Paxalisib Achieves 100% Clinical Benefit Rate in Metastatic TNBC
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Kazia Therapeutics announced that paxalisib produced a 100% clinical benefit rate and an 83% objective response rate in evaluable stage IV triple-negative breast cancer patients.
The investigational PI3K/Akt/mTOR inhibitor paxalisib produced a 100% clinical benefit rate among 6 evaluable patients with stage IV triple-negative breast cancer (TNBC), according to a news release from the developer, Kazia Therapeutics.
Five of the 6 patients achieved an objective response, defined as a 30% or greater reduction in tumor burden, including 1 complete response and 4 partial responses, for an objective response rate of 83%. Of note, the remaining patient achieved stable disease. No paxalisib-related serious adverse events were reported, and investigators observed no grade 3 or higher hyperglycemia, stomatitis, or mucositis, toxicities that are commonly associated with PI3K/mTOR pathway inhibition.
These findings build on earlier data from the same ongoing phase 1b trial, which CancerNetwork previously reported showed meaningful clinical activity with paxalisib plus pembrolizumab (Keytruda) and chemotherapy in patients with metastatic TNBC.
Main Paxalisib Data
Clinical responses were observed across a broad range of metastatic disease sites, including the lung, liver, bone, lymph nodes, and central nervous system. Responses emerged as early as approximately 3 months after treatment began. The press release highlighted that a 44-year-old woman with stage IV TNBC achieved a complete metabolic response that has remained durable since November 2025. Her response has been accompanied by sustained and complete abolishment of circulating tumor cell (CTC) clusters and a significant reduction in terminally exhausted CD8-positive T cells, alongside an overall improvement in markers of immune function.
“Metastatic triple-negative breast cancer is one of the toughest cancers to treat. Historically, only 12% of patients are alive 5 years after diagnosis. Once a patient’s disease progresses on immunotherapy, options run out quickly,” said John Friend, MD, chief executive officer of Kazia Therapeutics, in the news release. “Across the 6 evaluable patients treated, every one of them has benefited, and we haven’t seen a single serious adverse event tied to paxalisib.”
