Administration of Third-Party Virus-Specific T-Cells (VST) at the Time of Initial Therapy for Infection after Haemopoietic Stem Cell Transplant Is Safe and Associated with Favourable Clinical Outcomes (the R3ACT-Quickly trial)

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Background Administration of partially HLA-matched third party virus-specific T cells (VST) from a cryopreserved cell bank is safe and effective after failure of standard antiviral therapy to resolve viral infection occurring after allogeneic stem cell transplantation (HSCT). Aim In this phase I trial, we assessed the safety and efficacy of administering partially HLA-matched third party VST at the time of initial antiviral therapy following HSCT rather than waiting for failure of at least two weeks of standard antiviral treatment. Methods A cryopreserved cell bank of VST directed at cytomegalovirus (CMV), Epstein Barr virus (EBV) or adenovirus (Adv) was established using G-CSF mobilised peripheral blood from healthy stem cell donors. After stimulation with peptide mixes, VST were selected by expression of CD137+ cells and cultured with cytokines. HSCT recipients were treated with up to 4 doses of 2x107 of VST/m2, the first commencing within 7 days of initial antiviral treatment for viral reactivation. Results A total of 188 doses of VST were manufactured from 7 donors with 12 product manufacturing runs (CMV n=3, EBV n=4 and Adv n=5). Median virus specificity was 75% for CMV, 83% for EBV and 37% for Adv. Thirty HSCT recipients were treated with VST a median of 55 days post-transplant. Data from 25 patients treated for initial viral reactivation were available for analysis (CMV n=22, EBV n=2, Adv n=1). Median age was 58 years (0-71). Patients underwent transplant for myeloid malignancies (n=16), lymphoid malignancies (n=5) and non-malignant conditions (n=4). Patients with malignant disease were transplanted in CR1 (n=8), CR2 (n=3), >CR2 (n=3) or with active disease (n=7). Conditioning was myeloablative in 11 patients and reduced intensity in 14 patients. Donors were matched unrelated (n=20), haploidentical (n=4) or siblings (n=1). 21 patients received some form of T cell depletion (most commonly pre-transplant thymoglobuline in vivo). All patients received VST within 7 days of commencing initial antiviral therapy. 18 patients received a single VST infusion, 6 received 2 and 1 received 4 VST infusions. There were 3 mild infusion related adverse events (vomiting, hypertension, fever). 3 patients had aGVHD pre-infusion (2 grade 1 skin, 1 grade 3 GI). Two patients died of acute GVHD (1 patient with resolved grade 3 GI GVHD pre-VST infusion developed grade 4 GI GVHD 89 days post- infusion as immunosuppression was weaned; the other patient developed de novo liver and GI GVHD 30 days post infusion in the context of a rapid wean in immunosuppression for severe BK virus haemorrhagic cystitis). 2 patients developed de novo grade 1 GVHD post-infusion. 2 patients developed mild limited cGVHD and 1 patient developed extensive cGVHD after VST infusion. 23/25 patients (92%) had complete viral clearance of the infection for which VST were given, 2 had a partial viral response. Median time to best viral response was 20 days. There were 5 deaths (refractory aGVHD in 2 patients, pulmonary VOD/CMV pneumonitis, disease relapse, and sepsis/aspiration pneumonia). 4 of 25 patients died within 12 months of transplant for a 1 year NRM of 12%. At a median follow up of 431 days (112-1391) post-transplant, 20 of 25 patients (80%) remain alive (Figure 1). Conclusion Infusion of third party partially HLA-matched donor-derived VST at the time of first antiviral treatment for CMV, EBV and Adv post HSCT is associated with minimal infusion toxicity, a low rate of moderate to severe GVHD and complete viral clearance in 92% of recipients. Overall survival in this group of high-risk patients requiring treatment for viral reactivation after HSCT is high. A randomised trial will be performed to determine whether administration of third-party VST in addition to standard anti-viral treatment improves transplant outcomes. Figure 1 Disclosures Gottlieb: Haemalogix P/L: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy; Gilead: Consultancy; AbbVie: Consultancy; University of Sydney: Employment; Merck: Consultancy. Ritchie:Amgen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy; BMS: Research Funding; Takeda: Research Funding; Beigene: Research Funding; Imago: Research Funding; Novartis: Honoraria; Sanofi: Honoraria.

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