A Phase 1 interventional study of Rifampin 150 mg, 300 mg capsules and 25 mg/mL oral suspension in Idiopathic Infantile Hypercalcemia - Mild Form, sponsored by The Hospital for Sick Children. Status unknown at 1 site in Canada. Open to participants aged 6 Months to 17 Years. Per ClinicalTrials.gov, last updated 2021-08-31.
Sponsored by The Hospital for Sick Children · Phase 1, Interventional, and Treatment
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.
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.
Exclusion Criteria:
All subjects
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
Also known as: Rifadin, Rofact, Rifampicin
Change in Serum Calcium
Measured at baseline and every 2 months (8 weeks)
Time frame: 40 weeks
Change in Serum Parathyroid Hormone
measured at baseline and every 2 months ( 8 weeks)
Time frame: 40 weeks
Change in Urinary calcium excretion
Measured at baseline and every 2 months( 8 weeks)
Time frame: 40 weeks
Nephrocalcinosis
Renal ultrasound performed before and after treatment
Time frame: 40 weeks
Plan to share: Undecided
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The Hospital for Sick Children