Multi-peptide Vaccination and Bispecific PSMAxCD3 Antibody Treatment in Patients With Prostate Cancer

Inclusion Criteria: * Understand and voluntarily sign an IC document prior to any study related assessments/procedures * Understand and voluntarily sign an IC document prior to any study related assessments/procedures * Patient is able to understand and comply with the protocol for the duration of the study including treatment and scheduled visits and examinations * Men aged ≥ 18 and ≤80 years * Histologic diagnosis of prostatic adenocarcinoma * Biochemical recurrence (BCR): PSA recurrence after treatment with curative intent; PSA ≥0.2 ng/mL or PSA \> nadir + 2 ng/mL (after definitive RT), with two increasing PSA values prior to study treatment; AND no distant metastasis upon PSMA-PET imaging * Patients are ineligible to receive available treatment alternatives * Low risk of rapid disease progression, defined as: o PSA-DT \> 1 year AND pathological ISUP grade \< 4 for men with prior RP OR Interval to BCR \> 18 months AND biopsy ISUP grade \< 4 for men with prior radiation therapy * In case of second relapse PSA-DT \> 9 months * Eastern Cooperative Oncology Group (ECOG) performance status ≤1 Exclusion Criteria: * • PSA \>5 ng/mL (at screening) * Patients who are receiving or have previously received androgen deprivation treatment. Except testosterone has recovered to normal levels: patients who have previously received anti-hormonal treatment testosterone must be \>12 nmol/l. * Patients who are planned to or are undergoing salvage therapy (e.g. radiation) * Clinically significant xerostomia (dry mouth \>1grade according to CTCAE v6.0) * Untreated current or prior distant metastasis of PC * Other malignancy within the last 2 years except: adequately treated non-melanoma skin cancer and non-muscle invasive bladder cancer. * Concurrent or previous treatment within 30 days in another interventional clinical trial with an investigational anti-cancer therapy * Clinical signs of active infection (\> grade 2 according to CTCAE v6.0) * History of HIV infection * Viral active or chronic hepatitis (HBV or HCV) * Autoimmune disease that requires or has required treatment with systemic immunosuppressive treatments, except low dose corticosteroids (\< 10 mg/ day), in the past 1 year * Ongoing relevant CNS pathology (e.g. seizure, paresis, aphasia, cerebrovascular ischemia, severe brain injuries, dementia, Parkinson's disease, cerebellar disease, organic brain syndrome, psychosis, coordination or movement disorder) * Epilepsy requiring pharmacologic treatment * Major surgery within 4 weeks of starting study treatment. Patients must have recovered from any effects of major surgery. * Heart failure NYHA III/IV * Severe obstructive or restrictive ventilation disorder * Known intolerance to CC-1, or other immunoglobulin drug products as well as hypersensitivity to any of the excipients present in the respective drug products (CC-1, VAC-XS15-PC01) * Refrain from blood donation during the course of the study * Male patients have to refrain from sperm donations for 6 months after last IMP