NCT03384121

The Antibiotic Rifampin to Reduce High Levels of Blood and Urine Calcium in IIH

Rifampin to Reduce Elevated Levels of Blood and Urine Calcium in Patients With Idiopathic Infantile Hypercalcemia

• Status: Unknown
• Phase: Phase 1
• Study type: Interventional
• Enrollment: 5 (estimated)
• Sponsor: The Hospital for Sick Children · Academic / Other
• Sex: All
• Age: 6 Months – 17 Years
• Healthy volunteers: Not accepted

Summary

Idiopathic infantile hypercalcemia(IIH) is a rare,genetic disorder of mineral metabolism. Biallelic loss of functions mutations of CYP24A1, the gene encoding the 24-hydroxylase enzyme that represents the principal pathway for inactivation of vitamin D metabolites, cause the most common and severe form of IIH.Investigators have preliminary data supporting a novel therapeutic approach to suggest rifampin as an investigational drug to induce over-expression of CYP3A4, an important enzyme that provides an alternate catabolic pathway for inactivation of vitamin D metabolites. In this study, investigators will recruit 5 patients with biallelic inactivating mutations of CYP24A1. Participants will be followed prospectively for a total 6-11 months. This will include 2 months of observation, 2 months of receiving the starting dose of rifampin, followed by 2 month washout phase. Efficacy of the starting dose of rifampin will be determined prior to proceeding only in non responders to the escalation dose of rifampin 10mg/kg/day.

Detailed description

Idiopathic infantile hypercalcemia(IIH) is a rare,genetic disorder of mineral metabolism characterized by severe hypercalcemia and/or hypercalciuria, suppressed serum levels of parathyroid hormone (PTH), elevated levels of the active vitamin D metabolite, 1,25(OH)2D, and nephrocalcinosis. Biallelic loss of functions mutations of CYP24A1, the gene encoding the 24-hydroxylase enzyme that represents the principal pathway for inactivation of vitamin D metabolites, cause the most common and severe form of IIH. Investigators have preliminary data supporting a novel therapeutic approach to suggest rifampin as an investigational drug to induce over-expression of CYP3A4, an important P450 microsomal enzyme that is expressed in the liver and intestine. When CYP3A4 is induced, the increased enzyme activity provides an alternative catabolic pathway for inactivation of vitamin D metabolites. The purpose of this study is to obtain results and support for an open label, escalating dose study to assess the effect, safety, and tolerability of once daily oral rifampin for two months in participants with IIH due to inactivating mutations in CYP24A1. In this study, Investigators will recruit 5 patients with biallelic inactivating mutations of CYP24A1. Participants will be followed prospectively for a total 6-11 months. This will include 2 months of observation, 2 months of receiving the starting dose of rifampin, followed by 2 month washout phase. Efficacy of the starting dose of rifampin will be determined prior to proceeding only in non responders to the escalation dose of rifampin 10mg/kg/day. In addition to determining if this treatment is efficacious in reducing elevated serum and urinary calcium in patients, it will be determined if there is a dose effect of rifampin. As well, detailed measurements of vitamin D metabolites will determine if rifampin reduces hypercalcemia through increased CYP3A4 activity.

Conditions

• Idiopathic Infantile Hypercalcemia - Mild Form

Interventions

Type	Name	Description
DRUG	Rifampin 150 mg, 300 mg capsules and 25 mg/mL oral suspension	Starting Dose (V2): 5 mg/kg/day (max 600mg/day) orally for 2 months followed by a 2 month washout period V4: After washout period, only Non-responders will escalate dose to 10 mg/kg/day (max 600mg/day) orally for 2 months

Timeline

• Start date: 2018-02-22
• Primary completion: 2021-12-31
• Completion: 2021-12-31
• First posted: 2017-12-27
• Last updated: 2021-08-31

Locations

1 site across 1 country: Canada