Oral glucocorticoid pulse therapy for induction of treatment of canine pemphigus foliaceus - a comparative study

Pharmacology of drugs used in autoimmune dermatopathies in cats and dogs: A narrative review

Immunosuppressive drugs are the mainstay of treatment for many feline and canine autoimmune skin diseases, either as monotherapy or in combination with other drugs. Treatment with these drugs is often lifelong and may have long-term consequences on the affected animal's overall quality-of-life. Clinicians need to understand the pharmacology of immunosuppressants in planning and executing the treatment regimen for the best possible clinical outcome, as well as reducing the risk of adverse effects. This review paper will focus on the mechanism of action, pharmacokinetics and pharmacodynamics, clinical uses and adverse effects of immunosuppressive drugs used to treat autoimmune dermatoses in cats and dogs. These include glucocorticoids, ciclosporin A, azathioprine, chlorambucil, mycophenolate mofetil, oclacitinib and Bruton's tyrosine kinase inhibitors.

Re-evaluating the prevalence of anti-desmocollin-1 IgA autoantibodies in canine pemphigus foliaceus

Pemphigus foliaceus (PF) is an autoimmune skin disease of dogs characterized by intraepidermal pustules containing neutrophils and dissociated keratinocytes that develop in association with circulating and tissue-bound IgG autoantibodies. A subset of IgG autoantibodies in canine PF target desmocollin-1 (DSC1), a component of intercellular adhesion complexes within the epidermis. Passive transfer of IgG autoantibodies from canine PF sera to mice was previously shown to induce skin disease in the absence of infiltrating neutrophils. In attempts to identify a mechanism responsible for neutrophil recruitment, past studies evaluated the prevalence of IgA autoantibodies in canine PF sera where they were found in <20% of affected dogs. We re-evaluated the prevalence of anti-DSC1 IgA in canine PF due to concerns regarding the sensitivity of previously used methods. We hypothesized that anti-DSC1 IgA are present in most dogs with PF but have been under-detected due to competition with concurrent anti-DSC1 IgG for binding to their mutual antigenic target. Despite removing approximately 80% of IgG from patient sera using affinity chromatography, we did not detect an increase in anti-DSC1 IgA by performing indirect immunofluorescence on canine DSC1-transfected HEK293T cells. Taken together, our results do not support a role for pathogenic IgA in canine PF.

Microarray Gene Expression Analysis of Lesional Skin in Canine Pemphigus Foliaceus

Canine pemphigus foliaceus (PF) is considered the most common autoimmune skin disease in dogs; the mechanism of PF disease development is currently poorly understood. Therefore, this study aimed to characterize the molecular mechanisms and altered biological pathways in the skin lesions of canine PF patients. Using an RNA microarray on formalin-fixed, paraffin-embedded samples, we analyzed the transcriptome of canine PF lesional skin (n = 7) compared to healthy skin (n = 5). Of the 800 genes analyzed, 420 differentially expressed genes (DEGs) (p < 0.05) were found. Of those, 338 genes were significantly upregulated, including pro-inflammatory and Th17-related genes. Cell type profiling found enhancement of several cell types, such as neutrophils, T-cells, and macrophages, in PF skin compared to healthy skin. Enrichment analyses of the upregulated DEGs resulted in 78 statistically significant process networks (FDR < 0.05), including the Janus kinase signal transducer and activator of transcription (JAK-STAT) and mitogen-activated protein kinase (MAPK) signaling. In conclusion, canine PF lesional immune signature resembles previously published changes in human pemphigus skin lesions. Further studies with canine PF lesional skin using next-generation sequencing (e.g., RNA sequencing, spatial transcriptomics, etc.) and the development of canine keratinocyte/skin explant PF models are needed to elucidate the pathogenesis of this debilitating disease.

The use of oclacitinib compared to azathioprine in the management of canine pemphigus foliaceus: A retrospective analysis

BACKGROUND

Oclacitinib (Apoquel; Zoetis) has been reported to be beneficial for treating immune-mediated disorders.

HYPOTHESIS/OBJECTIVES

This retrospective study evaluates in which group of dogs [oclacitinib (OC) or azathioprine (AZ)] remission of pemphigus foliaceus (PF) was more effectively achieved with matched induction dosing of glucocorticoids; it further evaluates which group had a higher glucocorticoid-sparing effect.

ANIMALS

Review of 30 medical records of dogs diagnosed with PF presented to a private practice dermatological service.

MATERIALS AND METHODS

Retrospective analysis of dogs diagnosed with PF and treated with OC or AZ in combination with glucocorticoids.

RESULTS

There was no significant difference in the ability to induce remission between AZ and OC groups. In the AZ group, 13 of 15 dogs went into some type of remission (partial or complete), compared with 11 of 15 in the OC group. There was no significant difference between the two groups for the glucocorticoid-sparing effect. The AZ group had an average reduction of 77.9% from the induction glucocorticoid dose, and OC group had an average reduction of 64.4%. One of 15 patients in the AZ group and three of 15 patients in the OC group had a 100% reduction of the glucocorticoid dose.

CONCLUSIONS AND CLINICAL RELEVANCE

These results indicate that OC can be considered as a treatment option for canine PF.

Case report: Uncommon immune-mediated skin disease involving systemic disorders in dogs

Case 1, a 6-year-old, spayed female Pug, presented with severe systemic urticaria, edema, and erythema. The dog had received a famotidine injection as a treatment for repeated vomiting in another hospital. On physical examination, hyperthermia was observed. Moderate pancytopenia, hypoalbuminemia, and increased CRP and D-dimer were also observed in blood tests. Hyposthenuric proteinuria, pulmonary interstitial infiltration, and hepatomegaly were found in other tests. In the histology of the skin, dermal edema and infiltration of inflammatory cells were observed. Therefore, she was diagnosed with acute systemic hypersensitivity. Case 2, a 13-month-old, neutered male Pembroke welsh corgi, presented with severe and patchy systemic ulcerative skin lesions. The dog had a history of soft feces and pain around the anus 2 days before. Thrombocytopenia, and increased CRP and D-dimer were observed in blood tests. In histology, epidermal necrolysis, separation of the epidermis and dermis, and infiltration of inflammatory cells were observed. Therefore, he was diagnosed with an immune-mediated disease with necrolysis dermatitis. Case 3, a 12-year-old, spayed female Pomeranian, presented with severe systemic alopecia, pustule, and crust on the skin. The dog had received an infection treatment from a local hospital. Severe regenerative anemia (hematocrit 15.3%, negative saline agglutination test, negative slide agglutination test, negative Coomb's test, prominent spherocytes) elevated liver enzymes, and increased CRP and D-dimer were observed in blood tests. On histopathology of the skin, pustules, acantholytic cells, and inflammatory cells were observed in the keratin layer of the epithelium. Therefore, she was diagnosed with Pemphigus foliaceus concurrent with immune-mediated hemolytic anemia. The 3 cases were diagnosed with fatal immune-mediated skin disease concurrently with hematological and systemic abnormalities. All the cases were treated with immune-suppressive drugs, prednisolone, and cyclosporine. In cases 2 and 3, the dogs also received human intravenous immunoglobulin as an immune modulator. The treatment was successful with significant improvements in all the 3 cases.

A Retrospective Evaluation of the Steroid-Sparing Effect of Oral Modified Ciclosporin for Treatment of Canine Pemphigus Foliaceus

The efficacy of ciclosporin as an adjuvant immunosuppressant administered with glucocorticoids (GCs) for induction of canine PF remission is unknown. This study is a retrospective review of medical records from 2015 to 2020 to evaluate the therapeutic outcomes of 11 PF dogs treated with oral modified ciclosporin and GCs. Concurrent GCs were given with ciclosporin to all PF dogs. Nine dogs (9/11) achieved complete remission (CR); five dogs received ciclosporin at a mean dose of 6.2 mg/kg/day; and four dogs received a combination of ciclosporin and ketoconazole at a mean dose of 3 mg/kg/day, respectively. Two dogs (2/11) showed only 25% or poor response, with the development of new PF lesions during treatment. The mean duration of ciclosporin therapy for nine dogs to achieve CR was 65 days (median 57 days, range 24–119 days). Slow tapering of oral GCs while continuing ciclosporin at the same dose and frequency in nine dogs with CR led to recurrence of PF lesions in four dogs, whereas, in five dogs, oral glucocorticoids were discontinued without a PF flare. Oral modified ciclosporin combined with GCs achieved CR in 9 out of 11 PF dogs during the induction phase in this study.

A retrospective evaluation of the steroid sparing effects of oral mycophenolate mofetil (MMF) as an adjunct immunosuppressant for the treatment of canine pemphigus foliaceus

BACKGROUND

Oral mycophenolate mofetil (MMF) is currently considered a low-risk steroid-sparing therapeutic option the management of canine pemphigus foliaceus (PF).

OBJECTIVES

This retrospective study evaluates the therapeutic outcomes of dogs with PF treated with the combination of oral MMF and GC. Clinical outcomes and side effects are reported.

ANIMALS

Eleven dogs diagnosed with PF.

METHODS AND MATERIALS

Retrospective review of medical records from dogs presented with PF to the dermatology service of a veterinary teaching hospital 2015-2020.

RESULTS

Eleven dogs were identified which had received concurrent GCs and MMF. The MMF dose range was 19.8-45 mg/kg/day. Only two dogs (2/11) treated with a mean MMF dosage of 39 mg/kg/day along with oral prednisone or dexamethasone achieved complete remission (CR). Partial remission (PR) was achieved in 4/11 dogs who received either prednisone, prednisolone or dexamethasone along with MMF (mean dosage 26 mg/kg/day). Four dogs (4/11) showed poor response to MMF given at 28.5 mg/kg/day along with prednisone or dexamethasone. In one dog (1/11) MMF was discontinued due to severe GI upset; transient vomiting and diarrhea was observed in 4/11 dogs. The median duration of MMF therapy in conjunction with GC for all groups was 70.5 days. Tapering of oral GCs while continuing MMF administration at the same dosage and frequency led to recurrence of lesions in all PF patients.

CONCLUSION

Oral MMF combined with GC achieved CR in 2 out of 11 PF dogs included in this study. Further research of MMF efficacy in PF may need to be performed.

Open trial of Bruton's tyrosine kinase inhibitor (PRN1008) in the treatment of canine pemphigus foliaceus

BACKGROUND

Bruton's tyrosine kinase (BTK) is important in B-cell signalling. Efficacy has been reported for BTK inhibitors (BTKi) in human autoimmune diseases. Canine pemphigus foliaceus (cPF) is one of the most common canine autoimmune skin diseases.

OBJECTIVES

To determine the safety and efficacy of the BTKi PRN1008 in the treatment of cPF.

ANIMALS

Four privately owned dogs.

METHODS AND MATERIALS

Four dogs diagnosed with PF were administered BTKi PRN1008. Initial dosages approximated to 15 mg/kg once daily, increased to twice daily if inadequate response was seen. Treatment continued for 20 weeks, attempting to decrease to every other day. Dogs were monitored with complete blood counts, serum biochemistry panels and urinalyses, and evaluated with a modified version of a validated human Pemphigus Disease Activity Index (cPDAI). Serum anti-desmocollin-1 (DSC-1) and desmoglein-1 (DSG-1) immunoglobulin (Ig)G titres were performed before and after the treatment period. Drug bound to target was measured in peripheral blood mononuclear cells (PBMC).

RESULTS

All four dogs showed reduction in lesions and cPDAI score during the first two weeks of treatment. Three dogs continued to improve and sustained near complete remission by 20 weeks, at which point three responses were considered "good" and one "fair". Final daily dosages were in the range 17-33 mg/kg. Anti-DSC-1 IgG titre decreased dramatically in one dog, was undetectable in two and was uninterpretable in one dog. No dogs had detectable IgG to DSG1. A possible adverse event occurred in one dog.

CONCLUSIONS AND CLINICAL IMPORTANCE

BTKi PRN1008 monotherapy may have some beneficial effects in some cases of cPF.

Efficacy of a Bruton's Tyrosine Kinase Inhibitor (PRN-473) in the treatment of canine pemphigus foliaceus

BACKGROUND

Bruton's tyrosine kinase (BTK) is important in B-cell signalling. Efficacy has been reported for BTK inhibitors (BTKi) in human autoimmune diseases. Canine pemphigus foliaceus (cPF) is the most common canine autoimmune skin disease.

OBJECTIVES

To determine the safety and efficacy of a BTKi in cPF treatment.

ANIMALS

Nine privately owned dogs.

METHODS AND MATERIALS

Nine dogs diagnosed with PF were administered BTKi PRN473. Initial dosages were ≈15 mg/kg once daily, increased to twice daily if inadequate response was seen. Treatment continued for a maximum of 20 weeks, attempting decrease to every other day. Dogs were monitored with complete blood counts, serum biochemistry panels, urinalyses and evaluated with a modified version of a validated human Pemphigus Disease Activity Index (cPDAI). Anti-desmocollin-1 (DSC-1) and desmoglein-1 (DSG-1) immunoglobulin G (IgG) titres were performed before and after the treatment period. Drug bound to target was measured in peripheral blood mononuclear cells.

RESULTS

All nine dogs showed reduction in lesions and cPDAI score during the first two weeks of treatment. At the end of the study, four responses were considered "good", two "fair", two "poor" and one dog withdrawn due to recurrence of a previously excised mast cell tumour. Four dogs continued to improve by Week 4; three sustained near complete remission by study's end. The anti-DSC-1 IgG titre decreased in three dogs, increased in two, was undetected in three and was not performed in the withdrawn dog. No dogs had detectable IgG to DSG1. Possible adverse effects occurred in three dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Bruton's tyrosine kinase inhibitor monotherapy may have beneficial effects in some cases of cPF.

Feline pemphigus foliaceus: original case series and a comprehensive literature review

BACKGROUND

Since the first description of feline pemphigus foliaceus (PF) more than 30 years ago, numerous case reports have been published, while larger case series have remained rare. This large body of information, if extrapolated, could address clinical discrepancies and expand our knowledge about the treatment of feline PF. This manuscript reviews cases of feline PF published between 1950 and 2016 and adds additional 35 original cases to provide further insight into the clinical aspect and treatment outcome of this disease.

RESULTS

Feline PF, while being a primary acantholytic pustular dermatosis, presents most often with crusts and erosions that predominantly affect the face and feet. More than half of cats with active disease exhibits non-dermatological signs such as lethargy, fever and/or anorexia. The prognosis of feline PF is good as the majority of cats rapidly achieve disease control even with the most basic treatment such as glucocorticoid monotherapy. Most PF-affected cats, however, require long-term treatment and, like other autoimmune diseases, feline PF has a tendency to relapse spontaneously or with treatment changes.

CONCLUSIONS

Therefore, despite the overall good prognosis cats with PF can be given, owners should be informed and prepared for these circumstances, which may reduce the risk of euthanasia in the case of disease relapse, and improve treatment compliance.

Therapeutic effectiveness of calcineurin inhibitors in canine vesicular cutaneous lupus erythematosus

BACKGROUND

Oral and topical calcineurin inhibitors (CIs) have been reported to lead to complete lesion remission in several dogs with vesicular cutaneous lupus erythematosus (VCLE).

OBJECTIVES

To report retrospectively on the effectiveness and adverse effects of systemic (ciclosporin) and/or topical (tacrolimus/pimecrolimus) CIs in 11 dogs with VCLE.

METHODS

Inclusion criteria were: (i) presence of characteristic annular, polycyclic or serpiginous ulcerations distributed over the groin, axillae and/or ventral abdomen; (ii) a histopathological diagnosis of VCLE (i.e. a lymphocyte-rich interface dermatitis with vesiculation); (iii) treatment that included CIs for at least eight weeks; and (iv) follow-up until death/euthanasia or for a minimum of 12 months post-diagnosis.

RESULTS

Initial therapy included the avoidance of excessive sun exposure, oral glucocorticoids [six of 11 dogs (55%); progressively tapered over a month] and once daily ciclosporin [11 dogs (100%); median 5.8 mg/kg]. A complete remission (CR) of signs occurred between days 35 and 70 after starting CIs in eight dogs (73%); increasing ciclosporin dosage and adding topical tacrolimus induced a CR in two additional dogs (18%). Relapses were common when doses were tapered or discontinued. With the exception of three dogs that were euthanized, clinical signs were maintained in CR with oral ciclosporin (eight of eight dogs treated, 100%) or topical tacrolimus/pimecrolimus (four of eight dogs; 50%) with a median follow-up of 2.9 years.

CONCLUSIONS AND CLINICAL IMPORTANCE

These observations support CIs as the preferable therapeutic alternatives to long-term immunosuppression with oral glucocorticoids in dogs with VCLE.