Abstract
Introduction
Thymosin-α-1 (Tα1) elevates lymphocyte counts among patients with COVID-19, but its effect on reversing lymphocytopenia is unknown.
Methods
24 patients treated with Tα1 and 100 patients in the control arm were included in this analysis. The incidence rate of reversing lymphocytopenia, overall and stratified by baseline oxygen support, above the threshold for classification of lymphocytopenia (i.e., Total Lymphocyte Count (TLC) < 1.5 × 109/L) and severe lymphocytopenia (i.e., TLC < 1.0 × 109/L) within 3, 5, and 7 days of treatment initiation was calculated, along with incidence rate ratios (IRRs) and 95 % confidence intervals (CIs).
Results
Compared with the standard of care, the rate of reversing lymphocytopenia (IRR: 2.38, 95 % CI: 0.92 – 5.81) and severe lymphocytopenia (IRR: 1.57, 95 % CI: 0.60 – 3.72), especially among patients with severe lymphocytopenia on high flow oxygen support (IRR: 3.64, 95 % CI: 0.71 – 23.44), was greater for patients treated with Tα1 within 3 days of treatment initiation, although analyses were not significant.
Conclusion
Among patients with hypoxemia and lymphocytopenia, Tα1 may reverse lymphocytopenia and severe lymphocytopenia, particularly within 3 days of treatment initiation, faster than the standard of care.
Keywords: Thymalfasin, Thymosin-alpha-1, COVID-19, Lymphocytopenia, Lymphopenia, Severe COVID-19
1. Introduction:
Lymphocytopenia is associated with severe coronavirus disease 2019 (COVID-19) infection [[1], [2]] and poor clinical outcomes [[3], [4]]. Direct infection of CD4+ T-cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [5] and cytokine dysregulation [[2], [6]] are two main mechanisms by which lymphocytopenia manifests among patients with COVID-19. Among hospitalized patients with COVID-19, the proportion with lymphocytopenia differs across studies, with one study reporting that 83 % of patients had a total lymphocyte count (TLC) < 1.5 × 109/L [1], while another study reported that 63 % of patients had a TLC < 1.0 × 109/L [7].
Thymosin-alpha-1 (Tα1) is a 28 amino acid peptide thymic hormone [8] that may restore immune function in the treatment of malignancies and infectious diseases [[9], [10]]. The purported mechanism of action for Tα1 in restoring immune function involves regulating cytokine expression and activating dendritic cells to stimulate the adaptive arm of the immune system [9]. In the context of COVID-19, early ex vivo data indicated that Tα1 downregulated transcriptional expression of inflammatory cytokines, such as interleukin-6, interleukin-1β, and tumor necrosis α [11], and reversed T-cell exhaustion primarily by boosting naïve T-cell circulation [12]. Moreover, from the preliminary analysis of our pilot trial, we found that Tα1 is safe and increases CD4+ T-cell count among patients with hypoxemia and lymphocytopenia on low flow oxygen support [13].
The objective of the present report was to evaluate the effect of Tα1 in restoring TLC above the threshold for classification of both lymphocytopenia (i.e., TLC < 1.5 × 109/L) and severe lymphocytopenia (i.e., TLC < 1.0 × 109/L) among patients with hypoxemia and lymphocytopenia due to COVID-19.
2. Methods:
2.1. Study population
Detailed information, including inclusion and exclusion criteria, regarding patients enrolled into our pilot trial are described elsewhere [13]. Notably, we sought to enroll patients aged ≥ 18 years admitted with COVID-19, hypoxemia, defined as either oxygen saturation (SpO2) ≤ 93 % on room air or a requirement for supplemental oxygen support, and lymphocytopenia, defined as TLC < 1.5 × 109/L. Patients in the treatment arm received the standard of care plus thymalfasin subcutaneously, at a daily dose of 1.6 mg in 1 mL of diluent, starting the day of randomization (day 1) for 7 consecutive days or until death, hospital discharge, or withdrawal from the study. Patients in the control arm only received the standard of care.
In the present report we include additional enrolled patients with follow-up data up to October 8, 2022. Specifically, we add one additional patient who was randomized to the treatment arm and two additional patients who were randomized to the control arm. Then, to evaluate the effect of Tα1 in restoring TLC, we matched the 24 enrolled patients who were randomized to the Tα1 arm in a 1:3 ratio to randomly selected patients who were eligible and declined enrollment into the pilot trial. These 72 randomly selected patients were added with the 28 enrolled patients who were randomized to the control arm of the pilot trial to comprise the control arm of the present report.
2.2. Data collection for randomly selected controls
Baseline characteristics were recorded on day 1, defined as the day of approach for enrollment for the randomly selected control patients. TLCs, first recorded on day 1, were collected as part of standard clinical care throughout the hospital course. Similar to enrolled patients, TLC data was only collected while patients remained hospitalized. Acute illness severity at baseline was measured using the National Early Warning Score (NEWS) [14], and comorbidity burden was measured by the van Walraven weighted Elixhauser Comorbidity Index Score [15]. Concurrent use of remdesivir and corticosteroids at baseline was defined as receipt of ≥ 1 dose of the respective medication within 24 h of end of the workday on the day of approach for enrollment. Supplemental oxygen support status (i.e., SpO2 ≤ 93 % on room air, noninvasive ventilation, or low flow or high flow delivery system) was recorded at end of the workday on the day of approach for enrollment.
2.3. Endpoints
Primary endpoints were to assess the effect of Tα1, compared with the standard of care, on time to reverse lymphocytopenia, defined as restoring TLC ≥ 1.5 × 109/L, and time to reverse severe lymphocytopenia, defined as restoring TLC ≥ 1.0 × 109/L, within 3, 5, and 7 days of treatment initiation. Time to reverse severe lymphocytopenia was assessed among patients with severe lymphocytopenia (i.e., TLC < 1.0 × 109/L) on day 1. To determine TLC using flow cytometry, the BD FACSCanto System (Becton Dickinson) was utilized. Subgroup analyses were also performed to assess primary endpoints stratified by baseline low flow or high flow oxygen support, so the 3 randomly selected control patients who were either on room air with SpO2 ≤ 93 % or noninvasive ventilation at baseline were excluded from stratified analyses.
A secondary endpoint was to assess, using day 1 as reference, the absolute mean TLC difference at day 3, 5, and 7 within treatment arms among all patients and patients with severe lymphocytopenia on day 1, while stratifying by baseline oxygen support.
2.4. Statistical analysis
Continuous variables were represented as medians with interquartile ranges [IQRs]. Univariate tests of association between treatment arms and baseline demographic, health, and clinical characteristics were performed using Wilcoxon rank sum tests for continuous variables and either Pearson’s chi-square test for independence or, when applicable, Fisher’s exact test for categorical variables.
To assess the primary endpoints, we calculated the incidence rate of reversing lymphocytopenia and severe lymphocytopenia within 3, 5, and 7 days for each treatment arm. For each primary endpoint, a case was defined as a patient who reached the primary endpoint. Individual follow-up time, measured in days, was calculated starting day 1 to either day 7 or day of last recorded TLC value. For each primary endpoint, if a hospitalized patient who had not yet reached the primary endpoint had at least one missing TLC value in between their previous recorded TLC value and their subsequent recorded TLC value, then we assumed that they remained lymphopenic on the days pertaining to their missing TLC value(s). Furthermore, we calculated incidence rate ratios (IRRs), along with 95 % confidence intervals (CIs), to compare the relative rate of reversing lymphocytopenia and severe lymphocytopenia between patients treated with Tα1 and control patients.
Because the randomly selected controls were not followed according to the study protocol, it is plausible that restored TLC was missed on day 3, 5, or 7. We thus performed a sensitivity analysis for the primary endpoints in which if any hospitalized patient had a missing TLC value on day 3, 5, or 7, then we used their next available TLC value.
Then, to assess the secondary endpoint, we utilized paired t-tests to assess absolute mean TLC differences at day 3, 5, and 7, respectively, from baseline within treatment arms. Only patients who had available data on both respective days being compared were included for analysis. Analyses were performed using Stata software, version 17.0 (StataCorp). Significance was set at α = 0.05.
3. Results:
3.1. Baseline characteristics
A total of 124 patients were included in this analysis, with 24 patients in the Tα1 arm and 100 patients in the control arm. Baseline characteristics were mainly comparable between patients treated with Tα1 and the control arm (Table 1 ), as well as baseline oxygen support status, a surrogate for disease severity, between enrolled patients and randomly selected controls that denied enrollment (Table S1). The median age of patients treated with Tα1 was 64 years [IQR: 49 – 80.5] and 63 years [IQR: 54 – 75] for patients in the control arm. Additionally, baseline median TLCs were comparable between treatment arms (Table 2 ) among all patients (Tα1: 0.7 × 109/L vs Control: 0.6 × 109/L) and among patients with severe lymphocytopenia on day 1 (Tα1: 0.6 × 109/L vs Control: 0.6 × 109/L). We note that there was a difference in the race and ethnicities of patients across treatment arms (p = 0.02), with numerically greater proportions of Non-Hispanic White (83 % vs 66.7 %) and Hispanic/Latinx (10 % vs 4.2 %) in the control arm compared with the treatment arm.
Table 1.
Baseline demographic, health, and clinical characteristics.
| Total N = 124 |
Tα1 N = 24 |
Control N = 100 |
P-Value | |
|---|---|---|---|---|
|
Age [IQR] |
63 [53.5–76] |
64 [49 – 80.5] |
63 [54–75] |
0.88 |
|
Patient Sex Female |
56 (45.2 %) | 9 (37.5 %) | 47 (47 %) | 0.40 |
| Male | 68 (54.8 %) | 15 (62.5 %) | 53 (53 %) | |
| Race/Ethnicity | 0.02 | |||
| Non-Hispanic White | 99 (79.8 %) | 16 (66.7 %) | 83 (83 %) | |
| Hispanic or Latinx | 11 (8.8 %) | 1 (4.1 %) | 10 (10 %) | |
| Non-Hispanic Black | 7 (5.7 %) | 3 (12.5 %) | 4 (4 %) | |
| Other / Unknown | 7 (5.7 %) | 4 (16.7 %) | 3 (3 %) | |
|
Severe Lymphocytopenia (i.e., TLC < 1.0 × 109/L) No Yes |
25 (20.2 %) 99 (79.8 %) |
4 (16.7 %) 20 (83.3 %) |
21 (21 %) 79 (79 %) |
0.78 |
|
COVID-19 Vaccination* Not Fully Vaccinated Fully Vaccinated |
89 (71.8 %) 35 (28.2 %) |
20 (83.3 %) 4 (16.7 %) |
69 (69 %) 31 (31 %) |
0.16 |
|
Oxygen Support Low Flow High Flow |
69 (55.7 %) 52 (41.9 %) |
9 (37.5 %) 15 (62.5 %) |
60 (60 %) 37 (37 %) |
0.14 |
| Noninvasive Ventilation | 1 (0.8 %) | 0 (0 %) | 1 (1 %) | |
| SpO2 ≤ 93 % on room air | 2 (1.6 %) | 0 (0 %) | 2 (2 %) | |
|
Corticosteroid Use No |
4 (3.2 %) |
1 (4.2 %) |
3 (3 %) |
0.58 |
| Yes | 120 (96.8 %) | 23 (95.8 %) | 97 (97 %) | |
|
Remdesivir Use No Yes |
17 (13.7 %) 107 (86.3 %) |
3 (12.5 %) 21 (87.5 %) |
14 (14 %) 86 (86 %) |
1.0 |
|
NEWS [IQR] |
5 [5 – 6.5] |
5 [4.5 – 6.5] |
5 [5 – 6.5] |
0.90 |
|
Elixhauser Score < 0 0 |
28 (22.6 %) 50 (40.3 %) |
9 (37.5 %) 9 (37.5 %) |
19 (19 %) 41 (41 %) |
0.24 |
| 1 – 4 | 14 (11.3 %) | 2 (8.3 %) | 12 (12 %) | |
| ≥ 5 | 32 (25.8 %) | 4 (16.7 %) | 28 (28 %) |
*A patient was considered fully vaccinated against COVID-19 if either the date of enrollment (pilot trial cohort) or date of approach for enrollment (matched controls) was ≥ 14 days after their second messenger RNA vaccine dose or ≥ 14 days after their Johnson & Johnson vaccine. All patients who did not meet this definition were considered not fully vaccinated. Abbreviations: COVID-19: Coronavirus Disease 2019. IQR: Interquartile Range, NEWS: National Early Warning Score, SpO2: Oxygen Saturation, Tα1: Thymosin-α-1. TLC: Total Lymphocyte Count.
Table 2.
Baseline median TLC among all patients and patients with severe lymphocytopenia (i.e., TLC < 1.0 × 109/L) on day 1.
| Tα1 | Control | P-Value | |
|---|---|---|---|
|
All Patients Median (x 109/L) [IQR] |
N = 24 0.7 [0.4 – 0.85] |
N = 100 0.6 [0.4 – 0.85] |
0.89 |
|
Patients with Severe Lymphocytopenia Median (×109/L) [IQR] |
N = 20 0.6 [0.4 – 0.7] |
N = 79 0.6 [0.4 – 0.7] |
0.46 |
3.2. Effect of Tα1 on reversing lymphocytopenia
Among all patients treated with Tα1, a total of 10/24 (41.7 %) patients accomplished reversal of lymphocytopenia within 7 days of treatment initiation, with 9/10 (90 %) patients accomplishing reversal within 3 days and all 10 patients accomplishing reversal within 5 days (Table 3 ). Among all control patients, a total of 25/100 (25 %) patients accomplished reversal of lymphocytopenia within 7 days, with 15/25 (60 %) patients accomplishing reversal within 3 days and 23/25 (92 %) patients accomplishing reversal within 5 days.
Table 3.
Reversing lymphocytopenia (i.e., restore TLC ≥ 1.5 × 109/L) within 3, 5, and 7 days for each treatment arm.
| Total N = 124 |
Tα1 N = 24 |
Control N = 100 |
IRR (95% CI) |
|
|---|---|---|---|---|
|
Within 3 Days No.of patients that reversed lymphoctyopenia (i.e., Cases)v Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
24 333 7.2 |
9 67 13.4 |
15 266 5.6 |
2.38 (0.92–5.81) |
|
Within 5 Days No. of patients that reversed lymphoctyopenia (i.e., Cases) Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
33 465 7.1 |
10 91 11.0 |
23 374 6.1 |
1.79 (0.76–3.90) |
|
Within 7 Days No. of patients that reversed lymphoctyopenia (i.e., Cases) Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
35 560 6.3 |
10 115 8.7 |
25 445 5.6 |
1.55 (0.66–3.34) |
Abbreviations: CI: Confidence Interval, IRR: Incidence Rate Ratio, Tα1: Thymosin-α-1, TLC: Total Lymphocyte Count.
Within 3 days, while accounting for follow-up time, the incidence rate of reversing lymphocytopenia was 13.4 cases per 100 person-days among patients treated with Tα1 and 5.6 cases per 100 person-days among control patients. Thus, patients treated with Tα1, compared with control patients, had 2.38 (95 % CI: 0.92 – 5.81) times the rate of reversing lymphocytopenia within 3 days of treatment initiation, although this was not statistically significant. Within 5 days, the incidence rate of reversing lymphocytopenia was 11 cases per 100 person-days among patients treated with Tα1 and 6.1 cases per 100 person-days among control patients. Thus, patients treated with Tα1, compared with control patients, had 1.79 (95 % CI: 0.76 – 3.90) times the rate of reversing lymphocytopenia within 5 days. Finally, within 7 days, the incidence rate of reversing lymphocytopenia was 8.7 cases per 100 person-days among patients treated with Tα1 and 5.6 cases per 100 person-days among control patients. Overall, patients treated with Tα1, compared with control patients, had 1.55 (95 % CI: 0.66 – 3.34) times the rate of reversing lymphocytopenia within 7 days.
Among patients with baseline low flow oxygen support, patients treated with Tα1, compared with control patients, had 2.79 (95 % CI: 0.77 – 8.51), 2.38 (95 % CI: 0.69 – 6.71), and 1.99 (0.58 – 5.56) times the rate of reversing lymphocytopenia within 3, 5, and 7 days, respectively, although results were not statistically significant (Table S2). Additionally, among patients with baseline high flow oxygen support, patients treated with Tα1, compared with control patients, had 3.24 (95 % CI: 0.55 – 22.13), 2.08 (95 % CI: 0.50 – 8.19), and 1.79 (95 % CI: 0.45 – 6.55) times the rate of reversing lymphocytopenia within 3, 5, and 7 days, respectively, although results were also not statistically significant (Table S3).
3.3. Effect of Tα1 on reversing severe lymphocytopenia
Among all patients with severe lymphocytopenia on day 1 treated with Tα1, a total of 15/20 (75 %) patients accomplished reversal of severe lymphocytopenia within 7 days of treatment initiation, with 8/15 (53.3 %) patients accomplishing reversal within 3 days and 12/15 (75 %) patients accomplishing reversal within 5 days (Table 4 ). Among all control patients with severe lymphocytopenia, a total of 38/79 (48.1 %) patients accomplished reversal of severe lymphocytopenia within 7 days, with 20/38 (52.6 %) patients accomplishing reversal within 3 days and 31/38 (81.6 %) patients accomplishing reversal within 5 days.
Table 4.
Reversing severe lymphocytopenia (i.e., restore TLC ≥ 1.0 × 109/L) within 3, 5, and 7 days for each treatment arm.
| Total N = 99 |
Tα1 N = 20 |
Control N = 79 |
IRR (95 % CI) |
|
|---|---|---|---|---|
|
Within 3 Days No.of patients that reversed lymphoctyopenia (i.e., Cases) Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
28 261 10.7 |
8 53 15.1 |
20 208 9.6 |
1.57 (0.60 – 3.72) |
| Within 5 Days No.of patients that reversed lymphoctyopenia (i.e., Cases) Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
43 356 12.1 |
12 74 16.2 |
31 282 11.0 |
1.48 (0.69 – 2.95) |
|
Within 7 Days No.of patients that reversed lymphoctyopenia (i.e., Cases) Follow-up time (Person-days) Incidence Rate (Cases per 100 person-days) |
53 419 12.6 |
15 88 17.0 |
38 331 11.5 |
1.48 (0.76 – 2.76) |
Abbreviations: CI: Confidence Interval, IRR: Incidence Rate Ratio, Tα1: Thymosin-α-1, TLC: Total Lymphocyte Count.
Within 3 days, the incidence rate of reversing severe lymphocytopenia was 15.1 cases per 100 person-days among patients treated with Tα1 and 9.6 cases per 100 person-days among control patients. Thus, patients treated with Tα1 had 1.57 (95 % CI: 0.60 – 3.72) times the rate of reversing severe lymphocytopenia within 3 days of treatment initiation, although this was not statistically significant. Within 5 days, the incidence rate of reversing severe lymphocytopenia was 16.2 cases per 100 person-days among patients treated with Tα1 and 11 cases per 100 person-days among control patients. Thus, patients treated with Tα1, compared with control patients, had 1.48 (95 % CI: 0.69 – 2.95) times the rate of reversing severe lymphocytopenia within 5 days. Finally, within 7 days, the incidence rate of reversing severe lymphocytopenia was 17.0 cases per 100 person-days among patients treated with Tα1 and 11.5 cases per 100 person-days among control patients. Overall, patients treated with Tα1, compared with control patients, had 1.48 (95 % CI: 0.76 – 2.76) times the rate of reversing severe lymphocytopenia within 7 days.
Among patients with baseline low flow oxygen support, patients treated with Tα1, compared with control patients, had 1.42 (95 % CI: 0.27 – 4.92), 1.38 (95 % CI: 0.35 – 4.07), and 1.47 (0.44 – 3.91) times the rate of reversing severe lymphocytopenia within 3, 5, and 7, respectively, although results were not statistically significant (Table S4). Additionally, among patients with baseline high flow oxygen support, patients treated with Tα1, compared with control patients, had 3.64 (95 % CI: 0.71 – 23.44), 2.31 (95 % CI: 0.76 – 7.08), and 2.03 (95 % CI: 0.78 – 5.12) times the rate of reversing severe lymphocytopenia within 3, 5, and 7 days, respectively, although results were not statistically significant (Table S5).
3.4. Sensitivity analyses
Among all patients, the number of patients with a missing value at day 3, day 5, and day 7 was 12, 7, and 1, respectively. Among patients with severe lymphocytopenia on day 1, the number of patients with a missing value at day 3, day 5, and day 7 was 11, 4, and 1, respectively. Results from all sensitivity analyses assessing reversal of lymphocytopenia and reversal of severe lymphocytopenia were similar to our main findings and presented in Table S6 .
3.5. Absolute mean TLC difference within treatment arms
Among all patients with baseline low flow oxygen support, peak absolute mean TLC increase from baseline for patients treated with Tα1 (0.82 × 109/L, 95 % CI: −0.93 – 2.57) and control patients (0.43 × 109/L, 95 % CI: 0.22 – 0.65) were observed on day 7 and day 5, respectively (Table S7). Among all patients with baseline high flow oxygen support, peak absolute mean TLC increase from baseline for patients treated with Tα1 (0.45 × 109/L, 95 % CI: 0.14 – 0.89) and control patients (0.45 × 109/L, 95 % CI: 0.13 – 0.76) were observed on day 7 (Table S8).
Among patients with severe lymphocytopenia on day 1 and low flow oxygen support, peak absolute mean TLC increase from baseline for patients treated with Tα1 (1.37 × 109/L, 95 % CI: −2.80 – 5.53) and control patients (0.52 × 109/L, 95 % CI: 0.15 – 0.89) were observed on day 7 (Table S7). Lastly, among patients with severe lymphocytopenia on day 1 and on high flow oxygen support, peak absolute mean TLC increase from baseline for patients treated with Tα1 (0.46 × 109/L, 95 % CI: −0.02 – 0.95) and control patients (0.32 × 109/L, 95 % CI: 0.01 – 0.62) were observed on day 7 (Table S8). The absolute mean TLC increase on days 3 and 5 is detailed in Table S7 and Table S8.
4. Discussion:
Infections with viruses, such as SARS-CoV-2 and influenza virus, may result in the manifestation of lymphocytopenia [16], which impacts the clinical prognosis of infected persons. Specifically among patients with COVID-19, lymphocytopenia is a common clinical presentation [[1], [7]], so elevating TLC to promote reversal of lymphocytopenia is of clinical significance. In the present report, we found that Tα1 may restore TLC above threshold for classification of lymphocytopenia (i.e., TLC < 1.5 × 109/L) and severe lymphocytopenia (i.e., TLC < 1.0 × 109/L) within 7 days of treatment initiation, particularly within 3 days, faster than the standard of care.
A reduction in lymphocyte count among patients with COVID-19 is associated with severe infection [[1], [2]] and poor clinical outcomes [[3], [4]]. For instance, Guan et al. found that TLC < 1.5 × 109/L at inpatient admission is associated with severe COVID-19 infection [1], while Huang et al. found that TLC < 1.0 × 109/L is associated with intensive care unit admission [7]. Additionally, among hospitalized patients with influenza, TLC < 1.0 × 109 is associated with respiratory failure and TLC as low as < 0.3 × 109/L is associated with poor composite endpoint of respiratory failure, greater sequential organ failure assessment score, and death [17]. Furthermore, continued impairment of lymphocyte cell function, such as diminished CD4+ T-cell functionality and exhaustion of CD8+ T-cell and natural killer cells, is observed in immunological non-responders living with human immunodeficiency virus [10]. Of note, Tα1, in conjunction with antiretroviral therapy and interferon α, elevates CD4+ T-cells among patients with CD4+ T-cell count between 0.200 × 109/L and 0.500 × 109/L [[18], [19]]. Also, Tα1, in conjunction with antiretroviral therapy, increases thymic output as measured by elevated levels of signal joint T-cell receptor excision circles [20], which are by-products of naïve T-cell maturation.
A decrease in the number of T-cells and natural killer cells [[6], [21]], along with increased levels of CD8+ T-cell exhaustion markers, such as programmed cell death protein 1 (PD-1) and T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) [[6], [22]] are observed during COVID-19 infection. Early data by Yu et al. found that Tα1 significantly elevated TLC among 25 patients with severe and critical COVID-19 [23], while Liu et al. found that, among patients with severe COVID-19, Tα1 increased thymic output, decreased levels of PD-1 and Tim-3, and elevated CD4+ and CD8+ T-cell count among patients with < 0.650 × 109/L and 0.400 × 109/L, respectively, at admission [12]. Moreover, clinical trial data by Shetty et al. found that Tα1 increases both CD4+ and CD8+ T-cell counts among patients with either moderate or severe COVID-19 [24].
Importantly, in this second report from our ongoing trial study (NCT04487444), we enhanced the statistical power by including additional enrolled patients and matching patients treated with Tα1 in a 1:3 ratio. This additional analysis has allowed us to evaluate the effect of Tα1 on reversing both lymphocytopenia and severe lymphocytopenia within 3, 5, and 7 days of treatment initiation. We found that Tα1, compared with the standard of care, may reverse lymphocytopenia and severe lymphocytopenia faster and most profoundly within 3 days. Notably, we previously found that Tα1 increases CD4+ T-cell count faster specifically among patients with baseline low flow oxygen support [13]. In the present report, we found that the effect of Tα1 on reversing lymphocytopenia may be consistent across low flow or high flow oxygen support, and in particular, the effect of reversing severe lymphocytopenia may be most prominent among patients on high flow oxygen support. Thus, while the effect of Tα1 on increasing CD4+ T-cell count may be limited based on supplemental oxygen requirement, the effect of restoring TLC may not be as limited, which could potentially promote clinical recovery for patients treated with Tα1.
Reduced lymphocyte count among convalescent patients with COVID-19 has been observed weeks following symptom onset [[25], [26]] and may be associated with persistent symptoms [26]. Additionally, an increasing trend in lymphocyte count throughout disease course is observed among survivors of initial COVID-19 infection, while non-survivors maintained lower lymphocyte count [[27], [28]]. The recovery of lymphocyte count is also delayed among patients with severe COVID-19 infection, such as patients with greater degree of pulmonary involvement [25], compared with patients with mild infection [29]. Because reduced lymphocyte counts are associated with unfavorable outcomes and the time for TLC to recover takes longer for patients with more severe COVID-19 infection, our current findings that Tα1 may reverse lymphocytopenia and severe lymphocytopenia merit further investigation.
Limitations to the present report include that for the randomly selected controls, collection of TLC data throughout the hospital course was strictly left to the discretion of the attending providers rather than as prompted by a study protocol as with the pilot trial patients, which could potentially overestimate the effect of Tα1. Though, for the inpatient management of COVID-19, complete blood cell count with differential is a recommended daily laboratory measurement to monitor trends such as TLC [30]. Nevertheless, findings from sensitivity analyses accounting for this type of ascertainment bias did not differ from our main findings. Second, although we enhanced the statistical power of the pilot trial analysis, the sample size of the present report is still relatively limited, which may have contributed to the baseline difference in race and ethnicity of patients between treatment arms and precluded statistically significant findings, so we cannot conclusively comment on the clinical significance of our findings.
5. Conclusion:
Among patients with hypoxemia and lymphocytopenia, we found that Tα1 may reverse lymphocytopenia and severe lymphocytopenia, particularly within 3 days of treatment initiation. Furthermore, the effect of Tα1 on reversing severe lymphocytopenia may be most prominent among patients with baseline high flow oxygen support. Taken in their totality, cumulative data from our ongoing trial indicate that Tα1 is primed for continued assessment in the management of COVID-19 to definitively assess the effect of Tα1 on reversing lymphocytopenia and promoting clinical recovery.
Funding Source: This work was supported by SciClone Pharmaceuticals International ltd.
CRediT authorship contribution statement
Gregorio Benitez: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing – original draft. Fadi Shehadeh: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing – review & editing. Evangelia K. Mylona: Investigation, Data curation, Writing – review & editing. Quynh-Lam Tran: Investigation, Writing – review & editing. Maria Tsikala-Vafea: Investigation, Writing – review & editing. Eleftheria Atalla: Investigation, Writing – review & editing. Matthew Kaczynski: Investigation, Writing – review & editing. Eleftherios Mylonakis: Conceptualization, Methodology, Investigation, Writing – review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.intimp.2023.109831.
Appendix A. Supplementary material
The following are the Supplementary data to this article:
Data availability
Data will be made available on request.
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Data Availability Statement
Data will be made available on request.