Alpha 1 Anti-Trypsin (AAT) Offers Potent Therapy for Steroid Resistant Gut Gvhd: Interim Results of a Phase I/II Clinical Study

Background: Graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation (HCT). Severe acute GVHD of the gastrointestinal tract can be life threatening and is associated with a loss of acute phase proteins including alpha1-antitrypsin (AAT). AAT acts as a potent anti-inflammatory agent. We and others have shown in allogeneic murine models that administration of AAT during HCT suppresses serum levels of pro-inflammatory cytokines, interferes with GVHD and reduces transplant-related mortality. We embarked upon a phase I/II clinical study to evaluate the feasibility and safety of AAT given to HCT recipients with steroid non-responsive acute GVHD. We aimed at characterizing pharmacodynamic effects of AAT and assess clinical responses as determined by changes in stool volume and overall clinical improvement

Methods: Seven patients (3 female, 4 male) with hematologic malignancies were enrolled in the first and second cohort. Patients were 35-59 (median 50.4) years old and were given transplants from HLA-matched siblings (n=5) or received cord blood (n=2) following high intensity (myeloablative) or reduced intensity conditioning with cyclophosphamide +TBI (n=2), Fludarabine+TBI (n=4), or busulfan +cyclophosphamide (n=1). All patients received cyclosporine and MMF for GVHD prophylaxis. Acute GVHD of grades III-IV developed at 49 to 71 (median of 48) days, and treatment with systemic methylprednisolone, 2 mg/kg/day was instituted. Patients showing no clinically satisfactory responses after 5 days were given AAT (Glassia^TM) at 90 mg/kg iv on day 1, followed by 30 mg/kg (first cohort) or 60 mg/kg (second cohort) every other day for a total of 8 doses (15 days).

Results: As AAT levels vary considerably from person to person, we determined plasma AAT concentrations before and after administration of exogenous AAT. Pre-treatment AAT levels ranged from 1.25mg/ml to 2.3mg/ml (mean 1.76 mg/ml), while post-treatment AAT levels were 2.5 mg/ml to 5 mg/ml (mean 3.18 mg/ml), i.e. in the normal range. Concurrently, levels of Angptl4, IL10 and IL-15 protein increased in all patients, while TIM-3, a marker of lymphocyte activation, was down-regulated. RQ-PCR analysis of donor-derived cells showed up-regulation of IL-10 and IL-1Ra (50 log2 and 10 log2, respectively, compared to pre-treatment samples). FACS analysis of peripheral blood cells showed a 5-fold increase in CD4+CD24+FoxP3+ Treg cells and a 3 fold increase in CD8+CD205+ dendritic cells (DC) in comparison to pre-treatment samples in all 7 patients. Concurrently, the numbers of TIM-3 expressing CD4+ T lymphocytes decreased. While endoscopic evaluation of patients before treatment revealed severe intestinal GVHD with mucosal denudation, endoscopic evaluation one week after completion of AAT administration showed evidence of re-epithelialization of the bowel wall. Concurrently, five of the seven patients developed formed stools, associated with decreased intestinal loss of AAT. One patient required additional therapy and died with biopsy proven liver GVHD. With a median follow-up of 8 months (range 3.5-12 months), five of of seven patients are alive, no longer requiring treatment for GVHD.

Summary and conclusions: Continuous administration of AAT as salvage therapy for steroid resistant gut GVHD is feasible without clinically relevant toxicity. Stool sampling showed a decrease in intestinal AAT loss, as measured by AAT clearance and endoscopic evaluation confirmed healing of the bowel mucosa. These data are encouraging, and further exploration of AAT therapy in extended phase II and randomized trials as therapy of steroid refractory acute GVHD or as first line therapy are warranted.