A Novel GVHD-Prophylaxis with Low-Dose Alemtuzumab in Allogeneic Sibling or Unrelated Donor Hematopoetic Cell Transplantation: The Feasibility of Deescalation

Article Outline

• Abstract
• Introduction
• Patients and Methods
  • Patient Characteristics
  • Conditioning Regimen, GVHD Prophylaxis, and Stem Cell Source
  • Protocol History
  • Supportive Care
  • Study Endpoints, Definitions, and Statistical Analysis
• Results
  • Engraftment
  • Acute GVHD
  • Chronic GVHD
  • Infections
  • Response and Relapse
  • NRM
  • Outcome (Table 3)
• Discussion
• Acknowledgments
• References
• Copyright

Prophylaxis of acute graft-versus-host disease (aGVHD), while maintaining the graft-versus-leukemia (GVL)/lymphoma effect and preventing severe infectious diseases, remains the main challenge in allogeneic hematopoetic cell transplantation (allo-HCT). To evaluate this, we examined the feasibility of deescalating the dose of alemtuzumab (MabCampath™) in combination with cyclosporine (CsA) as the sole GVHD-prophylaxis in patients after fludarabine (Flu)-based reduced-intensity conditioning (RIC) in an observational cohort study. We included 127 consecutive patients (median age 63 years) with an unrelated (UD; n=69) or related donor (SIB; n=58) after their first transplantation, mostly presenting with advanced disease. The first 30 patients received 20 mg/day on day −2 and −1 (40 mg), the following 48 patients 10 mg/day on day −2 and −1 (20 mg), and the last 49 patients 10 mg on day −1 (10 mg) alemtuzumab intravenous (i.v.) prior to transplant. We observed no statistical differences comparing the 40 mg, 20 mg, or 10 mg dose groups, in terms of cumulative incidences of aGVHD grade III-IV 7% (confidence interval [CI] 95%; 1-51), 12% (1-40), 6% (1-40), extensive chronic GVHD (cGVHD) 24.4% (3.3-55.8), 17% (2.5-42), and 14.2% (1.5-41.5) and of aGVHD grade II-IV 7 % (0-51.5), 29% (11.9-49.1), 21% (15.3-43.1), respectively. The difference between the 20-mg and 40-mg groups was significant for aGVHD grade II-IV(P < .05). In conclusion, we demonstrate the feasibility of reducing the dose of alemtuzumab as GVHD-prophylaxis to 10 mg absolute in combination with CsA only for UD transplantation in particular.

Key Words: Allogeneic HCT, Alemtuzumab, Graft-versus-host disease

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Introduction 

To reduce the incidence and severity of acute graft-versus-host disease (aGVHD), especially in volunteer unrelated donor transplantation (UD), polyclonal antibodies like antithymocyte globulin (ATG) have been used in combination with standard cyclosporine/methotrexate (CsA/MTX) prophylaxis [1]. A group of monoclonal antibodies (mAbs) against CD52 (Campath-1) were introduced [2] to deplete recipient and donor T cells, provide engraftment, and prevent severe aGVHD. The anti-CD52 antibody was initially used for in vitro T cell depletion by exposing stem cell products to the rat Campath-1 G, a procedure called “Campath in the bag” [3]. Campath-1H (alemtuzumab) is a humanized IgG 1 mAb that recognizes the CD52 antigen on human lymphocytes, natural killer (NK) cells, monocytes/macrophages, dendritic cells, and eosinophils, but not on hematopoetic stem cells (HSCs) 4, 5. Campath-1H has been studied in vitro [6] and used in vivo as part of conditioning regimens since 1997 [7].

Initially, the total dose of alemtuzumab was 100 mg total dose given i.v. over 5 days prior to transplantation 2, 7. Although panlymphocyte depletion resulted in significantly less GVHD, there was increased incidence of severe viral and opportunistic infections, graft failure, and relapse. To prevent these complications, 2 groups reduced the alemtuzumab dose as part of the conditioning regimen to 50 mg total dose in sibling and UD transplantation 8, 9 in addition to using calcineurin inhibitors and MTX as GVHD prophylaxis.

In an effort to reduce infectious complications and maintain a significant graft- versus-malignancy effect, we aimed at further reducing the total dose of alemtuzumab dose and substituting MTX and mycophenolat-mofetil (MMF), because of their side effects as part of the GVHD prophylaxis in our reduced-intensity conditioning (RIC) protocols 10, 11, 12. The observational design was to initially use alemtuzumab 40 mg total dose and deescalate to 20 mg total if aGVHD and mortality rates did not increase in 70 patients compared to our standard GVHD prophylaxis used before, consisting of CsA/MMF or CsA/MTX. Further alemtuzumab tapering (10 mg total) was dependent on the noninferiority of 20 mg to 40 mg after interim analysis of significant numbers of patients treated. Therefore, in 2002, we incorporated lower doses of alemtuzumab (total 40 mg) as part of our GVHD prophylaxis in combination with CsA into our internal review board (IRB) and ethics committee-approved RIC protocol designed for relapsed patients undergoing second allogeneic transplantation [10], and since 2003, included it in our primary RIC-protocol study protocol 11, 12. As we did not observe higher incidences of aGVHD and morbidity, we further amended the protocol to deescalate the alemtuzumab dose to 20 mg total, and later, a 10-mg total dose.

Here we report data from our observational study with 3 consecutive patient cohorts after their first transplantation receiving the i.v. administration of 3 doses of alemtuzumab (40 mg, 20 mg, and 10 mg) in combination with CsA as GVHD prophylaxis.

Our experience in 127 consecutive patients with hematologic malignancies who underwent UD (n=69) or sibling donor (n=58) transplantation show similar results for aGVHD and extensive chronic GVHD (cGVHD).

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Patients and Methods 

Patient Characteristics 

Patient characteristics are listed in Table 1. The 127 patients received their first transplantation for de novo acute myelogenous leukemia (AML, n=35), therapy-related or secondary AML or myelodysplastic syndrome (MDS0, refractory anemia (RA), refractory anemia with excess blasts (RAEB) 2, refractory anemia with excess blasts in transformation (RAEB-T), chronic myelomonocytic leukemia (CMMoL) (n=50), acute lymphoblastic leukemia (ALL; n=7), non-Hodgkin lymphoma (NHL)/Hodgkin lymphoma (HL)/multiple myeloma (MM)/chronic lymphocytic leukemia (CLL) (n=27), and chronic myelogenous leukemia (CML)/other myeloproliferative syndromes (MPS) (n=8). The 53 female and 74 male patients had a median age of 63 years (24-76 years). At transplantation, 30 patients were untreated, 18 patients were in first complete remission or first chronic phase (CR1/CP1), and all other patients (n=79) had advanced disease (CR>1, >CP1, persistent induction failure, relapse ≥1, progressive disease, partial remission, stable disease). One hundred three of the 127 patients (81%) were at risk at transplantation for cytomegalovirus (CMV) infection/disease because of positive pretransplant CMV serology in the patient and/or donor.

Table 1. Patients, Transplantation, and Donor Characteristics

y indicates years; AML, acute myelogenous leukemia; MDS, myelodysplastic syndrome; tAML, therapy-associated AML; sAML, secondary AML; tsAML, therapy-associated secondary AML; MDS, myelodysplastic syndrome; MPS, myeloproliferative syndrome; NHL non-Hodgkin lymphoma; CLL, chronic lymphocytic lymphoma; MM, multiple myeloma; HCT, hematopoetic cell transplantation; CR, complete remission; CP, chronic phase; REL, relapse; PIF, persistant induction failure; other, chronic phase, accelerated phase, blast crisis, progression, partial remission, stable disease; TX, transplantation; allo, allogen; auto, autologous; UD, unrelated donor; CMV, cytomegalovirus; D, donor; P, patient; G-CSF, granulocyte colony-stimulating factor; Flu, fludarabine; B, carmustin; Mel, melphalan; TT, thiotepa.

Conditioning Regimen, GVHD Prophylaxis, and Stem Cell Source 

All patients received fludarabine (Flu)-based RIC regimens. Inclusion criteria have been published elsewhere 10, 11, 12. One hundred eighteen patients received Flu (Schering, Berlin, Germany) 30 mg/m²/day given from day −9 to day −5 (since July 2005: Flu 30 mg/m²×4 days from day −8 to day −5), carmustine (Bristol Myers Squibb, Munich, Germany) 200 mg/m²/day (<55 years of age) or 150 mg/m²/day (≥55 years) given from day −7 to day −6, and melphalan (Mel; GlaxoSmithKline, Hamburg, Germany) 140 mg/m²/day (<55 years of age) or 110 mg/m²/day (≥55 years) given at day −4, as previously described (Flu/B/Mel regimen; n=118) 11, 12. One patient received Flu 30 mg/m²/day given from day −7 to day −4 and thiotepa 5 mg/kg/day for 3 days given from day −6 to day −4 (Flu TT; n=1) [10]. Seven patients with ALL, and 1 patient with AML received Flu 3×30 mg/m², BCNU 300 mg/m² and thiotepa 4×5 mg/kg (Flu/Blu/TT; n=8).

The GVHD prophylaxis consisted of i.v. cyclosporine A (CsA) starting at day –3 at a dose of 2.5 mg/kg twice a day (trough level 250-350 ng/mL) 10, 11, 12 in combination with alemtuzumab (MabCampath™, Schering, Berlin, Germany) given i.v. over 4 hours. In 2003, the alemtuzumab was given in a total dose of 40 mg by infusing 20 mg/day on days −2 and −1 (n=30, group 40 mg). Since July 2005, alemtuzumab has been deescalated to a total dose of 20 mg given as 10 mg/day on days −2 and −1 (n=48, group 20 mg), and, since June 2006, we have been giving a single dose of 10 mg on day −1 (n=49, group 10 mg) (Table 1). Comedication included 100 mg prednisolone, 10 mg clemastine (H1-blocker), and 50 mg ranitidin before and directly after the alemtuzumab infusion. In the case of adverse reactions we extended the usual infusion time (2 hours) and administered additional corticosteroids. After transplantation, in patients without GVHD, orally administered CsA was usually tapered from day +60, and usually discontinued at day +120.

The main graft source were (124/127 [98%]) unmanipulated rhu-granulocyte-colony stimulated factor (G-CSF)-mobilized peripheral blood stem cells (PBSCs), whereas bone marrow (BM) was transplanted in 3 UD transplantations because of availability. Donors were siblings (n=58; 46%) and unrelated volunteers (n=69; 54%). HLA class I antigens were typed by serology or intermediate resolution DNA techniques (2 digits) and HLA class II by high-resolution DNA techniques (4 digits) [11]. The unrelated donors were mismatched in HLA-A, -B, -C, -DRB1, or DQB1 in 26/69 (38%) of the transplantations with more than 1 mismatch in 3 patients (Table 1).

Protocol History 

All patients gave informed consent to being included in a local IRB and ethics committee-approved RIC protocol. The protocol was carried out according to the Helsinki declaration. The GVHD prophylaxis protocol containing alemtuzumab (2×20 mg) was established initially within second transplantations [10]. Because of the low incidence of aGVHD in these patients, in 2003 first transplants from both sibling and UD were included by amendment. After an interim analysis for aGVHD rate and mortality of 71 patients receiving alemtuzumab 40 mg total dose in combination with CsA (data not shown), the alemtuzumab dose was deescalated to 20 mg total by amendment in 2005, and finally to 10 mg total in 2006 following interim analysis of the 61 patients previously treated with 2×10 mg (data not shown), because of low morbidity and a similarly low rate of aGVHD.

Supportive Care 

Standard supportive care was given as previously described [13]. Briefly, all patients received fluconazole and ciprofloxacin prophylaxis until day +25 and acyclovir prophylaxis until day +100. In the case of fever, broad-spectrum antibiotic treatment was started and escalated according to our in-house standards [11]. The first 8 patients included in the 40-mg group received filgrastim (Amgen, Munich, Germany) at 5 μg/kg starting on day +7 and until leukocytes >1×10⁹/L. After stable engraftment, cotrimoxazole (TMS) was added twice per week (or an alternative regimen consisting of dapsone/daraprime) for pneumocystis jiroveci pneumonia (PjP) prophylaxis. CMV in peripheral blood was monitored in all patients using fluorescein antigen-detection methodology and by quantitative CMV-polymerase chain reaction (PCR) twice weekly after engraftment and up to discharge, once weekly up to day +100, and at least once every 3 weeks until immunnosuppression was completely withdrawn and no GVHD was present. In cases of positive CMV antigenemia or 1 positive CMV-PCR with copy numbers above 3000/μL or 2 consecutive positive CMV-PCR assays >1000/μL, we initiated preemptive standard ganciclovir, valganciclovir, or foscarnet therapy for at least 1 week until the apparent CMV negativity [1]. CMV infection was defined as asymptomatic CMV antigenemia or PCR positivity in peripheral blood requiring preemptive therapy; a positive culture in any histologic tissue was considered as CMV disease 14, 15. Since 2003, we have monitored Epstein-Barr virus (EBV) infection/reactivation in peripheral blood and by quantitative PCR, defining EBV reactivation whenever copies were above 5000/μL. EBV-associated disease/infection was defined as positive EBV-PCR in any nonblood specimen or as posttransplantation lymphoproliferative disease (PTLD) with additional new lymphomas on any side. Studies for other viral (adenovirus, respiratorial syncytial virus, varizella zoster virus) and PjP infections were performed when indicated.

Study Endpoints, Definitions, and Statistical Analysis 

Data were evaluated as of December 31, 2008. Follow-up of all patients was complete. aGVHD and cGVHD was assessed using the criteria of Przepiorka and Shulman 16, 17. The day of engraftment was defined as the first of 3 consecutive days with leukocytes ≥1×10⁹/L. Platelet recovery was defined as a platelet count ≥20×10⁹/L without transfusion.

The time to event was analyzed using the Kaplan-Meier method and the different groups were compared by the Log-Rank test and the 2-tailed t-test. This included the estimated cumulative incidences of aGVHD and cGVHD, leukocyte and platelet recovery, incidence of CMV infection, of morphologic relapse, overall survival (OS), and nonrelapse mortality (NRM). Kaplan-Meier estimates were based on the time from hematopoietic cell transplant (HCT) until the censored event or death. All statistical analyses were calculated using the commercially available GraphPad PRISM Version 5.00.

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Results 

Engraftment 

Engraftment occurred in 123/127 evaluable patients leukocyte engraftment ≥1×10⁹/L occurred at a median of 12 days (range: 9-24, n=29) in the 40-mg group, by day +14 (range: 9-25, n=46) in the 20-mg group, and by day +13 (range: 8-18, n=48) in the 10-mg group, with no statistical difference among the 3 groups (Table 2). The absolute neutrophil count (ANC) ≥1×10⁹/L revealed similar results: day +16 (range: 11-42, n=29; group 40), day +18.5 (range: 10-36, n=45; group 20 mg), and day +17 (range: 11-54, n=48; group 10 mg).

Table 2. Engraftment

WBC indicates total white blood cell; ANC, absolute neutrophil count.

Three patients died before stable engraftment in the 20-mg (n=2) and 40-mg groups (n=1). Overall, we observed only 1 primary graft failure in a female patient from the 10-mg group with untreated MPS/chronic neutrophilic leukemia in the accelerated phase; stable engraftment was achieved by a second transplantation from the same donor.

Stable platelet counts ≥20×10⁹/L were reached at median day +10 (range: 7-23, n=28, group 40 mg) and day +11 in both other groups (range: 0-48, n=43, group 20 mg; range: 6-34, n=48, group 10 mg). Platelet counts ≥50×10⁹/L were reached by day +12 (range: 8-37; n=27, group 40 mg), day +14 (range: 9-97, n=42, group 20 mg; and day +13 (range: 10-64, n=46; group 10 mg), respectively.

Three of 30 patients in group 40 mg, 6/48 in group 20 mg, and 3/49 in group 10 mg died prior to stable platelet engraftment (Table 2).

Acute GVHD 

Of the 127 patients, 124 were evaluable for aGVHD evaluation after engraftment. Clinically relevant aGVHD grade II-IV developed with a cumulative incidence of 7% (2/30) and grade III-IV of 7% (2/30) in the 40-mg group. Acute GVHD grade II-IV in group 20 mg occurred with a cumulative incidence of 29% (13/48) and grade III-IV of 12% (5/48), and in the 10-mg group with a cumulative incidence of 21% grade II-IV (10/49) and grade III-IV of 6% (3/49), respectively. There were no differences in the occurrence of grade II-IV and III-IV aGVHD among the 3 dose groups, except when comparing the 20-mg and the 40-mg group for aGVHD grade II-IV(P < .05) (Figure 1).

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• Figure 1 

  Kaplan-Meier estimated incidences of aGVHD grade II-IV and grade III-IV.

The incidence of aGVHD within the 3 groups according to the graft source (SIB versus UD) revealed no significant difference for aGVHD grade II-IV and grade III-IV in the unpaired t-test.

The results in detail: after 40 mg total dose of alemtuzumab, aGVHD grade II-IV developed in 27% in UD transplantation compared to 0% (P < .005) after sibling transplantation, and for aGVHD grade III-IV 23.8% after UD and 0% (p=not significant [n.s.]) in SIB transplantation (Figure 2). Within the 20-mg group, there was a cumulative 34% incidence of aGVHD grade II-IV after UD and 16% (P=n.s.) after sibling transplantation. The comparison for aGVHD grade III-IV (12.5% in UD and 7% in SIB transplantations) is n.s.

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• Figure 2 

  (a,b) Kaplan-Meier estimated incidences of aGVHD grade II-IV and grade III-IV in comparison with graft source (SIB/UD).

Within the 10-mg group, UD resulted in a nonsignificant higher incidence of grade II-IV aGVHD compared to SIB transplantation (UD 28% versus SIB 10%; P=ns) but a similar occurence of severe grade III-IV aGVHD (UD 7% versus SIB 5%; P=n.s.). The cumulative incidence of severe aGVHD was not higher after UD transplantation (Figure 2).

Chronic GVHD 

Of the 127 patients observed, 111 were evaluable for cGVHD evaluation. No cGVHD developed in 14 patients of the 40-mg, 28 patients of the 20-mg group, and 30 patients of the 10-mg group, respectively. The cumulative incidence of cGVHD was 44% (40-mg group), 38% (20-mg group), and 37% (10-mg group). The corresponding values for extensive cGVHD are 24.4% (40-mg group) and 17% (20-mg group) and 14.2% (10-mg group). Statistical analysis revealed no significant differences (Figure 3).

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• Figure 3 

  Kaplan-Meier estimated incidences of overall and extensive cGVHD.

Infections 

CMV infections/reactivations requiring preemptive therapy were detected in 38% (10/26), 55% (22/40), and 35% (13/37) of the transplantations with patients at risk in the 40-mg, 20-mg, and 10-mg alemtuzumab groups, respectively. At risk for CMV infection are seropositive patients, those whose donor is seropositive, or when both are seropositive for CMV before transplantation. Two patients in the 10-mg group died of CMV indisease. EBV infection (positive EBV-PCR) or disease (PTLD at any side) developed in 1 patient in the 40-mg group (3%), in 4 patients in the 20-mg group (8%), and in 2 patients in the 10-mg group (4%). EBV pneumonia was the cause of death in 2 patients (40+10-mg groups, 1 each). Adenoviral and respiratoral syncytial viral infections were not observed during the study period. After cessation of their immunosuppression and the routinely used prophylaxis, PjP was detected in 1 patient in the 10-mg group and in 2 patients in the 20-mg group; one patient experienced late toxoplasmosis retinitis (10-mg group).

Response and Relapse 

Eight patients died prior to response evaluation. Of the remaining 119 patients evaluable for disease response, 106 (84%) achieved CR at day +30. Four patients achieved partial remission (PR; 4%), 1 patient had stable disease, and 8 patients were refractory.

The cumulative incidence of relapse according to Kaplan-Meier are 42% in the 40-mg group (11/30; at median day +104), 42% in the 20-mg group (18/48; at median day +173) and 43% in the 10-mg group (19/49; at median day +163), without statistical difference (Figure 4).

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• Figure 4 

  Kaplan-Meier estimated incidence of relapse.

NRM 

The cumulative incidence of NRM at day +100, 1 year and 2 years revealed no differences among the 3 groups as the values were 10%, 20%, and 35% for group 40 mg, 8%, 20%, and 20% for group 20 mg, and 6%, 23%, and 26% for the 10-mg group (Figure 5). Infections were the most common causes of death. By groups, reasons for NRM were infection (n=7), central nervous system (CNS) toxicity (n=1), cardial (n=1), aGVHD (n=1), and cGVHD (n=1) in group 40 mg, infection (n=5), CNS hemorrhage (n=2), primary solid tumor (n=1), aGVHD (n=1), and multiorgan failure (MOF) (n=2) in group 20 mg, and infection (n=6), MOF (n=3) and aGVHD (n=1) in group 10 mg (Figure 5).

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• Figure 5 

  Kaplan-Meier estimated incidence of NRM.

Outcome (Table 3) 

As of December 31, 2008, 62 patients are alive in the 40-mg group 11/30 patients (37%; at median day +1673; range: 1274-1999), 23/48 patients in the 20-mg group (49%; at median day +1132; range: 950-1248), and 28/49 patients in the 10-mg group (57%; at median day +759; range: 601-864). Kaplan-Meier estimates for OS at day +100, 1 year, and 2 years are 77%, 57%, and 50% for the 40-mg group, 90%, 69%, and 58% for the 20-mg group, and 91%, 61%, and 57% in the 10-mg group, with no statistical difference either, respectively (Figure 6).

Table 3. Outcome

MOF indicates multiorgan failure; ARDS, acute respiratory distress syndrome; CNS, central nervous system; EBV, Epstein-Barr virus; CMV, cytomegalovirus; PR, partial remission; CR, complete remission; GVHD, graft-versus-host disease.

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• Figure 6 

  Kaplan-Meier estimation for OS.

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Discussion 

Alemtuzumab is increasingly being used as GVHD prophylaxis in allogeneic RIC-HCT; however, the optimal dose and timing have not been defined. Studies with large patients cohorts of patients have demonstrated the efficacy of 100 mg alemtuzumab as part of the conditioning to reduce GVHD incidence, yet with a far greater incidence of severe viral infections and relapse rates when compared to alemtuzumab-free protocols [15]. Small studies with up to 20 patients have shown that the alemtuzumab dose can be reduced when combined with CsA/MTX treatment post-HCT [8].

To our knowledge, ours is the first observational study examing the deescalation of an alemtuzumab dose still sufficient as GVHD prophylaxis in RIC-HCT. We found low incidences of aGVHD grade II-IV (7.5%-30%) and grade III-IV (7%-11.5%) when 40 mg, 20 mg, or 10 mg, respectively, of alemtuzumab was given 1 to 2 days prior to stem cell infusion, and only 1 patient died of aGVHD. Such low aGVHD rates have also been achieved with 100 mg alemtuzumab 18, 19, 20, 21, and they compare favorably with protocols using standard CsA/MTX GVHD prophylaxis in UD transplantation reducing the incidence of aGVHD grade III-IV [22]. The higher 30% incidence grade II-IV aGVHD in the 20-mg alemtuzumab group probably reflects the higher rate of HLA-mismatches in that patient cohort compared to the 40-mg group. It is striking that we observed no significant difference in the degree of grade III-IV aGVHD between UD and sibling HCT in all 3 alemtuzumab dose groups. Using low-dose alemtuzumab (7.5 mg/m² and 15 mg/m²) in a small trial with sibling transplantation, Dodero et al. [23] also reported a low incidences of aGVHD grade II-IV (11%); however, their post-HCT immunsuppression was more intensive than ours, because it consisted of CsA and MTX.

Further, we did not observe significant differences in overall (37%-44%) and extensive cGVHD (14%-24%).These data compare favorably with overall cGVHD of 11%-36% in other publications using higher alemtuzmab doses 8, 21, 24. However, we observed no statistical differences in our patients for the quality of life compromising extensive cGVHD comparing the 3 groups. The low incidence of extensive cGVHD in the low-dose groups (14% and 17%) compares well with published data for higher doses of alemtuzumab or low doses with additional immunosuppression 8, 23.

With the 10-40-mg alemtuzumab doses used, we observed only 1 graft failure in 1 particular patient who underwent RIC-HCT in an accelerated phase of her MPS. Such low incidences of graft failure have also been shown in earlier trials with 50 mg alemtuzumab in vivo [7]. In contrast, 100 mg alemtuzumab doses given during RIC resulted in a significant rate (3.5%-19%) of primary graft failure 18, 19, 20, 21, 25.

After alemtuzumab medication, patients are at risk of acquiring viral infections (CMV, Epstein-Barr virus [EBV], or Adenovirus) 9, 15, 26 or opportunistic infections like PjP or toxoplasmosis [27] because of T cell lymphocyte depletion. We found similar incidences of CMV infection/reactivation in all dose groups (35%-55%). Higher incidences as of 50% to 70% CMV reactivation have been reported after 100 mg alemtuzumab 15, 20, 21, 26, 28, 29 and up to 2% progressed to CMV-disease despite preemptive therapy [15]. We observed 1 fatal CMV pneumonia and 1 fatal CMV-colitis in addition to aGVHD grade IV of the gut (10-mg group).

Aggressive T cell depletion is also a risk factor for EBV reactivation, disease, and potential PTLD development [30]. We detected EBV infection/disease in 7 patients with no difference among the alemtuzumab doses. Overall, 2 of them died of EBV pneumonia.

The PjP or toxoplasmosis infections occurred very late, when the patients were off immunosuppression. The occurrence of PjP or toxoplasmosis infection after cessation of adequate prophylaxis with either TMS or dapsone/daraprim after alemtuzumab GVHD prophylaxis shows that patients must be examined for individual immunodeficiencies and prophylaxis should be extended. Taken together, the low doses of alemtuzumab used in this study seem to be relatively safe regarding opportunistic infections.

The low incidences of aGVHD and of severe, fatal opportunistic infections are reflected in our low NRM. Although our patients represented a high-risk population for NRM (86% advanced disease and untreated, average age 63 years, 66% UD, 21% mismatched transplantations), day +100 and 1-year NRM was between 6% and 10% and 20% and 23% in the 3 alemtuzumab dose groups. Similarly, low incidences of early (day +100) NRM have been observed in previous studies with higher doses of alemtuzumab, in which an NRM between 0% and 11% 7, 21, 24, 31, 32 and 14% and 17% 19, 20, 26 was detected (mainly after first allo-HCT from matched sibling donors).

As of December 31, 2008 we compared the OS in all groups, with no apparent differences. Nor did we detect any differences among the 3 alemtuzumab doses when considering the cumulative incidence of relapse.

Our analysis on 3 cohorts of a total of 127 consecutive patients demonstrates that the deescalation of in vivo alemtuzumab to 10 mg total dose given on day −1, combined with single agent CsA as posttransplantation immunosuppression, results in adequate suppression of aGVHD and extensive cGVHD without elevating graft failures, viral infections, and early relapse rates especially in sibling and UD allo-HCT. We believe that the optimal therapeutic window of alemtuzumab application in allogeneic HCT lies between a total dose of 10 mg and 20 mg, and that higher doses do not seem necessary in HLA-matched transplantations. Furthermore, the GVHD incidence seems acceptable when 20-mg doses of alemtuzumab are administered in HLA mismatched UD transplantations. Low doses of alemtuzumab should also form the basis for randomized trials when comparing the efficacy of alemtuzumab versus standard GVHD prophylaxis protocols such as CsA/MTX.

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Acknowledgments 

The authors acknowledge the contributions of Elisabeth Lenartz and Petra Isele-Hiss in donor search and coordination, Irmgard Matt in data management, Eva Samek, Ingrid Huber, Waltraud Riedl, and Sabine Enger for technical assistance in the laboratory, Carole Cürten for proofreading assistance, and Roland Mertelsmann for his continuous support. They also thank Martin Bentz, Thomas J. Fischer, Joerg Mezger, Frieder Hirsch, and Wolfram Brugger for patient referral, and the nurses and fellows of ward Löhr for their dedication to the patients.

Financial disclosure: The authors have nothing to disclose.

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