Inclusion Criteria:  1. Histologically confirmed metastatic or locally advanced inoperable NSCLC, ovarian cancer, or prostate cancer that have already received at least 1 line of approved cancer therapy and either: exhausted current recognized treatment options; or are stable in a planned treatment-free interval following completion of a set course of treatment; or in the case of prostate cancer, are currently stable on an antihormonal treatment.  2. Are not receiving active cancer treatment other than supportive therapies or androgen deprivation therapies for prostate cancer, which may be continued, and, in the opinion of the investigator, are not anticipated to require further approved cancer treatment options until the Week 8 assessment (up to 9 weeks) after the first dose of OVM-200 per standard of care.  3. At least 1 measurable lesion that can be accurately assessed at baseline by computed tomography (CT)/magnetic resonance imaging (MRI) and is suitable for repeated assessment (NSCLC only).  4. Age ≥ 18 years and ≤ 75 years. 5. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Section 7.2.6).  6. Predicted life expectancy ≥ 3 months. 7. Adequate bone marrow, renal, and hepatic function.  Exclusion Criteria:  Known history or evidence of significant immunodeficiency due to underlying illness. Patients with a condition requiring systemic treatment with either corticosteroids (> 10 mg daily prednisolone equivalent) or other immunosuppressive medications within 14 days of the first dose of study drug. Inhaled or topical steroids and adrenal replacement steroids are permitted in the absence of autoimmune disease. Patients with a history of or active, known, or suspected autoimmune disease or a syndrome that requires systemic or immunosuppressive agents. Patients with vitiligo, type I diabetes mellitus, residual hypothyroidism due to autoimmune disease only requiring hormone replacement, psoriasis not requiring systemic treatment, or conditions not expected to recur in the absence of an external trigger are permitted to enrol. Prior therapy with an anticancer vaccine; anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or anti-CTLA-4 antibody; or any other antibody or drug specifically targeting T-cell co-stimulation or immune checkpoint pathways in the 28 days before the first dose of study drug. Administration of an investigational drug in the 28 days or 6 half-lives (whichever is longer) before the first dose of study drug. Major surgery or treatment with any chemotherapy, or radiation therapy for cancer in the 28 days before the first dose of study drug. Active infection requiring antibiotics or physician monitoring, or recurrent fevers (> 38.0°C) associated with a clinical diagnosis of active infection. Active viral disease, positive test for hepatitis B virus using hepatitis B surface antigen test, or positive test for hepatitis C virus (HCV) using HCV ribonucleic acid or HCV antibody test indicating acute or chronic infection. Positive test for human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome; testing is not required in the absence of history. Receipt of any vaccine within 28 days before the first dose of study drug. Other prior malignancy within the previous 3 years, except for local or organ-confined early stage cancer that has been definitively treated with curative intent and does not require ongoing treatment, has no evidence of residual disease, and has a negligible risk of recurrence and is therefore unlikely to interfere with the primary and secondary endpoints of the study, including response rate and safety and tolerability. Symptomatic brain metastases or any leptomeningeal metastasis. Any serious or uncontrolled medical disorder (including cardiovascular, respiratory, renal, or autoimmune disease) that, in the opinion of the investigator or the medical monitor, may increase the risk associated with study participation or study drug administration, impair the ability of the patient to receive protocol therapy, or interfere with the interpretation of study results. History of allergic reaction or hypersensitivity to any component of the OVM-200 therapeutic vaccine or adjuvant.