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, orType 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 1or 2

• Have the following hematologic laboratory values: Leukocytes greater than or equalto (>=) 1.510^9 per liter, Neutrophils >=1.010^9 per liter, Platelets >=20*10^9per liter, Hemoglobin greater than (>) 7 gram per deciliter (g/dL)

• Have the following chemistry laboratory values: Alanine aminotransferase (ALT): lessthan or equal to (<=) 3upper limit of normal (ULN), Aspartate aminotransferase (AST): <=3ULN, Total bilirubin: <=1.5*ULN, and glomerular filtration rate >=40milliliter per minute (mL/min)

• A female participant of childbearing potential must agree to all the followingduring the study and for 6 months after the last dose of study treatment: use abarrier method of contraception, use a highly effective preferably user-independentmethod of contraception, not to donate eggs (ova, oocytes) or freeze for future usefor the purposes of assisted reproduction, not plan to become pregnant, not tobreast-feed

• A male participant must agree to all the following during the study and for 90 daysafter the last dose of study treatment: wear a condom when engaging in any activitythat allows for passage of ejaculate to another person, not to father a child, notto 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 heartcondition, 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 localprescribing information