Slow desensitization of imatinib-induced nonimmediate reactions and dynamic changes of drug-specific CD4+CD25+CD134+ lymphocytes.

BACKGROUND

Imatinib is a tyrosine kinase inhibitor indicated for the treatment of gastrointestinal stromal tumors (GISTs) and certain neoplastic diseases; however, nonimmediate adverse reactions are common.

OBJECTIVE

To describe the process of imatinib slow desensitization in patients who experienced nonimmediate reactions to imatinib and the dynamic change in drug-specific CD4+CD25+CD134+ T-lymphocyte percentages.

METHODS

Five patients diagnosed as having GISTs and with a recent history of imatinib-induced nonimmediate reactions (maculopapular exanthema with eosinophilia, exfoliative dermatitis, palmar-plantar erythrodysesthesia, and drug rash with eosinophilia and systemic symptoms) were desensitized using a slow desensitization protocol. The reintroduced imatinib dosage was stepped up every week starting from 10 mg/d and increasing to 25, 50, 75, 100, 150, 200, and 300 mg/d until the target dose of 400 mg/d was achieved. Prednisolone of up to 30 mg/d was allowed if allergic reactions recurred. The percentages of CD4+CD25+CD134+ T cells present after incubating peripheral blood mononuclear cells with imatinib, at baseline and after successful desensitization, were analyzed using flow cytometric analysis.

RESULTS

By using a slow desensitization technique, all patients were able to receive 400 mg/d of imatinib, and prednisolone was gradually tapered off. The percentages of imatinib-induced CD4+CD25+CD134+ T cells decreased from a mean (SD) of 11.3% (6.5%) and 13.4% (7.3%) at baseline to 3.2% (0.7%) and 3.0% (1.1%) after successful desensitization, when stimulating peripheral blood mononuclear cells with 1 and 2 μM of imatinib, respectively.

CONCLUSION

Slow desensitization is a helpful procedure in treating patients with imatinib-induced nonimmediate reactions other than simple maculopapular exanthema. The reduced percentages of imatinib-induced CD4+CD25+CD134+ T cells in these patients may be associated with immune tolerance.