• Patient must have enrolled onto APEC1621SC and must have been given a treatment assignment to Molecular Analysis for Therapy Choice (MATCH) to APEC1621F based on the presence of an actionable mutation
• Patients must be >= than 12 months and =< 21 years of age at the time of study enrollment.
• Patients must have a body surface area >= 0.5 m^2 at enrollment
• Patients must have radiographically measurable disease at the time of study enrollment. Patients with neuroblastoma who do not have measurable disease but have iobenguane (MIBG) positive (+) evaluable disease are eligible; measurable disease in patients with CNS involvement is defined as any lesion that is at minimum 10 mm in one dimension on a standard MRI or CT
• Note: The following do not qualify as measurable disease:
• Malignant fluid collections (e.g., ascites, pleural effusions)
• Bone marrow infiltration except that detected by MIBG scan for neuroblastoma
• Lesions only detected by nuclear medicine studies (e.g., bone, gallium or positron emission tomography [PET] scans) except as noted for neuroblastoma
• Elevated tumor markers in plasma or cerebrospinal fluid (CSF)
• Previously radiated lesions that have not demonstrated clear progression post radiation
• Leptomeningeal lesions that do not meet the measurement requirements for Response Evaluation Criteria in Solid Tumors (RECIST) 1.1
• Karnofsky >= 50% for patients > 16 years of age and Lansky >= 50 for patients =< 16 years of age
• Note: Neurologic deficits in patients with CNS tumors must have been relatively stable for at least 7 days prior to study enrollment; patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score
• Patients must have fully recovered from the acute toxic effects of all prior anti-cancer therapy and must meet the following minimum duration from prior anti-cancer directed therapy prior to enrollment; if after the required timeframe, the numerical eligibility criteria are met, e.g. blood count criteria, the patient is considered to have recovered adequately
• Cytotoxic chemotherapy or other anti-cancer agents known to be myelosuppressive: >= 21 days after the last dose of cytotoxic or myelosuppressive chemotherapy (42 days if prior nitrosourea)
• Anti-cancer agents not known to be myelosuppressive (e.g. not associated with reduced platelet or absolute neutrophil counts [ANC] counts): >= 7 days after the last dose of agent
• Antibodies: >= 21 days must have elapsed from infusion of last dose of antibody, and toxicity related to prior antibody therapy must be recovered to grade =< 1
• Corticosteroids: if used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid
• Hematopoietic growth factors: >= 14 days after the last dose of a long-acting growth factor (e.g. pegfilgrastim) or 7 days for short-acting growth factor; for growth factors that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur; the duration of this interval must be discussed with the study chair and the study-assigned research coordinator
• Interleukins, interferons and cytokines (other than hematopoietic growth factors): >= 21 days after the completion of interleukins, interferon or cytokines (other than hematopoietic growth factors)
• Stem cell Infusions (with or without total body irradiation [TBI]):
• Allogeneic (non-autologous) bone marrow or stem cell transplant, or any stem cell infusion including donor lymphocyte infusion (DLI) or boost infusion: >= 84 days after infusion and no evidence of graft versus host disease (GVHD)
• Autologous stem cell infusion including boost infusion: >= 42 days
• Cellular therapy: >= 42 days after the completion of any type of cellular therapy (e.g. modified T cells, natural killer [NK] cells, dendritic cells, etc.)
• Radiation therapy (XRT)/external beam irradiation including protons: >= 14 days after local XRT; >= 150 days after TBI, craniospinal XRT or if radiation to >= 50% of the pelvis; >= 42 days if other substantial none marrow (BM) radiation
• Note: Radiation may not be delivered to "measurable disease" tumor site(s) being used to follow response to subprotocol treatment
• Radiopharmaceutical therapy (e.g., radiolabeled antibody, 131I-MIBG): >= 42 days after systemically administered radiopharmaceutical therapy
• Patients must not have received prior exposure to ensartinib; prior treatment with other ALK inhibitors is permitted given that at least 5 half-lives or 21 days have elapsed since therapy discontinuation, whichever is greater
• For patients with solid tumors without known bone marrow involvement:
• Peripheral absolute neutrophil count (ANC) >= 1000/mm^3 (within 7 days prior to enrollment)
• Platelet count >= 100,000/mm^3 (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment) (within 7 days prior to enrollment)
• Patients with known bone marrow metastatic disease will be eligible for study provided they meet the blood counts (may receive transfusions provided they are not known to be refractory to red cell or platelet transfusions); these patients will not be evaluable for hematologic toxicity
• Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 ml/min/1.73 m^2 (within 7 days prior to enrollment) or a serum creatinine based on age/gender as follows (within 7 days prior to enrollment):
• Age 1 to < 2 years: maximum serum creatinine 0.6 mg/dL for male and 0.6 mg/dL for female
• Age 2 to < 6 years: maximum serum creatinine 0.8 mg/dL for male and 0.8 mg/dL for female
• Age 6 to < 10 years: maximum serum creatinine 1 mg/dL for male and 1 mg/dL for female
• Age 10 to < 13 years: maximum serum creatinine 1.2 mg/dL for male and 1.2 mg/dL for female
• Age 13 to < 16 years: maximum serum creatinine 1.5 mg/dL for male and 1.4 mg/dL for female
• Age >= 16 years: maximum serum creatinine 1.7 mg/dL for male and 1.4 mg/dL for female
• Bilirubin (sum of conjugated + unconjugated) =< 1.5 x upper limit of normal (ULN) for age (within 7 days prior to enrollment)
• Serum glutamic pyruvic transaminase (SGPT) (alanine aminotransferase [ALT]) =< 135 U/L (within 7 days prior to enrollment) (for the purpose of this study, the ULN for SGPT is 45 U/L)
• Serum albumin >= 2 g/dL (within 7 days prior to enrollment)
• Patients must be able to swallow intact capsules
• All patients and/or their parents or legally authorized representatives must sign a written informed consent; assent, when appropriate, will be obtained according to institutional guidelines
• Pregnant or breast-feeding women will not be entered on this study because there is currently no available information regarding human fetal or teratogenic toxicities; pregnancy tests must be obtained in girls who are post-menarchal; males or females of reproductive potential may not participate unless they have agreed to use an effective contraceptive method for the duration of study treatment and for one week after the last dose of ensartinib
• Concomitant medications
• Corticosteroids: patients receiving corticosteroids who have not been on a stable or decreasing dose of corticosteroid for at least 7 days prior to enrollment are not eligible; if used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid
• Investigational drugs: patients who are currently receiving another investigational drug are not eligible
• Anti-cancer agents: patients who are currently receiving other anti-cancer agents are not eligible
• Anti-GVHD agents post-transplant: patients who are receiving cyclosporine, tacrolimus or other agents to prevent graft-versus-host disease post bone marrow transplant are not eligible for this trial
• CYP3A4 agents: patients who are currently receiving drugs that are strong inducers or strong inhibitors of CYP3A4 are not eligible; strong inducers or inhibitors of CYP3A4 should be avoided from 14 days prior to enrollment to the end of the study
• Note: CYP3A4 inducing anti-epileptic drugs and dexamethasone for CNS tumors or metastases, on a stable dose, are allowed
• Patients who have an uncontrolled infection are not eligible
• Patients who have received a prior solid organ transplantation are not eligible
• Patients who in the opinion of the investigator may not be able to comply with the safety monitoring requirements of the study are not eligible

• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Patients must be >= 12 months and =< 21 years of age at the time of study enrollment
• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Patients with recurrent or refractory solid tumors, including non-Hodgkin lymphomas, histiocytoses (e.g. langerhans cell histiocytosis [LCH], juvenile xanthogranuloma [JXG], histiocytic sarcoma), and central nervous system (CNS) tumors are eligible; patients must have had histologic verification of malignancy at original diagnosis or relapse except in patients with intrinsic brain stem tumors, optic pathway gliomas, or patients with pineal tumors and elevations of cerebrospinal fluid (CSF) or serum tumor markers including alpha-fetoprotein or beta-human chorionic gonadotropin (HCG); in cases where patient enrolls prior to histologic confirmation of recurrent disease, patient is ineligible and should be withdrawn from study if histology fails to confirm recurrence; please note: Patients with Hodgkin lymphoma and plexiform neurofibroma are not eligible
• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Tumor Testing Requirement: Tumor sample availability requirement for stage 1 of Pediatric MATCH (patients enrolled from start of study in July 2017 through 12/31/21); Patients must have an formalin-fixed paraffin-embedded (FFPE) tumor sample available for MATCH study testing from a biopsy or surgery that was performed at any point after initial tumor recurrence/progression, or be planned to have a procedure to obtain such a sample that is considered to be of potential benefit by the treating clinicians; a tumor sample from a clinically performed diagnostic (pre-treatment) biopsy will be acceptable for enrollment onto Pediatric MATCH only for children with high-grade gliomas of the brainstem (diffuse intrinsic pontine gliomas) or thalamus
• Please note: Samples that have been decalcified using standardly utilized acid-based decalcification methods are not generally suitable for MATCH study testing; the nucleic acids will have been degraded in the decalcification process
• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Tumor molecular profiling report availability requirement for Stage 2 of Pediatric MATCH (patients enrolled starting 2022): In stage 2 of the study, no tumor samples will be submitted for centralized clinical tumor profiling; instead, a tumor molecular profiling report from a College of American Pathologists (CAP)/ Clinical Laboratory Improvements Amendments (CLIA)-approved testing laboratory must be submitted for review by the Molecular Review Committee (MRC)
• This molecular profiling must have been performed on a tumor sample that was obtained at any point after initial tumor recurrence/progression and must be accompanied by a pathology report for the same tumor specimen; a molecular profiling report for a diagnostic (pre-treatment) tumor sample will be acceptable for enrollment onto Pediatric MATCH only for children with high-grade gliomas of the brainstem (diffuse intrinsic pontine gliomas) or thalamus. In the event that molecular profiling reports are available from multiple timepoints, the most recent report should be prioritized for study submission
• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Karnofsky >= 50% for patients > 16 years of age and Lansky >= 50 for patients =< 16 years of age); note: neurologic deficits in patients with central nervous system (CNS) tumors must have been stable for at least 7 days prior to study enrollment; patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score
• ELIGIBILITY CRITERIA FOR ENROLLMENT ONTO APEC1621SC: Patients must have radiographically measurable disease; measurable disease based on imaging obtained less than or equal to 56 days prior to enrollment; patients with neuroblastoma who do not have measurable disease but have metaiodobenzylguanidine (MIBG) positive (+) evaluable disease are eligible; measurable disease in patients with CNS involvement is defined as any lesion that is at minimum 10 mm in one dimension on standard magnetic resonance imaging (MRI) or computed tomography (CT)
• Note: The following do not qualify as measurable disease:
• Malignant fluid collections (e.g., ascites, pleural effusions)
• Bone marrow infiltration except that detected by MIBG scan for neuroblastoma
• Lesions only detected by nuclear medicine studies (e.g., bone, gallium or positron emission tomography [PET] scans) except as noted for neuroblastoma
• Elevated tumor markers in plasma or CSF
• Previously radiated lesions that have not demonstrated clear progression post radiation
• Leptomeningeal lesions that do not meet the measurement requirements for Response Evaluation Criteria in Solid Tumors (RECIST) 1.1
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: NOTE: patient does not need to meet all subprotocol criteria at time of enrollment onto the APEC1621SC screening protocol, but will need to meet all criteria prior to enrollment on any assigned treatment subprotocol. Patients must be enrolled onto a subprotocol within 2 weeks (14 days) of treatment assignment
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Karnofsky >= 50% for patients > 16 years of age and Lansky >= 50 for patients =< 16 years of age); Note: neurologic deficits in patients with CNS tumors must have been stable for at least 7 days prior to study enrollment; patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: At the time of treatment with subprotocol specified therapy, the patients must have radiographically measurable disease; patients with neuroblastoma who do not have measurable disease but have MIBG+ evaluable are eligible; measurable disease in patients with CNS involvement is defined as any lesion that is at minimum 10 mm in one dimension on standard MRI or CT
• Note: The following do not qualify as measurable disease:
• Malignant fluid collections (e.g., ascites, pleural effusions)
• Bone marrow infiltration except that detected by MIBG scan for neuroblastoma
• Lesions only detected by nuclear medicine studies (e.g., bone, gallium or positron emission tomography [PET] scans) except as noted for neuroblastoma
• Elevated tumor markers in plasma or CSF
• Previously radiated lesions that have not demonstrated clear progression post radiation
• Leptomeningeal lesions that do not meet the measurement requirements for RECIST 1.1
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: At the time of enrollment onto a subprotocol, the following general criteria for initiation of therapy will be required:
• Patients must have fully recovered from the acute toxic effects of all prior anticancer therapy and must meet the following minimum duration from prior anticancer directed therapy prior to enrollment to the subprotocol; if after the required timeframe, the numerical eligibility criteria are met, e.g. blood count criteria, the patient is considered to have recovered adequately
• Cytotoxic chemotherapy or other anticancer agents known to be myelosuppressive: for agents not listed, the duration of this interval must be discussed with the study chair and the study-assigned research coordinator prior to enrollment >= 21 days after the last dose of cytotoxic or myelosuppressive chemotherapy (42 days if prior nitrosourea)
• Anticancer agents not known to be myelosuppressive (e.g. not associated with reduced platelet or absolute neutrophil counts [ANC]): >= 7 days after the last dose of agent; for agents not listed, the duration of this interval must be discussed with the study chair and the study-assigned research coordinator prior to enrollment
• Antibodies: >= 21 days must have elapsed from infusion of last dose of antibody, and toxicity related to prior antibody therapy must be recovered to grade =< 1
• Corticosteroids: If used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid
• Hematopoietic growth factors: >= 14 days after the last dose of a long-acting growth factor (e.g. Neulasta) or 7 days for short-acting growth factor; for agents that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur; the duration of this interval must be discussed with the study chair and the study-assigned research coordinator
• Interleukins, interferons and cytokines (other than hematopoietic growth factors): >= 21 days after the completion of interleukins, interferon or cytokines (other than hematopoietic growth factors)
• Stem cell infusions (with or without total-body irradiation [TBI]):
• Allogeneic (non-autologous) bone marrow or stem cell transplant, or any stem cell infusion including donor lymphocyte infusion (DLI) or boost infusion: >= 84 days after infusion and no evidence of graft versus host disease (GVHD)
• Autologous stem cell infusion including boost infusion: >= 42 days
• Cellular therapy: >= 42 days after the completion of any type of cellular therapy (e.g. modified T cells, natural killer (NK) cells, dendritic cells, etc.)
• X-ray therapy (XRT)/External Beam Irradiation including Protons: >= 14 days after local XRT; >= 150 days after TBI, craniospinal XRT or if radiation to >= 50% of the pelvis; >= 42 days if other substantial bone marrow (BM) radiation; note: radiation may not be delivered to "measurable disease" tumor site(s) being used to follow response to subprotocol treatment
• Radiopharmaceutical therapy (e.g., radiolabeled antibody, 131I-MIBG): >= 42 days after systemically administered radiopharmaceutical therapy
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: For patients with solid tumors without known bone marrow involvement:
• Peripheral absolute neutrophil count (ANC) >= 1000/mm^3
• Platelet count >= 100,000/mm^3 (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment)
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Patients with known bone marrow metastatic disease will be eligible for study provided they meet the blood counts (may receive transfusions provided they are not known to be refractory to red cell or platelet transfusions); these patients will not be evaluable for hematologic toxicity
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 ml/min/1.73 m^2 or a serum creatinine based on age/gender as follows:
• Age: 1 to < 2 years; maximum serum creatinine (mg/dL): male 0.6; female 0.6
• Age: 2 to < 6 years; maximum serum creatinine (mg/dL): male 0.8; female 0.8
• Age: 6 to < 10 years; maximum serum creatinine (mg/dL): male 1; female 1
• Age: 10 to < 13 years; maximum serum creatinine (mg/dL): male 1.2; female 1.2
• Age: 13 to < 16 years; maximum serum creatinine (mg/dL): male 1.5; female 1.4
• Age: >= 16 years; maximum serum creatinine (mg/dL): male 1.7; female 1.4
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Bilirubin (sum of conjugated + unconjugated) =< 1.5 x upper limit of normal (ULN) for age
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Serum glutamate pyruvate transaminase (SGPT) (alanine transferase [ALT]) =< 135 U/L (for the purpose of this study, the ULN for SGPT is 45 U/L)
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Patients must be able to swallow intact capsules/tablets, unless otherwise specified in the subprotocol to which they are assigned
• GENERAL INCLUSION CRITERIA FOR SUBPROTOCOLS: Agent specific limitations on prior therapy will be included with specific treatment subprotocols
• GENERAL EXCLUSION CRITERIA FOR SUBPROTOCOLS: Pregnant or breast-feeding women will not be entered on this study due to risks of fetal and teratogenic adverse events as seen in animal/human studies, or because there is currently no available information regarding human fetal or teratogenic toxicities; pregnancy tests must be obtained in females who are post-menarchal; males or females of reproductive potential may not participate unless they have agreed to use an effective contraceptive method
• GENERAL EXCLUSION CRITERIA FOR SUBPROTOCOLS: Concomitant medications
• Corticosteroids: at the time of consent and enrollment to regimen specific subprotocols, patients receiving corticosteroids who have not been on a stable or decreasing dose of corticosteroid for at least 7 days prior to enrollment to the subprotocol will not be eligible; if used to modify immune adverse events related to prior therapy, >= 14 days must have elapsed since last dose of corticosteroid
• Investigational drugs: patients must meet criteria for prior therapy at the time of consent and enrollment to a subprotocol; other investigational agents may not be administered to patients while they are receiving study drug as part of a subprotocol
• Anticancer agents: patients must meet criteria for prior therapy at the time of consent and enrollment to a subprotocol; other investigational agents may not be administered to patients while they are receiving study drug as part of a subprotocol
• Anti-GVHD agents post-transplant: patients who are receiving cyclosporine, tacrolimus or other agents to prevent graft-versus-host disease post bone marrow transplant are not eligible
• GENERAL EXCLUSION CRITERIA FOR SUBPROTOCOLS: Patients who have an uncontrolled infection are not eligible
• GENERAL EXCLUSION CRITERIA FOR SUBPROTOCOLS: Patients who have had a prior solid organ transplant are not eligible
• GENERAL EXCLUSION CRITERIA FOR SUBPROTOCOLS: Additional agent specific criteria will be included with specific treatment subprotocols

• Enrollment must occur within 6 months of initial disease presentation OR within 6 months of refractory disease, disease progression, disease recurrence, second or secondary malignancy, or post-mortem
• Patients previously enrolled on ACCRN07 are eligible to enroll on Tracking Outcome, Registry and Future Contact components of APEC14B1 any time after they reach age of majority
• Patients with a known or suspected neoplasm that occurs in the pediatric, adolescent or young adult populations are eligible for enrollment as follows:
• All cancer cases with an International Classification of Diseases for Oncology (ICD-O) histologic behavior code of one "1" (borderline), two "2" (carcinoma in situ) or three "3" (malignant)
• All neoplastic lesions of the central nervous system regardless of behavior, i.e., benign, borderline or malignant
• The following other benign/borderline conditions:
• Mesoblastic nephroma
• Teratomas (mature and immature types)
• Myeloproliferative diseases including transient myeloproliferative disease
• Langerhans cell histiocytosis
• Lymphoproliferative diseases
• Desmoid tumors
• Gonadal stromal cell tumors
• Neuroendocrine tumors including pheochromocytoma
• Melanocytic tumors, except clearly benign nevi
• Ganglioneuromas
• Subjects must be =< 25 years of age at time of original diagnosis, except for patients who are being screened specifically for eligibility onto a COG (or COG participating National Clinical Trials Network [NCTN]) therapeutic study, for which there is a higher upper age limit
• All patients or their parents or legally authorized representatives must sign a written informed consent and agree to participate in at least one component of the study; parents will be asked to sign a separate consent for their own biospecimen submission
• If patients or their parents or legally authorized representatives have not signed the Part A subject consent form at the time of a diagnostic bone marrow procedure, it is recommended that they initially provide consent for drawing extra bone marrow using the Consent for Collection of Additional Bone Marrow; consent using the Part A subject consent form must be provided prior to any other procedures for eligibility screening or banking under APEC14B1

• Diagnosis of MG with generalized muscle weakness meeting the clinical criteria defined by Myasthenia Gravis Foundation of America (MGFA) Class II, III or IV
• Positive serological test for autoantibodies against AChR
• History of thymectomy, or any other thymic surgery within 12 months prior to Screening
• Untreated thymic malignancy, carcinoma, or thymoma
• History of Neisseria meningitidis infection
• Pregnancy, breastfeeding, or intention to conceive during the course of the study