Rituximab Chimeric Anti-CD20 Monoclonal Antibody Therapy for Relapsed Indolent Lymphoma: Half of Patients Respond to a Four-Dose Treatment Program

PURPOSE

The CD20 antigen is expressed on more than 90% of B-cell lymphomas. It is appealing for targeted therapy, because it does not shed or modulate. A chimeric monoclonal antibody more effectively mediates host effector functions and is itself less immunogenic than are murine antibodies.

PATIENTS AND METHODS

This was a multiinstitutional trial of the chimeric anti-CD20 antibody, IDEC-C2B8. Patients with relapsed low grade or follicular lymphoma received an outpatient treatment course of IDEC-C2B8 375 mg/m2 intravenously weekly for four doses.

RESULTS

From 31 centers, 166 patients were entered. Of this intent-to-treat group, 48% responded. With a median follow-up duration of 11.8 months, the projected median time to progression for responders is 13.0 months. Serum antibody levels were sustained longer after the fourth infusion than after the first, and were higher in responders and in patients with lower tumor burden. The majority of adverse events occurred during the first infusion and were grade 1 or 2; fever and chills were the most common events. Only 12% of patients had grade 3 and 3% grade 4 toxicities. A human antichimeric antibody was detected in only one patient.

CONCLUSION

The response rate of 48% with IDEC-C2B8 is comparable to results with single-agent cytotoxic chemotherapy. Toxicity was mild. Attention needs to be paid to the rate of antibody infusion, with titration according to toxicity. Further investigation of this agent is warranted, including its use in conjunction with standard chemotherapy.

Prognostic factors for non-Hodgkin's lymphoma patients treated with chemotherapy may not predict outcome in patients treated with rituximab

Several factors predict outcome for patients with non-Hodgkin's lymphoma (NHL) after chemotherapy. However, predictors of response to rituximab have not been identified. Baseline characteristics for 166 NHL patients (130 follicular) in a phase III trial of rituximab were analysed by univariate and multivariate methods to determine whether any of 27 factors predict response and/or response duration. In a univariate analysis, response to rituximab was associated with follicular histology, no prior fludarabine therapy, prior autologous bone marrow transplantation (ABMT), lack of bone marrow involvement or extranodal disease, positive bcl-2 in blood, and fewer relapses. By univariate analysis, longer median time to progression (TTP) and/or duration of response (DR) after rituximab therapy was associated with International Prognostic Index lower-risk group, multiagent chemotherapy, and low/normal serum lactate dehydrogenase (LDH) or beta2 microglobulin. In the multivariate analysis, response to rituximab correlated with follicular histology, prior ABMT, multiagent chemotherapy, and no bone marrow involvement; longer TTP and/or DR correlated with low/normal serum LDH or beta2 microglobulin, high CD3+ cells, and response to last chemotherapy. The follicular lymphoma international prognostic index (FLIPI) did not correlate consistently with response to rituximab or response duration. Several factors associated with prognosis following chemotherapy did not correlate with response to rituximab or response duration. NHL patients can respond to rituximab despite having factors associated with a poor outcome to chemotherapy.

Treatment of relapsed B-cell non-Hodgkin's lymphoma with a combination of chimeric anti-CD20 monoclonal antibodies (rituximab) and G-CSF: final report on safety and efficacy

Antibody-dependent cellular cytotoxicity (ADCC) is one of the possible mechanisms of action of the chimeric CD20 monoclonal antibody IDEC-C2B8 (rituximab). As granulocyte-colony stimulating factor (G-CSF) greatly enhances the cytotoxicity of neutrophils in ADCC, the efficacy of rituximab might be enhanced by the addition of G-CSF. In a phase I/II clinical trial, we investigated the safety and efficacy of the combination of rituximab and G-CSF (5 microg/kg/day, administered for 3 days, starting 2 days before each infusion) in 26 relapsed low-grade lymphoma patients. Adverse events occurred in 25/26 patients and mainly consisted of (grade I/II) fever (29%) and allergic reactions (19%). In phases I and II (375 mg/m(2) rituximab+G-CSF), 19 patients were evaluable for efficacy. The response rate was 42% (8/19; 95% CI 20-67%), with 16% (3/19) complete remissions and 26% (5/19) partial remissions. The median duration of response was 18 months, the median time to progression was 24 months. We conclude that the combination of rituximab and G-CSF is well tolerated. Although the overall response rate seems comparable to that reported for rituximab monotherapy, remission duration in this pilot phase II study is remarkably long. Randomized comparison with rituximab monotherapy should substantiate this promising finding.

Analysis of CD20-dependent cellular cytotoxicity by G-CSF-stimulated neutrophils

Rituximab, a chimeric CD20 monoclonal antibody (mAb), is widely used in the treatment of patients with low-grade non-Hodgkin's lymphoma. Possible anti-tumour mechanisms involve complement-mediated lysis and/or antibody-dependent cellular cytotoxicity (ADCC). Because G-CSF greatly enhances the cytotoxicity of neutrophils (PMN) in ADCC, the clinical efficacy of rituximab might be enhanced by the addition of G-CSF. Therefore, we investigated the neutrophil-mediated CD20-dependent cellular cytotoxicity in B cell lines. In contrast to previous studies by others, we found that G-CSF-primed PMN are capable of functioning as effector cells in CD20-dependent cellular cytotoxicity. However, HLA class II mAbs were far more effective. The differences between HLA class II- and CD20-mediated PMN-ADCC were not due to: (1) the use of chimeric (hIgG1) mAbs vs mIgG2a mAbs; (2) HLA class II-induced apoptosis as an 'ADCC-sensitising' mechanism; (3) CD20-induced inhibition of ADCC; (4) inferior membrane mobility of CD20. Analysis of Fcgammareceptor (FcgammaR) involvement showed that although CD20-induced ADCC was mediated mainly via FcgammaRI, for optimal lysis FcgammaRI and FcgammaRII were both required. In contrast, in HLA class II-dependent ADCC both FcgammaRI and II were capable of independently inducing maximum lysis. The mechanism underlying these differences in FcgammaR-binding and activation remains to be elucidated.

Complement activation plays a key role in the side-effects of rituximab treatment

Treatment with rituximab, a chimaeric anti-CD20 monoclonal antibody, can be associated with moderate to severe first-dose side-effects, notably in patients with high numbers of circulating tumour cells. The aim of this study was to elucidate the mechanism of these side-effects. At multiple early time points during the first infusion of rituximab, complement activation products (C3b/c and C4b/c) and cytokines [tumour necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6) and IL-8] were measured in five relapsed low-grade non-Hodgkin's lymphoma (NHL) patients. Infusion of rituximab induced rapid complement activation, preceding the release of TNF-alpha, IL-6 and IL-8. Although the study group was small, the level of complement activation appeared to be correlated both with the number of circulating B cells prior to the infusion (r = 0.85; P = 0.07) and with the severity of the side-effects. We conclude that complement plays a pivotal role in the pathogenesis of side-effects of rituximab treatment. As complement activation can not be prevented by corticosteroids, it might be relevant to study the possible role of complement inhibitors during the first administration of rituximab.

Monoclonal antibodies: a new era in the treatment of non-Hodgkin's lymphoma

Monoclonal antibodies (MAbs) have been used as therapeutic agents for many years. In 1997, Rituxan (IDEC-C2B8, rituximab, MabThera) became the first MAb to be approved by the FDA for a cancer indication. Rituxan served to heighten interest in the therapeutic applications of MAbs. Herceptin (for patients with breast cancer) and Mylotarg (for patients with acute myeloid leukemia) were approved shortly thereafter. Literally dozens of antibodies are currently under investigation for a variety of malignant and non-neoplastic indications. Rituxan is effective in patients with low-grade or follicular, relapsed or refractory non-Hodgkin's lymphoma (NHL). The response rate and time to progression (responders) are in the 50% and 13 months range, respectively. It is also active in intermediate-grade NHL where a large randomized study, in combination with CHOP chemotherapy, has shown a statistically significant increase in complete response (CR) rate (75% vs. 60%), prolongation of 1 year event-free survival (69% vs. 49%) and of overall survival (83% vs. 68%) as compared to CHOP alone. This marks the first time that any agent has shown results superior to CHOP, the curative gold standard for this type of NHL. Other promising antibodies under clinical investigation include: Hu1D10; Anti CD19, 22, 52, and anti-Id antibodies. The safety profile, clinical activity, and mechanism of action of these MAbs make them ideal candidates for combination with chemotherapy or biologicals. Over the next few years, we will see very significant therapeutic advances emerge as this important research yields additional clinical results.

Antibody-targeted immunotherapy for treatment of malignancy

Despite testing since the mid-1900s, only in the past three years have some monoclonal antibodies provided sufficient efficacy and safety data to support regulatory approval as cancer therapy. Adjuvant-edrecolomab monoclonal antibody was approved in Germany after demonstration of a statistically significant 32% improvement over observation alone in the seven-year mortality rate for patients with colorectal cancer. Similarly, trastuzumab monoclonal antibody combined with chemotherapy prolonged the median time to the progression of breast cancer compared to chemotherapy alone. Unconjugated monoclonal antibodies investigated for the treatment of hematologic malignancies include anti-idiotype, CAMPATH-1, and rituximab. Rituximab was the first such therapy approved in the United States for relapsed or refractory low-grade or follicular B-cell non-Hodgkin's lymphoma after demonstration of an overall response rate of 48% and a duration of response of 11.7 months. The radioisotope-conjugated monoclonal antibodies tested as therapy include anti-B1, LYM-1, LL2, anti-CD33, and ibritumomab tiuxetan. Clearly, the full potential of immunotherapy still lies ahead.

Clearing of cells bearing the bcl-2 [t(14;18)] translocation from blood and marrow of patients treated with rituximab alone or in combination with CHOP chemotherapy

PURPOSE

Patients who were PCR-positive for B-cell leukemia-lymphoma 2 (bcl-2) gene rearrangement [t(14;18)] were evaluated for responses to rituximab alone or combined with CHOP.

PATIENTS AND METHODS

Patients had relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma (IWF: A-D). The single-agent trial used 375 mg/m2 weekly x 4; combination therapy included six cycles of CHOP and six 375 mg/m2 infusions of rituximab. Bcl-2 analyses of bone marrow (BM) and peripheral blood (PB) samples at base-line and following therapy were performed using a PCR assay.

RESULTS

In the single-agent trial, of 70 patients whose peripheral blood (PB) was bcl-2 positive at baseline, 36 became bcl-2-negative, 13 remained positive, and 21 varied between positive and negative. The overall response rates (ORRs) were 72%, 31%, and 57%, respectively. Twelve of twenty-two patients with repeat bone marrow (BM) samples were bcl-2-negative three months post-treatment. Of 18 patients in the combination trial, 8 were bcl-2 positive in PB and/or BM. All of seven patients positive in PB at baseline and six of seven patients positive in BM were negative at the end of therapy; all patients responded to treatment (100% ORR).

CONCLUSIONS

Rituximab, alone or combined with CHOP, eradicated bcl-2 positive cells from PB and BM in over half of the patients treated and was associated with a high overall clinical response rate. The impact on disease-free and overall survival awaits long-term follow up.

Antibody-targeted immunotherapy for treatment of non-Hodgkin's lymphoma

The scientific development of immunotherapies and radioimmunotherapies of cancer began more than four decades ago. Over time, it has become apparent that the choice of target antigen, immunogenicity of antibodies, length of antibody half-life, ability of antibodies to recruit immune effector functions, decision on conjugation of antibodies to toxins or radionuclides and antibody manufacturing are critical components of successful development of an immunotherapeutic regimen. Anti-idiotype antibodies were some of the first successful monoclonal antibody treatments developed for non-Hodgkin's lymphoma. In 1997, the chimeric antibody, Rituximab, was approved by the United States Food and Drug Administration for treatment of patients with relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma. In an effort to enhance the efficacy of immunotherapy, toxins and radionuclides have been conjugated to monoclonal antibodies. Ibritumomab, the parent murine antibody of Rituximab, is conjugated to the radioisotope 90Y to create 90Y Ibritumomab tiuxetan, (90Y Zevalin, IDEC-Y2B8). Promising Phase I/II trials have been completed. Phase III experimental trials of 9Y Ibritumomab tiuxetan as treatment for relapsed or refractory NHL are in progress.

A pilot study of the anti-CD20 monoclonal antibody rituximab in patients with refractory immune thrombocytopenia

We conducted a prospective pilot phase I/II clinical trial to evaluate the toxicity and response rate of the chimeric anti-CD20 monoclonal antibody, rituximab (Rituxan; Genentech, Inc, South San Francisco, CA, and IDEC Pharmaceutical Corporation, San Diego, CA), in the treatment of patients with immune thrombocytopenic purpura. Patients with a clinical diagnosis of idiopathic thrombocytopenic purpura who had failed corticosteroid therapy and whose platelet count was less than 75,000/microL were eligible for the study. Rituximab was administered in a dose-escalation fashion using doses ranging from 50 to 375 mg/m2 weekly for 4 weeks. Thirteen patients have been enrolled on the trial to date and 12 have completed the full course of treatment. No unusual toxicity was noted in this patient population. None of the three patients at the lowest dose level achieved a clinical response. Three of nine patients (30%) who have received rituximab at doses close or equal to the full dose have shown an objective clinical response (two complete responses, one partial response). The study is currently ongoing, and conclusions regarding the overall response rate, clinical parameters that influence response, surrogate markers of response, and the underlying mechanism of response remain to be addressed. The current study should provide answers to a number of important questions regarding the role of rituximab in the treatment of this and other autoimmune disorders.

Rituximab: an insider's historical perspective

Rituximab (Rituxan; Genentech, Inc, South San Francisco, CA and IDEC Pharmaceutical Corporation, San Diego, CA) is a unique monoclonal antibody for the treatment of non-Hodgkin's lymphoma. This chimeric mouse/human antibody was discovered in 1991 at IDEC Pharmaceuticals' laboratories, where the antibody was genetically engineered and produced utilizing high-yield expression systems. It is a human IgG1 kappa antibody with mouse variable regions isolated from a murine anti-CD20 antibody, IDEC-2B8, that binds with high affinity to cells expressing the CD20 antigen found on the surface of malignant and normal B cells, but not on other normal tissues. It mediates complement-dependent cell lysis in the presence of human complement, and antibody-dependent cellular cytotoxicity with human effector cells. Also, it has been shown to induce apoptosis and to sensitize chemoresistant human lymphoma cell lines in vitro. Clinical development was expedited (3 years) with the first patient entered in phase I trials in March 1993 and the last patient entered in the phase III study in March 1996. IDEC Pharmaceuticals began a collaboration with Genentech, Inc in March 1995 and with F. Hoffman-LaRoche (Nutley, NJ) shortly thereafter. Marketing approval was granted by the US Food and Drug Administration on November 26, 1997 (and by the European Union on June 2, 1998) for the indication of relapsed or refractory, CD20-positive, B-cell, low-grade or follicular non-Hodgkin's lymphoma. Rituximab is the first therapeutic monoclonal antibody approved for the treatment of cancer and the first single agent approved specifically for therapy for a lymphoma. Substantial research has been performed over the past 8 years to further the understanding of this novel therapeutic. Nevertheless, much remains to be accomplished in key areas such as mechanism of action and resistance, combinations with chemotherapy, biologics and radiotherapy/radioimmunotherapy, role within multimodality regimens, and nonmalignant applications. Research conducted in the coming years should be targeted toward resolving these important issues.

Rituximab anti-CD20 monoclonal antibody therapy in non-Hodgkin's lymphoma: safety and efficacy of re-treatment

PURPOSE

This phase II trial investigated the safety and efficacy of re-treatment with rituximab, a chimeric anti-CD20 monoclonal antibody, in patients with low-grade or follicular non-Hodgkin's lymphoma who relapsed after a response to rituximab therapy.

PATIENTS AND METHODS

Fifty-eight patients were enrolled onto this study, and two were re-treated within the study. Patients received an intravenous infusion of 375 mg/m(2) of rituximab weekly for 4 weeks. All patients had at least two prior therapies and had received at least one prior course of rituximab, with a median interval of 14.5 months between rituximab courses.

RESULTS

Most adverse experiences (AEs) were transient grade 1 or 2 events occurring during the treatment period. Clinically significant myelosuppression was not observed; hematologic toxicity was generally mild and reversible. No patient developed human antichimeric antibodies after treatment. The type, frequency, and severity of AEs in this study were not apparently different from those reported in the phase III trial of rituximab. The overall response rate in 57 assessable patients was 40% (11% complete response and 30% partial responses). Median time to progression (TTP) in responders and median duration of response (DR) have not been reached, but Kaplan-Meier estimated medians are 17.8 months (range, 5.4+ to 26.6 months) and 16.3 months (range, 3.7+ to 25.1 months), respectively. These estimated medians are longer than the medians achieved in the patients' prior course of rituximab (TTP and DR of 12.4 and 9.8 months, respectively, P: >.1) and in a previously reported phase III trial (TTP in responders and DR of 13.2 and 11.6 months, respectively). Responses are ongoing in seven of 23 responders.

CONCLUSION

In this re-treatment population, safety and efficacy were not apparently different from those after initial rituximab exposure.

Phase I/II 90Y-Zevalin (yttrium-90 ibritumomab tiuxetan, IDEC-Y2B8) radioimmunotherapy dosimetry results in relapsed or refractory non-Hodgkin's lymphoma

Dosimetry studies in patients with non-Hodgkin's lymphoma were performed to estimate the radiation absorbed dose to normal organs and bone marrow from 90Y-Zevalin (yttrium-90 ibritumomab tiuxetan, IDEC-Y2B8) treatment in this phase I/II, multicenter trial. The trial was designed to determine the dose of Rituximab (chimeric anti-CD20, Rituxan, IDEC-C2B8, MabThera), the unlabeled antibody given prior to the radioconjugate to clear peripheral blood B cells and optimize distribution, and to determine the maximum tolerated dose of 90Y-Zevalin [7.4, 11, or 15 MBq/kg (0.2, 0.3, or 0.4 mCi/kg)]. Patients received (111)In-Zevalin (indium-111 ibritumomab tiuxetan, IDEC-In2B8 ) on day 0 followed by a therapeutic dose of 90Y-Zevalin on day 7. Both doses were preceded by an infusion of the chimeric, unlabeled antibody Rituximab. Following administration of (111)In-Zevalin, serial anterior/posterior whole-body scans were acquired. Major-organ radioactivity versus time estimates were calculated using regions of interest. Residence times were computed and entered into the MIRDOSE3 computer software program to calculate estimated radiation absorbed dose to each organ. Initial analyses of estimated radiation absorbed dose were completed at the clinical site. An additional, centralized dosimetry analysis was performed subsequently to provide a consistent analysis of data collected from the seven clinical sites. In all patients with dosimetry data (n=56), normal organ and red marrow radiation absorbed doses were estimated to be well under the protocol-defined upper limit of 20 Gy and 3 Gy, respectively. Median estimated radiation absorbed dose was 3.4 Gy to liver (range 1.2-7.8 Gy), 2.6 Gy to lungs (range 0.72-4.4 Gy), and 0.38 Gy to kidneys (range 0.07-0.61 Gy). Median estimated tumor radiation absorbed dose was 17 Gy (range 5.8-67 Gy). No correlation was noted between hematologic toxicity and the following variables: red marrow radiation absorbed dose, blood T(1/2), blood AUC, plasma T(1/2), and plasma AUC. It is concluded that 90Y-Zevalin administered at nonmyeloablative maximum tolerated doses results in acceptable radiation absorbed doses to normal organs. The only toxicity of note is hematologic and is not correlated to red marrow radiation absorbed dose estimates or T(1/2), reflecting that hematologic toxicity is dependent on bone marrow reserve in this heavily pretreated population.

Combination immunotherapy of relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma with rituximab and interferon-alpha-2a

Rituximab and IFN have each demonstrated single-agent activity in patients with low-grade non-Hodgkin's lymphoma (NHL). A single-arm, multicenter, Phase II trial was conducted to assess the safety and efficacy of combination therapy with rituximab and IFN-alpha-2a in 38 patients with relapsed or refractory, low-grade or follicular, B-cell NHL. IFN-alpha-2a [2.5 or 5 million units (MIU)] was administered s.c., three times weekly for 12 weeks. Starting on the fifth week of treatment, rituximab was administered by i.v. infusion (375 mg/m2) weekly for 4 doses. All 38 patients received four complete infusions of rituximab and were evaluable for efficacy, although 11 patients (29%) did not-receive all 36 injections of IFN. The mean number of IFN-alpha-2a injections was 31 doses; the mean total units received were 141 MIU (maximum, 180 MIU). The study treatment was reasonably well tolerated with no unexpected toxicities stemming from the combination therapy. No grade 4 events were reported. Frequent adverse events during the treatment period included asthenia (35 of 38 patients), chills (31 of 38), fever (30 of 38), headache (28 of 38), nausea (23 of 38), and myalgia (22 of 38). The overall response rate was 45% (17 of 38 patients); 11% had a complete response, and 34% had a partial response. The Kaplan-Meier estimates for the median response duration and the median time to progression in responders are 22.3 and 25.2 months, respectively. Further follow-up is needed to determine whether this treatment combination leads to a significantly longer time to progression than single-agent treatment with rituximab.

Rituximab: the first monoclonal antibody approved for the treatment of lymphoma

Rituximab, a genetically engineered monoclonal chimeric antibody, targets the CD20 antigen expressed on B cells. It was approved by the US Food and Drug Administration on November 26, 1997, for the indication of relapsed or refractory, CD20-positive, B-cell, low-grade or follicular non-Hodgkin's lymphoma (LG/F NHL), and by the European Agency for the Evaluation of Medicinal Products on June 2, 1998, for therapy of patients with Stage III/IV, follicular, chemoresistant or relapsed NHL. Eight Phase II or II clinical trials in LG/F NHL patients have been completed: five single-agent studies and three combination studies. Rituximab has a favorable safety profile: most adverse events (AEs) are Grade 1 or 2, and the frequency of AEs decrease with subsequent infusions. AEs in the combination studies are consistent with those seen with individual agents. For evaluable patients in the single-agent studies, overall response rates (ORR) ranged from 40% to 60%, median duration of response (DR) ranged from 5.9 to 15.0+ months, and median time to progression (TTP) ranged from 8.1 to 19.4+ months. For evaluable patients in the combination studies, the ORR ranged from 45% to 100%, median DR ranged from 11.7+ to 39.1+ months, and median TTP ranged from 12.9+ to 40.5+ months. Studies in intermediate- and high-grade NHL are ongoing. Long-term development plans include evaluating the safety and efficacy of rituximab in various types of lymphoma and in combination with other lymphoma regimens. Future studies may explore ways to increase rituximab efficacy by upregulating CD20 or increasing effector function with different cytokines.

Response criteria for NHL: importance of 'normal' lymph node size and correlations with response rates

BACKGROUND

Oncologic literature cites many different definitions of critical response measurements.

PATIENTS AND METHODS

Response criteria (RC) for non-Hodgkin's lymphoma (NHL) were developed by lymphoma experts, endorsed by international lymphoma clinicians, and applied to a 166-patient rituximab (Rituxan, MabThera) trial by a third-party, blinded panel of NHL experts (LEXCOR). Retrospectively, we analyzed this data using variations of the original RC and comparing with recently published RC.

RESULTS

The definition of a 'normal' lymph node affected the complete response (CR) rate (< or = 1.0 x 1.0 cm, 6%; < or = 1.5 x 1.5 cm, 18%; < or = 2.0 x 2.0 cm, 28%); overall response rate (ORR) was not affected. CR rates increased progressively without > or = 28 days response confirmation: 12% vs. 6% (< or = 1.0 x 1.0 cm), 26% vs. 18% (< or = 1.5 x 1.5 cm), and 36% vs. 28% (< or = 2.0 x 2.0 cm). CR rate and duration of response (DR) were unaffected when only the six largest, rather than all lesions, were measured. When the new RC were applied, CR rate (32%) was higher and DR (13.9 months) and time to progression (15.6 months) were shorter in complete responders.

CONCLUSIONS

Standard RC must be consistently and rigorously applied for accurate comparisons between studies.

Rituximab therapy in Waldenstrom's macroglobulinemia: preliminary evidence of clinical activity

To assess the preliminary efficacy of rituximab therapy in Waldenstrom's macroglobulinemia (WM), we examined the clinical and laboratory data for all patients with WM treated on IDEC Pharmaceuticals sponsored trials and one patient treated at Walter Reed Army Medical Center. Seven symptomatic patients with WM were treated with four (n = 6) or eight (n = 1) weekly infusions of rituximab (375 mg/m2). Patients had received a median of three prior therapies (range 1-4) which included alkylator therapy in all (five patients refractory) and fludarabine in four (all refractory). Therapy was tolerated well in all patients without decrement in cellular immune function or significant infectious morbidity. Partial responses were noted in three of these patients, including two with fludarabine-refractory disease. The median progression-free survival for these patients was 6.6 months (range 2.2-29+ months). These data suggest that rituximab has clinical activity in heavily pre-treated patients with Waldenstrom's macroglobulinemia. Based on these data, clinical studies of Rituximab in previously untreated and treated WM appear indicated.

Phase I/II trial of IDEC-Y2B8 radioimmunotherapy for treatment of relapsed or refractory CD20(+) B-cell non-Hodgkin's lymphoma

PURPOSE

Yttrium-90 ibritumomab tiuxetan (IDEC-Y2B8) is a murine immunoglobulin G1 kappa monoclonal antibody that covalently binds MX-DTPA (tiuxetan), which chelates the radioisotope yttrium-90. The antibody targets CD20, a B-lymphocyte antigen. A multicenter phase I/II trial was conducted to compare two doses of unlabeled rituximab given before radiolabeled antibody, to determine the maximum-tolerated single dose of IDEC-Y2B8 that could be administered without stem-cell support, and to evaluate safety and efficacy.

PATIENTS AND METHODS

Eligible patients had relapsed or refractory (two prior regimens or anthracycline if low-grade disease) CD20(+) B-cell low-grade, intermediate-grade, or mantle-cell non-Hodgkin's lymphoma (NHL). There was no limit on bulky disease, and 59% had at least one mass > or = 5 cm.

RESULTS

The maximum-tolerated dose was 0.4 mCi/kg IDEC-Y2B8 (0.3 mCi/kg for patients with baseline platelet counts 100 to 149,000/microL). The overall response rate for the intent-to-treat population (n = 51) was 67% (26% complete response [CR]; 41% partial response [PR]); for low-grade disease (n = 34), 82% (26% CR; 56% PR); for intermediate-grade disease (n = 14), 43%; and for mantle-cell disease (n = 3), 0%. Responses occurred in patients with bulky disease (> or = 7 cm; 41%) and splenomegaly (50%). Kaplan-Meier estimate of time to disease progression in responders and duration of response is 12.9+ months and 11.7+ months, respectively. Adverse events were primarily hematologic and correlated with baseline extent of marrow involvement with NHL and baseline platelet count. One patient (2%) developed an anti-antibody response (human antichimeric antibody/human antimouse antibody).

CONCLUSION

These phase I/II data demonstrate that IDEC-Y2B8 radioimmunotherapy is a safe and effective alternative for outpatient therapy of patients with relapsed or refractory NHL. A phase III study is ongoing.

Rituximab in indolent lymphoma: the single-agent pivotal trial

Rituximab (Rituxan; IDEC Pharmaceuticals, San Diego, CA, and Genentech, Inc, San Francisco, CA) is a chimeric anti-CD20 monoclonal antibody that targets mature B cells and most B-cell malignancies. Rituximab was the first monoclonal antibody to be approved for therapeutic use for any malignancy. Its approval was based on a single-agent pivotal trial in patients with indolent B-cell lymphoma, in which 166 patients were enrolled from 31 centers in the United States and Canada. The overall results of the trial have been previously reported; additional aspects of the trial (eg, pharmacokinetics) have been reported separately as well. The current report includes an update, expansion, and synthesis of data from the single-agent pivotal trial of rituximab.

Radioimmunotherapy of relapsed non-Hodgkin's lymphoma with zevalin, a 90Y-labeled anti-CD20 monoclonal antibody

Approximately 55,400 new cases of non-Hodgkin's lymphoma (NHL) are diagnosed each year, with the overall prevalence of the disease now estimated to be 243,000. Until recently, treatment alternatives for advanced disease included chemotherapy with or without external beam radiation. Based on the results of several clinical trials, the chimeric monoclonal antibody Rituximab has now been approved by the United States Food and Drug Administration as a treatment for patients with relapsed or refractory, low-grade or follicular, B-cell NHL. Several other monoclonal antibodies in conjugated and unconjugated forms have been evaluated in the treatment of NHL. Ibritumomab, the murine counterpart to Rituximab, radiolabeled with 90Y (Zevalin), is presently being evaluated in clinical trials. The success of radioimmunotherapy is dependent upon the appropriate choice of antibody, isotope, and chelator-linker. The Ibritumomab antibody targets the CD20 antigen. The antibody is covalently bound to the chelator-linker tiuxetan (MX-DTPA), which tightly chelates the isotope 90Y. To date, two Phase I/II Zevalin clinical trials have been completed in patients with low-grade, intermediate-grade, and mantle cell NHL. The overall response rate was 64% in the first trial and 67% in the later trial. Phase II and III trials are ongoing.

Overview of the clinical development of rituximab: first monoclonal antibody approved for the treatment of lymphoma

Rituximab (Rituxan; IDEC Pharmaceuticals, San Diego, CA, and Genentech, Inc, San Francisco, CA) is a genetically engineered monoclonal antibody for the treatment of non-Hodgkin's lymphoma. This chimeric mouse/human, immunoglobulin GI kappa anti-CD20 antibody mediates complement-dependent cell lysis and antibody-dependent cellular cytotoxicity. It also has been shown to sensitize chemoresistant human lymphoma cell lines and to induce apoptosis. It was approved by the Food and Drug Administration on November 26, 1997, for the indication of relapsed or refractory, CD-20 positive, B-cell, low-grade or follicular non-Hodgkin's lymphoma Rituximab is the first monoclonal antibody approved for the treatment of cancer and the first single agent approved specifically for therapy of a lymphoma. The recommended dose is rituximab 375 mg/m2 intravenously weekly x4 infusions. Treatment is well tolerated and outpatient therapy is feasible. Adverse events are mostly grades I and 2, occurring primarily with the first infusion. In a phase II single-agent clinical trial, the overall response rate was 50%, with a median time to progression in responders of 10.2 months. In a larger multicenter trial involving 166 patients, the overall response rate was 48% with 6% complete and 42% partial responses. Median time to progression for responders was 13.2 months and median duration of response was 11.6 months. A 40% response rate has been observed on re-treatment with rituximab. Activity also has been seen in patients with bulky disease. Combination studies have been performed with interferon, cyclophosphamide/doxorubicin/vincristine/prednisone, and radioimmunotherapy. Rituximab, the first monoclonal antibody approved for the treatment of cancer, is safe and effective in treating patients with relapsed or refractory, CD-20 positive, B-cell, low-grade or follicular non-Hodgkin's lymphoma.

Single-agent monoclonal antibody efficacy in bulky non-Hodgkin's lymphoma: results of a phase II trial of rituximab

PURPOSE

A phase II trial was performed to evaluate the safety and efficacy of rituximab, a chimeric anti-CD20 monoclonal antibody, in patients with bulky (> 10-cm lesion) relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Thirty-one patients received intravenous infusions of rituximab 375 mg/m(2) weekly for four doses. All patients had at least one prior therapy (median, three; range, one to 13) and had progressive disease at study entry. Patients were a median of 4 years from diagnosis.

RESULTS

No patient had treatment discontinued because of an adverse event. No patient developed human antichimeric antibody. The overall response rate in 28 assessable patients was 43% with a median time to progression of 8.1 months (range, 4.5 to 18.6+ months) and median duration of response of 5.9 months (range, 2.8 to 12.1+ months). The average decrease in lesion size in patients who achieved a partial response was 76%, and patients with stable disease had a decrease in average lesion size of 26%. Median serum antibody concentration was higher in responders compared with nonresponders, and a negative correlation was shown between antibody concentration and tumor bulk at baseline.

CONCLUSION

Rituximab single-agent outpatient therapy is safe and shows significant clinical activity in patients with bulky relapsed or refractory low-grade or follicular B-cell NHL.

Extended Rituximab (anti-CD20 monoclonal antibody) therapy for relapsed or refractory low-grade or follicular non-Hodgkin's lymphoma

BACKGROUND

Rituximab is a chimeric monoclonal antibody directed against the B-cell CD20 antigen which has been utilized for therapy of B-cell non-Hodgkin's lymphoma (NHL). A previous clinical trial demonstrated that treatment with four weekly doses of 375 mg/m2 of Rituximab in patients with relapsed or refractory low-grade or follicular B-cell non-Hodgkin's lymphoma was well tolerated and had significant clinical activity.

PATIENTS AND METHODS

To assess the safety and efficacy of Rituximab treatment, an open-label, single-arm, multi-center, phase II study of eight consecutive weekly infusions of 375 mg/m2 Rituximab in patients with low-grade or follicular B-cell NHL who had relapsed or had failed primary therapy was conducted. Thirty-seven patients with a median age of 55 years were treated.

RESULTS

Grade 1 or 2 adverse events were the majority of reported toxicities and occurred most frequently with the first infusion, decreasing with subsequent infusions. No patients developed a host antibody response (HACA) to Rituximab. The mean serum immunoglobulin levels for IgG, IgA, and IgM stayed within the normal range throughout the study. The majority of patients who were bcl-2 positive at baseline in peripheral blood became bcl-2 negative during treatment and remained negative at the time of B-cell recovery. In the 37 intent-to-treat patients, 5 (14%) had a complete response and 16 (43%) had a partial response for an overall response rate of 57%. Of 35 evaluable patients, 21 (60%) responded to treatment (14% CR and 46% PR). In responders, the median time to progression (TTP) and the median response duration have not been reached after 19.4+ months and 13.4+ months, respectively.

CONCLUSIONS

The safety profile and efficacy achieved in this pilot study of extended treatment with Rituximab compares favorably with those seen with four weekly doses. Further studies are warranted to investigate whether this or other extended Rituximab schedules will result in increased efficacy in all or in certain subgroups of patients with low-grade or follicular NHL.

Treatment of patients with low-grade B-cell lymphoma with the combination of chimeric anti-CD20 monoclonal antibody and CHOP chemotherapy

PURPOSE

To determine the safety and efficacy of the combination of the chimeric anti-CD20 antibody, Rituxan (Rituximab, IDEC-C2B8; IDEC Pharmaceuticals Corporation, San Diego, CA), and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy.

PATIENTS AND METHODS

Forty patients with low-grade or follicular B-cell non-Hodgkin's lymphoma received six infusions of Rituxan (375 mg/m2 per dose) in combination with six doses of CHOP chemotherapy.

RESULTS

The overall response rate was 95% (38 of 40 patients). Twenty-two patients experienced a complete response (55%), 16 patients had a partial response (40%), and two patients, who received no treatment, were classified as nonresponders. Medians for duration of response and time to progression had not been reached after a median observation time of 29 + months. Twenty-eight of 38 assessable patients (74%) continued in remission during this median follow-up period. The most frequent adverse events attributable to CHOP were alopecia (38 patients), neutropenia (31 patients), and fever (23 patients). The most frequent events attributed to Rituxan were fever and chills, observed primarily with the first infusion. No quantifiable immune response to the chimeric antibody was detected. In a subset of 18 patients, the bcl-2 [t(14;18)] translocation was positive in eight patients; seven of these patients had complete remissions and converted to polymerase chain reaction (PCR) negativity by completion of therapy.

CONCLUSION

This is the first report demonstrating the safety and efficacy of Rituxan anti-CD20 chimeric antibody in combination with standard-dose systemic chemotherapy in the treatment of indolent B-cell lymphoma. The clinical responses suggest an additive therapeutic benefit for the combination with no significant added toxicity. The conversion of bcl-2 from positive to negative by PCR in blood and/or marrow suggests possible clearing of minimal residual disease not previously demonstrated by CHOP chemotherapy alone.

Clinical status and optimal use of rituximab for B-cell lymphomas

Rituximab (IDEC-C2B8 [Rituxan]) is a chimeric anti-CD20 monoclonal antibody (MoAb) that was recently approved by the FDA for the treatment of patients with low-grade or follicular B-cell non-Hodgkin's lymphoma. Its potential efficacy in other B-cell malignancies is currently being explored. This article reviews the mechanisms of action of rituximab, as well as preclinical data and results of the clinical trials that led to its approval. Also discussed are the mechanics of administering rituximab on the recommended weekly x 4 outpatient schedule. Finally, the article describes ongoing and planned trials of rituximab in other dosage schedules, in other B-cell neoplasms, and in conjunction with chemotherapy. As the first MoAb to gain FDA approval for the treatment of a malignancy, rituximab signals the beginning of a promising new era in cancer therapy.

Association of serum Rituximab (IDEC-C2B8) concentration and anti-tumor response in the treatment of recurrent low-grade or follicular non-Hodgkin's lymphoma

BACKGROUND

Monoclonal antibodies are being utilized for treatment of patients with low-grade non-Hodgkin's lymphoma as well as other cancers. Results from phase I and II clinical studies has shown that the chimeric monoclonal antibody Rituximab has minimal toxicity and significant therapeutic activity in low grade non-Hodgkin's lymphoma.

PATIENTS AND METHODS

We have recently reported on a multicentre pivotal phase III clinical trial involving 166 patients with recurrent low-grade lymphoma who were treated with four infusions of Rituximab. Eighty patients (48%) achieved objective responses including 10 patients (6%) with complete responses. Overall, 126 patients (76%) had a > or = 20% reduction in overall tumor size. The median response duration and time to progression are 11.6 and 13.2 months, respectively. The infusional and long term toxicities were limited.

RESULTS

In this report we describe the pharmacokinetic data obtained on these patients. Measurable concentrations of Rituximab were detected in all patients after the first infusion and increased throughout the treatment course. The half-life of the monoclonal antibody increased from 76.3 hours after the first infusion to 205.8 hours after the fourth infusion and was concomitant with a four-fold decrease in the antibody clearance. At three months and six months post-treatment, the median Rituximab serum levels were 20.3 micrograms/ml (range 0.0 to 96.8 micrograms/ml in 104 patients) and 1.3 micrograms/ml (range 0.0-28.7 micrograms/ml in 13 patients), respectively. A statistically significant correlation was found between the median antibody concentration and response for multiple time points during the treatment and followup. The mean serum antibody concentration was also inversely correlated with measurements of tumor bulk and with the number of circulating B cells at baseline.

CONCLUSIONS

We conclude that Rituximab is therapeutically effective against B-cell lymphoma. Pharmacokinetic data suggests that certain subsets of patients may possibly benefit from increased dosing and studies to address this are currently underway.

Rituximab chimeric anti-CD20 monoclonal antibody therapy for relapsed indolent lymphoma: half of patients respond to a four-dose treatment program

PURPOSE

The CD20 antigen is expressed on more than 90% of B-cell lymphomas. It is appealing for targeted therapy, because it does not shed or modulate. A chimeric monoclonal antibody more effectively mediates host effector functions and is itself less immunogenic than are murine antibodies.

PATIENTS AND METHODS

This was a multiinstitutional trial of the chimeric anti-CD20 antibody, IDEC-C2B8. Patients with relapsed low grade or follicular lymphoma received an outpatient treatment course of IDEC-C2B8 375 mg/m2 intravenously weekly for four doses.

RESULTS

From 31 centers, 166 patients were entered. Of this intent-to-treat group, 48% responded. With a median follow-up duration of 11.8 months, the projected median time to progression for responders is 13.0 months. Serum antibody levels were sustained longer after the fourth infusion than after the first, and were higher in responders and in patients with lower tumor burden. The majority of adverse events occurred during the first infusion and were grade 1 or 2; fever and chills were the most common events. Only 12% of patients had grade 3 and 3% grade 4 toxicities. A human antichimeric antibody was detected in only one patient.

CONCLUSION

The response rate of 48% with IDEC-C2B8 is comparable to results with single-agent cytotoxic chemotherapy. Toxicity was mild. Attention needs to be paid to the rate of antibody infusion, with titration according to toxicity. Further investigation of this agent is warranted, including its use in conjunction with standard chemotherapy.

IDEC-C2B8: results of a phase I multiple-dose trial in patients with relapsed non-Hodgkin's lymphoma

PURPOSE

To evaluate the safety, pharmacokinetics, and biologic effect of multiple doses of the chimeric anti-CD20 monoclonal antibody (mAb) IDEC-C2B8 in patients with relapsed B-cell lymphoma.

PATIENTS AND METHODS

Twenty patients with relapsed low-grade (n = 15) or intermediate-/high-grade (n = 5) lymphoma received weekly infusions times four of 125 mg/m2 (n = 3), 250 mg/m2 (n = 7), or 375 mg/m2 (n = 10) of IDEC-C2B8.

RESULTS

Infusional side effects during the initial infusion were mainly grade I/II fever, asthenia, chills, nausea, rash, and urticaria. More serious events were rare. Peripheral-blood B cells were rapidly depleted and slowly recovered over 3 to 6 months. There was no change in mean immunoglobulin (Ig) levels. Antibody serum half-life (and maximum concentration [Cmax]) generally increased between the first and fourth infusions (33.2 hours v 76.6 hours, respectively) following the 375-mg/m2 doses. Six of 18 assessable patients had a partial remission (PR), with a median time to disease progression of 6.4 months (range, 3 to 21.7). Minor responses (MRs) were observed in five patients and progressive disease (PD) in seven. Tumor responses occurred in peripheral blood, bone marrow (BM), spleen, bulky lymph nodes, and extranodal sites, and in patients who had relapsed following high-dose myeloablative chemotherapy. Six of 14 patients (40%) with a low-grade histology responded. Four of six with bulky disease had a PR.

CONCLUSION

IDEC-C2B8 chimeric anti-CD20 mAb therapy is well tolerated and has clinical activity in patients with relapsed B-cell lymphoma. The 375-mg/m2 dose has been selected for a phase II trial in patients with relapsed low-grade or follicular B-cell lymphoma.

IDEC-C2B8 (Rituximab) anti-CD20 monoclonal antibody therapy in patients with relapsed low-grade non-Hodgkin's lymphoma

IDEC-C2B8 is a chimeric monoclonal antibody (MoAb) directed against the B-cell-specific antigen CD20 expressed on non-Hodgkin's lymphomas (NHL). The MoAb mediates complement and antibody-dependent cell-mediated cytotoxicity and has direct antiproliferative effects against malignant B-cell lines in vitro. Phase I trials of single doses up to 500 mg/m2 and 4 weekly doses of 375 mg/m2 showed clinical responses with no dose-limiting toxicity. We conducted a phase II, multicenter study evaluating four weekly infusions of 375 mg/m2 IDEC-C2B8 in patients with relapsed low-grade or follicular NHL (Working Formulation groups A-D). Patients were monitored for adverse events, antibody pharmacokinetics, and clinical response. Thirty-seven patients with a median age of 58 years (range, 29 to 81 years) were treated. All patients had relapsed after chemotherapy (median of 2 prior regimens) and 54% had failed aggressive chemotherapy. Infusional side effects (grade 1-2) consisting of mild fever, chills, respiratory symptoms, and occasionally hypotension were observed mostly with the initial antibody infusion and were rare with subsequent doses. Peripheral blood B-cell depletion occurred rapidly, with recovery beginning 6 months posttreatment. There were no significant changes in mean IgG levels and infections were not increased over what would be expected in this population. Clinical remissions were observed in 17 patients (3 complete remissions and 14 partial remissions), yielding an intent to treat response rate of 46%. The onset of these tumor responses was as soon as 1 month posttreatment and reached a maximum by 4 months posttreatment. In the 17 responders, the median time to progression was 10.2 months (5 patients exceeding 20 months). Likelihood of tumor response was associated with a follicular histology, with the ability to sustain a high serum level of antibody after the first infusion, and with a longer duration of remission to prior chemotherapy. One patient developed a detectable but not quantifiable immune response to the antibody that had no clinical significance. IDEC-C2B8 in a dose of 375 mg/m2 weekly for 4 weeks has antitumor activity in patients with relapsed low-grade or follicular NHL. Results with this brief, outpatient treatment compare favorably with results with standard chemotherapy, and IDEC-C2B8 has a better safety profile. Further studies evaluating IDEC-C2B8 in other types of lymphoma either alone or combined with chemotherapy are warranted.

Amsacrine-associated cardiotoxicity: an analysis of 82 cases

Amsacrine is an antileukemia drug being widely used in North America, Europe, Australia, and New Zealand. In the initial clinical trials, patients treated with amsacrine developed occasional instances of acute cardiac arrhythmias and cardiomyopathy. We review and analyze the features of cardiac abnormalities associated with amsacrine in 82 patients, 27 of whom have not been previously reported. The rest have been reported in the literature, but we have included a large amount of additional information about these patients in our analysis. We conclude that amsacrine-related cardiac events are less common than those related to anthracycline chemotherapeutic agents. Manifestations of such toxicity include ECG abnormalities, ventricular and atrial arrhythmias, sudden death, and congestive heart failure. There is little or no cumulative dose effect. Hypokalemia may be a risk factor for development of serious tachyarrhythmias, but such problems can occur despite a normal serum potassium level. Amsacrine appears to affect depolarization and repolarization of the heart, but the mechanism is unknown.

CI-921: an analog of amsacrine with experimental activity against solid tumors

CI-921, a 4,5-disubstituted analog of amsacrine, has been selected for clinical testing because of its experimental activity in vitro and in vivo against solid tumors as well as leukemias. In studies conducted by Baguley and co-workers, CI-921 demonstrated activity against Lewis lung carcinoma in vivo, producing marked increases in life span and a high proportion of 60-day survivors. An intermittent schedule of administration was more effective than a daily X 5 or daily X 9 schedule. In pharmacokinetic studies in dogs, CI-921 achieved higher plasma concentrations and was cleared more slowly than amsacrine. CI-921 is readily soluble in water and may have antitumor activity when administered orally. Animal toxicology studies indicate that dose-related, reversible leukopenia and thrombocytopenia occur, as well as gastrointestinal toxicity, elevation of alkaline phosphatase and generalized lymphoid depletion. Phase I clinical testing of a parenteral formulation is in progress.

A phase I trial of ametantrone acetate (NSC-287513)

Ametantrone acetate is an intensely blue anthracenedione undergoing clinical trials in man. In this Phase I study, 20 patients received 39 courses of drug as a single IV dose given daily for five days and repeated every three weeks (21 days). Dosage escalations proceeded from 15 mg/m2 to 35 mg/m2. Predictable and reversible leukopenia was the dose limiting toxicity. One previously untreated patient with renal cell carcinoma metastatic to the lungs and right arm experienced a partial response of 51 days duration. Nine patients had pharmacokinetic studies performed during the study. Ametantrone was extensively distributed (apparent volume of distribution, 26.3 l/m2) and demonstrated a short half-life (harmonic mean half-life, 0.38 hour). The maximum tolerated dose in this study was 35 mg/m2. Recommended doses for Phase II trials are 30 mg/m2 in good risk patients and 25 mg/m2 in poor risk patients. Because of the partial response seen in one patient with renal cell carcinoma, Phase II trials should include this tumor category in order to better define the activity of ametantrone in this disease. In addition, since the total amount of drug that could be given to patients receiving the five day schedule (125-150 mg/m2) was approximately the same amount that could be administered as a single dose (140 mg/m2), it would appear that the only advantage of the daily times five day dosage schedule would be in the lower incidence of bluish skin discoloration.