Immune checkpoint inhibitor anemias (ICI-A) are a rare entity which can be potentially life-threatening without prompt identification. The goal of the study is to characterize the presentation, evaluation, and outcomes of ICI therapy in early phase clinical trial setting to guide future research and to develop standardized care guidelines. Retrospective chart review of 333 patients who participated in early phase clinical trials at the University of Texas MD Anderson Cancer Center revealed four cases with ICI-A between 2016 and 2020. We identified a spectrum of four cases which included ICI-related autoimmune hemolytic anemias, hemophagocytic lymphohistiocytosis and thrombotic microangiopathy as a result of combinatory investigational therapies involving ICI. Patient presentation, evaluation, bone marrow pathology, interventions, and clinical course were reviewed. The median time to onset of hematological immune-related adverse events (heme-irAEs) in this retrospective series was 3.5 weeks (2 - 6 weeks). One patient had pre-existing untreated chronic lymphocytic leukemia. Glucocorticoids are an effective first-line treatment in most patients although most patients were not rechallenged but successfully had complete recovery and pursued further non-immunotherapy-based therapies. Cognizance of ICI-A in clinical trial setting is paramount to early recognition of heme-irAEs. Further research is needed to identify and stratify risk factors during clinical trial enrollment and optimal management strategies for immune-mediated hematologic toxicities., Competing Interests: BEN, CLE, MN and MBM have no interests declared. TAY received research funding (paid to his institution) from Artios, AstraZeneca, Bayer, Clovis, Constellation, Cyteir, Eli Lilly, EMD Serono, Forbius, F-Star, GlaxoSmithKline, Genentech, ImmuneSensor, Ipsen, Jounce, Karyopharm, Kyowa, Merck, Novartis, Pfizer, Ribon Therapeutics, Regeneron, Repare, Sanofi, Scholar Rock, Seattle Genetics, Tesaro, and Vertex Pharmaceuticals. In addition, he has received fees for consulting with Almac, Aduro, AstraZeneca, Atrin, Axiom, Bayer, Bristol Myers Squibb, Calithera, Clovis, Cybrexa, EMD Serono, F-Star, Guidepoint, Ignyta, I-Mab, Jansen, Merck, Pfizer, Repare, Roche, Rubius, Schrodinger, Seattle Genetics, Varian, and Zai Labs. CMRH received research funding from Daichii Sankyo pharmaceuticals and Aspen pharmaceuticals. AN reports research funding from NCI, EMD Serono, MedImmune, Healios Onc. Nutrition, Atterocor, Amplimmune, ARMO BioSciences, Eli Lilly, Karyopharm Therapeutics, Incyte, Novartis, Regeneron, Merck, Bristol Myers Squibb, Pfizer, CytomX Therapeutics, Neon Therapeutics, Calithera Biosciences, TopAlliance Biosciences, Kymab, PsiOxus, Immune Deficiency Foundation (Spouse), Advisory board: CytomX Therapeutics, Novartis, Kymab, Genome. Travel and accommodation expenses: ARMO BioSciences. SPP reports research funding through the institution: AbbVie, Inc., ABM therapeutics, Inc., Acepodia, Inc., Alkermes, Inc., Aminex Therapeutics, Amphivena Therapeutics, Inc., BioMarin Pharmaceutical, Inc., Boehringer Ingelheim, Bristol Myers Squib, Chugai Pharmaceutical Co., Ltd., Daichi Sankyo, Inc., Eli Lilly, Five Prime Therapeutics, Genmab A/S, GlaxoSmithKline, Helix BioPharma Corp., Incyte Corp., Jacobio Pharmaceuticals Co., Ltd., Medimmune, LLC., Medivation, Inc., Merck Sharp and Dohme Corp., Novartis Pharmaceuticals, Pieris Pharmaceuticals, Inc., Pfizer, Principia Biopharma, Inc., Puma Biotechnology, Inc., Rapt Therapeutics, Inc., Seattle Genetics, Taiho Oncology, Tesaro, Inc., TransThera Bio. DSH reports research funding from AbbVie, Adaptimmune, Aldi-Norte, Amgen, Astra-Zeneca, Bayer, BMS, Daiichi-Sankyo, Eisai, Fate Therapeutics, Genentech, Genmab, GSK, Ignyta, Infinity, Kite, Kyowa, Lilly, LOXO, Merck, MedImmune, Mirati, miRNA, Molecular Templates, Mologen, NCI-CTEP, Novartis, Pfizer, Seattle Genetics, Takeda, Turning Point Therapeutics. Travel, Accommodations, Expenses: Bayer, LOXO, miRNA, Genmab, AACR, ASCO, SITC. Consulting or Advisory Role: Alpha Insights, Amgen, Axiom, Adaptimmune, Baxter, Bayer, Genentech, GLG, Group H, Guidepoint, Infinity, Janssen, Merrimack, Medscape, Numab, Pfizer, Prime Oncology, Seattle Genetics, Takeda, Trieza Therapeutics, WebMD. Other ownership interests: Molecular Match (Advisor), OncoResponse (Founder), Presagia Inc (Advisor). SF reports research funding from AstraZeneca, Abbisko, Anaeropharma Science, Arrien Pharmaceuticals, BeiGene, BioAtla, LLC, Boehringer Ingelheim, Eli Lilly & Co., Hookipa Biotech, Huya Bioscience International, IMV, Inc., Innovent Biologics, Co., Ltd., Lyvgen Biopharm, Co., Ltd., MacroGenics, Medivir AB, Millennium Pharmaceuticals, Inc., Nerviano Medical Sciences, NeuPharma, inc., Novartis, OncoMed Pharmaceuticals, Parexel International, LLC, Sellas Life Sciences Group, Soricimed Biopharma, Inc., Tolero Pharmaceuticals, NovoCure, Turnstone Biologics, Taiho Oncology, Abbisko (other). NGD receives honoraria from BMS, Jazz Pharmaceuticals, Novartis, Incyte, Otsuka, Immunogen, Pfizer, Astellas Pharma, AbbVie. His consulting or advisory role includes Celgene, Agios, Jazz Pharmaceuticals, Pfizer, AbbVie, Astellas Pharma, Daiichi Sankyo, Novartis, Bristol Myers Squibb, Otsuka, Incyte, Karyopharm Therapeutics, Sunesis Pharmaceuticals, Amgen, Immunogen, Genentech, Servier, Syndax, Trillium Therapeutics. His research funding includes Bristol Myers Squibb, Pfizer, Immunogen, Genentech, Nohla Therapeutics, AbbVie, Astellas Pharma, Servier, Daiichi Sankyo, Novartis, Karyopharm Therapeutics, Incyte, Sunesis Pharmaceuticals, Sobi., (Copyright 2022, Nelson et al.)