Isoxaflutole is a selective herbicide approved for control of certain broadleaf and grass weeds in field corn and soybean. Isoxaflutole is the first member of a new structural class of herbicides called the isoxazoles. Isoxaflutole works by preventing the biosynthesis of carotenoid pigmentsin both broadleaf and grass weeds. Without carotenoid pigments, chlorophyll pigments are damaged by the sun, and the plant eventually dies. Isoxaflutole is effective against weeds resistant to other herbicide classes such as glyphosate and atrazine. Isoxaflutole was registered conditionally from 1998 to 2004 for weed control in field corn. Isoxaflutole exhibited low acute toxicity via oral, dermal, and inhalation routes of exposure and it is not a dermal sensitizer. In long-term studies via the oral route, isoxaflutole caused ocular toxicity in rats, hepatotoxicity (including liver tumor formation) and thyroid tumors in rats and mice, and hematotoxicity (toxicity to blood) in dogs and mice at high doses. The liver and ocular toxicities observed in rats were consistent with the mode of action of isoxaflutole in mammals (i.e., inhibition of the hepatic enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD)) that leads to a buildup of tyrosine in the blood and the eye.

Topramezone is a pyrazolone herbicide developed by BASF, which is also an HPPD inhibitor, being effective for the control of weeds, which are resistant to glyphosate, triazines, ALS inhibitors and the ACCase inhibitors. Topramezone has a good control efficacy for corn grassy weed and broad-leaf grass worldwide. Topramezone was registered for the first time in Canada in 2006 for application to post-emergence weed removal in cornfield, followed by releases to Latin America, North America, Japan and Germany. In 2009, BASF brought to the Chinese market its Topramezone with the trade name Arietta®. Topramezone is moderately toxic to birds, honey bees, earthworms, fish and aquatic invertebrates. Topramezone strongly inhibited 4-HPPD activity in vitro, with I(50) values of 15 and 23 nM for the enzyme isolated from S. faberi and recombinant enzyme of Arabidopsis thaliana L. respectively.