Reversal of drug-resistance in multiple myeloma with verapamil.

In vitro testing with a new doxorubicin resistant myeloma cell line revealed the reversal of drug resistance with as little as 100 ng/ml of verapamil (a calcium channel blocker), a dose easily achievable in humans. A first patient with IgG kappa myeloma is presented in whom resistance to VAD (vincristine/doxorubicin infusion plus dexamethasone) chemotherapy was reversed with the administration of verapamil. A subsequent clinical study has been initiated. The potential for further evaluation of calcium channel blockers in multiple myeloma is discussed.