Interleukin-7 restores lymphocytes in septic shock: the IRIS-7 randomized clinical trial

Abstract

Background: A defining pathophysiologic feature of sepsis is profound apoptosis-induced death and depletion of CD4+ and CD8+ T cells. Interleukin-7 (IL-7) is an antiapoptotic common γ-chain cytokine that is essential for lymphocyte proliferation and survival. Clinical trials of IL-7 in over 390 oncologic and lymphopenic patients showed that IL-7 was safe, invariably increased CD4+ and CD8+ lymphocyte counts, and improved immunity.

Methods: We conducted a prospective, randomized, double-blind, placebo-controlled trial of recombinant human IL-7 (CYT107) in patients with septic shock and severe lymphopenia. Twenty-seven patients at academic sites in France and the United States received CYT107 or placebo for 4 weeks. Primary aims were to determine the safety of CYT107 in sepsis and its ability to reverse lymphopenia.

Results: CYT107 was well tolerated without evidence of inducing cytokine storm or worsening inflammation or organ dysfunction. CYT107 caused a 3- to 4-fold increase in absolute lymphocyte counts and in circulating CD4+ and CD8+ T cells that persisted for weeks after drug administration. CYT107 also increased T cell proliferation and activation.

Conclusions: This is the first trial of an immunoadjuvant therapy targeting defects in adaptive immunity in patients with sepsis. CYT107 reversed the marked loss of CD4+ and CD8+ immune effector cells, a hallmark of sepsis and a likely key mechanism in its morbidity and mortality. CYT107 represents a potential new way forward in the treatment of patients with sepsis by restoring adaptive immunity. Such immune-based therapy should be broadly protective against diverse pathogens including multidrug resistant bacteria that preferentially target patients with impaired immunity.

Trial registration: Trials registered at clinicaltrials.gov: NCT02640807 and NCT02797431.

Funding: Revimmune, NIH National Institute of General Medical Sciences GM44118.

Keywords: Immunology; T cells.

Figure 1. Trial enrollment details.

Details on patient enrollment, randomization, allocation, and follow-up and analysis are presented. Medical, Surgical, Neurosurgical, and Cardiothoracic Intensive Care Units were screened daily Monday through Friday for patients on antibiotics and vasopressors. After identifying patients in presumed septic shock, patients were further screened for inclusion and exclusion criteria as per the protocol.

Figure 2. CYT107 increases absolute lymphocyte counts.

(A) Patients were treated with 10 μg/kg CYT107, a recombinant human interleukin-7 (IL-7) using 2 different dosing regimens. Both CYT107-treated groups received CYT107 twice a week for the first week. Thereafter, one group was treated with CYT107 once a week (low frequency) while the second CYT107 treated group was treated with CYT107 twice a week (high frequency). Therapy with CYT107 was continued for a total of 4 weeks or until the patient was discharged from the hospital. The maximum number of doses of CYT107 that a patient could receive was 5 or 8 doses respectively for the low- and high-dose regimens of CYT107. All patients received injections twice a week. (B) The CYT107 treatment effect on average absolute lymphocyte counts (ALCs) was significant for both high- and low-frequency treatment regimens. The gray-shaded region represents the upper and lower limit of normal for ALCs. The CYT107 low-frequency group (red color) was greater than the placebo-treated group at days 15 and 42, and the CYT107 high-frequency group (blue color) was greater than placebo-treated at days 22 and 29. *P < 0.05, **P < 0.01, ***P < 0.001. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Dark arrowhead represents the last day of treatment. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107-treated, and high-frequency CYT107-treated patients, respectively. (C) The CYT107 treatment effect on ALCs is displayed for each patient over the study duration.

Figure 3. CYT107 increased CD4⁺ and CD8⁺ T cell counts.

(A) The effect of CYT107 on the averaged CD4⁺ and CD8⁺ T cell counts, considered for study duration, was significant for both CD4⁺ and CD8⁺ T cells. The low-frequency regimen (red color) significantly increased CD4⁺ and the high-frequency regimen (blue color) increased CD8⁺ T cells compared with placebo. Low-frequency CYT107 therapy increased CD4⁺ T cells at days 8, 15, and 22. High-frequency CYT107 therapy increased CD8⁺ T cells at day 42. *P < 0.05, **P < 0.01. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively. (B) The effect of CYT107 on individual patient CD4⁺ and CD8⁺ T cell counts is presented. Note that the patients at US sites had quantification of CD4⁺ and CD8⁺ T cell counts for 6 weeks, while the patients at French sites had quantification out to 4 weeks only.

Figure 4. CYT107 causes an initial drop in circulating CD8⁺ T cells.

CYT107 caused an early transient decrease in CD4⁺ and CD8⁺ T cells prior to significantly increasing lymphocyte counts. Individual septic patients treated with low- and high-dose CYT107 regimens are depicted in red and blue color, respectively. The placebo-treated patients are presented as a group and depicted with a solid black line. At day 4, CD8⁺ T cells were significantly decreased in patients receiving low-frequency regimen CYT107 (red color) compared with placebo (P ≤ 0.05). The effect of CYT107 to decrease CD4⁺ T cells did not quite achieve statistical significance. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively.

Figure 5. CYT107 effect on absolute neutrophil and absolute monocyte counts.

(A) The top right panel depicts the patients’ absolute neutrophil counts (ANCs) with the shaded gray area showing the normal counts for healthy individuals. Septic patients had an increase in their ANCs that returned to the normal range as their sepsis improved. There was an overall treatment effect of CYT107 on ANC. Further, there was an effect of high-frequency CYT107 to increase ANCs at weeks 3, 4, and 6. The top left panel depicts patients’ absolute monocyte counts (AMCs). Patients’ AMCs were generally within the normal range (shaded gray region) during their sepsis and not different in the 3 treatment groups. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively. *P < 0.05, **P < 0.01, ***P < 0.001. (B) The lower left and lower right panels depict the ANCs and AMCs respectively for each patient in the 3 treatment groups, i.e., placebo, low-frequency CYT107 group, and high-frequency CYT107 group.

Figure 6. CYT107 increased lymphocyte proliferation.

(A) CYT107 increased the percentage of Ki67-positive CD4⁺ and CD8⁺ T cells from approximately 10% at pre–CYT107 treatment to approximately 46% and 22%, respectively, on average for both CYT107 treatment groups. In contrast, there was no significant change in the percentage of cells that were Ki67 positive in placebo-treated patients. There was an overall treatment effect on Ki67 in both CD4⁺ and CD8⁺ T cells, individually showing an effect of low-dose CYT107 therapy to increase Ki67 in CD4⁺ T cells and both regimens to increase Ki67 in CD8⁺ T cells as compared with placebo. Additionally, in CD4⁺ T cells the low-frequency group displayed increased Ki67 at days 4, 8, 22, 29, and 42, while in CD8⁺ T cells, the high-frequency group showed increases at days 15 and 29, and both treatment groups at day 8 as compared with placebo. *P < 0.05, **P < 0.01. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively. (B) The effect of CYT107 on lymphocyte proliferation, as determined by flow cytometric quantification of Ki67, is provided for each patient. US study patients had flow cytometric quantification of Ki67 for 6 weeks, while French study patients had flow cytometric quantification out to 4 weeks only. Baseline adjustment reflects the difference between study day values and the predosing values.

Figure 7. CYT107 decreased IL-7 receptor α (CD127) expression.

(A) The IL-7 receptor is composed of a common γ chain and the IL-7 receptor α (CD127). CD127 is known to be transiently downregulated after administration of IL-7. Flow cytometry showed that there was a decrease in CD4⁺ and CD8⁺ T cell expression of IL-7 receptor α in patients treated with both low- and high-frequency treatment regimens of CYT107 versus placebo at day 4. *P < 0.05. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM for the 3 different treatment groups, i.e., placebo, low-frequency CYT107, and high-frequency CYT107. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively. (B) The lower left and lower right panels depict the percentages of CD4⁺ and CD8⁺ T cells positive for the IL-7 receptor α respectively for each patient in the 3 treatment groups, i.e., placebo, low-frequency CYT107 group, and high-frequency CYT107 group. US study patients had flow cytometric quantification of Ki67 for 6 weeks, while French study patients had flow cytometric quantification out to 4 weeks only. Baseline adjustment reflects the difference between study day values and the predosing values.

Figure 8. CYT107 increased early activation markers in CD4⁺ T cells.

(A) The expression of CD38 and HLA-DR increases during T cell activation. The CYT107 treatment effect for CD38, considered for the entire duration of the study, was significant for low-frequency dosing regimen CYT107 (red color) in CD4⁺ T cells (upper left panel). Additionally, the high-frequency dosing regimen for CYT107 (upper right panel, blue color) showed an increase in HLA-DR expression in CD4⁺ T cells, which approached significance at days 8 (P = 0.07) and 22 (P = 0.055). *P < 0.05. Statistical tests were conducted using a Wald-type multiple-degree-of-freedom method. Values reported are mean ± SEM. n = 10, 8, and 9 for placebo, low-frequency CYT107, and high-frequency CYT107-treated patients, respectively. (B) The lower left and lower right panels depict the effect of CYT107 on CD38 and HLA-DR expression respectively for each patient in the 3 treatment groups, i.e., placebo, low-frequency CYT107, and high-frequency CYT107. Baseline adjustment reflects the difference between study day values and the predosing values.

Figure 9. Pharmacokinetics of CYT107.

CYT107 (human recombinant CYT107) was measured in patients EDTA-3K plasma at 1, 3, 5, 9, and 24 hours after intramuscular administration. The blue curve shows the kinetics after the first administration at day 1 and the red curve after administration at day 22. Values reported are mean ± SEM. n = 17 patients on day 1 and n = 9 patients on day 22.