2605 Background: Previously we reported that peritumoral administration 5/week, 2 weeks, cumulative doses 2400, 4800, 8000 IU [as IL-2] of LI [Multikine] increased cancer cells sensitivity to radiation in 27 oral squamous cell carcinoma (OSSC T2–3N0–2M0) patients (p<0.05) resulting in tumor cells entering cell cycle with no recurrence at 24 months in 8/27 LI-treated patients (data to date) as opposed to controls. Treatment regimen included LI (above) single low-dose cyclophosphamide (iv 300mg/m2) indomethacin (po 25mg tid) and Zinc Sulfate (po 50mg) [CIZ]. Methods: Paraffin embedded samples obtained at surgery from 19 LI-treated patients (different cohort of OSSC T2–3N0–2M0) receiving LI (800IU/mL) \(\frac{1}{2}\) peritumorally \(\frac{1}{2}\) perilymphatically (5/week for 3 weeks + CIZ) were compared to 20 disease-matched (non-LI treated) controls. All patients had surgery & radiation. Histology, necrosis, AJCC grading was scored from H&E. Immunohistochemistry evaluated three tumor regions (surface, center, tumor-stroma interface). Trichrome stain visualized connective tissue. Morphometry by ImagePro software. All by 3 pathologists blinded to Study. Results: LI treatment induced a shift from stromal T cells to tumor epithelia (p<0.05) increase in intraepithelial CD3+ CD25+ CD4+ T cells and decrease in CD8+ T cells (p<0.05) causing a shift from low (<1) to high (>2.5–3) intra-tumoral CD4/CD8 ratio. Stroma/cancer-nest ratio showed reduction of cancer cells (LI-treated, p<0.005) as compared to control. LI-treated had 2/19 complete responders, 2/19 partial responders (>50%), and 4/19 minor responders (>30% but <50%). Conclusions: Objective response 21% overall response 42%. The results may be highly beneficial to OSCC patients: LI treatment induced CD3+ CD25+ CD4+ T cell increase in cancer nests including significant (p<0.005) decrease in tumor epithelia compared to control. Non-cycling cancer cells entered cell cycle following LI treatment increasing tumor susceptibility to radiation (p<0.05). LI-treatment appears to cause an increase in the local control of OSSC. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration CEL-SCI Corp. CEL-SCIU Corp. CEL-SCIU Corp.