Two-stage phase II study of imatinib mesylate in subjects with refractory or relapsing neuroblastoma.

Background: Cure rate for subjects with refractory or relapsing metastatic neuroblastoma is <5%. In the search for a novel therapy, continuous daily oral administration of imatinib mesylate was evaluated.

Patients And Methods: Twenty-four subjects were enrolled in a two-stage study. Imatinib was administered for the first 4 weeks (cycle) at 170 mg/sqm b.i.d. If no major toxicity occurred, the dose was escalated to 300 mg/sqm b.i.d. for a maximum of 12 cycles. Clinical response and toxicity were evaluated according to international criteria. Pharmacokinetics (PK) profiles and tyrosine hydroxylase (TH) mRNA expression were also determined in a subset of subjects.

Results: Five (21%) complete responses, with one subject still alive at 68 months, and 2 (8%) partial responses lasting up to 29 months were obtained. No grade 4 toxicity was observed. At steady-state, PK exposure (69.7 µg h/ml) was similar to that of adults receiving 1000 mg/die. Responses appear to correlate with the absence or presence of metastasis in the bone marrow (BM) alone, with low TH expression levels at study entry and low imatinib exposure.

Conclusions: Imatinib mesylate was well-tolerated and effective in the subset of subjects with low BM infiltration as only site of metastasis. Study identifier EudraCT: 2005-005778-63.