Study of INCA036978 in Participants With Myeloproliferative Neoplasms

Inclusion Criteria:

* Life expectancy \> 6 months.
* Willingness to undergo a pretreatment and limited on-study BM biopsies and aspirates (as appropriate to disease).
* Participants with MF, PV and ET as defined in the protocol.

Exclusion Criteria:

* Presence of any hematological malignancy other than MF, PV, or ET.
* Malignancy within the last 3 years prior to enrollment.
* Acute or chronic HBV, Active HCV or known HIV or tuberculosis infection.
* Clinically significant or uncontrolled cardiac disease.
* Has undergone any prior allogeneic stem-cell transplantation or such transplantation is planned in the next 6 months.
* Laboratory values outside the Protocol-defined ranges.
* Prior history of major bleeding or thrombosis within the last 3 months prior to study enrollment.
* Presence of chronic or current active infectious disease requiring systemic treatment.
* Treatment with an MPN-directed therapy (approved or investigational) within the per protocol threshold before the administration of study drug.
* Prior radiation therapy within 28 days before the first dose of study treatment.

Other protocol-defined Inclusion/Exclusion Criteria may apply.