Kazia Therapeutics Reports Positive Initial Phase 1b Trial Data from First Triple-Negative Breast Cancer Patient Treated with Paxalisib Combination Regimen

July 9, 2025

DENVER, Colo., Jul 09, 2025 (247marketnews.com)- Kazia Therapeutics (NASDAQ:KZIA) announced promising early efficacy data from the first patient enrolled in its ongoing Phase 1b clinical trial evaluating a combination of Paxalisib, pembrolizumab (Keytruda), and standard chemotherapy for the treatment of metastatic triple-negative breast cancer (TNBC).

After completing the first 21-day treatment cycle (Cycle 1), the 61-year-old female patient—diagnosed with metastatic TNBC involving the left upper lung—demonstrated a >50% reduction in circulating tumor cells (CTCs) and a marked decline in CTC clusters, both considered important indicators of disease progression and metastasis.

These preliminary results reflect previously published mechanistic preclinical findings in Molecular Cancer Therapeutics, which showed that Paxalisib, when combined with immunotherapy, significantly disrupts both single CTCs and multicellular clusters in preclinical models.

Key Highlights

  • Patient Profile: 61-year-old woman with metastatic triple-negative breast cancer (lung metastasis)
  • Investigational Regimen: Paxalisib + pembrolizumab + chemotherapy
  • Cycle 1 Results (Day 21):
  • 50% reduction in total CTC count
    • Similar reduction in CTC clusters, which are strongly associated with metastatic potential
    • Decrease in mesenchymal phenotype of remaining CTCs—linked to aggressive cancer cell behavior
    • First-in-human data indicating potential for potent suppression of CTC mobilization by this combination

Clinical Implications

CTC clusters are increasingly recognized as potent drivers of metastasis and poor prognosis. Unlike single tumor cells, these clusters are highly resistant to apoptosis, capable of immune evasion, and are far more efficient at seeding new tumors.

While chemotherapy has previously been shown to transiently increase CTC and cluster counts during early treatment cycles, and immunotherapy alone often exhibits delayed impact on CTCs, this patient’s response suggests a unique synergy between Paxalisib and immunotherapy.

In just 21 days, the combination led to a rapid decline in both CTC count and clusters, as well as a reduction in aggressive cell phenotypes, outcomes not typically seen with chemotherapy or immunotherapy alone. These findings align with mechanistic data from preclinical studies and support the hypothesis of enhanced efficacy through targeted inhibition and immune modulation.

Executive Commentary

Dr. John Friend, MD, CEO of Kazia Therapeutics, commented:

“It is very exciting to see our extensive preclinical research translate into such positive early data in this first patient receiving a combination of Paxalisib and immunotherapy. The degree of reduction in tumor cell dissemination markers in just 21 days gives us strong reason for optimism as we continue this clinical trial.

“CTC clusters are emerging as key drivers of metastatic spread—they’re 20–100X more efficient at seeding than single CTCs—and the sharp decline we’re seeing is truly encouraging. We believe this combination may offer a meaningful early intervention against systemic disease progression.”

Next Steps

  • Continue enrollment to expand cohort and evaluate safety, tolerability, and pharmacodynamics
  • Assess relationship between CTC kinetics and radiographic tumor responses
  • Perform serial monitoring of immune microenvironment and CTC dynamics across the trial
  • Long-term follow-up to include imaging, progression-free survival, and biomarker correlation analysis

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