Phosphorus is a mineral that is important for healthy bones. People with TIO have too little phosphorus, leading to weakening of their bones. In CRYSVITA clinical studies, adults with TIO had the level of phosphorus in their blood, described as “serum phosphorus,” measured at Week 24 (Studies 6 and 7), Week 88 (Study 7), and Week 144 (Study 6).
Serum phosphorus level (mg/dL)
- *Normal levels of serum phosphorus for this group of patients ranged from 2.5 to 4.5 milligrams/deciliter (mg/dL). The normal range of serum phosphorus levels varies by age and sex, and ranges may vary by testing laboratory.
Both studies of adults with TIO showed that CRYSVITA increased and maintained serum phosphorus
- Study 6, serum phosphorus increased from 1.60 mg/dL to 2.64 mg/dL at Week 24 and was sustained through Week 144 with CRYSVITA
- Study 7, serum phosphorus increased from 1.62 mg/dL to 2.63 mg/dL at Week 24 and was sustained through Week 88 with CRYSVITA
By Week 24, 7 out of 14 patients (50%) in Study 6 and 9 out of 13 patients (69%) in Study 7 had serum phosphorus within the normal range
CRYSVITA increased serum phosphorus levels for all patients (100%) by the end of the trial period in Studies 6 and 7
Under normal conditions, minerals like phosphorus are continuously added to bones. This process, called mineralization, helps to keep bones hard. People with TIO don’t have enough phosphorus for bones to properly mineralize, which causes some parts of the bone to become “soft” and more likely to break. “Softening” and weakening of the bones is called osteomalacia.
In a study of adults with TIO aged 33 to 68 years (Study 6), small samples of bone were taken and examined for signs of healing of osteomalacia. Bone samples were taken before patients started treatment with CRYSVITA and then again after the patients were treated with CRYSVITA every 4 weeks for 48 weeks.