Sirolimus-eluting iron bioresorbable scaffold (IBS) is safe and effective for treating non-complex coronary artery disease, with benefits continuing at 2-years post-procedure, in the IRONMAN II trial. This was reported in a late-breaking session at TCT 2025 on Monday. The results support a 5-year follow-up from the previous first-in-man IRONMAN I study which established the preliminary safety and effectiveness of the novel thin-strut device in 45 patients with single de novo lesions. The latest findings — pitting the IBS against contemporary metallic everolimus-eluting stends (EES) for non-inferiority — were presented at the San Fransisco conference by Lei Song, MD, PhD, from Yale School of Medicine, New Haven, on behalf of the trial’s investigators. Resorbable implants have been a key focus in recent times for interventional cardiologists, with a new drive towards “leave nothing behind” thinking. Baseline dynamics IRONMAN II recruited 518 patients (259 to IBS and 259 to Cobalt Chromium Everolimus-Eluting Stent [CoCr-EES]) aged 18 to 75 years who showed evidence of myocardial ischemia scheduled for percutaneous coronary intervention (PCI). Each cohort had 268 lesions. Patients had 1 or 2 target lesions in separate vessels, diameter stenosis ≥70% (or ≥ 50% with ischemic evidence), lesion length ≤ 33mm and reference vessel diameter between 2.5mm to 4mm. Exclusions included severe heart failure (HF), left ventricular ejection fraction (LVEF) below 40%, chronic total occlusion (CTO) or left main (LM) coronary artery disease, ostial lesion, branch vessel diameter ≥ 2.5mm, target vessel thrombus, in-stent restenosis and myocardial bridge at target lesion. At baseline, the two groups were of similar age (a mean of 59.5 years ± 9.5 in IBS and 60.4 years ± 9.9 in CoCr-EES), similarly sex-weighted (70.7% vs 68% male, respectively) and had similar comorbidity rates including diabetes (27./4% vs 29.7%, respectively), hypertension (62.9% vs 63.7%, respectively) and hyperlipidemia (34.4% vs 32.4%, respectively). Lesion locations were mostly in the left anterior descending (LAD) artery (57.8% in IBS vs 61.6% in CoCr-Ees), left circumflex (LCX, 14.2% vs 12.3%, respectively) or right coronary artery (RCA, 28% vs 26.1%, respectively). Pre-dilation was performed for the vast majority (for all but one lesion in the CoCr-EES group). Results The 2-year primary endpoint measure in the intention-to-treat (ITT) population — noninferiority of in-segment late-lumen loss (LLL) measured by quantitative coronary angiography (QCA) at 2 years — was a mean of 0.28 ± 0.52 in 204 lesions across 197 available patients in the IBS group and 0.23 ± 0.43 across 195 lesions in 188 available patients in CoCr-EES, Song reported at TCT. A generalized linear mixed model (GLMM) lesion level analysis found LLL was a mean of 0.32 ± 0.04 in the 204 lesions of the IBS group and 0.24 ± 0.04 in the 195 CoCr-EES lesions (difference 0.08; 95% confidence interval [CI]: -0.02 to 0.18; P for non-inferiority = 0.03). In the ‘per-protocol’ population (referring to those who strictly followed the clinical trial rules), mean LLL was 0.27 ± 0·52 in 197 lesions and 0.23 ± 0.43 in 193 lesions. GLMM analysis at lesion level returned an LLL of 0.32 ± 0·04 in IBS and 0.24 ± 0.04 in CoCr-EES (difference 0.08; 95% CI: -0.03 to 0.18; P for non-inferiority = 0.03). Powered secondary endpoints included quantitative flow ratio (QFR) measurements at 2 years for both noninferiority and subsequently superiority, and a cross-sectional mean flow area measured by optical coherence tomography (OCT) for noninferiority in subgroups of 25 patients per cohort at 2 years. Target vessel QFR in the ITT population returned a cross-sectional mean flow area of 0.90 (± 0.13) in 191 lesions and 0.92 (± 0.09) in 184 lesions (difference -0.02; 95% CI: -0.04 to 0; P for inferiority = 0.05 and P for superiority = 0.08). In the per-protocol set, the mean was 0.90 (± 0.12) vs 0.92 (± 0.09) respectively (difference -0.02; 95% CI: -0.04 to 0; P for inferiority = 0.05 and P for superiority = 0.10). TLF (Target Lesion Failure) occurred in 7.4% of the IBS group bs 5.4% of the CoCr-EES group (hazard ratio [HR] 1.37; 95% CI: 0.69 to 2.73; log-rank P value = 0.37). A patient-oriented composite endpoint (PoCE) of death, any myocardial infarction and any revascularization occurred in 19.3% of the IBS cohort vs 14.3% of CoCr-EES (HR 1.39; 95% CI: 0.91 to 2.12; log-rank P value = 0.13). Song concluded that IRONMAN II showed the novel thin-strut IBS to be safe and effective for treating non-complex coronary artery disease. “Device, lesion, and clinical success rates were high and comparable between groups. 71.6% of IBS lesions were [American College of Cardiology/ American Heart Association classification] B2/C lesions,” Dr. Song added. Dr. Song went on to highlight study limitations, including the fact it was not possible to double-blind the trial due to differences in appearance, packaging and radiopaque between the devoices. “However, potential bias was minimized through blinding the QCA core-lab […] to device allocation,” he said. Further research is needed in complex coronary anatomy, Dr. Song concluded, noting that the 2-year follow-up period is yet “premature to examine the potential long-term benefits of IBS as scaffold resorption is not yet complete.” Image Caption: Lei Song, MD, PhD, presents during a press conference Monday, October 27, at the Transcatheter Cardiovascular Therapeutics (TCT) 2025 conference in San Francisco. Image Credit: Screenshot by Bailey G. Salimes, CRTonline.org.