The iridium complexes Ir1-3, with N,N-chelated ligands in the metformin (a biguanide antidiabetic drug) family, were already highlighted in our previous analysis for their ability to inhibit MRSA at low concentrations. Indeed these complexes were already reported by the group of Sadler in an in-depth study on their antimicrobial properties. In our extended screening, these compounds maintained their high level of activity across the panel without any significant differences between the three complexes. All three exhibited moderate levels of cytotoxicity with CC50 values in the 50-100 µM range and also significant haemolysis (Table in SI). Overall the high activity coupled with moderate toxicity still results in favorable therapeutic indices in the range of 2600-3383 for Ir1-3, making this class of iridium compounds promising for antimicrobial applications. The investigation of more derivatives and their mode of action is encouraged.