• Histologically or cytologically-confirmed Ewing sarcoma, rhabdomyosarcoma, neuroblastoma, or osteosarcoma
• Disease progression after prior therapy in locally advanced or metastatic setting
• Measurable or evaluable disease based on the Response Evaluation Criteria in Solid Tumors (RECIST v1.1) criteria
• Age 12 months to <21 years
• Adequate bone marrow reserves, hepatic function, and renal function
• Recovered from effects of any prior surgery or cancer therapy
• Patients 18 years or older will provide written consent. A parent or legal guardian of a patient <18 years of age will provide informed consent and patients 11 to 18 years of age will provide written assent or as per participating institutional policy.
• Clinically significant gastrointestinal disorders
• NYHA Class III or IV congestive heart failure, ventricular arrhythmias or uncontrolled blood pressure
• Active infection or unexplained fever
• Known hypersensitivity to any of the components of MM-398 or other liposomal products
• Recent Investigational therapy
• Pregnant or breast feeding; females of child-bearing potential must test negative for pregnancy at the time of enrollment

PARTICIPANT INCLUSION CRITERIA To be eligible for study participation, an individual must meet all of the following criteria: 1. Ability to understand, and willingness and ability to read and sign, the informed consent form. 2. Ability to understand and follow instructions and study procedures. 3. Willingness to comply with all study procedures and be available for the duration of the study. 4. Ability to take oral medication, and are willing to adhere to study medication regimen. 5. Age 18 years or older. 6. Diagnosed with HZO in one eye based on both of these criteria: 1. History of characteristic unilateral vesicular rash in the dermatomal distribution of cranial nerve V1. 2. Medical record documentation of an episode of active dendriform epithelial keratitis, stromal keratitis, endothelial keratitis, and/or iritis due to HZO within the preceding year. This episode of active anterior segment ocular disease may be due to HZO of recent onset (within the preceding 6 months); or chronic HZO (with onset six or more months ago); may be new, worsening, or recurrent disease after a period of inactivity; and may occur after medication was reduced. i. Study participants with chronic HZO must be on a stable treatment regimen and off antivirals for at least 30 days before enrollment. Study participants with chronic HZO who do not meet this criterion may be rescreened, if they are able to meet this criterion within 3 months after the study visit. (This is not a requirement for study participants with recent onset HZO, who may be enrolled at any time, preferably after completing recommended acute antiviral treatment, if prescribed, is completed). 7. For females with reproductive potential, willingness to use highly effective contraception (e.g., hormonal contraception, barrier contraception, intrauterine device, or abstinence). PARTICIPANT EXCLUSION CRITERIA An individual who meets any of the following criteria will be excluded from participation in this study: 1. History of immunocompromised status as defined by current CDC contraindications for the vaccine against zoster (44). 1. Study participants who are diagnosed with leukemia, lymphomas or other malignant neoplasms affecting bone marrow or lymphatic system, unless leukemia in remission and off chemotherapy for at least 3 months. 2. Study participants who are diagnosed with Acquired Immune Deficiency Syndrome (AIDS) or presents with other clinical manifestations of Human Immunodeficiency virus (HIV) including CD4 count of ≤ 200 cells/ml. 3. Study participants on immunosuppressive therapy including: i. High-dose corticosteroids (greater than equivalent of prednisone 20 mg/day within 1 month) ii. Chemotherapy, other than low dose used for treatment of immune-mediated diseases within 3 months iii. Study participants receiving recombinant human immune mediators and immune modulators, especially antitumor necrosis agents, within 1 month prior to enrollment d. Study participants with unspecified cellular immunodeficiency. e. Study participants with history of hematopoietic stem cell transplantation. 2. Medical history of a systemic disease and thought likely to meet one of the exclusion criteria listed in exclusion criterion #1 during the 18-month study period. 3. Renal insufficiency: 1. Requires dialysis or has history of renal transplant or 2. eGFR less than 45, determined within 30 days preceding enrollment. 4. Allergy or adverse reaction to valacyclovir or acyclovir. 5. History of vaccination against zoster within one month prior to enrollment. Study participants who meet this exclusion criterion may be rescreened. 6. Keratoplasty or keratorefractive surgery of the involved eye with zoster. 7. On systemic antivirals with activity against herpes within the past 30 days, including acyclovir, valacyclovir, or famciclovir, for any reason except for treatment of acute HZO, including investigational drug trial. 8. History of another condition that may require treatment with one of these three antivirals listed above in exclusion criterion #7, during the course of the study; study participants who require chronic suppressive antiviral treatment with these medications will be excluded. 9. Sexually active women who are pregnant, nursing, or in their reproductive years who do not agree to use contraception during the 1-year treatment period. 10. Incarceration 11. Any condition or circumstance that in the opinion of the study investigator, would place the study participant in increased risk or affect his/her full compliance or completion of the study. 12. Participation in a clinical study testing a drug, biologic, device or other intervention within the last 30 days from enrollment visit. Study participants who meet this criterion may be rescreened.

Who have experienced a progressive deterioration in their vision, such thot they can no longer achieve adequate functional vision on a daily basis with their contact lenses or spectacles; Who are 21 years of age or older; Who have clear central corneas; Who have a corneal thickness of 450 microns or greater at the proposed incision site; Who have corneal transplantation as the only remaining option to improve their functional vision. Who have abnormally thin corneas or who have a corneal thickness of 449 microns or less at the proposed incision site; Patients with collagen vascular, autoimmune or immunodeficiency disease; Pregnant or nursing patients; Presence of ocular conditions, such as recurrent corneal erosion syndrome or corneal dystrophy, that my predispose the patient to future complications; Patients who are taking on or more of following medications: isotretinoin (Accutane); amiodarone HCL (Cordarone).

• Subject has dry chronic tympanic membrane perforation (CTMP) documented as persisting longer than 3 months.
• A female subject is eligible to participate if she is not pregnant and at least one of the following conditions applies:
• Not a woman of childbearing potential (WOCBP) OR
• WOCBP who agrees to follow the contraceptive guidance starting at screening and for at least 28 days after investigational product (IP) application on Day 1.
• Female subject must agree not to breastfeed starting at drug application on Day 1 and for at least 28 days after IP application.
• Female subject must not donate ova starting on Day 1 and for at least 28 days after investigational product (IP) application.
• A male subject with female partner(s) of child-bearing potential must agree to use contraception starting on Day 1 and for at least 28 days after IP application.
• A male subject must not donate sperm starting on Day 1 and for at least 28 days after IP application.
• Male subject with a pregnant or breastfeeding partner(s) must agree to remain abstinent or use a condom from Day 1 and for at least 28 days after IP application.
• Subject must be willing and able to comply with the study requirements including prohibited concomitant medication restrictions.
• Subject agrees not to participate in another interventional study while receiving IP.
• Subject has one of following conditions that may affect the ipsilateral side of the ear with chronic tympanic membrane perforation (CTMP):
• Perforation involving 3 or more quadrants.
• Pin hole perforation (only for the expansion cohort).
• Presence of tympanosclerosis adjacent to the perforation.
• Perforation involves malleus erosion.
• Absent malleus.
• Marginal perforation (i.e., involving the annulus or exposing the handle of malleus).
• Tympanic membrane perforation (TMP) caused by electric/slag/blast/burn injury.
• Post radiated TMP.
• History of tympanic membrane repair by any type of live tissue.
• History of otorrhea or active treatment for otorrhea within the last 3 months prior to Screening.
• Bellucci otorrhea grade 3 or above.
• Active external ear canal inflammation (otitis externa, dermatitis) or within the last 3 months prior to Screening.
• Active diagnosis of Eustachian Tube dysfunction or diagnosis within 6 months prior to Screening.
• Craniofacial abnormalities, History of head and neck surgery within the last 3 months prior to Screening, history of radiation to head and neck.
• Recent (within 2 weeks) diagnosis of upper respiratory tract infection.
• Presence or history of cholesteatoma.
• Presence of pars-flaccida or pars tensa retraction or adhesion.
• Presence or history of tumors of the middle or external ear.
• Contraindications to tympanic membrane closure.
• An audiometric finding indicates a characteristic of Carhart's notch which is an increase in bone conduction threshold with a peak at 2,000 Hz.
• Only hearing or better hearing ear.
• Whole circumference of the tympanic membrane perforation is not visible by endoscope.
• Presence/history of eosinophilic otitis media in either ear.
• Subject has a presence of adhesive otitis media in the contralateral ear.
• Subject has a presence of any wound healing systemic condition.
• Subject has Obstructive Sleep Apnea where the subject is required to use Continuous Positive Airway Pressure (CPAP) during the study period.
• Subject is exposed in their daily life to high volume of water into the ear canal (e.g., swimmer or surfer).
• Subject has health conditions that would prevent him/her from fulfilling the study requirements on the basis of medical history and laboratory test (Serum Chemistries, complete blood count [CBC] with Differential, Urinalysis) results at the screening visit.
• Subject is receiving any other investigational agents during study participation.
• Subject has any form of substance abuse, or psychiatric illness/social situations that would limit compliance with study requirements, or a condition that could invalidate communication.
• Subject has a known or suspected hypersensitivity to ASP0598, or any components of the formulation used.
• Subject has had previous exposure with ASP0598.
• Subject is unlikely to comply with the visits scheduled in the protocol.

• Age greater than or equal to 1 month and less than or equal to 12 months at the time of randomization; AND
• Positive congenital CMV by urine culture or polymerase chain reaction test(PCR), OR saliva culture or PCR followed by confirmatory urine PCR by 21 days of age, OR urine culture or PCR after 21 days of age followed by newborn dry blood spot PCR; AND
• Confirmed sensorineural hearing loss (SNHL) by auditory brainstem response (ABR) testing. For ABR assessments, hearing loss is defined as levels greater than 25 dB normal hearing levels (NHL) at 1, 2, or 4 kHz in one or both ears.
• Imminent demise; OR
• Known hypersensitivity reaction to valganciclovir, ganciclovir, or any components of the investigational product formulation; OR
• ALT (Alanine Aminotransferase) five times baseline U/L, hepatomegaly, or significant gastrointestinal disorders (e.g., eosinophilic esophagitis, ulcerative colitis); OR
• Absolute neutrophil count (ANC) less than 500 cells/mm^3, Hemoglobin less than 8 g/dL, or platelets less than 50,000/mm^3, splenomegaly, or significant hematologic disorders (e.g., hemophilia, leukemia, sickle cell anemia); OR
• Creatinine clearance less than 60 mL/min/1.73m^2 or significant renal disorders (e.g., nephrotic syndrome); OR
• Receiving other antiviral medications or immune globulin therapy; OR
• Receiving other investigational drugs; OR
• Breast feeding from a mother receiving antiviral or immunosuppressive medication; OR
• Known HIV positive mother (risk of immunosuppression); OR
• Subject is currently using list of prohibited medication specified by the package insert; OR
• Other known cause contributing to SNHL (e.g., meningitis, aminoglycoside ototoxicity); OR
• Bilateral profound SNHL or auditory neuropathy spectrum disorder; OR
• Existing conductive hearing loss or mixed permanent hearing loss is present; OR
• Evidence of intracranial calcification; OR
• Evidence of hydrocephalus; OR
• Microcephaly; OR
• Presence of petechiae; OR
• Intrauterine growth retardation; OR
• Chorioretinitis, optic atrophy or pale optic nerves; OR
• Parent or guardian unable to speak English or Spanish; OR
• Subject exposed to a language other than English or Spanish a majority of the time; OR
• Subject unable to complete hearing assessments or parent/guardian unable to complete communication questionnaires; OR
• < 32 weeks gestational age at birth; OR
• Weight at the time of birth < 1800 g.

Inclusion Criteria 1. Biopsy-proven non-hematopoietic malignancy, except for small cell lung cancer, germ cell cancer, or unknown primary tumor. 2. Radiographic evidence by MRI (or by CT scan with CT contrast if ineligible or intolerant of MRI) of brain metastasis. (If patient is unable to tolerate MRI contrast, an MRI without contrast is acceptable if lesions are visible) 3. All brain metastases must be outside the brain stem (midbrain, pons and medulla). 4. Patient must have 10 or less brain metastases. 5. The maximum diameter of any lesion must be less than or equal to 3.0 cm. 6. Previous treatment with surgery, radiation, chemotherapy, immunotherapy or any targeted agents are allowed provided that:
• Radiation was not to the brain.
• Surgery to the brain was > 7 days prior to SRS and there remains at least one additional brain metastasis that can be targeted with SRS 7. Age ≥ 18 years. 8. ECOG Performance Score of 2 or better/Karnofsky Performance Status score of 50-60 or better. 9. All men, as well as women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. 10. A female of child-bearing potential is any woman (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria:
• Has not undergone a hysterectomy or bilateral oophorectomy; or
• Has not been naturally postmenopausal for at least 12 consecutive months (i.e., has had menses at any time in the preceding 12 consecutive months). 11. Ability to understand and the willingness to sign a written informed consent. Exclusion Criteria 1. Patients had craniotomy and surgery to the brain within 7 days from the date of SRS. 2. Patients with leptomeningeal metastasis. NOTE: For the purposes of exclusion, LMD is a clinical diagnosis, defined as positive CSF cytology and/or equivocal radiologic or clinical evidence of leptomeningeal involvement. Patients with leptomeningeal symptoms in the setting of leptomeningeal enhancement by imaging (MRI) would be considered to have LMD even in the absence of positive CSF cytology, unless a parenchymal lesion can adequately explain the neurologic symptoms and/or signs. In contrast, an asymptomatic or minimally symptomatic patient with mild or nonspecific leptomeningeal enhancement (MRI) would not be considered to have LMD. In that patient, CSF sampling is not required to formally exclude LMD, but can be performed at the investigator's discretion based on level of clinical suspicion. 3. Patients with a contraindication to both MRI (with or without contrast) and CT scan (with contrast) 4. Patients with life expectancy < 3 months. 5. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that, in the opinion of the investigator, would limit compliance with study requirements. 6. Subjects must not be pregnant or nursing at the time of SRS treatment due to the potential for congenital abnormalities and the potential of this regimen to harm nursing infants.

• 2 to 21 years of age
• Have a visually significant cataract or need IOL replacement surgery
• Compromised capsular bag prohibiting implantation of standard posterior IOL
• Subject or parent/guardian must be able to comply with visit schedule and study requirements
• Subject's legal representative must be able to sign the Informed Consent
• Under 2 years of age
• Unable to meet Postoperative evaluation requirements
• No useful vision or vision potential in fellow eye
• Mentally retarded patients
• History of corneal disease
• Abnormality of the iris or ocular structure
• ACD less than 3.2 mm
• Uncontrolled glaucoma
• IOP > 25 mmHg
• Chronic or recurrent uveitis
• Preexisting macular pathology that may complicate the ability to assess the benefit of this lens
• Retinal detachment or family history
• Retinal disease that may limit visual potential
• Optic nerve disease that may limit visual potential
• Diabetes mellitus
• Pregnant, lactating or plan to become pregnant

Inclusion: 1. Histologically confirmed relapsed or refractory solid tumor as follows:
• For dose escalation and dose determination parts: Histologically confirmed relapsed or refractory solid tumor (including CNS tumors but not lymphomas). Patients with Diffuse Intrinsic Pontine Glioma do not require histological only radiographic confirmed relapse to enroll.
• For dose expansion and tumor specific cohorts: Histologically confirmed relapsed or refractory solid tumor including but not limited to EWS, rhabdoid tumor, rhabdomyosarcoma, neuroblastoma, and medulloblastoma. Patients with Diffuse Intrinsic Pontine Glioma do not require histological only radiographic confirmed relapse to enroll. EWS is not eligible for TOPO and CTX tumor-specific cohorts. 2. Age ≥2 and <21 years at the time of study entry. 3. Lansky performance status ≥50% for patients ≤16 years of age, or Eastern Cooperative Oncology Group (ECOG) 0, 1 or 2 for patients >16 years of age. 4. Adequate bone marrow function.
• Absolute neutrophil count ≥1000/mm3;
• Platelet count ≥100,000/mm3 (transfusion independent);
• Hemoglobin ≥8.5 g/dL (transfusion allowed). 5. Adequate renal function: Serum creatinine level based on age/gender must within protocol specified limits. 6. Adequate liver function, including:
• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × upper limit of normal (ULN) or ≤5 × ULN for age, if attributable to disease involvement of the liver;
• Total bilirubin ≤1.5 × ULN for age. 7. Measurable disease as defined by RECIST version 1.1 or modified RANO criteria for CNS disease or INRC for neuroblastoma. 8. Recovered to CTCAE Grade ≤1, or to baseline, from any non-hematological acute toxicities of prior surgery, chemotherapy, immunotherapy, radiotherapy, differentiation therapy or biologic therapy, with the exception of alopecia. 9. Serum/urine pregnancy test (for all girls ≥8 years of age) negative at screening and at the baseline visit. 10. Evidence of a personally signed and dated informed consent document indicating that the patient or a legally acceptable representative/parent(s)/legal guardian of minors, has been informed of all pertinent aspects of the study. Minor study patients also must provide age appropriate assent according to the local guidelines, where applicable. 11. Willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other procedures. Exclusion: 1. For palbociclib with IRN and TMZ combination, prior treatment with a CDK4/6 inhibitor or progression while on treatment with an IRN-containing regimen that includes TMZ. Patients who have received the combination of IRN and TMZ and did not progress while on these medications are eligible. For patients enrolling in the palbociclib with TOPO and CTX combination, prior treatment with a CDK4/6 inhibitor or progression while on treatment with a TOPO-containing regimen that includes CTX. Patients who have received the combination of TOPO and CTX and did not progress while on these medications are eligible. 2. Prior intolerability to IRN and/or TMZ, for palbociclib with IRN and TMZ combination and prior intolerability to TOPO and/or CTX for palbociclib with TOPO and CTX combination. 3. Use of strong cytochrome P450 (CYP) 3A inhibitors or inducers. Patients who are receiving strong uridine diphosphate-glucuronosyl transferase 1A1 (UGT1A1) inhibitors within 12 days of Cycle 1 Day 1 (C1D1) are not eligible for the palbociclib with IRN and TMZ combination. Patients who are receiving strong UGT1A1 inhibitors within 12 days of C1D1 are eligible for the palbociclib with TOPO and CTX combination (See Section 5.7.1 for list of products.) 4. Prior growth factors (including filgrastim) within 7 days before study entry or PEG-filgrastim within 14 days before study entry. 5. Radiation therapy within 14 days before study entry. 6. Systemic anti cancer therapy within 2 weeks prior to study entry and 6 weeks for nitrosoureas. 7. Previous high dose chemotherapy requiring stem cell rescue within 90 days or persistent AE >Grade 1. 8. Prior irradiation to >50% of the bone marrow (see Appendix 9). 9. Participation in other studies involving investigational drug(s) within 2 weeks or 5 half lives, whichever is longer, prior to study entry. 10. Major surgery within 4 weeks prior to study entry. Surgical biopsies or central line placement are not considered major surgeries. 11. Known or suspected hypersensitivity to palbociclib, IRN and/or TMZ. 12. Patients with known symptomatic brain tumors or brain metastases and require steroids, unless they have been on a stable or on a decreasing steroid dose for >14 days. 13. Patients with previously diagnosed brain metastases are eligible if they have completed their prior treatment and have recovered from the acute effects of radiation therapy or surgery prior to study entry for these metastases for at least 14 days post radiation and 4 weeks post-surgery and are neurologically stable. 14. Hereditary bone marrow failure disorder. 15. QTc >470 msec. 16. History of clinically significant or uncontrolled cardiac disease, including:
• History of or active congestive heart failure; if patient had congestive heart failure resolve and >1 year from resolution, patient will be considered eligible;
• Clinically significant ventricular arrhythmia (such as ventricular tachycardia, ventricular fibrillation or Torsades de Pointes);
• Diagnosed or suspected congenital or acquired prolonged QT syndrome;
• Need for medications known to prolong the QT interval;
• Uncorrected hypomagnesemia or hypokalemia because of potential effects on the QT interval;
• Left ventricular ejection fraction <50% or shortening fraction <28%. 17. Recent or ongoing clinically significant gastrointestinal disorder that may interfere with absorption of orally administered drugs (eg, gastrectomy). 18. Evidence of serious active or uncontrolled bacterial, fungal or viral infection or known history of hepatitis B virus, hepatitis C virus, or human immunodeficiency virus infection or acquired immunodeficiency syndrome-related illness. 19. Other severe acute or chronic medical or laboratory test abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results, and in the judgment of the Investigator, would make the patient inappropriate for entry into this study. 20. Investigator site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, or patients who are Pfizer employees, including their family members, directly involved in the conduct of the study. 21. Fertile male patients and female patients of childbearing potential who are unwilling or unable to use a highly effective method of contraception as outlined in this protocol for the duration of the study and for at least 90 after the last dose of investigational product.

• Patients must have a body surface area (BSA) of >= 0.5 m^2 at enrollment
• Patients must have neurofibromatosis type 1 (NF1) based on clinical criteria and/or germline genetic testing
• Patients must be newly diagnosed or have previously diagnosed NF-1 associated LGG that has not been treated with any modality other than surgery
• For patients with optic pathway gliomas (OPGs):
• Newly-diagnosed patients with OPG are eligible if there are neurologic symptoms (including visual dysfunction, as defined below) or other exam findings associated with the tumor
• Previously-diagnosed patients with OPG are eligible if they have new or worsening neurologic symptoms (including visual dysfunction, as defined below) or have tumor growth
• For both newly-diagnosed and previously-diagnosed OPG, the patient may be eligible, irrespective of whether there has been tumor growth or other neurological symptoms or worsening, if they meet at least one of the following visual criteria:
• Visual worsening, defined as worsening of visual acuity (VA) or visual fields (VF) documented within the past year (by examination or history); OR
• Significant visual dysfunction (defined as VA worse than normal for age by 0.6 logMAR [20/80, 6/24, or 2.5/10] or more in one or both eyes)
• For patients with LGG in other locations (i.e., not OPGs):
• Newly-diagnosed patients with LGG are eligible if there are neurologic symptoms or other exam findings associated with the tumor
• NOTE: Newly-diagnosed patients with LGG without associated neurologic symptoms or exam findings are not eligible
• Previously-diagnosed patients with LGG are eligible if they have new or worsening neurologic symptoms or have tumor growth
• Although not required, if a biopsy/tumor resection is performed, eligible histologies will include all tumors considered LGG or low-grade astrocytoma (World Health Organization [WHO] grade I and II) by 5th edition WHO classification of central nervous system (CNS) tumors with the exception of subependymal giant cell astrocytoma
• Patients must have two-dimensional measurable tumor >= 1 cm^2
• Patients with metastatic disease or multiple independent primary LGGs are allowed on study
• Creatinine clearance or radioisotope glomerular filtration Rate (GFR) >= 70 mL/min/1.73 m^2 OR a serum creatinine based on age/gender within 7 days prior to enrollment as follows:
• Age; maximum serum creatinine (mg/dL)
• 2 to < 6 years; 0.8 (male) and 0.8 (female)
• 6 to < 10 years; 1 (male) and 1 (female)
• 10 to < 13 years; 1.2 (male) and 1.2 (female)
• 13 to < 16 years; 1.5 (male) and 1.4 (female)
• >= 16 years; 1.7 (male) and 1.4 (female)
• Total bilirubin =< 1.5 x upper limit of normal (ULN) for age within 7 days prior to enrollment (children with a diagnosis of Gilbert's syndrome will be allowed on study regardless of their total and indirect [unconjugated] bilirubin levels as long as their direct [conjugated] bilirubin is < 3.1 mg/dL)
• Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 3 x upper limit of normal (ULN) = 135 U/L within 7 days prior to enrollment. For the purpose of this study, the ULN for SGPT is 45 U/L
• Albumin >= 2 g/dL within 7 days prior to enrollment
• Left ventricular ejection fraction (LVEF) >= 53% (or institutional normal; if the LVEF result is given as a range of values, then the upper value of the range will be used) by echocardiogram within 7 days prior to enrollment
• Corrected QT (QTc) interval =< 450 msec by electrocardiography (EKG) within 7 days prior to enrollment
• Absolute neutrophil count >= 1,000/uL (unsupported) within 7 days prior to enrollment
• Platelets >= 100,000/uL (unsupported) within 7 days prior to enrollment
• Hemoglobin >= 8 g/dL (may be supported) within 7 days prior to enrollment
• Patients with a known seizure disorder should be stable and should have not experienced a significant increase in seizure frequency within 2 weeks prior to enrollment
• Patients 2-17 years of age must have a blood pressure that is =< 95th percentile for age, height, and gender at the time of enrollment. Patients >= 18 years of age must have a blood pressure =< 130/80 mmHg at the time of enrollment (with or without the use of antihypertensive medications).
• Note: Adequate blood pressure can be achieved using medication for the treatment of hypertension
• All patients must have ophthalmology toxicity assessments performed within 4 weeks prior to enrollment
• For all patients, an MRI of the brain (with orbital cuts for optic pathway tumors) and/or spine (depending on the site(s) of primary disease) with and without contrast must be performed within 4 weeks prior to enrollment
• For patients who undergo a surgery on the target tumor (not required), a pre- and post-operative* MRI of the brain (with orbital cuts for optic pathway tumors) or spine (depending on the site(s) of primary disease) with and without contrast must also be performed within 4 weeks prior to enrollment
• The post-operative MRIs should be performed ideally within 48 hours after surgery if possible
• Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1, or 2. Use Karnofsky for patients > 16 years of age and Lansky for patients =< 16 years of age
• Patients must have the ability to swallow whole capsules
• Patients must have receptive and expressive language skills in English or Spanish to complete the quality of life (QOL) and neurocognitive assessments
• 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.
• Patients must not have received any prior tumor-directed therapy including chemotherapy, radiation therapy, immunotherapy, or bone marrow transplant. Prior surgical intervention is permitted
• Patients with a concurrent malignancy or history of treatment (other than surgery) for another tumor within the last year are ineligible
• Patients may not be receiving any other investigational agents
• Patients with any serious medical or psychiatric illness/ condition, including substance use disorders likely in the judgement of the investigator to interfere or limit compliance with study requirements/treatment are not eligible
• Patients who, in the opinion of the investigator, are not able to comply with the study procedures are not eligible
• Female patients who are pregnant are not eligible 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 are not eligible
• Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation and for 12 weeks after stopping study therapy are not eligible
• Note: Women of child-bearing potential and males with sexual partners who are pregnant or who could become pregnant (i.e., women of child-bearing potential) should use effective methods of contraception for the duration of the study and for 12 weeks after stopping study therapy to avoid pregnancy and/or potential adverse effects on the developing embryo
• Cardiac conditions:
• Known genetic disorder that increases risk for coronary artery disease. Note: The presence of dyslipidemia in a family with a history of myocardial infarction is not in itself an exclusion unless there is a known genetic disorder documented
• Symptomatic heart failure
• New York Heart Association (NYHA) class II-IV prior or current cardiomyopathy
• Severe valvular heart disease
• History of atrial fibrillation
• Ophthalmologic conditions:
• Current or past history of central serous retinopathy
• Current or past history of retinal vein occlusion or retinal detachment
• Patients with uncontrolled glaucoma
• If checking pressure is clinically indicated, patients with intraocular pressure (IOP) > 22 mmHg or ULN adjusted by age are not eligible
• Ophthalmological findings secondary to long-standing optic pathway glioma (such as visual loss, optic nerve pallor, or strabismus) or longstanding orbito-temporal plexiform neurofibroma (PN, such as visual loss, strabismus) will NOT be considered a significant abnormality for the purposes of the study
• Treatments and/or medications patient is receiving that would make her/him ineligible, such as:
• Supplementation with vitamin E greater than 100% of the daily recommended dose. Any multivitamin containing vitamin E must be stopped prior to study enrollment even if less than 100% of the daily recommended dosing for vitamin E
• Surgery within 2 weeks prior to enrollment, with the exception of surgical placement for vascular access or cerebrospinal fluid (CSF) diverting procedures such as endoscopic third ventriculostomy (ETV) and ventriculo-peritoneal (VP) shunt.
• Note: Patients must have healed from any prior surgery prior to enrollment
• Patients who have an uncontrolled infection are not eligible

Inclusion Criteria
• ≥2 years and <18 years of age for enrolment in Phase 1 or ≥2 years and ≤21 years of age for enrolment in Phase 2.
• Recurrent or refractory solid tumors
• Phase 1: All solid tumors (measurable or evaluable disease), including primary central nervous system (CNS) tumors; exclusion of hepatoblastoma and lymphomas. Participants with diffuse intrinsic pontine glioma, optic pathway glioma, or pineal tumors with elevated tumor markers (alpha-fetoprotein [AFP] and beta-human chorionic gonadotropin [ß-hCG][or human chorionic gonadotropin [hCG])do not require histological or cytological confirmation of diagnosis
• Phase 2: Ewing sarcoma/peripheral primitive neuroectodermal tumor (pPNET), Rhabdomyosarcoma, High Grade Glioma (HGG) (all must have measurable disease); exclusion of Diffuse Intrinsic Pontine Glioma
• Histologically or cytologically confirmed diagnosis
• Measurable disease that meets the following criteria (Phase 2): 1. RECIST 1.1 (for all tumor types except HGG): At least 1 lesion of ≥1.0 cm in the longest diameter for a non lymph node or ≥1.5 cm in the short-axis diameter for a lymph node which is serially measurable according to RECIST 1.1 using computed tomography /magnetic resonance imaging (CT/MRI) 2. Response Assessment in Neuro-Oncology (RANO) for high grade glioma (HGG): At least one lesion must be measurable as defined as a bi dimensionally contrast enhancing lesion with clearly defined margins by CT or MRI scan, with a minimal diameter of 1 cm, and visible on 2 axial slices which are preferably at most 5 mm apart with 0 mm skip Lesions that have had external beam radiotherapy (EBRT) or locoregional therapies such as radiofrequency (RF) ablation must show evidence of progressive disease based on RECIST 1.1 to be deemed a target lesion
• Karnofsky performance score ≥50 for participants>16 year of age and Lansky play score ≥50 for participants ≤16 years of age. Neurologic deficits in participants with CNS tumors must have been relatively stable for at least 7 days prior to study enrollment. Participants 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
• Prior Therapy
• Participants must have fully recovered from the acute toxic effects of all prior anti-cancer therapy
• Cytotoxic chemotherapy or other chemotherapy 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 (eg, not associated with reduced platelet or absolute neutrophil counts): ≥7 days after the last dose of agent
• Monoclonal antibodies: ≥21 days or 3 half-lives (whichever is shorter) of the antibody must have elapsed after the last dose of a monoclonal antibody (including checkpoint inhibitors). 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. Participants 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
• Hematopoietic growth factors: ≥14 days after the last dose of a long-acting growth factor 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
• Interleukins, interferons, and cytokines (other than hematopoietic growth factors): ≥21 days after the completion of interleukins, interferons or cytokines (other than hematopoietic growth factors)
• Stem cell infusions (with or without total body irradiation): Allogeneic (non-autologous) bone marrow or stem cell transplant, or any stem cell infusion including donor leukocytes infusion or boost infusion: ≥84 days after infusion and no evidence of graft versus host disease; Autologous stem cell infusion including boost infusion: ≥42 days
• Cellular Therapy: ≥42 days after the completion of any type of cellular therapy (eg, modified T cells, natural killer cells, dendritic cells, etc)
• Radiotherapy (XRT)/External Beam Irradiation including Protons: ≥14 days after local XRT; ≥150 days after total body irradiation, craniospinal XRT or if radiation to ≥50% of the pelvis; ≥42 days if other substantial bone marrow radiation.
• Radiopharmaceutical therapy: ≥42 days after systemically administered therapy.
• Vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR)-targeted or mammalian target of rapamycin (mTOR)-targeted therapies: Must not have received prior exposure to lenvatinib; May have previously progressed on an mTOR inhibitor; No more than 2 prior VEGF/VEGFR-targeted therapies (For Phase 2 only); Must not have received prior VEGF/VEGFR-targeted therapy in combination with an mTOR inhibitor (For Phase 2 only)
• Adequate bone marrow function for participants with solid tumors without known bone marrow involvement
• Adequate bone marrow function for participants with known bone marrow metastatic disease
• Adequate renal function
• Adequate liver function
• Adequate cardiac function
• Adequate neurologic function
• Adequate blood pressure (BP) control with or without antihypertensive medications
• Adequate coagulation
• Adequate pancreatic function
• Adequate metabolic function
• Adequate glycemic control
• Participants must have a minimum body surface area (BSA) of 0.6 m^2 at study entry. Exclusion Criteria
• Participants who have had or are planning to have the following invasive procedures
• Major surgical procedure, laparoscopic procedure, open biopsy or significant traumatic injury within 28 days prior to enrolment
• Central line placement or subcutaneous port placement is not considered major surgery. External central lines must be placed at least 3 days prior to enrollment and subcutaneous ports must be placed at least 7 days prior to enrollment
• Fine needle aspirate within 7 days prior to enrolment
• Surgical or other wounds must be adequately healed prior to enrolment
• For purposes of this study, bone marrow aspirate and biopsy are not considered surgical procedures and therefore are permitted within 14 days prior to start of protocol therapy
• Participants who have non-healing wound, unhealed or incompletely healed fracture, or a compound (open) bone fracture at the time of enrolment
• Participants having an active infection requiring systemic therapy.
• Participants with a known history of active hepatitis B (defined as hepatitis B surface antigen reactive or hepatitis B virus- deoxyribonucleic [DNA] detected) or known active hepatitis C virus (HCV, defined as HCV- Ribonucleic acid [RNA] detected). Note: No testing for hepatitis B and hepatitis C is required unless mandated by the local health authority.
• Known to be human immunodeficiency virus (HIV) positive. Note: HIV testing is required at screening only when mandated by the local health authority
• Clinical evidence of nephrotic syndrome prior to enrolment
• Gastrointestinal bleeding or active hemoptysis (bright red blood of at least half teaspoon) within 21 days prior to enrolment
• Thrombotic/ thromboembolic event requiring systemic anticoagulation within 90 days prior to enrollment
• Evidence of new intracranial hemorrhage of more than punctate size on MRI assessment obtained within 28 days prior to study enrollment for Participants with HGG
• Diagnosis of lymphoma
• Radiographic evidence of major blood vessel invasion/infiltration.
• Evidence of untreated CNS metastases (exception: participants with primary CNS tumors and leptomeningeal disease)
• Participants who are currently receiving enzyme-inducing anticonvulsants
• Participants chronically receiving strong cytochrome P450 3A4 (CYP3A4)/P-glycoprotein (P-gp) inhibitors or inducers within 7 days prior to study enrollment
• Females who are breastfeeding or pregnant. For females of childbearing potential, a negative screening pregnancy test must be obtained within 72 hours before the first dose of study drug

1. Diagnosis of Multiple Sclerosis , ADEM, anti-MOG antibody associated CNS demyelination 2. Age 12 to 18 inclusive at time of enrollment 3. Ability of parent or legal guardian to provide informed consent if participant is under 18. 4. Ability of patients age 12 and older to give assent 5. Completion of the signed HIPPA authorization form by a parent or legal guardian or by participants (18 years of age). 1. Known history of traumatic brain injury that required medical care 2. Non-English speaking (based on standardized neuropsychological testing and questionnaires) 3. Claustrophobic, pregnant, the presence of metallic braces, implants or medical devices that are unsafe at 3T or 7T and/or interfere with the MRI/MRS signals

• Male or female:
• 2 years of age at 5 pediatric CMS study sites
• 10 years of age at other study sites.
• Confirmed physician diagnosis of LEMS, CMS or downbeat nystagmus.
• Completion of anti-cancer treatment at least 3 months (90 days) before treatment.
• Negative urine pregnancy test for females of childbearing potential at Screening.
• If sexually active and of childbearing potential, willing to use 2 acceptable methods of contraception from screening visit until 3 months after the last dose of investigational product. No adequate clinical data on exposed pregnancies are available for amifampridine. No nonclinical safety data are available regarding the effects of amifampridine on reproductive function. Amifampridine phosphate should not be used during pregnancy. It is unknown whether amifampridine is excreted in human breast milk. The excretion of amifampridine in milk has not been studied in animals. Amifampridine phosphate should not be used during breastfeeding.
• Any subject currently participating in studies LMS-002, LMS-002EXT, or CMS 001 is immediately eligible for enrollment into study EAP-001, as long as inclusion/exclusion criteria are still met.
• Willing and able to provide written informed consent after the nature of the study has been explained and before the start of any research-related procedures.
• History of epilepsy.
• CMS subtypes including slow-channel syndrome, LRP4 deficiency, and acetylcholinesterase deficiency.
• Known active brain metastasis. Patients with treated brain metastasis (radiotherapy and/or surgery) who have completed treatment for their brain metastasis >90 days before Screening, are neurologically stable (neurological symptoms grade <1), are on a stable dose of corticosteroids and have no evidence of new disease on magnetic resonance imaging (MRI) are eligible, provided they meet the other inclusion/exclusion criteria.
• Current use of dalfampridine (Ampyra®; 4-aminopyridine), and any form of 3,4 DAP other than the investigational product provided, such as amifampridine base and does not agree to discontinue use for the duration of the study.
• Use of guanidine hydrochloride within 7 days of starting amifampridine phosphate treatment.
• History of drug allergy to any pyridine-containing substances or any amifampridine phosphate excipients (i.e. microcrystalline cellulose, colloidal silicon dioxide or calcium stearate).
• Use of any other investigational product (other than 3,4 DAP or amifampridine phosphate) or investigational medical device within 30 days before starting treatment or requirement for any investigational agent before completion of all scheduled study assessments.
• An electrocardiogram (ECG) within 6 months before starting treatment that shows clinically significant abnormality(ies), in the opinion of the patient's personal physician.
• History of additional risk factors for torsade de pointes (e.g. history of surviving a near drowning due to loss of consciousness, family history of congenital QT syndrome, long QT syndrome, family history of unexplained early sudden death, or heart failure).
• Breastfeeding or pregnant or planning to become pregnant (self or partner). Male patients with breastfeeding partners are not excluded from the study.
• History of severe renal impairment or evidence of severe renal impairment at time of Screening on laboratory tests, specifically a creatinine clearance <30 mL/min (within 30 days) as calculated using the Cockcroft Gault formula.
• History at time of Screening of laboratory tests (within 30 days) indicating hepatic impairment: o In patients without liver metastases from cancer, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and/or total bilirubin >1.5 × upper limit of normal (ULN).
• Any condition that, in the view of the Principal Investigator, places the patient at high risk of poor treatment compliance or of not completing the study.