Bioequivalence of 2 Pediatric Formulations of Fexofenadine Hydrochloride Oral Suspension

Fexofenadine hydrochloride (HCl) is a second‐generation, nonsedating, histamine H1‐receptor antagonist used to manage seasonal allergic rhinitis and chronic idiopathic urticaria. A new oral pediatric suspension of fexofenadine HCl has been developed, with the preservative potassium sorbate replacing parabens. The objective of this phase 1 single‐center, open‐label, randomized, 2‐treatment, full‐replicated, 4‐period, 2‐sequence crossover study in healthy adult volunteers was to assess the bioequivalence of 30 mg of the new oral suspension of fexofenadine HCl (test) versus 30 mg of the marketed pediatric oral suspension of fexofenadine HCl (reference). The replicate design was based on the high intra‐individual variability of fexofenadine (>30% on Cmax). The study comprised 68 randomized and treated volunteers. Plasma concentrations of fexofenadine were similar following the administration of a single dose of each formulation. Cmax, AUClast, AUC, median tmax, and mean t1/2z were similar between administrations of the same fexofenadine formulation and between formulations. A high intra‐individual variability was confirmed with both formulations. Bioequivalence of the test and reference fexofenadine HCl formulations was demonstrated as the 90% confidence intervals of the geometric least squares mean ratio for Cmax, AUClast, and AUC of fexofenadine were all within the bioequivalence range of 0.80‐1.25. There were no serious adverse events (AEs) or study discontinuations due to treatment‐emergent AEs with either fexofenadine HCl formulation. The new paraben‐free fexofenadine HCl 30‐mg oral suspension and marketed fexofenadine HCl 30‐mg pediatric oral suspension are bioequivalent under fasting conditions, with no safety concerns and a safety profile consistent with the known profile of fexofenadine.

Allergic rhinitis prevalence varies with geographic location and affects approximately up to 40% of people, with the highest incidence in children. 1 In 2017, the global reported incidence of urticaria (acute and chronic combined) was 160 million new cases annually. 2Chronic urticaria affects around 1%-2% of the population, 3 although the prevalence in children is lower, at an estimated 0.1%-0.3%. 4 Both allergic rhinitis and chronic urticaria negatively impact the quality of life and are associated with a significant healthcare burden. 1,3These conditions are commonly treated with oral antihistamines. 1,5ver-the-counter fexofenadine hydrochloride (HCl) (eg, Allegra) is a second-generation, nonsedating, histamine H1-receptor inverse agonist indicated for the relief of symptoms associated with seasonal allergic rhinitis (SAR) and chronic idiopathic urticaria (CIU). 6In some countries, fexofenadine HCl is also indicated for use in pruritus associated with skin diseases (eczema/dermatitis, pruritus cutaneous, atopic dermatitis) and for allergic rhinitis symptoms due to indoor and outdoor allergens.][20] A pooled analyses of 3 double-blind, randomized, placebo-controlled studies of fexofenadine HCl at 30 mg twice daily (bid) in children aged 6-11 years with SAR had evaluated over 10,000 treatment days. 14These analyses showed that fexofenadine HCl was effective in reducing SAR symptoms, including nasal congestion, versus placebo.The treatment-related adverse events (AEs) appeared similar among the 2 groups (fexofenadine HCl and placebo) and the most common AE was headache, which occurred at a similar incidence in the placebo and fexofenadine HCl groups.There were no signs of clinically meaningful sedation or changes in QTc interval compared with placebo. 14arious formulations of fexofenadine HCl are approved: hard capsules (60 mg), film-coated tablets (30,  60, 120, and 180 mg), gelcap tablets (180 mg), oral dispersible integrating tablets (ODT, 30 mg in USA only, 60 mg in Japan only), oral suspension (6 mg/mL), and powder for syrup (5%, in Japan only).The approved doses of fexofenadine HCl are 60 mg bid, 120 mg once daily (qd), or 180 mg qd for SAR, and 60 mg bid or 180 mg qd for CIU in patients ≥12 years; 30 mg bid for children 2-11 years with SAR, and 30 mg bid for children 2-11 years or 15 mg bid for children 6 months to <2 years with CIU.
Generally, tablets are suitable for dosing adults and children ≥12 years old.For younger pediatric patients, alternative formulations such as ODTs and oral suspensions are preferable. 21Liquid-dose formulations result in increased dose flexibility and ease of swallowing.However, it is well recognized that oral drug absorption can be affected by the formulation used, which can potentially alter exposure to the active agent, impacting efficacy and/or tolerability. 22,23Bioequivalence of drug formulations is important, 24 particularly for highly variable drugs. 25Moreover, bioavailability and bioequivalence studies are generally conducted in adult populations. 26he pharmacokinetics of fexofenadine HCl are well characterized in healthy adults [27][28][29] and in children with SAR 30,31 and CIU. 32Fexofenadine is rapidly absorbed (T max 1.4-1.5 hours) and has an absolute bioavailability of 35% after oral administration.Fexofenadine displays linear pharmacokinetics over the 20-120 mg dose range, with a small disproportionate increase in the area under the concentration-time curve (AUC) observed after a 240 mg dose. 33,34In a study of healthy male volunteers, 92% of the total dose of orally administered 14 C-fexofenadine 60 mg was recovered from the feces (80%) and urine (12%), mostly (>85%) as unchanged fexofenadine. 34The mean terminal elimination half-life ranges from 13 to 16 hours.
The fexofenadine pharmacokinetic profile is mainly dependent on the activity of the efflux transporter P-glycoprotein (P-gp).This is expressed in the mucosa of the small intestine, in the liver, kidneys, and at the blood-brain barrier. 35Fexofenadine is a sensitive P-gp substrate as demonstrated both in vitro and in vivo in MDR1 knockout mice as well as in humans with P-gp inhibitors and inducers.Other transporters such as multidrug resistance-associated proteins (MRPs) and, in particular, organic aniontransporting polypeptides (OATP1A2 and OATP2B1) are also involved in fexofenadine disposition. 35,36Absorption is reduced by grapefruit juice and orange juice, especially with concurrent intake. 37Fexofenadine is a Biopharmaceutics Drug Disposition Classification System class 3 compound.For this class, the intestinal permeability is strongly affected by both uptake and efflux transporters: these drugs require active transport to overcome their poor passive permeability.The inhibition or the induction of any intestinal transporter has the potential to cause clinically relevant changes in the disposition of poorly metabolized drugs. 38mportantly, bioequivalence has been demonstrated between a 30-mg dose of fexofenadine HCl 6 mg/mL suspension and the marketed 30-mg tablet in adults. 39oreover, a similar range of exposures to fexofenadine has been demonstrated between fexofenadine HCl in children (30 mg of fexofenadine HCl bid in children 2-<12 years old and weighing >10.5 kg, and 15 mg bid in children 6 months to <2 years and weighing ≤10.5 kg) and in adults (60 mg bid). 40Thus, it is acceptable to evaluate the bioequivalence of 2 pediatric oral suspensions of fexofenadine HCl in healthy adult volunteers and extrapolate the findings to children. 41 major challenge in pediatric treatment is the lack of suitable drug preparations specifically designed and marketed for children. 42Oral drug formulations contain excipients for several reasons, including increasing active ingredient stability, improving palatability, preservation from microbiological contamination, tonicity maintenance, and bulking up formulations containing highly potent active ingredients.However, certain excipients may cause adverse reactions 22,43 and impact drug pharmacokinetics. 22,23Furthermore, excipients that are mostly used in adult formulations may not be equally safe when used in pediatrics, even when used in very small concentrations. 44Moreover, some excipients may result in biopharmaceutical interactions with physiological systems in children by influencing the rate of absorption and elimination of concomitantly used medications. 44Thus, drug formulations suitable for use in children are required.
A new oral pediatric suspension of fexofenadine HCl has been developed in which the preservative has been changed.After parabens and benzoates, sorbates are the third largest group of antimicrobial preservatives in food and pharmaceutical industries, 45 and they have been utilized in the food industry worldwide.Sorbates are commonly used to increase the shelf life of commercial goods without affecting the organoleptic properties of food.Potassium sorbate prevents the growth of yeasts, mold, and bacteria in food products and can be used as a substitute of parabens. 46he objectives of the present phase 1 study were to assess the bioequivalence of 30 mg of a new parabenfree oral suspension of fexofenadine HCl (test) versus 30 mg of the marketed pediatric oral suspension of fexofenadine HCl (marketed fexofenadine HCl 30 mg, reference), to determine fexofenadine pharmacokinetic parameters, and to assess the safety of 30 mg of the test and reference oral suspensions of fexofenadine HCl.

Study Population
This study was conducted at Syneos Health Clinique Inc. in Quebec, Canada, in healthy adult volunteers during the COVID-19 pandemic, and all required tests and preventative measures were applied.Key inclusion criteria included males or females aged 18-55 years, with a body weight 50-100 kg (males) or 40-90 kg (females) and a body mass index of 18-30 kg/m 2 , who were considered to be healthy (based on a comprehensive clinical assessment, including vital signs, 12-lead electrocardiogram [ECG], and laboratory parameters).Females of childbearing potential were required to use acceptable contraception throughout the study and for 30 days after the last fexofenadine administration.Key exclusion criteria included a history/presence of any clinically relevant condition or disease, frequent headaches and/or migraine, a history/presence of drug or alcohol abuse, smoking ≥5 cigarettes or equivalent/day, excessive consumption of xanthine-containing beverages, any medication (including St John's Wort) within 14 days of study start or within 5 times the terminal elimination half-life (t 1/2z ) or pharmacodynamic half-life of the medication, any vaccination within the prior 28 days, and any biologics within 4 months of study start.Volunteers were not permitted to consume citrus fruits/juices with 5 days of inclusion, or to take any aluminum-/magnesium-containing antacids, any antihistaminic drugs, or any tricyclic antidepressants within 14 days of inclusion.
The study protocol, associated documents, and informed consent forms were reviewed and approved by an independent Institutional Review Board (Advarra, Columbia, MD, USA) prior to the start of any study procedures.The study was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice.All volunteers provided written, informed consent.
The test formulation was the new fexofenadine HCl 30-mg oral suspension.The reference formulation was the marketed Allegra fexofenadine HCl 30-mg pediatric oral suspension.The butylparaben and propylparaben in the reference formulation were completely substituted by potassium sorbate in the test formulation.Both formulations were manufactured by Sanofi Medley Farmacêutica Ltda (Suzano, Brazil).
Volunteers received a single dose of each formulation twice.A 4-period, 2-sequence block randomization scheme, provided by Sanofi and stratified by gender, was used to assign volunteers to each treatment (Figure 1).Volunteers were randomly assigned to 1 of 2 sequences: test/reference/test/reference or reference/test/reference/test.For each treatment period, volunteers were confined to the clinical facility from the evening of day -1 until day 3.The washout period between fexofenadine administrations was at least 7-10 days.The follow-up visit occurred 7-10 days after the last fexofenadine administration.The total study duration was up to 60 days from screening to follow-up visits.
The appropriate formulation of fexofenadine HCl (5 mL of 6 mg/mL suspension, total dose 30 mg) was administered orally under fasting conditions in the morning of day 1 of each period, after a supervised overnight fast of at least 10 hours, with 235 mL of noncarbonated water.Additional water consumption was not permitted from 1 hour before to 1 hour after administration, and no food was allowed for at least 5 hours postdose.
Plasma concentrations of fexofenadine were analyzed using a fully validated method at Syneos Health Inc. Fexofenadine and fexofenadine-d 10 used as internal standard were extracted from EDTA K2 plasma using a solid-phase extraction.The extracted samples were injected into a liquid chromatograph equipped with an Agilent ZORBAX SB-C18 (30 × 3.0 mm, 3.5 μm particule size) column at 25°C.The mobile phases were mixtures of Methanol and Milli-Q type water with ammonium acetate and acetic acid glacial (in different proportions).The mass spectrometer was an API 4000 AB Sciex equipped with a heated nebulizer in reversed phase chromatographic mode, using gradient mode with a 1000 mL/min flow rate.Injection volume was 10 μL.The m/z transitions for fexofenadine and fexofenadine-d 10 were 502.4/466.3 and 512.3/476.4,respectively.The concentration range of the calibration curve was 0.5-500 ng/mL and the lower limit of quantification was 0.5 ng/mL.Withinand between-run variability is summarized in Table S1.A total of 262 samples were selected for the incurred sample reproducibility test to demonstrate that the results obtained from study sample analysis are reproducible.The method was considered reliable and reproducible since 99.62% of repeated sample results were within the acceptance criteria of 20%.

Safety and Tolerability Assessments
Treatment-emergent AEs (TEAEs), including severity and causality, were recorded throughout the entire study.AEs were coded based on the Medical Dictionary for Regulatory Activities (version 23.1).At screening and at final follow-up, clinical laboratory parameters (biochemistry, hematology, urinalysis), vital signs, and 12-lead ECG recordings were obtained.Physical examination of the volunteers took place during screening, on day -1 of each dosing period, and at the final follow-up.

Data Analyses
Sample size calculation was based on withinparticipant standard deviations (SDs) of logtransformed maximum observed plasma concentration (C max ) and area under the plasma concentration-time curve from time zero to the last nonzero concentration (AUC last ), and extrapolated to infinity (AUC) of fexofenadine 30 and 60 mg under fasting conditions from previous internal studies.Allowing for a 10% true difference between formulation means (ratio = 0.9), the number of volunteers required to demonstrate bioequivalence between fexofenadine HCl formulations (test vs reference) with 90% power was 58 assuming a true within-participant SD of 0.300.Allowing for a dropout rate of 15%, a total of 68 volunteers was required (34 in each treatment sequence, with at least 30% of each gender).
Key pharmacokinetic parameters included C max , time to C max (t max ), t 1/2z (terminal elimination half-life), AUC last (calculated by linear-linear trapezoidal summation), and AUC extrapolated to infinity (AUC, calculated by AUC = AUC last + C last /λ, where C last is the last measurable plasma concentration and λ is the elimination rate constant [K el ]), and were estimated using WinNonLin version 8.0 (Pharsight, Mountain View, CA, USA).
Plasma concentration-time curves were plotted and descriptive statistics (mean and SD) were calculated for fexofenadine pharmacokinetic parameters.
For each treatment period, the geometric least square means (LSM) of C max , AUC last , and AUC for fexofenadine were estimated with a mixed model which included fixed terms for sequence, period, formulation, gender, and random term for volunteer within sequence-by-gender with formulation-specific between-volunteer variances and correlation between formulations.SAS version 9.3 (SAS Institute, Cary, NC, USA) was used for the analyses.Bioequivalence of the 2 fexofenadine HCl formulations was established if the 90% confidence intervals (CIs) of the geometric LSM ratio for the test versus reference were within the limits of 0.80-1.25. 24he personnel involved in the data review and analyses were blinded to the treatments throughout the study.

Disposition and Baseline Characteristics
Overall, 141 healthy volunteers were screened and 66 were excluded (52 did not meet the entry criteria, 14 were not enrolled either due to withdrawal of consent or were not selected due to a sufficient number of volunteers already being available).Of the 75 enrolled volunteers, 68 were randomized and treated.The number of volunteers receiving the first dose was 67 (test) and 68 (reference), and 65 (test) and 64 (reference) received the second dose.The first volunteer was enrolled on September 1, 2020 and the last volunteer completed the study on December 31, 2020.
Three participants discontinued from 1 study period: 1 volunteer discontinued prior to period 2 dosing (due to an AE, conjunctivitis) then completed periods 3 and 4; 2 volunteers discontinued in period 3 (1 due to a false-positive COVID-19 test result, the other for a personal reason) then completed period 4. Three participants permanently discontinued the study: 2 due to AEs (COVID-19 infection, nasopharyngitis) and 1 due to other reason (contact to a confirmed positive case of COVID-19 outside the study center).Thus, all 68 volunteers completed at least 2 treatment periods, including the test and reference formulations, and 62 completed all treatment periods.

Fexofenadine Pharmacokinetics
Fexofenadine plasma concentration-time curves are shown in Figure 1.The plasma concentration data were highly variable (Figure 2A).Plasma concentrations of fexofenadine were similar following administration of a single dose of each formulation in each period (Figure 2B).
Table 1 lists fexofenadine pharmacokinetic parameters for each administration of both formulations.The C max , AUC last , and AUC mean values were similar between administrations of the same fexofenadine formulation and between formulations.Median t max for the 2 formulations was also similar (Table 1).The mean t 1/2z of both fexofenadine formulations was similar, with a range of 11.6-12.7 hours (Table 1).
Within-volunteer SD estimates of log-transformed C max , AUC last , and AUC for test and reference fexofenadine formulations were: 0.36 and 0.35, 0.28 and 0.26, and 0.27 and 0.25, respectively (Table S2) confirming the high variability of these pharmacokinetic parameters.These estimates and the overall SD estimates were similar between formulations (Table S2).
The formulation ratios (test/reference) for C max , AUC last , and AUC of fexofenadine were 1.09, 1.08, and 1.09, respectively (Table 2).Bioequivalence of the test and reference fexofenadine HCl formulations was demonstrated because the 90% CIs of the geometric LSM ratio for C max , AUC last , and AUC of fexofenadine were all within the range 0.80-1.25 (Table 2).A sensitivity analysis using only data from all volunteers who completed all periods (n = 62) supported this primary analysis (data not shown).

Safety and Tolerability
Table S3 lists the TEAEs recorded during this study.There were no serious TEAEs or study discontinuations due to TEAEs with either fexofenadine HCl formulation.Overall, 25 TEAEs were reported in 13/68 volunteers: 11 TEAEs in 9/68 (13.2%) participants receiving the test fexofenadine HCl formulation and 14 TEAEs in 6/68 (8.8%) volunteers receiving the reference formulation.The number of TEAEs reported was similar between the test and reference formulations.The most common TEAE was headache, experience by 4 (5.9%) and 3 (4.4%)volunteers after administration of the test and reference formulations, respectively.
Of the 25 reported TEAEs, 10 (test formulation) and 11 (reference formulation) were mild.Four TEAEs were moderate in severity, that is, headache (1 event with each formulation), neck pain (reference formulation), and vomiting (reference formulation).There were no severe TEAEs.All TEAEs, except 1 (nodule, which was mild and unrelated to treatment with the reference formulation), were resolved by the end of the study.Six and 11 TEAEs were considered to be related to fexofenadine test and reference formulations, respectively.There were no TEAEs related to clinical laboratory results, vital signs, or ECGs.

Discussion
The present study demonstrates the bioequivalence of a single oral dose of 30 mg of a paraben-free oral suspension of fexofenadine HCl (test) versus a 30-mg dose of the marketed pediatric oral suspension (reference) in healthy adult volunteers, as the 90% CIs of the geometric LSM ratios for C max , AUC last , and AUC were within the limits of 0.80-1.25. 24A single dose of fexofenadine HCl, administered to healthy adults on 4 separate occasions (2 occasions/formulation), was well tolerated for both oral formulations.
Due to the transient nature of fexofenadine in plasma, it was expected that C max would be highly variable. 29,47Indeed, the present results showed that the within-volunteer SD for C max was >30%, which confirms the high variability of this parameter for fexofenadine.In addition, this finding provides justification for the robust study design, that is, a full-replicated, 4period, 2-sequence crossover study with 68 volunteers.
31,32 Although individual pharmacokinetic studies cannot be directly compared to ascertain similarities between adults and children, in a pooled analyses of data from 14 children aged 6-12 years, 21 children aged 2-5 years, and 42 children aged 6 months to 2 years, individual oral clearance estimates were 44%, 36%, and 61% lower, respectively, than in adults (n = 136). 39Several other studies evaluating the pharmacokinetics of fexofenadine HCl in children also support similar exposures in children who received ageadjusted doses to those of adults receiving a 60 mg dose of fexofenadine HCl. 30,31,48,49hen drug formulations are changed, it is important to demonstrate bioequivalence between the formulations. 24,25Typically, such studies are conducted in adults. 26For fexofenadine HCl, similar exposures have been demonstrated with tablets, ODTs, and suspensions in children and adults. 30,32,39,49Thus, while the present study was conducted in healthy adult volunteers, and not in pediatric patients, these previous studies demonstrating similar exposures to fexofenadine HCl in these patient populations, with appropriate dosing.The demonstration of bioequivalence of the 2 pediatric oral suspensions in the present study in adults can be reasonably expected to hold true in the pediatric population.
Thus, the therapeutic benefits of fexofenadine HCl are expected to be maintained in children with SAR or CIU.
5][16][17][18][19][20] The most common AE in a pooled analyses of pediatric studies in SAR was headache, at similar rates for fexofenadine HCl (5.8%) and placebo (4.3%), 14 which is not unexpected as chronic daily headaches and allergic rhinitis frequently coexist. 50In the present study, the number of AEs reported was low overall.In addition, the TEAE profile was similar between the new oral suspension of fexofenadine HCl compared with the marketed suspension.Importantly, there were no unexpected safety findings reported in this study and the AE profile was consistent with the known safety profile of fexofenadine.It has previously been shown that even with a high exposure (>7-fold higher than the recommended dose of fexofenadine HCl) in adults there were no safety issues. 29,51Furthermore, high doses of fexofenadine HCl in a pediatric population aged 6 months and above (ie, up to 2-fold higher than the recommended dose) were also demonstrated to be well tolerated with no safety issues. 16,18

Conclusions
The results of this study demonstrate that the new fexofenadine HCl 30-mg oral suspension and the marketed fexofenadine HCl 30-mg pediatric oral suspension are bioequivalent under fasting conditions.Moreover, there were no unexpected safety findings reported in this study and the AE profile was consistent with the known safety profile of fexofenadine.

Table 1 .
Summary of Fexofenadine Pharmacokinetic Parameters Following Administration of 2 Single Doses of 2 Formulations Under Fasted Conditions , area under the plasma concentration-time curve; AUC last , area under the plasma concentration-time curve from time zero to the last nonzero concentration; C max , maximum observed plasma concentration; HCl, hydrochloride; SD, standard deviation; t 1/2z , terminal elimination half-life; t last , time to last concentration above the limit of quantification; t max , time to C max .Reference formulation: marketed fexofenadine HCl 30-mg pediatric oral suspension.Test formulation: new fexofenadine HCl 30-mg oral suspension.a Except t max and t last = median (range). AUC

Table 2 .
Summary of Statistical Analyses of Fexofenadine Pharmacokinetic Parameters