The selection of a chassis organism can be guided by the desired site of activity and pharmacokinetic properties of the chassis, as well as manufacturing feasibility. The design of genetic circuits may also be influenced by the circuit’s effectors, pragmatic concerns regarding inducer compounds, and the genetic stability of regulatory circuits. Critically, the design of an engineered bacterial drug may also be constrained by considerations for the needs of patients. b Optimal strain design often requires a balance between strain suitability for function in the target microenvironment and concerns for feasibility of manufacturing and clinical development.[3]