An American Society of Clinical Oncology (ASCO) meeting abstract describes initial results from an ongoing Phase 2 study of romidepsin combined with Velcade (bortezomib) for patients with relapsed or refractory myeloma.

Romidepsin is a histone deacetylase inhibitor (HDACi). An HDACi is a compound that disrupts the function of enzymes called histone deacetylases, which contribute to the spread of myeloma.

Laboratory studies have determined that HDACis such as romidepsin significantly reduce the growth of myeloma cells. Additionally, HDACis can enhance the toxic effect of Velcade on myeloma cells.

According to the abstract, romidepsin in particular has previously shown activity in patients with relapsed or refractory myeloma when administered as a four-hour infusion in combination with dexamethasone (Decadron) and Velcade.

The current Phase 2 study is evaluating the activity and safety of a one-hour infusion of romidepsin in combination with Velcade. Researchers also are evaluating the way the drug is absorbed, distributed, metabolized, and excreted by the body.

Patients participating in the study have received 10 mg/m² of romidepsin on days one, eight, and 15 of a 28-day cycle. They received 1.0 mg/m² of Velcade on days one, four, eight, and 11 of the same cycle. Researchers evaluated the drug’s effects on the body at the start of the one-hour infusion of romidepsin, as well as after 15 minutes, half hour, one hour, two hours, three hours, four hours, six hours and 24 hours.

So far, five patients have enrolled and taken part in the study. The five patients had a median age of 68, though ages ranged from 65 to 72.

Two patients who had relapsed from recent Velcade-containing treatments experienced minimal responses after two cycles of the combination romidepsin and Velcade regimen. Also, two patients experienced severe thrombocytopenia (low blood platelet counts).

The abstract concludes that the initial results suggest a one-hour romidepsin infusion combined with Velcade is an active treatment for myeloma patients who have replapsed or are refractory to Velcade.

The study continues to enroll patients. However, based on the cases of thrombocytopenia observed in the trial thus far, the romidepsin dose being used has been reduced to 8 mg/m².

For more information on the study, visit abstract e19508 at the 2009 ASCO meeting Web site.