Benefit of Clarithromycin in Patients With Severe Infections Through Modulation of the Immune System

Sepsis is a condition with actually rising incidence, estimated around 19 cases per 1000 hospitalizations per year in academic hospitals in USA and similar trends in Europe. It is associated with unacceptably high early (in-hospital) mortality of 40- 50%. Current guidelines promote best practice by early recognition and management with timely antibiotic administration, fluids, vasopressors and early identification/ control of infection source. However, in spite of adherence to more intensive and costly protocols of early goal-directed therapy, no further decrease in mortality is achieved. Syndromic approaches on sepsis and therapies targeting immune modulation are under evaluation and failures may partly be due to incomplete understanding of underlying pathophysiological mechanisms and immunological phases (pro and anti-inflammatory) of sepsis.

Macrolides, such as clarithromycin or azithromycin have been shown beneficial in reducing Chronic Obstructive Pulmonary Disease exacerbations (OR 0.55; 95% Confidence Intervals [CI] 0.39-0.77; p<0.001) partly through anti-inflammatory properties. Besides, when added to a beta-lactam regimen in community-acquired pneumonia, macrolide therapy was associated with reduced mortality risk (OR 0.67; 95% CI 0.61-0.73; p<0.001) in a recent meta- analysis of observational studies including 42942 patients. An immunomodulatory effect of macrolides, beyond their antimicrobial action may explain these findings.

Clarithromycin as adjunctive treatment to standard antibiotic therapy has been used by our group in two previous large-scale multi-center Randomised Controlled Trials (RCTs) conducted in Greece after approval from the Greek regulatory authorities. The first RCT studied 200 patients with sepsis due to Ventilator Associated Pneumonia (VAP) ( www.clinicaltrials.gov NCT00297674). Identified pathogens mainly included gram- negative bacteria i.e. Acinetobacter baumannii and Pseudomonas aeruginosa that do not belong to the usual antimicrobial spectrum of macrolides. Although 28-day mortality in both arms was similar, patients assigned to the clarithromycin arm experienced earlier weaning from mechanical ventilation and more rapid resolution of VAP, compared to the placebo arm. In the subgroup of patients with septic shock and multiple organ dysfunction syndrome (MODS), probability of sepsis-related death was significantly lower (OR 3.78 vs 19; p = 0.043). Serious adverse events (SAEs) occurred in 3 (3%) clarithromycin-treated patients, with no clear causative link with the study drug in 2 out of 3 cases. Furthermore, hospitalization costs associated clarithromycin use were significantly reduced (by 7000 euros/ patient) compared to the placebo arm.

The second multi-center RCT compared the efficacy of clarithromycin versus placebo added to standard antibiotic therapy in patients with gram-negative sepsis caused by acute pyelonephritis, intra-abdominal infections and primary gram- negative bacteremia; 600 patients were included (www.clinicaltrials.gov NCT01223690). Overall mortality at 28 days in both arms did not differ, but probability of death due to septic shock and MODS was shown once more lower in the clarithromycin-treated group (OR 3.58 vs 6.21; p = 0.036). Interestingly, survival benefit from clarithromycin was even greater in those patients suffering from adult respiratory distress syndrome (ARDS). SAEs were described in 2 (0.7%) patients treated with clarithromycin, while its use was associated with saving of a median of 1000 euros/ hospitalized patient.

Immunomodulatory effects of clarithromycin in sepsis are not yet elucidated. The analysis of circulating monocytes and of circulating cytokines of patients participating in the first RCT showed that treatment with clarithromycin was associated with a decline in Interleukin-10 (IL-10)/ Tumor Necrosis Factor-α (TNF-α) ratio, greater apoptosis of monocytes, enhanced antigen presentation capacity of monocytes, as well as improved capacity of monocytes for cytokine production suggesting an effect consistent with reversal of sepsis-induced immunosuppression. These findings in conjunction with evidence generated from in vitro and animal experiments suggest modulation of the immune response as the mechanism of action of clarithromycin.

In both RCTs, clarithromycin was administered intravenously at a dose of 1g as continuous one-hour intravenous infusion for three or four days. The drug was safe, well tolerated and cost-effective. However, benefit from treatment in both RCTs was shown only after sub-group analysis of the sub-group of patients with respiratory dysfunction and not when analysis comprised the entire study population. As a consequence, in order to consolidate the benefit of clarithromycin among patients with sepsis and respiratory dysfunction, the INCLASS study is a RCT designed to target a patient population with sepsis and respiratory dysfunction. It also targets a population with infections likely to be caused by Gram-negative bacteria that do not belong to the antimicrobial spectrum of clarithromycin. The study's aims are to assess the effect on mortality associated with the use of clarithromycin as adjunctive treatment in the above setting, as well as to provide insight on different biomarkers modification during treatment, to propose a mechanism of action of this treatment and to perform a cost analysis.