Synlogic (SYBX) 8-K Regulation FD Disclosure

 Exhibit 99.1

   Synlogic   DESIGNED FOR LIFE  SYNB1618Phase1/2a Clinical Trial Topline Data from PKU Patient CohortsJuly 15th, 2019 

   SYNB1618 Potential to Address Unmet Need Across Patient Groups  360 mmol /L  Uncontrolled Adults  Partially Controlled Adults(Adults on Kuvanand/or low-Phe Diet)  Pediatric Patients (controlled / partially controlled) (Pediatric patients on Kuvan and / or low-Phe diet           Phe  Natural protein  Phe      Phe    Initial Focus 

 SYNB1618 Phase 1/2a Study Design  Single Ascending Dose (SAD)6 cohorts, N = 24  Multiple Ascending Dose (MAD)- TID x 7 days4 cohorts, N = 32    Dose ID  Single Dose (SD)N = 4  Multiple Dose (MD)TID x 7 daysN =10    Dose Confirm    MTD  Part 1: Healthy Volunteers  Part 2: PKU Patients  PKU Clinical Trial DesignRandomized, double-blind placebo-controlled study at multiple sites in the US Primary outcome: establish safety/tolerability following single and multiple doses in HV and PKU patients Secondary outcome: SYNB1618 kinetics in fecesExploratory: change from baseline in plasma and urinary biomarkers of Phe metabolism  Presented in September 2018  New Data 

 SYNB1618 Activity Biomarkers Indicate Significant Phe Consumption  Similar activity in HVs and PKU Patients     

 Modeling: Potential For Phe Reduction in PKU Patients   % Blood Phe lowering  7x1010 1x1011 3x1011 5x1011  125100755025          TPP >30%  SYNB1618 Dose (CFU)  8-18%  11-26%  34-79%  57-131%  Ranges representLow: PAL mechanism only (conservative) High: PAL + LAAD activity (estimates maximum with both pathways) 

 Upcoming Milestones and Path Forward  Established new solid formulation and manufacturing process Completed EPO1 interactions with FDA to align on program plans (clinical, manufacturing, toxicology) Completed Phase 1/2a study (healthy volunteers and PKU patients)Initiate bridging study with solid formulation in Q3 2019Phase 2 study in PKU patients to assess Phe lowering to start in 1H 2020                 

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