Biomimetic phospholipid nanoparticles effectively deliver OX40 mRNA to tumor-infiltrating T cells with increased OX40 expression, thus potentiate the therapeutic effect of anti-OX40 mAbs against tumor. (a) Illustrated is the mechanism of PL1-OX40 mRNA nanoformulation for enhanced cancer immunotherapy of anti-OX40 mAbs. (b–d) Shown are the experimental timeline of B16F10 tumor bearing mice received different treatments as indicated (b), tumor growth profiles and survival curves of mice with primary tumor (c), and tumor sizes of rechallenged mice (d). (e) The percentages of CD8+, CD4+ T cells and Tregs infiltrated in A20-tumor derived from mice received different treatments as shown [98]. Reproduced under the terms of the Creative Commons CC BY license. Copyright 2021, The Author(s), published by Springer Nature.