Purpose: Anti-angiogenic agents combined with histone deacetylase inhibitors act synergistically in vitro and in vivo. We conducted a phase I study of the combination of the anti-VEGF monoclonal antibody bevacizumab and histone deacetylase inhibitor valproic acid in patients with advanced cancers.
Methods: Bevacizumab was administered at escalating dosages of 2.5-11 mg/kg on days 1 and 15, and oral valproic acid at dosages of 5.3-10 mg/kg on days 1-28 every 28 days to determine the maximum tolerated dose. Pharmacodynamic parameters were assessed in peripheral blood mononuclear cells (histone H3 acetylation) and serum (valproic acid levels).
Results: Fifty-seven patients were enrolled. Dose-limiting toxicities were grade 3 altered mental status (n = 2), related to valproic acid. Bevacizumab 11 mg/kg given on days 1 and 15 and valproic acid 5.3 mg/kg daily were the recommended phase II dosages. Stable disease (SD) ≥6 months was reported in 4/57 (7 %) of patients, including two patients with colorectal cancer who had progressed previously on bevacizumab. Of the 39 patients evaluated for histone acetylation, 2 of 3 (67 %) patients with SD ≥6 months showed histone acetylation, while 8 of 36 (22 %) without SD ≥6 months demonstrated histone acetylation (p = 0.16). Patients with any grade of hypertension, compared to others, had a prolonged median survival (11.1 vs. 5.8 months; p = 0.012).
Conclusions: The combination of bevacizumab 11 mg/kg and valproic acid 5.3 mg/kg is safe in patients with advanced malignancies, with activity in colorectal, gastroesophageal junction, and prostate cancer. Patients with hypertension had improved overall survival.