A phase I, pharmacokinetic, and pharmacodynamic study of panobinostat, an HDAC inhibitor, combined with erlotinib in patients with advanced aerodigestive tract tumors.

Purpose: Panobinostat, a histone deacetylase (HDAC) inhibitor, enhances antiproliferative activity in non-small cell lung cancer (NSCLC) cell lines when combined with erlotinib. We evaluated this combination in patients with advanced NSCLC and head and neck cancer.

Experimental Design: Eligible patients were enrolled in a 3+3 dose-escalation design to determine the maximum tolerated dose (MTD) of twice weekly panobinostat plus daily erlotinib at four planned dose levels (DL). Pharmacokinetics, blood, fat pad biopsies (FPB) for histone acetylation, and paired pre and posttherapy tumor biopsies for checkpoint kinase 1 (CHK1) expression were assessed.

Results: Of 42 enrolled patients, 33 were evaluable for efficacy. Dose-limiting toxicities were prolonged-QTc and nausea at DL3. Adverse events included fatigue and nausea (grades 1-3), and rash and anorexia (grades 1-2). Disease control rates were 54% for NSCLC (n = 26) and 43% for head and neck cancer (n = 7). Of 7 patients with NSCLC with EGF receptor (EGFR) mutations, 3 had partial response, 3 had stable disease, and 1 progressed. For EGFR-mutant versus EGFR wild-type patients, progression-free survival (PFS) was 4.7 versus 1.9 months (P = 0.43) and overall survival was 41 (estimated) versus 5.2 months (P = 0.39). Erlotinib pharmacokinetics was not significantly affected. Correlative studies confirmed panobinostat's pharmacodynamic effect in blood, FPB, and tumor samples. Low CHK1 expression levels correlated with PFS (P = 0.006) and response (P = 0.02).

Conclusions: We determined MTD at 30 mg (panobinostat) and 100 mg (erlotinib). Further studies are needed to further explore the benefits of HDAC inhibitors in patients with EGFR-mutant NSCLC, investigate FPB as a potential surrogate source for biomarker investigations, and validate CHK1's predictive role.