Bioresorbable coronary stents represent a step toward strategies without permanent metallic implants, although the first polymer-based platforms showed mechanical limitations and suboptimal clinical results. The sirolimus-eluting iron bioresorbable stent (IBS) was developed to overcome these barriers, integrating an ultrathin (55 μm) iron framework with a degradable polymer coating and controlled drug release. The IRONMAN II trial evaluated its performance compared with a cobalt-chromium everolimus-eluting stent (CoCr-EES) in the treatment of non-complex de novo coronary lesions.
This prospective, multicenter, randomized, single-blind, non-inferiority trial was conducted in 36 centers across China and included 518 patients (259 per arm; 536 lesions in total). Inclusion criteria were single or double lesions with ≥70 % stenosis (or ≥50 % with ischemic evidence), length ≤33 mm and vessel diameter 2.5–4.0 mm. Patients with severe heart failure, left main disease, chronic occlusion, or in-stent restenosis were excluded.
The primary endpoint was late luminal loss (LLL) at 2 years, assessed by quantitative coronary angiography (QCA). Secondary endpoints included quantitative flow ratio (QFR), mean flow area by OCT in the treated segment, and clinical events such as target lesion failure (TLF) and patient-oriented composite endpoint (PoCE).
At 24 months, late luminal loss was 0.29 ± 0.39 mm with IBS vs 0.21 ± 0.39 mm with CoCr-EES, meeting the non-inferiority criterion (p < 0.025). QFR values were identical between groups (0.89 ± 0.11; p < 0.001 for non-inferiority), and the mean OCT flow area was also equivalent (7.0 ± 3.0 mm² in both arms; p < 0.001 for non-inferiority).
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Device, lesion, and procedural success rates exceeded 95 %. Clinically, the incidence of TLF and PoCE was low and comparable between groups, with no significant differences in thrombosis or target-vessel MI.
Conclusion
The IRONMAN II study confirms the safety and efficacy of the sirolimus-eluting iron bioresorbable stent, with angiographic and functional outcomes non-inferior to contemporary metallic stents at 2 years. Its ultrathin profile, high radial strength, and progressive resorption make it a promising option toward a metal-free coronary intervention strategy.
Presented by Lei Song et al. at TCT 2025 (Late-Breaking Clinical Trials), October 27, San Francisco, USA.
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