Thymosin alpha 1 - Reimagine its broader applications in the immuno-oncology era.

Thymosin alpha 1 (Tα1) is a highly conserved 28 amino-acid peptide naturally occurring in the thymus and plays critical roles in T cell maturity and differentiation. Its synthetic form, thymalfasin, has been approved by various regulatory agencies in the treatment of hepatitis B viral infection and as an enhancer of vaccine response in immune-compromised populations. In China, it has also widely utilized in patients with cancer and severe infections, as well as the emergency use during (Severe Acute Respiratory Syndrome)SARS and COVID-19 pandemic as an immune-regulator. Recent studies showed that Tα1 could significantly improve overall survival (OS) in patients with surgically resectable non-small cell lung cancer (NSCLC) and liver cancers in the adjuvant setting. For patients with locally advanced, unresectable NSCLC, Tα1 could significantly reduce chemoradiation-induced lymphopenia, pneumonia, and trending improvement of OS. Preclinical evidence are emerging to demonstrate that Tα1 may augment efficacy of cancer chemotherapy by reversing efferocytosis-induced M2 polarization of macrophages via activation of a TLR7/SHIP1 axis and enhancing anti-tumor immunity by turning "cold-tumors" to "hot-tumors"; a protective role in reducing colitis caused by immune check-point inhibitors (ICIs). Potential enhancement of ICIs' clinical efficacies has also been indicated. ICIs have transformed ways treating patients with cancer but limitations such as relatively low response rates and certain safety issues remains. Given the roles of Tα1 in regulating cellular immunities and exceptional safety profiles demonstrated in decades clinical uses, we believe that it is plausible to explore implications of Tα1 the immune-oncology setting by combining with ICI-based therapeutic strategies. Background Activities of Tα1. Tα1 is a biological response modifier which activates various cells in the immune system [1-3]. Tα1 is therefore expected to have clinical benefits in disorders where immune responses are impaired or ineffective. These disorders include acute and chronic infections, cancers, and vaccine non-responsiveness. In severe sepsis, for example, sepsis-induced immunosuppression is increasingly recognized as the overriding immune dysfunction in these vulnerable patients [4] and there is now agreement that many patients with severe sepsis survive the first critical hours of the syndrome but eventually die later due to patients' immunosuppression which make the system difficulty to fight the primary bacterial infection, decreased resistance to secondary nosocomial infections, and reactivation of viral infections [5]. Tα1 has been shown to restore immune functions and help to reduce mortality in patients with severe sepsis.