Vivesto reports positive Paccal Vet cat topline results supporting continued clinical development

Preliminary results from all 21 enrolled cats in Vivesto’s Paccal Vet (paclitaxel micellar) dose-finding study demonstrated clear indications of anti-tumor effects across multiple tumor types and dose levels. To date, best biological responses have been observed in 15 cats, including 1 complete response, 6 partial responses, and 8 cases of stable disease, with stable disease defined as stable disease maintained for at least six weeks. In addition, the study established a higher-than-expected MTD, reflecting the favorable tolerability profile of Paccal Vet and allowing the evaluation of higher dose levels than initially anticipated.

"The positive topline results, including clear anti-tumor activity and a higher-than-expected MTD in cats with cancer, mark an important milestone for the Paccal Vet program and provide an encouraging foundation for selecting future target indications," said Erik Kinnman, CEO of Vivesto. "These results increase the commercial attractiveness of Paccal Vet and support our ongoing business development activities together with Liberi Group."

The primary objective of the study was to establish the MTD of Paccal Vet (paclitaxel micellar) in cats. In addition to determining an appropriate dose for future development, the study included exploratory assessments of Paccal Vet anti-tumor activity across diverse tumor types such as lymphoma, sarcoma and carcinoma.

Treatment was well tolerated, with side effects consistent with those commonly associated with chemotherapy, including decreased appetite, lethargy and neutropenia (a temporary reduction in white blood cells). Most side effects were mild and temporary and could be managed with supportive medication. No hypersensitivity reactions were observed.

The study was initially designed to include up to 12 cats in a 3+3 dose-escalation design. Recruitment was subsequently expanded as Paccal Vet was tolerated better than anticipated, allowing the study to continue into progressively higher dose cohorts and include additional patients. In the study, cats were treated with up to four treatment cycles of Paccal Vet at three-week intervals across three clinical sites in the US.

All cats have completed treatment, which is now followed by data cleaning, monitoring and statistical analyses. The final analysed results are expected in Q4 2026 and will support the selection of tumor types and dosing regimen for future clinical development and provide further guidance for ongoing partnering discussions.

For more information:
Erik Kinnman, Chief Executive Officer
Phone: +46 018-50 54 40
E-mail: IR@vivesto.com

About Vivesto AB

Vivesto is a Swedish development company that aims to offer new treatment options for hard-to-treat cancers where there are major medical needs and significant market potential. The project portfolio consists of Cantrixil, which is being developed for blood cancer, and the veterinary oncology program Paccal Vet (paclitaxel micellar), which is being evaluated in a pilot clinical trial in dogs with splenic hemangiosarcoma following splenectomy and in a dose-finding study in cats with solid tumors. Vivesto’s shares are traded on Nasdaq Stockholm (ticker: VIVE). Visit www.vivesto.com for more information about Vivesto.

About Paccal Vet

Vivesto’s drug candidate Paccal Vet consists of paclitaxel formulated with the company’s proprietary XR-17 technology, which enables solubility without the undesirable effects of traditional formulations containing solvents. The absence of the solvent cremophor, to which cats and dogs are particularly sensitive, may reduce the risk of serious side effects and death associated with treatment.

Paccal Vet also does not require the addition of human albumin, which when used in cats and dogs can cause hypersensitivity reactions and reduced treatment effectiveness. Previous clinical studies performed by Vivesto have demonstrated safety in more than 300 dogs. Anti-tumor activity has also been shown in squamous cell carcinoma and non-resectable mammary carcinoma of stage III-V. Vivesto is also conducting a Paccal Vet dose-finding study in cats with solid tumors.

About cancer in cats
The need for safe and effective cancer treatment in cats is vast and increasing as the number of pets grows. Estimates indicate that there are more than 95 million cats in the United States alone and approximately 6 million of those are diagnosed with cancer each year. There are currently no approved drugs for the treatment of cancer in cats and current paclitaxel formulations are not tolerated by cats and therefore cannot be used.