TIO or tumor induced osteomalacia is a rare disease that is characterized by development of tumors that cause weakend and softened bones. The tumors associated with TIO release a peptide hormone like substance known as fibroblast growth factor 23 (FGF 23) that lowers phosphate levels.
FGF23 regulate the level of phosphate which are required for bone maintenance, energy production by cells and nerve function. When body does not have enough phosphate, bones begin to soften and weaken, causing osteomalacia.
U.S. Food and Drug Administration approved Crysvita ( Burosumab-twza ) injection to treat patients age two and older with tumor induced osteomalacia.
The safety and efficacy of Crysvita was evaluated in the studies. Patients received Crysvita every 4 weeks. In one of the two studies conducted, half of the patient achieved the normal level through the week 24 and maintained the normal level through week 144. In second study 69% of participant achieved normal level of phosphate through week 24 and maintained the normal level through week 88.
Rash and hives have been reported as hypersensitive reactions in some of the patients. Further the increased level of the Phosphorus more than normal can also be a risk for nephrocalcinosis. Nephrocalcinosis is a disorder that occurs when too much calcium is deposited in the kidney.
Most common side effects found with Crysvita were tooth abscess, muscle spasm, dizziness, constipation injection site reaction and headache.
Patients who are on vitamin D are phosphate supplement, having normal level of phosphate and the patients with severe kidney impairment or end stage renal disease should not take this drug.