Participants will receive SC or IV injection of Cusatuzumab 20 mg/kg.

Time to transformation of participants to AML will be reported. Transformation to AML is defined as >= 20% bone marrow blasts.

PFS is defined as the time from randomization to disease progression; relapse from CR, PR, or mCR; or death from any cause.

OS is defined as the time from randomization to death.

Hematologic improvement rate is defined as erythroid response (pretreatment, less than (<) 11 g/dL; hemoglobin >= 1.5 g/dL; relevant reduction of units of RBC transfusions by an absolute number of >= 4 Red blood cell (RBC) transfusions/8 weeks compared with the pretreatment transfusion number in the previous 8 weeks. Only RBC transfusions given for a hemoglobin of <= 9.0 g/dL pretreatment will count in the RBC transfusion response evaluation; platelet response (pretreatment <100*10^9/L); absolute increase of >= 30*109/L for participants starting with >20*10^9/L platelets; increase to >20*109/L and by >= 100% for participants starting with <= 20*109/L platelets; Neutrophil response (pretreatment <1.0×10^9/L); and at least 100% increase and an absolute increase of >0.5*10^9/L.

An adverse event 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.

Percentage of participants with clinically significant abnormalities in laboratory parameters will be reported.

The AUC(t1-t2) is the area under the serum concentration-time curve within timespan t1 to t2.

Cmax is the maximum observed serum concentration.

Cmin is the minimum observed serum concentration.

T1/2 is the time measured for the serum concentration to decrease by 1 half to its original concentration. It is associated with the terminal slope of the semi logarithmic drug concentration-time curve, and is calculated as 0.693/lambda(z).

CL is a quantitative measure of the rate at which a drug substance is removed from the body.

The Vz is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired blood concentration of a drug.

Venous blood samples are analyzed for presence of antidrug antibodies to cusatuzumab. Participants with titer of confirmed positive samples for cusatuzumab antibodies are reported.

Percentage of participants achieving CR and PR as per IWG criteria will be reported.

Time to response for participants who achieved CR, PR and mCR responses, defined as time from randomization to achieving the first response of CR, PR, or mCR as per modified IWG criteria.

Time from achieving the first response of CR, PR, or mCR to relapse or death from any cause for those participants who responded.

FACT-An is a scale in Functional Assessment of Chronic Illness Therapy Measurement System. It consists of Functional Assessment of Cancer Therapy (general version; FACT-G) and 20 questions labeled "additional concerns" that measure anemia/fatigue. FACT-G is 27-item compilation of general questions divided into 4 primary quality of life domains: physical well-being, social/family well-being, emotional wellbeing, and functional well-being. Participants will be asked to rate scale items as it applies to past 7 days, on 5-point scale (0=Not at all, 1=A little bit, 2=Somewhat, 3=Quite a bit, 4=Very much). Negatively stated items will be reversed by subtracting the response from 4. After reversing the proper items, items are summed to a total to generate a score on (sub)scale. A summary Trial Outcome Index total score (FACT An TOI) will be calculated by summing physical well being, functional well being, and anemia symptoms subscales and higher is the score better is the quality of life.