Dennis Sun is Co-Founder at Ditto Bio (YC W26), a biotech company discovering drugs for autoimmune diseases by harnessing parasite biology. The company uses AI to identify proteins from parasites that can calm hyperactive immune systems.

Dennis earned his PhD in Molecular & Cellular Biology from UC Berkeley with a focus on computational and genomic biology, and his BA in Human Developmental and Regenerative Biology from Harvard. He was an NSF Graduate Research Fellow and graduated magna cum laude with high honors from Harvard.

Dennis previously served as Chief of Staff to the CEO at Arcadia Science, where he led product management and strategic initiatives. He founded the Harvard College Writers' Workshop and was Editor-in-Chief of the award-winning Mt. Carmel Sun newspaper.

Ditto Bio is part of Y Combinator's Winter 2026 batch and is developing therapeutics for conditions including rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and other autoimmune diseases. The company leverages millions of years of parasite evolution to identify immunomodulatory proteins.

Ditto Bio's AI platform screens proteins from viruses, ticks, and worms that have evolved to control the human immune system. The company is targeting the autoimmune disease market, which affects millions of patients worldwide with limited treatment options.