**3.4 Sanfetrinem (Trinem beta-lactam)**

Sanfetrinem cilexetil is an orally available tricyclic beta-lactam developed by Glaxo Smith Kline (GSK) in the early 1990's with broad antibacterial activity on both Gram-negative and Gram-positive bacteria. The development of this drug was halted after phase 2 clinical trials. However, it has recently been identified as a potential beta-lactam against *M. tuberculosis*, with an MIC of 1.5 μg/mL against H37Rv and an intracellular MIC of 0.5 μg/mL in THP1 monocytes. Furthermore, it has been reported that the drug showed potent activity against a range of susceptible and resistant clinical isolates with an MIC90 of 1–4 μg/mL. In an *in vivo* investigation, sanfetrinem cilexetil was comparable to meropenem and amoxicillin/ clavulanate [27]. Similar to other carbapenems, it targets the cell wall by inhibiting the formation of peptidoglycan [28]. This drug is currently under pre-clinical investigation with a planned phase 1 clinical trial.
