An overview of the current clinical use of the anti-CD20 monoclonal antibody rituximab

J. Boye, T. Elter and A. Engert+

Clinic I of Internal Medicine, University Hospital of Cologne, Cologne, Germany

Received 1 July 2002; revised 18 October 2002; accepted 20 November 2002

Abstract

The chimeric anti-CD20 monoclonal antibody rituximab has become part of the standard therapy for patients with non-Hodgkin’s lymphoma (NHL). To date, more than 300 000 patients have been treated with rituximab worldwide, including patients with indolent and aggressive NHL, Hodgkin’s disease and other B-cell malignancies. Combination of rituximab with cytotoxic agents or cytokines has been explored in a number of different studies. Rituximab is now also approved for patients with diffuse large B-cell lymphoma when combined with standard CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine and prednisone). The monoclonal antibody is generally well tolerated. Most adverse events are infusion-associated, including chills, fever and rigor related to the release of cytokines.

Key words: chronic lymphocytic leukemia, clinical studies, Hodgkin’s disease, non-Hodgkin’s lymphoma, rituximab

Introduction

Since the initial description by Köhler and Milstein [1], monoclonal antibodies have increasingly been used in the diagnosis of malignant diseases. However, many problems were encountered when monoclonal antibodies were developed as specific antitumor reagents. This has changed with the advent of rituximab, a chimeric human/mouse monoclonal antibody directed against the CD20 antigen. The use of rituximab in the treatment of relapsed or refractory indolent CD20+ B-cell non-Hodgkin’s lymphoma (NHL) was endorsed by the US Food and Drug Administration in December 1997. Shortly thereafter, rituximab was also approved in Europe under the trade name MabThera® (Hoffmann-La Roche AG) for patients with advanced stage chemoresistant or relapsed follicular NHL. More recently, rituximab was also approved in the USA and in Europe for the treatment of aggressive NHL when combined with standard chemotherapy. Worldwide, more than 300 000 patients have been treated so far, including patients with other malignancies and autoimmune disorders. The rapidly increasing bulk of data makes it difficult to keep abreast of the most recent developments. Here, we review the current clinical results with rituximab.

Biological activity

Rituximab is a chimeric human/mouse antibody with human constant regions and mouse variable regions (Figure 1) isolated from a murine anti-CD20 antibody (IDEC 2B8) [2]. The murine 2B8 antibody and the chimeric C2B8 antibody (rituximab) are very similar in terms of specificity and affinity. Compared with its murine counterpart, however, rituximab has a longer half-live in humans, interacts with human effector cells [2, 3], and is less immunogenic [4]. Rituximab binds avidly to the CD20 antigen, which is expressed on 95% of B-cell lymphoma cells and on normal B-cells. Importantly, CD20 is not present on precursor B-cells or stem cells. The antigen is expressed at lower levels on chronic lymphocytic leukemia (CLL) and plasma cells [5, 6]. The CD20 antigen is appealing for a selective immunotherapy for several reasons: CD20 does not circulate in the plasma [5], it is not shed from the surface of CD20+ cells after antibody binding and it is not internalized or downregulated [3]. Although the function of CD20 is not fully understood, factors such as complement-dependent lysis [2], effector cell-mediated lysis [7], induction of apoptosis and interference with calcium influx into the cell contribute to the antitumor activity [8].



View larger version (28K):
[in this window]
[in a new window]
 
Figure 1. The chimeric human/mouse monoclonal antibody rituximab.

 
Indolent and follicular lymphoma

The efficacy and safety of rituximab given as a single agent in relapsed indolent and follicular lymphoma were established in an international pivotal multicenter trial [9]. A total of 166 patients received four weekly doses of 375 mg/m2. In the intention-to-treat group the overall response rate (ORR) was 48%, including 6% complete responses (CR) and 42% partial responses (PR). A recently performed retrospective re-analysis of these data using newly standardized response criteria [10] showed a higher ORR (62%) and more CRs (32%). The majority of the non-responders had a mean decrease of measurable disease of 32%. Overall, only 13% of patients had no response or progressive disease, as shown in Figure 2. Median time to progression (TTP) was 13.2 months for responders and duration of response (DR) 11.6 months.



View larger version (35K):
[in this window]
[in a new window]
 
Figure 2. Rituximab pivotal trial: maximum percentage change in tumor size. Tumor shrinkage was measured radiographically by the product of perpendicular lesion diameters. Data for three patients are unavailable. *Includes two patients with >100% increase in lesion size. {dagger}Patients with no change in tumor size are represented by the area of no change on the y-axis.

 
Adverse events such as fever, chills, nausea and aches were mainly associated with the first infusion and were typically modest. Most patients (55%) had no toxicity at subsequent infusions. The median values for hemoglobin, platelets, leucocytes and granulocytes remained within normal limits throughout the treatment period. Apart from a nearly complete elimination of B-lymphocytes in 86% of patients, other cells were mainly unaffected. No significant changes were observed in serum immunoglobulin levels. Infections that occurred for up to 1 year after therapy were mainly of bacterial origin (37 of 68) and generally mild (61 of 68 grade 1/2). Bcl-2 became negative in the peripheral blood in 62% and in the bone marrow in 56% of patients after 3 months. These data suggest that rituximab has a superior potency to induce molecular remissions when compared with cytotoxic agents.

Prognostic factors
Patients who had received only one prior treatment showed an ORR of 57%. In contrast, those who had three or more regimens before treatment with rituximab had an ORR of 38%. The ORR was 35% in patients with lesions >7 cm. This contrasts with most of the available literature documenting a clear relationship between bulky disease and both shorter survival and lower response to chemotherapy [11]. Davis et al. [12] treated 31 patients with bulky disease of >=10 cm with four weekly infusions of rituximab and reported an ORR of 43% with a median TTP for the responders of 8.1 months. More grade 3/4 events were reported compared with the pivotal trial, but no patient developed a tumor lysis syndrome.

First-line treatment of indolent and follicular lymphoma
Colombat et al. [13] treated a group of 50 previously untreated patients with follicular NHL with a standard four-dose course of rituximab. Of the 36/49 patients who were responders on day 78, 10 patients progressed during the first year of follow-up. Of note, seven of 23 patients in PR on day 78 were in CR/CR (unconfirmed) (CRu) at 12 months after treatment. If the response rates at any staging during the first year of follow-up are considered, the ORR was 80% and the CR/CRu rate 41%, respectively. Thirty-two of 48 patients had been positive for the t(14;18) translocation before treatment. Interestingly, 17 of 30 (57%) were negative on day 50 after rituximab treatment in the peripheral blood, with 31% negative in bone marrow.

Hainsworth [14] conducted a phase II trial in 62 patients with indolent lymphoma also using the 4-dose schedule as first-line therapy. Treatment was repeated every 6 months in responding patients for a maximum of up to four courses. At week 6 after the first course, 47% of the patients had objective responses (7% CR). Forty-six patients received two or more rituximab courses (two courses, 10; three courses, 13; four courses, 23) with response rates increasing to 65% (27% CR). Repeated courses of the antibody at 6-month intervals improved responses in 30% of the patients without increasing toxicity. The 1- and 2-year progression-free survival (PFS) for all patients were 69% and 67%, respectively.

Retreatment
Davis et al. [15] conducted a clinical trial evaluating rituximab in the retreatment of 58 patients with relapsed low-grade or follicular B-cell NHL who had responded to at least one prior course of rituximab. In general, rituximab was well tolerated in this setting. Significant clinical activity was observed with an ORR of 38% (10% CR, 28% PR) in the intention-to-treat group. The median TTP was 17.8 months and DR was 16.3 months. This was longer than the TTP and DR achieved in these patients prior to treatment with rituximab (TTP 12.4 months and DR 9.8 months). The median interval between the courses was 14.5 months (range 3.8–35.6 months). These results were confirmed by Igarashi et al. [16], suggesting that retreatment with rituximab is save and feasible.

Development of resistance is characteristic for B-cell lymphoma upon repeated treatment with conventional chemotherapy. In contrast, the selection of CD20– lymphoma cells in patients treated with rituximab is rarely observed. Therapeutical trials showed a primary response rate of 50%, and a secondary response rate of 44% in prior responders [17]. Possible mechanisms of resistance include uncoupling of the apoptotic signal initiated by rituximab, an inhibited immune response by complement-resistance proteins, or reduction of CD20 expression below a critical threshold. The most relevant clinical trials of rituximab in low-grade and follicular NHL are shown in Table 1.


View this table:
[in this window]
[in a new window]
 
Table 1. Current studies using single-agent rituximab in indolent and follicular NHL
 
Combined modality treatment of rituximab and chemotherapy
Preclinical studies have indicated that rituximab can sensitize resistant malignant cells to the effect of cytotoxic agents [18]. Underlying mechanisms for a possible synergism were analyzed for the combination of fludarabine and rituximab, showing that fludarabine downregulates the membrane expression of CD55, which serves as an anticomplement protein [19]. In preclinical studies, rituximab was subsequently shown to potentiate the cytotoxicity of fludarabine [20]. Thus, the concept of concomitant administration of the antibody and chemotherapy is appealing.

Czuczman et al. [21] published data on the combined use of rituximab and fludarabine in 40 patients with follicular lymphoma. The ORR was 90% in the intention-to-treat group (CR/CRu 82.5%, PR 7.5%). The first report demonstrating the efficacy and safety of rituximab in combination with standard-dose CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) in low-grade lymphoma patients was published by the same group [22]. Two antibody infusions were administered before CHOP with the rationale of making use of a possible rituximab-induced sensitization to cytotoxic agents and also to saturate CD20 binding sites. The third and fourth rituximab infusion were given together with the chemotherapy. Thirty-eight of 40 patients responded, 55% with a CR, which compares favorably with similar studies when CHOP was given alone [23]. In an update, 21 patients were in remission between 46.8 and 86.3 months after treatment [24]. Median DR was 63.3 months with median PFS not reached after a median observation time of 65.1 months. Seven of the eight bcl-2-positive patients converted to PCR negativity after the combined treatment. Importantly, there was no evidence of additive toxicity. When rituximab was administered after CHOP, response rates appeared to be lower (CR/CRu 54%, PR 18%), but possible additional antitumor activity was demonstrated as measured by the clearance of bcl-2 [25].

The combination of FND (fludarabine, mitoxantrone and dexamethasone) with rituximab was shown to be effective and associated with modest side-effects in the treatment of indolent lymphoma [26, 27]. A prospective, randomized multicenter trial of the German Low Grade Lymphoma Study Group randomized between FCM (fludarabine, cyclophosphamide, mitoxantrone) or FCM in combination with rituximab [29]. To date, 43 patients with relapsed follicular lymphoma are evaluable. The ORR was 95% in the combined immunochemotherapy group and 68% in the FCM group.

Other trials using rituximab combined with different regimens such as cyclophosphamide/dexamethasone [29], fludarabine/mitoxantrone [30], bendamustine [31, 32] or mitoxantrone/chlorambucil/prednisone (MCP) [33] suggest that a combined immuno-chemotherapy is generally safe and might give superior clinical results.

Table 2 summarizes the clinical trials in which rituximab was combined with chemotherapy in patients with low-grade and follicular NHL.


View this table:
[in this window]
[in a new window]
 
Table 2. Clinical studies using rituximab combined with chemotherapy in indolent and follicular NHL
 
Rituximab combined with interferon
Interferon (IFN)-{alpha} has a potential synergistic antitumor effect with monoclonal antibodies [34]. This synergism is probably related to an IFN-induced upregulation of antigen expression [35], which results in a better targeting of antibodies to tumor cells [36] and possibly enhanced cytotoxicity [37]. Therefore, different trials investigated safety and efficacy of rituximab in combination with IFN (Table 3).


View this table:
[in this window]
[in a new window]
 
Table 3. Clinical studies using rituximab combined with interferon in indolent and follicular NHL
 
Davis et al. [38] performed a 12-week trial involving 38 patients with relapsed or refractory low-grade or follicular lymphoma. IFN was given three times each week [weeks 1–12, 5 million International Units (MIU)]; rituximab was administered at standard doses (weeks 5–8). The ORR of 45% (CR 11%) compares to the response rates observed with rituximab alone [9], but TTP was more durable (25.2 months). No unexpected toxicities occurred, and most adverse events were classified as IFN- related. In other low-grade lymphoma studies, the response rate ranged from 49% (F. Offner, presented at the rituximab meeting in Montreux, 2001) to 70% [39] and median DR was ~20 months.

Kimby et al. [40] treated 69 patients with low-grade or follicular lymphoma who had a PR or minor response after a first course of rituximab with additional four doses of the antibody with or without IFN in a randomized fashion. Co-administration resulted in more CRs (48% versus 23%).

Although the current evidence is rather limited, combining IFN with rituximab might be an option for patients who have difficulty tolerating chemotherapy. In addition, this is an interesting combination for possible use as maintenance therapy in patients with minimal residual disease after induction treatment.

Stem cell transplantation
A number of trials in which rituximab was used both before stem cell collection and after transplantation have been published (Table 4), and indicate that this approach is safe as far as mobilization and engraftment is concerned. The amount of tumor cell contamination in the stem cell product can be reduced and an increase in molecular remission following transplant has been suggested [4145]. The use of rituximab in combination with autologous peripheral stem cell transplantation (ASCT) is also promising in patients with aggressive NHL.


View this table:
[in this window]
[in a new window]
 
Table 4. Clinical studies using rituximab in patients undergoing high-dose chemotherapy and stem cell transplantation
 
Dosing and scheduling
The standard dose of rituximab is 375 mg/m2 given once a week for a total of four applications. In the pivotal trial [9], the mean serum half-life after the first infusion was shorter than after the fourth infusion (76.3 versus 205.8 h), and the maximum observed concentration was higher after the fourth compared with the first infusion (mean 465 versus 206 µg/ml). Median serum antibody levels were higher compared with non-responders (502.8 versus 412.4 µg/ml, respectively; P = 0.010).

Several investigators have evaluated modifications of the current schedule. For patients with CLL or bulky tumor, other schedules might be more suitable. Alternative approaches included higher doses [50] or an increase of the number of applications given [51]. Piro et al. [52] conducted a phase II trial in which eight weekly infusions of rituximab were evaluated in patients with refractory or relapsed indolent NHL. Of 35 evaluable patients, 14% achieved CR and 46% PR. Patients with bulky disease also responded including 25% of those with lesions >7 cm. The median post-infusion serum levels plateaued after the sixth infusion (range 518.1–558.1 µg/ml). Most adverse events were mild and similar to those seen in previous studies.

Rituximab in aggressive NHL

A single-arm, open-label phase II study evaluated the clinical activity of rituximab in combination with CHOP as first-line treatment of aggressive NHL [53]. The patient population consisted of histologically documented aggressive lymphoma excluding patients with mantle cell, lymphoblastic or Burkitt’s lymphoma. Treatment was administered at 21-day intervals, with rituximab given on days 1 and 3 of each cycle at standard doses. Toxicity was similar to that expected with each treatment alone. ORR was 94% (31 of 33 patients), with a CR rate of 61%. Intermediate and high-risk patients [International Prognostic Index (IPI) score >=2] had remissions sustained for at least 2 years.

The first large, prospectively randomized multicenter trial in previously untreated patients with aggressive NHL was performed by the French GELA, comparing CHOP alone with a rituximab–CHOP combination (R-CHOP) [54]. This study involved 399 elderly patients (aged 60–80 years) with diffuse large cell lymphoma (stage II–IV). With a median follow-up of 24 months, R-CHOP led to significantly more CRs (76% versus 63%, P = 0.005), 2-year event-free survival (EFS) (57% versus 38%, P <0.001) and overall survival (OS) (70% versus 57%, P = 0.007) compared with CHOP alone (Figure 3). This study documented a significant benefit of the combined immunochemotherapy in both patients with low-risk IPI (P <0.001) and those with high-risk IPI (P <0.03). There was no major difference between the two arms in terms of toxicity or severe infections. Thus, this ‘proof of concept’ study showed that the addition of rituximab to conventional CHOP is associated with superior results, and therefore suggests R-CHOP as the new standard for elderly patients with aggressive NHL.



View larger version (10K):
[in this window]
[in a new window]
 
Figure 3. Rituximab ± CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) for previously untreated aggressive non-Hodgkin’s lymphoma: Overall survival [54].

 
In the USA, a similar study conducted by the Eastern Cooperative Oncology Group (ECOG), Cancer and Leukemia Group B (CALGB) and the Southwest Oncology Group (SWOG) is currently underway. In addition, a large international study (MINT) is also evaluating the combination of rituximab and CHOP-like chemotherapy in previously untreated younger patients with aggressive NHL.

There is, however, only limited information on the single-agent efficacy of rituximab in relapsed aggressive NHL. Rituximab was investigated in a small dose-finding study in 54 patients [55], most of whom were in their first or second relapse after initial chemotherapy. Patients were randomized between the standard dose of 375 mg/m2 given eight times or a first infusion of standard dose rituximab followed by seven infusions of 500 mg/m2. The ORR was not significantly different between the two groups, with an ORR of 31% in the intention-to-treat group. The higher dose of rituximab was slightly less well tolerated compared with the standard dose. Others have demonstrated activity of single-agent administration of rituximab in relapsed aggressive NHL (M. Reiser, presented at the rituximab meeting in Montreux, 2001).

For patients with relapsed or refractory aggressive NHL, combinations of high-dose chemotherapy and rituximab followed by ASCT are an interesting new option. Recently published data suggest that the addition of rituximab to the ICE (ifosfamide, carboplatin, etoposide) regimen may significantly increase the CR rate achieved with ICE alone (55% versus 28%, respectively) without increasing toxicity [56]. Horwitz et al. [57] suggested that rituximab as adjuvant therapy after ASCT might lead to higher OS and PFS than expected with conventional ASCT regimens.

A rituximab–EPOCH (doxorubicin, etoposide, vincristine, cyclophosphamide, prednisone) regimen was found to be effective and well tolerated both in heavily pretreated patients with aggressive NHL (R. Stahel, presented at the rituximab meeting in Montreux, 2001) and in untreated patients [58]. Several smaller studies with different regimens combined with rituximab also point towards possible superior effects.

An overview of studies of rituximab in aggressive NHL is given in Table 5.


View this table:
[in this window]
[in a new window]
 
Table 5. Clinical studies using rituximab in patients with aggressive NHL
 
Mantle cell lymphoma

Rituximab has shown activity in patients with mantle cell lymphoma (MCL) with responses ranging from 20% to 38% [48, 55, 60, 61]. In a study conducted by Foran et al. [60] the ORR was 37% in 67 patients, with CR in 14% of the pretreated patients. The projected median DR in MCL was 1.2 years, with no difference between previously treated and untreated patients.

A phase II trial is ongoing to evaluate the concurrent use of rituximab plus CHOP in patients with newly diagnosed MCL [62]. Preliminary results including 39 patients show response rates of 96% with 48% CR. Nine of 25 patients who were bcl-1-positive at diagnosis showed PCR negativity after therapy. However, patients who achieved molecular remissions in peripheral blood or bone marrow had PFS similar to those without molecular response (16.5 versus 18.8 months; P = 0.51). Thus, the possible benefit of this regimen has to be determined in larger studies.

In a randomized German multicenter trial, 37 patients with relapsed MCL were treated with FCM alone or in combination with rituximab [28]. An ORR of 77% was observed in patients treated with the combined immunochemotherapy compared with 27% in the FCM group. The estimated risk reduction for relapse of 63% suggested a superior efficacy of rituximab plus FCM compared with FCM alone (P = 0.0107), although the number of patients is too small for final conclusions to be drawn.

Peripheral stem cell transplantation (PSCT) is increasingly being evaluated as first-line treatment for patients with MCL. Results reported thus far using additional treatment with rituximab in this setting are encouraging: all patients achieved clinical CRs after post-transplant therapy with rituximab, and most also had molecular remissions (71.5% to 100%) [41, 42, 63, 64]. For comparison, high-dose chemotherapy alone was effective in only one of nine cases [65], and ex vivo purging failed to eradicate PCR-detectable disease in most patients [66].

More recently, 77 previously untreated MCL patients received rituximab combined with the HyperCVAD-Methotrexate/Ara-C regimen (HCVAD) without PSCT [67]. In this study, the combination of the antibody and HCVAD in retrospective analysis appears equivalent to HCVAD with PSCT in patients <66 years old, and superior in older patients. Longer follow-up and confirmatory studies are, however, warranted.

Although the data available so far suggest a benefical role of rituximab in the treatment of MCL (Table 6), randomized trials with larger numbers of patients are recommended to fully determine the role of rituximab as single agent or in combination with chemotherapy in this disease.


View this table:
[in this window]
[in a new window]
 
Table 6. Clinical studies using rituximab in patients with mantle cell lymphoma
 
Rituximab in CLL

Several trials have been conducted to determine the efficacy of rituximab in CLL patients using standard doses. However, results were disappointing with only a limited number of short-lived PRs (11% to 25% of cases) [60, 61, 68, 69]. The ORR in the pivotal trial was 13% for patients with small lymphocytic lymphoma (SLL), contrasting with 60% for those with follicular lymphoma [9]. This might be due at least in part to the lower density of CD20 on CLL/SLL cells as compared with follicular lymphoma. Other reasons include the high number of B-cells and circulating CD20 [70]. In an attempt to improve on these results, a thrice-weekly dosing schedule was evaluated reporting higher response rates (CR 4%, PR 48%) [51].

An alternative strategy might be to increase the dose administered. Previously treated CLL patients received escalating doses of rituximab ranging from 500 up to 2250 mg/m2 per infusion [50]. The response rates were 22%, 43% and 75% (P = 0.03) when response was correlated with dose (500–825, 1000–1500 and 2250 mg/m2). All responses were PRs. Ninety-four per cent of the patients had side-effects including fever, chills and nausea with the first rituximab infusion, but severe toxicity (grade 3/4) was only seen in 12%. At the highest dose level a significant number of side-effects were observed without severe toxicity.

Different combination therapy trials have been conducted. Four cycles of rituximab, cyclophosphamide and decandron induced 36% CR and 41% PR in 22 evaluable patients [71]. In fludarabine and anthracycline-naïve patients, concurrent use of rituximab and fludarabine resulted in an ORR of 90%, with CR of 32% to 47% [72, 73] and a median TTP for the responders of 11 months [73]. A comparison between sequential administration and simultaneous treatment indiciated superior results in those patients who received rituximab together with fludarabine [73]. Combination chemoimmunotherapy with fludarabine, cyclophosphamide and rituximab also achieved high responses in previously untreated (n = 79; ORR 95%, CR 66%) [74] as well as in pretreated patients (n = 102; ORR 72%, CR 23%) [75]. Upfront treatment with rituximab might lead to higher response rates [76], particularly in early stages [77].

Our group has performed a multicenter phase II trial in which four cycles of fludarabine were given together with four cycles of rituximab [72]. Of 31 eligible B-CLL patients enrolled, 20 were previously untreated and 11 relapsed. Side-effects such as fever, chills and exanthema were mild and mainly associated with the first rituximab infusion. There were a total of 32 infections in 16 patients, none of which was fatal. The overall response rate was 87% with no difference between pretreated and untreated patients.

Taken together, these data, as summarized in Table 7, indicate that rituximab has efficacy in CLL but might require combination with chemotherapy. Thus, further information including the optimal schedule and best combination partner has to be established. The German CLL Study group is currently preparing such a study in which a fludarabine–cyclophosphamide (FC) combination will be compared with FC plus rituximab in a prospectively randomized fashion.


View this table:
[in this window]
[in a new window]
 
Table 7. Clinical studies using rituximab in CLL patients
 
Multiple myeloma

CD20 is present on the malignant cells of 20% of patients with multiple myeloma (MM) [6]. In addition, CD20 is expressed on clonotypic B-cells, which may be relevant precursors in MM. Since CD20+ MM patients have a shorter survival compared with CD20– patients [78], the expression of this antigen might be associated with a more aggressive phenotype. A phase II clinical trial with single-agent rituximab has been reported [79]. Although the response rates were low (1/19 PR, 5/19 SD), five of six responders had CD20+ bone marrow plasma cells upon study entry. Median time to treatment failure was 5.5 months. In another trial, rituximab was used in combination with a melphalan/prednisone regimen in newly diagnosed MM patients [80]. Rituximab seemed to improve the ORR, but the impact on PFS is yet to be determined.

The combination of rituximab and IFN-{gamma} might be particularly attractive in MM, since IFN-{gamma} is a potent inducer of CD20 on plasma cell lines and clinical studies using this combination in MM are currently underway.

Waldenström’s macroglobulinemia

CD20 is expressed on malignant lymphoplasmacytic cells in most patients with Waldenström’s macroglobulinemia (WM). Several retrospective analyses have indicated activity of rituximab in these patients with high response rates even in refractory cases [81, 82]. Interestingly, disease-associated polyneuropathy improved after rituximab treatment [83]. In a recent report, mean IgM levels for all 30 patients were reduced from 2.4 to 1.5 mg/dl after single-agent rituximab, with 87% of the patients showing a decline of IgM levels of >25% [84]. Moreover, median bone marrow involvement was reduced from 60% to 15%. In addition, 63% of the patients had an increase in their hematocrit and platelet counts. Prospective studies are currently ongoing that seem to confirm the activity of rituximab in Waldenström’s disease [85].

Other B-cell malignancies

Several attempts have been made to evaluate rituximab in patients with primary cutaneous B-cell lymphomas (pCBCL), either intravenously or intralesionally [86, 87]. Therapy with rituximab appears to be effective, in particular for patients with primary cutaneous large B-cell lymphomas of the leg, who have a poorer prognosis using conventional therapies than patients with other subtypes of pCBCL. There are some reports on rituximab in other B-cell malignancies such as B-acute lymphoblastic leukemia (B-ALL), Burkitt’s lymphoma, AIDS-related lymphoma and primary CNS lymphoma. Responses have been documented, but more studies are warranted to determine the impact of rituximab in these disorders.

Post-transplant lymphoproliferative disorder

Rituximab was investigated in the treatment of post-transplant lymphoproliferative disorder (PTLD), which is mostly composed of CD20+ B-cells. The ORR ranged from 62% to 75% in solid organ recipients [8890]. ORR of 92% (CR 46%) was reached in combination with 2-chlorodeoxyadenosine and granulocyte–macrophage colony-stimulating factor [91]. Rituximab also appears to have an impact on the Epstein–Barr virus (EBV) infection that underlies PTLD after hematopoietic stem cell transplantation [92]. Pre-emptive therapy with the antibody appears to prevent EBV-associated PTLD [93]. Longer follow-up is required to assess the durability of the responses.

Hodgkin’s disease

The CD20 antigen is expressed on roughly 20% of Hodgkin–Reed–Sternberg (HRS) cells in classical Hodgkin’s disease (HD) [94]. In contrast, the malignant cell population in lymphocyte predominant HD (LPHD) express the CD20 antigen in high density (Figure 4).



View larger version (155K):
[in this window]
[in a new window]
 
Figure 4. Lymphocyte predominant Hodgkin’s disease (LPHD): expression of CD20 in Hodgkin-Reed–Sternberg (HRS) cells [72].

 
Rehwald et al. [95] have treated 14 patients with relapsed LPHD or other CD20+ classical HD. The ORR was 86% with 8/14 CRs (57%) and 4/14 PRs (29%), with 10/12 responders in continuous remission at a median follow-up of 12 months. The median DR has not been reached at 20+ months. Encouraging results were also reported from another phase II study including only patients with LPHD [96], in which six of nine evaluable patients (67%) achieved a CR and three a PR (33%).

Based on the hypothesis that normal B-lymphocytes in patients with HD might promote HRS cell survival, Younes et al. [97] treated 24 patients with relapsed HD irrespective of CD20 expression on their HRS cells in order to deprive HRS cells from important growth signals. The patients received rituximab once a week for six doses. In the evaluable 22 patients the ORR was 23%. CD20 was expressed on HRS cells only in two cases of the responding patients.

Longer follow-up as well as larger number of patients are needed for a final judgement on rituximab in CD20+ HD. Possible new studies to be conducted include a combination of radiotherapy and rituximab in the early stages of LPHD, as well as chemotherapy and rituximab in the advanced stages.

Rituximab in autoimmune diseases

Autoimmune disorders are mediated at least in part by B-cells. Elimination of autoreactive B-cell clones is the rationale for the use of rituximab in these diseases. Currently, most information is available on the treatment of idiopathic thrombocytopenic purpura (ITP). A dose-escalation trial was reported in ITP patients with platelet counts of <75 000/µl who failed corticosteroid therapy [98]. Twenty-five per cent of the 20 patients who received four weekly doses of rituximab 375 mg/m2 showed objective clinical responses. Other studies involving a total of 47 patients were conducted in cases resistant to standard therapy including splenectomy [99101]. The attained ORRs ranged from 40% to 75%, and sustained responses for more than 6 months were reported. In responders, the rise in platelet count was usually observed 1 week after the first infusion of rituximab. Thus, mechanisms other than the reduction of circulating antiplatelet antibodies might explain the effect of rituximab in this disease. In fact, median serum IgG, IgM and IgA levels remained within normal limits throughout the study [101]. One might speculate that opsonized B-cells can inhibit macrophage Fc receptor function and clearance of IgG-coated platelets. The suppression of autoreactive B-cell clones might account for the sustained remissions observed in some patients.

Interest in the treatment of autoimmune hemolytic anemia (AIHA) with rituximab has grown after initial encouraging case reports. A small prospective study was recently reported [102]: five patients with chronic cold agglutinin disease were treated with a standard dose of rituximab with four of five patients responding (one CR, three PRs). Two further trials also documented high response rates with CRs between 83% and 100%, and DRs ranging from 4 months to 2.7 years [103, 104]. Eight of eight CLL patients with AIHA achieved a remission after treatment with a rituximab/cyclophosphamide/dexamethasone combination [105].

Others have applied rituximab in the prevention of acute graft-versus-host disease (aGVHD). B-lymphocytes may act as antigen-presenting cells capable of triggering T-cell activation. Though the clinical relevance of the elemination of B-cells in this context remains to be more precisely defined, the incidence of severe aGVHD in patients with NHL after allogeneic stem cell transplantation was lower in those who had previously received rituximab (18% versus 51%) [106].

Additional autoimmune diseases in which rituximab is currently being evaluated include IgM polyneuropathy, dermatomyositis, myasthenia gravis, thrombotic thrombocytopenic purpura, acquired factor VIII deficiency, rheumatoid arthritis, pemphigus vulgaris and systemic lupus erythematosus.

Toxicity

Rituximab is generally well tolerated, in patients with both malignant and non-malignant disease, including children and pregnant women [104, 107]. Severe adverse events develop only in a small number of patients. The most common adverse events are infusion-related and occur most frequently during or shortly after the first infusion. This syndrome consists of chills, fever, headache, rhinitis, pruritus, vasodilation, asthenia and angioedema. Less often reported are hypotension, rash, bronchospasm, rash and pain at tumor sites. About 95% of these adverse reactions are mild or moderate and resolve completely after temporary interruption of the infusion. Symptomatic treatment with antipyretics, antihistamines, and, if necessary, steroids readily controls severe unwanted reactions in most cases.

Importantly, the increasing use of rituximab in entities other than follicular NHL has revealed no other side-effects than those previously described. Infusion-related side-effects are mediated by inflammatory cytokines such as TNF-{alpha}, interleukin (IL)-8 and IFN-{gamma} [51]. This cytokine-release syndrome is more frequently observed in patients with higher numbers (>50 x 109/l) of tumor cells in their peripheral blood [68]. Winkler et al. [68] found a correlation of clinical symptoms and increased serum levels of TNF-{alpha} and IL-6 90 min after the first application of rituximab (Figure 5A and B). Postmarketing surveillance database includes reports of very few cases with fatal outcome who were related to severe forms of the cytokine-release syndrome in patients with high peripheral tumor load and other comorbidities. In most fatal cases, patients had prior pulmonary or cardiovascular disease, pulmonary infiltrates or had been treated with cardiotoxic drugs. Thus, patients with a high number of circulating cells should only be treated with fractionated doses of rituximab initially, and should be closely monitored. In addition, only patients with <50 x 109/l cell count peripherally should be treated. When the infusion of the antibody has to be interrupted due to adverse reactions, complete resolution of clinical symptoms has to be awaited before restarting the application.



View larger version (19K):
[in this window]
[in a new window]
 
Figure 5. (A) Interleukin (IL)-6 levels in chronic lymphocytic leukemia patients treated with rituximab. (B) TNF-{alpha} levels in chronic lymphocytic leukemia patients treated with rituximab. Blood samples were taken 90 min after the first rituximab application.

 
Rituximab induces a rapid depletion of CD20+ B-cells in the peripheral blood. B-cells remain at low levels for at least 2– 6 months with recovery to pretreatment values within 12 months [47]. Other hematological toxicity is generally mild and rare. About 10% of patients experience temporary reduction of platelets or neutrophils, and occasionally reduced immunoglobulin levels. Some case reports showed reactivation of hepatitis B following rituximab administration [108]. In contrast, a recently published Japanese study suggests that the risk for a reactivation might be lower than expected [109]. Most importantly, the incidence of other infections does not seem to be increased in patients treated with rituximab alone. This observation has been confirmed in the few available prospectively randomized studies. Combination with chemotherapy was also not associated with more toxicity than expected, although a higher rate of neutropenia has been described [26].

Human anti-chimeric antibodies (HACA) were rarely observed with no impact on toxicity and on clinical outcome [9, 110]. However, the detection of HACAs is difficult and has been neglected in most studies. Thus, further studies should aim at a more comprehensive investigation of auto-antibody development.

Single serious late effects have been documented, occurring weeks to months after treatment with rituximab, including arthralgia, vasculitis, serum sickness, acute agranulocytosis, uveitis and bullous cutaneous reaction possibly related to other yet to be clarified immune phenomena [111, 112].

Conclusions and prospects

Since rituximab has been widely documented as effective treatment associated with few serious side-effects, most patients with indolent lymphoma receive this chimeric monoclonal antibody during the course of their disease. In the USA and in Europe rituximab was also approved for patients with DLCL when combined with standard chemotherapy (CHOP). Other entities currently under investigation include CLL, MCL, plasmocytoma, HD and autoimmune diseases. Although the use of rituximab in most of these entities has become standard praxis particularly in the US, carefully designed randomized studies are warranted to further define the optimal treatment strategies with this new exciting component.

Footnotes

+ Correspondence to: Professor A. Engert, Department I of Internal Medicine, University Hospital of Cologne, Joseph-Stelzmann-Strasse 9, Cologne 50924, Germany. Tel: +49-221-478-5933; Fax: +49-221-478-3778; E-mail: a.engert{at}uni-koeln.de Back

References

1. Köhler G, Milstein C. Continuous cultures of fused cells secreting antibody of pre-defined specificity. Nature 1975; 256: 495–497.[ISI][Medline]

2. Reff ME, Carner K, Chambers KS et al. Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20. Blood 1994; 83: 435–445.[Abstract/Free Full Text]

3. Press OW, Appelbaum F, Ledbetter JA et al. Monoclonal antibody 1F5 (anti-CD20) serotherapy of human B cell lymphomas. Blood 1987; 69: 584–591.[Abstract]

4. LoBuglio AF, Wheeler RH, Trang J et al. Mouse/human chimeric monoclonal antibody in man: kinetics and immune response. Proc Natl Acad Sci USA 1989; 86: 4220–4224.[Abstract]

5. Stashenko P, Nadler LM, Hardy R, Schlossman SF. Characterization of a human B lymphocyte-specific antigen. J Immunol 1980; 125: 1678–1685.[Abstract/Free Full Text]

6. Srinivas S, Yook C, Chang V et al. Prevalence of bone marrow CD20 positivity in patients (pts) with multiple myeloma (MM). J Clin Oncol 2001; 20: (Abstr 2687).

7. Anderson DR, Grillo-Lopez A, Varns C et al. Targeted anti-cancer therapy using rituximab, a chimeric CD20 antibody (IDEC-C2B8) in the treatment of non-Hodgkin’s B-cell lymphoma. Biochem Soc Trans 1997; 25: 705–708.[ISI][Medline]

8. Tedder TF, Engel P. CD20. A regulator of cell-cycle progression of B lymphocytes. Immunol Today 1994; 15: 450–454.[CrossRef][ISI][Medline]

9. McLaughlin P, Grillo-Lopez AJ, Link BK et al. Rituximab chimeric anti-CD20 monoclonal antibody therapy for relapsed indolent lymphoma: half of patients respond to a four-dose treatment program. J Clin Oncol 1998; 16: 2825–2833.[Abstract]

10. Grillo-Lopez AJ, Cheson BD, Horning SJ et al. Response criteria for NHL: impotance of ‘normal’ lymph node size and correlations with response rates. Ann Oncol 2000; 11: 399–408.[Abstract]

11. Velasquez WS, Jagannath S, Tucker SL et al. Risk classification as the basis for clinical staging of diffuse large-cell lymphoma derived from 10-year survival data. Blood 1989; 74: 551–557.[Abstract]

12. Davis TA, White CA, Grillo-Lopez AJ et al. Single-agent monoclonal antibody efficacy in bulky non-Hodgkin’s lymphoma: results of a phase II trial of rituximab. J Clin Oncol 1999; 17: 1851–1857.[Abstract/Free Full Text]

13. Colombat P, Salles G, Brousse N et al. Rituximab (anti-CD20 monoclonal antibody) as single first-line therapy for patients with follicular lymphoma with a low tumor burden: clinical and molecular evaluation. Blood 2001; 97: 101–106.[Abstract/Free Full Text]

14. Hainsworth JD. Rituximab as first-line and maintenance therapy for patients with indolent non-Hodgkin’s lymphoma: interim follow-up of a multicenter phase II trial. Semin Oncol 2002; 29 (1 Suppl 2): 25–29.

15. Davis TA, Grillo-Lopez AJ, White CA et al. Rituximab anti-CD20 monoclonal antibody therapy in non-Hodgkin’s lymphoma: safety and efficacy of re-treatment. J Clin Oncol 2000; 18: 3135–3143.[Abstract/Free Full Text]

16. Igarashi T, Ohtsu T, Fujii H et al. Re-treatment of relapsed indolent B-cell lymphoma with rituximab. Int J Hematol 2001; 73: 213–221.[ISI][Medline]

17. Davis TA, Czerwinski DK, Levy R. Therapy of B-cell lymphoma with anti-CD20 antibodies can result in the loss of CD20 antigen expression. Clin Cancer Res 2000; 6: 317–318.[Free Full Text]

18. Demidem A, Lam T, Alas S et al. Chimeric anti-CD 20 antibody sensitizes a B-cell lymphoma cell line to cell killing by cytotoxic drugs. Cancer Biother Radiopharm 1997; 12: 177–186.[ISI][Medline]

19. Di Gaetano N, Xiao Y, Erba E et al. Synergism between fludarabine and rituximab revealed in a follicular lymphoma cell line resistant to the cytotoxic activity of either drug alone. Br J Haematol 2001; 114: 800–809.[CrossRef][ISI][Medline]

20. Alas S, Bonavida B, Emmanouilides C. Potentiation of fludarabine cytotoxicity on non-Hodgkin’s lymphoma by pentoxifylline and rituximab. Anticancer Res 2000; 20: 2961–2966.[ISI][Medline]

21. Czuczman MS, Fallon A, Mohr A et al. Phase II study of rituximab plus fludarabine in patients (pts.) with low-grade lymphoma. Blood 2001; 98 (Suppl 1): 601 (Abstr 2518A).[CrossRef]

22. Czuczman MS, Grillo-Lopez AJ, White CA et al. Treatment of patients with low-grade B-cell lymphoma with the combination of chimeric anti-CD20 monoclonal antibody and CHOP chemotherapy. J Clin Oncol 1999; 17: 268–276.[Abstract/Free Full Text]

23. Freedman AS, Gribben JG, Neuberg D et al. High dose therapy and autologous bone marrow transplantation in patients with follicular lymphoma during first remission. Blood 1996; 88: 2780–2786.[Abstract/Free Full Text]

24. Czuczman M, Grillo-Lopez AJ, White CA et al. Progression free survival (PFS) after six years (median) follow-up of the first clinical trial of rituximab/CHOP chemoimmunotherapy. Blood 2001; 98 (Suppl 1): 601a (Abstr 2519A).[CrossRef]

25. Rambaldi A, Carlotti E, Baccarani M et al. Monitoring of minimal residual disease after CHOP and rituximab in previously untreated follicular lymphoma patients. Blood 2001; 98 (Suppl 1): 603a (Abstr 2528A).

26. McLaughlin P, Hagemeister FB, Rodriguez MA et al. Safety of fludarabine, mitoxantrone, and dexamethasone combined with rituximab in the treatment of stage IV indolent lymphoma. Semin Oncol 2000; 27 (Suppl 12): 37–41.

27. Vitolo U, Boccomini C, Astolfi M et al. Chemoimmunotherapy with fludarabine + mitoxantrone + dexamethasone (FND) and rituximab in indolent non-Hodgkin’s lymphoma (NHL): a pilot study to evaluate feasibility, safety, clinical and molecular response. Blood 2001; 98 (Suppl 1): 252 (Abstr 4739A).

28. Hiddemann W, Forstpointner R, Fiedler F et al. Combined immunotherapy (R-FCM) is superior to a fludarabine-containing chemotherapy (FCM) alone in recurrent indolent lymphoma – results of a prospective randomized comparison of the German Low Grade Lymphoma Study Group. Onkologie 2001; 24: 90A.

29. Patel D, Gupta NK, Mehrotra B et al. Rituximab, cyclophosphamide and decadron (RCD) combination is an effective salvage regimen for previously treated low grade lymphoma. J Clin Oncol 2001; 20: (Abstr 2665).

30. Gregory SA, Venugopal P, Adler SS et al. Safety and efficacy of fludarabine and mitoxantrone with rituximab consolidation in untreated advanced low grade non-Hodgkin’s lymphoma (LG-NHL). Blood 2001; 98 (Suppl 1): 605a (Abstr 2534A).

31. Weide R, Heymanns J, Gores A, Köppler H. Bendamustine, mitoxantrone and rituximab (BMR): a new effective regimen for refractory or relapsed indolent lymphoma. Leuk Lymphoma 2002; 43: 327–331.[CrossRef][ISI][Medline]

32. Kirchner HH, Gaede B, Steinhauer EU et al. Chemoimmunotherapy with fludarabine, bendamustine and rituximab for relapsed low grade malignant non-Hodgkin’s lymphoma. Blood 2001; 98 (Suppl 1): 135a (Abstr 568A).

33. Herold M, Fiedler F, Pasold R et al. Efficacy and toxicity of rituximab plus mitoxantrone, chlorambucil, prednisolone (MCP) versus MCP alone in advanced indolent NHL – interim results of a clinical phase III study of the East German Study Group Hematology/Oncology (OSHO). Blood 2001; 98 (Suppl 1): 601 (Abstr 2521A).[CrossRef]

34. Basham TY, Race ER, Campbell MJ et al. Synergistic antitumor activity with IFN and monoclonal anti-idiotype antibody for murine B cell lymphoma. Mechanism of action. J Immunol 1988; 141: 2855–2860.[Abstract/Free Full Text]

35. Hari P, Venugopal P, Sivaraman S et al. Analysis of time sequence of CD20 antigen expression changes on tumor cells following exposure to cytokines. Blood 2001; 98 (Suppl 1): 228b (Abstr 4634A).

36. Guadagni F, Schlom J, Pothen S et al. Parameters involved in the enhancement of monoclonal antibody targeting in vivo with recombination interferon. Cancer Immunol Immunther 1998; 26: 222–230.

37. Yokota S, Hara H, Luo Y, Seon BK. Synergistic potentiation of in vivo antitumor activity of anti-human T-leukemia immunotoxins by recombinant {alpha}-interferon and daunorubicin. Cancer Res 1990; 50: 32–37.[Abstract]

38. Davis TA, Maloney DG, Grillo-Lopez AJ et al. Combination immunotherapy of relapsed or refractory low-grade or follicular non-Hodgkin’s lymphoma with rituximab and interferon-{alpha}-2a. Clin Cancer Res 2000; 6: 2644–2652.[Abstract/Free Full Text]

39. Sacchi S, Frederico M, Vitolo U et al. Clinical activity and safety of combination immunotherapy with interferon-{alpha}2a and rituximab in patients with relapsed low-grade non-Hodgkin’s lymphoma. Haematologica 2001; 86: 951–958.[ISI][Medline]

40. Kimby E, Geisler C, Hagberg H et al. Rituximab (Mabthera) as single agent and in combination with interferon-{alpha}-2a as treatment of untreated and first relapse follicular or other low-grade lymphomas. A randomized phase II study (M39035). Blood 2000; 96 (Suppl 1): 577a (Abstr 2479A).

41. Magni M, Di Nicola M, Devizzi L et al. Successful in vivo purging of CD34-containing peripheral blood harvests in mantle cell and indolent lymphoma: evidence for a role of both chemotherapy and rituximab infusion. Blood 2000; 96: 864–869.[Abstract/Free Full Text]

42. Flinn IW, Jones RJ, Goodrich A et al. Rituximab during autologous stem cell transplantation for lymphoma produces lymphoma free grafts in most patients by PCR and clonogenic assays. Blood 2001; 98 (Suppl 1): 676a (Abstr 2832A).

43. Buckstein RJ, Imrie KR, Spaner D et al. Autologous stem cell transplants combined with rituximab for relapsed follicular lymphoma achieve prolonged clinical and molecular remissions. Blood 2001; 98 (Suppl 1): 680a (Abstr 2846A.

44. Voso MT, Pantel G, Weis M et al. In vivo depletion of B cells using a combination of high-dose cytosine arabinoside/mitoxantrone and rituximab for autografting in patients with non-Hodgkin’s lymphoma. Br J Haematol 2000; 109: 729–735.[CrossRef][ISI][Medline]

45. Brugger W. Improving outcomes in transplantation. Semin Oncol 2002; 29 (2 Suppl 6): 23–26.

46. Maloney DG, Grillo-Lopez AJ, Bodkin DJ et al. IDEC-C2B8: results of a phase I multi-dose trial in patients with relapsed non-Hodgkin’s lymphoma. J Clin Oncol 1997; 15: 3266–3274.[Abstract]

47. Maloney DG, Grillo-Lopez AJ, White CA et al. IDEC-C2B8 (Rituximab) anti-CD20 monoclonal antibody therapy in patients with relapsed low-grade non-Hodgkin’s lymphoma. Blood 1997; 90: 2188–2195.[Abstract/Free Full Text]

48. Ghielmini M, Schmitz SF, Burki K et al. The effect of Rituximab on patients with follicular and mantle-cell lymphoma. Ann Oncol 2000; 11 (Suppl 1): 123–126.[CrossRef]

49. Feuring-Buske M, Kneba M, Unterhalt M et al. IDEC-C2B8 (Rituximab) anti-CD20 antibody treatment in relapsed advanced-stage follicular lymphomas: results of a phase-II study of the German Low-Grade Lymphoma Study Group. Ann Hematol 2000; 79: 493–500.[CrossRef][ISI][Medline]

50. O’Brien SM, Kantarjian H, Thomas DA et al. Rituximab dose-escalation trial in chronic lymphocytic leukemia. J Clin Oncol 2001; 19: 2165–2170.[Abstract/Free Full Text]

51. Byrd JC, Murphy T, Howard RS et al. Rituximab using a thrice weekly dosing schedule in B-cell chronic lymphocytic leukemia and small lymphocytic lymphoma demonstrates clinical activity and acceptable toxicity. J Clin Oncol 2001; 19: 2153–2164.[Abstract/Free Full Text]

52. Piro LT, White CA, Grillo-Lopez AJ et al. Extended rituximab (anti-CD20 monoclonal antibody) therapy for relapsed or refractory low-grade or follicular non-Hodgkin’s lymphoma. Ann Oncol 1999; 10: 655–661.[Abstract]

53. Vose JM, Link BK, Grossbard ML et al. Phase II study of rituximab in combination with CHOP chemotherapy in patients with previously untreated, aggressive non-Hodgkin’s lymphoma. J Clin Oncol 2001; 19: 389–397.[Abstract/Free Full Text]

54. Coiffier B, Lepage E, Briere PD et al. CHOP chemotherapy plus rituximab compared with CHOP alone in elderly patients with diffuse large B-cell lymphoma. N Engl J Med 2002; 346: 235–242.[Abstract/Free Full Text]

55. Coiffier B, Haioun C, Ketterer N et al. Rituximab (anti-CD20 monoclonal antibody ) for the treatment of patients with relapsing or refractory aggressive lymphoma: A multicenter phase II study. Blood 1998; 92: 1927–1932.[Abstract/Free Full Text]

56. Kewalramani T, Zelenetz A, Bertino J et al. Rituximab significantly increases the complete response rate in patients with relapsed or primary refractory DLBCL receiving ICE as second-line therapy (SLT). Blood 2001; 98 (Suppl 1): 346a (Abstr 1459A).[CrossRef]

57. Horwitz SM, Negrin RS, Stockerl-Goldstein KE et al. Phase II trial of rituximab as adjuvant therapy to high dose chemotherapy and peripheral blood stem cell transplantation for relapsed and refractory aggressive non-Hodgkin’s lymphomas. Blood 2001; 98 (Suppl 1): 862a (Abstr 3578A).

58. Wilson WH, Gutierrez M, O’Connor P et al. The role of rituximab and chemotherapy in aggressive B-cell lymphoma: a preliminary report of dose-adjusted EPOCH-R. Semin Oncol 2002; 29 (1 Suppl 2): 41–47.

59. Tsai DE, Moore HCF, Hardy CL et al. Rituximab (anti-CD20 monoclonal antibody) therapy for progressive intermediate-grade non-Hodgkin’s lymphoma after high-dose therapy and autologous peripheral stem cell transplantation. Bone Marrow Transplant 1999; 24: 521–526.[CrossRef][ISI][Medline]

60. Foran JM, Rohatiner AZS, Cunningham D et al. European phase II study of rituximab (chimeric anti-CD20 monoclonal antibody) for patients with newly diagnosed mantle-cell lymphoma and previously treated mantle-cell lymphoma, immunocytoma, and small B-cell lymphocytic lymphoma. J Clin Oncol 2000; 18: 317–324.[Abstract/Free Full Text]

61. Nguyen DT, Amess JA, Doughty H et al. IDEC-C2B8 anti-CD20 (rituximab) immunotherapy in patients with low-grade non-Hodgkin’s lymphoma and lymphoproliferative disorders: evaluation of response on 48 patients. Eur J Haematol 1999; 62: 76–82.[ISI][Medline]

62. Howard OM, Gribben JG, Neuberg DS et al. Rituximab and CHOP induction therapy for newly diagnosed mantle-cell lymphoma: molecular complete responses are not predictive of progression-free survival. J Clin Oncol 2002; 20: 1288–1294.[Abstract/Free Full Text]

63. Mangel J, Buckstein R, Imrie K et al. Immunotherapy with rituximab following high-dose therapy and autologous stem-cell transplantation for mantle cell lymphoma. Semin Oncol 2002; 29 (1 Suppl 2): 56–69.[CrossRef][ISI][Medline]

64. Seyfarth B, Sonnen R, Zeis M et al. Mantle cell lymphoma: promising results with upfront stem cell transplantation using the rituximab/TBI/CY high-dose regimen. Blood 2001; 98 (Suppl 1): 679a (Abstr 2841A).

65. Corradini P, Astolfi M, Cherasco C et al. Molecular monitoring of minimal residual disease in follicular and mantle cell non-Hodgkin’s lymphomas treated with high-dose chemotherapy and peripheral blood progenitor cell autografting. Blood 1997; 89: 724–731.[Abstract/Free Full Text]

66. Andersen NS, Donovan JW, Borus JS et al. Failure of immunologic purging in in mantle cell lymphoma assessed by polymerase chain reaction detection of minimal residual disease. Blood 1997; 90: 4212–4221.[Abstract/Free Full Text]

67. Romaguera J, Cabanillas F, Dang NH et al. Mantle cell lymphoma (MCL) – high rates of complete remission (CR) and prolonged failure-free survival (FFS) with Rituxan-HyperCVAD (R-HCVAD) without stem cell transplant (SCT). Blood 2001; 98 (Suppl 1): 726a (Abstr 3030A).

68. Winkler U, Jensen M, Manzke O et al. Cytokine-release syndrome in patients with B-cell chronic lymphocytic leukemia and high lymphocyte counts after treatment with an anti-CD20 monoclonal antibody (rituximab, IDEC C2B8). Blood 1999; 94: 2217–2224.[Abstract/Free Full Text]

69. Huhn D, von Schilling C, Wilhelm M et al. Rituximab therapy of patients with B-cell chronic lymphatic leukemia. Blood 2001; 98: 1326–1331.[Abstract/Free Full Text]

70. Manshouri T, Saffer H, Keating M, Albitar M. Clinical relevance of circulating CD20 (cCD20) in patients with chronic lymphocytic leukemia (CLL). Blood 2000; 96 (Suppl 1): 369a (Abstr 1595A).

71. Gupta NK, Patel D, Kavuru S et al. Rituximab, cyclophosphamide and decadron (RCD) is effective in previously treated advanced chronic lymphocytic leukemia (CLL). J Clin Oncol 2001; 20: (Abstr 1133).

72. Schulz H, Klein SK, Rehwald U et al. Phase II study of combined immunotherapy using rituximab and fludarabine in patients with chronic lymphocytic leukemia. Blood 2001; 100: 3115–3120.[CrossRef][ISI]

73. Byrd JC, Peterson BL, Park K et al. Concurrent rituximab and fludarabine has a higher complete response rate than sequential treatment in untreated chronic lymphocytic leukemia (CLL) patients: results from CALGB 9712. Blood 2001; 98 (Suppl 1): 772a (Abstr 3212A).

74. Wierda W, O’Brien S, Albitar M et al. Combined fludarabine, cyclophosphamide, and rituximab achieves a high complete remission rate as initial treatment for chronic lymphocytic leukemia. Blood 2001; 98 (Suppl 1): 771a (Abstr 3210A).[CrossRef]

75. Manero GG, O’Brien S, Cortes J et al. Update of results of the combination of fludarabine, cyclophosphamide and rituximab for previously treated patients with chronic lymphocytic leukemia (CLL). Blood 2001; 98 (Suppl 1): 633a (Abstr 2650A).

76. Hainsworth JD, Litchy S, Burris HA, Greco A. Rituximab as first-line and maintenance therapy for patients with small lymphocytic lymphoma (SLL) and chronic lymphocytic leukemia (CLL). Blood 2001; 98 (Suppl 1): 363a (Abstr 1530A).

77. Thomas DA, O’Brien S, Giles FJ et al. Single agent rituxan in early stage chronic lymphocytic leukemia (CLL). Blood 2001; 98 (Suppl 1): 364a (Abstr 1533A).

78. San Miguel JF, Gonzalez M, Gascon A et al. Immunophenotypic heterogeneity of multiple myeloma: influence on the biology and clinical course of the disease. Castellano-Leones (Spain) Cooperative Group for the Study of Monoclonal Gammopathies. Br J Haematol 1991; 77: 185–190.[ISI][Medline]

79. Treon SP, Pilarski LM, Belch AR et al. CD20-directed serotherapy in patients with multiple myeloma: biologic considerations and therapeutic applications. J Immunother 2002; 25: 72–81.[CrossRef][ISI][Medline]

80. Hsi E, Hussein MA, Elson P et al. Biologic and clinical evaluation of rituxan (RT) in the management of newly diagnosed multiple myeloma (MM) patients (pts): an update. J Clin Oncol 2001; 20: 1193A.

81. Byrd JC, White CA, Link B et al. Rituximab therapy in Waldenstrom’s macroglobulinemia: preliminary evidence of clinical activity. Ann Oncol 1999; 10: 1525–1527.[Abstract]

82. Weber DM, Gavino M, Huh Y et al. Phenotypic and clinical evidence supports rituximab for Waldenström’s macroglobulinemia. Blood 1999; 94 (Suppl 1): 125a (Abstr 551A).[ISI]

83. Weide R, Heymanns J, Köppler H. The polyneuropathy associated with Waldenström’s macroglobulinaemia can be treated effectively with chemotherapy and the anti-CD20 monoclonal antibody rituximab. Br J Haematol 2000; 109: 838–841.[CrossRef][ISI][Medline]

84. Treon SP, Agus DB, Link B et al. CD20-directed antibody-mediated immunotherapy induces responses and facilitates hematologic recovery in patients with Waldenstrom’s macrcoglobulinemia. J Immunother 2001; 24: 272–279.[CrossRef][ISI]

85. Dimopoulos MA, Zervas C, Zomas A et al. Treatment of Waldenstrom’s macroglobulinemia with rituximab. J Clin Oncol 2002; 20: 2327–2333.[Abstract/Free Full Text]

86. Heinzerling L, Dummer R, Kempf W et al. Intralesional therapy with anti-CD20 monoclonal antibody rituximab in primary cutaneous B-cell lymphoma. Arch Dermatol 2000; 136: 374–378.[Abstract/Free Full Text]

87. Heinzerling LM, Urbanek M, Funk JO et al. Reduction of tumor burden and stabilization of disease by systemic therapy with anti-CD20 antibody (rituximab) in patients with primary cutaneous B-cell lymphoma. Cancer 2000; 89: 1835–1844.[CrossRef][ISI][Medline]

88. Horwitz SM, Tsai D, Twist C et al. Rituximab is effective therapy for post-transplant lymphoproliferative disorder (PTLD) not responding to reduction in immunosuppression: a prospective trial in adults and children. J Clin Oncol 2001; 20: 1134A.

89. Kentos A, Knoop C, Wissing M et al. Anti-CD20 monoclonal antibody as first-line treatment of post-transplant B-lymphoproliferative disorders in solid organ transplant recipients. A report of 8 cases observed in a single center. Blood 2001; 98 (Suppl 1): 344a (Abstr 1451A).

90. Morrison VA, Bartlett N, Dunn DL, Peterson BA. Rituximab therapy for post-transplant lymphoproliferative disorders (PTLD): preliminary outcome results. J Clin Oncol 2001; 20: 1177A.

91. Shah PK, Ifthikharuddin J, Mintz M et al. 2-Chlorodeoxyadenosine (2-CDA) with weekly rituximab and granulocyte–macrophage colony stimulating factor (GM-CSF): a highly effective regimen for advanced B-cell lymphoproliferative disorders (BLPD). Blood 2001; 98 (Suppl 1): 249b (Abstr 4726A).

92. Kuehnle I, Huls MH, Liu Z et al. CD20 monoclonal antibody (rituximab) for therapy of Epstein–Barr virus lymphoma after hemopoietic stem-cell transplantation. Blood 2000; 95: 1502–1505.[Abstract/Free Full Text]

93. Gruhn B, Meerbach A, Häfer R et al. Early diagnosis and pre-emptive therapy Epstein–Barr virus-associated lymphoproliferative disease following hematopoietic stem cell transplantation. Blood 2001; 98 (Suppl 1): 393a (Abstr 1655A).[CrossRef]

94. Rassidakis GZ, Medeiros LJ, Viviani S et al. CD 20 expression on Hodgkin and Reed–Sternberg cells of classical Hodgkin’s disease: associations with presenting features and clinical outcome. J Clin Oncol 2002; 20: 1278–1287.[Abstract/Free Full Text]

95. Rehwald U, Engert A, Diehl V. Monoclonal anti-CD20 antibody Rituximab (Rituxan) for treatment of CD20-positive Hodgkin’s lymphoma: The German experience. Blood 2000; 96 (Suppl 1): 729a (Abstr 3153A).

96. Lucas JB, Hoppe RT, Horwitz RM et al. Rituximab is active in lymphocyte predominant Hodgkin’s disease. Blood 2000; 96 (Suppl 1): 831a (Abstr 3592A).[ISI]

97. Younes A, Romaguera J, Hagemeister F et al. Depletion of normal B-lymphocytes by rituximab therapy alters serum cytokine levels, resolves B-symptoms and induces clinical remissions in patients with relapsed classical Hodgkin’s disease (HD). Blood 2001; 98 (Suppl 1): 132a (Abstr 555A).

98. Saleh MN, Moore M, Feinberg B et al. A pilot study of anti-CD20 MoAb rituximab in patients with refractory immune thrombocytopenic purpura (ITP). Blood 2001; 98 (Suppl 1): 521a (Abstr 2179A).

99. Giagounidis AAN, Anhuf J, Schneider P et al. Treatment of relapsed idiopathic thrombocytopenic purpura with the anti-CD20 antibody rituximab. Blood 2001; 98 (Suppl 1): 523a (Abstr 2187A).[CrossRef]

100. Perotta A, Abuel C. Update of response to rituximab of chronic relapsing ITP. Blood 1999; 94 (Suppl 1): 82b (Abstr 3528).

101. Stasi R, Pagano A, Stipa E, Amadori S. Rituximab chimeric anti-CD20 monoclonal antibody treatment for adults with chronic idiopathic thrombocytopenic purpura. Blood 2001; 98: 952–957.[Abstract/Free Full Text]

102. Berentsen S, Tjonnfjord GE, Gjertsen BT et al. Rituxan (Rituximab) therapy for chronic cold agglutinin disease. Blood 2000; 96 (Suppl 1): 730 (Abstr 3156A).

103. Lee E, Zamkoff KW, Gentile TC, Zimrin A. Rituximab in the treatment of auto-immune hemolytic anemia (AIHA). Blood 2000; 96 (Suppl 1): 596a (Abstr 2560A).[ISI]

104. Quartier P, Brethon P, Philippet P et al. Treatment of childhood autoimmune haemolytic anaemia with rituximab. Lancet 2001; 358: 1511–1513.[CrossRef][ISI][Medline]

105. Gupta NK, Patel DV, Kavuru S et al. Re-treatment with a rituximab based therapy is highly effective in autoimmune hemolytic anemia (AIHA) associated with chronic lymphocytic leukemia (CLL). Blood 2001; 98 (Suppl 1): 363a (Abstr 1529A).

106. Ratanatharathorn V, Bociek RG, Pavletic SZ et al. Prior therapy with anti-CD20 chimeric antibody (Rituximab) may decrease the risk of acute graft-versus-host disease (GVHD) in patients with non-Hodgkin’s lymphoma receiving allogeneic stem cell transplantation. Blood 2000; 96 (Suppl 1): 391a (Abstr 1688).

107. Herold M, Schnohr S, Bittrich H. Efficacy and safety of a combined rituximab chemotherapy during pregnancy. J Clin Oncol 2001; 19: 3439.[Free Full Text]

108. Ng HJ, Lim LC. Fulminant hepatitis B virus reactivation with concomitant listeriosis after fludarabine and rituximab therapy: case report. Ann Hematol 2001; 80: 549–552.[CrossRef][ISI][Medline]

109. Hamaki T, Kami M, Kusumi E et al. A feasibility study of rituximab for patients with hepatitis B or C virus infection in the treatment of non-Hodgkin’s lymphoma. Blood 2001; 98 (Suppl 1): 242b (Abstr 4695A).[CrossRef]

110. Maeda T, Yamada Y, Tawara M et al. Successful treatment with a chimeric anti-CD20 monoclonal antibody (IDEC C2-B8, rituximab) for a patient with relapsed mantle cell lymphoma who developed a human anti-chimeric antibody. Int J Hematol 2001; 74: 70–75.[ISI][Medline]

111. Voog E, Brice P, Cartrin J et al. Acute agranulocytosis (AA) in three patients treated with rituximab for non-Hodgkin’s lymphoma (NHL). Blood 2001; 98 (Suppl 1): 236b (Abstr 4668A).

112. Rituximab 1999 package insert.