Background. GVHD is a frequent complication within the 1st year after allogeneic stem cell transplantation (allo-HCT). Recipients of reduced intensity (RI) and non-myeloablative (NMA) conditioning combined with calcineurin inhibitor (CNI)-based GVHD prophylaxis, frequently develop GVHD in the context of immunosuppression taper. Ixazomib is an oral proteasome inhibitor (PI) that has demonstrated immunomodulatory properties, inhibition of pro-inflammatory cytokines, anti-tumor activity, and has a wide safety profile. We hypothesized that secondary GVHD prophylaxis using ixazomib, will facilitate CNI taper without increase in GVHD frequency and severity, maintaining graft-versus-tumor (GVT) effect, and a safety profile.

Methods. We conducted an open label, prospective, single-center pilot study between 11/16 and 03/19. Eligible patients were > 18 yrs old, had a hematologic malignancy treated with RI or NMA conditioning allo-HCT, received CNI-based GVHD prophylaxis, and were within day 100 to 150 post-HCT. Patients with active acute and/or chronic GVHD were excluded. Patients were treated with ixazomib 4 mg orally once weekly, each cycle consisting of 3 weeks on and 1 week off therapy, until completion of taper from prophylactic CNI or 1-year post-HCT was reached, whichever occurred first. Patients who developed grade II-IV acute GVHD, chronic GVHD, or died of transplant-related mortality (TRM) were deemed treatment failure. The primary endpoint was the efficacy of ixazomib for the prevention of recurrent or late grade II-IV acute GVHD or chronic GVHD at 1-year post-HCT. Additional endpoints included TRM, relapse rate, survival analysis, safety evaluation, and immune reconstitution.

Results. A total of 18 patients (median age of 58 yrs) were accrued in the study. The majority were male, had a diagnosis of NHL, and received RI conditioning (Table 1). All patients had a PBSC graft, and 16 (89%) were 10/10 HLA-matched. The median time for initiation of ixazomib was 141.5 days post-HCT. Fourteen patients had no GVHD during the study period. The 4 patients who developed GVHD had severe overlap syndrome (n = 2), mild de novo chronic GVHD (n = 1), and recurrent grade II acute GVHD (n = 1). Notably, patients with severe overlap syndrome had limited chronic GVHD involvement affecting the mouth and/or eyes, and the severity score was driven by acute manifestations affecting the skin and GI tract. Six patients successfully discontinued CNI and 4 patients were tapering immunosuppression close to the end of study at 1-year post-HCT. The cumulative incidence (CI) of grade II-IV acute and chronic GVHD at 1-year post-HCT was 25% (95%CI: 7.2-48.1) (Fig. 1A). No patients died during the study and therefore, the CI of TRM at 1-year was 0%, and only 1 patient had malignant relapse (NHL). The CI of PFS and the composite endpoint GVHD-free/relapse-free survival (GRFS) at 1-year were 83% (95%CI: 58-100) and 73% (95%CI: 49-100, Fig 1B), respectively. All patients experienced at least 1 TEAE of any grade. Most AEs were grade 1 or 2, with the most common being cytopenia and elevation in ALT/AST. Drug-related SAEs were reported in 9 patients and included neutrophil and decreased WBC. Seven patients required ixazomib dose reduction due to side effects, and 5 patients were removed from the study due to toxicity (1 neutropenia, 3 GI, 1 skin rash). Of those, 1 had subsequent GVHD by day 365 post-HCT. Immune recovery at 3, 6 and 12 months post-HCT was evaluated. There was a rapid and sustained recovery in T-cell subpopulations and B cell reconstitution Fig 2.

Conclusions. Secondary GVHD prophylaxis with ixazomib was associated with low incidence of recurrent and late acute and chronic GVHD within the 1st year post-HCT. This approach allowed CNI taper while preserving GVT effect without aggravating GVHD. No deaths occurred during the study period and the 1-year GRFS was high. Ixazomib was overall well tolerated and favored immune reconstitution post-HCT. Our findings support further development of this approach and provide a proof-of-concept for secondary GVHD prophylaxis.

Disclosures

Dahi:Kite: Consultancy. Giralt:TAKEDA: Research Funding; JAZZ: Consultancy, Honoraria; CELGENE: Consultancy, Honoraria, Research Funding; AMGEN: Consultancy, Research Funding; MILTENYI: Consultancy, Research Funding; KITE: Consultancy; NOVARTIS: Consultancy, Honoraria, Research Funding; OMEROS: Consultancy, Honoraria; ACTINUUM: Consultancy, Research Funding. Sauter:Bristol-Myers Squibb: Research Funding; GSK: Consultancy; Gamida Cell: Consultancy; Celgene: Consultancy, Research Funding; Kite - a Gilead Company: Consultancy; Precision Biosciences: Consultancy, Research Funding; Genmab: Consultancy; Novartis: Consultancy; Spectrum Pharamaceuticals: Consultancy; Sanofi-Genzyme: Consultancy, Research Funding; Juno Therapeutics: Consultancy, Research Funding. Perales:Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Medigene: Membership on an entity's Board of Directors or advisory committees, Other; NexImmune: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Other; Cidara Therapeutics: Other; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Miltenyi Biotec: Research Funding; Kite/Gilead: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; MolMed: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ponce:Ceramedix: Membership on an entity's Board of Directors or advisory committees; Generon: Membership on an entity's Board of Directors or advisory committees; Kadmon: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding.

Author notes

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Asterisk with author names denotes non-ASH members.