The studies, presented on Monday at the American Society of Hematology (ASH) meeting in New Orleans, tested carfilzomib given intravenously every 28 days in 73 patients who had not previously been treated with Takeda Pharmaceuticals’ (4502.T) Velcade, and in 33 others following treatment with Velcade.

“These interim results suggest that carfilzomib could benefit patients with multiple myeloma who are no longer responding to current therapies,” Dr. David Siegel, co-investigator of the studies, said in a statement.

Onyx acquired carfilzomib with its purchase last month of Proteolix Inc, saying the drug for multiple myeloma, a blood cancer, has the potential for accelerated U.S. approval in 2011.

Among those who had not received prior Velcade treatment, or Velcade naive patients, carfilzomib led to an overall response rate (ORR) of 46 percent among 54 patients at a 20 milligram dose, and a 53 percent overall response among 19 patients with dose escalation to 27 mg, researchers said.

Patients who were previously treated with Velcade, known chemically as bortezomib, achieved an overall response rate of 18 percent when administered carfilzomib, researchers said.

The Velcade naive patients had relapsed or worsened following other prior therapies.

“While we do not yet model carfilzomib revenue, we do think this agent has real potential for accelerated approval and to establish a meaningful position in the multiple myeloma market based on strong activity and promising side effect profile,” Robert W Baird analyst Chris Raymond said in a research note.

Multiple myeloma results from abnormal plasma cells, usually in the bone marrow. More than 180,000 people are living with the disease worldwide and about 86,000 new cases are diagnosed annually, Onyx said.

Median survival from relapsed and refractory multiple myeloma — when the disease returns and progresses following a response to therapy — can be as short as six to nine months.

In addition to overall response, the Proteolix-sponsored trials looked at secondary goals of time-to-progression and duration of response.

In the Velcade naive group time-to-progression, or the amount of time before the disease worsens, was 7.6 months, and duration of response was 8.4 months.

In the group previously treated with Velcade, interim results showed a time-to-progression of 5.3 months and duration of response of more than 9 months.

“These findings are truly an advance for patients with multiple myeloma,” Dr. Michael Wang, of the MD Anderson Cancer Center in Houston and one of the lead investigators, said.

Noting that other life-extending drugs often have adverse side effects, including severe nerve pain, Wang said “carfilzomib is showing good response rates with an improved side effects profile.”

Treatment with carfilzomib was well tolerated with no unexpected side effects, researchers said.

More than 20 percent of patients were able to complete the full 12 cycles (48 weeks) of therapy in both studies without cumulative side effects, and with low incidence of neuropathy, researchers said.

“These data support our ongoing carfilzomib program in multiple myeloma, a disease that has poor long-term survival,” Michael Kauffman, Onyx’s interim chief medical officer, said in a statement, adding that the company could file its application seeking U.S. approval by the end of 2010.

Onyx shares were off 18 cents or 0.6 percent at $29.59 on the Nasdaq at midday.

Histopathology Bone–Multiple myeloma