A Study of JNJ-90189892 for Relapsed or Refractory Acute Myeloid Leukemia or Myelodysplastic Neoplasms

Inclusion Criteria:

* A. For Parts 1, 2, and 3: Have a diagnosis, per the world health organization (WHO) 2022 criteria, of (a) Parts 1, 2, and 3: Acute myeloid leukemia (AML) or (b) Parts 1 and 2: Moderate high, high, or very high-risk myelodysplastic neoplasms (MDS) per Molecular International Prognostic Scoring System (IPSS-M); B. For Part 4 only: Previously untreated acute myeloid leukemia (AML) per the WHO 2022 criteria

* Body weight that is greater than or equals to (>=) 40 kg

* Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2

* Have adequate renal function defined as Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Estimated Glomerular Filtration Rate (eGFR) >=40 milligrams per minute (mL/min) computed with the calculator on the national kidney foundation website

* Participants must have laboratory parameters in the required range

Exclusion Criteria:

* Has a medical history of clinically significant pulmonary compromise, particularly the current need for supplemental oxygen use to maintain adequate oxygenation

* Has evidence of uncontrolled systemic viral, bacterial, or fungal infection. Antimicrobial prophylaxis is permitted

* All participants- Has known allergies, hypersensitivity, or intolerance to JNJ-90189892 or its excipients; Parts 3 and 4- Has known allergies, hypersensitivity, or intolerance to venetoclax (VEN), azacitadine (AZA), or their excipients

* Had major surgery or had significant traumatic injury within 14 days of planned first dose of JNJ-90189892

* Had a prior or concurrent second malignancy with natural history or treatment likely to interfere with any study endpoints of safety or the efficacy of the study treatment

* Has known active central nervous system involvement