental PK variables were calculated from plasma concentrations, using WinNonlin Pro (Version 4.0.1). Data were summarized descriptively by sex as well as by treatment groups (cohort) and dose level. Generally for continuous variables, descriptive statistics are presented where applicable (including number of subjects [N], arithmetic mean [mean], standard deviation [SD], coefficient of variation [CV%], median, minimum, and maximum).
Results In Part A, eight subjects each in Cohort 1 received placebo and arterolane at doses of 25, 100, and 200 mg, according a four‐period four‐way crossover design, where six subjects were randomized to arterolane and two subjects were randomized to placebo during each period of the study. In Cohort 2, placebo and arterolane were administered at doses of 50, 150, and 300 mg, following the same design as in Cohort 1. Subject 012 (Cohort 2) only received one dose each of 50 and 150 mg of arterolane, before being discontinued from the study. Eight subjects in Cohort A received placebo and arterolane at doses of 400 and 600 mg, following a three‐period, three‐way crossover design, where six subjects were randomized to receive arterolane, and two subjects to receive placebo during each period of the study. Subject 021 (Cohort A) received only one 400 mg dose of arterolane before being discontinued from the study. In Part B of the study, eight subjects received a single oral dose of 100 mg of arterolane, under fed and fasted conditions, separated by a wash‐out period of seven days. During Part C of the study subjects in Cohorts 4, 5, 6, and 7, respectively, received 25, 50, 100, or 200 mg arterolane or placebo once daily for a period of 7 days. Six subjects in each cohort were randomized to receive placebo and the remaining two to receive arterolane. In Cohort 7, one patient was discontinued from the study after receiving only two doses of placebo. In elderly study 28 healthy elderly subjects (14 males and 14 females) were randomized and completed the study according to the clinical study protocol.
389 Pharmacokinetic Results Plasma concentration–time profiles Part A Time to Cmax (tmax) was, on average (median) 5.0– 5.3 hours post‐dose. Double peaks were observed in the plasma arterolane concentration time profiles at each dose level. The initial peak was apparent at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Thereafter, plasma arterolane concentration declined with a geometric mean t1/2 of approximately 2– 4 hours. The exponents of the power model were 1.4 and 1.3 for AUC0–1 and Cmax respectively, indicating a greater than dose proportional relationship. Furthermore, there was statistically significant evidence for a non‐dose proportional increase in AUC0–1 and Cmax because the 95% CI around the mean exponent did not include unity. For a doubling of dose, systemic exposure to arterolane would be expected to increase 2.4‐ to 2.8‐fold. The increase in AUC0–1 and Cmax was greater and disproportionate to the increase in dose especially at the lower doses. At therapeutic doses, the increase from 100 to 200 mg in five subjects leads to a mean increase of 2.9 and 2.6 for AUC0–1 and Cmax, respectively (Figure 1). Part B The time to Cmax (tmax) was, on average (median) 4.5 hours post‐dose with and without concomitant ingestion of a high‐fat meal. There was little or no effect of food on the rate of systemic availability of arterolane. Irrespective of whether arterolane was administered under fed/fasted conditions, plasma arterolane concentrations declined with a geometric mean t1/2 of approximately 3 hours (Table 1). The extent of systemic availability (AUC0–1 and Cmax) of arterolane after oral administration of 100 mg arterolane with a high‐fat breakfast appeared to be greater than that under fasted conditions. The geometric mean ratios (fed/ fasted) for AUC0–1 and Cmax were 1.3 and 1.1,
Figure 1. Mean plasma arterolane concentration–time profiles following single oral administration of 25–600 mg arterolane to healthy young male subjects: Part A.
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Table 1. Geometric Mean Pharmacokinetic Parameters Following Administration of Single Oral Dose of 25, 50, 100, 150, 200, 300, 400, and 600 mg Arterolane (Part A) Under Fasting Condition Dose (mg) 25 50 100 150c 200d 300b 400 600b
Cmax (ng/mL) 5.5 13.2 44.4 61.1 116 172 186 398
tmaxa (h) 2.5 5 5 5.25 5 4.5 4.8 5
AUC0–1 (ng h/mL) b
37.7 91.1 327 601 1,089 1,526 1,512 3,211
t1/2 (hours) b
2.1 2.4 3.1 3.2 3.5 3.7 3.2 4.2
Dose Normalized AUC
Dose Normalized Cmax
1.5 1.8 3.3 4.0 5.5 5.1 3.8 5.4
0.2 0.3 0.4 0.4 0.6 0.6 0.5 0.7
a
Median. Mean of seven subjects. c Mean of two subjects. d Mean of five subjects. b
respectively and the 90% CIs were not included within the prescribed limits of 0.8–1.3. Therefore, an absence of a food effect could not be concluded. Figure 2 depicts the concentration–time profiles following single oral administration (100 mg of arterolane maleate) under fed and fasted condition. Part C Following single (Day 1) and repeated once‐daily (Day 7) dosing; the time to Cmax (tmax) was, on average (median), 4.5–5.0 hours post‐dose. Double peaks were observed in the plasma arterolane concentration–time profiles at each dose level. The initial peak was observed at 2–3 hours post‐dose followed by a secondary peak at approximately 5 hours post‐dose. Plasma arterolane concentrations declined with a geometric mean t1/2 of approximately 3 hours (Table 2). Relationship between systemic exposure and dose. On Day 1, the estimated fold increase in AUC0–24h and Cmax for a doubling in dose was 2.9 (95% CI: 2.6, 3.2) and 2.6 (95% CI: 2.4, 2.8), respectively. On Day 7, the estimated fold increase for AUC0–24h and Cmax was 3.3 (95% CI: 2.9,
Figure 2. Mean plasma arterolane concentration–time profiles following single oral administration of 100 mg arterolane maleate to healthy young male subjects under fed and fasted conditions: Part B.
3.8) and 2.83 (95% CI: 2.5, 3.2), respectively. Therefore, for a doubling in dose, systemic exposure to arterolane would be expected to increase 2.3‐ to 3.8‐fold. Accumulation in Plasma Following repeated, once‐daily administration, systemic exposure to arterolane on Day 7 was not appreciably different to that on Day 1.9,10 The degree of accumulation of arterolane in plasma (RO) is given by the systemic exposure (AUC0–24h) after repeated once‐daily dosing (Day 7) relative to that on Day 1. On average, RO values were not appreciably different from unity (0.9–1.4), consistent with a short t1/2 relative to the dosing interval (24 hours). The linearity ratio (RLIN) was close to unity (mean values were 0.9–1.4), which is consistent with time‐ invariant PKs with the exception of the highest dose level, plasma concentrations at pre‐dose were close to or below the LOQ (limit of quantization). Pharmacokinetic Profile and Systemic Exposure in Elderly Subjects Maximum plasma concentrations were attained at 5.0 and 5.5 hours (median) post dose in elderly males and females respectively. Thereafter, plasma concentrations declined with a geometric mean t1/2 of approximately 2.7 and 3.2 hours in males and females respectively. Systemic exposure of elderly females compared to elderly males. Systemic exposure to arterolane (AUC0–1) in elderly female subjects and elderly male subjects appeared to be greater than that in elderly males. The geometric mean AUC0–1 value in females was approximately 36% greater than that in males, although this difference was not statistically significant. Mean PK parameters and ratios (females/males) with 95% CIs are summarized in Table 3. Systemic exposure of elderly males compared to young males. Systemic exposure to arterolane in elderly male subjects tended to be greater than that in young male subjects; however, but the difference was not statistically
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Table 2. Geometric Mean Pharmacokinetic Parameters of AUC0–1 and Cmax after 100 mg Arterolane Administered Under Fasted and Fed Conditions (N ¼ 8) Parameter
Fed or Fasted
AUC0–1 (ng h/mL)
Fed Fasted Fed Fasted
Cmax (ng/mL)
Geometric Mean
Geometric Mean Ratio (Fed/Fasted)
90% CI for Ratio
292 219 37.3 32.6
1.3
1.2, 1.5
1.1
1.0, 1.4
Fed/Fasted ratio with 90% CIs also presented (Part B).
Table 3. Geometric Mean PK Parameters Following First (Day 1) and seventh (Day 7) Oral Dose of 25, 50, 100, and 200 mg Arterolane (Mean of Six Subjects, Except Where Stated) (Part C) Tmaxa (hours)
Cmax (ng/mL)
AUC0–24 (ng h/mL)
AUC0–1 (ng h/mL)
t1/2 (hours)
Dose
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
Day 1
Day 7
25.0 50.0 100.0 200.0
4.7 10.9 32.1 79.4
3.1 10.7 30.5 90.7
4.5 4.5 4.5 4.5
4.5 5.0 4.5 5.0
25.2 70.5 242.0 563.0
17.0b 73.1 186.6 827.5
26.3c 72.2d 243.5 567.4
18.8 73.0 192.3 833.8
1.8c 2.3d 3.1 3.0
1.8 2.6 2.5 2.8
a
Median. Mean of five subjects. c Mean of four subjects. d Mean of three subjects. b
significant. Mean PK parameters and ratios (elderly males/ young males) with 95% CIs are summarized in Table 4. Safety Results There were no serious adverse events (SAEs) in any of the studies. The incidence of AEs was similar for placebo and active treatment and between different cohorts. There were no clinically significant findings in vital signs, ECGs, physical examination, audiometries and BAEP. Adverse Events (Healthy Adult Study) Most AEs reported in healthy adults were related to nervous system (headaches, postural dizziness, and somnolence), and gastrointestinal system (nausea, vomiting, diarrhea, dyspepsia) AEs. The AEs related to
gastrointestinal system were all reported in subjects who received the 600 mg dose of arterolane maleate. The AEs were not limited to either the fed or fasted period of dosing. There were also reports of skin and subcutaneous disorders (dermatitis, exfoliative dermatitis of the hands, a non‐specific rash and a skin reaction at the cannula dressing site). Except for the cannula site reaction (not related), all skin‐related AEs were thought to be possibly related to study medication. There were no relevant clinical abnormalities reported by audiometry findings and BAEP. No clinical significant changes from baseline were observed in the median values of laboratory parameters except the mentionable difference in the total bilirubin levels and median change from baseline for triglycerides was notably large. Triglyceride values were generally higher at screening, admission on
Table 4. Elderly Female/Male and Elderly Male/Young Male Mean Ratios and 90% Confidence Intervals of PK Parameters AUC0–1 and Cmax After Oral Administration of Arterolane Maleate 100 mg Parameter AUC0–1 (ng h/mL) Cmax (ng/mL) AUC0–1 (ng h/mL) Cmax (ng/mL)
Male or Female Subject
Geometric Mean
Geometric Mean Ratio (Females/Males)
EF/EM EF/EM EM/YM EM/YM
457/337 51.5/42.5 337/259 42.5/37
1.4 1.2 1.3 1.2
Note: EF, elderly female; EM, elderly male, YM, young male.
90% CI for Ratio 0.9, 0.9, 1.0, 0.9,
2.0 1.7 1.8 1.5
392 Day 1 and follow‐up than on Day 2, and were ascribed to the change in subjects’ diet whilst confined to the clinical research unit (CRU). Adverse Events (Elderly Study) Ten (35.7%) of the 28 subjects presented with a total of 12 AEs, all of which were reported as possibly related to the study medication. The majority of AEs reported were related to nervous system (headaches, sciatica, somnolence, paresthesia) and gastrointestinal system (nausea, diarrhea). All AEs were considered to be mild in severity. Overall the incidence of AEs was similar for male (25.0%) and female (33.3%) subjects. No clinically significant changes from baseline were observed in the median values of any of the laboratory parameters.
Discussion In this single and multiple dose study arterolane was administered to healthy subjects to investigate the safety, tolerability, food effect, and PKs of arterolane. The PK analysis indicated that the systemic exposure to arterolane increased greater than dose proportionately after single (25–600 mg) and repeated once daily (25– 200 mg) oral administration with moderate to low inter‐ subject variability but low intra‐subject variability. The bioavailability of arterolane increased with increases in dose which is consistent with the preclinical PK finding. This disproportionate increase in exposure of arterolane as compared to increases in dose of the drug administered may be due to saturation of the enzymes/transporter systems at higher doses or saturation of first pass metabolism which perhaps leads to higher bioavailability. The possible determinants of variability seen in PK estimates include body weight, age, sex, type of dosing (single or multiple‐dosing), and food intake. The PK study of other artemisinins (oral artemether) in man shows considerable inter‐individual variation in the PK of both the parent and the metabolite.9 The PKs of artesunate and DHA (dihydroartemisinin) have been studied in a single randomized three phase cross over model. It demonstrated that oral DHA was rapidly absorbed from gastrointestinal tract with marked interindividual variation. The PKs of DHA following 2 and 4 mg/kg body weight were similar and linearity in its PKs was observed.11 It was demonstrated that artemisinin exhibits time‐ dependant PKs in healthy subjects as well as malaria patients during repeated oral administration putatively caused by an auto‐induction of drug metabolism in man. The lower drug levels towards the end of a treatment period may in some individuals become insufficient for radical parasite CL.11 In contrast, the PKs of arterolane appeared to be time‐invariant after repeated once‐daily dosing. In vitro metabolism studies of arterolane with
The Journal of Clinical Pharmacology / Vol 54 No 4 (2014)
mouse, rat, dog, monkey and human microsomes showed that oxidation of the adamantane moiety is the major metabolic pathway in all the species. Metabolism in rat and human cryopreserved hepatocytes showed that the compound is more stable in human than in rat hepatocytes. CYP3A4 is the primary human CYP450 enzyme responsible for the microsomal degradation of arterolane. Plasma protein binding was similar (95%) in rat, mouse, dog, and human. Arterolane PK profile also demonstrated secondary peaks in the study after the maximum concentration (Cmax) in the plasma was attained. These may be related to regional absorption in the gut, enterohepatic cycling or variable gastric emptying. Following single oral dose of 100 mg arterolane under fed and fasted conditions, the geometric mean ratios (fed/ fasted) for AUC0–1 and Cmax were 1.33 and 1.14 respectively and the 90% CIs were not within the prescribed limits of 0.80–1.25. Therefore food increased the systemic availability of arterolane was concluded. Plasma arterolane concentration declined with a geometric mean t1/2 of approximately 3 hours irrespective of drug being administered with or without food. The systemic exposure to arterolane was similar in healthy young and elderly male subjects but was increased with healthy elderly female subjects. Overall single and multiple doses of arterolane were safe and well tolerated, in the dose range and subject population studied. Preclinical safety pharmacology studies indicated that arterolane maleate is a safe compound and did not produce any unwanted effect on behavioral parameters or cardiovascular system. At a relatively high oral dose (150 mg/kg) to the putative therapeutic dose, mild respiratory stimulation was observed and also single dose studies indicated higher dose levels are likely to cause central nervous system (CNS) related signs in both rats and mice. It showed no evidence of primary dermal irritation in rabbits or any photo toxicity reactions with in vitro cytotoxicity assay with Balb/c3T3 Cells. Arterolane maleate was found to be an “eye irritant” in primary eye irritation study conducted in rabbit preclinical models suggests a substantial safety margin between an ED for malaria and the toxic dose. In the present studies the subjects experienced nervous system related (headache, postural dizziness, and somnolence) and gastrointestinal AEs (nausea, vomiting, abdominal pain, and dyspepsia). No dose‐related changes in clinical laboratory, vital sign, or ECG parameters were observed. Adverse events reported throughout the study were mild to moderate in intensity, and either related to the nervous system (headaches, postural dizziness, and somnolence) or gastrointestinal tract (nausea, vomiting, diarrhea, dyspepsia). Adverse event rates were generally similar for placebo and active treatment, between different cohorts as well as between male and female subjects. None of the subjects developed any serious adverse event or
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required discontinuation of study drug as a result of drug‐ related adverse event. There were no clinically significant findings of note in any of the laboratory variables or any other safety parameters reported. Systemic exposure to arterolane maleate increases greater than dose proportionately after single (25– 600 mg) and repeated once‐daily (25–200 mg) oral administration in healthy volunteers. Cmax is achieved within 5.00–5.25 hours, thereafter plasma arterolane concentrations declines with a mean t1/2 of 2–4 hours. Between‐ subject (interindividual) variability in the extent of systemic exposure (Cmax and AUC0–8h) to arterolane in healthy young subjects was moderate to low, with coefficients of variation of 16–48%. The PKs of arterolane is time‐ invariant after repeated once‐daily dosing. Food marginally increased the systemic availability of the PKs of arterolane; however, sex and age have no apparent effect on it. Arterolane, as a single agent has been evaluated in patients suffering from uncomplicated falciparum malaria at doses of 50, 100 and 200 mg.12 A FDC of arterolane maleate and piperaquine phosphate had been evaluated in a multi‐center study in malaria endemic regions and undergoing registration process with regulatory authorities of malaria endemic countries. The FDC is already registered in India for the treatment of uncomplicated malaria. Acknowledgements Authors thank the volunteers and their caregivers for their participation in the study. We also wish to acknowledge Dr. Jyoti Paliwal (Troikaa Pharmaceuticals), Dr. Anirudh Gautam (Dr. Reddy’s Lab), Dr. Timothy Mant (Quintiles Drug Research Unit, Guy’s Hospital) for their contribution towards the study.
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Funding
Supporting Information
Medicines for Malaria Venture (MMV) Geneva, Switzerland for providing financial support and co‐sponsoring the project.
Additional supporting information may be found in the online version of this article at the publisher’s web‐site.
