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Source: Merck & Co.

It's been a busy month for diabetes trial data; especially data that could have a big impact on Merck & Co.'s (NYSE:MRK) top-selling type 2 diabetes drug Januvia.

Specifically, Merck released data showing that its once-weekly omarigliptin works similarly to once-daily Januvia and Eli Lilly (NYSE:LLY) reported its SGLT2 inhibitor Jardiance lowers the risk of heart attack and stroke.

Competing therapies
Eli Lilly's cardiovascular outcomes results have some thinking that Jardiance could put Merck's Januvia on the ropes. However, Merck's once-weekly omarigliptin could solidify Merck's position by reducing patient burden and boosting patient adherence, something that's critical to slowing diabetes progression.

In phase 3 trials, patients taking 25 mg of omarigliptin saw a similar improvement in their blood sugar levels from baseline as patients taking Januvia. The percentage of patients achieving their blood sugar target levels was about identical for both therapies, too: 51% of omarigliptin patients reached their A1C goal of less than 7%, compared to 49% of Januvia patients.

Omarigliptin's safety results were also similar, but omarigliptin may have an advantage tied to a slightly lower incidence rate of diarrhea, flu, and urinary tract infection.

However, omarigliptin's once-weekly dosing, solid efficacy, and similar safety doesn't mean that doctors will prefer it to Eli Lilly's Jardiance.

Jardiance's lowering of all-cause mortality by 32% makes it the first diabetes therapy that has been proven to lower the risk of death due to a major cardiovascular event and that's an important finding that will lead many doctors to prescribe it, especially in high-risk patients who are struggling to hit their blood glucose target.

But Jardiance's success doesn't necessarily have to come at Merck's expense.

Overwhelmingly, Januvia is already being prescribed as part of combination therapy, usually alongside metformin, and because Jardiance results were the same regardless of whether or not it was used with or without Januvia, there's little reason for doctors to discontinue Januvia if it's helping patients keep their blood sugar in check.

Instead, Jardiance could simply become one drug in a three drug strategy that also includes metformin and either Januvia or omarigliptin, if it gets FDA approval.

More options coming
If so, then Merck's unlikely to take much of a hit to its DPP-4 revenue stream, which as of the second quarter is running at annualized $6.4 billion clip.

The company could eventually build on that figure if its plans to develop combination therapies for type 2 diabetes patients pans out.

To compete with Jardiance, Merck is developing its own SGLT2 inhibitor, ertugliflozin. Merck is also conducting a late-stage trial evaluating whether patients using a combination of ertugliflozin and Januvia are able to better control their blood sugar levels. Data from those trials is expected next year and if the combination trial results are positive, then it could advance the notion that regimens including SGLT2's and DPP-4's are the future of treatment for patients whose blood sugar is no longer controlled by metformin alone.

Looking ahead
Investors are correct to believe that Eli Lilly's Jardiance could become a blockbuster drug, but I also believe it's too early to say that Merck's DPP-4 franchise is going to be left empty-handed.

If Merck's omarigliptin wins over regulators and its combination therapy study posts positive results, then Merck should be able to leverage its 70%-plus DPP-4 market share to pitch the advantages of its upcoming drugs, and for that reason, it may be a mistake to count Merck out of the race so soon.

Todd Campbell has no position in any stocks mentioned. Todd owns E.B. Capital Markets, LLC. E.B. Capital's clients may have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.