Novel approaches to the therapy of steroid-resistant acute graft-versus-host disease
2004; Elsevier BV; Volume: 10; Issue: 10 Linguagem: Inglês
10.1016/j.bbmt.2004.07.007
ISSN1523-6536
AutoresJoseph H. Antin, Allen Chen, Daniel R. Couriel, Vincent T. Ho, Richard A. Nash, Daniel J. Weisdorf,
Tópico(s)T-cell and B-cell Immunology
ResumoIntroductionAcute graft-versus-host disease (GVHD) is a principal impediment to the cure of patients with blood disorders after allogeneic stem cell transplantation. Thus, much attention has been paid to understanding the pathophysiology of GVHD with the hope that elucidation of the mechanisms of GVHD will improve our ability to both prevent and treat this complex problem. The working framework for allogeneic GVHD is derived from Billingham and Brent's initial postulate that the development of GVHD requires that the graft contain immunologically competent cells and that the host contain membrane antigens lacking in the graft, which can be recognized as foreign [1Billingham R.E. The biology of graft-versus-host reactions.Harvey Lect. 1966; 62: 21-78PubMed Google Scholar]. We now generally accept that donor T cells are the immunologically competent cells and that these T cells recognize a set of host polypeptides as foreign. These antigens include both major and minor histocompatibility antigens and are thought to be metabolic products of normal protein metabolism that are processed through the endoplasmic reticulum and displayed by HLA molecules. These polypeptides are polymorphic and lead to T-cell recognition, activation, and, ultimately, tissue injury through a variety of cellular effector mechanisms. In essence, the donor's resting immune system suddenly comes in contact with new antigens in the setting of tissue injury that accompanies conditioning regimens, infection, and the underlying disease. Direct cell-mediated attack, production of inflammatory mediators (such as tumor necrosis factor alpha [TNF]-α and interferon gamma [IFN]-γ), and recruitment of secondary effectors completes the accelerating cycle of cell injury and inflammation that we recognize as GVHD [2Ferrara J. Antin J. The pathophysiology of graft-versus-host disease.in: Blume K. Forman S. Applebaum F. Thomas' Hematopoietic Cell Transplantation. Blackwell Publishing, Boston2004: 353-368Google Scholar] In this setting, the donor's immune system now finds itself in a milieu of upregulated chemokines, cytokines, and adhesion molecules, precisely as if there were a serious systemic infection [2Ferrara J. Antin J. The pathophysiology of graft-versus-host disease.in: Blume K. Forman S. Applebaum F. Thomas' Hematopoietic Cell Transplantation. Blackwell Publishing, Boston2004: 353-368Google Scholar, 3Antin J.H. Ferrara J.L. Cytokine dysregulation and acute graft-versus-host disease.Blood. 1992; 80: 2964-2968PubMed Google Scholar] Therefore it follows that if a therapeutic intervention can interrupt the GVHD, it may also interfere with the recipient's ability to respond to infection. Thus, control of established GVHD should be associated with an increased risk of opportunistic infections.Corticosteroids have been the primary therapy for acute GVHD for more than 3 decades [4Martin P.J. Schoch G. Fisher L. et al.A retrospective analysis of therapy for acute graft-versus-host disease initial treatment.Blood. 1990; 76: 1464-1472PubMed Google Scholar] Standard treatment of GVHD with high-dose corticosteroids effects a durable response in approximately 40% of patients after histocompatible sibling transplantation [5Weisdorf D. Haake R. Blazar B. et al.Treatment of moderate/severe acute graft-versus-host disease after allogeneic bone marrow transplantation an analysis of clinical risk features and outcome.Blood. 1990; 75: 1024-1030PubMed Google Scholar] and in only 24% after unrelated donor transplantation [6Roy J. McGlave P.B. Filipovich A.H. et al.Acute graft-versus-host disease following unrelated donor marrow transplantation failure of conventional therapy.Bone Marrow Transplant. 1992; 10: 77-82PubMed Google Scholar]. Thus, 60% to 75% of patients who develop clinically significant GVHD will require therapy beyond corticosteroids. For patients with steroid-refractory disease, no standard effective treatments are available [7Martin P.J. Schoch G. Fisher L. et al.A retrospective analysis of therapy for acute graft-versus-host disease secondary treatment.Blood. 1991; 77: 1821-1828PubMed Google Scholar]. A variety of agents have been studied in this setting, but outcome is generally disappointing. In this report, we review treatment of steroid-resistant GVHD, including studies of newly available agents.Antithymocyte globulinThe problems with the management of steroid-refractory acute GVHD are perhaps best illustrated in the experience with antithymocyte globulin (ATG). ATG has been a staple of GVHD therapy for many years and remains the most commonly used secondary treatment, especially among pediatric transplant centers [8Hsu B. May R. Carrum G. Krance R. Przepiorka D. Use of antithymocyte globulin for treatment of steroid-refractory acute graft-versus-host disease an international practice survey.Bone Marrow Transplant. 2001; 28: 945-950Crossref PubMed Scopus (36) Google Scholar]. A number of studies have demonstrated that ATG has activity in steroid-refractory GVHD, with 19% to 56% responses overall and skin responses from 59% to 79% [5Weisdorf D. Haake R. Blazar B. et al.Treatment of moderate/severe acute graft-versus-host disease after allogeneic bone marrow transplantation an analysis of clinical risk features and outcome.Blood. 1990; 75: 1024-1030PubMed Google Scholar, 6Roy J. McGlave P.B. Filipovich A.H. et al.Acute graft-versus-host disease following unrelated donor marrow transplantation failure of conventional therapy.Bone Marrow Transplant. 1992; 10: 77-82PubMed Google Scholar, 7Martin P.J. Schoch G. Fisher L. et al.A retrospective analysis of therapy for acute graft-versus-host disease secondary treatment.Blood. 1991; 77: 1821-1828PubMed Google Scholar, 8Hsu B. May R. Carrum G. Krance R. Przepiorka D. Use of antithymocyte globulin for treatment of steroid-refractory acute graft-versus-host disease an international practice survey.Bone Marrow Transplant. 2001; 28: 945-950Crossref PubMed Scopus (36) Google Scholar, 9Storb R. Gluckman E. Thomas E.D. et al.Treatment of established human graft-versus-host disease by antithymocyte globulin.Blood. 1974; 44: 56-75PubMed Google Scholar, 10Doney K.C. Weiden P.L. Storb R. Thomas E.D. Treatment of graft-versus-host disease in human allogeneic marrow graft recipients a randomized trial comparing antithymocyte globulin and corticosteroids.Am J Hematol. 1981; 11: 1-8Crossref PubMed Scopus (135) Google Scholar, 11Dugan M.J. DeFor T.E. Steinbuch M. Filipovich A.H. Weisdorf D.J. ATG plus corticosteroid therapy for acute graft-versus-host disease predictors of response and survival.Ann Hematol. 1997; 75: 41-46Crossref PubMed Scopus (38) Google Scholar, 12Remberger M. Aschan J. Barkholt L. Tollemar J. Ringden O. Treatment of severe acute graft-versus-host disease with anti-thymocyte globulin.Clin Transplant. 2001; 15: 147-153Crossref PubMed Scopus (73) Google Scholar, 13Khoury H. Kashyap A. Adkins D.R. et al.Treatment of steroid-resistant acute graft-versus-host disease with anti-thymocyte globulin.Bone Marrow Transplant. 2001; 27: 1059-1064Crossref PubMed Scopus (103) Google Scholar, 14Arai S. Margolis J. Zahurak M. Anders V. Vogelsang G.B. Poor outcome in steroid-refractory graft-versus-host disease with antithymocyte globulin treatment.Biol Blood Marrow Transplant. 2002; 8: 155-160Abstract Full Text Full Text PDF PubMed Scopus (133) Google Scholar, 15MacMillan M.L. Weisdorf D.J. Davies S.M. et al.Early antithymocyte globulin therapy improves survival in patients with steroid-resistant acute graft-versus-host disease.Biol Blood Marrow Transplant. 2002; 8: 40-46Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 16Ohashi K. Tanaka Y. Mori S. et al.Low-dose antithymocyte globulin for treatment of steroid-pulse-resistant acute graft-versus-host disease.Int J Hematol. 2003; 77: 99-102Crossref PubMed Scopus (5) Google Scholar]. However, overall survival has not improved, and 1-year mortality approaches 90%. Deaths typically are not from GVHD per se but are primarily from opportunistic infections that follow the prolonged and global immunosuppression. In concordance with this, Arai et al. [14Arai S. Margolis J. Zahurak M. Anders V. Vogelsang G.B. Poor outcome in steroid-refractory graft-versus-host disease with antithymocyte globulin treatment.Biol Blood Marrow Transplant. 2002; 8: 155-160Abstract Full Text Full Text PDF PubMed Scopus (133) Google Scholar] demonstrated that survival was similarly poor for patients regardless of their GVHD severity at the time of starting ATG, although a report from another group did show an improvement in survival when ATG was given as part of early therapy [15MacMillan M.L. Weisdorf D.J. Davies S.M. et al.Early antithymocyte globulin therapy improves survival in patients with steroid-resistant acute graft-versus-host disease.Biol Blood Marrow Transplant. 2002; 8: 40-46Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar]. The use of ATG is also complicated by the fact that at least 14 different formulations of horse- and rabbit-derived products are currently available worldwide. Furthermore, different brands, or even different lots of the same brand, of ATG may contain varying titers of antibodies against T-cell antigens, and this yields unpredictable bioactivity. The relative efficacy of horse- versus rabbit-derived ATG has never been compared in the stem cell transplantation setting. Finally, a standard dose and schedule for ATG in the treatment of GVHD has not been established, and an alarming observation was revealed by a recent international practice survey: only 6% to 28% of the 153 responding transplant centers were using ATG dosing guidelines published in the literature [8Hsu B. May R. Carrum G. Krance R. Przepiorka D. Use of antithymocyte globulin for treatment of steroid-refractory acute graft-versus-host disease an international practice survey.Bone Marrow Transplant. 2001; 28: 945-950Crossref PubMed Scopus (36) Google Scholar].Anti-interleukin-2 receptor monoclonal antibodiesBecause activated T cells play a major role in both the initiation and maintenance of GVHD, it was logical to target cells bearing the interleukin (IL)-2 receptor (IL-2R). This rationale is based on the principle that T-cell activation and expansion under the influence of IL-2 is crucial in the pathogenesis of acute GVHD. The human IL-2R is a heteromeric complex composed of up to 3 polypeptide chains, designated as α-, β-, and γ-subunits. On the basis of the combination of these subunits, the receptor exists in low, medium, and high IL-2 affinity binding forms. Most resting lymphocytes and natural killer (NK) cells express on their surface an intermediate-affinity IL-2R, which contains the β- and γ-chains, and expression of the α-subunit (CD25) is often restricted to T cells after antigen stimulation. The limited distribution of CD25 on activated lymphocyte subsets suggests that monoclonal antibodies against this subunit may be used to deplete alloreactive T cells in patients with GVHD. In the early 1990s, murine anti-IL-2R monoclonal antibodies were tested for steroid-refractory acute GVHD in human clinical trials. Complete response (CR) rates of 66% and 73% were reported in human trials of the murine monoclonal antibodies B-B10 and BT563, respectively [17Herve P. Wijdenes J. Bergerat J.P. et al.Treatment of corticosteroid resistant acute graft-versus-host disease by in vivo administration of anti-interleukin-2 receptor monoclonal antibody (B-B10).Blood. 1990; 75: 1017-1023PubMed Google Scholar, 18Herbelin C. Stephan J.L. Donadieu J. et al.Treatment of steroid-resistant acute graft-versus-host disease with an anti-IL-2-receptor monoclonal antibody (BT 563) in children who received T cell-depleted, partially matched, related bone marrow transplants.Bone Marrow Transplant. 1994; 13: 563-569PubMed Google Scholar].The notion that these reagents may delete only activated T cells while sparing resting T cells suggested that immunologic recovery might be enhanced compared with a pan-T-cell antibody such as ATG. Several monoclonal antibodies with varying human and mouse elements are available (Figure 1). Most studies in hematopoietic stem cell transplantation were performed with daclizumab (Zenapax; Roche Pharmaceuticals, Nutley, NJ), a 144-kd humanized immunoglobulin G1 monoclonal antibody that binds specifically to the α-subunit (p55 α, CD25, or Tac subunit) of the human IL-2R, where it inhibits IL-2 binding. Daclizumab has been used extensively in solid organ transplantation, where it seems to decrease the number and severity of rejection episodes without increasing adverse events, infectious complications, or late malignancies [19Beniaminovitz A. Itescu S. Lietz K. et al.Prevention of rejection in cardiac transplantation by blockade of the interleukin-2 receptor with a monoclonal antibody.N Engl J Med. 2000; 342: 613-619Crossref PubMed Scopus (213) Google Scholar, 20Bumgardner G. Hardie I. Johnson R. et al.Results of 3-year phase III clinical trials with daclizumab prophylaxis for prevention of acute rejection after renal transplantation.Transplantation. 2001; 72: 839-845Crossref PubMed Scopus (105) Google Scholar]. Daclizumab demonstrated a 40% response rate in a phase I trial of steroid-refractory acute GVHD [21Anasetti C. Hansen J.A. Waldmann T.A. et al.Treatment of acute graft-versus-host disease with humanized anti-Tac an antibody that binds to the interleukin-2 receptor.Blood. 1994; 84: 1320-1327Crossref PubMed Google Scholar]. A subsequent larger trial reported a CR rate of 47% when daclizumab was administered twice weekly, whereas overall survival was 53% at 4 months [22Przepiorka D. Kernan N.A. Ippoliti C. et al.Daclizumab, a humanized anti-interleukin-2 receptor alpha chain antibody, for treatment of acute graft-versus-host disease.Blood. 2000; 95: 83-89PubMed Google Scholar]. Encouraging activity has also been reported in steroid-refractory GVHD for other commercially available IL-2Ra antibodies, including inolimomab (BT563) and basiliximab [18Herbelin C. Stephan J.L. Donadieu J. et al.Treatment of steroid-resistant acute graft-versus-host disease with an anti-IL-2-receptor monoclonal antibody (BT 563) in children who received T cell-depleted, partially matched, related bone marrow transplants.Bone Marrow Transplant. 1994; 13: 563-569PubMed Google Scholar, 23Hertenstein B. Stefanic M. Sandherr M. Bunjes D. Mertens T. Arnold R. Treatment of steroid-resistant acute graft-vs-host disease after allogeneic marrow transplantation with anti-interleukin-2 receptor antibody (BT563).Transplant Proc. 1994; 26: 3114-3116PubMed Google Scholar, 24Massenkeil G. Rackwitz S. Genvresse I. Rosen O. Dorken B. Arnold R. Basiliximab is well tolerated and effective in the treatment of steroid-refractory acute graft-versus-host disease after allogeneic stem cell transplantation.Bone Marrow Transplant. 2002; 30: 899-903Crossref PubMed Scopus (92) Google Scholar]. Laboratory correlate studies revealed significant reductions in CD3+CD25+ lymphocytes after daclizumab treatment, although these reductions did not correlate with clinical response. On the basis of these encouraging results, a multicenter randomized, double-blinded, placebo-controlled trial testing the addition of daclizumab to corticosteroids as initial therapy for acute GVHD has recently been completed. Unfortunately, there was significantly inferior 100-day survival (77% versus 94%; P = .02) and overall survival (29% versus 60%; P = .002) when daclizumab was combined with corticosteroids, despite an equivalent rate of GVHD control (53% versus 51%; P = .85) [25Lee S.J. Zahrieh D. Agura E. et al.Effect of up-front daclizumab when combined with steroids for the treatment of acute graft-vs.-host disease results of a randomized trial.Blood. 2004; 104: 1559-1564Crossref PubMed Scopus (172) Google Scholar].Denileukin diftitoxDenileukin diftitox (Ontak; Ligand Pharmaceuticals, San Diego, CA) is a recombinant fusion protein with selective cytotoxicity against activated T lymphocytes based on its preferential binding to high-affinity IL-2R. Denileukin diftitox consists of an N-terminal methionine, the first 386 amino acids of diphtheria toxin, fused to amino acid residues 1 to 133 of IL-2. After internalization by IL-2R-mediated endocytosis, the diphtheria toxin portion of the molecule is cleaved, and the catalytic A fragment is transferred to the cytosol, where it catalyzes adenosine diphosphate ribosylation of elongation factor 2 on ribosomes, halts cellular protein synthesis, and triggers programmed cell death [26Falnes P.O. Sandvig K. Penetration of protein toxins into cells.Curr Opin Cell Biol. 2000; 12: 407-413Crossref PubMed Scopus (243) Google Scholar].Pharmcokinetics of denileukin diftitoxAside from its selectivity for activated T cells, denileukin diftitox has pharmacokinetic properties that may render it favorable for use in patients with GVHD. Denileukin diftitox is metabolized by ubiquitous proteolytic degradation, and dose adjustments are not necessary for hepatic or renal dysfunction. After administration, denileukin diftitox follows dose-proportional kinetics and exhibits monophasic clearance from the serum, with a terminal half-life of 72 minutes. A phase I study in lymphoma patients has also established that the serum concentration of denileukin diftitox does not accumulate despite repeated daily administrations [27LeMaistre C.F. Saleh M.N. Kuzel T.M. et al.Phase I trial of a ligand fusion-protein (DAB389IL-2) in lymphomas expressing the receptor for interleukin-2.Blood. 1998; 91: 399-405PubMed Google Scholar]. This pharmacokinetic profile may have important implications in terms of minimizing prolonged immune suppression.Denileukin diftitox may also be advantageous compared with monoclonal antibodies directed against CD25 on the basis of its mechanism of action. Unlike monoclonal antibodies, which function by blocking IL-2 binding to the IL-2R and depend on secondary effector mechanisms such as complement activation or antibody-dependent cellular cytotoxicity for cell kill, denileukin diftitox exerts its cytotoxic effects directly via its toxin moiety. The kinetics of this cytotoxicity are extremely efficient. In vitro studies suggest that only 10 to 40 binding sites are necessary on the cell surface for entry, and that entry of only 1 molecule of denileukin diftitox is sufficient to induce cell death [28Foss F.M. DAB(389)IL-2 (ONTAK) a novel fusion toxin therapy for lymphoma.Clin Lymphoma. 2000; 1: 110-116Abstract Full Text PDF PubMed Scopus (101) Google Scholar].Finally, it has been suggested that that bioactivity of anti-CD25 monoclonal antibodies could be dampened by binding to soluble IL-2R (sIL-2R), a phenomenon known as cold-target inhibition [29Junghans R.P. Carrasquillo J.A. Waldmann T.A. Impact of antigenemia on the bioactivity of infused anti-Tac antibody implications for dose selection in antibody immunotherapies.Proc Natl Acad Sci U S A. 1998; 95: 1752-1757Crossref PubMed Scopus (23) Google Scholar]. However, concentrations of purified sIL-2R as high as 2500 pmol/L had no effect on the in vitro biologic activity of denileukin diftitox. Similarly, LeMaistre et al. [30LeMaistre C.F. Meneghetti C. Rosenblum M. et al.Phase I trial of an interleukin-2 (IL-2) fusion toxin (DAB486IL-2) in hematologic malignancies expressing the IL-2 receptor.Blood. 1992; 79: 2547-2554Crossref PubMed Google Scholar] reported that the presence of sIL-2R did not prevent antitumor responses mediated by DAB486IL-2, a precursor molecule to denileukin diftitox. These results suggest that sIL-2R competes poorly with denileukin diftitox for the native IL-2R [27LeMaistre C.F. Saleh M.N. Kuzel T.M. et al.Phase I trial of a ligand fusion-protein (DAB389IL-2) in lymphomas expressing the receptor for interleukin-2.Blood. 1998; 91: 399-405PubMed Google Scholar, 30LeMaistre C.F. Meneghetti C. Rosenblum M. et al.Phase I trial of an interleukin-2 (IL-2) fusion toxin (DAB486IL-2) in hematologic malignancies expressing the IL-2 receptor.Blood. 1992; 79: 2547-2554Crossref PubMed Google Scholar].Denileukin diftitox in acute GVHDHo et al. [31Ho V. Zahrieh D. Hochberg E. et al.Safety and efficacy of denileukin diftitox in patients with steroid refractory acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation.Blood. 2004; 104: 1224-1226Crossref PubMed Scopus (133) Google Scholar] conducted a phase I study investigating denileukin diftitox in 32 patients with steroid-refractory acute GVHD. Three dose schedules were evaluated: level 1, 9 μg/kg intravenously on days 1 and 15; level 2, 9 μg/kg on days 1, 3, 5, 15, 17, and 19; and level 3, 9 μg/kg on days 1 to 5 and 15 to 19. Dose escalation was determined by dose-limiting toxicity (DLT) at each dose level. After the maximum tolerated dose (MTD) was determined, 10 additional patients were enrolled to assess efficacy. The initial dose of denileukin diftitox was administered over 60 minutes, with subsequent doses over 30 minutes. Patients were premedicated with diphenhydramine, acetaminophen, and corticosteroid. Whenever possible, the daily steroid dose was used as premedication.At dose level 3, all 4 evaluable patients developed DLT (1 renal failure and 3 hepatic transaminase elevation). Therefore, dose level 2 was considered the MTD. Hepatic dysfunction, defined as alanine aminotransferase or aspartate aminotransferase ≥5 times baseline or the upper limit of normal or total bilirubin ≥3 times baseline, was the most common DLT (30%), occurring in 4 (22%) of 18 patients at the MTD. Although increased hepatic transaminase was common in the week after denileukin diftitox administration, isolated hyperbilirubinemia was rare and was observed in only 1 patient in this trial. Other severe adverse events potentially attributable to therapy included infusional reaction, acute renal failure, cardiac tamponade, and sepsis, but these toxicities occurred in very few patients and were difficult to ascribe to therapy per se. Severe vascular leak syndrome was not observed, and no patient developed respiratory distress from pulmonary edema. Most patients had some degree of peripheral edema and hypoalbuminemia before and after therapy with denileukin diftitox. Eight of the 32 patients died during the study period. Causes of death were GVHD, sepsis/multiorgan failure, idiopathic pneumonia syndrome, intracranial hemorrhage, and liver failure.GVHD responses to denileukin diftitox are shown in Table 1. Of the 24 patients evaluable for GVHD response, 8 (33%) resolved all evidence of GVHD (CR) on or before study day 29, and 9 (38%) improved by at least 1 grade (partial response; PR), for an overall response rate of 71%. Of the PRs, 4 subsequently entered a CR without additional immune-suppressive therapy, resulting in an overall CR rate of 50% (12/24). GVHD response correlated with increasing dose frequency. The best responses were observed at dose level 2, at which 6 (46%) of 13 achieved a CR and 3 (23%) had a PR that subsequently converted to a CR after 1 month (resulting in an overall CR rate at level 2 of 69%). GVHD responses to denileukin diftitox were substantial in patients with skin and intestine involvement, with individual organ CRs of 44% and 56%, respectively, and overall response rates of 69% to 71%. Ten patients had previously been unsuccessfully treated with daclizumab, and it is interesting to note that 8 of these patients either completely or partially resolved the GVHD after denileukin diftitox (1 CR and 7 PRs). With extended follow-up, 9 of 30 patients treated are alive (median, 7.2 months). Among the 12 patients who ultimately had complete resolution of GVHD, 7 (58%) are alive. Conversely, only 1 of 12 evaluable patients who did not achieve a CR is alive (P < .001). There have been 5 late deaths among patients in CR: 3 from infection (2 bacterial and 1 fungal), 1 from chronic GVHD, and 1 from relapse. No Epstein-Barr virus-associated lymphoma or cytomegalovirus disease has been observed.Table 1GVHD Response to Denileukin DiftitoxVariableComplete ResponsePartial ResponseOverall ResponseDose Level 11/7 (14%)4/7 (57%)5/7 (71%) Level 26/13 (46%)3/13 (23%)9/13 (69%) Level 3*Only 1 patient at this level completed the intended 10 doses, because of toxicity; 4 of 9 PRs converted to CR after day 29 without additional therapy.1/4 (25%)2/4 (50%)3/4 (75%) Overall8/24 (33%)9/24 (38%)17/24 (71%)Organs involved Skin7/16 (44%)4/16 (25%)11/16 (69%) Intestine9/16 (56%)3/16 (19%)12/16 (75%) Liver1 (25%)01 (25%)GVHD grade at enrollment II1/8 (13%)4/8 (50%)5/8 (63%) III5/13 (38%)4/13 (31%)9/13 (69%) IV2/3 (67%)1/3 (33%)3/3 (100%)* Only 1 patient at this level completed the intended 10 doses, because of toxicity; 4 of 9 PRs converted to CR after day 29 without additional therapy. Open table in a new tab Flow cytometry of peripheral blood samples taken during the study period revealed low pretreatment numbers of absolute CD3+CD25+ lymphocytes, and this did not change after treatment with denileukin diftitox. However, there was a marginally significant reduction in absolute NK cell and in CD3+ lymphocyte counts 1 to 7 days after treatment, followed by brisk recovery after the third week. The reduction in absolute CD3+ count by 1 to 7 days was statistically significant in patients who eventually achieved a CR (P = .03) but was unchanged in nonresponders. Serum or plasma sIL-2R levels were comparable to control post-hematopoietic stem cell transplantation patients without GVHD, and sIL-2R levels remained stable after denileukin diftitox. There was no correlation between sIL-2R level and clinical response.SummaryDenileukin diftitox can be safely administered in patients after allogeneic hematopoietic stem cell transplantation. A reversible increase in hepatic transaminases is the major DLT, but the incidence (22% at the MTD) is comparable to the 17% reported in patients with cutaneous T-cell lymphoma [32Olsen E. Duvic M. Frankel A. et al.Pivotal phase III trial of two dose levels of denileukin diftitox for the treatment of cutaneous T-cell lymphoma.J Clin Oncol. 2001; 19: 376-388Crossref PubMed Scopus (565) Google Scholar]. Denileukin diftitox seems to have significant clinical activity in steroid-refractory acute GVHD, with complete and overall response rates of 46% and 69%, respectively, at the MTD.Although the numbers of peripheral CD3+CD25+ cells were not affected by treatment, absolute numbers of peripheral CD3+ lymphocytes were transiently depleted after treatment with denileukin diftitox, especially in patients who achieved a CR. These results suggest that denileukin diftitox preferentially targets CD3+ T cells that are involved in the GVHD response and that resistance to therapy is associated with the inability of this agent to eliminate these cells in some patients. Because treatment resulted in the elimination of CD3+ T cells that did not express high levels of CD25, these observations suggest that cells expressing other components of the IL-2R may also internalize sufficient denileukin diftitox to result in cell death in vivo. Alternatively, flow cytometry may not be able to detect relatively low-level expression of high-affinity receptors that may still be sufficient to bind and internalize denileukin diftitox.Despite the encouraging GVHD responses and improved survival among the patients who achieved a CR, the overall survival for this entire cohort was disappointing, and infections remained a common cause of late mortality. Attribution of late infections to denileukin diftitox is difficult in this study because these patients had received many prior immunosuppressive therapies. Future clinical trials investigating denileukin diftitox as primary therapy or in a more viable population of patients with steroid-refractory disease are needed to confirm the responses reported here and to determine whether this agent improves survival for patients with acute GVHD.Mycophenolate mofetilMycophenolate mofetil ([MMF] CellCept; Roche Laboratories, Indianapolis, IN) is a morpholinoethyl ester of mycophenolic acid (MPA). MPA possesses antibacterial, antifungal, antiviral, antitumor, and immunosuppressive properties. However, to facilitate absorption, it must be administered as the prodrug, MMF. Approximately 95% of the oral dose of MMF is absorbed, and the immunosuppressive activity is evident after de-esterification to MPA in vivo [33Morris R.E. Wang J. Comparison of the immunosuppressive effects of mycophenolic acid and the morpholinoethyl ester of mycophenolic acid (RS-61443) in recipients of heart allografts.Transplant Proc. 1991; 23: 493-496PubMed Google Scholar]. MPA mediates its immunosuppressive effect by inhibiting inosine monophosphate dehydrogenase, an enzyme that catalyzes the oxidation of inosine monophosphate to xanthine monophosphate, an intermediate metabolite in the synthesis of guanosine triphosphate. Lymphocytes rely on the de novo purine synthesis pathway for the nucleotides necessary for DNA synthesis, whereas other cells can also use the salvage pathway [34O'Reilly R.J. Keever C.A. Small T.N. Brochstein J. The use of HLA-non-identical T-cell-depleted marrow transplants for correction of severe combined immunodeficiency disease.Immunodefic Rev. 1989; 1: 273-309PubMed Google Scholar, 35Eugui E.M. Mirkovich A. Allison A.C. Lymphocyte-selective antiproliferative and immunosuppressive effects of mycophenolic acid in mice.Scand J Immunol. 1991; 33: 175-183Crossref PubMed Scopus (188) Google Scholar, 36Eugui E.M. Mirkovich A. Allison A.C. Lymphocyte-selective antiproliferative and immunosuppressive activity of mycophenolic acid and its morpholinoethyl ester (RS- 61443) in rodents.Transplant Proc. 1991; 23: 15-18PubMed Google Scholar]. Therefore, MPA depletes the nucleotide pool, resulting in relatively selective suppression of
Referência(s)