Rochester, Minnesota Clinical Profile


The research focus of Harry H. Yoon, M.D., is in the development of biomarkers and therapies in esophagogastric and colorectal malignancies. Clinically, he specializes in cancers that spread from an unknown location (cancer of unknown primary).

Focus areas

  • Human epidermal growth factor receptors (HER2 and HER3). Dr. Yoon developed the largest clinically annotated, tissue-based cohort of esophageal and gastroesophageal junction (GEJ) adenocarcinomas in the world. Using this unique resource, the team found that the clinical impact of the HER2/ERBB2 gene aberrations differ based on the presence of premalignant lesions and that tumors with HER2 genetic heterogeneity display particularly aggressive behavior. His team determined that HER3/ERBB3, a potential therapeutic target that partners with HER2, is frequently overexpressed in esophageal and GEJ tumors and tends to be coexpressed with HER2. This supports the concept of dual-targeting of HER2 and HER3.
  • Ramucirumab, an angiogenesis inhibitor. Dr. Yoon is principal investigator of an investigator-initiated U.S.-based randomized phase II trial examining the effects of ramucirumab in people with previously untreated, advanced esophagogastric adenocarcinoma. Ramucirumab is a monoclonal therapeutic antibody targeting vascular endothelial growth factor receptor 2 (VEGFR-2). In addition, Dr. Yoon is principal investigator of multiple studies to identify tissue, genetic and plasma-based biomarkers that predict ramucirumab benefit.

Significance to patient care

In a trial at Mayo Clinic, patients with previously treated esophagogastric cancers with equivocal or strong HER2 expression received additional treatment regardless of HER2 gene amplification status. These patients were given a novel HER2- and HER3-targeted bispecific antibody, in addition to standard chemotherapy.

Dr. Yoon has also led a ramucirumab study focused on VEGFR-2, the most important receptor involved in tumor-related blood vessel formation. Tumors are unable to grow unless they can continue to coax blood vessels to supply nutrition, and the objective of ramucirumab is to deprive tumors of this blood supply. This study is the only one in the world examining ramucirumab in esophagogastric cancer in the front-line setting. Additionally, ramucirumab was shown to improve overall survival in two phase III trials (known as REGARD and RAINBOW) in patients with previously treated advanced cancer of the upper gastrointestinal tract.

Professional highlights

  • Young Investigator Award, American Society of Clinical Oncology
  • Charles F. and Marcia L. Forcey Career Development Award in Esophageal Cancer Research
  • Paul Calabresi Scholar (Mayo Clinic Cancer Center K12)
  • Former junior member, National Cancer Institute Gastrointestinal Intergroup, Gastrointestinal Steering Committee


See my publications


Primary Appointment

  1. Gastroenterology

Academic Rank

  1. Assistant Professor of Oncology


  1. Clinical Post Doctoral Fellowship - Medical Oncology The Johns Hopkins University School of Medicine
  2. MHS Graduate Training Program in Clinical Investigation (GTPCI), Johns Hopkins School of Public Health
  3. Internship/Residency - Internal Medicine Traditional Program, Yale-New Haven Hospital, Yale University School of Medicine
  4. MD Yale University School of Medicine
  5. BS - Molecular Biophysics & Biochemistry Yale College

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