Patient description: The patient is a 35-year-old woman with myasthenia gravis, class IIa. She complains of diplopia and fatigue and weakness that affects mainly her upper limbs. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She takes pyridostigmine 60 mg three times a day. But she still has some symptoms that interfere with her job. She is a research coordinator and has 3 children. Her 70-year-old father has hypertension. She does not smoke or use illicit drugs. She drinks alcohol occasionally at social events. Her physical exam and lab studies were not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Advanced Malignancies Advanced Cancer Participant has locally-advanced (unresectable) or metastatic solid tumor malignancy that is confirmed by available pathology records or current biopsy. Participant must also have received all standard therapies (unless the therapy is contraindicated or intolerable) appropriate to provide clinical benefit for his/her specific tumor type. However, participants with metastatic melanoma who have not received checkpoint inhibitors [CPIs] (i.e., CPIs naive) may enroll in the Phase 2 Combination Therapy Arm Dose Expansion Cohort to receive CPI: Pembrolizumab Participant must be diagnosed with solid tumor known to express WT1 antigen such as, but not limited to melanoma, ovarian cancer or Colorectal Cancer (CRC) Participant consents to provide an archival tumor specimen in a tissue block or unstained serial slides, if available, prior to study treatment Participant has an Eastern Cooperative Oncology Group (ECOG) Performance Status of ≤ 2 Participant's last dose of prior antineoplastic therapy, including any immunotherapy, was 21 days or 5 half-lives, whichever is shorter, prior to initiation of IP administration. A participant with BRAF gene, epidermal growth factor receptor (EGFR) or anaplastic lymphoma kinase (ALK) mutation positive non-small cell lung carcinoma is allowed to remain on epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) or anaplastic lymphoma kinase (ALK) or BRAF inhibitor therapy until 4 days prior to the start of Investigational Product (IP) administration Participant has completed any radiotherapy (including stereotactic radiosurgery) at least 2 weeks prior to IP administration Participant's Adverse Events (AEs) (excluding alopecia) from prior therapy have improved to grade 1 or baseline within 14 days prior to start of IP Participant has adequate organ function prior to start of IP. If a participant has received a recent blood transfusion, the laboratory tests must be obtained ≥ 4 weeks after any blood transfusion A female participant is eligible to participate if she is not pregnant and at least 1 of the following conditions applies Not a woman of childbearing potential (WOCBP) OR  Participant weighs < 45 kg at screening Participant has received investigational therapy (other than an investigational EGFR TKI in a participant with EGFR activating mutations or ALK or BRAF inhibitor in a participant with an ALK mutation) within 21 days or 5 half-lives, whichever is shorter, prior to start of IP Participant requires or has received systemic steroid therapy or any other immunosuppressive therapy within 14 days prior to Cycle 1 Day 1. Participants using a physiologic replacement dose of hydrocortisone or its equivalent (defined as up to 30 mg per day of hydrocortisone up to 10 mg per day of prednisone) are allowed Participant has symptomatic central nervous system (CNS) metastases or participant has evidence of unstable CNS metastases even if asymptomatic (e.g., progression on scans). Participants with previously treated CNS metastases are eligible, if they are clinically stable and have no evidence of CNS progression by imaging for at least 4 weeks prior to start of IP and are not requiring immunosuppressive doses of systemic steroids (> 30 mg per day of hydrocortisone or > 10 mg per day of prednisone or equivalent) for longer than 2 weeks Participant has an active autoimmune disease. Participants with type 1 diabetes mellitus, endocrinopathies stably maintained on appropriate replacement therapy or skin disorders (e.g., vitiligo, psoriasis or alopecia) not requiring systemic treatment are allowed Participant was discontinued from prior immunomodulatory therapy due to a grade ≥ 3 toxicity that was mechanistically related (e.g., immune related) to the agent Participant has known history of serious hypersensitivity reaction to a known ingredient of ASP7517 or pembrolizumab or severe hypersensitivity reaction to treatment with another monoclonal antibody Participant has a known history of human immunodeficiency virus Participant with known history of positive hepatitis B surface antigen or isolated hepatitis B core antibody (including acute HBV or chronic HBV) or hepatitis C ([HCV] ribonucleic acid [RNA] detected by qualitative assay). Hepatitis C RNA testing is not required in participants with negative hepatitis C antibody testing Participant has received a live vaccine against infectious diseases within 28 days prior to initiation of IP