ASTCT Consensus Recommendations on Testing and Treatment of Patients with Donor-specific Anti-HLA Antibodies.

Donor-specific anti-HLA antibodies (DSA) are an important cause of engraftment failure and may negatively impact survival outcomes of patients receiving allogeneic hematopoietic stem cell transplantation (HSCT) using an HLA-mismatched allograft. The incidence of DSA varies across studies, depending on individual factors, detection or identification methods and thresholds considered clinically relevant. Although DSA testing by multiplex bead arrays remains semiquantitative, it has been widely adopted as a standard test in most transplant centers. Additional testing to determine risk of allograft rejection may include assays with HLA antigens in natural conformation, such as flow cytometric crossmatch, and/or antibody binding assays, such as C1q testing. Patients with low level of DSA (<2,000 mean fluorescence intensity; MFI) may not require treatment, while others with very high level of DSA (>20,000 MFI) may be at very high-risk for engraftment failure despite current therapies. By contrast, in patients with moderate or high level of DSA, desensitization therapy can successfully mitigate DSA levels and improve donor cell engraftment rate, with comparable outcomes to patients without DSA. Treatment is largely empirical and multimodal, involving the removal, neutralization, and blocking of antibodies, as well as inhibition of antibody production to prevent activation of the complement cascade. Desensitization protocols are based on accumulated multicenter experience, while prospective multicenter studies remain lacking. Most patients require a full intensity protocol that includes plasma exchange, while protocols relying only on rituximab and intravenous immunoglobulin may be sufficient for patients with lower DSA levels and negative C1q and/or flow cytometric crossmatch. Monitoring DSA levels before and after HSCT could guide preemptive treatment when high levels persist after stem cell infusion. This paper aims to standardize current evidence-based practice and formulate future directions to improve upon current knowledge and advance treatment for this relatively rare, but potentially serious complication in allogeneic HSCT recipients.

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Copyright © 2024. Published by Elsevier Inc.

Déclaration de conflit d'intérêts

Declaration of competing interest PK - none for this work; other COI - consulting for CareDx and reseach funding from Eurofins Viracor PV - none declared JZ - none declared SS - none declared BS - none declared RMS - none declared AV - none declared JM - none for this work; other COI - honoraria from Kite, AlloVir, Bristol Myers Squibb, Novartis, CRISPR, Nektar Therapeutics, Caribou Bio, Sana Technologies, Legend Biotech and Cargo Therapeutics. BRD - none declared SRM – none declared AED - none for this work; participated in advisory boards, and/or had a consultancy with and received honoraria from Celgene/BMS, Agios, Regeneron, Sobi, Novartis, Astellas, Gilead. AED served on clinical trial steering committees or DSMB for Novartis, Abbvie, Kura, Geron and Celgene/BMS. NB – none for this work; consulting, advisory role or research funding with Magenta Therapeutics, Medexus Pharmaceuticals, CTI BioPharma, CareDx Pharma, Orca Bio, Allovir and CRISPR Therapeutics. AB – none declared SF – none declared LC – none declared JM – none declared AR - none declared RB - none for this work; travel & accommodation: Pfizer, Jazz Pharmaceuticals, Gilead Sciences, Sanofi. Research Funding: Jazz Pharmaceuticals. Speaker: Pfizer, Gilead Sciences. TT – none declared XH - none declared CB – none declared FA – none declared KC – none declared PAC – none for this work; consulting or advisory roles and/or research funding with Incyte, AbbVie and Sanofi MH - none for this work; research support/funding from ADC Therapeutics; Spectrum, Pharmaceuticals; Astellas Pharma, consultancy for ADC Therapeutics, Omeros, BMS, Kite, Abbvie, Genmab, Allovir, CRISPR, Caribou, Autolus, Forte Biosciences, and speaker's bureau for ADC Therapeutics, AstraZeneca, Kite, Beigene MA – none for this work; director clinical services, Be The Match/National Marro Donor Program (NMDP), Minneapolis, MN MFV – none declared AG – none declared SOC – none for this work; reports participation is advisory board for Hansa Therapeutics, CardDx, Spetrum/Achrotech, Kiadis Pharma, Magenta, Allogene, Cellularity, MolMed, Pharmacyclics and received research funds from Miltenyi and Kiadis Pharma.