Thymosin α1 Elevates Lymphocyte Counts and Improves Immunoradiotherapy Outcomes in Patients with Advanced Cancer.
This retrospective, single-arm study evaluated the effects of a 7-day loading dose of thymosin α1 (Tα1) on peripheral blood lymphocyte counts, as well as the safety and efficacy of combining Tα1 with hypofractionated radiotherapy and PD-1 inhibitors in 48 patients with advanced or refractory cancers. Peripheral blood T cells, B cells, and natural killer cells were measured by flow cytometry before and after Tα1 administration. The study found that the 7-day Tα1 course was associated with statistically significant increases in total T cells, CD4+ T cells, and CD8+ T cells. Secondary outcomes including objective response rate, disease control rate, progression-free survival, and overall survival were also reported alongside adverse event data, with the authors characterizing the safety and efficacy profiles as satisfactory. Key limitations include the retrospective, non-randomized, single-arm design; the small and heterogeneous patient population spanning multiple tumor types; a median follow-up of only 13.7 months, which may be insufficient to assess long-term survival and late toxicities; and the absence of a control group, making it difficult to isolate Tα1's contribution. The authors acknowledge these findings are exploratory and call for larger, randomized, homogenous cohort studies to validate results.
Why this grade: Single-arm retrospective observational study in only 48 patients with mixed tumor types and no control group, limiting causal inference about Tα1's effects.
Background Radiotherapy combined with immunotherapy shows increasing efficacy in treating metastatic malignancies; however, positive outcomes may be negatively impacted by lymphocytopenia. Previous studies suggest thymosin α1 (Tα1) may mitigate radiation-induced lymphocytopenia. This study retrospectively evaluated the effects of a Tα1 loading dose on peripheral blood lymphocyte counts and assessed the safety and efficacy of radiotherapy combined with of PD-1 inhibitors in patients with advanced or refractory cancers. Methods A total of 48 patients received a 7-day loading dose of Tα1 (1.6 or 3.2 mg, once daily) followed by hypofractionated radiotherapy and PD-1 inhibitors. Peripheral blood T cells, B cells, and natural killer cells were quantified by flow cytometry before and after Tα1 treatment. The primary endpoint was the change from baseline in lymphocyte subset counts. Secondary endpoints included adverse events, objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). Results The median follow-up was 13.7 months. Tα1 treatment for 7 days significantly increased the median counts of peripheral blood total T cells (422.5/μL to 614.0 /μL, P + T cells (244.5/μL to 284.5/μL, P + T cells (159.0/μL to 222.5/μL, P Conclusion A 7-day loading dose of Tα1 elevated lymphocyte counts in advanced cancer patients and was accompanied by satisfactory safety and efficacy profiles. It should be noted that the median follow-up of 13.7 months may be insufficient to fully assess long-term survival outcomes and the potential for late-onset toxicities. As this was an exploratory analysis across multiple tumor types, these findings warrant validation in larger, randomized studies with more homogenous cohorts.
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