Promising late-stage data from two rival drugs to Merck & Co’s big-selling dipeptidyl peptidase-4 inhibitor Januvia have been presented at the American Diabetes Association meeting in San Francisco.

First up were five Phase III studies of Takeda Pharmaceutical Co’s DPP-4 inhibitor SYR-322 (alogliptin) involving more than 2,000 patients. They revealed that the drug, given once daily as a monotherapy, demonstrated statistically significant reductions in haemoglobin A1c (less than or equal to 7%) versus placebo.

Similar results were seen in the add-on to metformin, thiazolidinedione and sulfonylurea studies and across all studies, patients achieved significant reductions in HbA1c, up to 0.80%. The data show that alogliptin “effectively reduces blood sugar in patients, alone or when used in combination with existing oral anti-diabetic treatments as well as insulin, increasing the range of treatment options for patients'', said Richard Pratley, director of the Diabetes & Metabolism Translational Medicine Unit at the University of Vermont.

Alogliptin is key to Takeda’s future prospects as it prepares for life after its anti-diabetes blockbuster Actos (pioglitazone) which loses patent protection in the USA in 2011. Sales of the drug for the year ended March 2008 climbed 17.8% to 396.2 billion yen, or around $3.8 billion. Alogliptin was filed with the US Food and Drug Administration in January.

After Takeda’s presentations, AstraZeneca and Bristol-Myers Squibb touted the virtues of their DPP-4 inhibitor Onglyza (saxagliptin). A Phase III study involving 401 treatment-naive patients with type 2 diabetes and A1C levels between 7%-10% were randomised to receive one of three doses of Onglyza, or placebo, once daily.

The data showed that after 24 weeks of treatment, those who received either the 2.5mg or 5mg dose of saxagliptin saw a placebo-adjusted reduction of 0.6% in their A1C level, while those on 10mg had a reduction of 0.7%. The firms added that 41% on the latter dose achieved the ADA's recommended A1C level of less than 7%.

Observers are still unsure the data the firms are putting forward will be enough to get the approval of the US Food and Drug Administration and then make a dent in Merck’s sales for Januvia (sitagliptin). First-quarter revenues reached $272 million. Furthermore, at the ADA meeting, Merck presented new data from a 587-patient study demonstrating that combination therapy with Januvia and metformin substantially improved markers of beta cell function and significantly reduced blood sugar levels at both one and two years.