What medicines given as a subcutaneous (SC) injection can help the body create more stem cells and release them into circulation for harvesting?

Medications for Stem Cell Mobilization via Subcutaneous Injection

Granulocyte-Colony Stimulating Factor (G-CSF) is the primary medication given subcutaneously to mobilize stem cells into circulation for harvesting, with filgrastim being the standard agent at 10 mcg/kg/day for 4-5 days before collection begins. 1

Primary Mobilization Agents

G-CSF (Filgrastim and Biosimilars)

• Standard dosing: 10-32 mcg/kg/day subcutaneously for 4-5 days 1
  • Begin apheresis (collection) on day 4 or 5
  • Higher doses in the range (closer to 10 mcg/kg twice daily) may yield better stem cell collection 2
• Available forms:
  • Filgrastim (original)
  • Tbo-filgrastim (biologic, not biosimilar) 1
  • Filgrastim-sndz (biosimilar) 1

Pegfilgrastim

• Limited data suggest it may be equivalent to G-CSF for mobilization 1
• Standard dose: 6 mg subcutaneously as a single dose 1
• Not currently indicated specifically for stem cell mobilization in product labeling 1

GM-CSF (Sargramostim)

• Can be used as a single agent for mobilization, though G-CSF is more widely utilized 1
• Standard dose: 250 mcg/m²/day subcutaneously 1
• Can be used in combination with G-CSF: 7.5 mcg/kg each morning (G-CSF) and 7.5 mcg/kg each evening (GM-CSF) 1

Advanced Mobilization Strategy

G-CSF + Plerixafor Combination

For patients with poor mobilization potential:

• G-CSF 10 mcg/kg/day for 4 days, then
• Add plerixafor 240 mcg/kg/day subcutaneously (evening of day 4)
• Begin collection on day 5 1
• Plerixafor dose adjustments:
  • Reduce for GFR <50 mL/min
  • Maximum dose: 40 mg/day for maximum 4 days 1

Mobilization Protocols by Donor Type

Autologous Setting

1. Single-agent G-CSF:

   • 10-32 mcg/kg/day subcutaneously for 4-5 days 1
   • Begin collection on day 4 or 5

2. Chemomobilization + G-CSF:

   • Similar G-CSF doses after chemotherapy (e.g., cyclophosphamide, ICE, DHAP)
   • Start G-CSF approximately 24 hours after completing chemotherapy 1
   • Collection begins during count recovery

Allogeneic Donors

• G-CSF 10 mcg/kg/day subcutaneously
• Start collection on day 4 or 5 1
• Plerixafor use in normal donors is still under investigation 1

Clinical Considerations

Administration Schedule

• Twice-daily administration (5 mcg/kg twice daily) may be more effective than once-daily (10 mcg/kg once daily) for stem cell mobilization 2
• This approach yields higher CD34+ cell counts and requires fewer apheresis procedures without increasing toxicity 2

Safety Profile

• G-CSF administration to healthy donors is generally well-tolerated 3
• Common side effects include:
  • Moderate bone pain (88%)
  • Headache (72%)
  • Fatigue (48-60%)
  • Nausea (8%) 2

Collection Efficacy

• G-CSF is significantly more effective than GM-CSF alone for mobilizing CD34+ cells 4
• Combination of G-CSF and GM-CSF may enhance mobilization of certain stem cell subsets 4

Practical Recommendations

1. First-line agent: G-CSF (filgrastim) at 10 mcg/kg/day subcutaneously for 4-5 days
2. For poor mobilizers: Add plerixafor on evening of day 4
3. For optimal yield: Consider split dosing (5 mcg/kg twice daily) rather than once-daily dosing
4. Alternative: GM-CSF can be used but is less commonly utilized than G-CSF

Generic filgrastim appears comparable to innovator filgrastim for peripheral blood stem cell mobilization in both normal donors and patients undergoing autologous transplantation 5.