Publication

• Title: Intravenous Tirofiban After Tenecteplase in Acute Ischemic Stroke: The INSTANT Randomized Clinical Trial
• Acronym: INSTANT
• Year: 2026
• Journal published in: JAMA
• Citation: INSTANT Trial Authors for the INSTANT Investigators. Intravenous tirofiban after tenecteplase in acute ischemic stroke: the INSTANT randomized clinical trial. JAMA. Published online May 8, 2026.

Context & Rationale

• Background

  Tenecteplase 0.25 mg/kg is now an accepted thrombolytic option for selected patients with acute ischaemic stroke, with contemporary AHA/ASA and European Stroke Organisation guidance supporting its use in defined acute stroke settings.¹²
• Background

  A clinically important subgroup shows little improvement, neurological deterioration, or neurological fluctuation in the first 24 hours after thrombolysis; proposed mechanisms include residual platelet-rich thrombosis, re-occlusion, failed recanalisation, and microcirculatory obstruction.
• Background

  Tirofiban is a rapid-onset, short half-life glycoprotein IIb/IIIa inhibitor; prior evidence included the SaTIS safety trial, RESCUE BT2 in non-large-vessel occlusion stroke, TREND in early neurological deterioration, and ASSET-IT after intravenous thrombolysis.³⁴⁵⁶
• Research Question/Hypothesis

  INSTANT tested whether adjunctive intravenous tirofiban, started after an inadequate clinical response to intravenous tenecteplase, improves 90-day excellent functional outcome in patients without large or medium vessel occlusion and without a cardioembolic source.
• Why This Matters

  The trial targeted a narrow, mechanistically plausible rescue population: patients already treated with tenecteplase, not eligible for thrombectomy, still symptomatic at 4–24 hours, and judged at lower haemorrhagic risk because large infarct, cardioembolism, and visible occlusion were excluded.

Design & Methods

• Research Question: In adults with acute ischaemic stroke who had received intravenous tenecteplase and had an inadequate response within 4–24 hours, and who had no large or medium vessel occlusion or cardioembolic source, does intravenous tirofiban increase the proportion with mRS 0–1 at 90 days compared with placebo?
• Study Type: Investigator-initiated, multicentre, randomised, double-blind, double-dummy, placebo-controlled trial in 37 hospitals in China; randomisation was stratified by site using block size 4.
• Population:
  • All participants had acute ischaemic stroke treated with tenecteplase 0.25 mg/kg, maximum 25 mg, given as an intravenous bolus over 5–10 seconds.
  • Inclusion criteria: age ≥18 years; NIHSS score ≥4 before randomisation; inadequate response 4–24 hours after tenecteplase, defined as no significant change from baseline NIHSS, neurological deterioration, or neurological fluctuation; written informed consent.
  • Final inadequate response definition: no significant change was an NIHSS increase or decrease of 0 or 1 point; neurological deterioration was NIHSS worsening by ≥2 points; neurological fluctuation was a ≥4-point NIHSS increase followed by ≥4-point decrease, or the reverse.
  • Key exclusions: intracranial haemorrhage after thrombolysis but before randomisation; large or medium vessel occlusion on CTA, MRA, or DSA; confirmed or suspected cardioembolic stroke; platelet count <100×10⁹/L; GFR <30 mL/min; pregnancy or lactation; tirofiban allergy; relevant bleeding, severe organ disease, sepsis, intracranial tumour, arteriovenous malformation, aneurysm, terminal illness, or another trial.
• Intervention:
  • Intravenous tirofiban 0.3 μg/kg/min for 30 minutes, followed by 0.075 μg/kg/min for up to 47.5 hours.
  • Study drug was initiated as soon as possible after randomisation, ideally within 10 minutes, and at least 4 hours after tenecteplase completion.
  • In the tirofiban group, matching oral antiplatelet placebo was used initially; active aspirin 100 mg once daily, clopidogrel 75 mg once daily, or both was then used through 90-day follow-up.
• Comparison:
  • Matching saline placebo infusion with the same bolus and infusion schedule.
  • Patients in the placebo infusion group received active oral antiplatelet therapy at 24 hours after tenecteplase; the choice of aspirin, clopidogrel, or both was at the treating physician’s discretion.
  • Use of other anticoagulant or antiplatelet agents was prohibited during the first 48 hours after randomisation.
• Blinding: Double-blind and double-dummy; tirofiban, saline placebo, active antiplatelets, and oral placebos had identical packaging, and participants, treating clinicians, outcome assessors, the clinical events committee, and imaging core laboratory were blinded to assignment.
• Statistics: A total of 348 patients, 174 per group, was required to detect a 15% absolute increase in 90-day mRS 0–1, from 23% with placebo to 38% with tirofiban, with 85% power at a two-sided 5% significance level, allowing 5% attrition; the published protocol described the trial rationale and analytic approach.⁷ The primary analysis used the full analysis set, analysed by assigned treatment, with an unadjusted modified Poisson regression risk ratio; adjusted, per-protocol, complete-case, best-case, worst-case, and GEE sensitivity analyses were also reported.
• Follow-Up Period: Functional and quality-of-life outcomes were assessed at 90 days; symptomatic intracranial haemorrhage and any radiological intracranial haemorrhage were assessed within 48 hours.

Key Results

This trial was not stopped early. It randomised 359 patients, exceeding the planned 348, with final follow-up completed on October 11, 2025.

• The primary outcome was favourable, but the treatment effect was statistically fragile: adjusted primary analysis was not significant, and the centre-clustered GEE sensitivity analysis gave RR 1.22; 95% CI 0.99 to 1.49; P=0.06.
• Prespecified subgroup analyses showed no convincing effect modification: age interaction P=0.18, baseline NIHSS interaction P=0.95, last-known-well to randomisation interaction P=0.35, last-known-well to study drug administration interaction P=0.31, and oral antiplatelet strategy interaction P=0.42.
• Numerically favourable subgroups included age ≤67 years, 67/97 (69.1%) vs 45/89 (50.6%), RR 1.37; 95% CI 1.07 to 1.75, and study drug administration after the median 656 minutes from last-known-well, 65/91 (71.4%) vs 48/89 (53.9%), RR 1.32; 95% CI 1.04 to 1.67; these subgroup CIs were not adjusted for multiplicity.

Internal Validity

• Randomisation and Allocation: Randomisation used a central web-based system, 1:1 allocation, block size 4, and stratification by participating site; allocation concealment was credible.
• Drop out or exclusions: All 359 randomised patients received their assigned study drug; no crossover or failure to administer assigned treatment occurred; one placebo patient was lost to 90-day follow-up; 8 patients were excluded from the per-protocol set, 3 in the tirofiban group and 5 in the placebo group.
• Performance/Detection Bias: Blinding was unusually strong for an acute stroke pharmacology trial, with double-dummy infusion and oral medication, blinded outcome adjudication, blinded clinical events committee, and blinded imaging core laboratory.
• Protocol Adherence: Protocol delivery was strong at the level of assigned infusion, but oral antiplatelet timing differed by design; this preserved blinding and allowed a tirofiban-vs-placebo contrast during the infusion period, but makes the comparison a strategy of tirofiban with delayed active oral antiplatelets versus saline with earlier oral antiplatelets.
• Baseline Characteristics: Groups were well balanced: mean age 66±12 vs 67±10 years; female sex 39.0% vs 39.6%; median NIHSS 6 (IQR 5–9) vs 6 (IQR 5–9); ASPECTS 10 (IQR 9–10) vs 9 (IQR 9–10); hypertension 80.2% vs 81.3%; diabetes 36.2% vs 34.1%.
• Stroke phenotype: The population was predominantly mild-to-moderate, small-infarct, non-cardioembolic stroke: small-vessel occlusion accounted for 70.6% vs 75.8%, large artery atherosclerosis 11.9% vs 10.4%, unknown mechanism 17.5% vs 12.6%, and cardioembolism 0% vs 1.1%.
• Heterogeneity: Clinical heterogeneity was modest because the trial deliberately excluded cardioembolism and large/medium vessel occlusion, but stroke mechanism still varied; statistical heterogeneity was not obvious, with all subgroup interaction P values ≥0.18.
• Timing: Median last-known-well to tenecteplase was 180 minutes in both groups; median last-known-well to randomisation was 638 minutes vs 623 minutes; median thrombolysis completion to study drug administration was 424 minutes vs 471 minutes; this is biologically coherent for identifying non-responders, but later than ultra-early antiplatelet strategies.
• Dose: The tested tirofiban regimen was conservative: 0.3 μg/kg/min for 30 minutes followed by 0.075 μg/kg/min for up to 47.5 hours; the low haemorrhage rate supports safety in this selected population, but the optimal dose after tenecteplase remains unresolved.
• Separation of the Variable of Interest: Intravenous exposure was cleanly separated: tirofiban infusion for up to 47.5 hours versus matching saline placebo; oral antiplatelet strategy was similar by type, with monotherapy 96/177 (54.2%) vs 105/182 (57.7%), dual therapy 78/177 (44.1%) vs 75/182 (41.2%), and none 3/177 (1.7%) vs 2/182 (1.1%).
• Key Delivery Aspects: The trial required vascular imaging to exclude large or medium vessel occlusion and required urgent noncontrast CT in patients with deterioration or fluctuation before randomisation; 21 screened patients were excluded because post-thrombolysis haemorrhage was already evident.
• Crossover: No crossover occurred.
• Adjunctive therapy use: Oral antiplatelet selection was clinician-directed rather than randomised; monotherapy and dual antiplatelet proportions were numerically similar, but this remains an important co-intervention because the trial was not a pure “tirofiban plus identical antiplatelet background” comparison.
• Outcome Assessment: The primary outcome, mRS 0–1 at 90 days, is patient-centred and standard in stroke trials; central adjudication by two certified neurologists using video or voice recordings strengthened reliability.
• Safety Outcome Assessment: Symptomatic haemorrhage adjudication was rigorous, but follow-up imaging for radiological haemorrhage was not universal; intracranial haemorrhage denominators were 115 vs 102, leaving 142 patients without 48-hour imaging data for this safety endpoint.
• Statistical Rigor: The trial met its planned sample size and followed a prespecified primary unadjusted full-analysis-set approach; however, no multiplicity adjustment was applied to secondary outcomes, the adjusted primary analysis was not significant, and the primary result was sensitive to centre-clustered modelling.

Conclusion on Internal Validity: Internal validity is moderate-to-strong for trial conduct and outcome ascertainment, but the certainty of the treatment effect is moderate rather than high because the primary estimate is imprecise, adjusted analyses weaken the signal, and safety imaging was incomplete.

External Validity

• Population Representativeness: The trial enrolled only Chinese patients, largely with mild-to-moderate stroke, small infarct burden, and non-cardioembolic mechanisms; the supplemental representativeness statement explicitly notes that all enrolled patients were Han Chinese.
• Major exclusions: The results do not apply to large or medium vessel occlusion, suspected cardioembolism, atrial fibrillation, NIHSS <4, prestroke mRS >1, advanced renal failure, established post-thrombolysis haemorrhage, or patients eligible for thrombectomy.
• Thrombolysis window: 330 patients, 91.9%, received tenecteplase within 4.5 hours of last-known-well; applicability to extended-window thrombolysis is therefore uncertain.
• Healthcare system applicability: Translation requires rapid vascular imaging, ability to identify inadequate response between 4 and 24 hours, blinded or standardised mRS assessment for trial replication, infusion pump capacity for approximately 48 hours, and local comfort with off-label tirofiban in stroke.
• Aetiological applicability: Generalisability to populations with lower prevalence of intracranial atherosclerosis or different small-vessel disease biology is uncertain.
• Drug-specific applicability: The trial tested tenecteplase 0.25 mg/kg specifically; it should not be assumed to apply directly to alteplase-treated patients, higher-dose tenecteplase, or patients treated with mechanical thrombectomy.

Conclusion on External Validity: External validity is limited-to-moderate. The findings are most applicable to Chinese or similar practice environments treating selected non-cardioembolic, non-LVO/MVO, mild-to-moderate ischaemic stroke patients with inadequate response after standard-dose tenecteplase.

Strengths & Limitations

• Strengths: Randomised, placebo-controlled, double-blind, double-dummy design; concealed allocation; multicentre recruitment; high follow-up completeness; no crossover; central blinded mRS adjudication; blinded clinical events committee; blinded imaging core laboratory; prospectively published protocol and statistical analysis plan.
• Strengths: The trial studied a precise and clinically recognisable rescue phenotype: inadequate response after tenecteplase, no visible large/medium vessel occlusion, no cardioembolic source, and no pre-randomisation intracranial haemorrhage.
• Strengths: Treatment separation was strong for the intravenous intervention, and the control arm received guideline-concordant active oral antiplatelet therapy after the usual post-thrombolysis interval.
• Limitations: The effect estimate was fragile: unadjusted primary RR 1.22 was significant, but adjusted RR 1.17 was not, and the GEE sensitivity model crossed the null.
• Limitations: Secondary outcomes were exploratory because no multiplicity correction was applied.
• Limitations: The trial was too small to reliably assess rare but catastrophic bleeding events; one symptomatic intracranial haemorrhage occurred and was fatal.
• Limitations: Follow-up imaging was not mandated for all participants, limiting inference about asymptomatic and total intracranial haemorrhage.
• Limitations: Generalisability is restricted by the all-Chinese population, low-to-moderate stroke severity, high small-vessel stroke proportion, and exclusion of LVO/MVO, cardioembolism, and minor stroke.

Interpretation & Why It Matters

• Clinical signal

  INSTANT provides a plausible efficacy signal that platelet inhibition after tenecteplase may improve excellent recovery in selected patients who have not clinically responded to thrombolysis.
• Practice implication

  The trial should not be interpreted as broad permission for tirofiban after all thrombolysis; it supports further study and possibly cautious specialist consideration only in the narrow phenotype tested.
• Conceptual advance

  The trial reframes early post-thrombolysis antiplatelet therapy from a uniform hazard question to a precision-treatment question: selected non-cardioembolic, non-LVO/MVO, inadequate responders may be different from unselected thrombolysed stroke patients.
• What it does not settle

  INSTANT does not define the optimal timing, dose, duration, imaging surveillance strategy, oral antiplatelet combination, or applicability outside Chinese centres.

Controversies & Other Evidence

• Guideline position: The 2026 AHA/ASA acute ischaemic stroke guideline supports tenecteplase 0.25 mg/kg in eligible patients, but it predated INSTANT and therefore does not provide a recommendation for routine tirofiban after tenecteplase.¹
• Protocol evolution: A May 2025 amendment refined the inadequate response definition, including neurological deterioration by ≥2 NIHSS points in the final trial; this was approved before outcome analysis, but it widened the clinical phenotype compared with the original ≥4-point deterioration threshold in the published protocol.⁷
• Fragility of efficacy: The absolute increase in mRS 0–1 was clinically attractive, 12%, but the 95% CI for the NNT was broad, 4.6 to 72.1, and the adjusted primary analysis crossed the null.
• Safety uncertainty: Symptomatic intracranial haemorrhage was rare, but the single event in the tirofiban group was fatal; incomplete systematic imaging means total haemorrhage rates may be underestimated.
• Comparison with ASSET-IT: ASSET-IT randomised 414 patients to tirofiban and 418 to placebo within 60 minutes after thrombolysis, used alteplase in 75% and tenecteplase in 25%, and found mRS 0–1 at 90 days in 65.9% versus 54.9%, RR 1.20; 95% CI 1.07 to 1.34; P=0.001, with symptomatic intracranial haemorrhage 1.7% versus 0%.⁶
• Comparison with RESCUE BT2: RESCUE BT2 studied patients without large or medium vessel occlusion and found mRS 0–1 at 90 days in 29.1% with tirofiban versus 22.2% with aspirin, adjusted RR 1.26; 95% CI 1.04 to 1.53; P=0.02, with symptomatic intracranial haemorrhage 1.0% versus 0%.⁴
• Comparison with TREND: TREND found early neurological deterioration within 72 hours in 4.2% with tirofiban versus 13.2% with aspirin, adjusted RR 0.32; 95% CI 0.16 to 0.65; P=0.002, but did not show a statistically significant 90-day mRS shift.⁵
• Aetiology matters: RESCUE BT in large vessel occlusion stroke before thrombectomy did not show improved disability and had symptomatic intracranial haemorrhage 9.7% with tirofiban versus 6.4% with placebo; a cardioembolic RESCUE BT analysis found no disability benefit and increased symptomatic intracranial haemorrhage, supporting INSTANT’s exclusion of cardioembolism and visible LVO/MVO.⁸⁹
• Meta-analytic context: A 2026 RCT meta-analysis of early tirofiban after thrombolysis, with searches to August 2025 and therefore not including INSTANT, found no significant difference in excellent outcome, RR 2.72; 95% CI 0.26 to 27.97, no significant mortality difference, RR 1.07; 95% CI 0.55 to 2.09, and no significant symptomatic intracranial haemorrhage difference, RR 1.74; 95% CI 0.41 to 7.42; INSTANT therefore strengthens but does not close the evidence gap.¹⁰
• Minor stroke and bleeding context: PRISMS reported symptomatic intracranial haemorrhage of 3.2% in alteplase-treated minor nondisabling stroke; comparison with INSTANT is indirect because INSTANT enrolled a different, post-tenecteplase inadequate-response phenotype and excluded patients with NIHSS <4.¹¹

Summary

• INSTANT randomised 359 selected patients with acute ischaemic stroke, inadequate clinical response 4–24 hours after tenecteplase, no large/medium vessel occlusion, and no cardioembolic source.
• Tirofiban increased 90-day mRS 0–1 from 52.2% to 63.8%, RR 1.22; 95% CI 1.02 to 1.46; P=0.03, with an NNT of 8.7.
• The efficacy signal was not robust across all analyses: adjusted RR 1.17; 95% CI 0.98 to 1.41; P=0.08, and centre-clustered GEE sensitivity P=0.06.
• Symptomatic intracranial haemorrhage was uncommon, 0.9% versus 0%, but the single event was fatal and safety imaging was incomplete.
• The trial is best interpreted as an important, hypothesis-strengthening precision-stroke trial, not definitive evidence for routine tirofiban after thrombolysis.

Overall Takeaway

INSTANT is an important contemporary RCT because it tests a biologically coherent rescue strategy after tenecteplase in a carefully selected stroke population. It is not yet a definitive practice-changing landmark: the effect is clinically promising, but statistically fragile, safety is underpowered, and generalisability is narrow.

Bibliography

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