Alternate Day Dosing of Pomalidomide in Patients With Refractory Multiple Myeloma. A Multi-center, Single Arm Phase II Trial

Multiple myeloma (MM) accounts for 1% of all cancers and ∼10% of all hematological malignancies. Despite recent advances in myeloma treatment, including the introduction of proteasome inhibitors, immunomodulatory drugs (IMiDs) and stem cell transplantation, myeloma remains an incurable disease. The treatment of bortezomib and lenalidomide refractory myeloma is still an unmet medical need. Once patients have relapsed after IMiD-containing therapies and have become bortezomib-resistant, their prognosis is extremely poor.

Pomalidomide is a third-generation, Swissmedic approved, oral immunomodulatory drug with activity in such patients. However the toxicity of pomalidomide in the pivotal MM-003 trial was considerable, with 60% of patients experiencing drug-related G3/4 toxicity. Neutropenia (48% vs 16%) and pneumonia (13% vs 8%) were significantly more common in the pomalidomide arm. This resulted in frequent dose interruptions (67%) and dose reductions (27%). This suggests that for the majority of patients the 4 mg daily dosing schedule (4 mg daily on 21 of 28 days) is toxic, and that strategies to deliver reduced dosing of pomalidomide are of high practical relevance.

Alternative dosing schedules:

There is robust data available indicating that lower pomalidomide doses (e.g. 2 mg daily) lead to similar responses and progression free survival with fewer side effects. Due to its unique pharmacological characteristics, pomalidomide is well suited for alternate day dosing. The decline of the plasma concentration at the terminal phase is slow. These data make pomalidomide an ideal candidate for alternate day dosing. Therefore, a phase I study has already been conducted in 2008 to test the alternating administration of the drug showing excellent responses with a marked reduction of thrombotic events and less severe myelosuppression.

The drug costs of pomalidomide are quite high. Interestingly, the manufacturer determined a pricing model that is independent from the capsule strength (costs for one capsule 1 mg=2 mg=3 mg=4 mg). In patients requiring dose reductions due to hematologic toxicity, daily dosing of reduced strength pomalidomide (e.g. 2 mg daily) is approved and suggested by the manufacturer. This delivers 50% less pomalidomide to the patient, albeit at 100% of the price of full dosing.