(Reuters) - An experimental biotech drug being developed by Johnson & Johnson may offer hope to multiple myeloma patients who have run out of options, according to data from a midstage study released at a cancer meeting on Saturday.

J&J plans to use the Phase II study to seek U.S. and European approval of its antibody daratumumab to treat the blood cancer. The drug received breakthrough designation from the U.S. Food and Drug Administration, which can help speed the approval process.

Nearly 30 percent of 106 patients responded to daratumumab, including 3 complete responses, meaning no sign of cancer. Another 10 patients had a very good partial response defined as 90 percent reduction of myeloma protein in the blood or urine, while 18 had a partial response, researchers reported.

"To have complete remission speaks to the power of an immune-based approach," said Dr. Sagar Lonial, the study's lead investigator from Emory University in Atlanta. Lonial presented the data at the American Society of Clinical Oncology meeting in Chicago.

Daratumumab directly targets myeloma cells and enlists components of the immune system to attack the cancer.

Lonial said this was the first antibody drug that demonstrated effectiveness against myeloma without having to be combined with other medicines.

While median overall survival had not yet been reached, researchers estimated 65 percent of patients would still be alive after one year. "These are people you'd expect to be living less than six months," Lonial said.

Patients in the trial on average had undergone five prior treatments. They had become resistant, or failed to respond, to Takeda's Velcade and Celgene's Revlimid, the most widely-used myeloma medicines, as well as newer drugs Kyprolis from Amgen and Celgene's Pomalyst.

Responses lasted 7.4 months on average, and the median time to disease progression was 3.7 months, researchers reported.

The drug, for which J&J licensed worldwide rights from Danish drugmaker Genmab, is also being tested in combination with other multiple myeloma treatments to further improve patient outcomes.

The most common side effects were skin reactions at the infusion site, typically with the first or second dosing, which is quite common with such medicines.

An estimated 26,850 Americans are expected to be diagnosed with multiple myeloma in 2015. All patients eventually become resistant to therapy.

 

(Reporting by Bill Berkrot; Editing by Diane Craft)