Cancer biotech Vivace Therapeutics is tuning up for a phase 3 trial after its potential first-in-class small molecule scored a 32% objective response rate in patients with treatment-resistant mesothelioma.
In an ongoing phase 1/2 trial of VT3989, seven out of 22 evaluated patients showed a partial response to treatment, meaning their tumors shrank by at least 30% in size, while 12 others had their tumor size stabilize, Vivace announced in an Oct. 19 release.
Additionally, these 22 patients survived without their cancer advancing for a median of 40 weeks, Vivace said, “more than double the 15-week benchmark for standard-of-care salvage chemotherapy.”
The Bay Area biotech presented the results at the 2025 European Society for Medical Oncology congress today, while simultaneously publishing the results in Nature Medicine.
“These findings make a compelling case for the therapeutic potential of VT3989 in the treatment of mesothelioma, a cancer that presents significant treatment challenges and for which there are few therapeutic options beyond first‑line therapies” Timothy Yap, Ph.D., a medical oncologist at MD Anderson Cancer Center and lead investigator for the study, said in the release. “We believe that the strength of these efficacy findings, combined with the encouraging safety profile demonstrated in the study, support the advancement of VT3989 into a registrational clinical trial for mesothelioma.”
That safety profile includes no dose-limiting toxicities across 172 patients and a 3.5% rate of discontinuation due to adverse events, Vivace said in the release, with most adverse events mild or moderate in severity.
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The trial has enrolled 172 patients in total, 135 of whom have mesothelioma; other solid tumors represented include meningioma, epithelioid hemangioendothelioma and sarcoma. Of the patients with mesothelioma, 22 of them received the optimized dose of VT3989.
Vivace plans to launch a phase 3 study of VT3989 in mesothelioma in the first half of 2026, the company said.
Mesothelioma is cancer of the thin layer of tissue that coats internal organs, and is most commonly associated with asbestos exposure. Breathing in asbestos can lead to pleural mesothelioma, the most common form of the cancer, in the tissue surrounding the lungs. Other forms of the disease can affect tissue around the stomach, heart or testicles.
If approved, VT3989 would be the first drug to target the Hippo pathway, which controls cell growth, migration and death. Many cancer cells, including in mesothelioma, have an overactive Hippo pathway, Yap and colleagues wrote in the Nature Medicine paper. VT3989 is designed to dampen this overexcited system by inhibiting a group of transcription factors called TEAD, which play a key role in regulating the Hippo pathway.
Vivace’s clinical plans got a boost earlier this year, when the biotech closed a $35 million series D round. That funding followed a $30 million series C in 2020 and the company’s $40 million launch in 2017.
