A pilot phase II study of the efficacy and biosafety of doxorubicin chemotherapy in tumor-bearing equidae.

This research pilot study investigates the effectiveness and safety of the use of doxorubicin, a chemotherapy drug, for treating various tumors in horses. It also examines the drug’s pharmacokinetics profile and the period of exposure to drug residues.

Research Objective and Methods

• The research sought to provide initial evidence of the impact of doxorubicin on tumor-bearing horses, examine the drug’s pharmacokinetic profile, and evaluate the duration of exposure risk to drug residues.
• The study was conducted on 12 horses bearing 37 tumors. A chemotherapy regimen of six treatments at three-week intervals was used.
• Eight of the horses were consistently administered a dose of 70 mg/m^2, while the other four received the same dose for four of the six treatment cycles.
• Clinical signs, tumor responses, and toxicosis were analyzed as part of the study. The drug residue concentrations were quantified in three horses given dosages of 65, 70, and 75 mg/m^2. The researchers used high-performance liquid chromatography, along with ultraviolet detection for plasma and feces samples, and liquid chromatography and tandem mass spectrometry for urine samples.

Study Results

• A wide array of tumors such as lymphomas, carcinomas, sarcoids, and melanomas were assessed for the drug’s efficacy, with an overall response rate of 47%. However, doxorubicin was not found to be effective in treating melanomas, with lymphomas and carcinomas showing the most responsiveness.
• Pooling the serum, the researchers found that the peak concentration (Cmax) and the half-life of doxorubicin in the blood were 121.3 ng/mL and 12.9 hours, respectively.
• According to the findings, there were no detectable residues in fecal samples up to three weeks after treatment, or in plasma and urine after two and three days, respectively.

Study Conclusions

• The research offered preliminary evidence that doxorubicin, when used as a single-agent at a dose of 70 mg/m^2, displayed a broad spectrum of activity against various types of tumors in horses.
• It was also found that the risk of exposure to drug residues in plasma and feces was low. However, the horses should not be allowed to be in contact with urine-contaminated waste for at least two days after treatment.