In Vivo Efficacy of Olorofim against Systemic Scedosporiosis and Lomentosporiosis

Clinically relevant members of the Scedosporium/Pseudallescheria species complex and Lomentospora prolificans are generally resistant against currently available systemic antifungal agents in vitro, and infection due to these species is difficult to treat. We studied the in vivo efficacy of a new fungicidal agent, olorofim (formerly F901318), against scedosporiosis and lomentosporiosis in neutropenic animals. Cyclophosphamide-immunosuppressed CD-1 mice infected by Scedosporium apiospermum, Pseudallescheria boydii (Scedosporium boydii), and Lomentospora prolificans were treated by intraperitoneal administration of olorofim (15 mg/kg of body weight every 8 h for 9 days). The efficacy of olorofim treatment was assessed by the survival rate at 10 days postinfection, levels of serum (1-3)-β-d-glucan (BG), histopathology, and fungal burdens of kidneys 3 days postinfection. Olorofim therapy significantly improved survival compared to that of the untreated controls; 80%, 100%, and 100% of treated mice survived infection by Scedosporium apiospermum, Pseudallescheria boydii, and Lomentospora prolificans, respectively, while less than 20% of the control mice (phosphate-buffered saline [PBS] treated) survived at 10 days postinfection. In the olorofim-treated neutropenic CD-1 mice infected with any of the three species, serum BG levels were significantly suppressed and fungal DNA detected in the target organs was significantly lower than in controls. Furthermore, histopathology of kidneys revealed no or only a few lesions with hyphal elements in the olorofim-treated mice, while numerous fungal hyphae were present in control mice. These results indicate olorofim to be a promising therapeutic agent for systemic scedosporiosis/lomentosporiosis, devastating emerging fungal infections that are difficult to treat with currently available antifungals.