• Phase 0: Presence of Tocilizumab and Metabolites [ Time Frame: Within 4 to 8 hours of administration of tocilizumab ]
  Utilize biopsy and/or drainage to identify the presence of tocilizumab and its metabolites in adamantinomatous craniopharyngioma (ACP) tumor tissue and/or cyst fluid and/or CSF following one dose of systemically administered tocilizumab.
• Feasibility Phase: Toxicity Profile [ Time Frame: Start of study to end of study, up to 5 years ]
  To define toxicities of tocilizumab therapy using CTCAE version 5.

• Phase 0: Presence of Tocilizumab and Metabolites [ Time Frame: Within 4 to 8 hours of administration of tocilizumab ]
  Utilize biopsy and/or drainage to identify the presence of tocilizumab and its metabolites in adamantinomatous craniopharyngioma (ACP) tumor tissue and/or cyst fluid and/or CSF following one dose of systemically administered tocilizumab.
• Feasibility Phase: Overall Response Rate (ORR) [ Time Frame: Start of study to end of study, or up to 5 years ]
  Utilize radiography to estimate the overall response rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: Partial Response Rate (PR) [ Time Frame: Start of study to end of study, or up to 5 years ]
  Utilize radiography to estimate the partial response rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: Complete Response Rate (CR) [ Time Frame: Start of study to end of study, or up to 5 years ]
  Utilize radiography to estimate the complete response rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: 1-Year Disease Stabilization [ Time Frame: Start of study to 1 year post treatment ]
  Utilize radiography to estimate the 1-year disease stabilization rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.

• Phase 0: IL6 and Inflammatory Cytokines [ Time Frame: Within 4 to 8 hours of administration of tocilizumab ]
  To define levels of IL6 and other inflammatory cytokines in biopsied tissue and/or cyst fluid as measured by enzyme-linked immunosorbent assay (ELISA) following 1 dose of systemically administered tocilizumab
• Feasibility Phase: Progression Free Survival (PFS) [ Time Frame: From date of enrollment until the date of first documented progression or date of death from any cause, whichever came first, assessed up to 60 months ]
  Utilize radiography to estimate PFS of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: Pathway Activation [ Time Frame: Start of study to end of study, up to 5 years ]
  To demonstrate evidence of WNT (Wingless-related integration site) in tumor tissue using immunohistochemistry and transcription array
• Feasibility Phase: Pathway Activation [ Time Frame: Start of study to end of study, up to 5 years ]
  To demonstrate evidence of MAPK (mitogen activated protein kinases) in tumor tissue using immunohistochemistry and transcription arr
• Feasibility Phase: Immunity [ Time Frame: Start of study to end of study, up to 5 years ]
  To demonstrate immune cell infiltration in tumor tissue using immunohistochemistry and flow cytometry
• Feasibility Phase: Cytokines [ Time Frame: Start of study to end of study, up to 5 years ]
  To characterize cytokine signaling in tumor tissue and/or cyst fluid using enzyme-linked immunosorbent assay (ELISA)To characterize cytokine signaling in tumor tissue and/or cyst fluid using enzyme-linked immunosorbent assay (ELISA)
• Feasibility Phase: Overall Response Rate (ORR) [ Time Frame: Start of study to end of study, or up to 5 years ]
  Utilize radiography to estimate the overall response rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: 1-Year Disease Stabilization [ Time Frame: Start of study to 1 year post treatment ]
  Utilize radiography to estimate the 1-year disease stabilization rate of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.

• Phase 0: IL6 and Inflammatory Cytokines [ Time Frame: Within 4 to 8 hours of administration of tocilizumab ]
  To define levels of IL6 and other inflammatory cytokines in biopsied tissue and/or cyst fluid as measured by enzyme-linked immunosorbent assay (ELISA) following 1 dose of systemically administered tocilizumab
• Feasibility Phase: Progression Free Survival (PFS) [ Time Frame: From date of enrollment until the date of first documented progression or date of death from any cause, whichever came first, assessed up to 60 months ]
  Utilize radiography to estimate PFS of subjects with newly diagnosed, unresectable or recurrent/progressive ACP (with or without prior radiation therapy) treated with systemic tocilizumab.
• Feasibility Phase: Toxicity Profile [ Time Frame: Start of study to end of study, up to 5 years ]
  To define toxicities of tocilizumab therapy using CTCAE version 5.
• Feasibility Phase: Pathway Activation [ Time Frame: Start of study to end of study, up to 5 years ]
  To characterize evidence of WNT (Wingless-related integration site) in tumor tissue using immunohistochemistry and transcription array
• Feasibility Phase: Pathway Activation [ Time Frame: Start of study to end of study, up to 5 years ]
  To characterize evidence of MAPK (mitogen activated protein kinases) in tumor tissue using immunohistochemistry and transcription arr
• Feasibility Phase: Immunity [ Time Frame: Start of study to end of study, up to 5 years ]
  To characterize immune cell infiltration in tumor tissue using immunohistochemistry and flow cytometry
• Feasibility Phase: Cytokines [ Time Frame: Start of study to end of study, up to 5 years ]
  To characterize cytokine signaling in tumor tissue and/or cyst fluid using enzyme-linked immunosorbent assay (ELISA)To characterize cytokine signaling in tumor tissue and/or cyst fluid using enzyme-linked immunosorbent assay (ELISA)

• Experimental: Tocilizumab Administration: Phase 0
  In Phase 0, patients will receive one dose of tocilizumab prior to surgery.
  Intervention: Drug: Tocilizumab
• Experimental: Tocilizumab Administration: Feasibility Phase
  During the Feasibility Phase, patients will receive tocilizumab every 2 weeks for up to 13 cycles (approximately 1 year). Patients will be followed for up to 5 years.
  Intervention: Drug: Tocilizumab

Inclusion Criteria

Phase 0 Eligibility:

1. Tumor biopsy/resection and/or cyst aspiration planned for the clinical care of the patient independent of study participation by the treating pediatric neurosurgeon and neuro-oncologist

2. Must meet one of the following criteria:

   1. Presumed craniopharyngioma based on imaging features and best judgement of treating medical team (if newly diagnosed)
   2. Previous histologically confirmed ACP that has progressed or recurred at the time of enrollment

Feasibility Eligibility:

1. Must meet one of the following criteria:

   1. Recurrent or progressive* ACP treated with surgery alone without radiation

   2. Recurrent or progressive* ACP treated with surgery and radiation

      * Progressive disease for eligibility purposes will be defined as follows: Solid disease: any growth deemed progression based on discretion of the investigator regardless of timing from RT Cystic disease: must be at least 6 months from last day of RT. Patients demonstrating isolated cyst growth >6 months after RT must show a continued increase in the cystic component on two serial MRI scans performed at least 4 weeks apart OR at least partial reaccumulation of the cyst following one or more cyst aspirations.

   3. Newly diagnosed, by histology or imaging ACP with unresectable residual cystic and/or solid disease that is measurable in 2 dimensions
2. Subjects who participated in the Phase 0 portion and meet eligibility, may enroll in the Feasibility Phase of the study once open.

Overall Study Inclusion Criteria:

1. Age: ≥ 2 years and < 21 years
2. Subjects may have received prior tocilizumab or other IL6 or IL6R inhibitor

3. Organ Function Requirements

   1. Adequate bone marrow function defined as:

      • Platelet count ≥100,000/μl (transfusion independent)
      • Absolute neutrophil count (ANC) ≥1500/μl

   2. Adequate renal function defined as:

      • Creatinine clearance or radioisotope GFR ≥70 ml/min/1.73 m2 or
      • A serum creatinine based on age/gender as follows: (Age, Male, Female) 3 to < 6 years, 0.8, 0.8; 6 to < 10 years, 1, 1; 10 to < 13 years, 1.2, 1.2; 13 to < 16 years, 1.5, 1.4; 16 years to < 18 years, 1.7, 1.4

   3. Adequate liver function defined as:

      • SGOT (AST) and SGPT (ALT) <1.5x ULN for age

4. Subjects must meet one of the following performance scores:

   1. ECOG performance status scores of 0, 1, or 2;
   2. Karnofsky score of ≥60 for patients > 16 years of age; or
   3. Lansky score of ≥60 for patients ≤16 years of age
5. Subjects of childbearing or child fathering potential must be willing to use a medically acceptable form of birth control, which includes abstinence, while being treated on this study.
6. Informed consent and assent obtained as appropriate.

Exclusion Criteria

1. Pregnant or breastfeeding

2. Uncontrolled intercurrent illness including, but not limited to:

   1. ongoing or active infection (including active tuberculosis)
   2. symptomatic congestive heart failure
   3. unstable angina pectoris
   4. cardiac arrhythmia
   5. psychiatric illness/social situations that would limit compliance with study requirements are not eligible.
3. Known hypersensitivity or history of anaphylaxis to tocilizumab
4. Received any live vaccinations within 3 months prior to start of therapy
5. Evidence of metastatic disease or other cancer
6. Inability to return for follow up visits or obtain required follow-up studies to assess toxicity of therapy