1. What problem is Vivesto’s veterinary oncology program solving, and why is it important?
Paclitaxel is a well-established and highly effective chemotherapy in human cancer, but its use in veterinary medicine has been limited because standard formulations trigger hypersensitivity and immunogenic reactions in cats and dogs. This has left veterinarians with fewer effective options for treating aggressive animal cancers. The company’s XR-17 formulation solves this delivery problem, enabling paclitaxel to be administered safely in animals for the first time.
This unlocks a compelling market opportunity: bringing a proven cancer drug into veterinary oncology where unmet need is high and treatment options are limited. The current studies are designed to demonstrate both safety and anti-cancer effects, which is the key value inflection point for this program.
2. Where does the pilot dog study stand today, and what are the interim results telling us?
The dog study is an ongoing U.S. pilot trial in dogs with splenic hemangiosarcoma, an aggressive and common cancer. Dogs receive surgery (standard-of-care) followed by four doses of Paccal Vet (paclitaxel micellar) over 12 weeks. After that, the dogs enter a follow-up phase with regular check-ups to monitor their health and continued treatment response. Recruitment is well underway across eight veterinary clinics in four states. Based on the current recruitment rate and the positive response rate observed to date, we anticipate top-line data during the summer of 2026.The interim results reported in November, from the first 11 evaluable dogs, are particularly encouraging. Median overall survival increased to 138 days, compared with roughly 60–86 days historically for surgery alone, which is standard-of-care. Even the lower bound of the confidence interval exceeds standard outcomes, suggesting Paccal Vet may meaningfully extend survival in dogs with hemangiosarcoma. If confirmed at study completion, this would be a strong validation of both the formulation and the commercial case. The next step would then be to initiate a pivotal trial to further document the efficacy and safety of Paccal Vet in a larger cohort of dogs, with the goal of obtaining full marketing approval. At the same time, positive results may also allow us to seek a conditional approval after commercial production has been set up, potentially enabling us to bring Paccal Vet to market well ahead of the completion of the pivotal study.
3. How is the dose-finding study in cats progressing and when is data expected?
The Paccal Vet cat study is the first of its kind for this formulation and is focused on establishing the maximum tolerated dose while observing early signs of efficacy. In this study, cats with difficult-to-treat solid tumors (often after failing other therapies) receive the same four-dose, three-week cycle of Paccal Vet used in dogs.
While the original plan was to include up to 12 cats, the number has been increased to approximately 15–18 cats, as the treatment has been better tolerated than anticipated. The cats are being recruited across three U.S. sites, and top-line data are expected in the first half of 2026, with timing dependent on recruitment and dose escalation.
So far, results are promising: no dose-limiting toxicities have been observed in the completed dose cohorts, and the study has already escalated to higher dosing levels than initially expected. Importantly, early clinical responses have been seen in tumors such as lymphoma and carcinoma.
The next steps include completing enrollment and dose escalation to identify the maximum tolerated dose and positioning the program for broader development.
We are very excited to bring this new treatment forward in clinical development, and eventually to the market, as there are still no approved drugs for the millions of cats diagnosed with cancer every year.
4. What’s new in the Cantrixil program?
Cantrixil is a novel chemotherapy candidate for hard-to-treat hematological cancers, with a unique mechanism of action that targets not only bulk tumor cells but also resistant, relapse-driving cancer stem cells. At the end of 2025, positive results were obtained from preclinical studies in an animal model of Acute Myeloid Leukemia (AML), where Cantrixil demonstrated efficacy as monotherapy and when combined with drugs used in standard-of-care treatments. These newly disclosed data are consistent with earlier preclinical in vitro results, which showed Cantrixil’s strong cytotoxic activity across multiple hematological cancer cell lines, with particularly potent effects in relapse-derived cells, as well as synergistic effects when combined with other anti-cancer agents.
These findings, combined with the significant unmet medical need and the attractive commercial opportunity, formed the basis for our strategic decision to prioritize continued development in acute myeloid leukemia (AML), where new treatment options and combination approaches are urgently needed.
Another major recent development is the filing of a new international method-of-use patent. Besides the potential to significantly strengthen the IP position, the filing now allows us to share detailed preclinical results that were previously confidential, enabling more substantive discussions of the program’s value and development path with potential partners.
5. In which development stage is Cantrixil now, and what are the next milestones?
Cantrixil is in preclinical development and the program has been significantly de-risked. The Cantrixil programis now advancing toward human clinical development, with a PK/toxicology study in dogs planned for the first half of 2026 to assess intravenous dosing and systemic exposure in support of clinical trial design.
Next steps include completing the remaining preclinical work and preparing for the initiation of a clinical Phase 1 study in human AML, which is targeted for post-2026, alongside continued CMC development. Given Cantrixil’s unique mechanism of action, encouraging safety profile, and the strong synergies between the veterinary and human programs, we have also announced an expansion of the program into veterinary oncology with a pilot study in cancer-affected dogs to be planned in the second half of 2026 data from the already planned PK/toxicology study in dogs is available.