Takeda Pharmaceutical Co has suffered a blow with the news that regulators in the USA want the firm to carry out additional studies on its investigational type 2 diabetes drug alogliptin.

The Japanese drugmaker has received a complete response letter from the US Food and Drug Administration for alogliptin, which is also known as SY-322 and is a selective dipeptidyl peptidase IV (DPP-4) inhibitor. The rejection is no great surprise seeing as how in March, the agency noted that although the New Drug Application for the drug was filed prior to fresh guidelines laid out in December, it does not believe that “the amount of existing alogliptin clinical data is sufficient to meet certain statistical requirements outlined in that new guidance”.

In recent months, the FDA and Takeda have been in discussions about conducting an additional cardiovascular study for alogliptin that would satisfy that guidance. Such a trial is likely to last at least two years and analysts believe that there is little chance of the drug hitting the US market before 2013.

Receipt of the letter from the FDA comes a month after Takeda said that alogliptin will not be filed in Europe until 2012. This is because the company has initiated an additional long-term study to evaluate the drug compared to glipizide when used in combination with metformin in 2,500 subjects with type 2 diabetes, whose blood sugar level is inadequately controlled with the latter.

Once the results are known, Takeda expects to have “a more robust data set necessary to ensure its approval” in Europe. That trial in Europe is separate to the additional one planned for the USA.

This is all bad news for Takeda as alogliptin is vital to its future success as the company prepares for life after its diabetes blockbuster Actos (pioglitazone), which loses patent protection in the USA in 2011. Also the delay means that alogliptin will have to make up huge ground on Merck & Co's DPP-4 inhibitor Januvia (sitagliptin), which is well-established on the market.