Hexasodium fytate for the treatment of calciphylaxis: a randomised, double-blind, phase 3, placebo-controlled trial with an open-label extension

Background: In the CALCIPHYX trial, we investigated hexasodium fytate, an inhibitor of vascular calcification, for the treatment of calcific uraemic arteriolopathy (calciphylaxis), a rare condition characterised by painful, non-healing skin lesions.

Methods: In this international, phase 3, randomised, double-blind, placebo-controlled trial, adults with an ulcerated calciphylaxis lesion and pain visual analogue scale (VAS) score ≥50/100 were randomised 1:1 to hexasodium fytate 7 mg/kg or placebo intravenously during maintenance haemodialysis. Primary efficacy outcomes were an 8-item modification of the Bates-Jensen Wound Assessment Tool (BWAT-CUA) and Pain VAS in the intention-to-treat population. ClinicalTrials.gov number: NCT04195906.

Findings: Overall, 34/37 patients randomised to hexasodium fytate and 26/34 patients randomised to placebo completed the 12-week randomised treatment period. At Week 12, both groups (hexasodium fytate versus placebo) showed similar improvements in BWAT-CUA (mean [standard deviation (SD)], -5.3 [5.2] versus -6.0 [6.2]; least squares mean difference, 0.3 [96% confidence interval (CI): -2.5, 3.0]; p = 0.88) and Pain VAS (mean [SD], -19.5 [26.9] versus -32.2 [38.5]; least squares mean difference, 11.5 [96% CI: -4.8, 27.8]; p = 0.15). One patient randomised to placebo briefly received hexasodium fytate in error. Serious adverse events through Week 12 included: calciphylaxis-related events leading to hospitalisation (2/38 [5%] versus 11/33 [33%]) and death (1/38 [3%] versus 5/33 [15%]). During the subsequent 12 weeks of open-label hexasodium fytate and 4 weeks of follow-up, there were no additional calciphylaxis-related events leading to hospitalisation. Over the course of the entire trial, deaths were 2/38 [5%] for the hexasodium fytate group and 7/33 [21%] for the placebo group.

Interpretation: In patients with calciphylaxis, BWAT-CUA and Pain VAS improved similarly in hexasodium fytate- and placebo-treated patients; over the course of the entire trial, there were fewer deaths and calciphylaxis-related events leading to hospitalisation in the hexasodium fytate group.

Funding: Funded by Sanifit, a CSL Vifor company.