(566h) A Synthetic Probiotic Engineered to Treat Phenylketonuria

Phenylketonuria (PKU) patients are unable to properly metabolize the amino acid phenylalanine (Phe), leading to neurotoxicity. Currently, few broadly-useful treatment options exist. To address this unmet need, we constructed a synthetic probiotic strain of the Escherichia coli Nissle, designated SYN-PKU. SYN-PKU is engineered to express Phe degradative genes that are transcriptionally activated in the anoxic conditions of the mammalian gut. In phenylketonuric mice, SYN-PKU catalyzed a significant decrease in blood Phe levels independent of dietary protein intake, suggesting active recirculation of systemic Phe to the intestinal tract. Phe enterorecirculation was also demonstrated for the first time in healthy non-human primates (NHPs), and recirculating Phe was converted by SYN-PKU to trans-cinnamate, which was hepatically metabolized to hippurate and excreted in the urine, allowing its use as a quantitative biomarker of probiotic activity. Importantly, SYN-PKU also inhibited serum Phe elevation in NHPs following an oral Phe dietary challenge. This work supports synthetic probiotics as a novel class of therapeutics for treating rare genetic metabolic disorders and defines a strategy for their progression.