Phase I Clinical Trial and Pharmacodynamic Evaluation of Combination Hydroxychloroquine and Doxorubicin Treatment in Dogs with Lymphoma


Dogs, just like humans, can develop lymphoma, a type of cancer that affects the lymphatic system. In recent years, there has been growing interest in exploring new treatment options for this disease. One promising avenue of research is the inhibition of a process called autophagy, which has been found to play a role in cancer progression and therapy resistance.

Autophagy is a natural process that helps cells recycle proteins and organelles, acting as a quality control mechanism and providing essential nutrients. However, in cancer, autophagy can enhance tumor survival and resistance to treatment. Studies conducted on mice have shown that combining standard cancer therapies with autophagy inhibitors such as hydroxychloroquine (HCQ) can lead to improved treatment outcomes.

However, before such treatments can be implemented in clinical practice, it is crucial to determine the safe and effective dosage of HCQ when used in combination with other chemotherapy drugs. This is particularly important in dogs, as autophagy inhibition may have adverse effects on organs like the gut, kidneys, and liver. Additionally, understanding the pharmacokinetics of HCQ in dogs is necessary to ensure its optimal use and minimize potential toxicity.

Clinically, HCQ has been used to treat malaria and autoimmune diseases in humans, but its effectiveness and safety in dogs with cancer have not been fully explored. To address these knowledge gaps, a Phase I clinical trial was conducted to evaluate the effects of combination HCQ and doxorubicin treatment in dogs with lymphoma.

Findings of the Study:

The study involved pet dogs with naturally occurring lymphoma, which serves as a relevant model for human lymphoma due to its similarities in pathogenesis, response to treatment, and tumor biology. Dogs with lymphoma often experience spontaneous metastasis and therapy resistance, making them an ideal subject for this research.

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The trial aimed to determine the maximum tolerated dose of HCQ in combination with doxorubicin, assess any dose-limiting toxicities, and evaluate the pharmacokinetic and pharmacodynamic relationships of the treatment. Furthermore, researchers also looked for preliminary evidence of antitumor activity.

Results showed that HCQ could be used safely in dogs with lymphoma, with no significant alterations in liver function or hematology. This finding is particularly encouraging, as it suggests that combining HCQ with standard chemotherapy drugs may offer a potential benefit in treating lymphoma. Further research is needed to fully explore the antitumor activity of this combination therapy.


The Phase I clinical trial examining the use of combination HCQ and doxorubicin treatment in dogs with lymphoma has provided valuable insights into the safety and potential benefits of autophagy inhibition in cancer therapy. The findings of this study support the translational utility of the canine cancer model, which closely mimics human tumor biology and progression.

By utilizing pet dogs as clinical subjects, researchers can conduct comprehensive assessments of therapeutic endpoints and treatment protocols in a relatively short timeframe. These studies not only inform future human clinical trials but also contribute to advancements in veterinary medicine.

The results of this trial open up new possibilities for improving lymphoma treatment in both dogs and humans. Further research is needed to fully understand the mechanisms behind autophagy inhibition and its effects on tumor response. With continued exploration and refinement, combination therapies involving HCQ may revolutionize the field of cancer treatment, benefiting both our furry friends and ourselves.

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