Merrimack Pharmaceuticals, Inc. announced enrollment of its first patient in a Phase 1 dose-escalating clinical study of MM-398 in conjunction with cyclophosphamide for the treatment of pediatric solid tumors. MM-398 is a stable nanoliposomal irinotecan that is designed to exploit leaky tumor vasculature for enhanced drug delivery to tumors. Preclinical research indicates that MM-398 administration results in delivery to the tumor of larger quantities of chemotherapy that are sustained for longer time periods compared with conventional chemotherapy administration.

These effects may be applicable across other types of pediatric solid tumors. The most common forms of pediatric solid tumors include Ewing's sarcoma, rhabdomyosarcoma, neuroblastoma, and osteosarcoma. This Phase 1 study will assess the safety of MM-398 in combination with cyclophosphamide in patients with recurrent or refractory pediatric solid tumors and will seek to determine the recommended Phase 2 dose.

The trial will be sponsored by the South Plains Oncology Consortium and will be executed by participating institutions. Approximately 40 patients from 1 to 21 years old are expected to be enrolled. The first patient was dosed at the University of Texas Southwestern Medical Center.