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

Phase 1

• Conditions: Idiopathic Infantile Hypercalcemia - Mild Form
• Interventions: Drug: Rifampin 150 mg, 300 mg capsules and 25 mg/mL oral suspension

• Registration Number: NCT03384121
• Lead Sponsor: The Hospital for Sick Children

Brief 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.

Study Timeline

• Study First Submitted: 2017-12-13
• Study First Submitted QC: 2017-12-22
• Study First Posted: 2017-12-27
• Study Start: 2018-02-22
• Status Verified: 2021-08
• Last Update Submitted: 2021-08-30
• Last Update Posted: 2021-08-31
• Primary Completion: 2021-12-31
• Study Completion: 2021-12-31

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 5

Inclusion Criteria

• all patients between 6 months- 17 years of age with the clinical phenotype of idiopathic infantile hypercalcemia
• Biochemical evidence of this disorder: Serum calcium>upper limit of the reference age for range; high, 1,25 (OH)D; reduced PTH, reduced 24,25(OH)2D, and suppresses 24,1,25 (OH)2D, normal serum creatinine, AST, and ALT with or without
• biallelic inactivating mutations of CYP24A1
• mutations in newly published genes which are shown during the course of the study to cause an inappropriate increase in 1,25 (OH)2D

Exclusion Criteria

• Allergy to rifampin or related medications
• Pregnancy or breastfeeding
• Significant cardiac, hepatic, or endocrine comorbidities
• Taking any medications/foods known to interact with CYP3A4 or 1,25 (OH)D
• Parents or guardians or subjects who in the opinion of the Investigator may be non compliant with study schedules or procedures
• Other comorbidities considered unsuitable by the investigator, including TB

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Rifampin	Rifampin 150 mg, 300 mg capsules and 25 mg/mL oral suspension	All subjects

Primary Outcome Measures

Name	Time	Method
Change in Urinary calcium excretion	40 weeks	Measured at baseline and every 2 months( 8 weeks)
Change in Serum Calcium	40 weeks	Measured at baseline and every 2 months (8 weeks)
Change in Serum Parathyroid Hormone	40 weeks	measured at baseline and every 2 months ( 8 weeks)

Secondary Outcome Measures

Name	Time	Method
Nephrocalcinosis	40 weeks	Renal ultrasound performed before and after treatment

Trial Locations

Locations (1)

The Hospital for Sick Children; 🇨🇦 Toronto, Ontario, Canada