Novel AHAS-inhibiting sulfonylurea herbicides to control resistant weed species

Overview

Weed resistance to sulfonylurea herbicides is a growing global agricultural challenge caused by overuse of existing compounds. This research program applies structure-based drug design to acetohydroxyacid synthase (AHAS), the same enzyme targeted by commercial sulfonylureas, to identify new binding interactions that remain effective against resistant AHAS mutants. A series of novel sulfonylurea analogs has been chemically synthesized, and several lead compounds display strong inhibition of the P197L mutant AHAS, one of the most common resistance-conferring mutations. The goal is to deliver new herbicide candidates capable of controlling resistant weed species such as barnyard grass and crabgrass while maintaining acceptable crop safety.

Technical specifications

• Target enzyme: Plant acetohydroxyacid synthase (AHAS), including the wild-type enzyme and the resistance-associated P197L mutant
• Chemical class: Novel sulfonylurea analogs designed using crystal-structure analysis of the AHAS binding pocket to engage previously unexplored interaction sites
• In vitro performance: Selected compounds show potent inhibition of both wild-type AHAS and the P197L mutant, with a markedly improved selectivity index (as low as 2.78) compared with the commercial benchmark chlorimuron ethyl (26.60), indicating stronger activity against the resistant mutant
• Design strategy: Iterative medicinal chemistry guided by structure-activity relationship analysis and planned binding-mode studies with plant AHAS
• Planned validation: Expanded compound synthesis, in vitro assays against wild-type and P197L AHAS, greenhouse pot assays on susceptible and resistant barnyard grass and crabgrass, and crop-safety evaluation of lead candidates

Technology readiness level

The program is currently at an early-to-mid research stage. The design hypothesis has been validated through the first round of synthesis and in vitro AHAS inhibition assays, confirming that the new sulfonylureas inhibit the P197L resistance mutant more effectively than chlorimuron ethyl. Remaining work includes broadening the compound library, conducting greenhouse-level herbicidal activity tests on resistant weed species, refining structure-activity relationships, completing binding-mode analysis with plant AHAS, and assessing crop safety of lead candidates before any field or commercial development can be considered.