Phase I study of TLK286 (glutathione S-transferase P1-1 activated glutathione analogue) in advanced refractory solid malignancies.

The purpose of this study was to determine the dose-limiting toxicities (DLTs), the maximum tolerated dose, and the pharmacokinetics of the novel glutathione analog TLK286 administered by i.v. infusion.Patients with advanced malignancies received i.v. TLK286 administered as a 30-min constant rate infusion once every 3 weeks in escalating doses from 60 to 1280 mg/m(2). Patients underwent tumor assessment on day 43 and continued on treatment until disease progression or unacceptable toxicity.A total of 35 patients were treated with 109 cycles of TLK286. At 1280 mg/m(2), 3 of 5 patients developed one of two observed dose limiting toxicities (DLTs). The DLTs were: mild pancreatitis (1 of 5) and bladder symptoms (2 of 5) consisting of hematuria, dysuria, and urinary frequency. All of the patients with DLTs continued on TLK286 treatment at 960 mg/m(2) (one dose below maximum tolerated dose) without recurrence of DLTs. DLTs were transient, resolved without sequelae, and noncumulative. TLK286-related toxicities included grade 1-2 nausea, vomiting, fatigue, transient microscopic hematuria, and anemia. Of 31 evaluable patients, 10 patients continued therapy (median six cycles; range, four to nine cycles). Pharmacokinetic studies of TLK286 on cycle 1 revealed a mean elimination half-life of 18 min (95% confidence interval, 16.1-19.9). Dose-proportional increases in both maximum blood concentrations and area under the blood-concentration-time curve were observed over the dose range of 60-960 mg/m(2).TLK286 was well tolerated in this study. TLK286 safety and pharmacokinetics support disease-specific evaluations of TLK286 at doses <1280 mg/m(2) administered once every three weeks in the treatment of patients with advanced malignancies.