A Study to Evaluate INCA033989 Administered as a Monotherapy or in Combination With Ruxolitinib in Participants With Myeloproliferative Neoplasms

Inclusion Criteria:

* Life expectancy \> 6 months.
* Willingness to undergo a pretreatment and regular on-study BM biopsies and aspirates (as appropriate to disease).
* Existing documentation from a qualified local laboratory of CALR exon-9 mutation.
* Participants with MF and ET as defined in the protocol.

Exclusion Criteria:

* Presence of any hematological malignancy other than ET, PMF, or post-ET MF.
* Active invasive malignancy over the previous 2 years.
* Active HBV/HCV, HIV.
* History of clinically significant or uncontrolled cardiac disease.
* Has undergone any prior allogenic or autologous stem-cell transplantation or such transplantation is planned.
* Laboratory values outside the Protocol-defined ranges.
* Participants undergoing treatment with G-CSF, GM-CSF, or TPO-R agonists at any time within 4 weeks before the first dose of study treatment.
* Prior history of major bleeding, or thrombosis within the last 3 months prior to study enrollment.
* Any prior chemotherapy, immunomodulatory drug therapy, immunosuppressive therapy, biological therapy, endocrine therapy, targeted therapy, antibody, or hypomethylating agent used to treat the participant's disease within 5 half-lives or 28 days (whichever is shorter) before the first dose of study treatment.
* For TGBs only: Undergoing treatment with a potent/strong inhibitor or inducer of CYP 3A4/5 within 14 days or 5 half-lives (whichever is longer) before the first dose of study treatment, or expected to receive such treatment during the study.

Other protocol-defined Inclusion/Exclusion Criteria may apply.