Conflict-of-interest disclosure: J.G. is the chair of the response adjudication committee for, has received research funding from, served on advisory boards for, and received honoraria and funding to cover travel expenses from, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. A.R. has received research funding, served on advisory boards, and received honoraria and funding to cover travel expenses from AbbVie, AOP Orphan Pharmaceuticals, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Bristol Myers Squibb (BMS), Cogent, GSK, Incyte, and Novartis. D.H.R. has been a clinical advisory board/study steering group member (EXPLORER/PATHFINDER) for Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi; has been a study steering committee member for Cogent Biosciences; has been involved in educational events and advisory boards for Novartis; and has received author fees for Medscape cases. I.A.-T. has received research funding from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi; and has received advisory board or speaker fees from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi and Novartis. M.W.D. has received honoraria fees from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Incyte, Medscape, Sangamo, and Takeda; received consultancy fees from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, DisperSol, Fusion Pharma, Novartis, and Sangamo; received research funding from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Incyte, Leukemia & Lymphoma Society, Novartis, Pfizer, Sun Pharma Advanced Research Company, and Takeda; is part of a study management committee for Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi and Takeda; and is a case author for Medscape. T.I.G. has received consulting fees from, and is a study steering committee member for, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, BMS/Celgene, Cogent Biosciences, and Incyte. J.P. has received honorarium fees from Apellis, Alexion, AstraZeneca, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, BMS, Cogent, F. Hoffmann-La Roche, Grünenthal, Merck Sharp and Dohme, Novartis, Omeros, Samsung Bioepis, and Sobi; has served on the speakers bureau of Alexion, Boehringer Ingelheim, Chugai, Novartis, Pfizer, and Sobi; and is a study steering committee member for Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi and Omeros. A.M. has received honoraria from Takeda, Pfizer, Novo Nordisk, Behring, AbbVie, Novartis, Cilag, Janssen, and Bayer. K.M.P. has participated in advisory boards for CTI BioPharma, AbbVie, Protagonist Therapeutics, PharmaEssentia, and Kura Oncology. A.M.V. serves on advisory boards for, and has received fees for lectures from, Incyte, Novartis, GSK, AOP Orphan Pharmaceuticals, and Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. U.P. received research funding and honoraria from Amgen, Janssen, Jazz, and Novartis. O.H. received research funding from AB Science, BMS-Celgene, Alexion, Novartis, and Inatherys; has consulted for AB Science; and is a shareholder for AB Science. A.E. received compensation for his participation on the speakers bureau of Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. C.B.L. has received consultancy fees from Lilly, Novartis, and UCB; has received research support from Novartis; and is a nonpaying member of the steering committee for an AB Science study. R.M. has been a consultant for Novartis, Sobi, GSK, BMS, Incyte, and PharmaEssentia; has received research support from Celgene, Incyte, AbbVie, Samus, Genetech, Promedior, and CTI BioPharma. C.U. reports compensation for their role on the speakers bureau from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi and Takeda; serves on the advisory board for Cogent; and holds a nonpaid role for the Mastocytosis Society. M.T. has received fees for advisory boards from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Deciphera, and Novartis. I.D. has received advisory board fees from Novartis and Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. J.G.J. receives research funding paid to Columbia University from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, BMS, Forma Therapeutics, Gilead/Forty Seven, Seagen/Pfizer, and Sumitomo Pharma; serves on advisory boards for Gallop Oncology and Syros Pharmaceuticals; and serves as consultant for Incyte and Rigel Pharmaceuticals. R.Z. reports compensation from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi for meeting participation; and has acted as consultant for Istituto Gentili. S.T.O. has been a consultant for Disc Medicine, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, AbbVie, Constellation, CTI BioPharma, BMS, Geron, Sierra Oncology, Cogent, and Incyte. A.Y. has served on advisory boards for Incyte, CTI BioPharma, PharmaEssentia, Pfizer, Novartis, Acceleron Pharma, Servier, AbbVie, Apellis, Gilead, Notable Labs, and Celgene. E.O.H. has received research support (to institution) from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Disc Medicines, and AbbVie Oncology; serves on a data safety monitoring committee for Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi; and is a member of the hematology examination committee for the American Board of Internal Medicine. P.B. has received research support from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Celgene (now BMS), Constellation (now MorphoSys), Cogent, CTI BioPharma (now Sobi), Incyte, Ionis, Kartos, Telios, Disc Medicine, Geron, Janssen, and Sumitomo Oncology Pharma; and has received honoraria from AbbVie, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Celgene (now BMS), Cogent, Constellation (now MorphoSys), CTI BioPharma (now Sobi), Incyte, Karyopharm, Sumitomo, Morphic, Jubilant, Novartis, PharmaEssentia, and GSK. S.G.L. has received honoraria from Medison; has served on advisory boards for Medison, Novartis, and Forus Therapeutics Inc. W.R.S. has received honoraria, scientific grants, or travel support from AbbVie, Astellas, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, BMS-Celgene, Daiichi Sankyo, Deciphera, Incyte, Jazz, Laboratoires Delbert, Novartis, Otsuka, Pfizer, Servier, Stemline, and Thermo Fisher. E.A.G. has received honoraria with direct payments from The Aplastic Anemia and MDS International Foundation, American Society of Hematology, MDS International Foundation, MediCom Worldwide, Physician Educational Resource, Picnic Health, and WebMD; reports consulting or advisory board participation with direct payments/in kind contributions from AbbVie, Alexion Pharmaceuticals, AstraZeneca Rare Disease, Genentech, Novartis, Apellis, Celgene/BMS, Servier Pharmaceuticals, Takeda Oncology, and Taiho Oncology; and reports research funding to Roswell Park Comprehensive Cancer Center from Alexion Pharmaceuticals, Astex Pharmaceuticals, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Celldex Therapeutics, Celgene/BMS, Genentech Inc, and NextCure Therapeutics. J.L has received honoraria from Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. I.B., H.-M.L., S.R., S.D., and J.I.M.-G. are employees of Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi. D.J.D. has served as a consultant for Amgen, Autolus, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, Gilead, Kite, Jazz, Novartis, Pfizer, Servier, and Takeda; and received research funding from AbbVie, Blueprint Medicines Corporation, a wholly owned subsidiary of Sanofi, GlycoMimetics, and Novartis. M.B. declares no competing financial interests.