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.

Anti-CD22 and anti-CD79B antibody drug conjugates are active in different molecular diffuse large B-cell lymphoma subtypes

Antibody drug conjugates (ADCs), in which cytotoxic drugs are linked to antibodies targeting antigens on tumor cells, represent promising novel agents for the treatment of malignant lymphomas. Pinatuzumab vedotin is an anti-CD22 ADC and polatuzumab vedotin an anti-CD79B ADC that are both linked to the microtubule-disrupting agent monomethyl auristatin E (MMAE). In the present study, we analyzed the activity of these agents in different molecular subtypes of diffuse large B-cell lymphoma (DLBCL) both in vitro and in early clinical trials. Both anti-CD22-MMAE and anti-CD79B-MMAE were highly active and induced cell death in the vast majority of activated B-cell-like (ABC) and germinal center B-cell-like (GCB) DLBCL cell lines. Similarly, both agents induced cytotoxicity in models with and without mutations in the signaling molecule CD79B. In line with these observations, relapsed and refractory DLBCL patients of both subtypes responded to these agents. Importantly, a strong correlation between CD22 and CD79B expression in vitro and in vivo was not detectable, indicating that patients should not be excluded from anti-CD22-MMAE or anti-CD79B-MMAE treatment because of low target expression. In summary, these studies suggest that pinatuzumab vedotin and polatuzumab vedotin are active agents for the treatment of patients with different subtypes of DLBCL.

Long-term follow-up of lenalidomide in relapsed/refractory mantle cell lymphoma: subset analysis of the NHL-003 study

BACKGROUND

Mantle cell lymphoma (MCL) is an uncommon type of non-Hodgkin lymphoma with poor overall prognosis, requiring the development of new therapies. Lenalidomide is an immunomodulatory agent demonstrating antitumor and antiproliferative effects in MCL. We report results from a long-term subset analysis of 57 patients with relapsed/refractory MCL from the NHL-003 phase II multicenter study of single-agent lenalidomide in patients with aggressive lymphoma

DESIGN

Lenalidomide was administered orally 25 mg daily on days 1-21 every 28 days until progressive disease (PD) or intolerability. The primary end point was overall response rate (ORR).

RESULTS

Fifty-seven patients with relapsed/refractory, advanced-stage MCL had a median of three prior therapies. The ORR was 35% [complete response (CR)/CR unconfirmed (CRu) 12%], with a median duration of response (DOR) of 16.3 months (not yet reached in patients with CR/CRu) by blinded independent central review. The median time to first response was 1.9 months. Median progression-free survival was 8.8 months, and overall survival had not yet been reached. The most common grade 3/4 adverse events (AEs) were neutropenia (46%), thrombocytopenia (30%), and anemia (13%).

CONCLUSIONS

These results show the activity of lenalidomide in heavily pretreated, relapsed/refractory MCL. Responders had a durable response with manageable side-effects. Clinical trial number posted on www.clinicaltrials.gov NCT00413036.

Phase II trial of galiximab (anti-CD80 monoclonal antibody) plus rituximab (CALGB 50402): Follicular Lymphoma International Prognostic Index (FLIPI) score is predictive of upfront immunotherapy responsiveness

BACKGROUND

This phase II CALGB trial evaluated the activity and safety of an extended induction schedule of galiximab (G) plus rituximab (R) in untreated follicular lymphoma (FL).

PATIENTS AND METHODS

Patients with previously untreated FL (grades 1, 2, 3a) received 4 weekly infusions of G + R, followed by an additional dose every 2 months four times. International Workshop Response Criteria were used to evaluate response.

RESULTS

Sixty-one patients were treated and antibody infusions were well tolerated. The overall response rate (ORR) is 72.1% (95% confidence interval 59.2% to 82.9%): 47.6% complete response (CR)/unconfirmed complete response (CRu) and 24.6% partial response. At a median follow-up time of 4.3 years (range, 0.3-5.3 years) median progression-free survival (PFS) is 2.9 years. Notably, Follicular Lymphoma International Prognostic Index (FLIPI) correlated with ORR, CR rate, and PFS, and the low-risk FLIPI group (n = 12) achieved a 92% ORR, 75% CR/CRu rate, and 75% 3-year PFS.

CONCLUSIONS

An extended induction schedule of G + R in previously untreated FL is well tolerated and appears particularly efficacious in those patients with low-risk FLIPI scores. In addition, this trial served as the initial platform for additional CALGB 'doublet' combination regimes of rituximab plus other novel targeted agents.

An international phase II trial of single-agent lenalidomide for relapsed or refractory aggressive B-cell non-Hodgkin's lymphoma

BACKGROUND

Lenalidomide is an immunomodulatory agent with antitumor activity in B-cell malignancies. This phase II trial aimed to demonstrate the safety and efficacy of lenalidomide in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), follicular grade 3 lymphoma (FL-III), or transformed lymphoma (TL).

METHODS

Patients received oral lenalidomide 25 mg on days 1-21 every 28 days as tolerated or until progression. The primary end point was overall response rate (ORR).

RESULTS

Two hundred and seventeen patients enrolled and received lenalidomide. The ORR was 35% (77/217), with 13% (29/217) complete remission (CR), 22% (48/217) partial remission, and 21% (45/217) with stable disease. The ORR for DLBCL was 28% (30/108), 42% (24/57) for MCL, 42% (8/19) for FL-III, and 45% (15/33) for TL. Median progression-free survival for all 217 patients was 3.7 months [95% confidence interval (CI) 2.7-5.1]. For 77 responders, the median response duration lasted 10.6 months (95% CI 7.0-NR). Median response duration was not reached in 29 patients who achieved a CR and in responding patients with FL-III or MCL. The most common adverse event was myelosuppression with grade 4 neutropenia and thrombocytopenia in 17% and 6%, respectively.

CONCLUSION

Lenalidomide is well tolerated and produces durable responses in patients with relapsed or refractory aggressive non-Hodgkin's lymphoma.

A Phase 1b/2 trial of mapatumumab in patients with relapsed/refractory non-Hodgkin's lymphoma

Background:

We conducted a multicentre Phase 1b/2 trial to evaluate the safety and efficacy of mapatumumab, a fully human agonistic monoclonal antibody to the tumour necrosis factor-related apoptosis-inducing ligand receptor 1 (TRAIL-R1) in patients with relapsed non-Hodgkin's lymphoma (NHL).

Methods:

Forty patients with relapsed or refractory NHL were treated with either 3 or 10 mg kg⁻¹ mapatumumab every 21 days. In the absence of disease progression or prohibitive toxicity, patients received a maximum of six doses.

Results:

Mapatumumab was well tolerated, with no patients experiencing drug-related hepatic or other dose-limiting toxicity. Three patients with follicular lymphoma (FL) experienced clinical responses, including two with a complete response and one with a partial response. Immunohistochemistry staining of the TRAIL-R1 suggested that strong staining in tumour specimens did not appear to be a requirement for mapatumumab activity in FL.

Conclusions:

Mapatumumab is safe and has promising clinical activity in patients with FL.

Novel antibodies in the treatment of non-Hodgkin's lymphoma

Monoclonal antibodies (mAbs) have revolutionised the treatment of malignancies, especially non-Hodgkin's lymphoma (NHL). Antibody-based therapies target tumour cells expressing a specific antigen while sparing the majority of normal cells leading to a decrease in treatment-associated toxicity. Rituximab, a monoclonal antibody directed against CD20 on B cells, was the first monoclonal antibody to be approved by the US Food and Drug Association (FDA) in 1997 for the treatment of patients with relapsed/refractory, follicular or low-grade NHL . However, it was soon realised that not all patients respond to rituximab therapy and close to 60% of patients with follicular lymphoma who were previously sensitive to rituximab become 'resistant' to repeat rituximab therapy. This led to further attempts to improve the antitumour activity of anti-CD20 mAbs (i.e. 2nd/3rd generation anti-CD20s), and to identify additional potential targets on lymphoma cells other than CD20. A number of these antibodies directed against lymphoma cell targets other than CD20 are now undergoing development, many of which are currently in clinical trials. This manuscript focuses on an overview of these 'non-anti-CD20' novel mAbs for NHL.

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.

Strategies to overcoming rituximab-chemotherapy resistance by targeting the autophagy pathway using bortezomib in combination with the Bcl-2 inhibitor obatoclax in non-Hodgkin's lymphomas (NHL)

8543

We found that repeated rituximab exposure leads to deregulation of Bcl-2 proteins and concomitant chemotherapy resistance. We demonstrated that obatoclax (O), a potent Bcl-2 inhibitor, enhanced the anti-tumor activity of rituximab or chemotherapy agents. The proteasome is known to regulate Bcl-2 family members expression. In the current work we study the interactions between bortezomib (B) and O against B-cell NHL. Studies were conducted in rituximab sensitive (RSCL) and resistant cell lines (RRCL), as well as in malignant B-cells derived from patients with NHL (n = 20). Cells were exposed in vitro to escalating doses of O with/without B. Cell death was determined by the Cell glow luminescent assay and DNA synthesis by [3H]-Thymidine incorporation. To further study the mechanisms of O and/or B action, RSCL or RRCL were exposed to O or B with or without caspase inhibitors; viability was evaluated as above and apoptosis by flow cytometry and PARP cleavage. Autophagy was detected by LC3 conversion and electron microscopy (EM). Changes in p53 or BH3 domain proteins were evaluated by Western blot. To determine the role of p53 and/or autophagy in O or B activity, SiRNA assays were performed. O or B monotherapy induced time- and dose-dependent cell death of all cells tested. In vitro exposure of RRCL, RSCL and lymphoma specimens to O and B resulted in significant synergistic activity. In vitro exposure of NHL cells to O lead to p53 degradation and Noxa or PUMA induction; while exposure to B resulted in Bax upregulation and Mcl-1 downregulation. The ability of O or B to induce PARP cleavage varied between patient samples and was not observed in RRCL. Inhibition of caspase activity did not affect the ability of O or B to kill NHL cells. Induction of autophagy was detected by LC3 conversion and EM not only in RSCL or RRCL but also in patient-derived tumor cells. Additionally, cell death induced by O could be inhibited by knock-down of Beclin-1 or p53. Our data suggest that O and B have a dual mechanism of action. We also provide data suggesting that both p53 and Beclin-1 have a pivotal role in response to O. Our findings strongly suggest that O added to B may result in a novel and potent therapeutic strategy against aggressive NHL.

No significant financial relationships to disclose.

Efficacy and safety of lenalidomide oral monotherapy in patients with relapsed or refractory diffuse large B-cell lymphoma: Results from an international study (NHL-003)

e19504

Background: Patients with diffuse large-B-cell lymphoma (DLBCL) who are not cured with R-CHOP or high-dose chemotherapy with autologous stem cell rescue have a dismal prognosis. A recent phase II trial (NHL-002) of lenalidomide in patients with relapsed or refractory aggressive non-Hodgkin's lymphoma (NHL) demonstrated a 19% overall response rate (ORR) with a 7-month median duration of response (DR) in the subset of patients with DLBCL. A supporting international phase II trial (NHL-003) of single-agent lenalidomide was initiated for patients with relapsed or refractory aggressive NHL that had received at least one prior treatment and had measurable disease. Herein, we report the data from the DLBCL patients enrolled in this trial. Methods: Patients received 25 mg oral lenalidomide once daily on days 1–21 of every 28-day cycle and continued therapy until disease progression or toxicity. The 1999 IWLRC methodology was used to assess response and progression. Results: One hundred-three DLBCL patients were enrolled and were evaluable for response assessment. The median age was 66 years (21–87) and 70 patients (68%) were male. Median time from diagnosis was 2 years (0.4–18.6), patients had received a median of 3 prior treatment regimens (1–10) and 46 of the patients (45%) had received a prior stem cell transplant (DLBCL-stem cell). Response rates are shown in the Table . Grade 3 or 4 adverse events occurring in more than 5% of patients were neutropenia (34%), thrombocytopenia (18%), asthenia (9%), anemia (8%), leucopenia (7%), back pain (6%) and dyspnea (6%). Conclusions: This international study demonstrates that lenalidomide is active in heavily pre-treated patients with relapsed or refractory DLBCL and has manageable side effects.

[Table: see text]

[Table: see text]

Correlation of surface expression of CD11b or CD32 in polymorphonuclear cells (PMNs) and CD69 in natural killer cells (NK) with progression-free survival (PFS) following chemoimmunotherapy with rituximab and liposomal doxorubicin (LD) in patients (pts) with relapsed or refractory B-cell lymphoma

8583

Antibody dependent cellular citotoxicity (ADCC) play a significant role in rituximab's anti-tumor activity. FcγRIIIa polymorphisms have been associated with clinical responses to rituximab. The predictive value of FcγRIIIa polymorphisms is lost when rituximab is combined with chemotherapy. Alternative assays to assess the immune system had not been studied in patients treated with rituximab plus chemotherapy. To this end, we prospectively studied the pre-treatment quality and function of PMNs and NK cells from pts with refractory/relapsed B-cell lymphomas in a Phase I/II trial. Forty-two B-cell lymphoma patients pts completed treatment. Demographics: 22M:20F; Median age = 61.8 (range 35–83); Patients received R (375 mg/m2/dose) on day 1 and LD (30 mg/m2/dose) on day 3 q21 day × 6 cycles. Pre-treatment flow cytometry was performed to assess surface expression of CD11b, CD62, CD69, CD16, CD32 and CD64 in PMNs or NKcells was performed. Serum or PBMC's were isolated from each patient and used 51Cr release assays to study rituximab-associated complement mediated cytotoxicity (CMC) or ADCC. To correlate laboratory parameters with response rate, and PFS patients were divided in tertiles. Overall, R+LD was very well-tolerated. Overall response rate (ORR) = 68% (39% CR, 19% PR); median time-to-progression (TTP) = 12 m. Surface expression of CD32 in PMNs, and CD69 in NKcells correlated with better response rates. Surface expression of CD11b and CD32 in the PMN's correlated with a longer PFS (P = 0.040 and P = 0.015, respectively).There was a non-statistically significant trend towards an improved in PFS in those patients whom their PBMC's exhibited a higher degree of ex-vivo rituximab ADCC. Our data suggest that R+LD is a safe and effective regimen and that the quality of the immune system prior to a chemo-immunotherapy regimen may play a role in clinical outcomes, specifically the expression of CD11b and CD32 in PMNs or CD69 in NKcells. Our data supports further research in seeking ways to enhance the quality of the immune system to improve responses to rituximab ± chemotherapy.

[Table: see text]

Efficacy and safety of lenalidomide oral monotherapy in patients with relapsed or refractory mantle-cell lymphoma: Results from an international study (NHL-003)

8569

Introduction: Relapsed or refractory MCL patients demonstrated a promising overall response rate (ORR) of 53% with a median duration of response (DR) of 13.7 months to single-agent lenalidomide when analyzed as a subset in a recent a phase II study (NHL-002). A supporting international phase II trial (NHL-003) of single-agent lenalidomide was initiated for patients with relapsed or refractory aggressive NHL. In this report, we analyze the current results from the MCL patients enrolled in this trial. Methods: Patients with relapsed or refractory MCL and measurable disease 2 cm after at least 1 prior treatment regimen were eligible. Patients received 25 mg of lenalidomide orally once daily on days 1–21 of every 28-day cycle. Patients continued therapy until disease progression or toxicity. The 1999 IWLRC methodology was used to assess response and progression. Results: Fifty-four MCL patients were enrolled and were evaluable for response assessment. Median age was 69 years (33–82) and 40 patients (74%) were male. Median time from diagnosis was 3.2 years (0.4–10.4), patients had received a median of 3 prior treatments (1–8), 17 of the patients (32%) had received prior bortezomib therapy (MCL-bortezomib), and 14 (26%) had received a prior stem cell transplant (MCL-stem cell). Response rates are shown in the Table. The most common grade 3 or 4 adverse events were neutropenia (43%), thrombocytopenia (22%) and anemia (11%). Conclusions: This is the second study to demonstrate that lenalidomide oral monotherapy is effective in the treatment of patients with relapsed or refractory MCL, with manageable side effects.

[Table: see text]

[Table: see text]

Efficacy of the DAC inhibitor LBH589 in both rituximab-sensitive and rituximab-resistant lymphomas and effect on the antitumor activity of chemotherapy agents, monoclonal antibodies, and bortezomib

8576

Deacetylases (DACs) are enzymes that remove the acetyl groups from target proteins [histones (class I) and non-histones (class II)], leading to regulation of gene transcription and other cellular processes. LBH589 is a novel and potent DAC class I and II Inhibitor undergoing pre-clinical and clinical testing. In order to develop therapeutic options for refractory/resistant B-cell lymphomas we studied the effects of LBH589 in the anti-tumor activity of chemotherapy agents and monoclonal antibodies in a panel of rituximab-sensitive cell lines (RSCL), rituximab-resistant cell lines (RRCL), and in lymphoma cells isolated from patients with treatment-naïve or refractory/relapsed B-cell lymphomas by negative selection using magnetic beads. NHL cells lines were exposed to the following chemotherapy agents or monoclonal antibodies: CDDP, doxorubicin, vincristine, bortezomib or rituximab, veltuzumab, or isotype, alone or in combination with LBH589. In dose-sequence studies the treatment with LBH589 preceded or followed in vitro exposure to the chemotherapy agent or the monoclonal antibody by 24 hrs. Changes in mitochondrial potential were determined by alamar blue reduction using a kinetic assay. Patient-derived tumor cells were exposed to either LBH589, bortezomib or both. Changes in ATP content were determined by cell titer glow assay. RNA was isolated from NHL cell lines exposed to LBH859 and changes in gene expression of the Bcl-2 family members were determined by qualitative polymerase chain reaction (PCR). LBH589 was active as a single agent against RSCL, RRCL or patient-derived tumor cells. In addition, Bcl-XL gene down-regulation was observed following exposure to LBH859. Synergistic activity was observed by combining LBH589 and chemotherapy agents, bortezomib or either of the two anti-CD20 mAbs studied. The sequence of administration impacted the degree of antitumor activity observed. Our data suggests that LBH589 is active against various RSCL, RRCL and patient-derived tumor cells. Findings suggest that LBH589 added to systemic anti-CD20 and/or chemotherapy could result in a novel and potent treatment strategy against B-cell lymphomas.

No significant financial relationships to disclose.

Antitumor effects of lenalidomide in combination with IDEC114 (anti CD80) in lymphoma bearing severe combined immunodeficiency (SCID) mouse model

3037

Background: Lenalidomide is a thalidomide analogue with immunomodulatory effects. We previously demonstrated that lenalidomide enhances the biological activity of rituximab. In our current work we further studied the effects of combining lenalidomide with IDEC114, a primatized anti-CD80 monoclonal antibody, which is undergoing clinical testing in B-cell lymphoma. Methods: Raji cells were exposed in vitro to lenalidomide (10μg/ml) or DMSO over five days. Changes in DNA synthesis were determined by [3H]-thymidine uptake. For ADCC and CMC assays, lenalidomide or control exposed Raji cells were labeled to 51Cr and then exposed to IDEC114 or isotype control and PBMC’s or human serum. For in vivo studies, 6–8 week old SCID mice were inoculated with 1×106 Raji cells via tail vein injection and after a period of 72 hours animals were divided into four cohorts. Lenalidomide was administered intraperitoneally (i.p) at 0.5mg/kg/dose on days +3, +4, +8, +9, +13, +14, +18 and +19. IDEC114 was administered via tail vein injection at 10mg/kg/dose on days +5, +10, +15 and +20. Difference in survival between treatment groups was performed by Kaplan-Meier analysis. Results: In vitro exposure of Raji to lenalidomide for five consecutive days enhanced the anti-proliferative effects of IDEC114 when compared to control. In addition, an improvement in IDEC114-associated ADCC was observed in lenalidomide-exposed Raji cells. In vivo treatment of SCID mice with lenalidomide in combination with IDEC114 led to prolongation of survival (44 days) compared to either biological agent alone (p<0.01). Conclusions: Our current research demonstrates that Lenalidomide when added to IDEC114 has augmented in vitro antitumor activity (i.e, antiproliferation and ADCC) and synergistic effects in vivo (i.e., prolongation of survival). We hypothesize and currently are evaluating whether the improvement in in vivo antitumor activity of IDEC114, when combined with Lenalidomide, is secondary to potential changes in the tumor microenvironment and/or IMiD-primed upregulation of NK cells and ADCC. This promising unique combination of biologics warrants evaluation as a clinical trial. (Supported by USPHS grant PO1-CA103985 from the National Cancer Institute.)

No significant financial relationships to disclose.

Lenalidomide (L) induces high response rates with molecular remission in patients (pts) with relapsed (rel) or refractory (ref) chronic lymphocytic leukemia (CLL)

6517

Background: Tumor microenvironment (ME) is critical in CLL pathogenesis. Targeting the ME is a novel approach in CLL therapeutics. Lenalidomide (Revlimid, L) is an immunomodulating agent (IMiD), approved for pts with transfusion-dependent low or intermediate-1 risk myelodysplastic syndrome with deletion 5q cytogenetic abnormality. Its antitumor activity is possibly mediated through (a) downregulation of cytokine(s) - TNF-α, VEGF, PDGF and IL-6 and/or (b) activation of immune effector cells (T & NK cells). We investigated its antitumor activity in rel/ref CLL pts. Here we present the final results of the first cohort of pts treated with 25mg daily dose of L. Methods: Oral L was given at 25mg/day for 21 out of a 28 day cycle. Anti-leukemic effects were recorded after each cycle using NCI-WG 1996 criteria. Treatment was continued until molecular complete response (mCR) or progressive disease (PD). Those with PD were then treated with L in combination with rituximab (reported separately). Polymerase chain reaction (PCR) for immunoglobulin heavy chain gene was used to determine molecular remission (mCR). Results: Twenty-nine pts (median age 64 years; range: 47–75) have been enrolled. Toxicity is reported on all, while response on 19 evaluable pts. Nine pts are inevaluable (2 withdrew consent and 5 received < 2 months of therapy due to toxicity). Major response was noted in 13 of 19 evaluable pts (68%) with 3 CR (2 mCR) and 10 PR. Toxicity: Most common grade 3/4 adverse effects (AE) were neutropenia (60%) and thrombocytopenia (55%). Another common AE was tumor flare (79%); characterized by tender swelling of lymph nodes and/or rash, noted in almost all pts. Conclusions: L at 25mg/day dose given on days 1–21 in a 28 day cycle yields high ORR including mCR in rel/ref CLL. Hematologic toxicity was the most common AE requiring dose reduction. Overall safety profile was predictable and manageable. A slow dose escalation schema, starting at 15mg is being investigated.

[Table: see text]

Rituximab resistance and its association with changes in the internal domain of CD20 antigen and down-regulation of pro-apoptotic protein Bax and Bak in both rituximab-resistant cell lines (RRCL) and diffuse large B-cell lymphoma (DLBCL) patient (pt) samples

17509

Background: Resistance to rituximab (R) has been observed in lymphoma pts. To define the molecular basis for rituximab resistance we developed various RRCL and previously demonstrated changes in CD20 structure, membrane reorganization following rituximab exposure and deregulation of pro-apoptotic proteins Bax/Bak leading to rituximab/chemotherapy resistance. In our current work we evaluated changes in the structure/expression of CD20 and/or pro-apoptotic proteins in primary tumor specimens from DLBCL pts treated with rituximab in combination with CHOP (R-CHOP). Methods: We obtained frozen lymphoid material from patients with DLBCL who achieved a remission (sensitive lymphoma) or failed (resistant lymphoma) R-CHOP therapy. Protein lysates were obtained from each sample. Structural changes in CD20 were determined by Western blotting using various antibodies recognizing epitopes located in the internal (GST77 and 1439) and external domain (rituximab) of CD20. In addition, we studied the expression of Bax and Bak. Results: Variability in the expression and structure of CD20 was found in the pt samples. Rituximab binding to its surface CD20 antigen was preserved in all patients. However, differences in C- and N-terminal expression were found across DLBCL specimens. In addition, down-regulation of Bax/Bak was observed in some pts with resistant lymphomas. Patients who responded to R-CHOP were noted to either have an intact CD20 and/or express Bax/Bak. On the other hand, resistant lymphomas had altered CD20 isoforms and a downregulation of Bax/Bak. Conclusions: Our current preliminary data suggests a positive correlation to our pre-clinical data generated from B-cell NHL cell-lines and will be evaluated in a larger number of primary NHL tumor specimens.

No significant financial relationships to disclose.

Impaired Ca++ mobilization in rituximab-resistant cells (RRCL) is associated with changes in the structure of CD20 antigen, down-regulation of Bax/Bak pro-apoptotic proteins and up-regulation of the endoplasmic reticulum (ER) Ca++ pump protein SERCA-3

2516

Ca++ mobilization leading to apoptosis has been observed following rituximab biding to CD20 in lymphoma cells. Extending rituximab (R) exposure (e.g. as via R maintenance regimens) could potentially accelerate the emergence of resistance to rituximab. To define the molecular basis for rituximab resistance we developed several RRCL and demonstrated changes in CD20 expression/structure and membrane reorganization following rituximab therapy. Specifically, changes in the N-terminal and the C-terminal region of the internal domain of CD20 were observed in RRCL as determined by Western blotting using various antibodies recognizing epitopes located in the internal (GST77 and 1439) and external domain (B1) of CD20. In our current work we evaluated the effects that CD20 structure/expression changes have upon Ca++ mobilization. Extracellular and intracellular Ca++ mobilization was measured by flow cytometric analysis using FLUO-3 AM (acetoxymethyl ester). Optimization of the Ca++ indicator and calibration curves were performed for each cell line. Raji and RRCL were labeled under optimal conditions with FLUO-3 AM/Pluronic Acid F-127. Subsequently, cells were then re-suspended in HANKS media with or without Ca++ and exposed to rituximab or isotype (10μg/ml) ± human serum (25%). Surface CD20 expression was similar between Raji cells and RRCL. Expression of pro- or anti-apoptotic proteins and Ca++ regulatory proteins SERCA3, SERCA2 and Calreticulin was also determined by western blotting. In vitro exposure of Raji cells to rituximab + HS resulted in Ca++ mobilization even in Ca++ depleted media. Notably, Ca++ mobilization was impaired in RRCL when compared to Raji parental cells. In addition, down-regulation of Bax/Bak and up-regulation of SERCA3 was demonstrated in RRCL. Our data suggest that the acquirement of rituximab resistance is associated with changes in the intracellular domain of CD20 and in Ca++ regulator/pro-apoptotic proteins (SERCA3 and Bax/Bak) resulting in a decrease in the intracellular mobilization of Ca++.

No significant financial relationships to disclose.

A prognostic model for prolonged event-free survival after autologous or allogeneic blood or marrow transplantation for relapsed and refractory Hodgkin's disease

There are several prognostic models for Hodgkin's disease (HD) patients, but none evaluating patient characteristics at time of blood and marrow transplantation (BMT). We developed a prognostic model for event-free survival (EFS) post-BMT based on HD patient characteristics measured at the time of autologous (auto) or allogeneic (allo) BMT. Between 1/1991 and 12/2001, 64 relapsed or refractory HD patients received an auto (n=46) or allo (n=18) BMT. A multivariate prognostic model was developed measuring time to relapse, progression or death. Median follow-up was 51.7 months; median EFS for auto and allo BMT was 36 and 3 months, respectively (P=0.001). Significant multivariate predictors of shorter EFS were chemotherapy-resistant disease, KPS <90 and > or =3 chemotherapy regimens pre-BMT. Patients with two to three adverse factors had significantly shorter EFS at 2 years (58 vs 11% in auto; 38 vs 0% in allo BMT patients). Despite a selection bias favoring auto BMT, the model was valid in both auto and allo BMT groups. We were able to differentiate patients at high vs low risk for adverse outcomes post-BMT. This prognostic model may prove useful in predicting patient outcomes and identifying high-risk patients for novel treatment strategies. Validation of this model in a larger cohort of patients is warranted.

Rituximab in Combination With Fludarabine Chemotherapy in Low-Grade or Follicular Lymphoma

Purpose

To evaluate the safety and efficacy of fludarabine plus rituximab in treatment-naïve or relapsed patients with low-grade and/or follicular non-Hodgkin's lymphoma.

Patients and Methods

This was an open-label, single-arm, single-center phase II study enrolling 40 patients. During the first week of the study, patients received two infusions of rituximab 375 mg/m2 administered 4 days apart. Seventy-two hours after the second infusion of rituximab, patients received the first of six cycles of fludarabine chemotherapy (25 mg/m2/d for 5 days on a 28-day cycle). Single infusions of rituximab were administered 72 hours before the second, fourth, and sixth cycles of fludarabine, and two infusions of rituximab were given 4 weeks after the last cycle of fludarabine. Treatment duration was 26 weeks.

Results

An overall response rate of 90% (80% complete response rate) was achieved in the intent-to-treat population. Similar response rates were seen in treatment-naïve and previously treated patients. The median duration of response has not been reached at 40+ months. The median follow-up time in this study is 44 months (range, 15 to 66 months). In patients positive for the 14;18 translocation in blood and/or marrow at enrollment, molecular remission was achieved in 88% of cases, with patients remaining negative for up to 4 years to date. Hematologic toxicity was manageable, and except for a 15% incidence of herpes simplex/zoster infections, infectious complications were rare. Nonhematologic toxicities were minimal.

Conclusion

Rituximab plus fludarabine was well tolerated and associated with an excellent complete response rate, including molecular remissions, in patients with low-grade or follicular lymphoma.

Acute renal failure requiring dialysis after allogeneic blood and marrow transplantation identifies very poor prognosis patients

We examined the incidence, risk factors and associated mortality of acute renal failure requiring dialysis (Renal Bearman Grade [BG] 3) in a 3-year cohort of 97 consecutive allogeneic blood and marrow transplantation (alloBMT) patients. In all, 20 (21%) developed Renal BG3 (all died by day +132) and 77 (79%) developed renal insufficiency (Renal BG1-2). Renal BG3 was a contributing or primary cause of death in 18 (90%) patients who continued to require dialysis at time of death. The two Renal BG3 patients whose deaths were not related to renal failure died on day +103 of hemorrhage and day +132 of underlying disease. By univariate analysis, age, unrelated donor, veno-occlusive disease (VOD) and grade III-IV acute graft-versus-host disease with hepatic involvement were significantly associated with Renal BG3. The multivariate model of time to Renal BG3 determined only a prior diagnosis of severe acute GVHD (RR=4.1, 95% CI 1.6-10.3, P=0.003) and VOD (RR=9.1, 95% CI 3.5-23.7, P<0.001) as significant independent predictors. Renal BG3 is generally considered a conditioning regimen-related toxicity. This study demonstrates that Renal BG3 is most commonly a complication of hepatic co-morbidities after allogeneic blood and marrow transplantation and identifies patients with a very poor prognosis.

Effect of rituximab on peripheral blood stem cell mobilization and engraftment kinetics in non-Hodgkin's lymphoma patients

Rituximab is used for in vivo tumor cell purging for non-Hodgkin's lymphoma (NHL) patients prior to autologous peripheral blood stem cell transplantation (PBSCT). However, its effects on PBSC mobilization and function are poorly understood. We compared the mobilization characteristics and engraftment kinetics of 13 NHL patients receiving and 34 NHL patients not receiving rituximab 6 months before PBSC mobilization. In the rituximab group, there was a significantly longer time to neutrophil engraftment (P=0.0466), a trend toward the need for BM harvest to supplement low-yield PBSC collections (31 vs 9%, P=0.08) and a significantly increased rate of bacteremia episodes (62 vs 26%, P=0.025). Median progression-free survival (PFS) and overall survival (OS) were significantly longer in the rituximab compared to the nonrituximab patients (P=0.049 and 0.042, respectively). However, patients in the nonrituximab group were at high risk for recurrence and expected to have shorter survival. Rituximab used within 6 months prior to collection may have a detrimental effect on PBSC mobilization and engraftment. However, rituximab is a major therapeutic breakthrough for NHL treatment and this negative effect may be offset by improved survival. Further studies are warranted in larger populations to determine the impact of rituximab on engraftment, PFS and OS.

Combination chemotherapy and rituximab

Rituximab is a human-mouse chimeric monoclonal antibody that has demonstrated efficacy against non-Hodgkin's lymphoma (NHL). There is a powerful rationale for combining rituximab treatment with chemotherapeutic agents that have also shown efficacy in NHL, since the mechanisms of action are distinct and there is also evidence that rituximab may sensitize chemoresistant tumor cells to the actions of cytotoxic drugs. A study of rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) chemoimmunotherapy has been carried out in 40 patients with low-grade NHL. In the 35 patients who completed the study, the overall response rate was 100%, with 63% achieving a complete response. Median time to progression has not yet been reached at 47.2+ months. Molecular analysis (polymerase chain reaction) showed that CHOP plus rituximab (unlike CHOP alone) could completely clear blood and bone marrow of cells containing the bcl-2 gene translocation, a molecular marker of NHL cells. Rituximab can therefore add to the efficacy of CHOP without significantly increasing toxicity. A further study is underway to determine whether similar efficacy with less overall toxicity can be achieved using rituximab in combination with fludarabine.

Respiratory syncytial virus infection in the late bone marrow transplant period: report of three cases and review

Respiratory syncytial virus (RSV) infection is an important cause of respiratory mortality in immunosuppressed patients, including bone marrow transplant (BMT) recipients. The presence of lower respiratory tract infection and infection in the pre-engraftment phase of BMT is believed to confer a poor prognosis. Three patients who underwent allogeneic BMT at our institution developed RSV pneumonia over 1 year post BMT, with the underlying disease in remission. All three were hypoxic with extensive pulmonary disease at presentation. Treatment consisted of aerosolized ribavirin and intravenous immune globulin with successful clearing of viral shedding and excellent clinical outcomes. RSV infection is probably less severe in the late post-BMT period, but needs to be considered early in the differential diagnosis of pulmonary infiltrates in this patient population.

Thiotepa-associated cardiomyopathy during blood or marrow transplantation: association with the female sex and cardiac risk factors

Thiotepa (TT) has not been reported to cause cardiomyopathy, whereas cyclophosphamide (Cy)-related cardiomyopathy is well characterized. To search for cases of acute onset cardiomyopathy associated with TT, we retrospectively reviewed 171 patients who received TT-containing conditioning regimens for blood or marrow transplantation (BMT). Nine of 171 patients (5.3%) developed clinical congestive heart failure in the post-BMT period. The median time to onset of heart failure was 15 days after BMT (range 5-30). The median pre-BMT left ventricular ejection fraction (LVEF) was 50% (range 42-65%) as determined by two-dimensional echocardiogram, or gated blood pool scan. At the time of cardiomyopathy onset, LVEF was 30%. Six patients died of causes unrelated to heart failure. All affected patients who developed congestive heart failure following administration of TT had some evidence of cardiac dysfunction prior to transplantation. Significant risk factors for the development of cardiomyopathy included low pre-BMT-LVEF and female sex--particularly in females receiving allogeneic transplantation. The incidence of congestive heart failure with TT-containing regimens was similar to the incidence using other regimens with and without Cy. The mean time to clinical evidence of TT-associated cardiomyopathy was longer than the mean time reported with Cy. We recommend caution in using high-dose TT-containing regimens for patients with histories of cardiac dysfunction.

A phase II multicenter study of CAMPATH-1H antibody in previously treated patients with nonbulky non-Hodgkin's lymphoma

CAMPATH-1H is a humanized antilymphocyte monoclonal antibody (mAb) directed against the CD52 antigen expressed on normal and malignant lymphocytes. We report the results of a multicenter phase II trial using intravenous CAMPATH-1H in previously treated patients with nonbulky non-Hodgkin's lymphoma (NHL) or minimal residual NHL. Sixteen previously treated patients with nonbulky NHL and two patients with minimal residual NHL, were treated with CAMPATH-1H. Changes in peripheral blood lymphocyte subsets were analyzed by multiparameter flow cytometric techniques in eleven patients. The 18 patients enrolled in the studies received CAMPATH-1H for a median duration of 6 weeks (range, 3 to 14 weeks), and a median cumulative dose of 470 mg (range, 180 to 1185 mg). Two of the sixteen patients with nonbulky NHL achieved a complete response (CR) and one patient achieved a partial response (PR). One of the two patients with minimal residual NHL achieved a molecular CR. Infusional complications were seen with the majority of patients but were more common with initial infusions. Significant hematologic toxicity was also observed with grade (3/4) thrombocytopenia (n=10), grade (3/4) neutropenia (n=4) and grade 3 anemia (n=3). Due to excessive infectious complications observed with the patients enrolled, the trials were terminated early. Anti-tumor activity was demonstrated in a small subset of previously treated low-grade lymphoma patients with nonbulky or minimal residual disease. Future studies evaluating the effect of different drug schedules, modes of mAb administration, and concurrent use of prophylactic antibiotics/antiviral/antifungal agents to optimize anti-tumor activity and limit infectious toxicities are planned.

Retrospective multivariate analysis of hepatic veno-occlusive disease after blood or marrow transplantation: possible beneficial use of low molecular weight heparin

This retrospective cohort study of 462 consecutive adult allogeneic and autologous blood or marrow transplantation (BMT) patients compared the incidence of hepatic veno-occlusive disease (VOD) after BMT with three prophylactic regimens. Patients receiving heparin (Hep), heparin + prostaglandin E1 (Hep + PGE1) or low molecular weight heparin (LMWH) as a prophylactic VOD regimen were compared to a historical cohort receiving no VOD prophylaxis. Of 462 BMT patients, VOD was diagnosed in 22% (31 of 142) of the no prophylaxis group, 11% (11 of 104) of the Hep, 12% (13 of 110) in the Hep + PGE1 and 4% (four of 106) of the LMWH group (P = 0.0002). VOD was the primary cause of death in 20% (12 of 59). By multivariate logistic regression, independent risk factors for developing VOD were: no VOD prophylactic regimen, unrelated allogeneic BMT, Karnofsky performance score (KPS) < 80 and aspartate aminotransferase (AST) > or =50 U/l. There was no increase in the rate of death due to hemorrhagic events or VOD in any prophylaxis group compared to the control group. Prospective randomized trials of Hep vs LMWH vs placebo are warranted to assess the efficacy of heparin compounds in the prevention of VOD.

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.

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.

CHOP plus rituximab chemoimmunotherapy of indolent B-cell lymphoma

Indolent (low-grade) B-cell lymphomas are responsive to single-agent and combination chemotherapy agents, but unfortunately possess an incurable, relapsing nature. Novel agents and innovative treatment approaches need to be evaluated in these patients, with the ultimate goals of maintaining good quality of life and prolonging overall survival. Novel combinations of chemotherapeutic agents, monoclonal antibodies (both unlabeled and radiolabeled), and anti-idiotypic vaccine therapies are currently being evaluated. This article reports on the first successful clinical trial combining a chimeric anti-CD20 monoclonal antibody (rituximab; Rituxan, IDEC Pharmaceuticals, San Diego, CA, and Genentech, Inc, San Francisco, CA) with standard-dose combination chemotherapy (ie, cyclophosphamide/doxorubicin/vincristine/prednisone [CHOP]) in the treatment of patients with indolent B-cell lymphoma. A 95% overall response (55%, complete remission; 40%, partial remission) rate using strict definitions for complete remission and extensive staging studies was achieved in a 40-patient intent-to-treat group. In addition, seven of seven patients with follicular histologies achieving complete remission also had clearing of BCL-2 (chromosome 14;18 translocation) positivity from blood and marrow by sensitive polymerase chain reaction assay, suggesting the eradication of subclinical minimal residual disease. Based on its single-agent efficacy, excellent toxicity profile, and ability to be successfully combined with combination chemotherapy (ie, CHOP), rituximab is currently undergoing extensive investigation in a large number of worldwide clinical trials to determine its optimal use in the treatment of CD20-positive neoplasms.

Value of immunophenotype in intensively treated adult acute lymphoblastic leukemia: cancer and leukemia Group B study 8364

The prognostic value of immunophenotype in adult acute lymphoblastic leukemia (ALL) has varied based on the methods used, surface markers studied, and therapy administered. From April 1991 to September 1996, samples of leukemic marrow or blood from 259 eligible and evaluable adult ALL patients entering dose-intensive Cancer and Leukemia Group B (CALGB) front-line treatment protocols were prospectively studied for immunophenotypic classification by multiparameter flow cytometry (MFC) in a central laboratory. A B-lineage (B-LIN) phenotype was expressed in 79% of cases, with one third coexpressing myeloid antigens. A T-lineage (T-LIN) phenotype was expressed in 17% of cases, with one quarter coexpressing myeloid antigens. Since the advent of more intensive CALGB therapy which incorporated cyclophosphamide and the early use of L-asparaginase into the backbone of daunorubicin, vincristine and prednisone, together with central nervous system prophylaxis for adult ALL, no significant differences in response rates, remission duration, or survival have been seen in those patients coexpressing myeloid antigens. The T-LIN phenotype was associated with younger age (P =.01), a higher male to female ratio (P =.01), higher white blood cell count (P =.001) and hemoglobin (P <.001) levels, presence of a mediastinal mass (P <. 001), and longer survival (P =.01) and disease-free survival (DFS) (P =.01) when compared to patients with a B-LIN phenotype. The 3-year probability of survival and DFS (95% confidence interval [CI]) of T-LIN adult ALL was 0.62 (0.46 to 0.76) and 0.62 (0.44 to 0. 77), respectively. Comparatively, the 3-year probability of survival and DFS (95% CI) of B-LIN adult ALL was 0.42 (0.35 to 0.50) and 0.39 (0.31 to 0.47), respectively. The number of T markers expressed in T-LIN ALL cases was shown to have prognostic significance. In particular, patients expressing six or more markers compared with patients expressing three or fewer markers had longer DFS (P =.003) and survival (P =.004). The presence of the Philadelphia chromosome was significantly associated with B-LIN ALL cases which coexpressed CD19(+), CD34(+), and CD10(+) (49%; P =.003), whereas the majority of t(4;11) cases were CD19(+), CD34(+) but CD10(-). The knowledge gained from this study of MFC of a large number of patients will permit a reduction in the number of antigens to be evaluated in future studies. Overall, this should lead to cost savings without loss of valuable information. A rational approach for future studies would be to use four-color flow cytometry (instead of the current three-color) to help further streamline the study of immunophenotype of adult ALL by MFC.

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.