CD123-directed allogeneic chimeric-antigen receptor T-cell therapy (CAR-T) in blastic plasmacytoid dendritic cell neoplasm (BPDCN): Clinicopathological insights.

Purpose: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a hematologic malignancy associated with overexpression of CD123. Allogeneic chimeric antigen receptor T cells (CAR-T) directed against CD123 in BPDCN have been studied in clinical trials. We performed post-mortem analysis of a patient treated with anti-CD123 CAR-T to elucidate cause of death, development of cytokine release syndrome (CRS), and tissue distribution of UCART123 cells.
Methods: A post-mortem multidisciplinary clinicopathologic analysis was performed with digital droplet polymerase chain reaction of isolated blood and tissue ribonucleic acid (RNA) to evaluate tissue distribution of infused CAR-T. Multiparameter flow cytometry for detection of CAR-T was used for whole blood samples. Cytokine levels in plasma were measured using multiplex bead assay. Gene expression profiling on isolated RNA was performed using semi-custom Nanostring immune gene panel and RNA-sequence method. RNA in situ hybridization was performed using CAR-specific probe.
Results: The patient developed severe clinical CRS refractory to corticosteroids, tocilizumab, and lymphodepletion. Despite significant reduction in BPDCN lesions, the patient passed away on day 9 of CAR-T. Autopsy results show that following lymphodepletion and UCART123 administration, the patient remained severely lymphopenic with few UCART123 cells detected, predominantly localized to spleen.
Conclusions: No definitive cause of death was determined, but we hypothesized that the patient may have succumbed to CAR-T-mediated cardiopulmonary toxicity. UCART123 cells displayed low overall distribution, with predominance in immune organs and tissues. Mechanism of CRS development is still poorly understood in patients receiving CAR-T therapy. Future directions in the field developing CD123-targeted agents in BPDCN are discussed.
Competing Interests: Disclosure of Conflict of Interest M Konopleva: Consulting/honorarium: AbbVie, Genentech, F. Hoffman La-Roche, Stemline Therapeutics, Amgen, Forty-Seven, and Kisoji. Research funding/clinical trials support: AbbVie, Genentech, F. Hoffman La-Roche, Eli Lilly, Cellectis, Calithera, Ablynx, Stemline Therapeutics, Agios, Ascentage, and Astra Zeneca. Stock options/Royalties: Reata Pharmaceutical. N Pemmaraju: Consulting/honorarium: Celgene, Stemline, Incyte Corporation, Novartis, MustangBio, Roche Diagnostics, and LFB. Research funding/clinical trials support from Stemline, Novartis, Abbvie, Samus, Cellectis, Plexxikon, Daiichi-Sankyo, Affymetrix, and SagerStrong Foundation. M Guzman: Consulting/honorarium: SeqRx. Research funding: AI Therapeutics, TemedOn, Cellectis. S Neelapu: Consulting fees or honorarium from Kite, a Gilead Company, Merck, Bristol Myers Squibb, Novartis, Celgene, Pfizer, Allogene Therapeutics, Athenex, Incyte, Precision Biosciences, Legend Biotech, Adicet Bio, Calibr, Unum Therapeutics, Bluebird Bio, Sana Biotechnology, Caribou, Astellas Pharma, Sellas Life Sciences; research funding from Kite, a Gilead Company, Bristol Myers Squibb, Merck, Poseida, Cellectis, Celgene, Karus Therapeutics, Unum Therapeutics (Cogent Biosciences), Allogene, Precision BioSciences, Acerta and Adicet Bio; royalty income from Takeda Pharmaceuticals; stock options from Longbow Immunotherapy; and patents related to cell therapy. MG Frattini: Employment and Equity ownership: Cellectis, Inc. A Garton: Employment and Equity ownership: Cellectis, Inc. J. Smith: Employment and Equity ownership: Cellectis, S.A.
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