New evidence about the competition.
American College of Cardiology released some clinical data from the Phase III trials for their proposed competitor to acomplia (rimonabant). This new medication, still going by its generic name of taranabant, targets the same cannabinoid system as acomplia. It is therefore interesting to compare results since, if it gains regulatory approval, it will be a direct competitor to acomplia.
The randomised, double-blind and placebo-controlled trials recruited more than eight hundred participants who all had at least BMI 27. Merck & Co disclosed the preliminary results calculated at the end of year one of what is intended as a two year trial. In conjunction with a diet and exercises, 28% of those taking a 2mg dose of taranabant lost more than 10% of their body weight, while 57% lost 5% of their body weight. Almost 8% of those on placebo also lost 10% of their body weight through diet and exercise alone. In terms of averages, participants taking a 2mg dose of taranabant lost 14.5 pounds compared to 5.7 pounds on placebo. Depending on how you view these things, this could be viewed as a failure because Merck & Co announced in advance that it was aiming for a minimum 5% body weight loss in all participants taking their medication.
In 2004, Acomplia’s results were that 32% on Acomplia lost more than 10% of their body weight while 62.5% lost more than 5% of their body weight. But these results were obtained at the higher dosage of 20mg as opposed to 2mg taranabant. The reason of this difference in the dosage levels is that acomplia is a CB1 receptor antagonist that blocks endogenous cannabinoid binding to neuronal CB1 receptors, while taranabant acts as a selective cannabinoid-1 receptor inverse agonist, binding to CB1 receptors. I am glad we have got that clear.
Merck & Co tested higher doses of 4mg and 6mg but admitted problems with psychiatric side effects. It confirmed that taranabant would probably only be brought to the market at the lowest 2mg dose. Because the FDA has already expressed concern about similar side effects in acomplia, the Merck trials looked more specifically for evidence of the effects.
Nevertheless, this must be placed in a proper context. rimonabant has, of course, been available on prescription in Europe for two years and there is no emerging evidence of problems sufficiently serious to justify withdrawing approval. Indeed, it has just been given a further level of approval in the UK. As its effects are better understood, the reported side effects may be better controlled.