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.