Summary of results from the in vitro evaluation of avibactam inhibition potential for human cytochrome P450 enzymes
Values show mean percentage (CV%) enzyme activity vs. controls. Microsomes isolated from pooled liver samples from 15 to 30 male and female donors and two individual samples from separate male donors were preincubated with and without NADPH (to assess time-dependent inhibition) with varying concentrations of avibactam (data for 200 μM shown) before the addition of reference substrates. For CYP3A4/5, inhibition was studied using three substrates (midazolam, testosterone, and nifedipine), which interact with three different binding sites. Parallel incubations were done with reference inhibitors as positive controls. Enzymatic activities were determined by measuring the concentration of formed metabolite using a high-performance liquid chromatography with ultraviolet detection method for all enzymes except CYP2A6, which was determined by fluorometry.
| Enzyme Assaya | CYP1A2 | CYP2A6 | CYP2C8 | CYP2C9 | CYP2C19b | CYP2D6 | CYP2E1b | CYP3A4/5 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Nifedipineb | Midazolam | Testosterone | ||||||||||||||||||
| NADPH Preincubation | – | + | – | + | – | + | – | + | – | + | – | + | – | + | – | + | – | + | – | + |
| Control | 100 (3) | 100 (1) | 100 (13) | 100 (2) | 100 (6) | 100 (2) | 100 (3) | 100 (6) | 100 (7) / 100 (9) | 100 (2) / 100 (2) | 100 (6) | 100 (8) | 100 (8) / 100 (7) | 100 (5) /100 (2) | 100 (5) / 100 (5) | 100 (6) / 100 (7) | 100 (5) | 100 (5) | 100 (4) | 100 (6) |
| Reference inhibitor | 32 (2) | <5 | 95 (3) | 13 (3) | <17 | <22 | 18 (2) | 19 (1) | 29 (1) | 26 (3) | <26 | <29 | 12 (0) | <4 | 25 (0) / 23 (1) | 31 (5) / 34 (4) | 15 (2) | 16 (4) | 17 (3) | 16 (1) |
| Avibactam (200 µM) | 114 (3) | 106 (5) | 128 (10) | 96 (15) | 100 (1) | 107 (4) | 71 (4) | 86 (7) | 95 (14) | 105 (6) | 87 (4) | 102 (8) | 93 (3) | 95 (1) | 126 (7) | 115 (9) | 99 (1) | 96 (4) | 102 (2) | 104 (5) |