Phenotypic drug discovery (PDD) involves screening compounds for their effects on cells, tissues, or whole organisms without necessarily understanding the underlying molecular targets. PDD differs from target-based strategies as it does not require knowledge of a specific drug target or its role in the disease. This approach can lead to the discovery of drugs with unexpected therapeutic effects or applications and allows for the identification of drugs based on their functional effects, rather than through a predefined target-based approach. Ultimately, disease definitions are mostly symptom-based rather than mechanism-based, and the therapeutics should be likewise. In recent years, there has been a renewed interest in PDD due to its potential to address the complexity of human diseases, including the holistic picture of multiple metabolites engaging with multiple targets constituting the central hub of the metabolic host-microbe interactions. Although PDD presents challenges such as hit validation and target deconvolution, significant achievements have been reached in the era of big data. This article explores the experiences of researchers testing the effect of a thymic peptide hormone, thymosin alpha-1, in preclinical and clinical settings and discuss how its therapeutic utility in the precision medicine era can be accommodated within the PDD framework.

Dysregulation of immune response was observed in COVID-19 patients. Thymosin alpha 1 (Tα1) is used in the management of COVID-19, because it is known to restore the homeostasis of the immune system during infections and cancers. We aim to observe the longitudinal changes in T lymphocyte subsets and to evaluate the efficacy of Tα1 for COVID-19. A retrospective study was conducted in 275 COVID-19 patients admitted to Shanghai public health clinical center. The clinical and laboratory characteristics between patients with different T lymphocyte phenotypes and those who were and were not treated with Tα1 were compared. Among the 275 patients, 137 (49.8%) were males, and the median age was 51 years [interquartile range (IQR): 37-64]. A total of 126 patients received Tα1 therapy and 149 patients did not. There were 158 (57.5%) patients with normal baseline CD4 counts (median:631/μL, IQR: 501~762) and 117 patients (42.5%) with decreased baseline CD4 counts (median:271/μL, IQR: 201~335). In those with decreased baseline CD4 counts, more patients were older (p<0.001), presented as critically ill (p=0.032) and had hypertension (p=0.008) compared with those with normal CD4 counts. There was no statistical difference in the duration of virus shedding in the upper respiratory tract between the two groups (p=0.214). In both the normal (14 vs 11, p=0.028) and the decreased baseline CD4 counts group (15 vs 11, p=0.008), duration of virus clearance in the patients with Tα1 therapy was significantly longer than that in those without Tα1 therapy. There was no significant difference in the increase of CD4+ (286 vs 326, p=0.851) and CD8+ T cell (154 vs 170, p=0.842) counts in the recovery period between the two groups with or without Tα1 therapy. Multivariate linear regression analysis showed that severity of illness (p<0.001) and Tα1 therapy (p=0.001) were associated with virus clearance. In conclusion, reduction of CD4+ T and CD8+ T cell counts were observed in COVID-19 patients. Tα1 may have no benefit on restoring CD4+ and CD8+ T cell counts or on the virus clearance. The use of Tα1 for COVID-19 need to be more fully investigated.

BACKGROUND: Previous studies have demonstrated the benefits of thymosin alpha-1 (Tα1) in anti-virus, immunological enhancement and anti-inflammation. However, it is controversial about the efficacy and safety of entecavir (ETV) plus Tα1 combination therapy versus ETV monotherapy in cirrhotic patients with hepatitis B virus (HBV) infection.
METHODS: The systematic review and meta-analysis of randomized clinical trials (RCTs) were performed to evaluate the efficacy and safety of ETV plus Tα1 combination therapy versus ETV monotherapy in HBV-related patients with cirrhosis. We performed a systematic literature search via PubMed, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Journals Database (VIP), and Chinese Biological Medicine database (CBM). Relative risk (RR) and standardized mean difference (SMD) with a fixed- or random- effect model were calculated. Heterogeneity was assessed through a Cochrane Q-test and I2 values.
RESULTS: Seven RCTs involving 1144 subjects were included in the systematic review and meta-analysis. Compared with ETV monotherapy, ETV plus Tα1 combination therapy led to a higher complete response (RR = 1.18; 95% CI, 1.07-1.30). In post treatment for 24 weeks, the HBV DNA undetectable rate and HBeAg loss rate were higher in ETV plus Tα1 group than in ETV alone group (RR = 1.91; 95% CI, 1.56-2.35; RR = 2.05; 95% CI, 1.62-2.60). However, after 48 and 52 weeks of treatment, there was no significant difference between the combination therapy and ETV monotherapy (RR = 1.07; 95% CI, 0.96-1.18; RR = 1.17; 95% CI, 0.89-1.55). At week 52 of treatment, the HBsAg loss rate of ETV plus Tα1 group was no significance with that of ETV alone group (RR = 1.03; 95% CI, 0.15-7.26). In comparison with ETV alone, the some biochemical parameters and liver fibrosis were obviously improved by ETV plus Tα1, and there was significant heterogeneity. In addition, the number of adverse events was significantly reduced by ETV plus Tα1, compared to ETV alone (RR = 0.48; 95% CI, 0.24-0.95).
CONCLUSIONS: ETV plus Tα1 might lead to a higher clinical response and a lower comprehensive adverse reaction rate in HBV-related patients with cirrhosis, compared to ETV alone. However, the whole patients included in this meta-analysis were from Chinese mainland, so that more worldwide RCTs with a larger sample size are needed to verify the current findings.

BACKGROUND: Thymosin alpha-1 (TA) has been reported to inhibit tumor growth as an immunomodulator. However, its mechanism of action in immunosuppressive cells is unclear. The purpose of this study was to investigate whether TA can reshape the immune microenvironment by inhibiting the function of myeloid-derived suppressor cells (MDSCs) in non-small cell lung carcinoma (NSCLC).
METHODS: The effects of TA on peripheral blood monocytic MDSCs (M-MDSCs) in patients with NSCLC and on the apoptosis and migration of M-MDSCs were studied. A mouse subcutaneous xenograft tumor model was constructed, and the effect of TA on M-MDSC migration was evaluated. Quantitative real-time PCR, Western blotting, flow cytometry and immunohistochemistry were used to examine the mechanism by which TA affects M-MDSCs.
RESULTS: TA not only promoted the apoptosis of M-MDSCs by reducing the Bcl-2/BAX ratio but also and more importantly inhibited the migration of MDSCs to the tumor microenvironment by suppressing the production of vascular endothelial growth factor (VEGF) through the downregulation of hypoxia-inducible factor (HIF)-1α in tumor cells.
CONCLUSIONS: TA may have a novel antitumor effect mediated by decreasing M-MDSC accumulation in the tumor microenvironment through reduced VEGF production.

This research was conducted to investigate the biochemical effects of thymosin alpha-1 using human lung cancer cells (A549). The A549 cells were treated with different concentrations of Thα1 for 24 h and the growth, inhibition of cells was determined. Thα1 revealed anti-proliferative effect at 24 and 48 μg/ml after 24 h. Furthermore, it indicated antioxidant properties by significantly enhancing the activity of catalase (12 μg/ml), superoxide dismutase (6 and 12 μg/ml), and glutathione peroxidase (3, 6 and 12 μg/ml) and reducing the production of cellular ROS. Our results showed that Thα1 inhibits the migration of A549 cells in a concentration-dependent manner after 24 and 48 h. Moreover, the effect of Thα1 on apoptosis was investigated by Hoechst 33342 staining and cell cycle analysis. Results demonstrated no significant effect on the induction of apoptosis in A549 cells. In conclusion, our results showed the antioxidant properties of Thα1 on A549 cancer cells.

In this research, the antioxidant property of thymosin alpha-1 (Thα1) peptide was investigated through various antioxidant methods. Thα1 showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 = 20 µM) and its 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging reached 45.33% at 80 µM (IC50 = 85 µM). In addition, hydroxyl and superoxide radical scavenging of Thα1 peptide exhibited a concentration-depended manner. The IC50 values of hydroxyl and superoxide radical scavenging were estimated to be 82 µM and 20 µM, respectively. The effect of Thα1 on eliminating superoxide radicals was higher (62.23%) than other antioxidant assays. Moreover, the antioxidant activity of Thα1 peptide was evaluated by measuring cellular reactive oxygen species (ROS). Results indicated that Thα1 decreased the generation of ROS level in 1321 N1 human neural asterocytoma cells. The inhibitory effect of Thα1 on angiotensin-converting enzyme (ACE) was determined. The kinetic parameters (Km and Vmax) and the inhibition pattern were examined. Based on the Lineweaver-Burk plot, Thα1 displayed a mixed inhibition pattern. The IC50 and Ki values of Thα1 were 0.8 µM and 3.33 µM, respectively. Molecular modeling suggested that Thα1 binds to ACE-domains with higher affinity binding to N-domain with the binding energy of -22.87 kcal/mol. Molecular docking indicated that Thα1 interacted with ACE enzyme (N- and C-domains) due to electrostatic, hydrophobic, and hydrogen forces. Our findings suggested that Thα1 possess a multifunctional peptide with dual antioxidant and ACE-inhibitory properties. Further researches are needed to investigate the antioxidant and anti-hypertensive effect of Thα1 both in vitro and in vivo.

Activation of inflammatory responses regulates the transmission of pain pathways through an integrated network in the peripheral and central nervous systems. The immunopotentiator thymosin alpha-1 (Tα1) has recently been reported to have anti-inflammatory and neuroprotective functions in rodents. However, how Tα1 affects inflammatory pain remains unclear. In the present study, intraperitoneal injection of Tα1 attenuated complete Freund\'s adjuvant (CFA)-induced pain hypersensitivity, and decreased the up-regulation of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in inflamed skin and the spinal cord. We found that CFA-induced peripheral inflammation evoked strong microglial activation, but the effect was reversed by Tα1. Notably, Tα1 reversed the CFA-induced up-regulation of vesicular glutamate transporter (VGLUT) and down-regulated the vesicular γ-aminobutyric acid transporter (VGAT) in the spinal cord. Taken together, these results suggest that Tα1 plays a therapeutic role in inflammatory pain and in the modulation of microglia-induced pro-inflammatory cytokine production in addition to mediation of VGLUT and VGAT expression in the spinal cord.

This study investigated the anti-tumor effects of stereotactic body radiation therapy (SBRT) with thymosin alpha-1 (Tα1) in heavily pretreated, metastatic esophageal squamous cell carcinoma (mESCC) patients. Thirty-one patients with at least 2 metastatic sites were enrolled. SBRT was delivered with a daily fraction of 5.0 Gy for a total dosage of 25 Gy over one week to one metastatic lesion. Concurrent Tα1 (1.6mg subcutaneously) was administered twice a week with an interval of 3-4 days until tumor progression of other documented metastatic lesions. Anti-tumor effects (the primary endpoint) were evaluated by assessing the CT/MRI response of other distinct measurable lesions. Secondary endpoints included treatment safety, survival outcomes and immune-related blood parameters. This study was registered at ClinicalTrials.gov (NCT 02545751). Partial response occurred in three (9.7%) patients, and 11 (35.5%) patients had stable metastatic disease, which yielded a metastatic-lesion control rate of 45.2%. Seventeen (54.8%) patients were documented to have progressive disease in other metastatic lesions. The median overall survival and abscopal progression free survival (APFS) times were 5.2 and 2.9 months, respectively. Significant differences in survival outcomes were observed between the abscopal control group (without progression in the abscopal lesions at 12 weeks) and the non-control group (P = 0.035 and 0.044, respectively). Treatment-related toxicity was acceptable, and no grade 4 acute toxicity occurred. Immunomonitoring of lymphocytes showed that the proportion of CD8+ T cells after treatment was significantly different between the abscopal control group and the non-control group (P=0.047). In conclusion, the combination of SBRT with Tα1 produced encouraging effects in heavily pretreated, mESCC patients and further research on radiation enhanced immunotherapy is warranted.

Immune checkpoint blockade antibodies (imAbs), such as the anti Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) ipilimumab (IPI) raised overall survival (OS) in metastatic melanoma (MM). Further, long-term OS is a crucial endpoint in MM. Thymosin alpha-1 (Tα1) with dacarbazine (DTIC) showed activity in a phase II trial and a compassionate use program (EAP). We report on long-term follow-up of patients treated with Tα1 to investigate the preconditioning role of Tα1 in imAbs-treated patients.
Records of patients with melanoma treated with Tα1 within a phase II trial and EAP program were reviewed comparing median OS among patients that sequentially received anti-CTLA-4 imAb and Tα1. Further, the effect of Tα1 on IPI long-term survivor patients was investigated.
Among patients treated with Tα1, 21/61 patients received sequentially even anti CTLA-4 imAbs. Median OS at the data cut-off was 57.8 and 7.4 months in patients treated sequentially with anti-CTLA-4 imAbs or not, respectively. Moreover, pretreatment with Tα1 in all (95) IPI-evaluable patients confirmed a significant increase in long-term OS.
This is the first report on long-term follow-up of Tα1-treated patients. Moreover, an advantage in OS in patients sequentially treated with Tα1 and IPI was seen that suggests a synergistic effect.