Eli Lilly has decided not to continue a collaboration with Japan’s Taisho Pharmaceutical for a candidate drug for diabetes, although Taisho has insisted it will press ahead with the compound’s development on its own.

The reasons for Lilly’s decision have not been made clear, other than to say that it was a result of non-clinical testing which did not satisfy its criteria for continuing the programme.

TS-021 is an oral dipeptidyl peptidase-IV (DPP-IV) inhibitor, in the same class as Merck & Co’s Januvia (sitagliptin), which could be on the market as early as later this year, and Novartis’ Galvus (vildagliptin) which is following a few months behind. Both GlaxoSmithKline and Bristol-Myers Squibb are also working on drugs in this class.

In 2005, Lilly signed an agreement with Taisho giving it worldwide rights to TS-021 – with the exception of Japan and China – with Taisho maintaining co-promotion rights in the USA and other designated countries. Taisho now says it will look for another co-promotion partner for the drug.