Humira is without a doubt the most important drug for AbbVie (NYSE: ABBV ) . In the first quarter, sales of Humira were $2.2 billion, making up more than half of total sales.
Expanding the drug into axial spondyloarthritis? Not so much.
Shares hardly moved yesterday after a Food and Drug Administration advisory committee shot down the idea of expanding Humira's use. The panel voted 12 to 1 recommending against approving the drug to treat axial spondyloarthritis.
Humira is already approved to treat rheumatoid arthritis, plaque psoriasis, Crohn's disease, ulcerative colitis, ankylosing spondylitis, psoriatic arthritis, and juvenile idiopathic arthritis.
Axial spondyloarthritis is a precursor to ankylosing spondylitis, which all four TNF inhibitors -- Amgen (NASDAQ: AMGN ) and Pfizer's (NYSE: PFE ) Enbrel, Johnson & Johnson's (NYSE: JNJ ) Remicade and Simponi, and AbbVie's Humira -- are all approved for. But none of them are approved for axial spondyloarthritis, and it doesn't look like Humira will get the nod on this go with the FDA.
The agency has the final say, but the briefing documents for the committee members released last week posed similar questions about the trial design, so it seems unlikely the FDA would go against its panel of outside experts.
Axial spondyloarthritis is in the eye of the beholder
The FDA's and the panel's issue is that characterizing patients with axial spondyloarthritis isn't easy. The main symptom of axial spondyloarthritis is back pain caused by inflammation, but it isn't severe enough to show up on an X-ray. Ankylosing spondylitis, by contrast, is characterized by spinal fusion.
Back pain could, of course, be caused by a lot of other issues other than inflammation, but the FDA doesn't want patients exposed to potentially dangerous side effects if they won't benefit from the drug. Humira -- and the rest of the TNF inhibitors -- reduce the inflammation by inhibiting the immune system, which can lead to infections
AbbVie tried to ensure that the back pain was due to inflammation by defining the treatment group as those with objective signs of inflammation by elevated c-reactive protein or magnetic resonance imaging. But the patients couldn't have progressed far enough that they were considered to have ankylosing spondylitis. To separate those out, pelvis X-rays were performed.
Unfortunately these X-rays are apparently subjective. There were 38 patients -- out of 102 -- who entered into the study because the local investigators said their pelvis X-rays were negative who were then reclassified as having ankylosing spondylitis by the central reviewer. Considering what radiologists can miss on an X-ray, it's not surprising that they might have a differing opinion of disease progression.
Having that many patients with ankylosing spondylitis in the trial makes it somewhat useless, especially since Humira is already approved to treat ankylosing spondylitis.
AbbVie or one of the other drugmakers with a TNF inhibitor could try to run another trial with more controls for those enrolled in the clinical trial -- but the tighter the definition, the smaller the potential treatment group once the drug is approved. They might have a better return on their investment expending energy on finding patients in the already-approved indications.
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