Phase I pharmacokinetic and pharmacodynamic study of the first-in-class spliceosome inhibitor E7107 in patients with advanced solid tumors

To assess the safety, tolerability, pharmacokinetics, pharmacodynamics, and clinical activity of E7107 administered as 5-minute bolus infusions on days 1, 8, and 15 in a 28-day schedule.

Patients with solid tumors refractory to standard therapies or with no standard treatment available were enrolled. Dose levels of 0.6 to 4.5 mg/m(2) were explored.

Forty patients [24M/16F, median age 61 years (45-79)] were enrolled. At 4.5 mg/m(2), dose-limiting toxicity (DLT) consisted of grade 3 diarrhea, nausea, and vomiting and grade 4 diarrhea, respectively, in two patients. At 4.0 mg/m(2), DLT (grade 3 nausea, vomiting, and abdominal cramps) was observed in one patient. Frequently occurring side effects were mainly gastrointestinal. After drug discontinuation at 4.0 mg/m(2), one patient experienced reversible grade 4 blurred vision. The maximum tolerated dose (MTD) is 4.0 mg/m(2). No complete or partial responses during treatment were observed; one patient at 4.0 mg/m(2) had a confirmed partial response after drug discontinuation. Pharmacokinetic analysis revealed a large volume of distribution, high systemic clearance, and a plasma elimination half-life of 5.3 to 15.1 hours. Overall drug exposure increased in a dose-dependent manner. At the MTD, mRNA levels of selected target genes monitored in peripheral blood mononuclear cells showed a reversible 15- to 25-fold decrease, whereas unspliced pre-mRNA levels of DNAJB1 and EIF4A1 showed a reversible 10- to 25-fold increase.

The MTD for E7107 using this schedule is 4.0 mg/m(2). Pharmacokinetics is dose-dependent and reproducible within patients. Pharmacodynamic analysis revealed dose-dependent reversible inhibition of pre-mRNA processing of target genes, confirming proof-of-principle activity of E7107.