Phase I study of vorinostat with gefitinib in BIM deletion polymorphism/epidermal growth factor receptor mutation double-positive lung cancer

Abstract

Patients with epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) harboring BIM deletion polymorphism (BIM deletion) have poor responses to EGFR TKI. Mechanistically, the BIM deletion induces preferential splicing of the non-functional exon 3-containing isoform over the functional exon 4-containing isoform, impairing TKI-induced, BIM-dependent apoptosis. Histone deacetylase inhibitor, vorinostat, resensitizes BIM deletion-containing NSCLC cells to EGFR-TKI. In the present study, we determined the safety of vorinostat-gefitinib combination and evaluated pharmacodynamic biomarkers of vorinostat activity. Patients with EGFR-mutated NSCLC with the BIM deletion, pretreated with EGFR-TKI and chemotherapy, were recruited. Vorinostat (200, 300, 400 mg) was given daily on days 1-7, and gefitinib 250 mg was given daily on days 1-14. Vorinostat doses were escalated based on a conventional 3 + 3 design. Pharmacodynamic markers were measured using PBMC collected at baseline and 4 hours after vorinostat dose on day 2 in cycle 1. No dose-limiting toxicities (DLT) were observed in 12 patients. We determined 400 mg vorinostat as the recommended phase II dose (RP2D). Median progression-free survival was 5.2 months (95% CI: 1.4-15.7). Disease control rate at 6 weeks was 83.3% (10/12). Vorinostat preferentially induced BIM mRNA-containing exon 4 over mRNA-containing exon 3, acetylated histone H3 protein, and proapoptotic BIM_EL protein in 11/11, 10/11, and 5/11 patients, respectively. These data indicate that RP2D was 400 mg vorinostat combined with gefitinib in BIM deletion/EGFR mutation double-positive NSCLC. BIM mRNA exon 3/exon 4 ratio in PBMC may be a useful pharmacodynamic marker for treatment.

Keywords: BIM deletion polymorphism; EGFR-TKI; NSCLC; resistance; vorinostat.

Figure 1

Progression‐free survival (PFS) and overall survival (OS) of patients with BIM deletion‐positive epidermal growth factor receptor‐mutated non‐small cell lung cancer treated with gefitinib combined with vorinostat. Kaplan‐Meier curves for PFS (A) and OS (B) of 12 patients are shown. The 95% confidence intervals were calculated by using the Brookmeyer and Crowley method

Figure 2

Pharmacodynamic analysis of vorinostat through transcription of BIM mRNA isoforms in PBMC. A, PBMC were harvested at baseline and 4 h after giving gefitinib and 200 mg (n = 3), 300 mg (n = 3), and 400 mg (n = 5) vorinostat on day 2 of cycle 1. RNA was purified from PBMC and mRNA expression of BIM exon 2A (representative of total BIM mRNA expression), exon 3 (representative of the inactive isoform of BIM mRNA), and exon 4 (representative of the proapoptotic isoform of BIM mRNA) is shown. B, BIM mRNA exon 3/exon 4 ratio. *P < .05 vs baseline. C, Change in BIM mRNA exon 3/exon 4 ratio before and 2 d after treatment with vorinostat and gefitinib. Bars indicate mean ± SD

Figure 3

Pharmacodynamic analysis of vorinostat through protein expression of acetylated histone H3 and pro‐apoptotic BIM_EL in PBMC. PBMC were harvested at baseline (Pre) and 4 h after dose (Post) of gefitinib and 200 mg (A: n = 3), 300 mg (B: n = 3), and 400 mg (C: n = 5) vorinostat on day 2 of cycle 1. Protein expression in PBMC was determined by western blotting