SHMT-IN-4 (Compound 9ay) is a herbicide that targets and inhibits serine hydroxymethyltransferase ( SHMT1 ) with an IC 50 value of 193.8 g a.i./ha (active ingredient content per hectare). SHMT-IN-4 interferes with amino acid synthesis and metabolism in plants by binding to SHMT1 , thereby inhibiting plant growth. Additionally, SHMT-IN-4 shows no significant toxicity to maize and honeybees.