2531 Background: Vorinostat (suberoylanilide hydroxamic acid, SAHA) is an oral histone deacytlase (HDAC) inhibitor that has anti-tumor activity in hematologic malignancies and advanced solid tumors. Vorinostat has been postulated to act synergistically with bortezomib at the level of aggresome inhibition with creation of reactive oxygen species. We previously conducted a study of this combination with once-daily dosing of vorinostat with bortezomib (Step A). This study (Step B) was conducted to evaluate twice daily dosing of vorinostat during administration of bortezomib to determine safety and efficacy, pharmacokinetics, and activity this combination.
METHODS
This study used standard eligibility criteria except patients must have had no prior bortezomib. The treatment plan initially consisted of vorinostat given orally twice daily on days 1-14 with bortezomib IV on days 1, 4, 8, and 11 of a 21 day cycle. Two DLTs (elevated ALT and fatigue) were observed at level 1, and the protocol was amended to administer vorinostat twice daily on days 1-4 and 8-11. Starting dose was vorinostat 200 mg and bortezomib 1 mg/m2. RECIST was used to measure response.
RESULTS
29 pts have been enrolled; 13 men and 16 women. Tumor types include: Prostate (1), Colorectal (3), Pancreatic (6), Sarcoma (7), Biliary (1), Thymus (1), GIST (2), Mesothelioma (1), ovarian (1), Neuroendocrine (1), Lung (1), Head and Neck (1), Breast (2), and Cervical (1). Grade 3-4 toxicities possibly related to SAHA at any dose level were as follows: thrombocytopenia (5), fatigue (3), increased ALT (1), elevated INR (1), anemia, (1), hypotension (1), diarrhea (3), anorexia (1), dizziness (1), nausea/vomiting (1), and hypoalbuminemia (1). The only dose limiting toxicities included elevated ALT (1), fatigue (1). There were two deaths but neither was felt to be related to the drug. The MTD for Step B was established at vorinostat 300 mg BID and bortezomib 1.3 mg/m2.
CONCLUSIONS
The MTD for Step B was established at vorinostat 300 mg BID and bortezomib 1.3 mg/m2. Subjective evidence of clinical activity has been observed in patients with refractory solid tumors. These studies were supported by NCI, UO1, CA062491, SAIC 25XS097, and 1ULRR025011. No significant financial relationships to disclose.