A two-amino-acid molecule made in Russia in the 1990s as a defined replacement for thymus extracts, meant to restore immune function that fades as the thymus shrinks with age. Laboratory and old-mouse work is internally consistent; human evidence is three small unregistered reports, none repeated. Against that sits worse breast cancer in tumour-prone mice and a cancelled chemotherapy effect. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Complete blood count with differential | Lymphocytes 1.5–3.0 × 10⁹/L; neutrophil-to-lymphocyte ratio below 2.0 | Detects lymphoid overgrowth or suppression |
| Helper (CD4) and cytotoxic (CD8) T-cell counts and ratio | CD4:CD8 ratio 1.5–2.5 | Helper T cells fell in the one human dataset on Vilon |
| Natural killer cell count | 150–500 cells/µL, or 7–20% of lymphocytes | The second cell population reported to fall during treatment |
| Naive CD4 T-cell fraction | Above 30% of CD4 cells at age 60 and over | Closest available readout of thymic output, the intended target |
| Antithrombin III activity | 80–120% | Vilon raised this natural anticoagulant; rising values with bleeding signs warrant stopping |
| Protein C activity | 70–140% | The second anticoagulant protein reported to rise |
| International normalised ratio and activated partial thromboplastin time | International normalised ratio 0.9–1.1 if not anticoagulated; within the prescribed therapeutic window if anticoagulated | Catches additive anticoagulant effect |
| Fasting glucose and glycated haemoglobin | Glucose 70–85 mg/dL; glycated haemoglobin below 5.4% | Vilon reduced insulin requirement, making low blood sugar the exposure |
| High-sensitivity C-reactive protein | Below 0.5 mg/L | General inflammation, which rises with immune overactivation |
| Estimated glomerular filtration rate with creatinine | Above 90 mL/min/1.73 m² | Kidney signalling was the one non-immune animal finding, and function gates drug interactions |
| Age-appropriate cancer screening status | No established range; mammography, colorectal and skin screening documented as current | The tumour-promotion signal makes this the decisive safety gate |
| Epigenetic age estimate | No established target; track change from the individual's own baseline | The proposed mechanism acts on gene activity, and this is the only integrative readout available |
Cadence: Baseline before a first course; immune and clotting panels repeated at the end of each course and again at 4 to 6 weeks, then at 6 to 12 month intervals if courses continue. Anyone on insulin or an anticoagulant needs checks within the first week of every course.