What would be the reason why DPP-4 competition is so fierce?

Handok has announced the launch of ‘Tenelia(generic name: teneligliptin),’ the 7^th DPP-4 inhibitor. Its insurance price was selected as the lowest among other DPP-4 inhibitors with KRW 739. As JW Pharmaceutical acquired sales approval for the 8^th DPP-4 inhibitor, ‘Gadret(generic name: anagliptin),’ last May and is now about to launch the product, the domestic market will be an arena for 8 DPP-4...