Researchers from the Mayo Clinic today reported positive results of a Phase 2 clinical trial combining Actimid (pomalidomide) with low-dose dexamethasone (pom-dex) in relapsed or refractory multiple myeloma patients. The results were presented earlier today at the 50th annual meeting of the American Society of Hematology (ASH).

Actimid, also known as pomalidomide or CC-4047, is a molecular relative of the commonly used myeloma treatment thalidomide (Thalomid). Like thalidomide, Actimid is an immunomodulatory agent, meaning that it has the ability to alter or regulate the body's immune response. Both drugs seem to work by various methods, such as stopping the growth of new blood vessels to tumor cells and inhibiting the growth of myeloma cells.

The pom-dex study, involving 37 patients across the United States, found that 62 percent achieved a measurable response to therapy, and another 6 percent achieved stable disease. The 62 percent overall measurable response included 24 percent with a very good partial response and 38 percent with a partial response. Importantly, a measurable response rate of 29 percent was observed in patients who were refractory to Revlimid (lenalidomide), another analog of thalidomide commonly used to treat multiple myeloma.

The results of the pom-dex clinical trial are promising compared to the presently used thalidomide-dexamethasone (thal-dex) combination for those with relapsed or refractory myeloma.

For example, a 2004 study by Palumbo et al involving 90 relapsed and refractory patients showed that the overall measurable response rate for the thal-dex combination was 47 percent, including 19 percent with near complete response and 28 percent with partial response. This is 15 percent lower than the 62 percent overall measurable response rate reported today for the pom-dex regimen.

At the same time, the thal-dex combination resulted in 35 percent of the treated patients maintaining stable disease. Only six percent of the pom-dex patients achieved stable disease.

A common side effect of the presently used thal-dex combination is grade 3 neutropenia, leading to dose limitations in many patients. The same side effect was observed for 31 percent of patients in the pom-dex trial, though the researchers claim toxicity was mild and the treatment was well tolerated overall. Neutropenia is a disorder characterized by lower-than-normal levels of neutrophils, which are white blood cells that defend the body against life-threatening bacterial infections.

Another study also presented at ASH today, however, sheds new light on how thalidomide and its analogs cause neutropenia. Based on their findings, the study authors suggest that thalidomide-related neutropenia may be treatable using granulocyte-colony stimulating factor (G-CSF) (Neulasta/Neupogen). G-CSF works to stimulate the survival, differentiation, and growth of neutrophils and neutrophil precursors and can be effective in many neutropenia cases.

For more information, see abstracts 866 (pom-dex combination) and 845 (neutropenia & G-CSF) at the ASH meeting website.