CEL-SCI Corporation announced that the latest results from its pivotal Phase 3 study of Multikine, a presurgical cancer immunotherapy, were presented at the European Society for Radiotherapy and Oncology (ESTRO) 2023 Congress in Vienna, Austria in a poster presentation titled “Histopathology population (HPP) confirms Multikine* [Leukocyte Interleukin Injection (LI)] treatment (Tx) outcome in naïve locally advanced primary head & neck squamous cell carcinoma SCCHN)” during the Head & Neck Cancer Session on May 13, 2023. CEL-SCI's IT-MATTERS pivotal Phase 3 study, the largest study ever conducted in newly diagnosed locally advanced squamous cell carcinoma of the head and neck, reported a statistically significant 14.1% absolute 5-year overall survival benefit in the intent to treat (ITT) subjects who were categorized as lower risk to recurrence (LR) per National Comprehensive Cancer Network (NCCN) guidelines and received Multikine followed by surgery and radiotherapy, as compared to control LR subjects who received only standard of care (SOC) (surgery plus radiotherapy). The ESTRO presentation focused on pathology analysis of Phase 3 patients' tumors at surgery.

In summary, it confirmed that Multikine pre-surgery treatment led to significant changes in the tumors of the patients treated with Multikine and that these changes were not seen in control patients who did not get Multikine. The tumor tissue and biomarker analyses demonstrated that these changes were statistically significant and important in bringing about the beneficial responses seen. The tumor and tumor microenvironment changes induced by Multikine explain the increased survival, improved progression free survival, and improved local regional control, as well as the significantly lowered death rate compared to control subjects in the study.

These findings from the Phase 3 study also confirm Multikine's mechanism of action which was previously determined from samples collected during Phase 2 studies from Multikine treated subjects. The results from the Phase 2 studies were previously reported in the Journal of Clinical Oncology(Timar et al). The ESTRO presentation reported that patient responses to Multikine were determined following 3 weeks of Multikine treatment by comparing baseline tumor/lymph node measurements at screening (per RECIST) with tumor/lymph node measurements made just prior to and confirmed by pathology following surgery.

Histopathology (HP) samples (n=453), were representative of the study ITT population (n=923) in all manner of subjects' characteristics, and showed that: Multikine treated subjects had a different tumor and tumor microenvironment cellular profile at surgery than that exhibited by SOC (control) treated subjects. This was determined by pathologists who were blinded to the study using predefined low/high thresholds for 20 biomarkers (5 tumor, 15 tumor microenvironment). The histopathology analysis showed association with improved overall survival, progression free survival and local regional control that significantly favored Multikine-treated [(61/279 or 21.9% >> 2.5% by chance alone) vs SOC-treated (5/279 (or 1.9% < 2.5% by chance alone)] (conditional binomial; p<0.0001).

HP LR Multikine-treated vs HP LR SOC 5-year efficacy measures of success were: Overall Survival of 63.9% vs 44.4% (hazard ratio: 0.64 [95% CI 0.41, 1.01]), Progression Free Survival of 56.9% vs 41.1% (hazard ratio 0.67 [95% CI 0.44, 1.02]), Local Regional Control of 73.1% vs 63.6% (hazard ratio 0.62 [95% CI 0.35,1.09]), HP LR Multikine-treated subjects had a significantly lower (39.1% [45/115]) death rate versus a 53.7% (51/95) death rate for HP LR SOC alone (two-sided Fisher Exact Test p=0.038), These statistical results for the HP LR analyzed subjects are supportive of the efficacy advantages demonstrated for LR Multikine-treated vs LR SOC alone treated patients in the Phase 3 study.