aGvHD grades: Grade 0- no organ involvement (ie, Stage 0 skin, Stage 0 liver, and Stage 0 GI); Grade I-Stage 1 - 2 skin without liver/GI involvement; Grade II- Stage 3 skin and / or Stage 1 liver and / or Stage 1 GI; Grade III- Stage 2 - 3 liver and / or Stage 2 - 3 GI; Grade IV- Stage 4 skin and / or Stage 4 liver and/or Stage 4 GI.

Time to response is defined as the time from the date of the first treatment administration to the date of response.

Duration is calculated from time from the first OR (CR or PR) until the time point of no aGvHD response in comparison to baseline.

Best OR is defined as the achievement of an OR at any time point up to and including Day 28. Number of participants with best OR will be reported.

The cumulative dose of steroids given for SR-aGvHD per kg of body weight from baseline until Day 60 and until Visit Month 24 will be analyzed.

Number of participants with cGvHD will be reported.

Time to cGvHD is defined as the time between the last day of haematopoietic stem cell transplantation (HSCT) to the first episode of cGvHD.

Number of participants with GF will be reported.

Number of participants with relapse or progression in participants with underlying malignant disease will be reported.

Time to relapse or progression in participants with underlying malignant disease will be reported.

EFS is defined as the time from the date of randomization to the date of the event. An event is defined as GF, relapse or progression of the underlying disease, or death due to any cause.

NRM is defined as the time from the date of randomisation to the date of the event. An event is defined as death without previous relapse or progression of the underlying disease.

Severity will be graded based on Common Terminology Criteria for Adverse Events (CTCAE) v5.0: Grade 1- Mild; Grade 2- Moderate; Grade 3- Severe; Grade 4- Life-threatening consequences; urgent intervention indicated; Grade 4- Death related to the AE.

The Karnofsky performance score (KPS), which is reported on an ordinal scale from 0 to 100, provides a rough measure of the participant's well-being, including their ability to conduct activities of daily living and functional capacity. Higher score indicates normal, no complaints and no evidence of disease.

A Lansky score (recipient age greater than or equal to [>=] 1 years and less than [<] 16 years) will be recorded pre-treatment and measured serially at regular intervals after treatment. The score is a standard performance score that measures overall function of the child with a scale range from 0 to 100. Higher score indicates full activeness.

EQ-5D-5L is a 2-part instrument for use as a measure of health outcome, designed for self-completion by respondents. It consists of EQ-5D-5L descriptive system and EQ VAS. EQ-5D-5L descriptive system comprises of 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each has 5 levels of perceived problems (1-no problem, 2-slight problems, 3-moderate problems, 4-severe problems, 5-extreme problems). Participant selects answer for each of 5 dimensions considering response that best matches his/her health "TODAY". Responses were used to generate a HSI. HSI ranges from 0 (dead) to 1.00 (full health).

EQ-5D-5L is a 2-part instrument for use as a measure of health outcome, designed for self-completion by respondents. It consists of EQ-5D-5L descriptive system and EQ VAS. The EQ VAS self-rating records the respondent's own assessment of his or her overall health status at the time of completion, on a scale of 0 (the worst health you can imagine) to 100 (the best health you can imagine).

The FACT-BMT questionnaire was designed to measure the quality of life in subjects undergoing bone marrow (BM) transplantation. It consists of the following categories of assessment: physical well-being, social / family well-being, emotional well-being, functional well-being, and additional miscellaneous concerns that the subject may have concerning their healthcare, persons involved in their life, and other emotions and incapabilities. Score ranges from 0-164, with higher score indicating better quality of life.