An Extension Study of Bomedemstat (IMG-7289/MK-3543) in Participants With Myeloproliferative Neoplasms (IMG-7289-CTP-202/MK-3543-005)

Inclusion Criteria: Inclusion Criteria include, but are not limited to: * Has completed at least one Treatment Period (TP) in a prior bomedemstat Myeloproliferative Neoplasms (MPN) protocol (such as, but not limited to, IMG-7289-CTP-102/MK-3543-002 (NCT03136185) and IMG-7289-CTP-201/MK-3543-003) (NCT04254978). * In the estimation of the Investigator, the risk-benefit favors continued dosing with bomedemstat. Exclusion Criteria: Exclusion Criteria include, but are not limited to: * Ongoing participation in another investigational study (except observational studies). * A history of non-compliance in a prior bomedemstat study (excluding dose suspensions that were medically warranted). * Current use of a prohibited medication (e.g., romiplostim). * Medical, psychiatric, cognitive, or other conditions that, in the Investigator's opinion, compromise the patient's safety, ability to give informed consent, or comply with the trial protocol. * Is pregnant or breastfeeding or plan to become pregnant or breastfeed during the study. * Women of childbearing potential (WOCBP) and fertile men unwilling to agree to use an approved method of contraception from time of enrollment until 14 days after last bomedemstat dose.