A Study of VAC85135, a Neoantigen Vaccine Regimen, Concurrently Administered With Ipilimumab for the Treatment of Myeloproliferative Neoplasms

Inclusion Criteria:

Be positive for a CALR (calreticulin) mutation: Type 1 or Type 2; Type 1-like, or Type 2-like may be considered with Sponsor approval; or positive for the JAK2V617F (Janus kinase 2 with valine 617 to phenylalanine mutation) mutation with HLA-A02:01 (human leukocyte antigens) per medical history or local testing
Have an Eastern Cooperative Oncology Group (ECOG) performance status grade of 0 or 1 or 2
Have the following hematologic laboratory values: Leukocytes greater than or equal to (>=) 1.5*10^9 per liter, Neutrophils >=1.0*10^9 per liter, Platelets >=20*10^9 per liter, Hemoglobin greater than (>) 7 gram per deciliter (g/dL)
Have the following chemistry laboratory values: Alanine aminotransferase (ALT): less than or equal to (<=) 3*upper limit of normal (ULN), Aspartate aminotransferase (AST): <=3*ULN, Total bilirubin: <=1.5*ULN, and glomerular filtration rate >=40 milliliter per minute (mL/min)
A female participant of childbearing potential must agree to all the following during the study and for 6 months after the last dose of study treatment: use a barrier method of contraception, use a highly effective preferably user-independent method of contraception, not to donate eggs (ova, oocytes) or freeze for future use for the purposes of assisted reproduction, not plan to become pregnant, not to breast-feed
A male participant must agree to all the following during the study and for 90 days after the last dose of study treatment: wear a condom when engaging in any activity that allows for passage of ejaculate to another person, not to father a child, not to donate sperm or freeze for future use for the purpose of reproduction

Exclusion Criteria:

History of any significant medical condition per investigators judgment (example: severe asthma/chronic obstructive pulmonary disease (COPD), poorly regulated heart condition, insulin dependent diabetes mellitus)
Serious known clinically relevant allergies or earlier anaphylactic reactions
Currently pregnant or breastfeeding
Prior treatment with any Janus kinase 1/2 (JAK1/2) inhibitor
Known sensitivity or contraindications to the use of Ipilimumab per local prescribing information