Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a particularly aggressive hematologic malignancy with median survival of 80% bone marrow blasts. His BPDCN carried the mutations ASXL1 Y581fs*, ASXL1 E553fs*, GNB1 K57E, IDH2 R140W, and NRAS G12D, and expressed high levels of BCL-2 protein in bone marrow and skin. BH3 profiling of a skin tumor biopsy revealed marked BCL-2 dependence and dynamic BH3 response to venetoclax (4 hr delta priming 55.6%). We treated him using a regimen recently FDA-approved for chronic lymphocytic leukemia (CLL) consisting of weekly dose escalation (20 -> 50 -> 100 -> 200 mg), to a target dose of 400 mg daily. At the time of this writing, he had reached 200 mg without significant toxicity, including no evidence of tumor lysis syndrome. His skin disease has responded remarkably (Figure), with the first response evident within 10 days. Our data suggests that BPDCN is highly sensitive to BCL-2 inhibition, which could provide an urgently needed new treatment for patients with this disease. We propose that BCL-2 inhibition should undergo expedited clinical evaluation in BPDCN. In addition, this case offers an example of precision cancer medicine by functional rather than genetic means. Disclosures Davids:Infinity: Honoraria, Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Gilead: Honoraria; Janssen: Consultancy, Honoraria; Pharmacyclics: Consultancy, Honoraria, Research Funding; TG Therapeutics: Honoraria, Research Funding; Abbvie: Consultancy, Honoraria. Stone:ONO: Consultancy; Novartis: Consultancy; Amgen: Consultancy; Seattle Genetics: Consultancy; Roche: Consultancy; Celator: Consultancy; Abbvie: Consultancy, Membership on an entity9s Board of Directors or advisory committees; Agios: Consultancy; Celgene: Consultancy, Membership on an entity9s Board of Directors or advisory committees; Karyopharm: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; Juno Therapeutics: Consultancy; Merck: Consultancy; Sunesis Pharmaceuticals: Consultancy; Xenetic Biosciences: Consultancy. Konopleva:Reata Pharmaceuticals: Equity Ownership; Abbvie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Stemline: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Calithera: Research Funding. Letai:AbbVie: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Research Funding; Tetralogic: Consultancy, Research Funding. Lane:N-of-1: Consultancy; Stemline Therapeutics: Research Funding.