Known leptomeningeal carcinomatosis, uncontrolled/unstable spinal cord compression, or brain metastases. History of leptomeningeal disease or spinal cord compression secondary to metastasis Patient has spinal cord compression or symptomatic brain metastases. Have symptomatic or uncontrolled brain metastases, spinal cord compression, or leptomeningeal disease requiring concurrent treatment, including but not limited to surgery, radiation, and/or corticosteroids (participants receiving anticonvulsants are eligible). No concurrent leptomeningeal disease or cord compression Symptomatic brain metastases, leptomeningeal carcinomatosis, or spinal cord compression (treated metastatic brain, leptomeningeal carcinomatosis, or spinal cord compression are allowed); Note: Patients must be off steroids used for brain metastases, leptomeningeal carcinomatosis, or spinal cord compression In the dose-finding portion of the study, participants with known or suspected parenchymal brain, spinal cord, leptomeningeal disease prior to study enrollment will be excluded; in the dose-expansion portion of the study, known or suspected parenchymal brain or spinal cord disease, and/or suspected or symptomatic leptomeningeal disease prior to study enrollment will be excluded; asymptomatic leptomeningeal disease only will be allowed in the dose-expansion cohort Have symptomatic or uncontrolled brain metastases, spinal cord compression, or leptomeningeal disease requiring concurrent treatment. Known brain metastases or spinal cord compression PHASE II STUDY COHORT OVARIAN CANCER ELIGIBILITY CRITERIA (MEDI+O, MEDI+C AND MEDI+O+C):\r\nPatients with evidence of CNS metastasis, spinal cord compression, or leptomeningeal disease within one year prior to enrollment will be excluded from this clinical trial; patients with a remote history of brain metastases may be considered if they received sterilizing therapy to the CNS (resection or radiation) and have been CNS progression free for the -year period; baseline imaging to rule out brain metastases is not required for screening, but should be performed prior to study enrollment if clinically indicated; patients with spinal cord compression may be considered if the condition is medically managed and currently asymptomatic PHASE II STUDY COHORT TRIPLE NEGATIVE BREAST CANCER ELIGIBILITY CRITERIA (MEDI+O ONLY):\r\nPatients with evidence of CNS metastasis, spinal cord compression, or leptomeningeal disease within six months prior to enrollment will be excluded from this clinical trial; patients with a remote history of brain metastases may be considered if they received sterilizing therapy to the CNS (resection or radiation) and have been CNS progression free for the six months period; baseline imaging to rule out brain metastases is not required for screening, but should be performed prior to study enrollment if clinically indicated; patients with spinal cord compression may be considered if the condition is medically managed and currently asymptomatic PHASE II STUDY METASTATIC CASTRATE-RESISTANT PROSTATE CANCER COHORT ELIGIBILITY CRITERIA (MEDI+O ONLY):\r\nPatients with evidence of CNS metastasis, spinal cord compression, or leptomeningeal disease within year prior to enrollment will be excluded from this clinical trial; patients with a remote history of brain metastases may be considered if they received sterilizing therapy to the CNS (resection or radiation) and have been CNS progression-free for the -year period; baseline imaging to rule out brain metastases is not required for screening, but should be performed prior to study enrollment if clinically indicated; patients with spinal cord compression may be considered if the condition is medically managed and currently asymptomatic Have symptomatic leptomeningeal carcinomatosis or spinal cord compression. Patients with asymptomatic leptomeningeal disease and no evidence of spinal cord compression are allowed. Spinal cord compression or brain metastases Patients with untreated brain metastases, spinal cord compression, or leptomeningeal carcinomatosis are excluded from this clinical trial; patients with brain metastases or spinal cord compression previously treated with radiation and/or surgery are allowed if local treatment was > days ago, most recent MRI demonstrates stability or decrease in size of all lesions, and the patient has no current neurologic symptoms related to the metastases and treatment and no requirement for corticosteroids related to the prior treatment Known or suspected brain metastasis or active leptomeningeal disease or spinal cord compression Patient must not have known symptomatic leptomeningeal or brain metastases or spinal cord compression History of central nervous system (CNS) lymphoma, leptomeningeal disease or spinal cord compression. Subject has symptomatic brain metastases, spinal cord compression, or intractable back pain due to compression of destructive mass. Presence of, or history of, central nervous system (CNS) lymphoma, leptomeningeal disease or spinal cord compression. Patients with known leptomeningeal or brain metastases or spinal cord compression should be excluded from this clinical trial Have current spinal cord compression (symptomatic or asymptomatic and detected by radiographic imaging). Patients with leptomeningeal disease and without cord compression are allowed. have previously documented brain metastases, leptomeningeal disease, or uncontrolled spinal cord compression Has documented brain metastases, leptomeningeal disease, or uncontrolled spinal cord compression. Have documented brain metastases, leptomeningeal disease or uncontrolled spinal cord compression. Brain metastases or spinal cord compression. Spinal cord compression, leptomeningeal carcinomatosis or active symptomatic brain metastases Known spinal cord compression or brain or liver metastasis Unstable brain metastases or spinal cord compression The participant has documented brain metastases, leptomeningeal disease, or uncontrolled spinal cord compression. Patients with known brain metastases or spinal cord compression should be excluded from this clinical trial Patients with history of brain metastases, spinal cord compression, or a history of leptomeningeal carcinomatosis; Patients with history of brain metastases, spinal cord compression, or leptomeningeal carcinomatosis Current leptomeningeal metastases or spinal cord compression due to disease. Uncontrolled brain or spinal cord metastases Evidence of ongoing spinal cord compression or leptomeningeal carcinomatosis Leptomeningeal metastases or spinal cord compression due to disease. Have symptomatic or uncontrolled brain metastases, spinal cord compression, or leptomeningeal disease requiring concurrent treatment Brain metastases, or spinal cord compression. Individuals with brain metastases are allowed if they have been treated with irradiation or surgery, are clinically stable without steroid treatment. Individuals with documented leptomeningeal disease are not eligible. Symptomatic leptomeningeal, brain metastases, or spinal cord compression. Known leptomeningeal involvement, brain metastases or spinal cord compression. History of leptomeningeal disease or spinal cord compression secondary to metastasis. Subjects with leptomeningeal or brain metastases or spinal cord compression. Subjects with CNS symptoms should undergo a CT scan or MRI of the brain to exclude new or progressive brain metastases. Spinal cord metastasis is acceptable. However, subjects with spinal cord compression should be excluded. History of or known presence of brain or spinal cord metastases Has brain metastases, uncontrolled spinal cord compression, or leptomeningeal disease Previous brain metastases, leptomeningeal disease, or uncontrolled spinal cord compression. History of leptomeningeal disease or spinal cord compression Known or suspected brain metastasis or active leptomeningeal disease or spinal cord compression