Aeglea BioTherapeutics Investor Presentation Deck

Expected Phase 1 interim PK data informs dose and schedule modeling for target maintenance profile 1 SPY001 VEDO SPY001 HUMAN HALF-LIFE PREDICTIONS Half-life (days) Humans NHPs Humans NHPs 10 SPYRE Q8W based on PK modeling 17 25 -35 Q12W based on PK modeling -40 43-56 days Predicted range¹ MAINTENANCE PK SIMULATIONS Q12W SPY001 Dosing Simulation based on 50d half-life Concentration (µg/mL) Source: ¹Human YTE mAb half-life is on average 3.1x of NHP half-life; Rosario, M, et. al. (2017); 2Feagan, et. al. (2013) 100 80- 60 40 20 0 0 12 24 36 Weeks (At Steady-State) SPY001 SC Q12W VEDO IV Q8W 48 SPY001 Ctrough exceeds vedo by ~1.5x 6 ug/mL Ctrough associated with maximal efficacy² 14

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