Evaluation of the cytochrome P450-mediated drug interaction profile of olorofim

Olorofim is a novel oral antifungal agent which selectively inhibits the fungal enzyme dihydroorotate dehydrogenase found in molds including Aspergillus, Scedosporium, Lomentospora, and Scopulariopsis and in dimorphic fungi such as Coccidioides. Based on in vitro studies, clinical pharmacology, and pharmacokinetic (PK) data from the Phase 2b FORMULA study (F901318/0032) as well as physiologically based PK (PBPK) modeling of drug interactions, the drug’s CYP-mediated interactions are now well understood. Olorofim is mainly metabolized by cytochrome P450 (CYP) CYP3A4, with minor contributions from CYP2C8 and CYP2C9. In vitro studies found that it inhibits CYP3A4, weakly inhibits CYP2D6 and CYP2C8, and weakly induces CYP1A2 and CYP2B6. Phase I studies confirm it is predominantly cleared by CYP3A4 and weakly inhibits CYP3A4. In the Phase 2b FORMULA study, co-administered sensitive CYP3A4 substrates required limited dose reductions when using olorofim. When used with strong CYP3A4 inhibitors, dual moderate inhibitors like fluconazole, or CYP3A4 inducers, dose adjustments were needed for olorofim. Physiologically based PK (PBPK) modeling predicted moderate effects with CYP3A4 inhibitors or inducers and negligible effects with weak CYP3A4 inhibitors or strong inhibitors of CYP2D6, CYP2C8, and CYP2C9. Overall, the drug’s interaction profile is predictable and manageable, making it a suitable candidate drug to use in treating patients with invasive fungal disease (IFD), who often require polypharmacy.