Alemtuzumab as treatment for residual disease after chemotherapy in patients with chronic lymphocytic leukemia

Authors


Abstract

BACKGROUND

The objective of this study was to investigate the efficacy and safety of alemtuzumab, the humanized anti-CD52 monoclonal antibody, in patients with B-cell chronic lymphocytic leukemia and residual disease after chemotherapy.

METHODS

Forty-one patients received alemtuzumab 3 times weekly for 4 weeks. The first 24 patients received 10 mg per dose, and the next 17 patients received 30 mg. All patients received infection prophylaxis during therapy and for 2 months after treatment.

RESULTS

The overall response rate was 46%, including 39% of patients who received the 10 mg dose and responded versus 56% of the patients who received the 30 mg dose. The major reason for failure to respond was the presence of adenopathy. Residual bone marrow disease cleared in most patients, and 11 of 29 patients (38%) achieved a molecular disease remission. The median time to disease progression had not been reached in responders with a median follow-up of 18 months. Six patients remained in disease remission between 24–38 months after therapy. Infusion-related events were common with the initial doses, but all such events were NCI Common Toxicity Criteria Grade 1–2. Infections were reported to occur in 15 patients (37%), and 9 of these infections were reactivation of cytomegalovirus. Three patients developed Epstein–Barr virus positive, large cell lymphoma. Two patients had spontaneous resolution of the lymphoma and, in one patient, the lymphoma resolved after treatment with cidofovir and immunoglobulin.

CONCLUSIONS

Alemtuzumab produced significant responses in patients with residual disease after chemotherapy. Bone marrow disease was eradicated more frequently than lymph node disease, and molecular disease remissions were achieved. A randomized trial comparing alemtuzumab with observation after chemotherapy is indicated. Cancer 2003;98:2657–63. © 2003 American Cancer Society.

Alemtuzumab is a humanized monoclonal antibody comprised of a murine FAB segment joined to a human sequence Fc fragment.1 This antibody binds to CD52, an antigen expressed at high density on both B and T lymphocytes and on monocytes. CD52 is a nonmodulating glycosylated peptide antigen coupled to the membrane by a glycosylphosphatidylinositol anchor.2 Its structure has been elucidated, but its function has not been defined.3 The binding of alemtuzumab to CD52 can produce cell death in three ways: antibody dependent cellular cytotoxicity, complement activation, and direct induction of apoptosis.4, 5 Alemtuzumab has proven effective in the treatment of chronic lymphocytic leukemia (CLL). Based on European data as well as results from the recently published pivotal trial, the U.S. Food and Drug Administration approved alemtuzumab for the treatment of patients with refractory CLL in 2001.6–8 Although it clearly is effective in this setting, the optimal use of the drug may prove to be in patients with less refractory disease, particularly because its efficacy is reduced in the treatment of bulky adenopathy, a frequent component of refractory disease. In a recent European trial, alemtuzumab was administered subcutaneously to previously untreated patients with CLL.8 The overall response rate in that trial was 87%, and the complete response (CR) rate was 19%. Severe infections were rare, likely related to the more functional immune system in these patients compared with patients who had advanced, refractory disease. The current trial was designed to potentiate the use of alemtuzumab by treating patients without bulky disease and to determine whether residual disease after chemotherapy could be eradicated with the use of alemtuzumab.

MATERIALS AND METHODS

Study Design and Patients

Patients with CLL who responded to chemotherapy were treated on study after informed consent was obtained according to institutional guidelines. Patients must have responded to chemotherapy and must have achieved a partial disease remission (PR) or a nodular partial disease remission (nPR) according to the National Cancer Institute (NCI) CLL Working Group guidelines.9 Patients who achieved a CR also were included if they had evidence of residual disease on bone marrow immunophenotyping. Patients were excluded if their creatinine, bilirubin, or transaminases levels were greater than or equal to twice the upper limit of normal; if they had an Eastern Cooperative Oncology Group performance status of 3–4; if they had active infection or had received prior therapy with alemtuzumab; if they had a history of anaphylaxis after exposure to rat-derived or mouse-derived, complementarity-determining region (CDR)-grafted, humanized monoclonal antibodies; or when less than 3 weeks had elapsed since prior chemotherapy. All patients underwent a pretreatment evaluation, including history and physical examination, complete blood counts, differential and platelet counts, liver and renal function studies, bone marrow aspiration, and biopsy and bone marrow samples for immunophenotyping.

Treatment and Evaluation

The initial treatment schema was based on the assumption that, given the minimal disease in these patients, lower doses of alemtuzumab may be efficacious and may produce less immune suppression. Thus, alemtuzumab was administered at a dose of 10 mg 3 times weekly for 4 weeks. If patients still had residual disease, then they were reevaluated 4 weeks later. If residual disease persisted, then they could receive 4 more weeks of alemtuzumab therapy at an increased dose of 30 mg 3 times weekly. The first 24 patients received 10 mg of alemtuzumab 3 times weekly. After initial analysis, subsequent patients received 30 mg of alemtuzumab 3 times weekly for 4 weeks in an effort to increase response rates.

Alemtuzumab was diluted in 100 mL 0.9% saline and administered over 2 hours through an intravenous infusion line containing a 0.22-μm filter. In the first week, the dose was increased from 3 mg to 10 mg (and, later, to 30 mg) as infusion-related reactions were tolerated. Premedication with 50 mg diphenhydramine and 650 mg acetaminophen was used. Patients received prophylaxis for herpes (valacyclovir 500 mg daily or equivalent) and Pneumocystis carinii (trimethoprim sulfamethoxazole 1 tablet twice daily 3 times per week) during therapy with alemtuzumab and for 2 months posttherapy.

Response Criteria

Patients who were treated with alemtuzumab on this study had responded previously to chemotherapy. It was expected that residual adenopathy, if present, would be small in volume. Assessing a PR (i.e., a 50% reduction in small-volume disease) would be difficult. Thus, to consider patients with lymphadenopathy as responders to alemtuzumab, their disease status was required to convert to a CR or an nPR, as defined previously by the NCI Working Group.9 The only residual disease allowed was in the bone marrow. For patients in nPR at the initiation of therapy, response was defined as a conversion to CR. For patients treated in CR with flow cytometric evidence of disease, flow negativity defined response.

Statistical Considerations

Distributions of survival and time to disease progression were estimated using the method of Kaplan and Meier.10 Survival intervals were measured from the first day of therapy until death; deaths from all causes were included. The time to disease progression was measured from the initiation of therapy until disease recurrence.

RESULTS

Patient Characteristics

Forty-one patients with residual disease after chemotherapy were treated with alemtuzumab. Patient characteristics are detailed in Table 1. The median age was 60 years (range, 44–79 years). Most patients had normal blood counts at the initiation of therapy with alemtuzumab. The median hemoglobin level was 13.5 g/dL (range, 9.5–15.5 g/dL), the median leukocyte count was 4.7 × 103/μL (range, 1.5–16 × 103/μL), and the median platelet count was 135 × 103/μL (range, 41–263 × 103/μL. Prior response to chemotherapy was PR in 21 patients, nPR in 17 patients, and CR in 3 patients. The number of prior regimens was heterogeneous and ranged from 1 to 7 regimens with a median of 2 regimens. At the start of therapy, 13 patients had palpable adenopathy, 7 patients had > 30% lymphocytes in the bone marrow aspirate, 32 patients had nodules in the bone marrow biopsy, and 29 patients had bone marrow residual disease detected by immunophenotyping.

Table 1. Patient Characteristics (n = 41 Patients)
CharacteristicNo. of patients%
  1. PR: partial remission; nPR: nodular partial remission; CR: complete remission.

Age > 60 yrs2151
No. of prior regimens  
 11434
 2–32049
 ≥ 4717
Response to chemotherapy  
 PR2151
 nPR1741
 CR37
Maximum lymph node size (cm)  
 02868
 1–2717
 3614

Efficacy

Overall, 46 % of patients responded to alemtuzumab therapy. Nine of 23 patients (39%) who were treated at the 10-mg dose level responded, compared with 9 of 16 patients (56%) who were treated at the 30-mg dose level (P value not significant). One patient at each dose level was inevaluable for response. One patient who was treated at the 10-mg dose level had no evidence of disease prior to therapy with alemtuzumab. One patient who was treated at the 30-mg dose level had disease documented on bone marrow biopsy before treatment, but the posttherapy bone marrow was a subcortical specimen that was inadequate for evaluation. Both patients were evaluable for toxicity. Four patients received alemtuzumab 10 mg followed by alemtuzumab 30 mg, and none of those patients responded. The major reason for failure to respond was the presence of residual adenopathy. Response by site of disease is shown in Table 2. Only 2 of 13 patients had resolution of adenopathy, although only 6 patients had lymph nodes that measured > 2 cm in greatest dimension prior to alemtuzumab treatment. Seven patients began therapy with alemtuzumab with bone marrow aspirates that demonstrated > 30% lymphocytes (range, 45% to 60%). Six of those 7 patients had < 30% lymphocytes (range, 10% to 35%) after alemtuzumab therapy. Bone marrow nodules were observed in 32 patients at the start of therapy. One patient had a bone marrow biopsy specimen that was inadequate for evaluation after therapy. Fifteen patients (48%) had clearance of nodules after alemtuzumab. When evaluated by alemtuzumab dose level, 39% patients who received alemtuzumab 10 mg had clearance of bone marrow disease compared with 67% of patients who received alemtuzumab 30 mg (P = 0.14). Immunophenotyping showed residual bone marrow disease in 31 patients. One patient had no evidence of disease at the start of therapy and was evaluated only for safety. Nine patients had no evidence of disease on immunophenotyping at the start of therapy with alemtuzumab. The only evidence of disease in two patients was residual adenopathy. One patient had adenopathy and nodules on bone marrow biopsy. The remaining six patients had nodules on bone marrow biopsy. The aspirate specimen that was sent for flow cytometry may not have reflected residual disease, because it was localized to the nodules.

Table 2. Response to Alemtuzumab by Disease Site
ParameterNo of patients (%)
EvaluableResponders (%)
  1. PCR: polymerase chain reaction.

Lymph nodes13 2 (13)
Bone marrow nodules3115 (48)
Bone marrow lymphocytes > 30%7 6 (86)
Immunophenotyping2925 (86)
PCR2911 (38)

After therapy with alemtuzumab, two patients did not have a sample sent for immunophenotyping. Twenty-five of 29 evaluable patients (86%) had negative results on immunophenotyping. Molecular responses were assessed using a polymerase chain reaction (PCR) for the specific immunoglobulin heavy chain rearrangement. Information was available on 29 patients. Eleven of 29 patients (38%) achieved molecular remission.

Safety

Infusion-related events occurred in most patients and included predominantly fever and chills.(Table 3) Fleeting urticarial rashes also were common. All infusion-related toxicities were NCI Common Toxicity Criteria Grade 1–2. No Grade 3–4 infusion-related events were noted.

Table 3. Infusion Toxicitya
ToxicityPercent of patientsb
TotalGrade 1Grade 2
  • a

    NCI Common Toxicity Criteria

  • b

    There were no NCI Grade 3–4 infusion-related toxicities.

Fever953759
Chills90783
Rash662046
Nausea and emesis564610
Fatigue544410
Headache27207
Myalgia251510
Diarrhea1577

Myelosuppression was not infrequent during therapy with alemtuzumab. Neutropenia occurred in 85% of patients, with Grade 3–4 neutropenia occurring in 30% of patients. Grade 3–4 neutropenia was more common at the 30-mg alemtuzumab dose level (71% vs. 17% at the 10-mg alemtuzumab dose level). Thrombocytopenia occurred in 93% of patients, but only 14% of patients experienced Grade 3–4 thrombocytopenia. There was no significant difference in the incidence of thrombocytopenia according to the dose level of alemtuzumab. Anemia developed in 58% of patients. Grade 2–3 anemia occurred in 17% of patients., and Grade 4 anemia was not observed. Grade 2–3 anemia was more common at the 30-mg alemtuzumab dose level (35% vs. 4% at the 10-mg alemtuzumab dose level).

Infections occurred in 15 patients (37%). These included one presumed viral myocarditis that completely resolved, one Listeria infection in a patient who was allergic to sulfa, one pneumonia of unknown origin, one septicemia, one episode of sinusitis, and one episode of influenza A that subsequently progressed to pneumonia. Nine of the infections were related to reactivation of cytomegalovirus (CMV) that was documented in seven patients by positive antigenemia and, in one patient, by CMV in the urine, all associated with fever. One patient developed fever and was admitted to a local hospital where CMV testing was not available: Because the fever was persisting on broad-spectrum antibiotics, ganciclovir was added, and the fever resolved. One patient developed CMV hepatitis, which led to liver failure and death. More information on that patient is provided below in the discussion about Epstein–Barr virus (EBV) large cell lymphoma (LCL).

Three patients developed EBV positive LCL, a somewhat unexpected finding in this setting. The first patient was a man age 56 years with a 5-year history of CLL who had received prior therapy with chlorambucil and prednisone, fludarabine, and splenectomy. His most recent treatment, a combination of fludarabine, cyclophosphamide, and granulocyte-macrophage–colony stimulating factor, induced a PR. Residual disease included small inguinal lymph nodes, 52% bone marrow lymphocytes, nodular disease on biopsy, and positive immunophenotyping. He was treated with alemtuzumab 10 mg 3 times weekly for a total of 12 doses and was not categorized as a responder, because the inguinal adenopathy did not resolve (although bone marrow disease improved). Six weeks later, he developed a rapidly enlarging, 8 cm × 4 cm cervical lymph node. A biopsy showed features of both LCL and Hodgkin disease. In situ hybridization for EBV was positive. The patient refused chemotherapy. At follow-up 4 months later, he had spontaneous regression of the lymph node to 0.5 cm. A fine-needle aspirate was nondiagnostic. Four months later, the patient had progressive adenopathy, leukocytosis, anemia, and thrombocytopenia. Bone marrow analysis demonstrated extensive CLL, and a fine-needle aspirate from the cervical node showed only small lymphocytic lymphoma. He was treated with fludarabine, cyclophosphamide, and rituximab but died from sepsis during the first course, 9 months after the presentation with EBV LCL.

The second patient was a man age 55 years with a 6-year history of CLL who had previously received fludarabine and mitoxantrone and, subsequently, fludarabine and cyclophosphamide. Residual disease included 1-cm axillary lymph nodes. He received alemtuzumab 10 mg 3 times weekly for 12 doses and achieved a CR. Six weeks after finishing therapy, he developed a rapidly enlarging, scapular mass, and an excisional biopsy showed CD-30 positive LCL mixed with cytotoxic T cells. In situ hybridization for EBV was positive. It was also found that he had a 3 × 4 cm lung mass; a fine-needle aspirate revealed only necrotic tissue. The patient received no treatment; 1 month later, both the scapular mass and the lung mass had regressed. The patient remained in continuous CR 18 months later.

The third patient was a man age 58 years with a 5-year history of CLL treated previously with chlorambucil, fludarabine, and cyclophosphamide and, most recently, with fludarabine, cyclophosphamide, and amifostine, to which he achieved a PR. He received alemtuzumab 10 mg 3 times weekly for 12 doses but without complete resolution of residual adenopathy; 1 month later, he received a second cycle of treatment at the escalated alemtuzumab dose of 30 mg for 12 doses. Immediately after completing this therapy, he developed severe thrombocytopenia to 19,000/μL and gastrointestinal hemorrhage. Endoscopy revealed multiple gastric ulcers; a biopsy showed LCL that subsequently was found to contain EBV. He was treated with intravenous immunoglobulin and cidofovir, and reendoscopy 1 month later showed no ulcers. However, approximately 2 weeks later, he developed rapidly rising liver functions tests and died within 3 days with fulminant hepatic failure. Autopsy showed no evidence of EBV but diffuse CMV.

Duration of Disease Remission and Survival

The median time to disease progression in patients who responded to alemtuzumab has not been reached at a median follow-up of 18 months; 6 patients remain in disease remission between 24 months and 38 months after therapy (Fig. 1). There was some suggestion that the dose of alemtuzumab may have an impact on the time to disease progression in responders: Four of 9 responders who were treated at the 10-mg dose level developed recurrent disease, compared with only 1 of 9 responders who were treated at the 30-mg dose level (P = 0.20) Although there was no significant difference in response according to the dose of alemtuzumab, this may have been related to the small number of patients. When all patients were analyzed according to their PCR status after alemtuzumab, patients who had positive PCR results had a median time to disease progression of 15 months; patients who lacked PCR data had a median time to disease progression of 9 months, and the median time to disease progression has not been reached for patients who had negative PCR results (Fig. 2).

Figure 1.

Time to disease progression in patients who responded to alemtuzumab.

Figure 2.

Time to disease progression by polymerase chain reaction (PCR) status after treatment with alemtuzumab.

DISCUSSION

Improved chemotherapeutic regimens have produced higher overall response rates in the treatment of CLL. In a randomized Intergroup trial, fludarabine was more effective than chlorambucil for initial treatment of CLL, resulting in an overall response rate of 63% and a CR rate of 20%.11 It is noteworthy that, with the best single-agent therapy, 80% of previously untreated patients were unable to achieve a morphologic CR. Studies utilizing chemotherapy combinations are resulting in higher CR rates, and molecular disease remissions may occur.

Improvements in morphologic and molecular CR rates may impact the duration of disease remission because, in CLL, remission duration correlates with the quality of the disease remission. Patients who were treated with a combination of fludarabine and cyclophosphamide and achieved a PR, nPR, or CR had disease remission durations of 22 months, 30 months, and 57 months, respectively. Patients who achieved a morphologic CR with less residual disease, as documented by the inability to detect bone marrow CD-5 positive B cells by flow cytometry, had a longer duration of disease remission compared with patients who had residual disease.12–15

Currently, the standard approach to CLL is that patients are treated until their best response is achieved and are then observed until evidence of disease progression. The objective of this study was to determine whether alemtuzumab therapy would eliminate persistent disease after chemotherapy.

Although alemtuzumab is effective in the treatment of patients with refractory CLL, a limitation is its ability to reduce bulky lymph node sites. Using alemtuzumab to treat minimal (to moderate) residual disease would abrogate the issue of bulky adenopathy, because patients would have responded to prior chemotherapy. In addition, if the mechanism of action of alemtuzumab differed from that of chemotherapy or other antibodies, then resistant cells that escaped cell killing from chemotherapy may be eradicated by alemtuzumab.

Recently, Montillo et al. described nine patients with CLL who had residual disease after fludarabine therapy and were treated with subcutaneous alemtuzumab 3 times weekly for 6 weeks in escalating doses up to 10 mg.16 At the initiation of treatment, one patient was in CR, five patients were in nPR, and three patients were in PR. CR was achieved by three of five patients in nPR and by two of three patients in PR. Three patients converted to a molecular disease remission. Three patients in that study developed reactivation of CMV.

Because alemtuzumab depletes T cells and is immunosuppressive, the original study design used a lower than standard dose of alemtuzumab (10 mg) due to the fact that these patients had less disease and the potential to respond to a lower dose with less risk of infection. The regimen incorporated a 4-week rest period before a second cycle because of emerging data indicating that patients who are treated with rituximab may continue to respond for several months after the last dose. Patients who had not achieved a CR could be retreated with alemtuzumab for another 4 weeks at the standard dose of 30 mg.

After the first 24 patients were entered, this schema was changed for several reasons: 1) The response rate was 39%, and a higher dose of alemtuzumab (the standard 30-mg dose) might have resulted in greater efficacy; and 2) the schema was cumbersome, and there were no data to suggest that patients continued to respond to alemtuzumab after the last dose. Thus, the final schema used an alemtuzumab dose of 30 mg 3 times weekly for 4 weeks and no further therapy.

Overall, 18 of 39 evaluable patients (46%) responded. The response rate was 39% with alemtuzumab 10 mg compared with 56% with alemtuzumab 30 mg (P value not significant). The main reason for lack of response was the inability of alemtuzumab to eradicate adenopathy completely. In fact, when patients with adenopathy were excluded from the analysis, the overall response rate rose to 59%. Although shrinkage in lymph node size was seen, the response criteria required complete resolution of adenopathy. In contrast, the effects of alemtuzumab on bone marrow disease were impressive. Seventy-three percent of patients experienced significant improvements in bone marrow disease by morphology or immunophenotyping. Perhaps most striking is that 11 of 29 evaluable patients (38%) achieved negative PCR results after treatment with alemtuzumab. Preliminary data suggest that patients who achieve negative PCR results may experience longer disease remission durations (Fig. 2). The current trial was designed with an endpoint of response rather than disease remission duration. Because the median number of prior regimens was two (with a range up to seven regimens), the fact that the median time to disease progression had not been reached at a median follow-up of 18 months appears favorable.

Infusion-related events, as expected, occurred in most patients but were manageable. No Grade 3–4 infusion-related side effects occurred, perhaps because of the absence of leukocytosis and bulky disease at the start of therapy.

Reactivation of CMV occurred in 9 patients (22%), consistent with our experience with alemtuzumab in other studies. There was no significant difference in the incidence of CMV reactivation by dose (21% of patients treated with alemtuzumab 10 mg vs. 31% of patients treated with alemtuzumab 30 mg). None of the 4 patients who received alemtuzumab 30 mg and received prophylactic ganciclovir had reactivation of CMV, suggesting that CMV prophylaxis should be considered. Most patients had fever that did not respond to broad-spectrum antibiotics but responded rapidly to CMV-directed antibiotic therapy. Only 1 patient died from complications of CMV: This was the same patient who developed EBV LCL and was 1 of only 4 patients who received both 1 month of alemtuzumab 10 mg 3 times weekly and 1 subsequent month of alemtuzumab 30 mg 3 times weekly, suggesting that immunosuppression may have been more severe.

A striking finding was the development of EBV LCL in three patients, all of whom had resolution without chemotherapy. Two patients had spontaneous resolution of disease, and one patient received intravenous immunoglobulin and cidofovir. In trials using alemtuzumab in the transplantation setting, the development of posttransplantation lymphoproliferative disorder has been uncommon, and it was hypothesized that the use of alemtuzumab to deplete T cells did not lead to this complication, because it was also depleting B cells. In the current trial, it was assumed that the immunosuppression related to alemtuzumab resulted in the proliferation of EBV positive cells, because the LCL resolved without therapy in two patients with more time elapsed after treatment with alemtuzumab.

In the current study, alemtuzumab after chemotherapy was found to improve the response rates in approximately 50% of patients with CLL who wee treated; most responses occurred in patients who had residual bone marrow disease. Molecular disease remissions were achieved in 38% of patients, and preliminary data suggest that this may impact the time to disease progression. Infections still are of concern, and reactivation of CMV may occur and require treatment. Nevertheless, the promising results observed suggest that studies in which patients who responding to chemotherapy would be randomized to either observation or alemtuzumab therapy would be of interest.

Ancillary