The effect of intravenous interleukin-1 receptor antagonist on inflammatory mediators in cerebrospinal fluid after subarachnoid haemorrhage: a phase II randomised controlled trial
© Singh et al.; licensee BioMed Central Ltd. 2014
Received: 7 November 2013
Accepted: 17 December 2013
Published: 3 January 2014
Interleukin-1 (IL-1) is a key mediator of ischaemic brain injury induced by stroke and subarachnoid haemorrhage (SAH). IL-1 receptor antagonist (IL-1Ra) limits brain injury in experimental stroke and reduces plasma inflammatory mediators associated with poor outcome in ischaemic stroke patients. Intravenous (IV) IL-1Ra crosses the blood–brain barrier (BBB) in patients with SAH, to achieve cerebrospinal fluid (CSF) concentrations that are neuroprotective in rats.
A small phase II, double-blind, randomised controlled study was carried out across two UK neurosurgical centres with the aim of recruiting 32 patients. Adult patients with aneurysmal SAH, requiring external ventricular drainage (EVD) within 72 hours of ictus, were eligible. Patients were randomised to receive IL-1Ra (500 mg bolus, then a 10 mg/kg/hr infusion for 24 hours) or placebo. Serial samples of CSF and plasma were taken and analysed for inflammatory mediators, with change in CSF IL-6 between 6 and 24 hours as the primary outcome measure.
Six patients received IL-1Ra and seven received placebo. Concentrations of IL-6 in CSF and plasma were reduced by one standard deviation in the IL-1Ra group compared to the placebo group, between 6 and 24 hours, as predicted by the power calculation. This did not reach statistical significance (P = 0.08 and P = 0.06, respectively), since recruitment did not reach the target figure of 32. No adverse or serious adverse events reported were attributable to IL-1Ra.
IL-1Ra appears safe in SAH patients. The concentration of IL-6 was lowered to the degree expected, in both CSF and plasma for patients treated with IL-1Ra.
Aneurysmal subarachnoid haemorrhage (SAH) accounts for 5% of all strokes, but 25% of stroke-related mortality [1, 2]. Of those who survive the initial bleed, up to one-third may develop delayed cerebral ischaemia (DCI) . The mechanism of DCI remains unclear, but vasospasm and inflammation may be involved [4–6] in its progression to a worse outcome, with nimodipine having only a modest impact . Inflammation is a key process in cerebral ischaemia  and is driven by the cytokine interleukin-1 (IL-1). IL-1 upregulates the expression of IL-6, which triggers local inflammation and activation of the systemic acute phase response. IL-6 concentrations are elevated in the cerebrospinal fluid (CSF) of patients after SAH and higher concentrations of CSF IL-6 are seen in patients with worse clinical outcomes .
The naturally occurring selective antagonist of IL-1, IL-1 receptor antagonist (IL-1Ra) blocks all known actions of IL-1 and is a promising candidate as a treatment for cerebral ischaemia [10, 11]. Intracerebroventricular administration of IL-1Ra protects against diverse forms of experimentally induced brain injury in rodents, including ischaemia [12, 13], trauma , and perinatal hypoxia . In experimental cerebral ischaemia, IL-1Ra is protective when administered intravenously (IV)  or subcutaneously (SC) , and when administered up to 3 hours after onset . Intravenously administered IL-1Ra crosses the blood–brain barrier (BBB) and can be found in CSF of SAH patients at concentrations that are effective in limiting brain injury in rodents . In ischaemic stroke patients, IV IL-1Ra reduces peripheral inflammation (plasma IL-6, white cell count, and C-reactive protein, CRP) measured 7 days after stroke .
Up to 25% of patients with SAH require temporary external CSF drainage  to treat hydrocephalus. This offers a unique opportunity to study changes in brain physiology and pharmacology in patients, where these are reflected in CSF. Using this approach, we have shown that IV IL-1Ra crosses the BBB  and that experimentally therapeutic CSF concentrations can be achieved within 45 minutes of IV administration .
The aim of this study was to determine whether IV IL-1Ra reduces the concentration of mediators of inflammatory activity in the circulation and CSF.
Patient inclusion criteria and data collection
Eligibility criteria for study patients
Aged 18 years or above.
Known or suspected infection at the time of consideration for the study.
Patients with confirmed aneurysmal SAH who have had an EVD inserted as part of their clinical care, that is expected to remain in situ for more than 48 hours.
Known allergy to Escherichia coli or any of the constituents of the study medication as established from the patient themselves, reliable representative, or clinical records.
IL-1Ra or placebo can be administered within 72 hours from ictus.
Previous or existing treatment with IL-1Ra.
Patients are likely to remain resident within the study centre for the next 7 days.
Previous or current treatment with medication suspected of interacting with IL-1Ra, such as TNF-α inhibitors.
Normal renal function (serum creatinine <177 μmol L-1).
Known to have participated in a clinical trial of an investigational agent or device in the previous 30 days or for the period determined by the protocol of the study the patient has taken part in.
Willing and able to give informed consent or consent available from a patient’s personal representative (usually the next of kin) for study inclusion including agreement in principle to receive study intervention and undergo all study assessments.
Known pregnancy or breast-feeding.
Clinically significant concurrent medical condition which, at the CI’s (or designee’s) discretion, could affect the safety, tolerability, or efficacy in this study or would interfere with participation, administration of study treatment, or assessment of outcomes. For example, pre-existing malignancy.
Previous inclusion in the current study.
Inability or unwillingness of patient or patient’s personal representative to give written informed consent.
Informed consent was obtained from the patient or the patient’s representative. Demographic and clinical details were recorded. SAH severity was graded clinically using the World Federation of Neurosurgical Societies (WFNS) score  and radiologically using the Fisher grade . The randomisation service was provided by an independent third-party professional company, Sealed Envelope (London, UK; http://www.sealedenvelope.com). After consent the patient was randomised, baseline clinical assessment was performed, and CSF (2 mL) and plasma (5 mL) samples were taken. This was immediately followed by administration of placebo or IL-1Ra. IL-1Ra was injected as Kineret, a recombinant, non-glycosylated form of human IL-1Ra . An IV bolus of 500 mg, given over 1 minute, was immediately followed by a 10 mg/kg/hr infusion over 24 hours. CSF and plasma samples were taken at 6, 12, 24 (end of infusion), 36, 48, and 72 hours. Adverse event reporting was carried out according to Medicines and Healthcare Products Regulatory Agency (MHRA) and sponsor regulations.
Inter-assay CV range (QC concentration range)
Inter-assay CV range (QC concentration range)
8.2 to 3.2 (360 to 10,009 pg/mL)
Same assay as for plasma
9.0 to 4.2 (25 to 366 pg/mL)
6.6 to 9.2 (20 to 800 pg/mL)
10.3 to 6.3 (17.5 to 146 pg/mL)
30.3 to 10.9 (1.3 to 10.9 pg/mL)
5.9 to 2 (41 to 322 pg/mL)
7.1 to 2.6 (213 to 1,229 pg/mL)
7.9 to 16 (109 to 975 pg/mL)
8.9 to 15.8 (185 to 9,152 pg/mL)
10.3 to 6.26 (7.5 to 146 pg/mL)
10.6 to 5.5 (5.16 to 232 pg/mL)
19.5 to 11.3 (207 to 1,759 pg/mL)
(19 to 6.5 (9,303 to 11,275 pg/mL)
6.7 to 7.0 (16.8 to 159 pg/mL)
25 to 15.8 (4.3 to 28.1 pg/mL)
14.8 to 1 (9.2 to 97 mg/L)
The primary outcome measure was the area under the curve (AUC) for CSF IL-6 concentration, between 6 and 24 hours from the start of the infusion, adjusted for baseline. Values were log-transformed before analysis and adjustment was achieved by subtraction of the baseline value from values at all time points prior to calculation of AUC. Comparisons between the two treatment groups were made using Student’s t-test. Similar analyses were carried out for IL-1α, IL-1β, IL-8, IL-10, MCP-1, TNF-α, and CRP. Statistical analyses were performed with Stata version 12 (StataCorp, College Station, TX, USA). The target sample size was intended to include 16 participants per treatment group, including replacement of participants in whom it was not possible to obtain all samples up to 24 hours from the start of infusion. This sample size gave 80% power at the 5% significance level to detect differences of one standard deviation in outcomes between treatment groups, similar to that seen for ischaemic stroke patients in our previous study .
Recruitment and baseline characteristics
Characteristics of each treatment group
All patients (n = 13a)
Placebo (n = 7)
IL-1Ra (n = 6)
Mean age (range) (years)
54 (40 to 69)
50 (42 to 61)
58 (40 to 69)
Adverse and serious adverse events
Raised ICP; hypotensiona
Desaturation; cardiac arrhythmia; meningitis
Chest sepsis; focal seizures cardiac arrhythmia; increased urine output; increased CRPa
IV line infection; chest infection; focal seizure
Acute agitationa; pyrexia of unknown origina
Changes in plasma and CSF IL-6 following IL-1Ra administration
Changes in other measures of inflammation
Analysis of baseline-adjusted AUC from 6 to 24 hours for all outcome measures
12.8 (−2.1 to 27.7)
18.6 (−0.6 to 37.7)
7.1 (−5.4 to 19.5)
6.7 (−4.9 to 18.3)
1.8 (−8.6 to 12.2)
17.6 (4.3 to 30.9)
5.5 (−3.9 to 15.0)
−0.3 (−14.0 to 13.3)
−1.1 (−10.3 to 8.1)
GOS scores for patients at 6 months after SAH
Good (GOS 4 to 5)
Poor (GOS 1 to 3)
We observed that IV IL-1Ra reduced the concentration of IL-6 in CSF and plasma to the extent predicted, although the numbers of participants it was possible to recruit meant that statistical significance could not be achieved. This provides evidence that peripherally administered IL-1Ra has a biological effect within the central nervous system (CNS) after acute brain injury in humans. It is not certain whether IL-6 itself may be causally involved in contributing to pathology, but both peripheral and central IL-6 have been shown to be associated with outcome [24, 25]. However, here we have simply used it as a biological marker to monitor the level of inflammation that results after SAH. Although we were interested in how other markers might respond, we chose IL-6 at the outset as the primary marker, to reduce the difficulty of interpreting P values from multiple statistical analyses. As such, the data support the rationale for developing IL-1Ra as a therapy to attenuate the neuroinflammatory response, and possibly the development of DCI, after SAH.
The higher IL-6 concentrations in CSF, compared to plasma, are consistent with previous studies , and indicate that changes in CSF do not result from IL-1Ra altering peripheral IL-6 production before translocation to the CNS. We had anticipated a lag in response to IL-1Ra infusion, which is why the analysis is from 6 hours. However, as shown by data for those patients where data was available beyond 24 hours, the effect almost certainly continues beyond this time point. Although sample analysis at later times may demonstrate a greater difference, we are reluctant to attribute significance on the basis of post-hoc analysis, with missing data. Concentrations of CSF and plasma IL-1β and TNF were very low or undetectable, as also found previously . The other cytokines, IL-8, IL-10, and MCP-1 showed differences in the direction expected if IL-1Ra was acting in an anti-inflammatory manner but, as for IL-6, did not reach statistical significance. Consistent with IL-6 as the major driver of the CRP response, plasma CRP concentrations fell in the treatment group, relative to placebo, but only after the primary analysis period.
The study was limited by the small number of patients, mainly due to difficulties of recruiting from a cohort of critically unwell patients. The treatment arm also had patients with a higher WFNS, and started with a higher median IL-6 value. This may have mitigated against observing a treatment effect as more severe implies a bigger drive to counter with therapeutic intervention. The age and gender of patients, and aneurysm location, was however representative of the SAH population as a whole. In keeping with previous clinical studies involving critically unwell patients, IV IL-1Ra was found to be safe and no reported adverse events could be attributed to the drug.
IL-1Ra is unique as a candidate for treatment of the inflammatory response that is induced by SAH and there are extensive preclinical and clinical pharmacokinetic data supporting the role of IL-1Ra as a neuroprotective agent . This contrasts with other candidate treatments in SAH, such as clazosentan and magnesium sulphate (MgSO4), where the lack of patient pharmacokinetic and pharmacodynamic data may partly explain the recent failure of phase III clinical trials [27, 28].
Reduction of IL-6 concentration in CSF of patients with SAH indicates that IV administered IL-1Ra may act within the CNS directly or indirectly to attenuate the early inflammatory response to SAH. This suggests it is a promising therapeutic option for the prevention of inflammation and DCI in SAH. Larger trials are required in order to confirm its efficacy and impact on clinical outcome.
Area under the curve: BBB, Blood–brain barrier
Central nervous system
Coefficient of variation
Delayed cerebral ischaemia
Enzyme-linked immunosorbent assay
External ventricular drain
Glasgow outcome score
High performance ELISA
Interleukin-1 receptor antagonist
Monocyte chemoattractant protein-1
Medicines and healthcare products regulatory agency
National Institute for Biological Standards and Control
Tumour necrosis factor
World federation of neurosurgical societies.
This study was funded by the Medical Research Council and with additional salary support from Salford Royal NHS Foundation Trust. Amgen Inc (Thousand Oaks, CA, USA) kindly provided the placebo and drug for the study. PJH is supported by an Academy of Medical Sciences/Health Foundation Senior Surgical Scientist Fellowship.
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