Inclusion Criteria:

Part 1 1. Written Informed Consent (mentally competent patient, able to understand and willing to sign the informed consent form) 2. Age ≥ 18 years, male or non-pregnant female 3. Able to comply with the study protocol, as per Investigator's judgment 4. Histologically confirmed, unresectable locally advanced or metastatic cancer. There are no limits to prior lines of therapies received for the treatment of the cancer condition for which the patient is being enrolled into this study. 1. For the Part 1 combination urothelial carcinoma Cohorts 13 and 14: histologically or cytologically confirmed diagnosis of unresectable, locally advanced or metastatic urothelial carcinoma of the renal pelvis, ureter, bladder, or urethra (i.e., transitional cell carcinoma). 2. For the Part 1 combination H/N cancer Cohorts 11 and 12: histologically confirmed, locally advanced or metastatic squamous cell carcinoma of head and neck (SCCHN; oral cavity, oropharynx, hypopharynx, or larynx). 5. For urothelial and H/N combination cancer cohorts, prior exposure to immunotherapy is allowed, with standard of care treatment options and/or within a clinical trial context. If the patient received an anti-PD-1 and/or an anti-PD-L1 containing regimen at any point, they must have demonstrated at least stable disease, as per RECIST 1.1 or iRECIST criteria to one of these treatment regimens, if these measurements are available. If RECIST or iRECIST measurements are not available, then clinical PFS of at least 4 months is required to have been achieved on any of the prior anti-PD-1 and/or anti-PD-L1 containing regimens. 6. There is no PD-L1 expression requirement for the Part 1 combination urothelial and H/N cohorts; however, fresh biopsy or archival tissue is required for assessment of PD-L1 by IHC, or a historical PD-L1 expression by IHC must be available. If PD-L1 expression data are already available, this does not override the protocol preference for obtaining a fresh biopsy whenever feasible. 7. For Part 1 combination cohort H/N cancer patients of oropharynx origin: human papilloma virus (HPV) status needs to be established in the screening period or at any point while patient is on study drug, unless it is historically known. p16+ as a surrogate for HPV+, HPV RNA ISH or DNA PCR are all acceptable. The study accepts both HPV+ and HPV- patients. 8. Life expectancy > 3 months according to Investigator's judgment 9. ECOG performance status 0-1 10. Patient able and willing to undergo pre- and on/post treatment biopsies. According to the Investigator's judgment, the planned biopsies should not expose the patient to substantially increased risk of complications. Every effort will be made that the same lesion is biopsied on repeat biopsies. If the patient is eligible according to all other criteria but declines to consent to a biopsy or there are other medical reasons precluding biopsy, this will be discussed with the Sponsor. 11. Measurable disease, according to RECIST v1.1. Note that lesions intended to be biopsied should not be target lesions. 12. Adequate hematologic and end organ function, defined by the following laboratory results obtained prior to first dose of study drug treatment, provided no anticancer treatment was administered within the last 7 days: 1. neutrophil count ≥ 1 x 109/L 2. platelet count ≥ 100 x 109/L; for hepatocellular carcinoma (HCC) in Part 1 ≥ 50 x 109/L 3. hemoglobin ≥ 9.0 g/dL without transfusion in the previous week 4. creatinine ≤ 1.5 x the upper limit of normal (ULN); or eGFR > 50 mg/mmol 5. aspartate aminotransferase AST (SGOT) ≤ 3 x ULN (≤ 5 x ULN when HCC or hepatic metastases are present) 6. alanine aminotransferase (ALT [SGPT]) ≤ 3 x ULN (≤ 5 x ULN when HCC or hepatic metastases present) 7. bilirubin ≤ 1.5 x ULN (patients with known Gilbert's disease may have a bilirubin ≤ 3.0 x ULN) 8. albumin ≥ 3.0 g/dL 9. international normalized ratio (INR) and partial thromboplastin time (PTT) ≤ 1.5 x ULN, unless patient receiving anticoagulant therapy 13. No evidence of active serious infection or infections requiring parenteral antibiotics. 14. Women of childbearing potential must have a negative pregnancy test within 72 h prior to start of treatment. For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or to use contraceptive methods that result in a failure rate of < 1% per year during the treatment period and for at least 180 days after the last study treatment. A woman is of childbearing potential if she is post-menarche, has not reached a postmenopausal state (≥ 12 continuous months of amenorrhea with no identified cause other than menopause), and has not undergone surgical sterilization (removal of ovaries and/or uterus). Examples of contraceptive methods with a failure rate of < 1% per year include bilateral tubal ligation, male sterilization, hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices and copper intrauterine devices. The reliability of sexual abstinence should be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the patient. Periodic abstinence (e.g., calendar, ovulation, symptom-thermal, or post ovulation methods) and withdrawal are not acceptable methods of contraception. Fertile men must practice effective contraceptive methods during the study, unless documentation of infertility exists. 15. Four (4) weeks or 5 half-lives (whichever is shorter) since the last dose of anticancer therapy before the first LYT-200 administration 16. Bisphosphonate treatment (e.g., zoledronic acid) or denosumab are allowed if previously used prior to commencement of clinical trial. 17. Patients: 1. who have already received at least one prior line of systemic therapy for metastatic or locally advanced disease, and/or 2. who have a tumor type for which there are no available standard of care options 18. Patients who have not previously received a gemcitabine-containing regimen

Exclusion Criteria

1. Patient unwilling or unable to follow protocol requirements 2. Patient diagnosed with metastatic cancer of an unknown primary 3. Current illicit drug addiction (medical and recreational marijuana/cannabidiol [CBD]/ tetrahydrocannabinol [THC] would not be considered "illicit") 4. Clinically significant, active uncontrolled bleeding, and any patients with a bleeding diathesis (e.g., active peptic ulcer disease). Prophylactic or therapeutic use of anticoagulants is allowed. 5. Pregnant and/or lactating females 6. Receiving any other investigational agents or participating in any other clinical trial involving another investigational agent for treatment of solid tumors within 3 weeks or 5 half-lives of the administered drug (whichever is shorter) prior to the first dose of study drug, or major surgery or planned surgery within 4 weeks of the first dose of study drug (this includes dental surgery). 7. Radiation therapy within 4 weeks of the first dose of study drug, except for palliative radiotherapy to a limited field, such as for the treatment of bone pain or a focally painful tumor mass, and which does not jeopardize required measurable lesions for response assessment (RECIST v1.1). 8. Patients with fungating tumor masses 9. History or current evidence of any condition, therapy, any active infections, or laboratory abnormality that might confound the results of the trial, interfere with the patient's participation for the full duration of the trial, or is not in the best interest of the patient to participate, in the opinion of the treating Investigator 10. Grade 4 immune-mediated toxicities with a prior checkpoint inhibitor. Grade 2 or Grade 3 pneumonitis or any other Grade 3 checkpoint inhibitor-related toxicity that led to immunotherapy treatment discontinuation. Low-grade (< Grade 3) toxicities, such as neuropathy from prior treatments, manageable electrolyte abnormalities and lymphopenia, alopecia and vitiligo are allowed. 11. History of other prior or other concomitant malignancy that requires other active treatment. 12. Active parenchymal brain metastases, patients with carcinomatous meningitis or leptomeningeal metastases. Patients with brain metastases are eligible provided they have shown clinically and radiographically stable disease for at least 4 weeks after definitive therapy and have not used steroids (> 10 mg/day of prednisone or equivalent) for at least 4 weeks prior to the first dose of study drug 13. Evidence of severe or uncontrolled systemic diseases, congestive heart failure > New York Heart Association (NYHA) class 2, myocardial infarction (MI) within 6 months, or laboratory finding that in the view of the Investigator makes it undesirable for the patient to participate in the trial 14. Any medical condition that the Investigator considers significant to compromise the safety of the patient or that impairs the interpretation of LYT-200 toxicity assessment 15. Serious non-healing wound, active ulcer, or untreated bone fracture unless for e.g., a rib fracture for (which does not elicit treatment) 16. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures. For the purposes of this study, "recurrent" is defined as ³ 3 drains in the last 30 days 17. History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins 18. Significant vascular disease (e.g., aortic aneurysm requiring surgical repair or recent arterial thrombosis) within 6 months of Cycle 1, Day 1 19. History of pulmonary embolism, stroke or transient ischemic attack within 3 months prior to Cycle 1, Day 1 20. Active autoimmune disorder (except type I/II diabetes, hypothyroidism requiring only hormone replacement, vitiligo, psoriasis, or alopecia areata). 21. Requires systemic immunosuppressive treatment, including, but not limited to cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor (anti-TNF) agents. Patients who have received or are receiving acute, low dose systemic immunosuppressant medications (e.g., ≤ 10 mg/day of prednisone or equivalent) may be enrolled. Replacement therapy (e.g., thyroxine, insulin, physiologic corticosteroid replacement therapy [e.g., ≤ 10 mg/day of prednisone equivalent] for adrenal or pituitary insufficiency) is not considered a form of systemic treatment. The use of inhaled corticosteroids and mineralocorticoids (e.g., fludrocortisone), topical steroids, intranasal steroids, intra-articular, and ophthalmic steroids is allowed. 22. Severe tumor-related pain (Grade 3, CTCAE v.5.0) unresponsive to broad analgesic interventions (oral and/or patches) 23. Hypercalcemia (defined as ³ Grade 3, per CTCAE v 5.0) despite use of bisphosphonates 24. Any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk of treatment complications 25. Received organ transplant(s) 26. Patients undergoing dialysis 27. For Part 1, hormonal androgen deprivation therapy is allowed to continue for patients with metastatic castration-resistant prostate cancer 28. Any ablative therapy (Radio Frequency Ablation or Percutaneous Ethanol Injection) for HCC < 6 weeks prior trial entry 29. Hepatic encephalopathy or severe liver adenoma 30. Child-Pugh score ≥ 7

Key Inclusion Criteria:

Subjects are eligible for enrollment into this study if they meet any of the following criteria (NOTE: This is not an exhaustive list):
• Subjects aged ≥18 years.
• ECOG performance status 0 or 1
• Subjects must have a documented IDH mutation per immunohistochemistry (IHC), polymerase chain reaction (PCR), or next generation sequencing (NGS) testing of tumor tissue.
• Subjects must have histologically or cytologically documented, advanced or metastatic solid malignancy of any type that has recurred or progressed on available standard treatment and for which no curative therapy exists.

Key Exclusion Criteria:

Subjects are not eligible for enrollment into this study if they meet any of the following criteria (NOTE: This is not an exhaustive list):
• Subjects who received an investigational agent <14 days prior to their first day of study drug administration
• Subjects who are pregnant or breastfeeding
• Subjects with an active severe infection, some treated infections and with an expected or with an unexplained fever >38.3°C during screening visits or on their first day of study drug administration.
• Subjects with some current or prior heart conditions
• Subjects taking medications that are known to prolong the QT interval may not be eligible
• Subjects with immediately life-threatening, severe complications of leukemia such as uncontrolled bleeding, pneumonia with hypoxia or shock, and/or disseminated intravascular coagulation
• Some subjects with some current or prior gastrointestinal or liver diseases
• Subjects with inadequate organ function as defined by the protocol

Inclusion Criteria

1. Patients in the Phase 1 dose-escalation portion must have a diagnosis of relapsed or refractory AML, ALL or acute leukemia of ambiguous lineage, as determined by pathology review at the treating institution, and who failed available standard therapies known to be active for their AML, ALL, or acute leukemia of ambiguous lineage. Enrollment to the phase 1 portion of the study may be limited to patients with certain genetic abnormalities. Patients in the Phase 2 dose-expansion portion must have a confirmed diagnosis of relapsed or refractory AML, as determined by pathology review at the treating institution, and who failed available standard therapies known to be active for their AML. They must also have a documented KMT2A (MLL)-fusion or NPM1 mutation, which includes those with coexisting FLT3 genomic alterations and/or IDH1/2 mutations. 2. Be > 18 years of age or 20 years if required by local regulation 3. ECOG < 2 4. WBC below 30,000/μL (hydroxyurea allowed prior to initiation of the study treatment) 5. Clearance of creatinine (CLcr) level ≥ 50 ml/min, assessed by the Cockcroft-Gault formula 6. Total bilirubin ≤1.5 the upper limit of normal (ULN) (or ≤2.0 ULN for patients with known Gilbert's syndrome) 7. Aspartate aminotransferase (AST) ≤3.0 times ULN 8. Alanine aminotransferase (ALT) ≤3.0 times ULN 9. Any prior treatment-related toxicities resolved to ≤Grade 1 prior to enrollment, with the exception of ≤Grade 2 alopecia or neuropathy. 10. Be willing to attend study visits as required by the protocol 11. Have an estimated life expectancy ≥3 months, based on the investigator's assessment 12. Females of childbearing potential must have a negative serum pregnancy test. Females of childbearing potential are defined as women who have (1) experienced menarche and have not undergone sterilization procedures (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy), or have (2) not experienced menopause (defined as having amenorrhea continuously for more than 12 months that is not determined to be drug-induced, or who are taking hormone replacement therapy with serum follicle-stimulating hormone > 35 mlU/ml). 13. Must agree to use a combination of 2 or more different contraception methods (oral contraceptives/implantable hormonal contraceptives*, and barrier method*) or use prevention of pregnancy measures (ie, agreement to refrain completely from heterosexual intercourse) during the study and for 6 months (for females and males alike) after the last dose of study drug, if male or female patient of child-producing potential 14. Have AML/ALL material suitable for genomic analysis of AML or ALL genetic alterations

Exclusion Criteria:

1. Has a left ventricular ejection fraction (LVEF) <45%, as determined by ECHO 2. Histological diagnosis of acute promyelocytic leukemia 3. Received systemic calcineurin inhibitors within 4 weeks prior to the first dose of DSP 5336 4. Has had abnormal ECGs that are clinically significant, such as QT prolongation (QTc >450 msec for males and >470 msec for females, with QTc corrected according to Fridericia's formula [QTcF]) 5. Has an active, uncontrolled, bacterial, viral, or fungal infection requiring systemic therapy 6. Receives concurrent sensitive substrates with a narrow safety window or strong inhibitors or inducers of CYP3A4/5, including specifically: ketoconazole and itraconazole. Other antifungals that are used as standard of care to prevent or treat infections are permitted. If a patient is on one of the excluded azole class antifungals, he/she can be taken off or switched to a permitted azole 7 or more days prior to first dose, then the patient could be allowed on study (Arm B) with approval of the medical monitor. 7. Received immunotherapy, including tumor vaccines and checkpoint inhibitors, within 42 days prior to the first dose of DSP-5336 8. Has been on other investigational treatment within the previous 4 weeks prior to the first dose of DSP-5336 9. Had major surgery within 28 days prior to the first dose of DSP-5336 10. Has active central nervous system leukemia 11. Previously received menin-MLL inhibitors 12. Has immediately life threatening or severe complications of leukemia 13. Underwent HSCT or chimeric antigen receptor cell (CAR-T) therapy or other modified T-cell therapy within 60 days prior to the first dose of DSP-5336 14. Received a donor lymphocyte infusion within 28 days prior to the first dose of DSP-5336, or receiving immunosuppressive therapy post-HSCT at the time of screening, or with clinically active GVHD or GVHD requiring active medical intervention other than the use of topical steroids for ongoing cutaneous GVHD 15. Received antineoplastic agents (except hormonal therapies as adjuvant maintenance for breast or prostate cancers if a patient is taking before starting study treatment, and hydroxyurea given for controlling blast cells) within 14 days prior to the first dose of DSP-5336 16. Received anthracycline where cumulative doses exceeded the upper limit per the label approved in each country or investigator discretion (if there is no label restriction, investigator must state the cumulative dose received for each patient and sign to indicate that, in his/her medical opinion, stated prior dose of the agent does not put patient at undue risk of anthracycline-related cardiotoxicity 17. In the opinion of the treating investigator, have any concurrent conditions that could pose an undue medical hazard or interfere with interpretation of study results; these conditions include, but are not limited to: clinically significant non-healing or healing wounds; concurrent congestive heart failure; concurrent unstable angina; concurrent cardiac arrhythmia requiring treatment (excluding asymptomatic atrial fibrillation); recent (within the prior 6 months) myocardial infarction; acute coronary syndrome within the previous 6 months; significant pulmonary disease (shortness of breath at rest or on mild exertion), eg, due to concurrent severe obstructive pulmonary disease, concurrent hypertension not controlled with concomitant medication, or diabetes mellitus with more than 2 episodes of ketoacidosis in the prior 6 months 18. Have an active acute or chronic infection, including human immunodeficiency virus (HIV) as determined by anti-HIV antibodies; and hepatitis B virus (HBV) or hepatitis C virus (HCV) as determined by hepatitis B surface antigen (HBsAg) or anti-HCV antibodies, respectively. For sites in Japan only: Hepatitis B core (HBc) antibody or hepatitis B surface (HBs) antibody test should be performed if HBsAg is negative. If HBc antibody or HBs antibody test is positive, HBV DNA quantification test should be performed to confirm that HBV DNA is negative. 19. Have advanced liver disease or cirrhosis (Child-Pugh's Class B or greater) 20. Have one or more active autoimmune diseases requiring immunosuppressive therapy other than low-dose corticosteroids (equivalent to prednisone 10mg daily) or azathioprine. Patients on stable immunomodulatory medications may be considered by the investigator 21. Have active (uncontrolled, metastatic) malignancies of another type 22. Have severe dysphagia, short-gut syndrome, gastroparesis, or other conditions that limit the ingestion or gastrointestinal absorption of drugs administered orally, including the inability to swallow oral medication 23. Have cognitive, psychologic, or psychosocial impediment that would impair the ability of the patient o receive therapy according to the protocol, or adversely affect the ability of the patient to comply with the informed consent process, protocol, or protocol-required visits and procedures 24. Are pregnant or breastfeeding or planning to become pregnant Note: Patients who are breastfeeding may be enrolled if they interrupt breastfeeding prior to the first dose of any study drugs and do not feed the baby with breast milk expressed after receiving the first dose of any study drugs. Breastfeeding should not be resumed for at least 6 months after the last dose of study drug 25. Have any history or complication of interstitial lung disease (for sites in Japan only) 26. Have a history of Torsades de Pointes

Inclusion Criteria:

• All patients must be enrolled on APEC14B1 and consented to Eligibility Screening (Part A) prior to enrollment and treatment on AAML1831. Submission of diagnostic specimens must be done according to the Manual of Procedures
• Patients must be less than 22 years of age at the time of study enrollment
• Patient must be newly diagnosed with de novo AML according to the 2016 World Health Organization (WHO) classification with or without extramedullary disease
• Patient must have 1 of the following:
• >= 20% bone marrow blasts (obtained within 14 days prior to enrollment)
• In cases where extensive fibrosis may result in a dry tap, blast count can be obtained from touch imprints or estimated from an adequate bone marrow core biopsy
• < 20% bone marrow blasts with one or more of the genetic abnormalities associated with childhood/young adult AML as provided in the protocol (sample obtained within 14 days prior to enrollment)
• A complete blood count (CBC) documenting the presence of at least 1,000/uL (i.e., a white blood cell [WBC] count >= 10,000/uL with >= 10% blasts or a WBC count of >= 5,000/uL with >= 20% blasts) circulating leukemic cells (blasts) if a bone marrow aspirate or biopsy cannot be performed (performed within 7 days prior to enrollment)
• ARM C: Patient must be >= 2 years of age at the time of Late Callback
• ARM C: Patient must have FLT3/ITD allelic ratio > 0.1 as reported by Molecular Oncology
• ARM C: Patient does not have any congenital long QT syndrome or congenital heart block
• ARM C: Females of reproductive potential must agree to use effective contraception during treatment and for at least 6 months after the last dose of gilteritinib
• ARM C: Lactating women must agree not to breastfeed during treatment with gilteritinib and for 2 months after the last dose of gilteritinib
• ARM C: Males of reproductive potential must agree to use effective contraception during treatment and for at least 4 months after the last dose of gilteritinib
• ARM D: Patient must be >= 2 years of age at the time of Late Callback
• ARM D: Patient must have one of the clinically relevant non-ITD FLT3 activating mutations as reported by Foundation Medicine
• ARM D: Females of reproductive potential must agree to use effective contraception during treatment and for at least 6 months after the last dose of gilteritinib
• ARM D: Lactating women must agree not to breastfeed during treatment with gilteritinib and for 2 months after the last dose of gilteritinib
• ARM D: Males of reproductive potential must agree to use effective contraception during treatment and for at least 4 months after the last dose of gilteritinib
• NEUROPSYCHOLOGICAL TESTING: Patient must be enrolled on Arm A or Arm B. Patients who transfer to Arm C or Arm D are not eligible
• NEUROPSYCHOLOGICAL TESTING: Patient must be 5 years or older at the time of enrollment
• NEUROPSYCHOLOGICAL TESTING: English-, French- or Spanish-speaking
• NEUROPSYCHOLOGICAL TESTING: No known history of neurodevelopmental disorder prior to diagnosis of AML (e.g., Down syndrome, fragile X, William syndrome, mental retardation)
• NEUROPSYCHOLOGICAL TESTING: No significant visual or motor impairment that would prevent computer use or recognition of visual test stimuli
• All patients and/or their parents or legal guardians must sign a written informed consent
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Exclusion Criteria:

• Fanconi anemia
• Shwachman Diamond syndrome
• Patients with constitutional trisomy 21 or with constitutional mosaicism of trisomy 21
• Telomere disorders
• Germline predispositions known, or suspected by the treating physician to increase risk of toxicity with AML therapy
• Any concurrent malignancy
• Juvenile myelomonocytic leukemia (JMML)
• Philadelphia chromosome positive AML
• Mixed phenotype acute leukemia
• Acute promyelocytic leukemia
• Acute myeloid leukemia arising from myelodysplasia
• Therapy-related myeloid neoplasms
• Patients with persistent cardiac dysfunction prior to enrollment, defined as ejection fraction (EF) < 50% (preferred method Biplane Simpson's EF) or if EF unavailable, shortening fraction (SF) < 24%. *Note: if clinically safe and feasible, repeat echocardiogram is strongly advised in order to confirm cardiac dysfunction following clinical stabilization, particularly if occurring in the setting of sepsis or other transient physiologic stressor. If the repeat echocardiogram demonstrates an EF >= 50%, the patient is eligible to enroll and may receive an anthracycline-containing Induction regimen
• Administration of prior anti-cancer therapy except as outlined below:
• Hydroxyurea
• All-trans retinoic acid (ATRA)
• Corticosteroids (any route)
• Intrathecal therapy given at diagnosis
• In particular, strong inducers of CYP3A4 and/or P-glycoprotein (P-gp) should be avoided from the time of enrollment until it is determined whether the patient will receive gilteritinib. Patients receiving gilteritinib will be required to avoid strong CYP3A4 inducers and/or strong P-gp inducers for the duration of the study treatment
• Female patients who are pregnant since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test is required for female patients of childbearing potential
• Lactating females who plan to breastfeed their infants
• Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation
• ARM D: Patient does not have any congenital long QT syndrome or congenital heart block

Inclusion Criteria:

• All B-ALL patients must be enrolled on APEC14B1 and consented to Eligibility Screening (Part A) prior to treatment and enrollment on AALL1731. APEC 14B1 is not a requirement for B-LLy patients. B-LLy patients may directly enroll on AALL1731.
• Age at diagnosis:
• Patients must be >= 365 days and < 10 years of age (B-ALL patients without DS).
• Patients must be >= 365 days and =< 31 years of age (B-ALL patients with DS).
• Patients must be >= 365 days and =< 31 years of age (B-LLy patients with or without DS).
• B-ALL patients without DS must have an initial white blood cell count < 50,000/uL (performed within 7 days prior to enrollment).
• B-ALL patients with DS are eligible regardless of the presenting white blood cell count (WBC) (performed within 7 days prior to enrollment).
• Patient has newly diagnosed B-cell ALL, with or without Down syndrome: > 25% blasts on a bone marrow (BM) aspirate;
• OR if a BM aspirate is not obtained or is not diagnostic of B-ALL, the diagnosis can be established by a pathologic diagnosis of B-ALL on a BM biopsy;
• OR a complete blood count (CBC) documenting the presence of at least 1,000/uL circulating leukemic cells;
• OR patient has newly diagnosed B-cell LLy Murphy stages I or II, with or without Down syndrome.
• Note: For B-LLy patients with tissue available for flow cytometry, the criterion for diagnosis should be analogous to B-ALL. For tissue processed by other means (i.e., paraffin blocks), the methodology and criteria for immunophenotypic analysis to establish the diagnosis of B-LLy defined by the submitting institution will be accepted (diagnostic biopsy for B-LLy must be performed within 14 days prior to enrollment).
• All patients and/or their parents or legal guardians must sign a written informed consent.
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met.

Exclusion Criteria:

• Patient must not have secondary ALL that developed after treatment of a prior malignancy with cytotoxic chemotherapy. Note: patients with Down syndrome with a prior history of transient myeloproliferative disease (TMD) are not considered to have had a prior malignancy. They would therefore be eligible whether or not the TMD was treated with cytarabine.
• With the exception of steroid pretreatment or the administration of intrathecal cytarabine, patients must not have received any prior cytotoxic chemotherapy for either the current diagnosis of B ALL or B LLy or for any cancer diagnosed prior to initiation of protocol therapy on AALL1731.
• For patients receiving steroid pretreatment, the following additional exclusion criteria apply:
• Non-DS B-ALL patients must not have received steroids for more than 24 hours in the 2 weeks prior to diagnosis without a CBC obtained within 3 days prior to initiation of the steroids.
• DS and non-DS B-LLy patients must not have received > 48 hours of oral or IV steroids within 4 weeks of diagnosis.
• Patients who have received > 72 hours of hydroxyurea within 1 week (7 days) prior to the start of systemic protocol therapy.
• B-ALL patients who do not have sufficient diagnostic bone marrow submitted for APEC14B1 diagnostic testing and who do not have a peripheral blood sample submitted containing > 1,000/uL circulating leukemia cells.
• Patient must not have acute undifferentiated leukemia (AUL).
• Non-DS B-ALL patients with central nervous system [CNS]3 leukemia (CNS status must be known prior to enrollment).
• Note: DS patients with CNS3 disease are eligible but will be assigned to the DS-High B-ALL arm. CNS status must be determined based on a sample obtained prior to administration of any systemic or intrathecal chemotherapy, except for steroid pretreatment.
• Non-DS B-ALL patients with testicular leukemia. (Note: DS patients with testicular disease are eligible but will be assigned to the DS-High B-ALL arm).
• For LLy patients, the following additional exclusion criteria apply:
• T-Lymphoblastic Lymphoma.
• Morphologically unclassifiable lymphoma.
• Absence of both B-cell and T-cell phenotype markers in a case submitted as lymphoblastic lymphoma.
• CNS positive disease or testicular involvement.
• M2 (5% - 25% blasts) or M3 (> 25% blasts) marrow.
• Patients with known Charcot-Marie-Tooth disease.
• Patients with known MYC translocation associated with mature (Burkitt) B-cell ALL, regardless of blast immunophenotype.
• Patients requiring radiation at diagnosis.
• Female patients who are pregnant since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test is required for female patients of childbearing potential.
• Lactating females who plan to breastfeed their infants.
• Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation.

Inclusion Criteria:

• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Relapsed or refractory ALL after multi-agent chemotherapy (>= 5% marrow lymphoblasts, assessed by morphology and flow cytometry; flow cytometry will be used to confirm immunophenotype and percentage of blasts will be assessed by morphology)
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Adequate liver function with aspartate aminotransferase (AST)/alanine aminotransferase (ALT) less than 3 X upper limit of normal and total bilirubin less than 2 mg/dL within 7 days prior to first dose of study agent
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Circulating white blood cell (WBC) count must not be above 20 x10^9/L within 7 days prior to first dose of study agent
• Patients with WBC count above 20 x 10^9/L may be eligible if they start steroids or hydroxyurea per institutional guidelines, but they must discontinue before day 1 of study drug
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Creatinine clearance of at least 50 mL/min within 7 days prior to first dose of study agent
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Women must not be pregnant or breast-feeding
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): All females of childbearing potential must have a blood test or urine study within 2 weeks prior to registration to rule out pregnancy; a female of childbearing potential is any woman, regardless of sexual orientation or whether they have undergone tubal ligation, who meets the following criteria: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months)
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Women of childbearing potential and sexually active males must use an accepted and highly effective method of contraception or to abstain from sexual intercourse for the duration of their participation in the study and for 30 days after the last dose of venetoclax; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she (or the participating partner) should inform the treating physician immediately
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): No evidence of prior malignancy except adequately treated non-melanoma skin cancer, in situ cervical carcinoma, or any surgically- or radiation-cured malignancy continuously disease free for >= 5 years so as not to interfere with interpretation of radiographic response
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): No evidence of isolated extramedullary relapse (i.e., testicular or central nervous system [CNS])
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patient must not have Burkitt?s lymphoma/leukemia based on the World Health Organization (WHO) criteria
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients must not have active central nervous system (CNS) leukemia, as defined by unequivocal morphologic evidence of lymphoblasts in the cerebrospinal fluid (CSF), use of CNS-directed local treatment for active disease within the prior 28 days; previously treated CNS disease with documented cleared CSF will be allowed
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patient will not be enrolled if they received prior chemotherapy within 2 weeks before enrollment with the following exceptions: to reduce the circulating lymphoblast count or palliation (i.e., steroids or hydroxyurea) or for ALL maintenance (mercaptopurine, methotrexate, vincristine, thioguanine, and/or tyrosine kinase inhibitors)
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patient may be enrolled with a prior allogeneic hematopoietic stem cell transplant (HSCT) but the transplant date must be at least 90 days before date of enrollment; patient must be off immunosuppression and without active graft versus host disease (GVHD) prior to enrollment if previous HSCT
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patient cannot have poorly controlled human immunodeficiency virus (HIV), or CD4 < 400; HIV positive patients are allowed on this study if they have a CD4 count >= 400, and are on a stable antiviral regimen
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients with New York Heart Association (NYHA) class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence of acute ischemia may not be enrolled
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients with serious medical or psychiatric illness that in the opinion of the primary investigator is likely to interfere with study participation may not be enrolled
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients must not be participating in any other clinical trial or taking any other experimental medications within 21 days prior to registration
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients should not have received the following within 7 days prior to the first dose of study drug:
• Steroid therapy for anti-neoplastic intent;
• Strong and moderate CYP3A inhibitors;
• Strong and moderate CYP3A inducers
• ELIGIBILITY CRITERIA - PHASE I (ARMS A, B, C): Patients must not have grade 3 or higher peripheral neuropathy
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Relapsed or refractory ALL after multi-agent chemotherapy (>= 5% marrow lymphoblasts, assessed by morphology and flow cytometry; flow cytometry will be used to confirm immunophenotype and percentage of blasts will be assessed by morphology)
• ELIGIBILITY CRITERIA - PHASE II (ARM D): ECOG performance status 0-2
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Adequate liver function with AST/ALT less than 3 X upper limit of normal and total bilirubin less than 2 mg/dL within 7 days prior to first dose of study agent
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Circulating WBC count must not be above 20 x10^9/L within 7 days prior to first dose of study agent
• Patients with WBC count above 20 x10^9/L may be eligible if they start steroids or hydroxyurea per institutional guidelines, but they must discontinue before day 1 of study drug
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Creatinine clearance of at least 50 mL/min within 7 days prior to first dose of study agent
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Women must not be pregnant or breast-feeding
• ELIGIBILITY CRITERIA - PHASE II (ARM D): All females of childbearing potential must have a blood test or urine study within 2 weeks prior to registration to rule out pregnancy; a female of childbearing potential is any woman, regardless of sexual orientation or whether they have undergone tubal ligation, who meets the following criteria: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months)
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Women of childbearing potential and sexually active males must use an accepted and highly effective method of contraception or to abstain from sexual intercourse for the duration of their participation in the study and for 30 days after the last dose of venetoclax; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she (or the participating partner) should inform the treating physician immediately
• ELIGIBILITY CRITERIA - PHASE II (ARM D): No evidence of prior malignancy except adequately treated non-melanoma skin cancer, in situ cervical carcinoma, or any surgically- or radiation-cured malignancy continuously disease free for >= 5 years so as not to interfere with interpretation of radiographic response
• ELIGIBILITY CRITERIA - PHASE II (ARM D): No evidence of isolated extramedullary relapse (i.e., testicular or CNS)
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patient must not have Burkitt?s lymphoma/leukemia based on the WHO criteria
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients must not have active central nervous system (CNS) leukemia, as defined by unequivocal morphologic evidence of lymphoblasts in the cerebrospinal fluid (CSF), use of CNS-directed local treatment for active disease within the prior 28 days; previously treated CNS disease with documented cleared CSF will be allowed
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patient will not be enrolled if they received prior chemotherapy within 2 weeks before enrollment with the following exceptions: to reduce the circulating lymphoblast count or palliation (i.e., steroids or hydroxyurea), for ALL maintenance (mercaptopurine, methotrexate, vincristine, thioguanine, and/or tyrosine kinase inhibitors)
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patient may be enrolled with a prior allogeneic hematopoietic stem cell transplant (HSCT) but the transplant date must be at least 90 days before date of enrollment; patient must be off immunosuppression and without active GVHD prior to enrollment if previous HSCT
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patient cannot have poorly controlled HIV, or CD4 < 400; HIV positive patients are allowed on this study if they have a CD4 count >= 400, and are on a stable antiviral regimen
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients with NYHA class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence of acute ischemia may not be enrolled
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients with serious medical or psychiatric illness that in the opinion of the primary investigator is likely to interfere with study participation may not be enrolled
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients must not be participating in any other clinical trial or taking any other experimental medications within 21 days prior to registration
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients should not have received the following within 7 days prior to the first dose of study drug:
• Steroid therapy for anti-neoplastic intent;
• Strong and moderate CYP3A inhibitors;
• Strong and moderate CYP3A inducers
• ELIGIBILITY CRITERIA - PHASE II (ARM D): Patients must not have grade 3 or higher peripheral neuropathy

Key Inclusion Criteria:

Participants eligible for inclusion in this study must meet the following criteria: Criteria #1-5 are common to both patient cohorts (2L and 1L): 1. Signed informed consent must be obtained prior to participation in the study 2. CML-CP, no previous AP or BC 3. ≥ 18 years of age 4. ECOG performance status of 0, 1 or 2 5. Adequate end organ function within 14 days before the first dose of asciminib treatment. Patients with mild to moderate renal and hepatic impairment are eligible if:
• Total bilirubin ≤ 3.0 x ULN without AST/ALT increase
• Aspartate transaminase (AST) ≤ 5.0 x ULN
• Alanine transaminase (ALT) ≤ 5.0 x ULN
• Serum lipase ≤ 1.5 x ULN. For serum lipase > ULN and ≤ 1.5 x ULN, value should be considered not clinically significant and not associated with risk factors for acute pancreatitis
• Alkaline phosphatase ≤ 2.5 x ULN
• Creatinine clearance ≥ 30 mL/min as calculated using Cockcroft- Gault formula Criteria #6 and 7 are specific to the 2L patient cohort 6. Warning or failure (according to 2020 ELN Recommendations; Hochhaus et al) to 1L TKI therapy at the time of screening a. Warning is defined as: i. Six months after the initiation of treatment: BCR- ABL1IS >1-10% ii. Twelve months after the initiation of treatment: BCR- ABL1IS >0.1-1% b. Treatment failure/resistance to 1L TKI is defined as: i. BCR-ABL1IS >10% if 1L treatment duration between 6 and 12 months ii. BCR-ABL1IS >1% if 1L treatment longer than 12 months treatment: loss of MMR 7. Beyond 12 months after the initiation of to 1L TKI, a. BCR-ABL1IS > 0.1% at screening b. Intolerance is defined as: i. Non-hematologic intolerance: Patients with grade 3 or 4 toxicity while on therapy, or with persistent grade 2 toxicity, unresponsive to optimal management, including dose adjustments (unless dose reduction is not considered in the best interest of the patient if response is already suboptimal) ii. Hematologic intolerance: Patients with grade 3 or 4 toxicity (absolute neutrophil count [ANC] or platelets) while on therapy that is recurrent after dose reduction to the lowest doses recommended by manufacturer Criteria #8 is specific to the 1L patient cohort 8. Patients with newly diagnosed CML-CP (treatment with a prior TKI (imatinib, or nilotinib, or dasatinib or bosutinib) for ≤ 4 weeks is allowed)

Key Exclusion Criteria:

1. Previous treatment 1. With 2 or more ATP-binding site TKIs (for 2L patient cohort) 2. More than 4 weeks with 1-ATP-binding site TKIs (for 1L patient cohort) 2. Previous treatment with asciminib 3. Known presence of the T315I mutation at any time prior to study entry 4. Known second chronic phase of CML after previous progression to AP/BC 5. Previous treatment with a hematopoietic stem-cell transplantation 6. Patient planning to undergo allogeneic hematopoietic stem cell transplantation 7. Cardiac or cardiac repolarization abnormality, including any of the following:
• History within 6 months prior to starting study treatment of myocardial infarction (MI), angina pectoris, coronary artery bypass graft (CABG)
• Clinically significant cardiac arrhythmias (e.g., ventricular tachycardia), complete left bundle branch block, high-grade AV block (e.g., bifascicular block, Mobitz type II and third degree AV block)
• QTcF at screening ≥450 msec (male patients), ≥450 msec (female patients)
• Long QT syndrome, family history of idiopathic sudden death or congenital long QT syndrome, or any of the following:
• Risk factors for Torsades de Pointes (TdP) including uncorrected hypokalemia or hypomagnesemia, history of cardiac failure, or history of clinically significant/symptomatic bradycardia
• Concomitant medication(s) with a "Known risk of Torsades de Pointes" per www.crediblemeds.org that cannot be discontinued or replaced 7 days prior to starting study drug by safe alternative medication
• Inability to determine the QTcF interval 8. History of acute pancreatitis within 1 year of study entry or past medical history of chronic pancreatitis 9. Participation in a prior investigational study within 30 days prior to randomization or within 5 half-lives of the investigational product, whichever is longer 10. Treatment with medications that meet one of the following criteria is not allowed and should be switched to an alternative at least one week prior to the start of treatment with study treatment:
• Strong inducers of CYP3A for patients on the dose of 80 mg QD and 200mg QD
• Strong inducers and inhibitors of CYP3A for patients on the dose of 200 mg BID 11. Pregnant or nursing (lactating) women 12. Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception. Highly effective contraception for women should be maintained throughout the study and for at least 7 days after the last dose. 13. Sexually active males unwilling to use a condom during intercourse while taking study treatment and for 7 days after stopping study (only for patients treated with asciminib). 14. Severe and/or uncontrolled concurrent medical disease that in the opinion of the Investigator could cause unacceptable safety risks or compromise compliance with the protocol (e.g. uncontrolled diabetes, active or uncontrolled infection; uncontrolled arterial or pulmonary hypertension, uncontrolled clinically significant hyperlipidemia). 15. History of other active malignancy within 3 years prior to study entry with the exception of previous or concomitant basal cell skin cancer and previous carcinoma in situ treated curatively. 16. Known hypersensitivity to the study treatment.

Inclusion Criteria:

• Age >= 2 years
• Patient must have histologically confirmed primary mediastinal B-cell lymphoma (PMBCL) as defined by World Health Organization (WHO) criteria
• Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 or ECOG performance status of 3 if poor performance is related to lymphoma
• Children's Oncology Group (COG) Institutions: Use Karnofsky for patients >= 17 and < 18 years of age and Lansky for patients < 17 years of age
• Adults (age 18 or older): Creatinine clearance >= 30 mL/min, as estimated by the Cockcroft and Gault formula. The creatinine value used in the calculation must have been obtained within 28 days prior to registration. Estimated creatinine clearance is based on actual body weight
• Pediatric Patients (age < 18 years): The following must have been obtained within 14 days prior to registration:
• Measured or calculated (based on institutional standard) creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 ml/min/1.73 m^2, or
• Serum creatinine =< 1.5 x institutional upper limit of normal (IULN), or a serum creatinine based on age/gender as follows:
• Age : 2 to < 6 year; Maximum serum creatinine (mg/dL): 0.8 (male; 0.8 (female)
• Age : 6 to < 10 years; Maximum serum creatinine (mg/dL): 1 (male); 1 (female)
• Age : 10 to < 13 years; Maximum serum creatinine (mg/dL): 1.2 (male); 1.2 (female)
• Age : 13 to < 16 years; Maximum serum creatinine (mg/dL): 1.5 (male); 1.4 (female)
• Age : >= 16 years to < 18 years; Maximum serum creatinine (mg/dL): 1.7 (male); 1.4 (female)
• Patients with abnormal liver function will be eligible to enroll if the lab abnormality is thought to be due to the lymphoma or Gilbert's syndrome
• Age >= 18 years: Ejection fraction of >= 50% by echocardiogram
• Age < 18 years: Shortening fraction of >= 27% by echocardiogram, or ejection fraction of >= 50% by radionuclide angiogram
• Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial
• For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated
• Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load
• All patients and/or their parents or legal guardians must sign a written informed consent
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Exclusion Criteria:

• Administration of prior anti-cancer therapy except as outlined below:
• A short course (=< 2 weeks) of corticosteroids for the relief of lymphoma-related symptoms
• A single course of COP (cyclophosphamide, vincristine, and prednisone)
• One cycle of chemo-immunotherapy including R-CHOP, DA-EPOCH-R, a pediatric mature B-cell non-Hodgkin lymphoma (B-NHL) induction therapy (such as ANHL1131), or intrathecal chemotherapy that has not started more than 21 days prior to enrollment
• Active ischemic heart disease or heart failure
• Active uncontrolled infection
• Central nervous system (CNS) involvement of lymphoma
• Previous cancer that required systemic chemotherapy and/or thoracic radiation. Other cancers will be permitted if in remission x 3 years
• Active autoimmune disease that has required systemic treatment (such as disease modifying agents, corticosteroids, or immunosuppressive agents) in the past 2 years. Replacement therapy such as thyroxine, insulin or physiologic corticosteroid for adrenal or pituitary insufficiency is not considered a form of systemic treatment
• In patients < 18 years of age hepatitis B serologies consistent with past or current infections
• Patients with severe hepatic impairment (Child-Pugh class C or serum total bilirubin > 5.0 mg/dL) unless thought to be due to lymphoma or Gilbert's syndrome
• Female patients who are pregnant since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test is required for female patients of childbearing potential
• Sexually active patients of reproductive potential who have not agreed to use a highly effective contraceptive method (failure rate of < 1% per year when used consistently and correctly) for the duration of their study participation
• Lactating females are not eligible unless they have agreed not to breastfeed their infants starting with the first dose of study therapy and for at least 6 months after the last dose of rituximab

Inclusion Criteria:

• >= 15 and < 40 years at time of diagnosis
• Newly diagnosed B-ALL, T-ALL, lymphoblastic lymphoma (LLy), or mixed-phenotype acute leukemia/lymphoma (MPAL)
• Note: Philadelphia chromosome (PH)+ and PH-like acute leukemia are eligible (use of tyrosine kinase inhibitors [TKI] or CRLF2- targeted concomitant medication must be documented, if used)
• Conjugated bilirubin =< 1.5 x upper limit of normal (ULN) for age, regardless of baseline bilirubin (within 7 days prior to enrollment), and
• Serum glutamate pyruvate transaminase (SGPT) (ALT) =< 225 U/L (=< 5x ULN) (within 7 days prior to enrollment), and
• Note: For the purpose of this study, the ULN for SGPT (ALT) has been set to the value of 45 U/L and serum glutamic oxaloacetic transaminase (SGOT) (AST) to 50 U/L regardless of baseline
• SGOT (AST) =< 250 U/L (=< 5x ULN) (within 7 days prior to enrollment)
• Note: For the purpose of this study, the ULN for SGPT (ALT) has been set to the value of 45 U/L and SGOT (AST) to 50 U/L regardless of baseline
• Berlin-Frankfurt-Munich (BFM), Children's Oncology Group (COG), or C10403-based Induction regimen and must be inclusive of >= 1 dose of pegaspargase or calaspargase pegol, and
• First dose of asparaginase must be planned within the first week of induction therapy, and
• Dose of pegaspargase or calaspargase pegol must be >= 1,000 IU/ m^2 (dose-capping permitted per primary regimen)
• Note: Co-enrollment on a therapeutic consortia trial is not required
• All patients and/or their parents or legal guardians must sign a written informed consent
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Exclusion Criteria:

• Down syndrome
• Known inherited or autoimmune liver disease impacting conjugated bilirubin (e.g., Alagille syndrome, primary sclerosing cholangitis, other)
• Known biopsy (or imaging) proven severe liver fibrosis (Batts-Ludwig >= stage 3)
• Patients who received chemotherapy or treatment for a prior malignancy are not eligible
• The following are permitted: steroid prophase, hydroxyurea, or other cytoreduction prior to initiation of Induction chemotherapy (must be documented) and chemotherapy for current diagnosis (i.e. initiation of Induction therapy within enrollment window). Chemotherapy prior to enrollment for treatment of a non-malignancy (e.g., steroid or methotrexate for autoimmune disease) is also permitted and must be documented
• Female patients who are pregnant since fetal toxicities and teratogenic effects in humans are unknown for study drug. A pregnancy test is required for female patients of childbearing potential
• Lactating females who plan to breastfeed their infants
• Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation

Inclusion Criteria:

• Patients must be 1 month to < 6 years old at the time of study enrollment and must have had initial diagnosis of leukemia at < 2 years old.
• Patients must have KMT2A-rearranged acute lymphoblastic leukemia (ALL), acute leukemia of ambiguous lineage (ALAL), or mixed phenotype acute leukemia (MPAL), which is determined to be refractory or in first marrow relapse. All patients must undergo cytogenetics and fluorescence in situ hybridization (FISH) testing of a relapsed/refractory blast sample at a Children's Oncology Group (COG)-approved laboratory for KMT2A-R status determination and the presence of a KMT2A- rearrangement must be confirmed by central review. Cytogenetics results must be submitted for central review by Day 10 of protocol therapy, for confirmation of KMT2A-R status. Patients enrolled with refractory disease may utilize initial diagnostic cytogenetics for eligibility and submission for central review if testing was performed at a COG approved laboratory. Patients will be eligible to remain on protocol therapy if KMT2A-R is confirmed by central review. Additional methods of assessing for KMT2A-R may be considered if FISH does not detect the rearrangement.
• Disease status at time of enrollment must be one of the following:
• First relapse: Any recurrence of marrow disease, with or without other extramedullary sites(s), at any point after achieving remission. ("Remission-1", per definition below) meeting one of these criteria:
• Relapse M1: M1 morphology (< 5% blasts) + at least 2 confirmatory tests showing >= 1% blasts (testing includes flow, cytogenetics, polymerase chain reaction [PCR]ext-generation sequencing [NGS] of immunoglobulin [Ig]/T-cell receptor [TCR] rearrangement, and/or PCR or NGS of fusion gene identical to diagnosis), OR
• Relapse M2: M2 morphology (5-25% blasts) + 1 confirmatory test showing > 1% blasts, OR
• Relapse M3: M3 morphology (> 25% blasts)
• Refractory, or failure to achieve Remission-1: Remission-1 is defined as < 1% marrow blasts by flow minimal residual disease (MRD) and resolution of extramedullary disease by the end of Consolidation, or 2 courses of frontline chemotherapy.
• Central Nervous System (CNS) disease: Patients must have CNS1 or CNS2 status and no clinical signs or neurologic symptoms suggestive of CNS leukemia, such as cranial palsy.
• Patients with CNS3 disease may receive antecedent intrathecal chemotherapy to achieve CNS1 or CNS2 status prior to enrollment.
• Patients with a history of CNS chloromatous disease are required to have no radiographic evidence of CNS disease prior to enrollment.
• White blood cell (WBC) must be < 50,000/uL at the time of study enrollment. Patients can receive cytoreduction with hydroxyurea and/or corticosteroids for up to 7 days prior to enrollment.
• Patients >= 12 months of age must have a performance status by Lansky Scale of >= 50%.
• Patients must be able to take enteral medications. Acceptable routes of administration for SNDX-5613 include: oral (PO), nasogastric (NG) tube, nasojejunal (NJ) tube, nasoduodenal (ND), and gastrostomy tube (G-tube).
• Patients must have fully recovered from the acute toxic effects of all prior chemotherapy, immunotherapy, or radiotherapy prior to entering this study
• Cytotoxic chemotherapy or other anti-cancer agents known to be myelosuppressive:
• >= 14 days must have elapsed after the completion of other cytotoxic therapy, including patients who relapse during pre-Maintenance upfront therapy, with these specific exceptions: cytoreduction with hydroxyurea and/or corticosteroids, and intrathecal chemotherapy, which have no required washout periods. For patients who relapse during upfront Maintenance therapy, >= 7 days must have elapsed after the last dose of chemotherapy. Additionally, patients must have fully recovered from all acute toxic effects of prior therapy.
• NOTE: Cytoreduction with hydroxyurea and/or corticosteroids is permitted prior to enrollment for patients with WBC >= 50,000/uL, and by provider discretion regardless of WBC, to reduce potential risk of differentiation syndrome with SNDX-5613 initiation. Hydroxyurea and/or corticosteroids may be given for up to 7 days, with no wash-out required.
• NOTE: No waiting period is required for patients having received intrathecal cytarabine, methotrexate, and/or hydrocortisone. Intrathecal chemotherapy that is given up to 7 days prior to the initiation of protocol therapy counts as protocol therapy and not prior anti-cancer therapy. Intrathecal chemotherapy given > 7 days prior does not count as protocol therapy.
• NOTE: Prior exposure to fludarabine and cytarabine (FLA) is permitted.
• Anti-cancer agents not known to be myelosuppressive (e.g., not associated with reduced platelet or absolute neutrophil count [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. There is an exception for blinatumomab infusions, for which patients must have been off for at least 3 days and all drug related toxicity must have resolved to grade 2 or lower as outlined in the inclusion/exclusion criteria.
• 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 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
• Stem cell infusions (with or without total body irradiation (TBI):
• Allogeneic (non-autologous) bone marrow or stem cell transplant, or stem cell boost: >= 84 days after infusion
• Donor leukocyte infusion: >= 28 days
• Cellular Therapy: >= 28 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; >= 84 days after TBI, craniospinal XRT or if radiation to >= 50% of the pelvis; >= 42 days if other substantial bone marrow radiation.
• A serum creatinine based on age as follows:
• Age 1 month to < 6 months: maximum serum creatinine 0.4 mg/dL
• Age 6 months to < 1 year: maximum serum creatinine 0.5 mg/dL
• Age 1 to < 2 years: maximum serum creatinine 0.6 mg/dL
• Age 2 to < 6 years: maximum serum creatinine 0.8 mg/dL OR
• a 24-hour urine Creatinine clearance >= 70 mL/min/1.73 m^2 OR
• a glomerular filtration rate (GFR) >= 70 mL/min/1.73 m^2. GFR must be performed using direct measurement with a nuclear blood sampling method OR direct small molecule clearance method (iothalamate or other molecule per institutional standard).
• NOTE: Estimated GFR (eGFR) from serum creatinine, cystatin C or other estimates are not acceptable for determining eligibility.
• A direct bilirubin =< 1.5 x upper limit of normal (ULN) for age, unless disease related
• Serum glutamic-pyruvic transaminase (SGPT) (alanine aminotransferase [ALT]) =< 135 U/L (3 x ULN) unless disease related.
• Note: For the purpose of eligibility, the ULN for SGPT (ALT) has been set to the value of 45 U/L
• Shortening fraction of >= 27% by echocardiogram, or ejection fraction of >= 50% by radionuclide angiogram.
• Corrected QT interval using Fridericia formula (QTcF) of < 450 msec (using the average of triplicate measurements)
• NOTE: There are no specific electrolyte parameters for eligibility. However, it should be noted that, to limit QTc prolongation risk, patients must maintain adequate potassium and magnesium levels to initiate and continue SNDX-5613 on protocol therapy.
• Patients must be able to comply with the safety monitoring requirements of the study, in the opinion of the treating investigator.

Exclusion Criteria:

• Patients with isolated extramedullary leukemia.
• Patients diagnosed with Down syndrome.
• Patients known to have one of the following syndromes:
• Bloom syndrome, ataxia-telangiectasia, Fanconi anemia, Kostmann syndrome, Shwachman syndrome, or any other known bone marrow failure syndrome.
• Patients with a secondary KMT2A-R leukemia that developed after treatment of prior malignancy with cytotoxic chemotherapy.
• Patients with a history of congenital prolonged QT syndrome, congestive heart failure or uncontrolled arrhythmia in the past 6 months prior to study enrollment.
• Patients with an active, uncontrolled infection, further defined below:
• Positive bacterial blood culture within 48 hours of study enrollment
• Fever above 38.2 degrees Celsius (C) within 48 hours of study enrollment with clinical signs of infection. Fever that is determined to be due to tumor burden is allowed if patients have documented negative blood cultures for at least 48 hours prior to enrollment and no concurrent signs or symptoms of active infection or hemodynamic instability
• A positive fungal culture within 30 days of study enrollment or active therapy for presumed invasive fungal infection
• Patients may be receiving IV or oral antibiotics to complete a course of therapy for a prior documented infection as long as cultures have been negative for at least 48 hours and signs or symptoms of active infection have resolved. For patients with Clostridium (C.) difficile diarrhea, at least 72 hours of antibacterial therapy must have elapsed and stools must have normalized to baseline
• Active viral or protozoal infection requiring IV treatment
• Human immunodeficiency virus (HIV)-infected patients are eligible if on effective anti-retroviral therapy that does not interact with planned study agents and with undetectable viral load within 6 months of enrollment.
• Patients with active acute graft-versus-host disease (GVHD) > grade 0 (unless skin only), or chronic GVHD > mild (unless skin only) are not eligible. Patients with acute or chronic skin GVHD that is =< grade 1, or chronic skin GVHD that is graded as mild are eligible.
• Patients who have received a prior solid organ transplantation.
• Patients with known Charcot-Marie-Tooth disease, if treating on Regimen A (with vincristine).
• CYP3A4 Inhibitors or Inducers: Patients who require concomitant therapy with moderate or strong CYP3A4 inhibitors or inducers, as these are prohibited during the chemotherapy combination cycles. These agents should be discontinued at least 5 half-lives prior to starting protocol therapy. Concomitant use of strong CYP3A4 inhibitor -azole antifungals are permitted during the SNDX-5613 monotherapy cycles, with appropriate SNDX-5613 dose modification.
• P-glycoprotein (P-gp) inhibitors or inducers: Vincristine is a substrate for P-gp. Concomitant use of P-gp inhibitors or inducers with vincristine (patients receiving Regimen A Cycle 1) should be avoided.
• Investigational Drugs: Patients who are currently receiving another investigational drug.
• Anti-cancer Agents: Patients who are currently receiving other anti-cancer agents (exceptions: hydroxyurea and corticosteroids, which may be used as cytoreduction prior to enrollment).
• Anti-GVHD Agents: Patients who are receiving cyclosporine, tacrolimus, or other systemic agents to treat graft-versus-host disease post bone marrow transplant. Patients should discontinue anti-GVHD agents > 7 days prior to enrollment and have no evidence of worsening GVHD. Topical steroids are permitted.
• Patients who have previously been treated with SNDX-5613. Prior exposure to other menin inhibitors is permitted.
• All patients and/or their parents or legal guardians must sign a written informed consent.
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met.

Main Inclusion Criteria:

• Diagnosis of primary AML or AML with myelodysplasia-related changes (AML-MRC)
• Patient is in first or second relapse or has refractory disease. Patients must have had histologic verification of AML at the original diagnosis.
• Patient must be positive for the following FLT3 mutations in bone marrow or PB: FLT3 internal tandem duplication (ITD), FLT3 tyrosine kinase domain (TKD) D835 or I836 or FLT3-ITD and specified FLT3-TKD.
• ECOG performance status 0-2
• Life expectancy of at least 3 months in the opinion of the investigator.
• Normal hepatic and renal function.
• Patient is able to swallow oral medications.
• Female patients are postmenopausal, documented as surgically sterile, use two methods of contraception or practice true abstinence and have a negative urine pregnancy test at screening.
• Male patients even if surgically sterilized agree to practice true abstinence or use highly effective barrier contraception.

Main Exclusion Criteria:

• Diagnosis of acute promyelocytic leukemia.
• Known BCR-ABL-positive leukemia.
• AML secondary to prior chemotherapy for other neoplasms (except for MDS).
• AML that has relapsed after or is refractory to more than 2 lines of therapy.
• Clinically active central nervous system leukemia or prior history of NCI CTCAE Grade ≥ 3 drug-related CNS toxicity.
• Major surgery or radiation therapy within 4 weeks prior to the first study dose.
• Prior treatment with iadademstat or FLT3 inhibitors (except sorafenib or midostaurin used in first line as part of induction).
• Patients not eligible to receive gilteritinib per label.
• Prior treatment with 3 or more lines of AML therapy.
• Treatment with any investigational products within 3 weeks prior to first dose of study treatment.
• Uncontrolled hypertension or poorly controlled diabetes.
• Evidence of active uncontrolled viral, bacterial, or systemic fungal infection.
• Pregnant or lactating women.