Silensomes™ are human pooled liver microsomes in which one specific CYP has been chemically knocked out. Silensomes™ is a single unique and representative model, capable of directly quantifying and predicting the contribution of CYP enzymes in drug metabolism. Silensomes™ are validated human pooled liver microsomes (HLMs) chemically and irreversibly inactivated for one specific CYP using mechanism based inhibitors (MBI). Each Silensomes™ is available as ready-to-use HLMs chemically knocked-out for one specific CYP activity (1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4) with each showing high specificity and efficiency of their targeted CYP inhibition (>80%), and only minor impact (<20%) Silensomes™: the model of choice for determination of the CYP contribution all along the development plan of a new chemical entity 1. Irreversibly inhibited CYPs 2. For initial rate conditions 3. For saturating conditions 4. One single model for CYP phenotyping assays, instead of a battery of in-vitro tests 5. Quantitative: the true contribution of the CYP450 in the metabolism of the compound can be measured 6. A powerful model with an excellent specificity, potency, stability and predictability to ensure reliable extrapolation of the drug-drug interaction risk 7. More representative of in vivo, using human liver microsomes rather than recombinant enzymes isolated from non-mammalian cells Silensomes™ are available for compound screening purposes and also for regulatory validation.