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.

Phase I trial of the amsacrine analogue 9-[( 2-methoxy-4-[(methylsulfonyl)amino]-phenyl]amino)-N,5-dimethyl-4- acridinecarboxamide (CI-921).

CI-921, an analogue of amsacrine with superior activity against in vivo and in vitro experimental tumor models, has been studied in 16 patients with solid tumors refractory to chemotherapy or for which conventional therapy does not exist. Thirty-nine cycles were given and doses escalated from 39 to 810 mg/m2. This total dose was divided over 3 consecutive days and administered by 15-min infusion each day, repeated three times weekly. Neutropenia (Eastern Cooperative Oncology Group) Grade greater than or equal to 3 occurred at Day 8 (range, 7-13) in 10/13 courses at 648 mg/m2 and in 2/2 courses at 810 mg/m2 with recovery in 10 (range, 4-20) days. At 810 mg/m2 Grade 2 mucositis and phlebitis were noted. Mild nausea and venous irritation occurred in some patients at doses greater than or equal to 288 mg/m2. No objective response was seen. Pharmacokinetics were evaluated following 65 infusions on Days 1 and 3 with plasma concentrations of CI-921 measured by high performance liquid chromatography. Peak plasma concentrations ranged from 3.36 to 85.6 mumol/liter and were significantly correlated with dose. Mean (range) model-independent pharmacokinetic parameters were: distribution half-life, 0.46 h (0.24-1.08); elimination half-life, 2.63 h (1.08-4.98); mean residence time, 2.0 h (1.05-3.35); plasma clearance, 158 ml/h/kg (95-290); and steady-state volume of distribution, 319 ml/kg (219-614) with no significant difference between Day 1 and 3. Toxicity as defined by absolute granulocyte count nadir was significantly correlated with dose, area under concentration-time curve, and peak plasma concentration. The recommended dose for Phase II studies in this schedule is 648 mg/m2 (216 mg/m2 daily for 3 days) repeated every three weeks.

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.

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.

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.

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 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.

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.

Rituximab using a thrice weekly dosing schedule in B-cell chronic lymphocytic leukemia and small lymphocytic lymphoma demonstrates clinical activity and acceptable toxicity.

PURPOSE: Rituximab has been reported to have little activity in small lymphocytic lymphoma (SLL)/chronic lymphocytic leukemia (CLL) and to be associated with significant infusion-related toxicity. This study sought to decrease the initial toxicity and optimize the pharmacokinetics with an alternative treatment schedule. PATIENTS AND METHODS: Thirty three patients with SLL/CLL received dose 1 of rituximab (100 mg) over 4 hours. In cohort I (n = 3; 250 mg/m(2)) and cohort II (n = 7; 375 mg/m(2)) rituximab was administered on day 3 and thereafter three times weekly for 4 weeks using a standard administration schedule. Cohort III (n = 23; 375 mg/m(2)) administered rituximab similar to cohort II for the first two treatments and then over 1 hour thereafter. RESULTS: A total of 33 CLL/SLL patients were enrolled; only one patient discontinued therapy because of infusion-related toxicity. Thirteen patients developed transient hypoxemia, hypotension, or dyspnea that were associated with significant changes in baseline interleukin-6, interleukin-8, tumor necrosis factor alpha, and interferon gamma compared with those not experiencing such reactions. Infusion-related toxicity occurred more commonly in older (median age 73 v 62 years; P =.02) patients with no other pretreatment clinical or laboratory features predicting occurrence of these events. The overall response rate was 45% (3% CR, 42% PR; 95% CI 28% to 64%). Median response duration for these 15 patients was 10 months (95% CI, 6.8-13.2; range, 3 to 17+). CONCLUSION: Rituximab administered thrice weekly for 4 weeks demonstrates clinical efficacy and acceptable toxicity. Initial infusion-related events seem to be cytokine mediated and resolve by the third infusion making rapid administration possible. Future combination studies of rituximab with other therapies in CLL seem warranted.

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.

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.

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.

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.

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 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.

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.

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.

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.