SMR3B (submaxillary gland androgen-regulated protein 3B) is a salivary secretory protein with emerging roles in cancer biology and inflammatory diseases. As a member of the opiorphin gene family, SMR3B functions as an endopeptidase inhibitor with potential regulatory roles in pain perception and sensory processing 1. The protein is secreted into extracellular compartments and is detectable in saliva, where it serves as a biomarker for various pathological conditions. In cancer biology, SMR3B has been identified in fusion transcripts associated with salivary gland malignancies. A MYB::SMR3B fusion was detected in a recurrent, high-grade secretory carcinoma case, expanding the molecular spectrum beyond the typical ETV6::NTRK3 fusion 23. Additionally, SMR3B is upregulated in periodontitis-affected individuals and their offspring, positioning it as a potential early biomarker for this inflammatory disease 4. Salivary SMR3B peptides were validated as part of a five-protein signature panel achieving 80% sensitivity and 95% specificity in distinguishing triple-negative breast cancer patients from healthy controls 5. SMR3B is also significantly altered in symptomatic SARS-CoV-2 infection compared to asymptomatic cases 6. Furthermore, opiorphin genes including SMR3B are overexpressed in prostate cancer and promote development of androgen-insensitive tumors 7. These findings suggest SMR3B functions in oncogenic pathways and inflammatory responses with potential therapeutic relevance.