Diane Larsen

Evaluation of the curative and preventive efficacy of a single oral administration of afoxolaner against cat flea Ctenocephalides felis infestations on dogs

The efficacy of orally administered afoxolaner for treatment and prevention of repeated infestations with adult Ctenocephalides felis on dogs was evaluated in two studies after administration of a beef-flavored soft chew. In each study, 32 dogs were divided randomly into four equal groups. Dogs in Groups 1 and 3 were not treated and served as controls. Dogs in Groups 2 and 4 were treated on Day 0 with a combination of chewable tablets to be as close as possible to the minimum therapeutic dose of 2.5mg/kg. All animals were infested experimentally with unfed C. felis (100 ± 5) on Days -1, 7, 14, 21, 28 and 35. Flea killing efficacy was evaluated in both studies while, efficacy against flea egg production was assessed in Study 1. Live fleas were counted at 12 (Groups 1 and 2) and 24h (Groups 3 and 4), after treatment or after weekly infestations. In Study 1, flea eggs were collected and counted at either 12 or 24h after each flea infestation on Days 7, 14, 21, 28 and 35. The results of both studies demonstrate the long lasting and rapid efficacy of afoxolaner against C. felis, when administered as a single oral dose to dogs. For flea counts conducted 24h after treatment or infestation, efficacy was 100% for all time points up to Day 36 in both studies, except for one time point (99.9% on Day 22) for Study 2. For flea counts performed 12h after treatment or infestation, efficacy was ≥ 95.2% until Day 21 in both studies. Efficacy at 12h was ≥ 93.0% on Day 35 in Study 1 and ≥ 89.7% on Day 35 in Study 2. The treated groups had significantly fewer fleas than untreated control dogs in both studies for all flea counts (p=0.003 Study 1, p=0.0006 Study 2). In Study 1, for all egg counts performed at or beyond Day 7, efficacy in egg reduction was >99% for all time points between Days 7 and 35.

Assessment of the efficacy of orally administered afoxolaner against Rhipicephalus sanguineus sensu lato.

Two studies were conducted to confirm that a single oral dose of the novel insecticide/acaricide afoxolaner is efficacious against existing infestations of Rhipicephalus sanguineus sensu lato in dogs and can control re-infestation for up to 35 days. Each study utilized 16 purpose bred adult dogs using a controlled randomized block design. One or two days prior to treatment, all dogs were infested with 50 unfed adult ticks. On Day 0 one group was treated with an oral chewable formulation of afoxolaner at a dose as close as possible to the minimum dose of 2.5mg/kg. Weekly re-infestations with 50 adult unfed ticks were repeated for five weeks. Forty-eight hours after treatment and after each re-infestation, the number of remaining live ticks on each dog was counted. Treatment with afoxolaner resulted in efficacies of 98.8-100% within 48 h on existing tick infestations, while the efficacy against new tick infestations was >95.7% over five weeks.

Evaluation of the efficacy of afoxolaner against two European dog tick species: Dermacentor reticulatus and Ixodes ricinus

The acaricidal efficacy of a novel oral formulation of afoxolaner (NEXGARD(®), Merial) against two European tick species was assessed in dogs experimentally infested with Ixodes ricinus and Dermacentor reticulatus. Three studies, each characterized by a negative controlled randomized block design, were conducted with a total of 52 beagle or mongrel dogs of both sexes. Starting 2 days before treatment, each dog was infested weekly with approximately 50 ticks. The number of live ticks was counted at 48 h post-treatment (Day 2) as well as 48 h following each infestation on Days 9, 16, 23, and 30. Afoxolaner, administered at an average dose of 2.7 mg/kg bodyweight (range 2.5-2.9 mg/kg), rapidly eliminated the pre-existing tick infestations with over 99% acaricidal efficacy and controlled the weekly re-infestations for up to 30 days post treatment with over 96% efficacy on both tick species. Afoxolaner provides excellent acaricidal efficacy against these two major European tick species using the oral route of administration.

Efficacy of oral afoxolaner for the treatment of canine generalised demodicosis

The efficacy of oral treatment with a chewable tablet containing afoxolaner 2.27% w/w (NexGard®, Merial) administered orally was assessed in eight dogs diagnosed with generalised demodicosis and compared with efficacy in eight dogs under treatment with a topical combination of imidacloprid/moxidectin (Advocate®, Bayer). Afoxolaner was administered at the recommended dose (at least 2.5 mg/kg) on Days 0, 14, 28 and 56. The topical combination of imidacloprid/moxidectin was given at the same intervals at the recommended concentration. Clinical examinations and deep skin scrapings were performed every month in order to evaluate the effect on mite numbers and the resolution of clinical signs. The percentage reductions of mite counts were 99.2%, 99.9% and 100% on Days 28, 56 and 84, respectively, in the afoxolaner-treated group, compared to 89.8%, 85.2% and 86.6% on Days 28, 56 and 84 in the imidacloprid/moxidectin-treated group. Skin condition of the dogs also improved significantly from Day 28 to Day 84 in the afoxolaner-treated group. Mite reductions were significantly higher on Days 28, 56 and 84 in the afoxolaner-treated group compared to the imidacloprid/moxidectin-treated group. The results of this study demonstrated that afoxolaner, given orally, was effective in treating dogs with generalised demodicosis within a two-month period.

Efficacy of afoxolaner against Ixodes scapularis ticks in dogs.

Efficacy of afoxolaner, a novel isoxazoline insecticide/acaricide, against Ixodes scapularis was evaluated in a laboratory study. One day prior to treatment, beagle dogs (n=16) were infested with 50 unfed wild adult ticks. Repeat infestations were performed weekly for four additional weeks. The number of live ticks remaining on each dog was determined 48 h after treatment and after each subsequent infestation. A single oral treatment with a dose approaching the minimum effective dose of afoxolaner (2.5mg/kg) eliminated the pre-existing infestations of I. scapularis ticks and controlled weekly re-infestations, with efficacy between 98% and 100% recorded until Day 23 and 94% at Day 30.

Safety evaluation of orally administered afoxolaner in 8-week-old dogs

The safety profile of afoxolaner, a new isoxazoline molecule, was evaluated following the regulatory requirements when administered six times orally in a soft chewable formulation at a dose of at least 1×, 3× or 5× the maximum exposure dose (6.3mg/kg) in 8-week-old Beagle dogs. Thirty-two healthy puppies (16 males and 16 females) were enrolled and allocated randomly to one of four treatment groups. Treatments were administered at three, one-month dose intervals (Days 0, 28 and 56) followed by three, 2-week dose intervals (Days 84, 98 and 112). The study ended at Day 126. The groups were: Group 1: non-treated control; Group 2: afoxolaner chews administered at a dosage of at least 6.3mg/kg (1×); Group 3: afoxolaner chews administered at a dosage of at least 18.9 mg/kg (3×); and Group 4: afoxolaner chews administered at a dosage of at least 31.5mg/kg (5×). All dogs were examined for general health twice a day beginning on at least Day-14. Physical examinations, and blood collections for clinical pathology analysis and afoxolaner plasma concentrations, were performed throughout the study. On Day 126, 2 weeks following the last treatment, all dogs were humanely euthanized prior to the conduction of a full necropsy with tissue collection. No afoxolaner-related changes were observed in growth, physical variables, clinical pathology variables, or tissues examined histologically. No clinically or statistically significant health abnormalities related to the administration of afoxolaner were observed. Vomiting and diarrhea were observed sporadically across all groups including the controls. The kinetics of afoxolaner plasma concentrations was linear following 6 doses of 6.3, 18.9 and 31.5mg/kg and dose proportionality was demonstrated. There were no statistical differences (p<0.05) between samples taken on Days 55 and 83 when compared to Day 27. Based upon the results of this study, afoxolaner was shown to be safe when administered repeatedly in a soft chewable formulation at up to 5× the maximum exposure dose in dogs as young as 8 weeks of age.

Evaluation of a barrier dental sealant in dogs.

A study was conducted in 40 healthy, randomly selected, client-owned, mixed and purebred dogs to assess the efficacy of a barrier dental sealant. All dogs showed evidence of dental plaque, calculus, or gingivitis. The dental sealant was applied to one side of the mouth following a professional teeth cleaning procedure and reapplied weekly for 8-weeks following the cleaning procedure. Dental parameters evaluated included plaque, calculus, gingivitis, and gingival bleeding indices. A statistically significant difference was detected between treated and untreated teeth compared with baseline values for plaque and calculus at weeks 4 and 8, gingivitis at week 4, and gingival bleeding time at week 8. A professional teeth cleaning procedure followed by a single application of the barrier dental sealant and weekly reapplication performed by a veterinarian or veterinary technician provided significant improvement in plaque and calculus indices during an 8-week period.

Assessment of the onset of action of afoxolaner against existing adult flea (Ctenocephalides felis) infestations on dogs.

The speed of kill of afoxolaner against experimental infestations by Ctenocephalides felis was evaluated after oral administration of afoxolaner in a soft chew (NEXGARD(®)) at a dose to achieve 2.5mg/kg bodyweight. Forty beagles were allocated to two treatment groups. Dogs in Treatment Group 1 were untreated controls. Dogs in Treatment Group 2 were treated on Day-0 with afoxolaner, according to their pre-treatment bodyweight. All dogs were infested with approximately 100 C. felis on Day-1. Live fleas were counted upon removal at 5 time points after treatment (i.e., 2, 4, 8, 12 and 24h after treatment). For each time point, counts were performed on 4 dogs from each of the treated and the untreated groups. Early curative flea killing efficacy was evaluated with respect to the untreated control group. The afoxolaner treated group had significantly fewer fleas than the untreated control group at 8, 12, and 24h (p<0.001). The percent efficacies of orally administered afoxolaner were 15.0%, 87.8%, 99.5%, 100.0%, and 100.0% at 2, 4, 8, 12, and 24h, respectively. In this study, afoxolaner began killing fleas by 2h after treatment with increasing efficacy at subsequent time points and had >99.5% efficacy at 8, 12, and 24h after treatment demonstrating an early onset of action.

Efficacy of afoxolaner against Dermacentor variabilis ticks in dogs.

Efficacy of afoxolaner, a novel isoxazoline insecticide/acaricide, against Dermacentor variabilis ticks was confirmed in two laboratory studies. Each study utilized a controlled, randomized block design. One day prior to treatment, beagle dogs were infested with 50 unfed adult ticks. Repeat infestations were performed weekly for four weeks. The number of live ticks remaining on each dog was determined 48 h after treatment and after each subsequent infestation. A single oral treatment with a dose approaching the minimum effective dose of afoxolaner (2.5mg/kg) eliminated the pre-existing infestations by D. variabilis ticks and controlled weekly re-infestations with 99.7-100% efficacy up to Day 23 and >97% efficacy at Day 30.

Evaluation of the efficacy of afoxolaner against Haemaphysalis longicornis on dogs

A controlled study to assess the acaricidal efficacy of afoxolaner in dogs after a single oral administration was conducted against Haemaphysalis longicornis ticks. The study was characterized by a negative controlled randomized block design and included sixteen beagle dogs of both sexes. Starting two days before treatment, each dog was infested weekly with 50 ticks over 4 weeks. The number of live ticks was determined 48 h after treatment and then 48 h after each infestation. The mean dose of afoxolaner received by dogs was 3.0mg/kg (range: 2.5-3.1mg/kg). Afoxolaner rapidly eliminated pre-existing tick infestations (100% ticks killed within 48 h of treatment) and controlled weekly re-infestations (91.9% prophylactic efficacy at Day 30).