Overall median duration of therapy in all 51 patients measured 5.6 months (range 1-103 months). Progression-free survival among patients with high PBMC HDAC2 expression (> 0.4) remains longer compared to those with low expression (median 6.3 vs. 3.7 months, p = 0.0041). Metabolomics analysis demonstrated a negative correlation between HDAC2 and N6-acetyllysine, suggesting that baseline HDAC2 may impact efficacy of HDAC inhibition. The combination of abexinostat with pazopanib appears promising, with the potential for long-term responses particularly in patients with metastatic RCC.