Repeated oral dose tolerance in dogs treated concomitantly with ciclosporin and oclacitinib for three weeks.

BACKGROUND: Ciclosporin and oclacitinib are immunomodulators approved for the treatment of canine atopic dermatitis. The administration of a short course of prednisolone at the beginning of ciclosporin therapy hastens the efficacy of this drug; oclacitinib has a rapid antipruritic effect similar to that of prednisolone.
OBJECTIVES: To evaluate the oral tolerance of oclacitinib and ciclosporin given concurrently for three weeks. ANIMALS: Two groups of eight beagles.
METHODS: Dogs were randomized to receive oclacitinib alone (0.4-0.6 mg/kg twice daily for 14 days then once daily for seven days) or in combination with ciclosporin (5 mg/kg once daily) for three weeks. They were examined every day and adverse events were recorded. Blood samples were collected during the acclimatization phase, weekly during treatment and at the end of the study for haematology, clinical chemistry and coagulation evaluation.
RESULTS: There were no abnormal clinical observations following treatment with oclacitinib given alone or concomitantly with ciclosporin, with the exception of diarrhoea in two dogs receiving both drugs. Three dogs from each group experienced transient inappetence; three dogs treated with oclacitinib had mild weight loss. Clinical pathology parameters remained within the reference range for beagle dogs at that facility. CONCLUSIONS AND CLINICAL IMPORTANCE: The concomitant administration of ciclosporin and oclacitinib for three weeks to beagles was well tolerated and was not associated with an increase in the number of adverse events or laboratory abnormalities beyond those associated with oclacitinib given alone.

Introduction

Ciclosporin is a cyclic polypeptide with reversible immunosuppressive properties that targets, via its inhibition of calcineurin, T‐lymphocytes and other cells involved in allergic and immunological responses.1, 2, 3 Ciclosporin (Atopica, Novartis Animal Health; Basel, Switzerland) has been used also for treatment of canine atopic dermatitis (AD) and for other canine skin diseases such as perianal fistulae and sebaceous adenitis.3 A systematic review of clinical trials enrolling dogs with AD reported the relatively slow onset of effect of ciclosporin, with skin lesion and pruritus scores abating by 30–52% and 27–34% after four weeks of treatment, respectively.4 To provide a faster relief of the clinical signs of AD, the concomitant administration of oral glucocorticoids at the onset of treatment with ciclosporin has been proposed.5 A randomized controlled trial has validated this concept, establishing that the addition of prednisolone at 1 mg/kg once daily for one week, then every other day for two weeks, markedly increased the magnitude of benefit of ciclosporin in the first month of treatment compared to ciclosporin given alone.6

Oclacitinib (Apoquel, Zoetis; Florham Park, NJ, USA) is a novel janus kinase (JAK1)‐predominant inhibitor that prevents cell signalling following the binding of proallergic, proinflammatory and pruritogenic cytokines to their respective receptors.7 Oclacitinib has been reported as being rapidly effective in reducing pruritus and skin lesions in dogs with allergic dermatitis8 and with AD.9 The speed of pruritus relief with oclacitinib is parallel to that of prednisolone, with visible improvement in itch manifestations noted within the first day of administration of both drugs.10 When tested against ciclosporin in a randomized controlled trial, oclacitinib provided a faster reduction in pruritus, with a similar effect in improving skin lesions over time.11

Given the comparable anti‐allergic effect of prednisolone and oclacitinib,10 and the clinical benefit of adding prednisolone in the first three weeks of ciclosporin administration,6 the question arises whether the concomitant administration of oclacitinib during the first weeks of ciclosporin treatment would be safe. If proven to be well‐tolerated, using both drugs concurrently during the first month of ciclosporin therapy may be beneficial to dogs with AD.

The objective of this study was to evaluate the oral tolerance and safety of oclacitinib and ciclosporin given simultaneously once daily for three weeks to beagle dogs.

Materials and methods

Study design

This study was designed as a non‐Good Laboratory Practice, nonterminal, randomized, open, parallel experiment involving two groups of eight dogs. In the first group (OC group), dogs were treated with oclacitinib (Apoquel, Zoetis) concomitantly with ciclosporin (Atopica, Novartis), whereas the second group of dogs received oclacitinib alone (O group). Swiss national animal welfare legislation was followed and local ethical approval was obtained prior to starting the study.

Animals and management

All study dogs were beagles (eight males, eight females; all intact), aged between 11 months and 4 years and weighing between 9 and 13 kg at enrolment. After acclimatization, dogs were housed in the same group and gender pairs except during the time of drug administration when they were housed individually for up to 5 h per day to facilitate the recording of individual daily feed consumption and to conduct post‐treatment clinical assessments. The dogs were fed commercial dog food once daily in relation to their daily body weight whereas water was provided ad libitum. On completion of the study, all dogs were returned to their normal housing facilities. Dogs were considered suitable for inclusion in the study if, following a physical examination and clinical pathology assessment (haematology, clinical chemistry and coagulation panels), they were considered healthy. They had not received any anti‐inflammatory product in the preceding 2 months.

Treatment administration

Dogs were randomly allocated by computer to the OC or O groups according to their gender and body weight to maintain an effective pairing of four males and four females of comparable weight range in each group.

Day 0 was defined as the first day of dosing. Treatment was administered orally (after feeding for the morning dose) at dosages approved for each drug using the most recently recorded body weight. In the OC and O groups, dogs received oclacitinib, between 0.4 and 0.6 mg/kg twice daily for 14 days, then every morning for 7 d. Ciclosporin was given to dogs from the OC group at 5 mg/kg once in the morning. Following oral dosing, each dog was administered 5–10 mL of water orally by syringe and the oropharynx was examined to confirm that the tablet or capsule had been swallowed.

Observations

A complete physical examination was performed by a veterinarian during the acclimatization and at the end of the treatment period (Day 21). Physical examination included the general appearance (behaviour, body weight and hydration), integument and mucous membranes (colour and vascular filling time), heart and lung auscultation (sounds and rhythm), body temperature, oral cavity, eyes, nares, ears, central nervous system (equilibrium, coordination, muscular use and reflexes), glands and lymph nodes.

During the treatment period, each dog was examined approximately 3 h after each morning dosing. These clinical observations included a subjective monitoring of the dog's general health status, integument, nervous, musculoskeletal, ocular, gastrointestinal and cardiovascular systems, as well as an assessment of the animal's behaviour. Dogs were weighed, pre‐feeding, twice weekly throughout the treatment phase of the study.

Adverse events

Adverse events (AE), were considered to be any observations that were unfavourable or unintended, and which occurred after the use of test medications, whether or not they were considered related to the tested drugs. The investigators recorded the AE duration, type (i.e. clinical sign), severity (serious or not serious), outcome (complete recovery, recovery with sequelae, death or other), action taken (concomitant medication, withdrawal or continuation of the dog on the study or test medicine administration) and causality assessment (probable, possible, unlikely, unclassifiable/not assessable).

Clinical pathology

Blood samples were collected from every dog during the acclimatization phase (Day −6 to Day 0), weekly during treatment (days 3, 10 and 17) and at the end of the study (Day 21). Overnight fasting blood samples were collected into ethylenediaminetetraacetic acid (EDTA) for haematology, serum gel tubes for clinical chemistry and sodium citrate for coagulation parameters. Blood samples were analysed in the clinical pathology laboratory of the test facility for the parameters detailed in Table S1. Reference ranges for clinical pathology parameters had been established recently from this colony of beagle dogs.

Statistical analyses

The daily observed food consumption values were transformed as weekly averages for each individual. Body weight, food consumption and clinical pathology (haematology, clinical chemistry and coagulation) parameters were reported as descriptive statistics (mean, median and standard deviation) and analysed using repeated‐measures analysis of covariance (RMANCOVA) using statistics software (SAS v9.2.2, SAS; Cary, NC, USA). The average of two or more pretreatment values was included in the models as a covariate. The fixed factors in the models were treatment group and sex, whereas the repeated factor was time (i.e. study day). The two factor interactions (treatment × sex, treatment × time and sex × time) and the three factor interaction (treatment × sex × time) were also included. The following SAS procedures were used: “MIXED” for analysis with the covariance structures “AR(1)” and “ARH(1)” for data collected on equal intervals, spatial power covariance structure “SP(POW)” for data collected on unequal intervals, and “CS” and “CSH” for data collected at both equal and unequal intervals. We chose to report results from the model with the smallest Akaike's information criterion (i.e. those of best quality for a given set of data); for all pairwise comparisons, the chosen threshold for significance was P = 0.05.

Results

Animals and treatments

All treatments were successfully administered, with dogs in both groups receiving one or both drugs according to the study design except for one deviation: one dog from the OC group received a 3% higher dosage of oclacitinib (0.62 mg/kg) for nine consecutive doses (days 4–8) due to weight loss.

There were no deaths, withdrawals or abnormal clinical observations made following treatment with oclacitinib given alone or concomitantly with ciclosporin, with the exception of diarrhoea observed in two dogs in the OC group. One dog exhibited diarrhoea within 3 h after both morning and evening doses on Day 2; the other had a single episode of diarrhoea within 3 h of the morning dose on Day 17.

Food consumption and body weight

Food consumption was not significantly different between groups. Three dogs in each treatment group demonstrated a moderate transient inappetence (Figure S1). Their appetite fluctuated throughout the study with dogs eating at least 64% (Group OC) or 75% (Group O) of the food offered each day. Altogether there were no significant differences between treatment groups in regards to body weight. Mild weight loss was observed during the acclimatization and dosing phases in one dog from the OC group and in three dogs from the O group; two of these three dogs concurrently showed inappetence whereas the others entirely consumed their daily food.

Haematology

There were no significant differences in haematological parameters between groups. Any changes in values observed were considered not clinically relevant (Table S2).

Clinical chemistry

During the pre‐treatment acclimatization period (Day −6 to Day 0), one male dog had increased creatine kinase (851 U/L; reference range: 85–450 U/L) and lactate dehydrogenase activity levels (315 U/L; reference range: 30–253 U/L). These were not associated with abnormal clinical signs and were not considered relevant; this dog was subsequently randomized to the O group.

Only two parameters were significantly different when compared between the dogs of both treatment groups:

Alanine aminotransferase activity levels were significantly lower in males from the OC (mean: 24 U/L, reference range: 15–50 U/L) than those from the O group (mean: 36 U/L) (P = 0.05).

Blood urea nitrogen was significantly higher in dogs from the OC (mean: 4.8 mmol/L; reference range: 3.1–7.0 mmol/L) than those from the O group (mean: 4.3 mmol/L) (P = 0.03).

In spite of these significant differences, individual values from all parameters always remained within the reference range for beagle dogs held at this facility (Table S3).

Otherwise, and apart from the minor changes reported above, there were no significant differences in clinical chemistry values between the OC and O treatment groups.

Coagulation

There were no statistically significant differences for either prothrombin time, activated partial thromboplastin times or fibrinogen between dogs from the OC and O groups. All values always remained within the reference range for beagle dogs from this facility (Table S4).

Discussion

In this study, we established that the concomitant administration of ciclosporin and oclacitinib, when given according to their manufacturer's instructions for three consecutive weeks, was very well tolerated in beagle dogs. This study was not blinded and whilst observations were made by staff unaware of treatment allocation, we cannot exclude that bias might have occurred. Furthermore, this study involved small numbers (eight per treatment group) of a single breed of dogs (beagle); it will only be when this combination of drugs is used widely in the field, under a variety of conditions and in a range of dog breeds and ages, that the full safety of concomitant treatment with oclacitinib and ciclosporin will be known.

With the exception of one dog, all study subjects received both drugs within approved dosage ranges. The last dog, treated with both drugs, had a body weight that decreased below the minimum weight intended for the 5.4 mg oclacitinib tablet. As a result he received 0.62 mg/kg of the drug for nine consecutive doses before being changed to a 3.6 mg oclacitinib tablet (a 3.3% increase on the maximum approved dosage range). In this dog, however, no adverse events or significant changes in clinical pathology were observed at any time during the study.

Both ciclosporin and oclacitinib have been reported to cause minor adverse events when given as monotherapy to dogs with AD.4, 12 The administration of either of these drugs is associated with transient gastrointestinal disturbances including vomiting, diarrhoea or inappetance/anorexia.4, 11, 12 In this study, soft stools were observed on Day 2 in one dog and on Day 17 in another dog; both receiving the two drugs concurrently.

Whilst a decrease in food intake was observed in dogs from both groups during this study, it is unclear if the decrease in food ingestion was due to reduced appetite or to a confounding management factor, as this was observed only during weekends when dogs were fed by different personnel. As similar transient reductions in food intake also had been observed before treatment commenced, this phenomenon was felt to be unlikely due to treatment.

Some dogs in both treatment groups showed mild body weight loss during the study, although the differences in body weights between groups were not significant. These small decreases in body weight could, in part or in toto, be due to the decreased food intake discussed above. Apart from this transient weight loss, there were no other reports of adverse events in this study.

In a randomized controlled trial comparing the efficacy and safety of ciclosporin and oclacitinib given alone to dogs with AD, occasional dogs treated with either drug exhibited mild changes in haematology or clinical chemistry parameters, even though the mean values for both treatment groups remained in the reference ranges.11 The lack of consistent changes in clinical pathology parameters after the administration of ciclosporin for treatment of AD has also been documented in a compilation of previously published trials.13 Similarly, relevant changes in clinical pathology values were not found in dogs treated with oclacitinib in the long term.12 In the present study, evaluated haematology and coagulation parameters remained in the reference range established for beagles kept at this research facility; significant differences in values between groups were not observed. Minor changes in two chemistry parameters (alanine aminotransferase and blood urea nitrogen) were found to be significantly different between the two treatment groups, but as values were still in the reference range for beagles and were not associated with any visible adverse events, they were not deemed to be clinically relevant.

This study demonstrated that the concomitant administration of ciclosporin and oclacitinib for three weeks to beagle dogs was very well tolerated and did not increase the frequency or severity of abnormal clinical signs or laboratory abnormalities beyond the rare changes associated with the administration of oclacitinib alone. Whether or not these findings can be extrapolated to dogs of other breeds and/or to dogs with AD is not known, but there are no reasons suggesting the opposite. Furthermore, as drug blood levels were not monitored in this trial, any interaction between the metabolisms of ciclosporin and oclacitinib would not be detected; the eventuality of such interaction should be evaluated in pharmacological studies. Nevertheless, oclacitinib appears to be a suitable alternative to prednisolone for combination therapy during the induction of treatment with ciclosporin in dogs with AD.

Figure S1. Mean percentage of total food offered that was consumed in both groups over time. Bar represents the standard deviation.

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Table S1. Evaluated clinical pathology parameters.

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Table S2. Haematology parameters.

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Table S3. Clinical chemistry parameters.

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Table S4. Coagulation parameters.

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