A phase 1 study of TRC102, an inhibitor of base excision repair, and pemetrexed in patients with advanced solid tumors

Abstract

Introduction: TRC102 potentiates the activity of cancer therapies that induce base excision repair (BER) including antimetabolite and alkylating agents. TRC102 rapidly and covalently binds to apurinic/apyrimidinic (AP) sites generated during BER, and TRC102-bound DNA causes topoisomerase II-dependent irreversible strand breaks and apoptosis. This study assessed the safety, maximum-tolerated dose (MTD), pharmacokinetics and pharmacodynamics of TRC102 alone and in combination with pemetrexed.

Purpose: Patients with advanced solid tumors received oral TRC102 daily for 4 days. Two weeks later, patients began standard-dose pemetrexed on day 1 in combination with oral TRC102 on days 1 to 4. The pemetrexed-TRC102 combination was repeated every 3 weeks until disease progression.

Methods: Twenty-eight patients were treated with TRC102 at 15, 30, 60 or 100 mg/m(2)/d. The MTD was exceeded at 100 mg/m(2)/d due to grade 3 anemia in 50 % of patients. TRC102 exposure increased in proportion to dose with a mean t1/2 of 28 h. A pharmacodynamic assay confirmed that TRC102 binds to pemetrexed-induced AP sites at all doses studied. Stable disease or better was achieved in 15 of 25 patients evaluable for response (60 %), including one patient with recurrent metastatic oropharyngeal carcinoma that expressed high levels of thymidylate synthase, who achieved a partial response and was progression free for 14 months.

Conclusions: When administered with pemetrexed, the maximum tolerated dose of oral TRC102 is 60 mg/m(2)/d for 4 days. Randomized controlled studies are planned to evaluate the clinical benefit of adding TRC102 to pemetrexed and other agents that induce BER.

Trial registration: ClinicalTrials.gov NCT00692159.

Figures

Fig. 1

Relationship between dose of TRC102 and median AUC∞ for nineteen patients treated on C1D1. The exposure of TRC102 was proportional to dose across the range of 15 to 100 mg/m2/d

Fig. 2

Representative pharmacodynamic data from a patient treated with pemetrexed plus 60 mg/m2/d TRC102. AP sites in peripheral blood mononuclear cells were detected using a fluorescent aldehyde-reactive probe, and results were expressed relative to pre-dose. The number of AP sites increased after dosing with pemetrexed alone (cycle 3 day 1) but not after dosing with pemetrexed and TRC102 (cycle 2 day 1). These findings are consistent with binding of TRC102 to pemetrexed-induced AP sites