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

Last updated: August 30, 2021
Sponsor: The Hospital for Sick Children
Overall Status: Active - Recruiting

Phase

1

Condition

Hypercalcemia

Treatment

N/A

Clinical Study ID

NCT03384121
1000057141
  • Ages 6-17
  • All Genders

Study 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.

Eligibility Criteria

Inclusion

Inclusion Criteria:

  • all patients between 6 months- 17 years of age with the clinical phenotype ofidiopathic infantile hypercalcemia
  • Biochemical evidence of this disorder: Serum calcium>upper limit of the reference agefor 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 tocause an inappropriate increase in 1,25 (OH)2D

Exclusion

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 noncompliant with study schedules or procedures
  • Other comorbidities considered unsuitable by the investigator, including TB

Study Design

Total Participants: 5
Study Start date:
February 22, 2018
Estimated Completion Date:
December 31, 2021

Study 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.

Connect with a study center

  • The Hospital for Sick Children

    Toronto, Ontario M5G 1X8
    Canada

    Active - Recruiting

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