PROJECT SUMMARY Antimicrobial resistance increasingly threatens our ability to effectively treat a wide range of infections. Absent the development of novel antibiotics, humanity faces the prospect of a return to the pre-antibiotic era with associated mortality to rival that of cancer. One promising approach for the development of novel antibiotics is the engineering of antimicrobial peptides (AMPs), miniproteins of diverse structural classes made by all branches of life to defend against microbes. In particular, the engineering of human AMPs presents the opportunity to leverage both the antimicrobial and immunomodulatory properties of these AMPs to treat infections. Under the guidance of mentors at the Massachusetts Institute of Technology (MIT), Massachusetts General Hospital (MGH), and the Broad Institute, the candidate has adapted fast flow chemistry for the rapid synthesis and engineering of human AMPs, and in this proposal he seeks to extend these efforts through two aims. Aim 1 defines the structure-activity relationships underlying the mechanisms of gram-negative killing and phagocyte chemotaxis mediated by three human AMPs of distinct structural types, while Aim 2 extends these lines of inquiry to the development of derivatives of LL-37 as lead therapeutics. Together, these aims lay the groundwork for extension of the studies described to additional facets of AMP biology and engineering as well as preclinical applications as the candidate transitions to independence. The candidate’s research background consists of doctoral training in innate immunology against retroviral infection combined with clinical training in infectious diseases. This proposal for a K08 Mentored Clinical Scientist Research Career Development Award will enable the candidate to complete additional hands-on and didactic training in protein engineering and omics technologies over a five-year period toward the goal of establishing an independent, R01-funded research program applying these approaches to the ongoing study and development of human AMPs as novel antibiotics. In this effort, he is guided by primary mentors with expertise in protein engineering and mass spectrometry as well as bacterial pathogenesis and genomic technologies, which is further supported by an advisory board with deep expertise in microbiology, immunology, proteomics, AMP mechanisms of action, and drug development as well as the extensive resources of MIT, MGH, and the Broad Institute.