A Manufacturer-Sponsored Comparative Trial

An article in the September 14 issue of The Lancet raises some interesting questions. Its title is: “Efficacy and safety of canagliflozin versus glimepiride in patients with type 2 diabetes inadequately controlled with metformin (CANTATA- SU): 52 week results from a randomized, double-blind, phase 3 non-inferiority trial.”

The choice of a second drug in patients with type 2 diabetes that has not responded to metformin is a burning question that The Medical Letter tried to address in its July 23, 2012 issue (“What Comes After Metformin for Type 2 Diabetes”). We concluded that a sulfonylurea (such as glimepiride) appears to offer the best combination of effectiveness, low cost and convenience, but weight gain and hypoglycemia can be problematic. Subsequently (May 13, 2013) we reviewed canagliflozin (Invokana) when it came out on the US market and concluded that it is modestly effective in reducing HbA1c, systolic blood pressure and weight, with a low risk of hypoglycemia, but can cause genital mycotic infections, and its long-term safety is unknown.

The question of which drug should follow metformin is enormously important, not only clinically, but also commercially. There are a lot of folks out there with type 2 diabetes. A 30-day supply of glimepiride costs $4. A 30-day supply of canagliflozin costs $263, and most insurance companies probably keep it in the tier you have to pay for out of pocket. So the manufacturer (Janssen) has quite a mountain to climb to convince people they should reach for the pricey new drug with no long-term safety data over the cheap and effective old one.

The one thing you can count on from a manufacturer-sponsored comparative trial is that the sponsor’s drug will come out on top. Not to accuse anybody of anything, but that is just a fact of life. This study was not only funded by Janssen, but it also included 4 Janssen employees among its 9 authors. You will not find articles with that kind of line-up in The Lancet or any other major medical journal coming out with a conclusion that the manufacturer’s drug turned out to be inferior. Still, just as effective as glimepiride, with no weight gain and no hypoglycemia? It sounds too good to be true.

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