SYDNEY, Aug 27, 2026
Kazia Therapeutics Limited has reported a 100% clinical benefit rate among the first six evaluable patients treated with its investigational cancer therapy paxalisib for Stage IV triple-negative breast cancer (TNBC). The early clinical findings showed that all six patients experienced clinical benefit, with five patients achieving an objective response and one patient achieving stable disease. Among the five responders, one patient achieved a complete response and four achieved partial responses, producing an 83% objective response rate. The findings are from Kazia’s ongoing clinical development program and provide early evidence supporting further evaluation of paxalisib in advanced TNBC. The company emphasized that the results are preliminary and are being generated as enrollment continues in its Phase 1b study.
Paxalisib Shows Early Clinical Activity in TNBC
The six evaluable patients demonstrated responses across multiple metastatic sites, including lung, liver, bone, lymph nodes and central nervous system target lesions. Clinical responses emerged as early as approximately three months after randomization. Particularly notable was the case of a 44-year-old woman with Stage IV TNBC who achieved a complete metabolic response and has shown no evidence of disease since November 2025. According to the company, the response remained durable through the latest assessment. The patient’s response was also associated with sustained elimination of circulating tumor cell clusters and a significant reduction in terminally exhausted CD8+ T cells, alongside improvements in markers associated with immune function. Paxalisib is administered orally, and the initial safety findings showed no treatment-related serious adverse events and no Grade 3 or higher hyperglycemia, stomatitis or mucositis among the reported patients. These findings are important because PI3K/mTOR pathway inhibition can be associated with such toxicities.
Biomarker Data Point to Immune Reprogramming
Kazia’s translational analyses identified biological changes that may help explain the clinical responses observed in the initial patient group. Across all six evaluable patients, terminally exhausted CD8+ T cells decreased by a median of 51% within approximately three weeks of treatment, while total CD8+ T-cell counts remained unchanged. The company interprets this pattern as potentially indicating recovery of function among existing immune cells rather than their elimination or replacement. Blood-based analyses incorporating protein, RNA and plasma profiling also identified increases in immune-cell populations associated with antitumor activity, reductions in immune-exhaustion markers and evidence of PI3K-AKT pathway target engagement. These findings provide early biological support for the hypothesis that paxalisib may influence immune function in addition to its direct pathway inhibition.
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Reduced Tumor Cell Clusters Support Further Study
All six evaluable patients also demonstrated reductions in circulating tumor cell (CTC) clusters, aggressive groups of tumor cells associated with metastatic spread. The median reduction was 83% within six to seven weeks of treatment, providing another early biomarker signal alongside the observed clinical responses. Kazia believes these findings may indicate a potential dual effect of paxalisib involving immune-function restoration and reduced metastatic dissemination. The company is continuing enrollment in its Phase 1b study, which evaluates paxalisib in combination with pembrolizumab and chemotherapy in patients with advanced metastatic TNBC. Enrollment is expected to be completed by July 2027, with interim clinical updates anticipated during 2026 and 2027. However, the reported results are based on only six evaluable patients and remain preliminary; the study is not designed or powered to establish statistical significance. Further clinical investigation will therefore be necessary to determine whether the early response and biomarker findings translate into durable benefits in a larger patient population.
Source: Kazia Therapeutics press release
