• English speaking
• Patient must have histologically or cytologically-proven advanced metastatic renal cell cancer (mRCC) or medullary thyroid cancer initially treated with anti-angiogenic tyrosine kinase inhibitors (AA-TKIs) including: sunitinib, sorafenib, pazopanib, cabozantinib, lenvatinib, vandetanib, or axitinib)
• NOTE: If patient has a severe sulfa allergy (e.g. Stevens Johnson reaction), then alternative non-sulfa medications can be considered in consultation with the C-BAC. Patient with a noted severe allergic reactions to medications listed in the algorithms is not necessarily excluded from this trial, as alternative medications could be considered in consultation with the C-BAC. Moreover, the patient treated with pre-existing medications that may interact with proposed BP medications is not necessarily excluded, as alternative medications exist. The clinical significance of any potential drug interactions can also be addressed with the C-BAC.
• Prior exposure to another AA-TKI is permissible. Concurrent or prior treatment with immunotherapy is also permissible
• Patient must have either clinical cardiovascular (CV) disease or evidence of increased CV risk as defined by one or more of the following:
• Clinical CV disease (history of myocardial infarction [MI] acute coronary syndrome, coronary revascularization, carotid endarterectomy or stenting greater than 3 months prior to registration, peripheral artery disease, cerebrovascular accident greater than 3 months prior to registration, abdominal aortic aneurysm or heart failure [HF])
• An American College of Cardiology/American Heart Association (ACC/AHA) CV risk score of at least 10%
• Chronic kidney disease (defined as an estimated glomerular filtration rate [eGFR] between 30 and 60 ml/min per 1.73 m^2). Dialysis patients and patients with an eGFR < 30 ml/min/1.73m^2 will be excluded. eGFR will be calculated according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-Epi) equation
• Patient must have systolic blood pressure (SBP) >= 130 mmHg on two or more occasions according to any in-clinic visit in the 12 weeks prior to or during their initial 4 weeks of treatment with an AA-TKI. Patient who have a prior diagnosis of hypertension or on pre-existing anti-hypertensive medications are eligible for enrollment. However, patient must not be on more than 3 baseline blood pressure medications at time of entry
• NOTE: If a patient has a single elevated SBP >= 130mmHg but not on repeat assessment, an additional SBP assessment should be performed to confirm ineligibility
• Patient must agree to comply with performing home blood pressure monitoring using an Omron7250 oscillometric monitor at home, or equivalent models
• Women of childbearing potential and sexually active males must be strongly advised to use accepted and effective methods of contraception or to abstain from sexual intercourse for the duration of their participation in the study
• Patient must have internet access through a computer, tablet, or smart phone to use EASEE-PRO and home BP monitoring. A valid phone number to receive text messages and email address are also necessary
• Leukocytes >= 3,000/mcL (obtained within 14 days prior to registration)
• Absolute neutrophil count >= 1,500/mcL (obtained within 14 days prior to registration)
• Platelets >= 100,000/mcL (obtained within 14 days prior to registration)
• Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) =< 2.5 x institutional upper limit of normal (ULN) (obtained within 14 days prior to registration)
• Patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated
• Patient 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
• Patient with treated brain metastases are eligible if follow-up brain imaging after central nervous system (CNS)-directed therapy shows no evidence of progression
• Patient with new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determines that immediate CNS specific treatment is not required and is unlikely to be required during the first cycle of therapy
• Patient with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial
• Patient must have an Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Patient must not have end-stage renal failure on dialysis, history of repeated hyperkalemia with a potassium > 5.5 mEq/l, or have a kidney transplant, or an eGFR < 30 ml/min/1.73 m^2
• Patient must not have coronary artery bypass grafting, MI acute coronary syndrome severe/unstable angina, stroke, transient ischemic attack, clinically significant bleeding requiring hospitalization or pulmonary embolism within 3 months prior to registration
• Patient must not have brain surgery or radiotherapy within 2 weeks prior to registration
• Patient must not have uncontrolled blood pressure defined by SBP > 160 mmHg on three or more antihypertensives prior to TKI initiation
• Patient with an arm circumference too large (> 50 cm) or small (< 17 cm) to allow accurate BP measurement with available devices will not be eligible
• Women must not be pregnant or breast-feeding due to the potential harm to an unborn fetus and possible risk for adverse events in nursing infants with some anti-hypertensives, including angiotensin receptor blockers. All females of childbearing potential must have a blood test or urine study within 14 days prior to registration to rule out pregnancy. A female of childbearing potential is defined as any woman, regardless of sexual orientation or whether they have undergone tubal ligation, who meets the following criteria: has achieved menarche at some point, has not undergone a hysterectomy or bilateral oophorectomy; or has not been naturally postmenopausal (amenorrhea following cancer therapy does not rule out childbearing potential) for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months)

Key For Phase 1:
• Participants with a locally advanced or metastatic solid tumor that:
• Has progressed on or is intolerant to standard therapy, or
• For which no standard therapy exists, or in the opinion of the Investigator, are not candidates for or would be unlikely to tolerate or derive significant clinical benefit from standard therapy, or
• Decline standard therapy
• Prior multikinase inhibitors (MKIs) with anti-RET activity are allowed
• A RET gene alteration is not required initially. Once adequate PK exposure is achieved, evidence of RET gene alteration in tumor and/or blood is required as identified through molecular assays, as performed for clinical evaluation
• Measurable or non-measurable disease as determined by RECIST 1.1 or RANO as appropriate to tumor type
• Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2 or Lansky Performance Score (LPS) greater than or equal to (≥) 40 percent (%) (age less than [<] 16 years) with no sudden deterioration 2 weeks prior to the first dose of study treatment
• Adequate hematologic, hepatic and renal function
• Life expectancy of at least 3 months For Phase 2: As for phase 1 with the following modifications:
• For Cohort 1: Participants must have received prior standard therapy appropriate for their tumor type and stage of disease, or in the opinion of the Investigator, would be unlikely to tolerate or derive clinical benefit from appropriate standard of care therapy
• Cohorts 1 and 2:
• Enrollment will be restricted to participants with evidence of a RET gene alteration in tumor
• At least one measurable lesion as defined by RECIST 1.1 or RANO, as appropriate to tumor type and not previously irradiated
• Cohorts 3 and 4: Enrollment closed
• Cohort 5:
• Cohorts 1-4 without measurable disease
• MCT not meeting the requirements for Cohorts 3 or 4
• MTC syndrome spectrum cancers (e.g., MTC, pheochromocytoma), cancers with neuroendocrine features/differentiation, or poorly differentiated thyroid cancers with other RET alteration/activation may be allowed with prior Sponsor approval
• cfDNA positive for a RET gene alteration not known to be present in a tumor sample
• Cohort 6: Participants who otherwise are eligible for Cohorts 1, 2 or 5 who discontinued another RET inhibitor may be eligible with prior Sponsor approval
• Cohort 7: Participants with a histologically confirmed stage IB-IIIA NSCLC and a RET fusion; determined to be medically operable and tumor deemed resectable by a thoracic surgical oncologist, without prior systemic treatment for NSCLC Key Exclusion Criteria (Phase 1 and Phase 2):
• Phase 2 Cohorts 1 and 2: an additional known oncogenic driver
• Cohorts 3 and 4: Enrollment closed
• Cohorts 1, 2 and 5: prior treatment with a selective RET inhibitor Notes: Participants otherwise eligible for Cohorts 1, 2, and 5 who discontinued another selective RET inhibitor may be eligible for Phase 2 Cohort 6 with prior Sponsor approval
• Investigational agent or anticancer therapy (including chemotherapy, biologic therapy, immunotherapy, anticancer Chinese medicine or other anticancer herbal remedy) within 5 half-lives or 2 weeks (whichever is shorter) prior to planned start of LOXO-292 (selpercatinib). In addition, no concurrent investigational anti-cancer therapy is permitted Note: Potential exception for this exclusion criterion will require a valid scientific justification and approval from the Sponsor
• Major surgery (excluding placement of vascular access) within 2 weeks prior to planned start of LOXO-292 (selpercatinib)
• Radiotherapy with a limited field of radiation for palliation within 1 week of planned start of LOXO-292 (selpercatinib), with the exception of participants receiving radiation to more than 30% of the bone marrow or with a wide field of radiation, which must be completed at least 4 weeks prior to the first dose of study treatment
• Any unresolved toxicities from prior therapy greater than Common Terminology Criteria for Adverse Events (CTCAE) Grade 1 at the time of starting study treatment with the exception of alopecia and Grade 2, prior platinum-therapy related neuropathy
• Symptomatic primary CNS tumor, metastases, leptomeningeal carcinomatosis, or untreated spinal cord compression. Participants are eligible if neurological symptoms and CNS imaging are stable and steroid dose is stable for 14 days prior to the first dose of LOXO-292 (selpercatinib) and no CNS surgery or radiation has been performed for 28 days, 14 days if stereotactic radiosurgery (SRS)
• Clinically significant active cardiovascular disease or history of myocardial infarction within 6 months prior to planned start of LOXO-292 (selpercatinib) or prolongation of the QT interval corrected (QTcF) greater than (>) 470 milliseconds (msec)
• Participants with implanted pacemakers may enter the study without meeting QTc criteria due to nonevaluable measurement if it is possible to monitor for QT changes.
• Participants with bundle branch block may be considered for study entry if QTc is appropriate by a formula other than Fridericia's and if it is possible to monitor for QT changes.
• Required treatment with certain strong cytochrome P450 3A4 (CYP3A4) inhibitors or inducers and certain prohibited concomitant medications
• Phase 2 Cohort 7 (neoadjuvant treatment): Participant must not have received prior systemic therapy for NSCLC.

• Advanced or metastatic solid or primary CNS tumor which has failed standard of care therapies
• Evidence of an activating RET gene alteration in the tumor and/or blood
• Measurable or non-measurable disease
• Karnofsky (participants 16 years and older) or Lansky (participants younger than 16) performance score of at least 50
• Participant with primary CNS tumors or cerebral metastases must be neurologically stable for 7 days prior and must not have required increasing doses of steroids within the last 7 days
• Adequate hematologic, hepatic and renal function.
• Ability to receive study drug therapy orally or via gastric access
• Willingness of men and women of reproductive potential to observe conventional and effective birth control
• Major surgery within two weeks prior to planned start of LOXO-292
• Clinically significant, uncontrolled cardiac, cardiovascular disease or history of myocardial infarction within 6 months prior to planned start of LOXO-292
• Active uncontrolled systemic bacterial, viral, fungal or parasitic infection
• Clinically significant active malabsorption syndrome
• Pregnancy or lactation
• Uncontrolled symptomatic hyperthyroidism or hypothyroidism (i.e. the participant required a modification to current thyroid medication in the 7 days before start of LOXO-292)
• Uncontrolled symptomatic hypercalcemia or hypocalcemia
• Known hypersensitivity to any of the components of the investigational agent, LOXO-292 or Ora-Sweet® SF and OraPlus®, for participants who will receive LOXO-292 suspension
• Prior treatment with a selective RET inhibitor(s) (including investigational selective RET inhibitor[s])

PHASE 1 Key 1. Histologically or cytologically confirmed diagnosis of locally advanced, or metastatic solid tumor (including primary CNS tumors) (Stage IV, American Joint Committee on Cancer v.7) that harbors an ALK, ROS1, NTRK1, NTRK2, or NTRK3 gene rearrangement by protocol specified tests. 2. ECOG PS 0-1. 3. Age ≥18 (or age ≥ 20 of age as required by local regulation). 4. Capability to swallow capsules intact (without chewing, crushing, or opening). 5. At least 1 measurable target lesion according to RECIST version 1.1. CNS-only measurable disease as defined by RECIST version 1.1 is allowed. 6. Prior cytotoxic chemotherapy is allowed. 7. Prior immunotherapy is allowed. 8. Resolution of all acute toxic effects (excluding alopecia) of any prior anti-cancer therapy to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Version 4.03 Grade less than or equal to 1. 9. Patients with asymptomatic CNS metastases (treated or untreated) and/or asymptomatic leptomeningeal carcinomatosis are eligible to enroll if they satisfy the protocol specified criteria. 10. Baseline laboratory values fulfilling the following requirements:Absolute neutrophils count (ANC) ≥1500/mm3 (1.5 × 109/L); Platelets (PLTs) ≥100,000/mm3 (100 × 109/L); Hemoglobin ≥ 9.0 g/dL transfusions are allowed; Serum creatinine or creatinine clearance Within normal limits or > 40 mL/min; Total serum bilirubin < 1.5 × ULN; Liver transaminases (ASTs/ALTs) < 2.5 × ULN; < 5 × ULN if liver metastases are present Alkaline phosphatase (ALP); < 2.5 × ULN; < 5 × ULN if liver and/or bone metastasis are present; Serum calcium, magnesium, and potassium Normal or CTCAE grade ≤ 1 with or without supplementation 11. Life expectancy ≥ 3 months. PHASE 2 Key Inclusion Criteria 1. Histologically or cytologically confirmed diagnosis of locally advanced, or metastatic solid tumor (including primary CNS tumors) that harbors a ROS1, or NTRK1-3 gene fusion. 2. Subject must have a documented ROS1 or NTRK1-3 gene fusion determined by tissue-based local testing using either: 1. a next-generation sequencing (NGS) or quantitative polymerase chain reaction (qPCR) test will be accepted to determine molecular eligibility. • Adequate tumor tissue needs to be sent to the Sponsor designated central diagnostic laboratory for retrospective confirmation by a central diagnostic laboratory test selected by the Sponsor. OR 2. a fluorescence in situ hybridization (FISH) test AND prospective confirmation of fusion status by a central diagnostic laboratory test selected by the Sponsor PRIOR to enrollment will be accepted to determine molecular eligibility.
• Adequate tumor tissue must be sent to the Sponsor designated central diagnostic laboratory for prospective confirmation by a central diagnostic laboratory test selected by the Sponsor PRIOR to enrollment. 3. Eastern Cooperative Oncology Group (ECOG) Performance Status 0-1. 4. Age ≥12 (or age ≥ 20 as required by local regulation). 5. Willing and able to provide written institutional review board (IRB)/institutional ethics committee-approved Informed Consent or an Assent signed by a parent or legal guardian for subjects age 12 to 17. 6. At least 1 measurable target lesion according to RECIST (v1.1) prospectively confirmed by Blinded Independent Central Radiology Review (BICR), selected by Sponsor, PRIOR to enrollment. Subjects with CNS-only measurable disease ≥10 mm as defined by RECIST (v1.1) are eligible. 7. Subjects with advanced solid tumors harboring ROS1, NTRK1, NTRK2, or NTRK3 rearrangement will be assigned into 6 distinct expansion (EXP) cohorts provided all inclusion and exclusion criteria are met. i. EXP-1: ROS1 TKI-naïve ROS1+ NSCLC ii. EXP-2: 1 Prior ROS1 TKI and 1 Platinum based chemo ROS1+ NSCLC iii. EXP-3: 2 Prior ROS1 TKIs ROS1+ NSCLC (No Chemo or IO) iv. EXP-4: 1 Prior ROS1 TKI ROS1+ NSCLC (No Chemo or IO) v. EXP-5: TRK TKI-naïve NTRK+ solid tumors vi. EXP-6: TRK TKI-pretreated NTRK+ solid tumors 8. Subjects with asymptomatic CNS metastases (treated or untreated) and/or asymptomatic leptomeningeal carcinomatosis are eligible to enroll if they satisfy the protocol specified criteria. 9. Baseline laboratory values fulfilling the following requirements:Absolute neutrophils count (ANC) ≥1500/mm3 (1.5 × 109/L); Platelets (PLTs) ≥100,000/mm3 (100 × 109/L); Hemoglobin ≥ 9.0 g/dL transfusions are allowed; Serum creatinine or creatinine clearance > 40 mL/min; Total serum bilirubin < 1.5 × ULN; Liver transaminases (ASTs/ALTs) < 2.5 × ULN; < 5 × ULN if liver metastases are present Alkaline phosphatase (ALP); < 2.5 × ULN; < 5 × ULN if liver and/or bone metastasis are present; Serum calcium, magnesium, and potassium Normal or CTCAE grade ≤ 1 with or without supplementation 10. Life expectancy ≥ 3 months. Key Exclusion Criteria PHASE 1 and PHASE 2 1. Concurrent participation in another therapeutic clinical trial. 2. Symptomatic brain metastases or leptomeningeal involvement. 3. History of previous cancer, except for squamous cell or basal-cell carcinoma of the skin, or any in situ carcinoma that has been completely resected, requiring therapy within the previous 2 years. 4. Major surgery within 4 weeks of start of repotrectinib treatment. Radiation therapy (except palliative to relieve bone pain) within 2 weeks of study entry. Palliative radiation (≤10 fractions) must have been completed at least 48 hours prior to study entry 5. Clinically significant cardiovascular disease (either active or within 6 months prior to enrollment): myocardial infarction, unstable angina, coronary/peripheral artery bypass graft, symptomatic congestive heart failure (New York Heart Association Classification Class ≥ II), cerebrovascular accident or transient ischemic attack, symptomatic bradycardia, requirement for anti-arrhythmic medication. Ongoing cardiac dysrhythmias of NCI CTCAE grade ≥2 6. Any of the following cardiac criteria: Mean resting corrected QT interval (ECG interval measured from the onset of the QRS complex to the end of the T wave) for heart rate (QTcF) > 470 msec obtained from 3 ECGs, using the screening clinic ECG machine-derived QTc value Any clinically important abnormalities in rhythm, conduction or morphology of resting ECG (e.g., complete left bundle branch block, third degree heart block, second degree heart block, PR interval > 250 msec) Any factors that increase the risk of QTc prolongation or risk of arrhythmic events such as heart failure, hypokalemia, congenital long QT syndrome, family history of long QT syndrome, or any concomitant medication known to prolong the QT interval. 7. Known active infections (bacterial, fungal, viral including HIV positivity). 8. Gastrointestinal disease (e.g., Crohn's disease, ulcerative colitis, or short gut syndrome) or other malabsorption syndromes that would impact drug absorption. 9. Peripheral neuropathy of CTCAE ≥grade 2. 10. History of extensive, disseminated, bilateral, or presence of CTCAE grade 3 or 4 interstitial fibrosis or interstitial lung disease including a history of pneumonitis, hypersensitivity pneumonitis, interstitial pneumonia, interstitial lung disease, obliterative bronchiolitis, and pulmonary fibrosis. Subjects with history of prior radiation pneumonitis are not excluded.

1. ≥ 18 years of age 2. Histopathological or cytologically documented locally advanced or metastatic solid tumors who have no available standard therapeutic treatment options 3. At least one measurable lesion as defined by RECIST V1.1 criteria for solid tumors 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 5. Adequate organ function confirmed at screening and within 10 days of initiating treatment, as evidenced by:
• Absolute neutrophil count (ANC) ≥ 1.5 x 10^9/L
• Hemoglobin (Hgb) ≥ 8 g/dl
• Platelets (plt) ≥ 75 x 10^9/L
• AST/SGOT and ALT/SGPT ≤ 2.5 x Upper Limit of Normal (ULN) or ≤ 5.0 x ULN if liver metastases are present
• Total bilirubin ≤ 1.5 x ULN
• Calculated creatinine clearance ≥ 50 mL/min (Cockcroft Gault formula) 6. Negative pregnancy test within 72 hours before starting study treatment in all premenopausal women and women < 12 months after the onset of menopause 7. Must agree to take sufficient contraceptive methods to avoid pregnancy during the study and until at least 6 months after ceasing study treatment 8. Able to sign informed consent and comply with the protocol 1. Women who are pregnant or lactating 2. Women of child-bearing potential (WOCBP) who do not use adequate birth control 3. Patients with any hematologic malignancy, including leukemia (any form), lymphoma, and multiple myeloma 4. Patients with a history of primary central nervous system tumors or carcinomatous meningitis. 5. Patients with the following mood disorders as judged by the Investigator or a psychiatrist:
• Medically documented history of or active major depressive episode, bipolar disorder (I or II), obsessive-compulsive disorder, schizophrenia; a history of suicidal attempt or ideation, or homicidal ideation (immediate risk of doing harm to others)
• ≥ CTCAE grade 3 anxiety 6. Impaired cardiac function or significant diseases, including but not limited to any of the following:
• left ventricular ejection fraction (LVEF) < 45% as determined by multigated acquisition (MUGA) scan or echocardiogram (ECHO)
• Congenital long QT syndrome
• QTcF ≥ 480 msec on screening ECG
• Unstable angina pectoris ≤ 3 months prior to starting study drug
• Acute myocardial infarction ≤ 3 months prior to starting study drug 7. Patients with:
• unresolved diarrhea ≥ CTCAE grade 2, or
• impairment of gastrointestinal (GI) function, or
• GI disease that may significantly alter the absorption of TT-00420 8. Other concurrent severe and/or uncontrolled concomitant medical conditions (e.g., uncontrolled hypertension, uncontrolled hypertriglyceridemia, or active or uncontrolled infection) that could cause unacceptable safety risks or compromise compliance with the protocol 9. Patients who have received chemotherapy, targeted therapy, or immunotherapy ≤ 4 weeks (6 weeks for nitrosourea or mitomycin-C) prior to starting study drug or who have not recovered from side effects of such therapy 10. Patients who have received wide field radiotherapy ≤ 4 weeks or limited field radiation for palliation ≤ 2 weeks prior to starting study drug or who have not recovered from side effects of such therapy 11. Patients who have undergone major surgery ≤ 4 weeks prior to starting study drug or who have not recovered from side effects of such therapy 12. Patients who have been treated with any hematopoietic colony-stimulating growth factors (e.g., G-CSF, GM-CSF) ≤ 4 weeks prior to starting study drug. 13. Patients who are currently receiving treatment with therapeutic doses of warfarin sodium or any other coumarin-derivative anticoagulants 14. Patients who have received systemic corticosteroids ≤ 2 weeks prior to starting study drug or who have not recovered from the side effects of such treatment. 15. Patients who are currently receiving treatment with strong CYP3A inhibitors or inducers ≤ 2 weeks prior to starting study drug. 16. Known diagnosis of human immunodeficiency virus (HIV) infection (HIV testing is not mandatory; patients with well controlled HIV might be enrolled) 17. Known history of active infection with Hepatitis B or Hepatitis C 18. Has received a live-virus vaccination within 30 days of planned first dose 19. Inability to swallow or tolerate oral medication 20. Has a history or current evidence of any condition, therapy, or laboratory abnormality that, in the opinion of the investigator, might confound the results of the trial, interfere with the patient's safe participation and compliance in the trial.

1. Must have provided informed consent in a manner approved by the Investigator's Institutional Review Board (IRB) prior to any study-related procedure being performed. If a participant is unable to provide informed consent due to his/her medical condition, the participant's legally authorized representative may consent on behalf of the study participant, as permitted by local law and institutional Standard Operating Procedures; 2. Aged greater than or equal to 18 years at the time of informed consent; 3. Recent use of an FDA-approved immune checkpoint inhibitor (ICI, defined as administered an immune checkpoint inhibitor ≤ 6 months of myocarditis diagnosis), alone or in combination with other cancer therapies (i.e. chemotherapy, radiation therapy or targeted therapy). The FDA-approved ICI could be given as part of a clinical trial but not in combination with a new investigational agent which may cause myocarditis; 4. A diagnosis of myocarditis. 5. Hospitalized at the time of randomization; 6. On 1000 mg of solumedrol per day for myocarditis or with an intent to initiate 1000 mg of solumedrol per day for myocarditis within 24 hours of first administration of study drug; 7. Serum evidence of ongoing myocardial injury: Serum evidence of ongoing myocardial injury will be defined as an institutional troponin (either conventional or high-sensitivity troponin I or T, using the standard institutional assay) with a value that is ≥5 times the upper limit of the reference standard normal for that institution. The troponin assay may be adjusted based on sex depending on institutional standards. This value of troponin of ≥5 times above the institutional upper limits of normal value must be noted within 10 days prior to potential randomization. The 10-day period can be in the outpatient or inpatient setting. For example, a participant with a troponin value that on one occasion was ≥5 times the upper limits of institutional normal in the 10-day window prior to potential randomization (whether in the inpatient or outpatient setting), but later decreases below that threshold, typically due to starting corticosteroids, would still be considered eligible; 8. The following laboratory parameters, not older than 48 hours at the time of randomization, and measured as part of usual care:
• Total white blood cell (WBC) count >2,500/μl
• Absolute neutrophil count (ANC) >1,500/μL
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) <20 times the upper limit of the institutional normal ranges; 9. Women of childbearing potential (i.e., not postmenopausal, or surgically sterilized) must have a negative highly sensitive urine or serum pregnancy test prior to randomization. Participating women of childbearing potential must be willing to consistently use effective methods of contraception from screening until at least 90 days after administration of the last dose of study drug. Participating men must also be willing to consistently use effective methods of contraception from screening until at least 90 days after administration of the last dose of study drug; and 10. Must be willing and able to abide by all study requirements and restrictions. 1. Must not have experienced any of the following (as defined in the section on the primary endpoint) in the 30-day period prior to randomization:
• A sudden cardiac arrest
• Cardiogenic shock as defined. A significant bradyarrhythmia (Mobitz type II second degree atrioventricular block or third degree (complete) atrio-ventricular (AV) block, for which an intervention with a temporary or permanent pacemaker is completed or recommended).
• A significant tachyarrhythmia (ventricular fibrillation of any duration or sustained ventricular tachycardia (>30 seconds, >120 beats per minute); or a ventricular tachyarrhythmia requiring intervention. 2. Recent (≤2 month) exposure to abatacept or belatacept. 3. Concurrent or recent (≤2 month) use of the following non-corticosteroid immunosuppressive therapies prior to randomization: mycophenolate, JAK STAT inhibitors (including but not limited to upadacitinib, tofacitinib, baricitinib, and filgotinib), tacrolimus, anti-thymocyte globulin, alemtuzumab, infliximab, and plasma exchange. The use of intravenous immunoglobulin is permitted prior to randomization and during study treatment. 4. Currently enrolled in another interventional study utilizing systemic agents for the management of ICI-related toxicities. 5. Female who is pregnant, breastfeeding, or is considering becoming pregnant during the study or for approximately 90 days after the last dose of study drug. 6. Male who is considering fathering a child or donating sperm during the study or for approximately 30 days after the last dose of study drug. 7. Any active, chronic, or recurrent viral infection that, based on the investigator's clinical assessment, makes the participant an unsuitable candidate for the study. These may include hepatitis B virus (HBV) or hepatitis C virus (HCV), recurrent or disseminated (even a single episode) herpes zoster, and disseminated (even a single episode) herpes simplex. Active HBV and HCV are defined as: HBV: hepatitis B surface antigen (HBs Ag) positive (+) or detected sensitivity on the HBV deoxyribonucleic acid (DNA) polymerase chain reaction (PCR) qualitative test for Hepatitis B core antibody (HBc Ab) positive (+) participants; HCV: HCV ribonucleic acid (RNA) detectable in any participant with anti-HCV antibody (HCV Ab). Patients with active Covid-19 infection will be excluded. This is defined as the period of ongoing symptoms in the setting of a positive Covid-19 test, or until 10 days after symptom onset and after resolution of fever for at least 24 hours, without the use of fever-reducing medications. 8. Known active tuberculosis (TB), history of incompletely treated TB, suspected or known extrapulmonary TB, suspected or known systemic bacterial or fungal infections; 9. Receipt of any live vaccine within four weeks prior to the first dose of study drug, or expected need of live vaccination during study participation including at least 90 days after the last dose of IV study drug. 10. Any medical condition that could interfere with, or for which the treatment might interfere with, the conduct of the study or interpretation of the study results, or that would, in the opinion of the Investigator, increase the risk of the participant by participating in the study. 11. Any factors that, in the Investigator's opinion, are likely to interfere with study procedures, such as history of noncompliance with scheduled appointments.

• Patients with histologically confirmed solid tumor malignancies with residual tumors present that require standard of care chemotherapy for a minimum number of cycles. All anatomical sites and all tumor histologies are eligible including central nervous system tumors. Both newly diagnosed and/or newly relapsed patients are eligible.
• Patients ages 8
•25 years
• In the opinion of the investigator, patients must be thought to be able to lie still for imaging without sedation for 20
•30 minutes.
• Patients must have a performance status of > 50% (Lansky or Karnofsky).
• Patients of childbearing potential must have a negative urine or serum pregnancy test as per institution's standard of care within 7 days prior to [18F]FLT PET/CT imaging.
• Ability to understand and the willingness to sign a written informed consent/assent.
• Patients with known allergic or hypersensitivity reactions to previously administered radiopharmaceuticals of similar chemical or biologic composition to [18F]FLT
• Newly diagnosed subjects who had prior chemotherapy or radiotherapy before enrollment in the study. Relapsed patients are eligible prior to starting their relapsed chemotherapy regimen if they meet the other eligibility criteria.
• Subjects for whom chemotherapy is not a standard of care primary therapy option.
• Patients who are pregnant or breast-feeding.
• Patients with no residual tumor (i.e. complete resection at diagnosis or relapse).

• Age -- Age ≤ 30 years at time of initial qualifying solid tumor diagnosis
• Diagnosis -- Histologic diagnosis of solid malignancy (excluding brain tumors and lymphoma) that meets at least one of the following criteria:
• Refractory, defined as tumor progression after initiation of standard first line therapy without having achieved a prior partial or complete remission OR Biopsy proven residual disease at the completion of planned standard initial front-line therapy.
• Recurrent, defined as tumor progression after achieving a prior partial or complete remission
• Newly diagnosed high risk disease, defined as having an expected event free survival of < 50% at 2 years.
• Lacks definitive diagnosis or classical genomic findings after histologic review and standard molecular testing (rare tumor group).
• Examples include (eligibility not limited to these examples):
• Histology typically associated with a fusion in which fusion is not detected.
• Ewing-like sarcoma
• Undifferentiated sarcoma
• Inflammatory myofibroblastic tumor without ALK fusion
• Infantile fibrosarcoma without NTRK fusion
• Specimen Samples
• Sufficient tumor specimen available to meet the minimum requirements for profiling from diagnosis or progression / recurrence --- OR
• Surgery / biopsy planned as part of clinical care that is anticipated to yield sufficient material to meet the minimum requirements for profiling; OR
• Patient has already had molecular profiling and patient has not yet started matched targeted therapy based on the report .
• No Therapy Planned -- Patients who have declined further anticancer therapy will be excluded.
• Performance Status -- Patients with Lansky (age < 16 years) or Karnofsky (age ≥16 years) score < 50 will be excluded.
• Life Expectancy -- Patients with anticipated life expectancy < 3 months will be excluded.

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. A female of child-bearing potential is any woman (regardless of sexual orientation, marital status, 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). Medically acceptable birth control (contraceptives) includes:
• Approved hormonal contraceptives (such as birth control pills, patch, or ring: Depo-Provera, Implanon), or
• Barrier methods (such as a condom or diaphragm) used with a spermicide (a substance that kills sperm) 10. 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.

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.
• For randomized Phase 2 part: Histologically confirmed Ewing sarcoma at diagnosis or at relapse, with presence of EWSR1-ETS or FUS-ETS rearrangement. Histopathology confirmation of both EWSR1-ETS or FUS-ETS rearrangement partners is required OR availability of formalin fixed paraffin embedded (FFPE) tumor tissue sample for central testing. Patient must have relapsed or have refractory disease and at least evaluable disease in at least one site other than bone marrow that can be followed by imaging. 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, no platelet transfusion in past 7 days prior study entry);
• 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, unless the patient has documented Gilbert's syndrome. 7. Patients enrolled to Phase 1 portion of the study and tumor specific cohorts must have measurable disease as defined by RECIST version 1.1 or modified RANO criteria for CNS disease or INRC for neuroblastoma. Patients with EWS enrolled to Phase 2 portion of the study are eligible with evaluable disease (eg, bone only disease with no soft tissue component). 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. Exclusion: 1. Phase 1 and tumor specific cohorts: 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. Phase 2 portion: prior treatment with a CDK4/6 inhibitor or progression while on treatment with an IRN-containing or TMZ-containing regimen. Patients who have received IRN and/or TMZ and did not progress while on these medications are eligible. 2. Prior intolerability to IRN and/or TMZ plus/minus palbociclib with IRN and TMZ combination and prior intolerability to TOPO and/or CTX for 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. Systemic anti cancer therapy within 2 weeks prior to study entry and 6 weeks for nitrosoureas. 5. Prior irradiation to >50% of the bone marrow (see Appendix 9). 6. Participation in other studies involving investigational drug(s) within 2 weeks or 5 half lives, whichever is longer, prior to study entry. 7. Major surgery within 4 weeks prior to study entry. Surgical biopsies or central line placement are not considered major surgeries. 8. For IRN and TMZ with/without palbociclib combinations: known or suspected hypersensitivity to palbociclib, IRN and/or TMZ. For combination of palbociclib with TOPO and CTX: known or suspected hypersensitivity to palbociclib, TOPO and/or CTX. 9. 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. 10. 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. 11. Hereditary bone marrow failure disorder. 12. QTc >470 msec. 13. 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%. 14. Recent or ongoing clinically significant gastrointestinal disorder that may interfere with absorption of orally administered drugs (eg, gastrectomy). 15. 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. 16. 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.

• 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

• Be male at any age.
• Be scheduled to undergo surgery, chemotherapy, drug treatment and/or radiation for the treatment or prevention of a medical condition or malignancy with risk of causing permanent and complete loss of subsequent testicular function.
• Or, have a medical condition or malignancy that requires removal of all or part of one or both testicles.
• Have newly diagnosed or recurrent disease. Those who were not enrolled at the time of initial diagnosis (i.e., patients with recurrent disease) are eligible if they have not previously received therapy that is viewed as likely to result in complete and permanent loss of testicular function.
• Have two testicles if undergoing elective removal of all or part of a testicle for fertility preservation only. Note: removal of both testicles will limit fertility preservation options.
• Sign an approved informed consent and authorization permitting the release of personal health information. The patient and/or the patient's legally authorized guardian must acknowledge in writing that consent for specimen collection has been obtained, in accordance with institutional policies approved by the U.S. Department of Health and
• Consent for serum screening tests for infectious diseases [HIV-1, HIV-2, Hepatitis B, Hepatitis C], to be performed at the time of testicular tissue harvesting.
• Undergo a full history and physical examination and obtain standard pre-operative clearance (based on the most recent ACC/AHA Guideline for Perioperative Cardiovascular Evaluation for Noncardiac Surgery) as determined by their primary surgeon.
• Participating in long term follow-up is a requirement of the protocol.
• Diagnosed with psychological, psychiatric, or other conditions which prevent giving fully informed consent.
• Diagnosed with an underlying medical condition that significantly increases their risk of complications from anesthesia and surgery.

• Have advanced breast cancer or another solid tumor with the presence of a PIK3CA H1047R mutation (or other Sponsor and SRC-approved, activating PIK3CA mutations other than H1047R mutation)
• Have adequate archival tumor tissue sample available or be approved by the Sponsor for enrollment if no tumor sample is available.
• Have stopped all cancer treatment and have recovered from the major side effects
• Have adequate organ function, as measured by blood tests
• Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) scale
• Patients must have
• Measurable disease --- Patients with non-breast tumor types must have at least 1 measurable lesion
• Non-measurable bone disease (at least one bone lesion in breast cancer patients only)
• For patients with an ER+ breast cancer diagnosis:
• If female, must be postmenopausal
• If male, must agree to use hormone suppression
• Phase 1a: -- Dose escalation and backfill patients:
• Advanced solid tumor
• Patients may have had up to 5 prior regimens for advanced disease
• Phase 1b:
• Part A:
• ER+/HER2- advanced breast cancer
• Patients may have had up to 2 prior regimens for advanced disease
• Prior cyclin dependent kinase (CDK)4/6 inhibitor therapy required
• Part B:
• ER+/HER2- advanced breast cancer
• Patients may have had up to 2 prior regimens for advanced disease.
• Part C:
• ER+/HER2- advanced breast cancer
• Patients may have had up to 5 prior regimens for advanced disease. ---- Prior CDK4/6 inhibitor therapy required.
• Have a diagnosis of diabetes mellitus Type 2
• Part D:
• Advanced breast cancer
• Patients may have had up to 5 prior regimens for advanced disease.
• Part E:
• Advanced solid tumor
• Patients may have had up to 3 prior regimens for advanced disease
• Medical Conditions
• Colorectal cancer
• Endometrial cancers with specific concurrent oncogenic alterations
• A history of known active or suspected
• Diabetes mellitus Type 1 or
• Diabetes mellitus Type 2 requiring antidiabetic medication (Phase 1a and all parts of Phase 1b except Part C).
• Serious concomitant systemic disorder
• Known or suspected history of untreated or uncontrolled central nervous system (CNS) involvement.
• Active uncontrolled systemic bacterial, viral, fungal, or parasitic infection, or other clinically significant active disease process
• Prior exposure to PI3K/AKT/mTOR inhibitor(s), except in certain circumstances

• Patients can have either histologically confirmed malignancy that is radiologically evaluable and metastatic or unresectable, or have a malignancy for which a PD-1/PD-L1 inhibitor has been approved in the adjuvant setting. Eligible tumor types include solid tumors and malignancies in which there is known evidence of clinical activity for single agent PD-1 or PD-L1 antibodies. Nivolumab is Food and Drug Administration (FDA)-approved for the treatment of melanoma, non-small cell lung cancer (NSCLC), Merkel cell cancer, bladder cancer, renal cell carcinoma (RCC), gastric cancer, hepatocellular carcinoma (HCC), cervical cancer, head and neck cancer, Hodgkin lymphoma (HL), metastatic small cell lung cancer (SCLC), and any solid tumor with microsatellite instability (MSI)-high status confirmed. Patients with HL are eligible but must follow standard response criteria. Additional tumor types may be eligible on a case by case basis upon discussion with principal investigator (PI). Patients enrolling on the trial for adjuvant use will be restricted to those with histology for which a PD-1/PD-L1 inhibitor has been approved in the adjuvant setting including but not limited to NSCLC, melanoma, RCC, cervical cancer, and bladder cancer
• Patients who have previously received other forms of immunotherapy (high-dose [HD] IL-2, IFN, CTLA-4) are allowed. Patients must not have received cytokine immunotherapy for at least 4 weeks before nivolumab administration. Patients who have received prior anti-CTLA4 will be allowed and the washout period is 6 weeks
• Age >= 18 years; children are excluded from this study but may be eligible for future pediatric phase 1 combination trials
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 (Karnofsky >= 60)
• Life expectancy of greater than 12 weeks
• Leukocytes >= 1,000/mcL
• Absolute neutrophil count >= 500/mcL
• Platelets >= 50,000/mcL
• Total bilirubin =< 2 x institutional upper limit of normal (ULN)
• Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) =< 5 x institutional ULN or < 8 x institutional ULN for patients with liver metastases or an autoimmune disease that is contributing to the elevation of these values
• Creatinine ULN OR glomerular filtration rate (GFR) >= 30 mL/min (if using the Cockcroft-Gault formula)
• Human immunodeficiency virus (HIV)-infected patients on effective antiretroviral therapy with undetectable viral load within 6 months are eligible for this trial
• If evidence of chronic hepatitis B virus (HBV) infection, HBV viral load must be undetectable on suppressive therapy if indicated
• If history of hepatitis C virus (HCV) infection, must be treated with undetectable HCV viral load
• Patients with new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determines that immediate central nervous system (CNS) specific treatment is not required and is unlikely to be required for at least 4 weeks (or scheduled assessment after the first cycle of treatment), and a risk-benefit analysis (discussion) by the patient and the investigator favors participation in the clinical trial
• The effects of nivolumab on the developing human fetus are unknown. For this reason, women of child-bearing potential (WOCBP) and men 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. WOCBP receiving nivolumab will be instructed to adhere to contraception for a period of 5 months after the last dose of investigational product. Men receiving nivolumab and who are sexually active with WOCBP will be instructed to adhere to contraception for a period of 7 months after the last dose of investigational product. Women of childbearing potential must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of human chorionic gonadotropin [HCG]) within 24 hours prior to the start of nivolumab. Women must not be breastfeeding. Women who are not of childbearing potential (i.e., who are postmenopausal or surgically sterile as well as azoospermic men) do not require contraception. WOCBP is defined as any female who has experienced menarche and who has not undergone surgical sterilization (hysterectomy or bilateral oophorectomy) or who is not postmenopausal. Menopause is defined clinically as 12 months of amenorrhea in a woman over 45 in the absence of other biological or physiological causes. In addition, women under the age of 55 must have a documented serum follicle stimulating hormone (FSH) level less than 40 mIU/mL. These durations have been calculated using the upper limit of the half-life for nivolumab (25 days) and are based on the protocol requirement that WOCBP use contraception for 5 half-lives plus 30 days, and men who are sexually active with WOCBP use contraception for 5 half-lives plus 90 days. 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
• Ability to understand and the willingness to sign a written informed consent document
• Patients with more than one autoimmune disease are eligible. The treating physician would determine which autoimmune disease is dominant and the patient would be treated under that specific cohort
• Patients who have had chemotherapy or radiotherapy within 2 weeks (6 weeks for nitrosoureas or mitomycin C) prior to entering the study or those who have not recovered from adverse events (AEs) due to agents administered more than 4 weeks earlier have not resolved or stabilized. Palliative (limited-field) radiation therapy (RT) is permitted (2 week washout from start of treatment), if all of the following criteria are met:
• Repeat imaging demonstrates no new sites of bone metastases
• The lesion being considered for palliative radiation is not a target lesion
• Patients with prior therapy with an anti-PD-1 or anti-PD-L1
• Patients with prior allogeneic hematologic transplant
• Patients who are receiving any other anticancer investigational agents
• 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 would limit compliance with study requirements
• Patients who have had evidence of active or acute diverticulitis, intra-abdominal abscess, gastrointestinal (GI) bleeding, obstruction, and abdominal carcinomatosis which are known risk factors for bowel perforation should be evaluated for the potential need for additional treatment before coming on study. For the IBD (UC and CD) cohort, an endoscopic assessment, disease activity index, and disease specific inclusion/exclusion criteria will substitute for these factors in determining eligibility with the exception of abdominal carcinomatosis, which should prompt further evaluation

• Women and men of reproductive potential should agree to use an appropriate method of birth control throughout their participation in this study due to the teratogenic potential of the therapy utilized in this trial. Appropriate methods of birth control include abstinence, oral contraceptives, implantable hormonal contraceptives or double barrier method (diaphragm plus condom)
• Diagnosis of advanced cancer
• Patient-reported 2-month weight loss of at least 5 pounds (2.3 kilograms) and/or physician-estimated caloric intake of less than 20 calories/kilogram of body weight per day
• The patient must perceive loss of appetite and/or weight as a problem; and have an appetite score of 4 or worse on the "Please rate your appetite…." question that requires a patient response on a 0-10 numeric rating scale
• Not receiving ongoing tube feedings or parenteral nutrition at the time of registration
• Not currently using systemic adrenal steroids (with the exception of short-term dexamethasone within 3 days of chemotherapy for control of chemotherapy side effects)
• No use of androgens, progesterone analogs, or other appetite stimulants within the past month
• Patient should not have poorly controlled hypertension or congestive heart failure at registration
• Patient should not have an obstruction of the alimentary canal, malabsorption, or intractable vomiting (defined as vomiting more than 3 times per day over the preceding week)
• Not currently using olanzapine for another medical condition or had previously used olanzapine for chronic nausea or for any pre-existing psychotic disorder
• Patient should not have had a previous blood clot at any time in the past
• No history of poorly controlled diabetes
• No symptomatic leptomeningeal disease or known brain metastases as these patients may have difficulty taking oral medications
• No history of hypersensitivity to olanzapine or megestrol acetate
• No COVID-19 infection in the past that, in the opinion of the treating physician, had left patients with compromised taste, which has not resolved at the time of registration
• Not pregnant and not nursing, because this study involves an investigational agent whose genotoxic, mutagenic and teratogenic effects on the developing fetus and newborn are unknown. Therefore, for women of childbearing potential only, a negative urine or serum pregnancy test done =< 14 days prior to registration is required
• Age >= 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status 0, 1 or 2
• Estimated life expectancy of 3 months or longer
• Serum creatinine =< 2.0 mg/dL
• Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) =< 3 x upper limit of normal (ULN)
• Fasting glucose > 1410 mg/dl
• Granulocytes > 1000/hpf
• No treatment with another antipsychotic agent, such as risperidone, quetiapine, clozapine, butyrophenone within 30 days of enrollment
• In order to complete the mandatory patient-completed measures, participants must be able to speak and/or read English or Spanish. Sites seeking to enroll Spanish-speaking patients should have access to Spanish speaking staff on site or through the use of a translation service to be able to conduct the informed consent discussion in Spanish, and to conduct the weekly phone calls
• Psychiatric illness which would prevent the patient from giving informed consent
• Medical condition such as uncontrolled infection (including human immunodeficiency virus [HIV]), uncontrolled diabetes mellitus or cardiac disease which, in the opinion of the treating physician, would make this protocol unreasonably hazardous for the patient
• Patients who cannot swallow oral formulations of the agents
• Patients with impaired decision-making capacity (such as with a diagnosis of dementia or memory loss) are not eligible for this study
• No presence of a hormone-sensitive tumor, such as breast, endometrial, or prostate cancer (this exclusion criterion is intended to circumvent any confounding antineoplastic effects of megestrol acetate)