Pediatric Oncology Clinical Trials


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One of the greatest strengths of UW Health American Family Children's Hospital is our involvement in groundbreaking clinical trials conducted by the University of Wisconsin Carbone Cancer Center in Madison, WI. This work helps answer specific questions about new ways to prevent, diagnose, detect and treat cancer.


CLR 131 Clinical Trial


CLR 131 is a targeted radiotherapy to treat pediatric and adolescent patients who have solid cancers, lymphomas and malignant brain tumors. Hear from Dr. Mario Otto, co-principal investigator:




CLR 131 takes advantage of the specific makeup of the cancer cell membrane. CLR 131 enters cells through so-called lipid rafts, important signaling islands that are freely floating in every cell. However, the expression of lipid rafts is up to 20 fold higher in cancer cells than in normal, healthy cells, allowing for the preferred entry of the drug into cancer cells. In the cells, the drug is rapidly incorporated into cellular membranes, as it is a synthetic analog of naturally occurring building blocks (phospholipids) that make up all cell membranes. In addition, cancer cells have a relative deficiency of enzymes that digest and eliminate these particular phospholipid analogs, which ultimately leads to prolonged retention of the drug in cancer cells. The radioactive payload of the small molecule drug is iodine-131, a well-established anti-cancer radionuclide.

CLR 131 has shown activity in several clinical trials of adult hematologic malignancies and in pre-clinical studies has demonstrated efficacy in a wide range of pediatric tumors.

Pre-clinical studies completed by co-principal investigator Dr. Mario Otto, Associate Professor in the Division of Pediatric Hematology, Oncology and Bone Marrow Transplant at the University of Wisconsin, demonstrated significant anti-cancer effects in pre-clinical models of neuroblastoma, Ewing sarcoma, rhabdomyosarcoma and osteosarcoma. A single dose of CLR 131 resulted in better survival and slower growing tumors than seen in untreated mice (J Nucl Med. 2018 Feb;59(2):244-250). This, and the fact that the radiopharmaceutical is already been tested in adults, provided the rationale for the development of a phase I trial. “The current clinical trial is for children and adolescents ≥ 2 years and ≤ 21 years of age with relapsed/refractory solid tumors and brain cancers who have not responded to standard treatment and there are no options that would have a reasonable chance for cure” said Otto. Some other key eligibility criteria include a performance status ≥ 60, ability to collect an autologous stem cell backup product prior to CLR 131 administration, and measurable disease (≥ 15 mm for extracranial tumors, ≥ 10 mm for CNS tumors). Other eligibility and exclusion criteria exist. “If successful, CLR 131 could provide a beneficial treatment option for these children and their families.” The FDA has granted CLR 131 orphan drug status and rare pediatric disease designations for four separate pediatric cancer indications.


The primary aims of this open label, dose escalation study are to determine the safety and tolerability of single-dose CLR 131 in children and adolescents with relapsed or refractory malignant solid tumors and lymphoma (Cohort 1) and recurrent or refractory malignant brain tumors (Cohort 2) for which there are no standard treatment options with curative potential. Secondary aims are 1) to identify the recommended Phase 2 dose of CLR 131 in children and adolescents in the two Cohorts, 2) to determine therapeutic activity (via SPECT/CT) and preliminary antitumor activity (treatment response) and 4) to determine dosimetry of CLR 131 in children and adolescents in the two Cohorts. Up to 31 patients per cohort will be enrolled.

The trial, conducted in collaboration with Cellectar Biosciences, Inc., (Madison, WI) will be initially available only at UW Health American Family Children’s Hospital in Madison, WI.