peripheral neuropathy, a numbness and tingling in the fingers and toes that is a sign of nerve damage. Onyx, which obtained carfilzomib a year ago via the acquisition of South San Francisco-based Proteolix, is hoping to differentiate its product not just by helping patients who have run out of other options, but by offering a product with a more tolerable side effect profile.
Here’s what researchers are learning today about carfilzomib’s side effects. About 77 percent of patients had mild to moderate forms of peripheral neuropathy when they entered the study. New cases of this effect, or worsening of it was uncommon, researchers said. Less than 1 percent of patients reported a case of moderate to severe peripheral neuropathy on the Onyx drug. That’s good by cancer drug standards, but like many other anti-cancer compounds, this product is known to also knock out many types of blood cells. The most common moderate to severe side effects were thrombocytopenia, a depletion of clot-forming platelet cells (27 percent); anemia, a reduction in oxygen-carrying red blood cells (22 percent); and neutropenia, a lowering of infection-fighting white blood cells (10 percent).
Onyx has said it plans to seek FDA approval on the basis of this set of data by mid-2011, after it resolves some manufacturing issues that have held up its application by an estimated six months.
Millennium, of course, isn’t ready to back down. The company released some data yesterday at ASH from a study called MMY-3021, which suggested it was able to reduce the cases of peripheral neuropathy by developing a new formulation of bortezomib that can be injected just under the skin—a more convenient delivery route than the traditional intravenous infusion. Millennium said that 38 percent of patients experienced peripheral neuropathy after getting the subcutaneous bortezomib, compared with 53 percent who reported that effect with the intravenous form. Millennium, as I described in a feature story last week, is also seeking to figure out the best dosing schedule for maintenance therapy after patients have already had their tumors knocked down successfully in an early round of treatment.
Onyx is seeking over time to gain traction among myeloma patients with earlier stages of disease, but if it can win FDA approval, its initial market will be in a niche with patients who have essentially run out of other options. Even though myeloma is a relatively rare disease, it represents a big business opportunity. The worldwide market for myeloma drugs is worth an estimated $4 to $5 billion a year, Onyx has said. The Onyx drug could capture about $275 million in worldwide sales in 2014, according to forecast from analyst Christopher Raymond with Robert W. Baird, in a note to clients Nov. 4.
Despite Siegel’s enthusiasm, this drug doesn’t work for everybody. About one-third
