Mobilization of hematopoietic stem cells by plerixafor alone in children: a sequential Bayesian trial

Area of Science:

• Pediatric Hematology
• Stem Cell Mobilization
• Oncology

Background:

• Plerixafor (Mozobil®) demonstrates rapid hematopoietic stem cell kinetics, making it of interest for pediatric applications.
• A prospective trial was designed to assess the efficacy of a one-day plerixafor-only mobilization in pediatric cancer patients.

Purpose of the Study:

• To determine if a single-day plerixafor mobilization regimen is sufficient for collecting adequate hematopoietic stem cells in children with cancer.
• To evaluate the safety and kinetics of plerixafor in this pediatric population.

Main Methods:

• A phase IIA, Bayesian single-center prospective study enrolled children with solid malignancies.
• Mobilization involved a single subcutaneous injection of 240 μg/kg plerixafor.
• Apheresis commenced 5 hours post-injection if CD34+ cell count exceeded 10 × 10^6/L; the primary endpoint was collecting ≥ 5 × 10^6 CD34+/kg.

Main Results:

• None of the 5 patients met the primary success criterion for CD34+ cell collection.
• All patients achieved the threshold CD34+ cell count for apheresis eligibility within 4-6 hours post-injection.
• The median collected CD34+ cell yield was 1.62 × 10^6/kg, with 3 patients exceeding 1.5 × 10^6/kg.

Conclusions:

• A one-day plerixafor mobilization in children is faster and shorter than in adults but did not meet the primary efficacy endpoint in this study.
• The observed rapid kinetics and lack of side-effects suggest plerixafor may be a valuable option for completing insufficient grafts after further optimization.
• Additional research is necessary to refine plerixafor utilization strategies in pediatric stem cell mobilization.