General Inclusion Criteria:

          -  Age at treatment 1 to 35 years.

          -  Relapsed or refractory malignant solid tumors of any histology for which no standard
             curative therapy is available (escalation phase).

          -  Histologically proven: neuroblastoma, rhabdomyosarcoma, osteosarcoma, Ewing's sarcoma/
             primitive neuroectodermal tumor, Wilms tumor, desmoplastic small round cell tumor or
             malignant solid tumors of any other histology that test positive for B7-H3 .

          -  Must have malignant solid tumors that demonstrate B7-H3 expression at 2+ or greater
             levels on the membranous surface of at least 10% of tumor cells or ≥ 25% of tumor
             vasculature by IHC.

          -  With the exception of patients with non-measurable neuroblastoma patients must have
             measurable disease as per RECIST 1.1

          -  Karnofsky (patients ≥ 16 years)/Lansky (patients < 16 years) index ≥ 70.

          -  Acceptable laboratory parameters and adequate organ reserve.

        Exclusion Criteria:

          -  Patients are to be excluded from the study if they have any of the following:

          -  Patients with a history of symptomatic central nervous system (CNS) unless they have
             been treated and are asymptomatic.

          -  Patients with any history of known or suspected autoimmune disease with the specific
             exceptions of vitiligo, resolved childhood atopic dermatitis, psoriasis not requiring
             systemic treatment within the past 2 years, and patients with a history of Grave's
             disease that are now euthyroid clinically and by laboratory testing.

          -  History of prior allogeneic bone marrow/stem-cell or solid organ transplantation.

          -  Patients receiving autologous stem cell transplantation must wait 8 weeks before
             initiation of study drug administration.

          -  Treatment with systemic chemotherapy or investigational therapy within 4 weeks of
             first study drug administration; other agents (e.g., biologics) within 2 weeks;
             radiation within 2 weeks; patients receiving 131I-MIBG therapy must wait 6 weeks prior
             to the initiation of study drug administration; corticosteroids (≥ 0.2 mg/kg/day
             prednisone or equivalent) or other immune suppressive drugs within the 2 weeks prior
             to the initiation of study drug administration.

          -  History of clinically significant cardiovascular disease

          -  Active viral, bacterial, or systemic fungal infection requiring parenteral treatment
             within 7 days prior to the initiation of study drug.

          -  Known positive testing for human immunodeficiency virus or history of acquired immune
             deficiency syndrome.

          -  Known history of hepatitis B or hepatitis C infection or known positive test for
             hepatitis B surface antigen, hepatitis B core antigen, or hepatitis C polymerase chain
             reaction.

          -  Second primary invasive malignancy that has not been in remission for greater than 2
             years.

          -  History of severe trauma or major surgery within 4 weeks prior to the initiation of
             study drug administration.

          -  Known hypersensitivity to recombinant proteins, polysorbate 80 or any excipient
             contained in the drug formulation for enoblituzumab

          -  Patients in Canada may not have a history or evidence of latent or active tuberculosis
             infection.