Phase I/II Study of Heme Arginate and Tin Mesoporphyrin for Acute Porphyria

Porphyria

inborn errors of metabolism, acute porphyria, rare disease

OBJECTIVES: I. Evaluate the efficacy and safety of heme arginate in the treatment of 20 patients with acute attacks of porphyria. II. Evaluate the efficacy and safety of heme arginate in preventing frequent exacerbations of acute porphyria in up to 15 patients. III. Estimate the lowest effective dose of heme arginate (0.3, 1.0, or 3.0 mg/kg) in reducing porphyrin precursors in 12 stable patients with acute intermittent porphyria in remission. IV. Evaluate the safety and efficacy of tin mesoporphyrin used in combination with heme arginate in reducing porphyrin precursors in 12 stable patients with acute intermittent porphyria in remission.

PROTOCOL OUTLINE: This project involves 4 studies: an unblinded multicenter treatment study, an unblinded prevention study, a controlled dose-ranging study, and a controlled drug combination dose-ranging study. In the treatment study, participants with acute attacks of porphyria receive intravenous heme arginate daily for 4 days. Treatment may be extended to 7 days in patients with severe attacks and slow recovery; these data are analyzed separately. In the prevention study, participants receive weekly infusions of heme arginate for 6 months. Treatment may be extended in selected cases; these data are analyzed separately. If an acute attack occurs, patients are treated with a standard course of heme arginate. Participants are followed weekly for 6 months after preventive treatment. In the dose-ranging study, 4 groups of 3 patients are randomly assigned to standard and low-dose heme arginate infusions, administered daily for 4 days. After a washout of 4-12 weeks, patients are crossed to a second dose. In 2 of the 4 groups, patients cross between heme arginate and a normal saline control. In the combination dose-ranging study, 4 groups of 3 patients are randomly assigned to 1 of 2 doses of tin mesoporphyrin. After a 4-12 week washout, these patients are crossed to a standard or low-dose heme arginate infusion. After a second 4-12 week washout, patients are given a combination infusion of tin mesoporphyrin followed by heme arginate. All participants are given a special diet to prevent fluctuations in porphyrin precursors.

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