Optional tumor biopsies: Patients will be asked permission (consent) to provide tissue from a recent (within 6 weeks of study entry) archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion; in addition, for on-study biopsies (after one week and after 7 weeks of initiating study therapy) and for baseline tumor biopsy if an archival tissue sample is not available: willingness to undergo biopsies will be asked; patients who consent to provide tumor biopsies for research should have tumors deemed relatively safely accessible for biopsies with low likelihood of complication Must be able to provide tumor tissue obtained within 6 months of study enrollment. If such tissue is not available, a newly obtained core or excisional biopsy of a tumor lesion must be performed. RANDOMIZED PHASE II CLINICAL TRIAL: Have provided tissue from a newly obtained biopsy (an archival tissue sample may be substituted if new biopsy cannot be obtained and by discretion of principal investigator only) obtained from a focus of metastatic disease (a tumor lesion in newly diagnosed metastatic TNBC de novo is acceptable) and agreed to providing a second newly obtained biopsy after completion of 2 cycles of the study drugs Must agree to provide archival or newly obtained tumor tissue sample prior to the start of treatment in this study Has provided archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Previously obtained archival tumor tissue, or tissue obtained by endoscopically guided core biopsy at screening For participants entering Ph1b: have submitted, a sample from a newly obtained core or excisional biopsy of a tumor lesion or a recent biopsy defined by 6 months of study enrollment (Ph1b). Tissue (or lymph node biopsy for rrcHL participants) available from an archival tissue sample or, if appropriate, a newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Be willing to provide archived tumor tissue; tissue from the most obtained core or excisional biopsy of a tumor lesion is preferred; 20 unstained slides are preferred but a minimum of 15 slides will be acceptable; if adequate tissue is not present the patient may consent to a newly obtained biopsy Have a histologically confirmed diagnosis of:\r\n* Arm 1: melanoma, with =< 5 measurable (as defined by Response Assessment in Neuro-Oncology-Bone Marrow [RANO-BM]) new brain metastases clinically eligible for stereotactic radiosurgery (SRS); tissue diagnosis of the brain metastasis is not required for enrollment if history and imaging is consistent with melanoma and a histopathology is available from the systemic disease; however, a biopsy or surgical excision of one or more of the brain lesions may be performed, if clinically indicated; patient must consent to providing tissue from archival biopsy tissue or newly obtained excisional biopsy of a tumor lesion; newly-obtained is defined as a specimen obtained up to 6 weeks (42 days) prior to initiation of treatment on day 1\r\n* Arm 2: newly diagnosed glioblastoma (World Health Organization [WHO] grade IV) Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion; if a freshly procured research specimen has already been made available to the Pollack Lab prior to consent as part of another sample collection research protocol, may be omitted with approval of the primary investigator so long as the patient has not received anti-cancer therapy or immunosuppressive therapy since the biopsy sample was collected Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion Pathological diagnosis should be obtained by incisional or excisional tissue biopsy; core biopsy is only permissible if obtaining an incisional or excisional is not possible and if the grade can be assessed on the core biopsy Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion prior to starting study therapy or from archival tissue of a biopsy that was performed after the most recent systemic therapy Have provided tissue from a newly obtained biopsy obtained from a focus of metastatic disease (an archival tissue sample may be substituted if new biopsy cannot be obtained and by discretion of sponsor investigator) Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion after 2 cycles of therapy Have provided tissue for PD-L1 biomarker analysis from a newly obtained formalin fixed tumor tissue from a biopsy of a tumor lesion not previously irradiated; the tissue sample must be received and evaluated by the study site prior to start of treatment; fine needle aspirates are not acceptable; needle or excisional biopsies, or resected tissue is required For participants participating ONLY in the Phase 1b expansion: have submitted tissue sample from either a newly obtained core or excisional biopsy of a tumor lesion (preferred) or a recent biopsy since last documented progression of disease. For those participating ONLY in Phase 1b abemaciclib or merestinib expansions: Have submitted tumor tissue sample from a newly obtained core or excisional biopsy for a tumor lesion (preferred) or a recent biopsy taken with 3 months prior to study enrollment and following the participants most recent prior systemic treatment and be willing to undergo a biopsy procedure during the study treatment period for collection of additional tumor tissue sample. Be willing to provide archival tissue; if archival tissue is not available, or a newly obtained core or excisional biopsy of a tumor lesion will be obtained; newly-obtained is defined as a specimen obtained up to 6 weeks (42 days) prior to initiation of treatment on day 1; in cohort 9: paraganglioma-pheochromocytoma or cohort 10, where there is prominent bony disease, biopsies may not be possible due to the nature of the disease Have provided tissue for PD-L1 biomarker analysis from either archived tissue or a newly obtained core or excisional biopsy PHASE I AND PHASE II DOSE EXPANSION IN RECURRENT GBM UNDERGOING RESECTION: Be willing to provide tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Available tissue from a newly obtained core biopsy of a tumor lesion not previously irradiated Archival tissue is mandatory (a tumor biopsy-core or excisional) of a metastatic lesion obtained within 1 year prior to study registration (within 4 weeks preferred); tumor tissue from nephrectomy and site of metastasis will be requested; if archival tissue of a metastatic lesion obtained within the preceding year is not available, patients must have at least one site of disease (not including bone metastases) accessible for core needle or excisional biopsy; if archival tissue of a metastatic lesion is not available and biopsy of a new lesion is not feasible, the subject is not eligible for the study Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Be willing to consent for biopsy at baseline (if inadequate archival tissue per inclusion criteria above) and an on treatment biopsy; have a tumor in a location that in the opinion of the investigator that is amenable to biopsy or have provided tissue for PD-L1 and other biomarker analysis from a newly obtained (within 60 days) formalin fixed tumor tissue from a recent biopsy of a tumor lesion not previously irradiated; no systemic antineoplastic therapy may be administered between the PD- L1 biopsy and initiating study medication; fine needle aspirates are not acceptable; core needle or excisional biopsies, or resected tissue is required Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Have provided tumor tissue from a newly obtained core, punch, incisional or excisional tumor biopsy; patients must undergo biopsy (core, punch) or open incisional/excisional biopsy (if done as part of a clinically indicated baseline diagnostic procedure) within 4 weeks of registration on the study Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion For expansion cohort, patients must consent to provide tissue from newly obtained (during screening period) core or excisional biopsy of a tumor lesion. Patients must provide tissue from an archival tumor sample (obtained within 2 years from screening visit) or newly obtained core, punch, or excisional biopsy of a tumor lesion if deemed relatively safe and technically feasible Provided archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Provided archival tumor tissue sample or newly obtained (no anti-neoplastic therapy since biopsy) core or excisional biopsy of a tumor lesion not previously irradiated. Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Tissue from an archival tissue sample or fresh tissue obtained from a core or excisional biopsy of a tumor lesion. Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion; in the opinion of the investigator, the patient must have tumor accessible by CT or ultrasound guided core biopsy; subjects for whom newly-obtained samples cannot be provided may submit an archived specimen provided it was obtained after last systemic treatment, within 6 months of signing consent and that tissue is available for either 2 cell blocks or 20 uncut slides (core or excisional biopsy required, fine needle aspirate is not acceptable) Archival or newly obtained tissue sample of a tumor lesion. Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion obtained within 28 days prior to study enrollment Archival tissue must be available or newly obtained core or excisional biopsy of a tumor lesion Must have sufficient archival tissue block material (1.5 x 1.5 x 1.5 cm) and/or newly obtained core or excisional biopsy of tumor tissue; minimum of 2 cores Is able to provide tumor tissue from a site not previously irradiated as follows: Cohort A must provide a core or excisional biopsy from soft tissue or bone biopsy within 1 year of screening and after developing mCRPC; Cohort B: must provide an archival tumor tissue sample or tumor tissue from a newly obtained core or excisional biopsy from soft tissue if the lesion is clinically accessible; and Cohort C with soft tissue disease must provide a core or excisional biopsy from a soft tissue lesion if clinically accessible within 1 year of screening and after developing mCRPC and an archival specimen if available. Participants with bone metastasis only must provide an archival tumor tissue specimen Has provided tissue for biomarker analysis from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated from a muscle invasive urothelial carcinoma or a metastatic biopsy, originally from the original tumor. Must provide adequate tissue for biomarker analysis for Cohorts A and B from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated. Has provided archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated. Availability of tumor tissue for biomarker analysis from a newly obtained core or excisional biopsy or willing to undergo a tumor biopsy. For first line NSCLC participants only, PD-L1 expression should be 1% or higher. Have provided an archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated for PD-L1 analysis. Have provided tissue for PD-L1 analysis from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated. Archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion as required. Newly obtained core or excisional biopsy of a tumor lesion for part 2A and if they qualify, one pre-randomization biopsy for part 2B Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Previously obtained archival tumor tissue or tissue obtained from biopsy at screening Have available tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Provides an archival or newly obtained (?60 days prior to first dose of study treatment) tumor tissue sample (Cohort B). Have tissue from an archival tissue sample that has been identified and confirmed as available for study, or newly obtained core or excisional biopsy of a tumor lesion Have identified tissue from an archival tissue sample (preferably from a metastasis, but sample from primary tumor allowable) or newly obtained core or excisional biopsy of a tumor lesion. Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Can provide tissue for PD-L1 biomarker analysis from a core or excisional biopsy (fine needle aspirate is not sufficient): A newly obtained biopsy (within 90 days prior to start of study treatment) is preferred but an archival sample is acceptable. Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion Available tissue from a newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Have provided tissue from an archival tissue sample (< 6 months old) or newly obtained core biopsy of a tumor lesion before radiation therapy Patients must provide tissue from an archival tumor sample or newly obtained core, punch or excisional biopsy of a tumor lesion if deemed relatively safe and technically feasible\r\n* Note: newly obtained biopsy is preferable Able to provide tissue for biomarker analysis from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Can provide either a newly obtained or archival tissue sample for PD-L1 by immunohistochemistry analysis Has provided archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated Have provided tissue from a newly obtained core or excisional biopsy of a tumor lesion or a recent biopsy defined by ?3 years since last documented progression of disease Have provided tissue from an archival tissue sample or newly obtained core or excisional biopsy of tumor lesion. Have provided tumor tissue from a newly obtained core, punch, incisional or excisional tumor biopsy; patients must undergo biopsy (core, punch) or open incisional/excisional biopsy (if done as part of a clinically indicated baseline diagnostic procedure) within 4 weeks of registration on the study Tissue from an archival tissue sample or fresh tissue obtained from a core or excisional biopsy of a tumor lesion Has provided a tumor tissue sample (archival or newly obtained core or excisional biopsy of a tumor lesion) Has provided recently or newly obtained core or excisional biopsy from a locally recurrent inoperable or metastatic tumor lesion for central determination of TNBC status and PD-L1 expression, unless contraindicated due to site inaccessibility and/or participant safety concerns. Is able to provide an evaluable core or excisional lymph node biopsy for biomarker analysis from an archival (>60 days) or newly obtained (within 60 days) biopsy at Screening (Visit 1).