TNF Inhibitors for Crohn’s: So Much We Don’t Know

The next issue of The Medical Letter will include an article titled “TNF Inhibitors for Crohn’s Disease: When, Which, and for How Long”. That sounds as though we know a lot, and we do, but as with many drugs for many conditions, there is so much more we don’t know.

Crohn’s is a terrible disease, especially because it affects so many young people. We are lucky to have these wonderful drugs that can put patients who are suffering into corticosteroid-free remissions for months or years. But, as we point out in our article, they are expensive, and they can cause (or, more accurately, have been associated with) serious side effects like severe infections and malignancies. How likely is someone treated with one of these agents to develop tuberculosis or a lymphoma? We really don’t know.

The 3 TNF inhibitors currently available in the US are not just peas in one pod. They are all antibodies, but very different antibodies. One is partly mouse and partly human. Another is fully human. And the third is a fragment of a human antibody. Do these differences have any effect on the drugs’ efficacy or their side effects? We have no idea.

As is often the case with incontrovertibly useful, very expensive drugs, the last thing their manufacturers want to see happen is a comparative clinical trial that finds their bonanza less effective or more toxic than one of the competing agents. So they are unlikely to go out of their way to encourage such a trial, and if circumstances dictate that they must expose their sensitive baby to a trial against the rough-and-ready kids next door, they will sponsor it themselves, and single manufacturer-sponsored clinical trials almost always come out in favor of the sponsor’s product.

So we don’t know whether any one of the 3 TNF inhibitors is more effective for Crohn’s than any other. They all produce a response in a majority of patients being treated with one of these agents for the first time. And sometimes that response, freedom from the debilitating symptoms of the disease and the side effects of prednisone, can last for years. But how long do you continue a drug that seems to have produced a cure, but costs a fortune and carries huge, so far uncommon, risks? We don’t know that either, but we do our best to answer that question in our next issue. Take a look for yourself.

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  1. Dr. Gordon Yanchyshyn says:

    Thank you for your continued healthy skepticism of the limits of our medical knowledge and the motives for and results of clinical drug trials. I have been reading The Medical Letter since the mid-70’s and continue to value its non-partisan approach.

    Gordon Yanchyshyn, M.D., FRCPC
    Psychiatrist and Psychoanalyst
    Toronto, Ontario, Canada

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