Clinical Research Papers:
Phase 1 study of sirolimus in combination with oral cyclophosphamide and topotecan in children and young adults with relapsed and refractory solid tumors
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Kieuhoa T. Vo1, Erin E. Karski1, Nicole M. Nasholm1, Shelly Allen1, Fabienne Hollinger1, W. Clay Gustafson1, Janel R. Long-Boyle2, Stephen Shiboski3, Katherine K. Matthay1 and Steven G. DuBois1
1 Department of Pediatrics, UCSF Benioff Children’s Hospital, University of California, San Francisco School of Medicine, San Francisco, CA, USA
2 Department of Clinical Pharmacy, UCSF Benioff Children’s Hospital, University of California, San Francisco School of Medicine, San Francisco, CA, USA
3 Department of Epidemiology and Biostatistics, UCSF Benioff Children’s Hospital, University of California, San Francisco School of Medicine, San Francisco, CA, USA
Kieuhoa T. Vo, email:
Keywords: phase 1, mTOR, sirolimus, topotecan, cyclophosphamide
Received: August 23, 2016 Accepted: October 13, 2016 Published: October 25, 2016
Purpose: To determine the maximum tolerated dose (MTD), toxicities, and pharmacodynamics effects of sirolimus combined with oral metronomic topotecan and cyclophosphamide in a pediatric population.
Materials and Methods: Patients who were 1 to 30 years of age with relapsed/refractory solid tumors (including CNS) were eligible. Patients received daily oral sirolimus and cyclophosphamide (25-50 mg/m2/dose) on days 1-21 and oral topotecan (0.8 mg/m2/dose) on days 1-14 in 28-day cycles. Sirolimus steady-state plasma trough concentrations of 3-7.9 ng/mL and 8-12.0 ng/mL were evaluated, with dose escalation based on a 3+3 phase 1 design. Biomarkers of angiogenesis were also evaluated.
Results: Twenty-one patients were treated (median age 18 years; range 9-30). Dose-limiting toxicities included myelosuppression, ALT elevation, stomatitis, and hypertriglyceridemia. The MTD was sirolimus with trough goal of 8-12.0 ng/mL; cyclophosphamide 25 mg/m2/dose; and topotecan 0.8 mg/m2/dose. No objective responses were observed. Four patients had prolonged stable disease > 4 cycles (range 4-12). Correlative biomarker analyses demonstrated reductions in thrombospondin-1 (p=0.043) and soluble vascular endothelial growth factor receptor-2 plasma concentrations at 21 days compared to baseline.
Conclusions: The combination of oral sirolimus, topotecan, and cyclophosphamide was well tolerated and biomarker studies demonstrated modulation of angiogenic pathways with this regimen.
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