Efficacy and safety of Y-3 intracalvariosseous injection versus intravenous injection in the treatment of acute large hemispheric infarction (SOLUTION-2): rationale and design of a multicentre, prospective, randomised, open-label, blind endpoint (PROBE) trial

Abstract

Rationale

The blood–brain barrier (BBB) largely restricts the efficacy of neuroprotectants, which is an important approach in treating large hemispheric infarction (LHI). In this study, we harnessed intracalvariosseous (ICO) injection to bypass the BBB and facilitate drug delivery.

Aim

To compare the efficacy and safety of ICO injection versus intravenous injection in the treatment of acute LHI within 24 hours of disease onset.

Methods and design

The efficacy and safety of Y-3 ICO injection versus intravenous injection in the treatment of acute LHI (SOLUTION-2) is a multicentre, prospective, randomised, open-label, blind endpoint trial. 134 patients with acute LHI from more than six centres will be enrolled and randomised in the trial to receive ICO or intravenous injection of Y-3 in a 1:1 ratio.

Study outcomes

The primary efficacy outcome is the proportion of patients with a modified Rankin Scale score of 0–3 at 90 days after symptom onset. Primary safety outcomes include infection events related to ICO injection procedures.

Discussion

Results from the SOLUTION-2 trial will contribute to the understanding of the efficacy and safety of the Y-3 ICO injection in patients with LHI.

Trial registry

The efficacy and safety of Y-3 ICO injection versus intravenous injection in the treatment of acute LHI (SOLUTION-2).

URL

https://clinicaltrials.gov/study/NCT06374667?cond=SOLUTION-2&intr=y-3&rank=1.

Trial registration number

NCT06374667.

WHAT IS ALREADY KNOWN ON THIS TOPIC.

WHAT THIS STUDY ADDS

• Harnessing the natural pathway connecting cranial bone marrow, dura and perivascular space which bypasses BBB, we intended to evaluate the feasibility and safety of intracalvariosseous (ICO) injection in humans. We also sought to assess the efficacy of ICO injection compared with intravenous injection using Y-3 in the treatment of LHI.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• ICO injection is a promising drug delivery alternative that might decrease required drug dosage and increase drug transportation into the cerebral parenchyma. The SOLUTION-2 trial will hopefully clarify the efficacy and safety of the new central nervous system drug delivery method in patients with LHI.

Introduction and rationale

Large hemispheric infarction (LHI) is an ischaemic stroke in the territory of the middle cerebral artery (MCA).^{1 2} It is characterised by oedema, increased intracranial pressure and mass effect and is challenged by limited therapeutic choices.³ Thrombolysis and endovascular therapy are accompanied by a high risk of reperfusion injury or unsuccessful or futile reperfusion in LHI.^{4 5} As the HAMLET trial (ISRCTN94237756) and pooled analysis suggested,^{6 7} decompressive craniectomy (DC) is the most favourable life-saving treatment for patients with malignant MCA infarction (mMCAI) or LHI, but it may lead to infection, severe tissue damage or other side effects. Neuroprotection is another attractive choice for the treatment of patients with LHI, whereas its efficacy is challenged by the low rate of recanalisation and inadequate drug delivery through the blood–brain barrier (BBB). Among all neuroprotectants, postsynaptic density protein-95 (PSD-95) inhibitors are considered the most promising cytoprotective drugs, which function by ameliorating neuronal excitotoxicity and secondary ischaemic damage.⁸ Thus, we used Y-3, a small molecule neuronal nitric oxide synthase/PSD-95 uncoupling agent approved by the Chinese National Medical Products Administration, in our trial.⁹ Moreover, as a dual-target drug, Y-3 also exhibits selective potentiation of α2-containing γ-aminobutyric acid type A receptors (GABA_ARs), an anxiolytic and antidepression target.¹⁰

In 2018, microchannels connecting the cranial bone marrow and dura were identified, which also acted as natural pathways circumventing the BBB.¹¹ Preclinical study demonstrated that the above microchannels could be used to deliver drugs into cerebral parenchyma through intracalvariosseous (ICO) injection.^{12 13}

In the previous study, we proved the feasibility and safety of ICO injection for the first time in patients with mMCAI in the ‘SOLUTION’ (Y-3 injection through skull bone marrow in the treatment of acute mMCAI) trial (NCT05849805). Including 20 participants with mMCAI, the SOLUTION trial demonstrated no safety events in the ICO injection group. Additionally, we exhibited a tendency towards a better functional outcome of the ICO injection group compared to the best medical treatment group alone. Moving forward, we intended to expand our sample size and designed an investigator-initiated trial, namely ‘SOLUTION-2’ (the efficacy and safety of Y-3 ICO injection bypassing BBB vs intravenous injection in the treatment of acute LHI) to further evaluate the feasibility and safety of ICO injection in humans. We also sought to assess the efficacy of ICO injection compared to intravenous injection using Y-3 in the treatment of LHI.

Methods

Study design

SOLUTION-2 is a multicentre, prospective, randomised, open-label, blind endpoint trial. Patients with acute LHI will be randomised in a 1:1 ratio to Y-3 ICO injection or Y-3 intravenous injection groups within 24 hours after symptom onset. They will be followed up for 90 days to evaluate the clinical outcomes, and another 9 months of follow-up will be scheduled for functional estimation and neuroimaging collection. All participants enrolled in this study will receive standard medical treatment and care. The implementation process is shown in figure 1.

Figure 1. Schematic of SOLUTION-2 design. *Clinical symptoms, signs and imaging are consistent with a cerebral infarction in the territory of the middle cerebral artery (MCA), which also meets the following characteristics: (a) NIHSS score between 16 and 32, with a sum score of item 5 (arm motor function) and item 6 (leg motor function) ≥6 and (b) imaging indicates the infarct core region: the lesion volume obtained from MRI diffusion weighted imaging (DWI) or the volume with cerebral blood flow (CBF) <30% from CT perfusion (CTP) is between 70 mL and 300 mL or the Alberta Stroke Program Early CT Score (ASPECTS) value between 0 and 6. In cases of inconsistent results, the investigator must consider all information (scanning time, the most appropriate imaging method for assessing infarct size, etc) to make a reasonable judgement and document it accordingly. †After reperfusion therapy, the NIHSS score shows no improvement or even deterioration, and the total score remains ≤32. ‡ Y-3 dosage of 32 µg/kg, administered once daily for 3 days; § Y-3 dosage of 40 mg + 250 mL of saline, administered once daily for 7 days. ICO, intracalvariosseous; LHI, large hemispheric infarction; NIHSS, National Institutes of Health Stroke Scale.

Patient population

Inclusion and exclusion criteria

Patients who meet the following criteria will be taken into consideration: aged 18–80 years with acute LHI with no limitation of gender; prestroke modified Rankin Scale (mRS) score ⩽1; administration can be completed within 24 hours of neurological symptoms’ onset; clinical signs are consistent with cerebral infarction in the territory of the MCA with the following characteristics: a National Institutes of Health Stroke Scale (NIHSS) score between 16 and 32 and a score of motor function (item 5 plus item 6) ≥6, an infarct-core volume between 70 mL and 300 mL or an Alberta Stroke Program Early CT Score value ≤6; if patients have received reperfusion therapy, the NIHSS score does not improve or even worsen after treatment, and the total score remains ≤32. The principal exclusion criteria encompass haemorrhagic stroke or haemorrhagic transformation with mass effect; severe cerebral herniation; ICO injection contraindications; significant abnormalities in liver function, renal function or cardiac function; life expectancy <3 months, pregnancy or other therapeutic conditions deemed ineligible for enrolment by the investigator. The comprehensive inclusion and exclusion criteria are delineated in box 1.

Box 1. Inclusion and exclusion criteria.

Inclusion criteria

18≤age≤80 years old, regardless of gender;

Prestroke modified Rankin Scale score ≤1;

Drug administration can be completed within 24 hours of the onset of neurological symptoms (the time of onset is defined as the time of the last normal presentation);

Clinical symptoms, signs and imaging are consistent with a cerebral infarction in the territory of the middle cerebral artery, which also meets the following characteristics:

NIHSS score between 16 and 32, with a sum score of item 5 (arm motor function) and item 6 (leg motor function) ≥6;

Imaging indicating an infarct core: lesion volume with an apparent diffusion coefficient value <620×10⁻⁶ mm²/s on diffusion-weighted imaging in MRI or a cerebral blood flow <30% volume between 70 mL and 300 mL on CT perfusion or an Alberta Stroke Program Early CT Score of 0–6. In cases of inconsistent findings, investigators are required to integrate all available information (eg, scan timing, optimal imaging method for infarct size assessment) to make a well-reasoned judgement, which must be documented;

If reperfusion therapy is performed, the NIHSS score did not improve or even worsen after treatment, and the total score remains ≤32;

The patient or their legal representative signs informed consent.

Exclusion criteria

Complications of other cerebrovascular diseases meet one of the following conditions:

Acute cerebral haemorrhage and subarachnoid haemorrhage;

Acute posterior circulation cerebral infarction or severe posterior circulation stenosis (>70%);

Bilateral infarcts as indicated by imaging;

Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification indicates intracranial arterial dissection, vasculitis, moyamoya disease or other aetiologies;

Haemorrhage transformation of the infarction area, with haematoma occupying ≥30% of the infarct region and showing significant mass effect;

Clinical signs of brain herniation, such as unilateral or bilateral pupil dilation and fixation; loss of consciousness due to cerebral oedema (NIHSS 1a>2 points) or other signs of uncontrollable vital instability;

Planned decompressive craniectomy prior to randomisation;

Refractory hypertension (systolic >200 mm Hg or diastolic >110 mm Hg) or hypotension (systolic <70 mm Hg or diastolic <50 mm Hg) is difficult to control with medication;

Abnormal blood glucose before randomisation (random venous blood glucose <2.8 mmol/L or >23 mmol/L);

Significant liver or kidney function insufficiency prior to randomisation;

*Severe liver function insufficiency was defined as serum alanine aminotransferase or aspartate aminotransferase >3 times the upper limit of normal. Significant renal insufficiency is defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² (eGFR calculated using the Chronic Kidney Disease Epidemiology Collaboration formula);

Acute ST-elevation myocardial infarction and/or decompensated heart failure (New York Heart Association class III or IV) within the past 3 months;

Contraindications for intracalvariosseous injection, such as skull fracture, skull infection, subdural/extrinsic haematoma, subcutaneous haematoma, scalp or subcutaneous infection in the last 3 months or imaging that indicates unclear skull bone marrow;

Investigator-determined bleeding tendencies unsuitable for the procedure, including but not limited to: platelet count <100×10⁹/L, haemophilia or other coagulopathies;

Severe or extremely severe anaemia at randomisation (haemoglobin <60 g/L);

Severe respiratory diseases (eg, severe chronic obstructive pulmonary disease, respiratory failure) requiring tracheal intubation, tracheostomy or mechanical ventilation;

Investigator-determined clinically significant infection, including severe localised or systemic infection;

Diagnosed with severe central nervous system degenerative diseases, such as Alzheimer’s disease, Parkinson’s disease or severe dementia of any cause or psychiatric disorders (eg, schizophrenia, depression);

Investigator-determined life expectancy of <3 months due to causes unrelated to the current condition, such as malignancy;

Known allergy to any component of investigational drugs or contrast agents;

Pregnant, breastfeeding or patients with potential or planned pregnancy;

Inability to comply with the trial protocol or follow-up requirements;

Other conditions deemed unsuitable for inclusion by the investigator (reasons for exclusion documented);

Participation in other interventional clinical trials.

NIHSS, National Institutes of Health Stroke Scale.

Randomisation

All patients with suspected acute LHI will undergo a non-contrast CT scan of the head (including bone window), along with CT perfusion imaging to obtain information regarding infarct volume and outer plate thickness of the skull. After rigorous checking of the inclusion and exclusion criteria, patients enrolled are assigned to the Y-3 ICO group or intravenous group at a 1:1 ratio randomly. The randomisation code has been obtained by the random-permuted fixed-size blocks methods from the Statistics and Data Centre at the China National Clinical Research Centre for Neurological Diseases.

Intervention

Eligible participants will be randomly assigned to the Y-3 ICO injection group or Y-3 intravenous injection group (40 mg per day for 7 days) within 24 hours after symptom onset. The ICO injection group will receive ICO injection of Y-3 at a dose of 32 µg/kg/day for 3 days.This dose is converted from a preclinical study exploring the optimal injection dose in a permanent MCA occlusion rat model¹³ using the body surface area method. Considering the patients’ tolerance to invasive procedures and the potential infection risk, we set the ICO injection frequency as one time per day for three consecutive days after randomisation. Patients in the intravenous injection group will receive Y-3 (40 mg/day) for 7 days, which is the optimal intravenous dosage used in the phase II clinical study of Y-3. All participants will receive active treatment according to the guidelines.

ICO injection protocol

Prior to the procedure, we will carefully review the patient’s head CT scan with bone window settings to measure the thickness of the external cortical layer and the medullary cavity, in order to estimate the required depth for the bone drilling. The drilling site for ICO injection is located at the parietal tubercle on the ipsilateral side of the infarction. The patient will be positioned in a lateral decubitus position, and then standard disinfection and sterile draping procedures will be performed. Following sedation and the administration of local anaesthesia, a 2-centimetre scalp incision will be made. A mastoid retractor is used to expose the cranial marrow cavity, where a 4 mm diameter drilling hole will be created in the outer plate of the skull to a depth of 1–2 mm on average, ensuring the intactness of the inner cranial plate. The efflux of cranial bone marrow and blood indicates successful penetration of the cranial outer plate. A 5-mL syringe pasted with 3–4 layers of hydrocolloid dressing on its top will be employed for the ICO injection of Y-3. The dressing will form a temporary sealing environment as it comes into contact with the cortical bone surrounding the injection site during the injection process, ensuring that the drug is fully delivered into the bone marrow cavity. The injection will be performed with a speed of 200 µL per second once daily. To prevent drug leakage after injection, the injection site will be sealed with bone wax. Skin will be sutured after the sealing process.

Efficacy outcomes

The primary efficacy outcome is the proportion of patients with favourable functional outcomes defined as an mRS score of 0–3, assessed at 90±7 days after the onset of symptoms.

Secondary efficacy outcomes include changes in core infarction volume at 8±1 days; the proportion of patients demonstrating an NIHSS score improvement ≥4 points at 14±1 days compared with baseline; the distribution of NIHSS at 8±1, 14±1 and 90±7 days; the distribution of mRS at 90±7 days; the incidence of combined adverse events and the rate of DC within 90±7 days. Further details and exploratory 12-month efficacy outcomes are provided in table 1.

Table 1. Secondary outcomes and exploratory 12-month efficacy outcomes.

Secondary outcomes

Changes in core infarct volume at 8±1 days. Comparison of NIHSS scores distribution at 8±1 days. Proportion of patients with NIHSS score improvement ≥4 points at 14±1 days compared with baseline. Comparison of NIHSS score distribution at 14±1 days. Comparison of mRS score distribution at 90±7 days. Comparison of NIHSS score distribution at 90±7 days. Comparison of depression scale score at 90±7 days. Proportion of patients undergoing decompressive craniectomy at 90±7 days. Proportion of adverse events at 90±7 days (mRS 4–5, decompressive craniectomy, vascular death).

Exploratory 12-month efficacy outcomes

Proportion of patients with mRS score of 0–3 at 12 months ±14 days. Comparison of mRS score distribution at 12 months ±14 days. Anterior circulation ASPECTS score at 12 months ±14 days. Changes in infarct volume at 12 months ±14 days compared with baseline.

ASPECTS, Alberta Stroke Early CT Score; mRS, modified Rankin Scale; NIHSS, National Institutes of Health Stroke Scale.

Safety outcomes

Safety outcomes include infection events related to ICO injection procedures, other infection events, symptomatic and asymptomatic intracranial haemorrhage, moderate to severe bleeding events defined by the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries () criteria¹⁴, abnormal liver function indicators, severe renal function abnormalities, mortality rate, incidence of fatal stroke, tracheal intubation/tracheostomy, invasive/non-invasive mechanical ventilation or other adverse events/serious adverse events.

Data Safety and Monitoring Board

The Data Safety and Monitoring Board (DSMB) convenes as specified in the protocol to oversee the trial’s progress and safety, providing regular reports to the committee. After each meeting, the DSMB issues written statements detailing any recommendations, which will be submitted to the Steering Committee.

Sample size estimates

The minimum sample size for this trial is determined by the expected minimum need for the trial, running costs and the hypothetical proportion of patients with acute LHI who improved their 90-day mRS scores to 0–3. The minimum sample size required for a clinically meaningful difference between the ICO injection group and the intravenous group is the main consideration for the sample size calculations—assuming a 25% improvement in the 90-day mRS to a score of 0–3 in the intravenous injection group and a 50% improvement in the mRS to a score of 0–3 in the ICO injection group, equivalent to a 25% improvement in the event rate, with a test level of a taken as 0.05, a certainty of 85%, and a projected 90-day loss to visit rate of 5%. Sample size estimation was performed using PASS 15 (NCSS, LLC), and it was expected that 67 individuals would be needed in the cranial administration group and 67 in the intravenous administration group, for a total sample size of 134 individuals.

Statistical analyses

All efficacy analysis will be based on the intention-to-treat principle, and safety analysis will be based on the safety data set, using adjudicated data from all the patients who had undergone treatment.

The generalised linear model will be used to evaluate the primary outcome, the proportion of mRS 0–3 to evaluate efficacy between ICO injection and intravenous injection group in 90 days, and relative risks and 95% CIs will be presented. For second efficacy outcomes, a generalised linear model or general linear model will be selected appropriately.

Safety analysis will be analysed using the safety data set. Safety indicators such as the incidence of infection events related to skull manipulation (such as skin infection, osteomyelitis or intracranial infection), symptomatic and asymptomatic intracranial haemorrhage, moderate to severe bleeding events defined by GUSTO bleeding classification, mortality and incidence of fatal stroke will be compared between groups by Cox proportional hazards models, and HRs and 95% CIs were calculated. Other infection events will be compared between groups by χ² test (or Fisher’s exact test). Adverse events will be described statistically, and the incidence of safety endpoints will be compared between the two groups. In addition to the mean comparison before and after treatment, the laboratory data will mainly analyse and list the specific conditions of the cases that are normal before treatment but abnormal after treatment.

Subgroup analyses will be evaluated in patients with large cerebral hemisphere infarcts to assess differences in safety and efficacy between the ICO injection group and the intravenous injection group in the following subgroups of the population: age, gender, time-to-treatment (≤12 hours vs >12 hours after symptoms onset), wake-up stroke, cumulative dominant hemisphere, degree of vascular reperfusion, DC, baseline NIHSS score, intravenous thrombolysis, endovascular treatment, baseline ASPECT score, baseline core infarct volume and TOAST classification.

Discussion

Traditionally, the cranium was viewed as a structure primarily responsible for protection and haematopoiesis. However, recent research has revealed that the skull plays a significant role not only in immune responses but also in combating brain ageing and maintaining intracranial homeostasis.^{15 16} The recent discovery of the skull-dura-glymphatic system pathway further implicates the drug delivery potential of intracranial injection, which bypasses the BBB. Successful central nervous system (CNS) drug delivery and development is challenged by the presence of the BBB.¹⁷ Traditionally, to achieve higher drug exposure in the brain, researchers may increase the overall drug dosage; however, this may at the same time add systemic cytotoxicity. Other recent studies have investigated non-invasive methods including focused ultrasound combined with microbubble technology to open the BBB transiently, nasal inhalation administration or nanotechnology to increase BBB penetration.¹⁸ However, the benefits of these techniques are limited by the low drug delivery efficiency or disturbance of the BBB integrity. By using ICO injections to bypass the BBB, we administered a drug dosage that was only 2.5% of the intravenous injection dosage yet achieved similar or even better outcomes.¹³ To facilitate the clinical translation of this technology, we designed a clinical practice protocol for ICO injections in patients, exploring the feasibility and safety of Y-3 ICO injection for patients with LHI. We also pioneered the application of this technique in the treatment of large hemisphere infarctions to assess its efficacy compared with intravenous injections.

As a novel technique, several key concerns remain to be considered, such as safety issues (penetration of the cranial bone plate, drug leakage, etc) or its influence on intracranial pressure. To solve the problems, we replaced the traditional drilling method with cranial bone grinding, which may prevent cranial bone plate perforation. In addition, the concern for drug leakage was addressed by covering the syringe tip with multiple layers of hydrocolloid dressing. Regarding the impact on intracranial pressure, it is worth noting that the injected drug volume into the cranial cavity is approximately 1 mL, which is rather small compared with the cerebrospinal fluid volume (approximately 150 mL in adults) or the cranial bone cavity volume. Therefore, its effect on intracranial pressure might be minimal, though future studies are warranted to fully investigate its influence.

Overall, ICO injection may be an encouraging drug delivery alternative compared with systemic delivery, particularly for drugs with low BBB penetration efficiency, high costs or severe systemic toxicity. SOLUTION-2 will hopefully clarify the efficacy and safety of the new CNS drug delivery method: ICO injection in patients with LHI.

Conclusion

In summary, the SOLUTION-2 trial will investigate the safety and efficacy of Y-3 ICO injection initiated within 24 hours in the treatment of LHI.

Data availability statement

Data sharing not applicable as no datasets generated and/or analysed for this study.