Fidrisertib for fibrodysplasia ossificans progressiva for people aged 5 years and over

Fidrisertib is in clinical development for fibrodysplasia ossificans progressiva (FOP). FOP is an ultra-rare disease which results in the formation of unwanted bone in muscles, tendons, and
ligaments throughout the body where bone would not normally be present (this is known as heterotopic ossification). FOP is present at birth and malformations of the great toes and
occasionally thumbs are the first clinical signs of the disease. FOP is caused by spontaneous mutations within the gene ACVR1 which is responsible for regulating bone and muscle growth.
This causes a receptor to be turned on which in turn causes the overgrowth of bone and cartilage seen in the disease. This causes immobility to patients usually by the second decade of life, resulting in wheelchair use and eventually death. In some cases, bone growth may differ between patients and may be faster or slower.