Pepinemab in Treating Younger Patients With Recurrent, Relapsed, or Refractory Solid Tumors

PRIMARY OBJECTIVES: I. To estimate the maximum tolerated dose (MTD) and/or recommended phase 2 dose of pepinemab (VX15/2503) administered as an intravenous infusion every 14 days to children with recurrent or refractory solid tumors. (Part A) II. To define and describe the toxicities of VX15/2503 administered on this schedule. (Parts A-B) III. To characterize the pharmacokinetics of VX15/2503 in children with recurrent or refractory cancer. (Parts A-B) IV. To preliminarily define the antitumor activity of VX15/2503 for the treatment of relapsed or refractory osteosarcoma. (Part B) V. To determine if VX15/2503 either improves the disease control rate at 4 months in patients with recurrent measurable osteosarcoma or produces an objective response rate in patients with relapsed or refractory osteosarcoma. (Part B) SECONDARY OBJECTIVES: I. To assess the pharmacodynamics of VX15/2503 through VX15/2503 saturation of T-lymphocytes. II. To assess the immunogenicity of VX15/2503 in pediatric patients with recurrent or refractory cancer. EXPLORATORY OBJECTIVES: I. To evaluate potential biomarkers of VX15/2503 sensitivity including SEMA4D, PlexinB1, and other markers of immune cell infiltration in archival tumor tissues. OUTLINE: This is a phase I, dose-escalation study followed by a phase II study. Patients receive pepinemab intravenously (IV) over 60 minutes on days 1 and 15. Treatment repeats every 28 days for 13 cycles in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up periodically.