Summary/Abstract: Recombinant protein therapeutics (RPTs) have proven to be an effective method of treating a growing number of medical diseases/conditions. More than 100 approved RPT therapeutics now exist, with a potential market expected to surpass $550 B by 2030. Yet despite current success and robust growth, RPTs tend to be expensive to produce and difficult to administer. Underlying biology can fundamentally limit the clinical efficacy of a relevant recombinant protein delivered intravenously. Moreover, RPT design has typically been limited to the twenty canonical amino acids encoded by DNA/RNA triplets. Notably, evidence from the small-peptide field and from our own preliminary work has established that the substitution of specific amino acids with “unnatural” fluorinated analogs can increase thermodynamic stability of proteins above native levels. Thus, Halide Biologics was founded to leverage the potential of chemical biology to enhance the pharmacological properties of protein therapeutics and to capitalize upon the strong, NIH-funded initial work done by our co- founders at the University of Iowa and Oregon State University. During this Phase I SBIR project, our interdisciplinary team intends to establish proof of concept in applying targeted fluorination to the design and production of novel variants of injectable RPTs in the field of inborn errors of metabolism. Performance will be compared against relevant standard of care to determine whether targeted fluorination improves the stability of target proteins to an extent predictive of meaningful clinical improvement. In tandem, we will utilize cutting-edge techniques for stable integration to generate cell lines that enable production of fluorinated therapeutic proteins with at least a 3-fold improvement in cost efficiency over the existing transient system. Phase I SBIR success will lead to the identification of unique engineered therapeutic proteins bearing supra-physiological pharmacological properties. It will also serve as a foundation for a larger, follow-on Phase II SBIR project that includes in vivo safety and efficacy profiling. Phase II success will set the stage for a potential Phase IIB project and/or Phase III commercialization with major industry and/or financial partners. The ultimate commercial goal of these efforts is the licensing of our novel protein variant(s) to advance the treatment of a wide range of diseases. Success in the long term will address a major commercial market opportunity and will greatly benefit the human health and well-being of millions in the U.S. and internationally.