Plerixafor plus pegfilgrastim is a safe, effective mobilization regimen for poor or adequate mobilizers of hematopoietic stem and progenitor cells: a phase I clinical trial

The safety, kinetics and efficacy of plerixafor+pegfilgrastim for hematopoietic stem and progenitor cell (HSPC) mobilization are poorly understood. We treated 12 study patients (SP; lymphoma n =10 or myeloma n =2) with pegfilgrastim (6 mg SC stat D1) and plerixafor (0.24 mg/kg SC nocte from D3). Six SP were ‘predicted poor-mobilizers’ and six were ‘predicted adequate-mobilizers’. Peripheral blood (PB) CD34 + monitoring commenced on D3. Apheresis commenced on D4. Comparison was with 22 historical controls (HC; lymphoma n =18, myeloma n =4; poor mobilizers n =4), mobilized with pegfilgrastim alone. Eight (67%) SP had PB CD34 + count ⩽5 × 10 6 /L D3 post pegfilgrastim; all SP surpassed this threshold the morning after plerixafor. In SP, PBCD34 + counts peaked D4 6/12 (50%), remaining ⩾5 × 10 6 /L for 4 days in 8/12 (67%). All SP successfully yielded target cell numbers (⩾2 × 10 6 /kg) within four aphereses. After maximum four aphereses, median total CD34+ yield was higher in SP than HC; 8.0 (range 2.4–12.9) vs 4.8 (0.4–14.0) × 10 6 /kg ( P =0.04). Seven of twelve (58%) SP achieved target yield after one apheresis. Flow cytometry revealed no tumor cells in PB or apheresis product of SP. Plerixafor+pegfilgrastim was well tolerated with bone pain ( n =2), diarrhoea ( n =2) and facial paraesthesiae ( n =3). Plerixafor+pegfilgrastim is a simple, safe and effective HSPC mobilization regimen in myeloma and lymphoma, in both poor and good mobilizers, and is superior to pegfilgrastim alone.