A Phase I/II Trial Evaluating the Use of a Histone Deacetylase Inhibitor Panobinostat (LBH589) in Addition to Glucocorticoids in Patients with Acute Graft-Versus-Host Disease
Authors: Perez Lia , Field Teresa , Riches Marcie L , Fernandez Hugo F , Locke Frederick L , Betts Brian C , Pidala Joseph , Elmer Erika , Beato Francisca , Lienlaf Maritza , Horna Pedro , Villagra Alejandro , Anasetti Claudio 
Published: October 2019

Abstract
Graft-versus-host disease (GVHD) remains the principal obstacle to successful outcomes in allogeneic hematopoietic stem cell transplant (HCT). Glucocorticoids are the current standard initial treatment for acute GVHD with variable complete responses rates (30% to 60%). New immunosuppressive strategies are required to improve survival and to decrease immunosuppressive toxicities. Vorinostast, a histone deacetylase inhibitor (HDACi), have shown efficacy for acute GVHD prevention in MRD HCT. Panobinostat is a potent inhibitor of deacetylases and HSP90 belonging to a structurally novel class of the cinnamic hydroxamic acid class and is one of most potent pan-HDACi. This protocol tested the safety and efficacy of Panobinostat (LBH589) as initial adjunct treatment for acute GVHD, administered within 72 hours of the first high dose glucocorticoid (methylprednisolone 0.8 mg/Kg/day IV or equivalent PO for 14 days and then taper per MD discretion). We have enrolled 19 subjects, median age 53 years (range, 34-76), male (n=12)/female (n=7), white(n=14)/hispanic(n=5); with diagnosis of CLL (n=2), MDS (n=2), Myeloma (n=1), Follicular NHL (n=1), CML(n=1), Myelofibrois (n=3), AML (n=5), MDS/CMML (n=3) or ALL(n=1). Conditioning regimens included Busulfan(BU)/fludarabine(FLU) AUC 5300 (n=10) or AUC 3500 (n=3), FLU/Melphalan (n=4) or Pentostatin/BU (n=2); and GVHD prophylaxis for MUD 8/8 (n=11) or MRD (n=5) HCT with TAC/MTX (n=6), TAC/rapamycin(n=7), TAC/MMF(n=3) and for mismatched transplants with either TAC/RAPA/ATG (n=2) or TAC/MTX/ATG (n=1). Median day of acute GVHD (n=16) onset was day + 37 post HCT (26 -109 days) with overall grade GVHD II (n=13) or III (n=6); and median day of acute symptoms in overlap GVHD patients (n=3) was day + 712 (528-981). All Patients were treated with voriconazole (n=15) or micafungin (n=4) for fungal prophylaxis. For the first four patients Panobinostat was administered intravenously (IV) weekly x 4 at 2.5MG/M2 (n=3) or 5MG/M2 IV (n=1) with all 4 achieving either CR (n=3) or PR (n=1) GVHD responses by day +15 of Panobinostat. Due to manufacturer discontinuation of IV formulation, the protocol was amended to use PO Panobinostat. Using 10mg PO TIW 3 doses q week x 4 weeks, we treated 2 subjects which were both discontinued from study drug due to presumed GHVD progression within 7 days of Panobinostat (after 3-4 doses). First subject had grade II GVHD (skin stage 3, gut stage 1 and liver stage 0) that progress in gut and skin; second subject with grade II GVHD (skin stage 3, gut stage 1, liver stage 1) with LFTs worsening ultimately evolving into VOD. Due to safety concerns next subjects were treated with 5 mg PO TIW 3 doses q week x 4 weeks, dose that was determined to be the maximal tolerated dose (MTD) after 6 patients completed therapy in phase I. Currently we are enrolling in phase II portion (n=7). GVHD response rate among MTD treated was complete in 85% (n=11), partial in 7.6% (n=1) or progressive in 7.6% (n=1) by day +36 after Panobinostat with majority achieving responses by day +21. Chronic GVHD at day +365 in evaluable patients (n=6) was none (n=3) or mild (n=3) and steroid was discontinued at a median of 3 months (3-6). Hematological toxicities in evaluable patients (n=13) were mild with worsening of prior thrombocytopenia (n=7/10), anemia (n=3/10) and leukopenia (n=3/10) and returned to baseline within 1-2 weeks; LFTs deterioration (n=1) within 1 week of Panobinostat in a GVHD stages 3 liver/3 skin patient; pericarditis/cardiogenic shock CTCAE 5 of unclear etiology (n=1); worsening thyroid function (n=1) and hypercholesterolemia (n=1). Preliminary correlative studies in MTD treated patients showed that CD4 and CD8 numbers remained stable during treatment. T regulatory cells numbers decreased at day +8 after Panobinostat and recovered by days +15 and +29 of treatment. Level of T regs inducing cytokines (TGFB and IL-10) increased, possibly contributing to an immune-modulatory environment. There is evidence of an increased in acetylation of histone 3 in CD4, CD8 and monocytes subsets over time. We are encouraged with tolerability of level -1 Panobinostat dose and the high GVHD response rate of 85% which may compare favorably to the historical GVHD response rate. These results suggest a potential role for Panobinostat as a tool to improve success of glucocorticoids for acute GVHD treatment.

Disclosures
No relevant conflicts of interest to declare.