Masitinib
Masitinib mesylate
Also known as: Masivet · Kinavet · Masitinib mesilate
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Non-resectable mast cell tumours (Patnaik grade 2 or 3) | See Appendix for chemotherapy protocols | PO | unknown | unknown | 🌍 EU |
- Non-resectable mast cell tumours (Patnaik grade 2 or 3): Preferably with a confirmed mutated c-KIT tyrosine kinase receptor.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Injection site sarcoma, asthma (investigational) | Limited evidence: administered to healthy cats | PO | unknown | unknown | 🌍 EU |
- Injection site sarcoma, asthma (investigational): Not licensed in cats. Further clinical trials required. Monitor closely.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Masitinib is a protein tyrosine kinase inhibitor primarily used in veterinary medicine for the treatment of non-resectable mast cell tumours in dogs, particularly those with a confirmed mutated c-KIT receptor. It is also being investigated for use in other inflammatory and neoplastic conditions such as atopic dermatitis, inflammatory bowel disease, osteosarcoma, and haemangiosarcoma.
Clinical Warning: Masitinib is a cytotoxic drug. Strict safety and handling protocols must be followed by both veterinary staff and pet owners to prevent accidental exposure.
Mechanism of action
Masitinib acts as a protein tyrosine kinase (TK) inhibitor. It selectively and effectively binds with high affinity to mutated forms of the c-KIT tyrosine kinase receptor.
c-KIT receptor → Inhibition blocks the TK receptor pathways that are essential for cell replication, survival, and differentiation, thereby halting tumor growth and progression.
Safety & warnings
Contraindications
- Pregnant or lactating bitches
- Dogs < 24 months old
- Dogs < 7 kg body weight
- Pre-existing signs of myelosuppression
- Previous hypersensitivity to masitinib
Adverse effects
- Diarrhoea (mild to moderate)
- Vomiting (mild to moderate)
- Hair coat changes or alopecia
- Renal toxicity
- Anaemia
- Protein loss (protein-losing nephropathy/enteropathy)
- Myelosuppression
- Increased liver enzyme activity
- Lethargy
- Cough
- Lymphadenomegaly
Precautions
Cytotoxic Handling: Handle with care using appropriate chemotherapeutic safety guidelines. Do not split or crush tablets.
Use with caution in patients with pre-existing renal or hepatic dysfunction.
Patients require intensive monitoring. Blood pressure, urinalysis, haematology, and biochemistry should be checked before starting therapy, and then at least once a month (or 1-2 weeks after initiation). Full coagulation profiles and faecal occult blood tests are required if adverse clinical signs occur.
Drug interactions
May displace masitinib or be displaced, increasing the risk of adverse side effects
May alter the metabolism of masitinib, increasing the risk of toxicity or reducing efficacy
Monitoring
- Blood pressure (baseline and monthly)
- Urinalysis (baseline and monthly)
- Haematology (baseline and monthly)
- Biochemistry (baseline and monthly)
- Coagulation profiles (if adverse signs witnessed)
- Faecal occult blood tests (if adverse signs witnessed)
- Weekly owner check-ins for the first 6 weeks to monitor for side effects
Overdose
No specific overdose information is provided in the monograph.
Clinical Pearl: Overdose of tyrosine kinase inhibitors typically exacerbates gastrointestinal toxicity (severe vomiting, diarrhea) and myelosuppression. Treatment is symptomatic and supportive. Monitor renal and hepatic parameters closely.
Available products
Formulations
- 150 mg film-coated tablet
Veterinary
- Masivet 50 mg film-coated tablets
- Masivet 150 mg film-coated tablets
Regulatory status
POM-V. Licensed for dogs with non-resectable mast cell tumours.
POM-V. Licensed for dogs with non-resectable mast cell tumours.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store in accordance with cytotoxic drug guidelines. Keep out of reach of children and animals.
Client information
Masitinib is a targeted cancer therapy used primarily to treat mast cell tumors in dogs.
- Handling Precautions: This is a hazardous drug. Wear disposable gloves when handling the tablets and when cleaning up your pet's waste (urine, feces, vomit). Wash your hands thoroughly afterwards. Do not break or crush the tablets.
- Monitoring: Your pet will need frequent veterinary visits for blood and urine tests, especially during the first few weeks of treatment, to ensure the drug is not affecting their kidneys, liver, or bone marrow.
- Side Effects: Watch closely for vomiting, diarrhea, lethargy, or changes in the hair coat. Contact your veterinarian immediately if your pet seems unwell, as prompt action is required to manage side effects.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.