Diet drug taranabant, Merck's competitor to the Sanofi-Aventis drug rimonabant (Acomplia / Zimulti), is now entering the final months of a two-year international study with 2,400 participants.

Anecdotal reports from participants in the Phase III trial of taranabant, otherwise known as MK-0364 or L-000899055, continue to be encouraging, and Merck has said it expects to file for approval to market the diet drug in the United States in spring 2008.

But there have been no presentations of interim results of the trial to scientific meetings and Merck has had little to say about taranabant.

Some suggest Merck has drawn some important conclusions about how-not-to-gratuitously-alienate-the-FDA from recent experiences of Sanofi, which trumpeted one exciting result after another from clinical trials of rimonabant only to find things moving slower and slower at the regulatory agency.

With millions of Americans eagerly anticipating approval of rimonabant, the FDA repeatedly delayed action, and Sanofi finally pulled back its application in June -- ending hopes of early approval -- after an FDA advisory panel recommended the diet drug not be marketed until safety issues are resolved.

Meanwhile, taranabant -- which started out several years behind rimonabant -- moves quietly through the clinical trial process. The Phase III trial, which began enrolling participants in fall 2005, will be drawing to an end in the final quarter of this year, with contracts for researchers ending in early 2008.

Final results from this trial, where participants were rerandomized for the second year in an effort to determine what dose is needed to keep off weight lost in the first, are not expected until spring, and there has been no hint Merck will bring interim news to the Obesity Society annual meeting in October.

At a preconference session on New Developments in Obesity Pharmacotherapy on Oct. 20th, researchers plan to report on Qnexa, Excalia, Contrave and Lorcaserin -- but no presentation has been scheduled on taranabant.

While Merck may yet decide to provide some information on interim trial results at any time, the approach on taranabant -- which may wind up being a more exciting diet aid than rimonabant -- has thus far been extremely low key.