Clinical translation of an immunomodulatory cell therapy that is designed to convert “cold” tumors to “hot”: A phase 2B trial in 3L MSS/pMMR metastatic colorectal cancer

BACKGROUND: A translational immunotherapy framework was designed to initiate sequential spatial and temporal immunomodulatory cascades using living, allogeneic, activated memory Th1 cells (AlloStim®), hypothesized to promote an immunomodulatory cascade in immunologically "cold" tumors. Microsatellite stable/proficient mismatch repair (MSS/pMMR) metastatic colorectal cancer (CRC) represents an immunotherapy-refractory "cold" tumor archetype with historically low response rates. METHODS: To evaluate this framework, a Phase 2B, single-arm, multi-center proof-of-concept trial was conducted in third-line MSS/pMMR metastatic CRC patients, utilizing overall survival (OS) as the primary endpoint. AlloStim® was administered via a sequential schedule of weekly intradermal priming and subsequent intravenous infusions over three 5-week cycles, followed by optional monthly intravenous boosters. RESULTS: Twenty-nine patients were enrolled (18 death events, 11 censored cases [37.9%]). The median OS was 16.4 months (492 days; 95% CI: 8.6-20.8 months). To account for non-proportional hazards, Restricted Mean Survival Time (RMST) evaluated at a 32-month temporal horizon demonstrated an average cohort life expectancy of 16.1 months (482 days; 95% CI: 12.3-19.8 months). Concurrently, 89% of evaluable patients met RECIST 1.1 criteria for progressive disease at Day 119, highlighting a profound survival-radiological discordance. The protocol was well tolerated; only 4% of total adverse events were ≥ Grade 3. CONCLUSION: This study provides indirect clinical observations supporting the hypothesis that an active immunomodulatory framework may elicit an encouraging survival signal and extended life expectancy in refractory metastatic MSS/pMMR CRC, despite conventional radiological progression. These findings justify evaluation in a prospective, randomized controlled trial powered to validate this translational strategy.