Pesticide
Development of new pesticides

The aim is to find new compounds or agents with improved properties such as a new mode of action or lower application rate. Another aim is to replace older pesticides which have been banned for reasons of toxicity or environmental harm or have become less effective due to development of resistance.

The process starts with testing (screening) against target organisms such as insects, fungi or plants. Inputs are typically random compounds, natural products, compounds designed to disrupt a biochemical target, compounds described in patents or literature, or biocontro l organisms.

Compounds that are active in the screening process, known as hits or leads, cannot be used as pesticides, except for biocontrol organisms and some potent natural products. These lead compounds need to be optimised by a series of cycles of synthesis and testing of analogs. For approval by regulatory authorities for use as pesticides, the optimized compounds must meet several requirements. In addition to being potent (low application rate), they must show low toxicity, low environmental impact, and viable manufacturing cost. The cost of developing a pesticide in 2022 was estimated to be 350 million US dollars. It has become more difficult to find new pesticides. More than 100 new active ingredients were introduced in the 2000s and less than 40 in the 2010s. Biopesticides are cheaper to develop, since the authorities require less toxicological and environmental study. Since 2000 the rate of new biological product introduction has frequently exceeded that of conventional products.

More than 25% of existing chemical pesticides contain one or more chiral centres (stereogenic centres). Newer pesticides with lower application rates tend to have more complex structures, and thus more often contain chiral centres. In cases when most or all of the pesticidal activity in a new compound is found in one enantiomer (the eutomer), the registration and use of the compound as this single enantiomer is preferred. This reduces the total application rate and avoids the tedious environmental testing required when registering a racemate. However if a viable enantioselective manufacturing route cannot be found, then the racemate is registered and used.

Insecticides with systemic activity against sucking pests, which are safe to pollinators, are sought after, particularly in view of the partial bans on neonicotinoids. Revised 2023 guidance by registration authorities describes the bee testing that is required for new insecticides to be approved for commercial use.
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