Non Technical Summary: Current estimates indicate that one-third of worldwide agricultural output is lost to pests and diseases such as pathogenic fungi. Despite advancements in chemical control, the rapid onset of resistance to pesticides often limits their utility. In addition, the vast majority of pesticide research projects are terminated before commercialization because of unattractive attributes of the lead chemical series, such as toxicity or high cost of manufacturing, which cannot be engineered out of the molecule. It is therefore desirable to identify alternate chemical scaffolds that retain efficacy against the pathogen by the desired mode of action while improving other characteristics. Divergence has successfully employed this `lead-hopping' strategy by acquiring a breakthrough technology that allows rapid and accurate comparisons of compounds based on crucial similarities in shape and electrostatics at the molecular surface, where target interactions occur. Divergence's expertise in agrochemical discovery and assay systems coupled with this fundamental advance in cheminformatics has allowed the creation of HarvestTM, a powerful platform for novel agrochemical discovery. Harvest has already resulted in the development of promising nematicides, and two pilot projects modeling fungicides have identified compounds effective against pathogenic fungi both in vitro and in greenhouse assays. Several hits from one screen also inhibit the intended molecular target in biochemical assays, providing further validation to this approach. Based on these data, we are expanding this platform to broad-spectrum and potent fungicide candidates that were never commercialized (e.g., because of prohibitive manufacturing costs). Candidates are prioritized when they possess a novel mode of action, which is highly valuable for control of fungicide resistance within integrated pest management programs. Based on a computational search of over four million structures for one lead candidate, Divergence will acquire ~300 molecules that (1) best match the cheminformatic model and (2) harbor properties indicative of successful agrochemicals. These compounds will be evaluated in the laboratory for activity against two fungal pathogens as well as biochemical inhibition of the target enzyme. Hits will be progressed into greenhouse studies. It is anticipated that 3-5 lead candidates will result from these screens, facilitating further model refinements and the acquisition/synthesis of more efficacious analogs for each scaffold. During Phase II, leads will progress into spectrum testing against additional fungal species and preliminary toxicology testing before the prioritization of one lead series for analog synthesis and eventual progression into field trials. A safe and efficacious fungicide with a novel mode of action will be highly beneficial to commercial partners, agricultural producers, consumers, and the environment. OBJECTIVES: Goals/Objectives/Outputs: The goal of this Phase I SBIR project is to validate the soraphen A field model and to identify in vitro hits and greenhouse leads with confirmed mode of action using Harvest. Based on previous success and experience using this platform in the advancement of nematicides as well as fungicides, we are confident that promising novel fungicidal compounds that interact with the soraphen A target will be discovered during Phase I and will progress for lead development during Phase II. Specifically, we plan to complete the Aims described below. Aim I-In order to validate the molecular field model generated for soraphen A, we will acquire and evaluate compounds selected from the FieldPrints database. The compounds will be ranked and approximately 300 compounds will be acquired based on a number of factors, including 2-D diversity, absence of toxicophores, and desired physicochemical properties. Aim II-Using the compounds from Aim I, we will perform efficacy studies against Botrytis and Alternaria in vitro. We will also evaluate the compounds for interaction with the fungal acetyl-CoA carboxylase target of soraphen A using fluorescence spectroscopy and native gel shift assays. Based on results from previous screens, it is expected that over 10% of the compounds will be active in at least one of the screens. Aim III-Compounds that are effective in the bioassays and interact with fungal ACCase during Aim II will be given priority in the advanced greenhouse screen against Spaerotheca fuliginea (powdery mildew). Based on previous screens, we anticipate that 3-5 compounds will demonstrate activity in the greenhouse within 10-fold of commercial standards (spray solution at 0.02-0.2% AI). It is likely that further field model refinement and acquisition of analogs will be performed while moving into advanced Phase II studies. APPROACH: Methods: During Phase I, we will select and acquire ~300 compounds that closely match the soraphen A field pattern (Aim I), test these compounds in vitro against two phytopathogenic fungal species (Aim II), and confirm that the MOA of soraphen A is shared by these compounds (Aim III). Hits that meet both the efficacy and MOA criteria will be prioritized for greenhouse studies against a third fungal pathogen. Based on previous experience, this process may be iterative, with cheminformatic models adjusted to fit the field patterns of active compounds and subsequent acquisition of analogs to confirm hypotheses (Figure 6). Domestic benefits from the introduction of improved fungicides with novel MOAs would include improved yields for growers that may total several billion dollars and can also diminish the environmental footprint of agriculture and improve food security. Based on industry precedents, the cost/benefit ratio for a successful class of fungicides is outstanding from a commercial perspective as well as to society
