Background
Therapies to prevent organ dysfunction in sepsis and septic shock are limited [
1]. During sepsis, early and appropriate antibiotic administration to counteract infection is the cornerstone of treatment; additionally, current therapeutic strategies include supportive therapy mainly based on hemodynamic stabilization and, when organ dysfunction occurs, organ support [
2]. No specific treatments to prevent or recover renal injury in septic patients are available to date and renal replacement therapy (RRT) is required when renal function is severely compromised [
3]. Moreover, the use of blood purification techniques, including high-volume hemofiltration, polymyxin B hemoperfusion, and cytokines absorber devices, has not shown significant benefits to support their routine use in clinical practice and they are not recommended by the Surviving Sepsis Campaign Guidelines [
4‐
7].
The cytokine storm induced by the underlying infection can rapidly lead to multi-organ failure such as cardiovascular and respiratory systems, liver or kidney dysfunctions at advanced stages [
8]. The cytokine storm is an overwhelming reaction of the innate immune system following a bacterial or viral infection, which induces significant impairment of lipid and lipoprotein homeostasis in particular the high-density lipoprotein (HDL) [
9]. HDL complexes in addition to their well-characterized reverse cholesterol transport from peripheral cells to the liver, display anti-inflammatory, antioxidant, and antithrombotic properties [
10]. They regulate the function and integrity of endothelial cells, interfering with inflammatory and apoptotic stimuli [
11]. Furthermore, HDL plays an essential role in shaping immune response and may have a direct anti-infectious effect, thereby decreasing infection severity [
9,
12,
13]. Low HDL-cholesterol (HDL-C) and apolipoprotein A-I (ApoA-I) levels during the initial phase of sepsis is strongly associated with 30-day mortality and prolonged ICU stay, suggesting the ability of HDL to reduce TNF-alpha production induced by LPS [
14]. Recently, a prospective observational study including 205 septic patients admitted in ICU reported that an HDL-C level at ICU admission < 0.4 mmol/l was associated with increased mortality at day 28 [
15]. In the case of viral infection, such as SARS-CoV-2 infection, a significant decrease in HDL-C and ApoA-I were reported [
16], and low levels of ApoA-I were associated with a poor prognosis for recovery [
17]. This phenomenon can be generalized to sepsis regardless of infection source [
13‐
15]. Interestingly, a recent publication described ApoA-I as the only lipid biomarker associated with long-term survival (1 year) in patients with surgical sepsis [
18]. Altogether, one can hypothesize that the rapid restoration of small functional HDL particles containing ApoA-I in critically ill patients could have beneficial effects.
Several experimental studies have been performed in pre-clinical models of sepsis. Reconstituted HDL (CSL-111) administration in a mouse model of sepsis by cecal ligation and puncture or intraperitoneal injection of
E. coli or
Pseudomonas aeruginosa pneumonia improved overall survival, reducing the inflammatory burden and decreasing bacterial count [
19]. Similarly, the supplementation of a synthetic HDL (sHDL ETC-642) improved organ dysfunction and 7-day survival in septic mice, not only by neutralizing LPS, but also by a significant suppression of TLR4-NF-ĸB signaling and pro-inflammatory cytokine production [
20]. To date, there have been no significant experiences with HDL administration in the clinical setting in sepsis. In humans, the effect of infused synthetic reconstituted HDL in volunteers challenged with a sub-pathologic dose of LPS showed a decrease of cytokines such as IL-6 [
21,
22]. This observation was attributed mainly to the scavenger effect of the HDL [
21,
22]. Cases of patients with SARS-CoV-2 infection admitted to the ICU receiving short-term treatment (q12h for 1–2 days) with a synthetic HDL composed of a human recombinant ApoA-I and phospholipids, CER-001, were reported [
23,
24]. In all cases, CER-001 was able to rapidly decrease the level of different cytokines with commensurate improvement of the patients’ clinical conditions [
23]. These observations suggest that ApoA-I-complexes could have effects other than a scavenger effect per se and that there is some rationale to treat other patients such as septic patients with ApoA-I-complexes. To this purpose, we first studied the in vitro effect of CER-001 on peripheral blood mononuclear cell (PBMC) and endothelial cells, and based on the results obtained, we tested the effect of CER-001 in a swine model of LPS-induced acute kidney injury (AKI) and in an open-label Phase 2a pilot clinical trial. Our hypothesis was that CER-001 could provide anti-inflammatory and endothelial-protective effects, preserving kidney and liver integrity and function, reducing the risk of AKI as well as improving clinical outcomes.
Discussion
This translational study examined the potential role of an engineered HDL-mimetic, CER-001, as a novel adjuvant therapy in sepsis. Our findings demonstrated significant scavenger effects of CER-001 on endotoxins through the bile, as well as its ability to modulate the cytokine storm, reduce endothelial dysfunction, and prevent organ damage. Notably, we conducted a proof-of-concept clinical study that confirmed the pleiotropic effects of CER-001 in septic patients, in reducing renal damage, the need for organ support and ICU stay, emphasizing the potential clinical significance of this therapeutic approach.
Current treatment protocols for septic patients are based on hemodynamic resuscitation, supportive therapy, and adequate antibiotic therapy [
41]. However, in most critically ill patients, these measures are not enough to prevent sepsis-related organ dysfunction and the onset of AKI. Although the hemodynamic instability and kidney hypoperfusion are historically considered the main mechanism involved, multiple experimental studies have highlighted the detrimental effects of an uncontrolled systemic inflammatory response in the pathophysiology of sepsis-associated AKI [
42,
43]. Additionally, this systemic inflammation is correlated with alterations in lipid and lipoprotein metabolism [
9]. Indeed, clinical observational studies report that decreased amount of HDL-C in septic patients is positively correlated with the severity of the illness [
44]. Besides their well-documented role in reverse cholesterol transport (RCT), HDLs are involved in modulation of endothelial dysfunction, oxidative stress, inflammation, immune response, and coagulation activity [
45]. Previous studies using reconstituted HDL and HDL-mimetic peptides have shown their ability to reduce mortality and attenuate the pro-inflammatory response in endotoxemia and sepsis [
43]. Interestingly, the compelling evidence demonstrating the remarkable capacity of CER-001, an HDL-mimetic lipoprotein containing recombinant human ApoA-I, to enhance cholesterol mobilization, promote reverse cholesterol transport, and exhibit in vitro anti-inflammatory properties in an animal model of atherosclerosis suggests a strong potential for its efficacy in the treatment of septic conditions [
46].
In the present animal study, we demonstrate the targeted anti-inflammatory effects of CER-001 at the renal and hepatic levels as well as at systemic circulatory system. The potential mechanism of action is due to CER-001’s capacity on the one hand to decrease the inflammatory cytokines and on the other hand to counteract the action of LPS. Our pre-clinical results suggest that CER-001 enhances the transport of LPS to the liver and promotes its elimination into the bile, indirectly attenuating inflammation. Interestingly, LPS and ApoA-I levels increased in bile samples of CER-001-treated animals. In addition, the pharmacokinetics of the human ApoA-I measured in the swine sera of both treated groups was consistent with the decreased amount of LPS, mediated by CER-001 treatment.
Furthermore, we demonstrated the ability of CER-001 to ameliorate systemic endothelial dysfunction and induced an increase in average survival time. The subsequent activation of endothelial cells upregulates the expression of different adhesion molecules, such as s-ICAM-1, s-VCAM-1, and selectins, that enhance leukocyte migration and homing, amplifying innate and adaptative immune response [
47]. Accordingly, we observed an increased release of soluble adhesion molecules, s-ICAM-1 and s-VCAM-1, in sera of endotoxemic pigs and septic patients. Moreover, our analyses demonstrated a dose-dependent inhibition of these mediators in CER-001-treated subjects. In addition, our data showed that CER-001 treatment reduced serum levels of pro-inflammatory cytokines, such as TNF-α, MCP-1, and IL-6, both in endotoxemic pigs and in CER-001-treated patients. This observation is encouraging and suggests that CER-001, by decreasing LPS levels and interacting with the immune system through ApoA-I, limits the cytokine cascade and provides endothelial protection. Remarkably, we also found decreased levels of sTREM-1 after CER-001 treatment in septic patients that could be associated with increased survival and ameliorated prognosis. sTREM-1 has been suggested as a strong predictor of poor prognosis and mortality in septic patients [
48]. Persistently high sTREM-1 levels during the first days following ICU admission are associated with mortality in human septic shock [
49]. Moreover, CER-001 treatment reduced complement activation, demonstrating effectiveness in regulating the innate immune response.
Since HDL-C levels significantly declined in severe sepsis and septic shock, several studies have evaluated the impact of HDL in worsening renal function as a potential predictive biomarker and therapeutic target. In line with these findings, our study highlights the critical role of CER-001 in recovering renal function and urine output in endotoxemic animals. These results are consistent with the clinical data that reported a low risk for the onset and/or progression to severe AKI (Stage 2 or 3) among CER-001-treated patients.
Liver dysfunction is a fairly common manifestation during sepsis and it is strongly associated with mortality [
50]. The relationship between HDL-C and sepsis-associated liver dysfunction has been previously studied, as HDL-C levels are typically lower in patients with liver dysfunction, although HDL-C concentration did not correlate with hepatic dysfunction markers and overall mortality [
51]. The pathophysiology of such relationship is poorly understood; while it could be suspected to be a decreased hepatic synthesis of HDL during sepsis, an increased HDL elimination should be considered [
51]. In this study, we observed early manifestations of hepatic dysfunction which included increased ALT levels and histological changes. Remarkably, hepatic damage was resolved by CER-001 infusion, underscoring the hepatoprotective effects of this drug, thereby preserving its physiological function.
Finally, the strong observed effect of CER-001 on the cytokine cascade and endothelial dysfunction led us to evaluate its potential impact on clinical outcomes, although this small pilot clinical trial could only detect trends in such clinical parameters. Interestingly, the observed mortality rates for SOC are consistent with a recent publication of a meta-analysis examining mortality from sepsis in hospitalized patients (30.1%) and in the subset of ICU-treated patients (40.4%) in the European region (as defined by the WHO) [
52,
53]. We reported a more rapid improvement of clinical conditions among patients who received CER-001, as evidenced by a reduced length of ICU stay and need for organ support during the 30-day study period, as compared to SOC patients. These results need to be confirmed by a larger clinical trial examining these endpoints more rigorously.
Together, the present study has several strengths. We demonstrated the safety and efficacy of a novel HDL-mimetic compound in sepsis using a translational approach. We provide valuable insights into the pleiotropic effects of HDL in a heterogeneous population of septic patients. However, we acknowledge some limitations in our research. The application of pre-clinical results to the clinical setting is always questionable due to the difficulty of simulating the complexities of human disease. Another limitation is the open-label study design of the clinical study. Additionally, the sample size of our clinical study is limited as it was a proof-of-concept study, warranting caution in the interpretation of the results.
The findings of our research have profound implications for the management of sepsis and other critical illnesses characterized by inflammation and organ failure. Beyond sepsis, the multifaceted therapeutic potential of CER-001 may extend to other high-mortality clinical indications marked by inflammation. Notably, CER-001’s pleiotropic effects could hold promise in mitigating the severity and mortality of COVID-19 infection, as well as other critical illnesses such as acute respiratory distress syndrome (ARDS) and severe bacterial and viral infections. The ability to counteract inflammation, modulate the immune response, and protect endothelial cells makes it a potential therapeutic option worth exploring further. Considering the economic burden and high mortality associated with sepsis, the novel therapeutic approach related by CER-001 offers hope for addressing unmet medical needs in critical care.
Therefore, based on the positive outcomes of the human proof-of-concept trial, we will design and conduct a larger phase 2b/3 study. Phase 2b will be designed to further refine the dose and dose regimen. Phase 3 will allow us to demonstrate the clinical benefits of this promising therapy for patients, and to determine whether there is an economic impact for the treatment of sepsis.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.