So I think when we think about ankylosing spondylitis, that's been an issue for us for a long time, in terms of diagnosis and treatment. But in the last decade or so, it's become increasingly recognized that actually AS is only diagnosed when people have a lot of damage on the x-rays that can be identified. That's how it's classified. And so, patients will have had disease probably for 10 years or more, before they get to that point. So obviously, there's a need to pick up patients early, before they have the x-ray damage. And there's a need to treat them at that stage as well. Because they have active disease, even though they haven't got damage yet. So things have really changed in terms of the terminology that we use. So rather than using ankylosing spondylitis, we're now talking about axial spondyloarthritis, which is kind of a global term. And that can be radiographic.
So radiographic axSpA, which is essentially the same as AS. They have changes on the x-ray and damage there. And then nonradiographic axSpA, where they don't have damage on the x-ray yet. But it's identified based on clinical criteria and often MRI imaging as well, which can show the inflammation within the bone. And that's obviously crucial for patients. Because there's no point making a potential diagnosis, ignoring them for 10 years while they develop damage to their joints, and then treating them once they meet the criteria for ankylosing spondylitis. So we need to look at how we treat patients with nonradiographic axSpA once we've got a diagnosis, and treat them because they still have disease activity. Which is going to impact on their life day-to-day.
The COAST-X trial looked at ixekizumab versus placebo in patients with non-radiographic axSpA. So there's already been a study done in ankylosing spondylitis or radiographic axSpA. But there haven't been a study looking at these patients who don't yet have x-ray damage. So to be included in this study, they had to have axial spondyloarthritis according to the ASAS criteria. They had to not meet the radiographic modified New York criteria for AS. So we're excluding the ones who already have the damage. Because we've already tested that in another study. And they had to have either a CRP that was high or they had to have a positive MRI showing inflammation.
So that's really just to make sure that the diagnosis is sound and that they definitely have inflammation, evidenced either by the blood or the MRI results. So those patients were then randomized either to ixekizumab or to placebo. And perhaps unsurprisingly, because we know this works in the radiographic form of the disease, it worked very well. So there was a clear difference between drug and placebo for the primary outcome, which was ASAS40. And also for a number of secondary outcomes. So for other extra spinal manifestations, such as enthesitis, where they also saw an improvement. And I think the key things for clinicians to remember is obviously thinking about nonradiographic axSpA in terms of a diagnosis, and thinking about the treatment options available then. And this varies a lot in different health care settings.
Obviously, for a lot of the drugs that we have available in AS, the license is specifically in AS. Although a lot of people are treating patients who don't yet have the x-ray damage but have evidence of inflammation on MRI. But I think it's important that we have evidence to back that up. So we've seen a trial before from certolizumab an anti-TNF inhibitor. We've now got this study with ixekizumab, an IL-17 inhibitor, and another separate study with another IL-17 inhibitor-- secukinumab. So we're starting to see proof that the biologics work well, even in the nonradiographic axSpA patients. And that's important, because it gives us an evidence-based treatment to use to improve their symptoms, their quality of life, and to keep them living a normal life. Even before they've developed those X-ray changes.
So I think this data gives strong evidence for the use of ixekizumab. And I would expect that the company will apply for a label to be able to use that internationally. So that will give us access to that drug under similar inclusion criteria to the trial-- you would expect. So that gives us different options. That gives us treatment options like TNF inhibitors and IL-17 inhibitors. And so it gives us some different options to treat people.
There have been a couple of studies looking at drug withdrawal in this population as well. So when patients have become well; treated with a biologic in the nonradiographic axSpA, they then randomize people either to stay on the drug or to switch to a placebo later on to see if that's maintained. And, obviously, patients do stand a chance of flaring in those studies. But in some of those studies, it's been shown that the symptoms seem to settle down. And, actually, a proportion of patients will stay well. Even when the drug is stopped. So I think that would be a useful addition to think in the future, about whether we can treat early, and then withdraw the drug for some patients who do very well. And, obviously, we need to get better at that in order to treat people better.