(Adds U.S. expanded approval filing in 5th paragraph, updates shares in last paragraph)
By Bill Berkrot
Nov 21 (Reuters) - Johnson & Johnson's blockbuster multiple myeloma drug Darzalex when added to a standard therapy regimen reduced the risk of disease progression or death by 50 percent compared with standard therapy alone in patients not previously treated for the blood cancer, according to data released on Tuesday.
The data could lead to expanded approvals of the Darzalex combination as an initial, or first-line, therapy for multiple myeloma, providing a larger sales opportunity for the medicine, one of J&J's most important growth drivers.
Darzalex, a biotech drug known chemically as daratumumab, is already approved in combination with other medicines or alone in patients who had received one or more prior treatment regimens.
The drug had third-quarter sales of $317 million, with annual sales forecast to reach about $5 billion by 2021, according to Thomson Reuters data.
J&J has applied for expanded U.S and European approvals for the Darzalex combination to treat newly diagnosed patients, Genmab, which licensed the drug to J&J, said on Tuesday.
In the first-line study, 706 patients deemed not eligible for bone marrow transplants received either Darzalex with Takeda Pharmaceutical's Velcade, the chemotherapy melphalan and the steroid prednisone or the combination without Darzalex.
The trial was primarily conducted in Europe using the standard first-line regimen there. Celgene Corp's Revlimid is typically part of the standard U.S. regimen.
The median time until disease worsening, known as progression-free survival (PFS), was 18.1 months for the standard regimen, while fewer than half in the Darzalex group had experienced disease progression after two years of treatment, according to a summary of data to be presented at the American Society of Hematology (ASH) meeting in Atlanta next month.
The superior PFS with Darzalex was driven by more patients achieving greater responses, including a significantly higher number of complete responses, researchers concluded.
The overall response rate was 90.9 percent for the Darzalex group versus 73.9 percent for the control group.
Complete responses, meaning no detectable cancer in the blood or bone marrow, were reported in 42.6 percent of Darzalex patients versus 24.4 percent for the standard regimen.
Overall survival data was not yet available.
About 71 percent of Darzalex patients had what was deemed a very good partial response versus 49.7 percent for the other regimen.
There was a higher rate of serious infections in the Darzalex group - 23.1 percent vs 14.7 percent.
ASH President Dr. Kenneth Anderson called the results "impressive," but added they were likely to be viewed as more significant outside the United States.
J&J shares were up 0.5 percent at $138.60. (Reporting by Bill Berkrot; Editing by Andrew Hay and Jeffrey Benkoe)