A Study of ARGX-110 in Combination With Azacytidine in Participants With Newly Diagnosed Acute Myeloid Leukemia (AML) or High Risk Myelodysplatic Syndrome (MDS)

DLTs will be defined as any of the following drug-related events: Any grade 3 or higher drug related non-hematological toxicity or; Grade 3 or higher IRRs or; inability to administer the next dose due to a drug-related adverse event or a delay of the administration of the next dose due to toxicities for more than 14 days despite adequate medication or; drug-related grade 4 febrile neutropenia or; drug-related grade 4 anemia which cannot be adequately treated.

ORR is defined as the sum of Complete remission (CR), CR with incomplete recovery (CRi), morphologic leukemia-free state (MLFS), partial remission (PR) at the ARGX-110 RP2D level that was established in Phase 1 according to established response criteria for Acute myeloid leukemia (AML).

An AE is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product.

Cmax is the maximum observed concentration.

Ctrough is defined as the observed serum concentration before dosing or at the end of the dosing interval.

AUC(0-infinity) is defined as area under the serum analyte concentration-time curve from time 0 to infinite time of ARGX-110.

AUCtau is the area under the serum concentration-time curve during the dosing interval.

Vd/F is defined as Dose/[Lambda (z)*AUC (0-infinity)].

CL is the total systemic clearance of drug after intravenous (IV) administration.

t1/2 is defined as the time measured for the serum concentration to decrease by 1 half of its original concentration.

Minimal residual disease assessments will be performed on bone marrow aspirates and/or whole blood by flow cytometry.

Venous blood samples and bone marrow aspirate will be used to evaluate presence of anti-drug antibodies to ARGX-110. Participants with titer of confirmed positive samples for ARGX-110 antibodies will be reported.

Complete remission is defined as number of participants who have bone marrow blasts less than (<) 5 percent (%); absence of blasts with Auer rods; absence of extramedullary disease; absolute neutrophil count greater than (>) 1.0 * 10^9 per liter (L) (1000 per microliter [µL]); platelet count > 100 * 10^9/L (100.000/mc); independence of red cell transfusions.

CRi is defined as number of participants who have all CR criteria except for residual neutropenia (< 1.0 * 10^9/L [1000/mc]) or thrombocytopenia (< 100 * 10^9/L [100.000/mc]).

MLFS is defined as number of participants who have bone marrow blasts < 5%; absence of blasts with Auer rods; absence of extramedullary disease; no hematologic recovery required.

PR is defined as number of participants who have all hematologic criteria of CR; decrease of bone marrow blast percentage to 5% to 25%; and decrease of pretreatment bone marrow blast percentage by at least 50%.

Time to response is defined as response measured from the time from first dose of study drug to date of response (CR, CRi, MLFS, PR).

Duration of response is defined as the date of achievement of a response (CR, CRi, MLFS, PR) until the date of relapse.

RFS is defined as disease relapse or participant death from any cause; measured from the date of achievement of a remission (CR, CRi) until the date of relapse or death from any cause.

OS is defined as death from any cause; measured from the date of first dose to the date of death from any cause.

Number of participants with 30 Day and 60 Day Mortality will be reported.

Number of participants reaching greater than or equal to (>=) 8 consecutive weeks without red blood cell (RBC-TI) and/or platelet (PLT-TI) transfusion. The first day of the >=8-week period with no transfusions is noted as the time at which participants first achieved TI.

Time until TI for RBC and/or PLT will be measured from the date of entry into a study to the first day of the 8-weeks period with no transfusions.

Time between the last transfusion before the start of the TI period and the first transfusion after the start of the TI period, which occurred >=8 weeks later.

Time to neutrophil recovery will be calculated from number of days from Day 1 of commencing study treatment to first day neutrophils 0.5 * 10^9 per liter or 1.0 * 10^9 per liter.

Time to platelet recovery will be calculated from number of days from day 1 of commencing study treatment to first day neutrophils 50 * 10^9 per liter or 100 * 10^9 per liter.

Biomarkers including CD70 and CD27 assessment will be performed on bone marrow aspirates and/or whole blood.

Levels of T, B and NK cells will be reported by immunophenotyping (performed by flow cytometry or mass cytometry). .

Levels of B cells will be reported.

Levels of NK cells will be reported.