Laboratory safety evaluation of lokivetmab, a canine anti-interleukin-31 monoclonal antibody, in dogs.

Lokivetmab (Cytopoint®, Zoetis) is a canine monoclonal antibody that specifically binds and neutralizes interleukin (IL)-31. Lokivetmab is approved for use in dogs for the treatment of atopic dermatitis (AD) and allergic dermatitis. The laboratory safety of lokivetmab was evaluated in 2 studies by adapting the science-based, case-by-case approach used for preclinical and early clinical safety evaluation of human biopharmaceuticals. The main objectives were to demonstrate the safety of lokivetmab in healthy laboratory Beagle dogs by using integrated clinical, morphologic, and functional evaluations. In Study 1, dogs were treated s.c. with saline or lokivetmab at 3.3 mg/kg (1X, label dose) or 10 mg/kg (3X intended dose) for 7 consecutive monthly doses, with terminal pathology and histology assessments. In Study 2, the functional immune response was demonstrated in naïve dogs using the T-cell dependent antibody response (TDAR) test with 2 different dose levels of unadjuvanted keyhole limpet hemocyanin (KLH) as the model immunogen. The primary endpoint was anti-KLH IgG antibody titer, and secondary endpoints were ex vivo IL-2 enzyme-linked immunospot (ELISpot) and peripheral blood mononuclear cell lymphoproliferation assays. Both studies included monitoring general health, periodic veterinary clinical evaluations, serial clinical pathology and toxicokinetics, and monitoring for anti-drug antibodies. In both studies, the health of dogs receiving lokivetmab was similar to controls, with no treatment-related changes uncovered. Extensive pathology evaluations of immune tissues (Study 1) revealed no lokivetmab-related morphologic changes, and in dogs treated at 10 mg/kg lokivetmab, immunization with the model antigen KLH did not impair the functional antibody or T-cell recall responses. There were no immunogenicity-related or hypersensitivity-related responses observed in either study. These studies in healthy laboratory dogs showed that lokivetmab was well-tolerated, did not produce any treatment-related effects, and had no effect on immune system morphology or its functional response. These studies also demonstrated the utility of a science-based case-by-case approach to the safety evaluation of a veterinary biopharmaceutical product.

Microfilarial reduction following ProHeart® 6 and ProHeart® SR-12 treatment in dogs experimentally inoculated with a resistant isolate of Dirofilaria immitis.

BACKGROUND: Emerging resistance of heartworms (Dirofilaria immitis) to macrocyclic lactone (ML) preventives is an increasing concern for veterinarians, pet owners and animal health companies that supply heartworm preventives, with recent reports of resistant isolates identified from the Mississippi Delta region of the United States. Products that are effective in eliminating microfilariae (MF) in dogs harboring resistant heartworm infections could be important in reducing the spread of heartworm resistance. The current study was conducted to investigate the potential for ProHeart® 6 (PH 6; Zoetis) and ProHeart® SR-12 (PH 12; Zoetis) to reduce MF in dogs experimentally inoculated with an isolate of D. immitis (ZoeMo-2012) confirmed to be resistant to MLs. METHODS: Twenty-three dogs with preexisting heartworm infections (via surgical transplantation) were randomly allocated to four groups based on pretreatment (Day -14) MF counts. On Day 0, dogs received a subcutaneous injection of either saline (placebo-treated control, 6 dogs), PH 6 (0.17 mg/kg, 6 dogs), PH 12 (0.5 mg/kg, 5 dogs) or a single oral dose of moxidectin powder in a gelatin capsule (0.25 mg/kg, 6 dogs). All dogs were bled for MF counts (modified Knott's test) on Days 0 (pretreatment), 1, 3, 7, 14, 21, 28, 42, 56, and 84. Dogs in control and PH 6 groups were also bled for MF counts on Days 112, 140, and 168. No adverse events associated with treatment were observed for any dog. RESULTS: Average reductions in MF counts compared with controls for PH 6 were 9.7% on Day 1, increasing to 75.0% on Day 7, and further to 86.5% on Day 28. On Day 42, average MF reduction increased to 90.3%. Reductions increased further over the next several months with reductions of 91.3, 96.8, 96.6, and 98.9% on Days 56, 84, 112, and 140, respectively. On Day 168, the reduction was 99.3% (P < 0.0001). Average reductions in MF counts compared with controls for PH 12 were 20.9% on Day 1, increasing to 78.9% on Day 7, and further to 91.2% on Day 28. On Day 84, the reduction was 96.9%. For dogs receiving a single oral moxidectin (0.25 mg/kg) on Day 0, reductions in MF were 86.3% on Day 1 and fluctuated between 74.4 and 83.6% through Day 28. On Days 42 and 56, percentage reductions were 87.1 and 81.8%, respectively, and 92.6% at the final time point (Day 84). CONCLUSION: Both PH 6 and PH 12 were highly effective in reducing the MF levels of a confirmed ML-resistant heartworm isolate following a single dose.

Euthanasia method for mice in rapid time-course pulmonary pharmacokinetic studies.

To develop a means of euthanasia to support rapid time-course pharmacokinetic studies in mice, we compared retroorbital and intravenous lateral tail vein injection of ketamine-xylazine with regard to preparation time, utility, tissue distribution, and time to onset of euthanasia. Tissue distribution and time to onset of euthanasia did not differ between administration methods. However, retroorbital injection could be performed more rapidly than intravenous injection and was considered to be a technically simple and superior alternative for mouse euthanasia. Retroorbital ketamine-xylazine, CO(2) gas, and intraperitoneal pentobarbital then were compared as euthanasia agents in a rapid time-point pharmacokinetic study. Retroorbital ketamine-xylazine was the most efficient and consistent of the 3 methods, with an average time to death of approximately 5 s after injection. In addition, euthanasia by retroorbital ketamine-xylazine enabled accurate sample collection at closely spaced time points and satisfied established criteria for acceptable euthanasia technique.