Introduction: This phase I study evaluated the safety, tolerability, preliminary antitumor activity, and pharmacokinetic interaction of weekly topotecan (days 1 and 8) in combination with pemetrexed (day 1 only) in patients with advanced solid tumors.
Methods: Patients received topotecan (3.0-4.0 mg/m(2) i.v. days 1 and 8) and pemetrexed (375-500 mg/m(2) i.v. day 1) over 21-day cycles. Patients were accrued across five different dose levels and were observed for safety, tolerability, and preliminary activity.
Results: Twenty-six patients received 120 cycles of pemetrexed and topotecan, including five patients who received 8, 8, 10, 12, and 17 cycles without dose reductions, confirming a lack of cumulative myelosuppression. Four patients received topotecan (4.0 mg/m(2) i.v.) and pemetrexed (500 mg/m(2) i.v.), but experienced two dose-limiting toxicities (febrile neutropenia, grade 4 thrombocytopenia). As a result, the topotecan (3.5 mg/m(2) i.v.) and pemetrexed (500 mg/m(2) i.v.) group was expanded to 12 patients. The only grade 3 or 4 nonhematologic toxicity was one episode of grade 3 fatigue; no grade 3 or 4 nausea/vomiting/diarrhea, mucositis, or rash was reported. One non-small cell lung cancer (NSCLC) patient (12 months) and one soft tissue sarcoma patient (6 months) achieved a partial response.
Conclusions: Weekly topotecan plus every-3-week pemetrexed was well tolerated and active. Full doses of topotecan plus pemetrexed caused brief reversible myelosuppression with minimal dose delays/reductions; no grade 3 or 4 nausea/vomiting/diarrhea, mucositis, or rash was reported. All six NSCLC patients at the recommended phase II dose had at least stable disease as a best response, including one partial response lasting 12 months. There was no evidence of an effect of pemetrexed on topotecan pharmacokinetics. Collectively, these data suggest that further phase II exploration of weekly topotecan plus every-3-week pemetrexed for advanced malignancies is indicated.