Onyx Pharmaceuticals' saw its shares close up nearly 12% Friday after US regulators granted its jab Kyprolis a speedy approval for the treatment of the blood cancer multiple myeloma.

Specifically, the US Food and Drug Administration gave the thumbs up for Kyprolis (carfilzomib) to treat patients with multiple myeloma whose disease has progressed despite having had at least two prior therapies, including bortezomib and an immunomodulatory agent.

The accelerated approval - which allows regulators to OK a drug to treat a serious disease based on clinical data showing that it has an effect on a surrogate endpoint that is likely to predict a clinical benefit - came on the back of data from a Phase IIb 003-A1 study, in which the overall response rate to the drug was found to be 22.9% and median response duration was 7.8 months.

On the down side, there are some pretty hefty adverse reactions possible from taking the drug, including heart failure and shortness of breath, and patients "should be monitored closely and treatment withheld" should these occur, FDA officials said.

The most common side effects observed - in more than 30% of patients taking part in the study - were fatigue, low blood cell count and blood platelet levels, shortness of breath, diarrohea, and fever. 

Nevertheless, regulators judged that the treatment's benefits would likely outweigh the risks despite the absence of a full set of clinical trial data. Onyx said that enrollment in a Phase III confirmatory clinical trial, known as ASPIRE, is now complete.

New treatment option

"This approval provides a new treatment option for the significant unmet need that exists in patients with multiple myeloma who have progressed after use of available treatments," said David Siegel, Chief of the Division of Multiple Myeloma at John Theurer Cancer Center at Hackensack University Medical Center, welcoming the decision.

"The single-agent activity of Kyprolis provides clinicians the opportunity to help these patients who until now had no effective options," he added.

Annual sales of the drug could hit $682.7 million in 2016, according to the average of six analysts’ estimates compiled by Bloomberg, which would add significant ballast to the the firm's yearly revenues, which came in at $447 million in 2011.