Thymosin-α1 for Recurrent Implantation Failure

Despite significant advancements in assisted reproductive technologies (ART), recurrentimplantation failure (RIF) remains a persistent challenge. Growing evidence implicatesdysregulation of both local endometrial and systemic immune components in thepathophysiology of RIF.This has led to increasing attention on immune dysregulation, including aberrant cytokinesignaling, altered Th1/Th2 balance, heightened NK cell cytotoxicity, and impairedmaternal‐fetal tolerance as possible contributors. These immunological pathways arecritical for embryo implantation and pregnancy continuation; their disruption can createan environment hostile to the developing conceptus.Thymosin‐α1 (Tα1) is a naturally occurring thymic peptide with immune‐modulatoryproperties. It has been historically used in the management of chronic viral infectionsand certain cancers, where it demonstrated the ability to enhance T‐cell function,rebalance cytokine networks, and improve immune resilience. Its safety profile innon‐obstetric conditions is well established.Although comprehensive safety evaluation of thymosin alpha in pregnant women has not yetbeen completed, emerging evidence from observational studies, case reports, and proposedclinical trials suggests that thymosin alpha is generally regarded as safe duringpregnancy, with no reported adverse effects linked to its use to date. Specifically, apublished case report documented successful pregnancy following thymosin alphaadministration in a woman with recurrent implantation failure, noting an absence of fetalanomalies or significant adverse events and emphasizing the need for further prospectivetrials to establish broader safety and efficacy. Preliminary clinical protocols continueto monitor for adverse events in patients undergoing reproductive treatments, and nonehave identified safety concerns thus far.Emerging reproductive data suggest a potential role of Tα1 in implantation and pregnancymaintenance. Observational work reported lower maternal Tα1 levels in women whosepregnancies ended in miscarriage compared with those that continued to viability; thiseffect was not seen with thymosin‐β4, suggesting specificity. Mechanistically, Tα1enhances T‐cell maturation, restores Th1/Th2 balance, and promotes regulatory T‐cellactivity‐processes central to maternal immune tolerance during early pregnancy.Taken together, these findings highlight a gap: Tα1 has biological plausibility and earlysignals but no definitive RCT evidence. This underlines the need for a rigorous,placebo‐controlled study of Tα1 in women with RIF. To our knowledge, this is the firstrandomized placebo‐controlled study looking at Tα1 in RIF patients undergoing treatmentusing PGT‐a tested embryos.