MIT researchers engineered polymer‑coated nanoparticles that concentrate and release interleukin‑12 (IL‑12) within ovarian tumors, dramatically boosting responses to checkpoint inhibitors in mice. Published in Nature Materials, the study reports elimination of metastatic disease in over 80% of treated animals and durable immune memory on rechallenge. The targeted cytokine delivery design reduced systemic toxicity and may enable clinical translation of potent but previously too‑toxic immunostimulatory cytokines.