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Biomedical subjects

John C Byrd

Publications and source records attributed to John C Byrd.

70 records · Page 4Linked to original sources
PubMed2003

Lymphodepleting effects and safety of pentostatin for nonmyeloablative allogeneic stem-cell transplantation.

Nonmyeloablative allogeneic stem-cell transplantation (alloNST) is the focus of investigations searching for less-toxic transplantation regimens. We report studies on the kinetics of lymphodepletion and safety of pentostatin (PT) conditioning in alloNST. Patients with hematologic malignancy received mobilized blood from human leukocyte antigen-matched related (n=4) or unrelated (n=8) donors. PT 4 mg/m2 was administered on days -21, -20, and -19 and 200 cGy of total-body irradiation was administered on day -1, followed by cyclosporine A and mycophenolate mofetil. Mononuclear cell adenosine deaminase after PT was inhibited 84%. The absolute CD3+ cells decreased significantly by day -7 (49%) and CD19+ cells declined 92% by day -1. CD4+ cells were depressed more than CD8+ cells. Neutrophils and monocytes were minimally affected by PT. Median posttransplant peripheral blood chimerism on day 70 showed 95% donor leukocytes and 82.5% donor CD3 lymphocytes. PT demonstrated lymphodepleting effects and promising safety, supporting alloNST as early as 7 days after initiation of PT.

Adult↗
PubMed2003

Apoptotic-regulatory and complement-protecting protein expression in chronic lymphocytic leukemia: relationship to in vivo rituximab resistance.

PURPOSE: Rituximab has clinical activity in patients with chronic lymphocytic leukemia (CLL) and has a variety of proposed mechanisms, including apoptosis, complement-dependent cell lysis (CDC), and antibody-dependent cellular cytotoxicity (ADCC). Here we examine pretreatment biologic features that promote resistance to apoptosis and CDC in CLL patients and correlate it with clinical outcome to rituximab-based therapy. PATIENTS AND METHODS: Pretreatment samples from 21 CLL patients treated on a prospective, single-agent rituximab trial were examined for quantitative expression of apoptotic and CDC regulatory proteins, and the level of expression of these proteins was correlated with clinical outcome. RESULTS: Of the 21 patents for whom samples were available, 10 attained a partial response and 11 failed to respond to rituximab therapy. The mean pretreatment expression of Bcl-2, Mcl-1, XIAP, and the ratio of Bcl-2/Bax were higher but not statistically increased in nonresponding patients versus those responding to treatment. In contrast, the pretreatment Mcl-1/Bax ratio was significantly elevated (0.82 +/- 0.28 v 0.39 +/- 0.29, P <.016) in nonresponding patients compared with patients responding to rituximab therapy. Although pretreatment expression of CD55 and CD59 was not associated with response to rituximab therapy, significantly higher levels of CD59 were observed in the CLL cells that were not cleared from the blood at completion of therapy than the level observed at baseline levels (P =.02). CONCLUSION: These data indicate that baseline expression of the Mcl-1/Bax ratio, but not CD55 and CD59, predict for clinical response to rituximab therapy in CLL patients. Further study of disrupted apoptosis in CLL as a potential mechanism of resistance to rituximab appears warranted.

Antibodies, Monoclonal↗
PubMed2003

Depsipeptide (FR901228) induces histone acetylation and inhibition of histone deacetylase in chronic lymphocytic leukemia cells concurrent with activation of caspase 8-mediated apoptosis and down-regulation of c-FLIP protein.

Depsipeptide is in clinical trials for chronic lymphocytic leukemia (CLL) on the basis of earlier observations demonstrating selective in vitro activity in CLL. We sought to determine the relationship of histone H3 and H4 acetylation, inhibition of histone deacetylase, and apoptosis observed in CLL cells to justify a pharmacodynamic end point in these clinical trials. We demonstrate that in vitro depsipeptide induces histone H3 and H4 acetylation and histone deacetylase enzyme inhibition at concentrations corresponding to the LC50 (concentration producing 50% cell death) for cultured CLL cells (0.038 microM depsipeptide). The changes in histone acetylation are lysine specific, involving H4 K5, H4 K12, and H3 K9, and to a lesser extent H4 K8, but not H4 K16 or H3 K14. Depsipeptide-induced apoptosis is caspase dependent, selectively involving the tumor necrosis factor (TNF) receptor (extrinsic pathway) initiating caspase 8 and effector caspase 3. Activation of caspase 8 was accompanied by the down-regulation of cellular FLICE-inhibitory protein (c-FLIP, I-FLICE) without evidence of Fas (CD95) up-regulation. Changes in other apoptotic proteins, including Bcl-2, Bax, Mcl-1, and X-linked inhibitor of apoptosis (XIAP), were not observed. Our results demonstrate a relationship between target enzyme inhibition of histone deacetylase, histone H3 and H4 acetylation, and apoptosis involving the TNF-receptor pathway of apoptosis that is not used by other therapeutic agents in CLL. These data suggest use of histone H3 and H4 acetylation, inhibition of histone deacetylase, and down-regulation of FLIP as pharmacodynamic end points for further evaluation of this drug in patients.

Acetylation↗
PubMed2003

KRN5500: a novel therapeutic agent with in vitro activity against human B-cell chronic lymphocytic leukemia cells mediates cytotoxicity via the intrinsic pathway of apoptosis.

Therapy of B-cell chronic lymphocytic leukemia (CLL) is currently palliative, emphasizing the need for identification of new therapies for this disease. KRN5500 is a novel agent that has a unique sensitivity pattern in the National Cancer Institute cell line screening panel, suggesting a unique mechanism of action. To assess its in vitro activity in CLL, we exposed peripheral mononuclear cells from CLL patients (n = 11) to varying concentrations of this agent. Viability of the CLL cells was reduced by 50% (LC50) at 4 hours, 24 hours, and 4 days at KRN5500 concentrations of 2.50 microM, 0.276 microM, and 0.139 microM, respectively. KRN5500 induced cellular injury via caspase-dependent apoptosis involving the intrinsic mitochondrial (caspase-9) initiating caspase and caspase-3 effector caspase; however, expression of the antiapoptotic mitochondrial membrane protein Bcl-2 was unaffected. These data demonstrate KRN5500 has significant in vitro activity against human CLL cells, thus providing support for introduction of this agent into clinical trials for patients with CLL.

Antineoplastic Agents↗
PubMed2003

Interphase cytogenetic abnormalities in chronic lymphocytic leukemia may predict response to rituximab.

Select cytogenetic abnormalities such as del(17)(p13.1) and del(11)(q22-q23)predict rapid disease progression and inferior survival in chronic lymphocytic leukemia (CLL). We sought to determine the impact of the four most common interphase cytogenetic abnormalities in 28 CLL patients relative to response to three-times-a-week rituximab therapy. Abnormalities were noted in 25 of the 28 patients to include del(13)(q14.3) [n = 16 (57%)], del(11)(q22.3) [n = 10 (36%)], +12 [n = 6 (21%)], del(17)(p13.1) [n = 5 (18%)], and normal [n = 3 (11%)]. Only a minority of each of these occurred as sole abnormalities. To categorize patients into one specific group, we used the hierarchical order del(17)(p13.1) > del(11)(q22.3) > trisomy 12 > del(13)(q14.3) to prioritize. Response to rituximab was noted to vary by cytogenetic group: del(17)(p13.1), 0% [n = 5]; del(11)(q22.3), 66% [n = 9]; del(13)(q14.3), 86% [n = 7]; +12, 25% [n = 4], and normal, 0% [n = 3]. Response was significantly lower (P = 0.05) in patients with del(17)(p13.1) as compared with those with other abnormalities. These data suggest that interphase cytogenetics in CLL may be predictive of a response to rituximab therapy and provide support for additional studies validating risk-adapted therapy in this disease.

Antibodies, Monoclonal↗
PubMed2003

Rituximab in B-cell chronic lymphocytic leukemia.

The monoclonal anti-CD20 antibody rituximab exerts its antitumor activity through a variety of mechanisms, including acting against the cellular defects in apoptosis that give rise to B-chronic lymphocytic leukemia (B-CLL). Phase II clinical studies demonstrated that rituximab, given weekly as a single agent, exhibits significantly less activity in B-CLL than in indolent B-cell lymphomas. Dose escalation, achieved by a thrice-weekly dosing schedule, is necessary for rituximab to effect significant clinical activity as a single agent. A multicenter, prospective, randomized trial demonstrated that concurrent administration with fludarabine improves the complete response (CR) rate. Ongoing clinical studies are examining the use of rituximab in other combination regimens, including FCR (fludarabine, cyclophosphamide, and rituximab), which has shown great promise in a single-center phase II trial. B-CLL patients may experience more infusion toxicity, including tumor lysis syndrome, to rituximab than patients with lymphoma. However, such infusion toxicity is minimized with appropriate premedication and a stepped up dosing schedule, allowing safe and effective use of rituximab in this disease.

Antibodies, Monoclonal↗
PubMed2003

Uniform response criteria in Waldenstrom's macroglobulinemia: consensus panel recommendations from the Second International Workshop on Waldenstrom's Macroglobulinemia.

Waldenstrom's macroglobulinemia (WM) is a malignant disorder of lymphoplasmacytic cells that produce a monoclonal immunoglobulin M (IgM). Since the original description by Jan Waldenström of three patients with symptoms of hyperviscosity due to circulating monoclonal IgM, the definition of WM has been controversial. Standardized criteria for diagnosis have now been proposed, including the presence of any IgM monoclonal protein and marrow and/or nodal lymphoplasmacytic cells. Although previous response criteria have generally incorporated parameters for monoclonal protein reduction and/or improvement of marrow/nodal involvement, specific and uniform response criteria are needed to facilitate comparisons of response, remission duration, progression-free survival, and overall survival in clinical trials similar to those previously established for other diseases such as chronic lymphocytic leukemia, lymphoma, and myeloma. This is of particular importance as new agents are developed and evaluated. This presentation represents consensus recommendations for uniform response criteria for use in assessing responses to treatment for patients with WM, which were prepared in conjunction with the Second International Workshop held in Athens, Greece during September 2002.

Antineoplastic Agents↗
PubMed2003

Advances in the therapy of chronic lymphocytic leukemia.

Chronic lymphocytic leukemia therapy has changed dramatically over the past decade, with recent studies supporting the use of fludarabine as the initial therapy for symptomatic disease. New findings relative to the use of fludarabine and complications arising from this therapy are reviewed. Exciting combination approaches using monoclonal antibodies such as rituximab or Campath-1H in combination with fludarabine offer the opportunity to improve the complete response rate further in chronic lymphocytic leukemia. Furthermore, the field of experimental therapeutics for chronic lymphocytic leukemia was advanced by the description of a new mouse model of human chronic lymphocytic leukemia and identification of several disrupted signal transduction pathways in this disease. The description of therapies that target AKT, protein kinase C, phosphodiesterase 4, mammalian target of rapamycin, histone deacetylase, and methyltransferase offer the opportunity to utilize molecularly targeted therapy for this disease. Such targeted approaches offer hope that we might be on the threshold to changing the natural history of chronic lymphocytic leukemia.

Antineoplastic Agents↗
PubMed2002

Phase 1 and pharmacodynamic studies of G3139, a Bcl-2 antisense oligonucleotide, in combination with chemotherapy in refractory or relapsed acute leukemia.

Overexpression of Bcl-2 is a potential mechanism for chemoresistance in acute leukemia and has been associated with unfavorable clinical outcome. We hypothesized that down-regulation of Bcl-2 would restore chemosensitivity in leukemic cells. To test this hypothesis, we performed a phase 1 study of G3139 (Genasense, Genta, Berkeley Heights, NJ), an 18-mer phosphorothioate Bcl-2 antisense, with fludarabine (FL), cytarabine (ARA-C), and granulocyte colony-stimulating factor (G-CSF) (FLAG) salvage chemotherapy in patients with refractory or relapsed acute leukemia. Twenty patients with refractory or relapsed acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) were enrolled. G3139 was delivered by continuous infusion on days 1 to 10. FLAG chemotherapy was administered on days 5 to 10. Common side effects of this combination included fever, nausea, emesis, electrolyte imbalance, and fluid retention that were not dose limiting. Plasma pharmacokinetics of G3139 demonstrated steady-state concentration (Css) within 24 hours. Of the 20 patients, 9 (45%) had disease response, 6 (5 AML, 1 ALL) with complete remission (CR) and 3 (2 AML and 1 ALL) with no evidence of disease but failure to recover normal neutrophil and/or platelet counts or to remain in remission for at least 30 days (incomplete remission). Bcl-2 mRNA levels were down-regulated in 9 of the 12 (75%) evaluable patients. This study demonstrates that G3139 can be administered safely with FLAG chemotherapy and down-regulate its target, Bcl-2. The encouraging clinical and laboratory results justify the current plans for a phase 3 study in previously untreated high-risk AML (ie, age at least 60 years).

Acute Disease↗
PubMed2002

Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse, and overall survival in adult patients with de novo acute myeloid leukemia: results from Cancer and Leukemia Group B (CALGB 8461).

We analyzed prospectively 1213 adults with de novo acute myeloid leukemia (AML) to ascertain the prognostic impact of cytogenetic abnormalities on complete remission (CR) rate, 5-year cumulative incidence of relapse (CIR), and 5-year overall survival (OS). All patients received similar induction therapy. Median follow-up for surviving patients was 8.3 years. Nonprioritized cytogenetics distinguished t(8;21) and inv(16)/t(16;16) as conferring a significantly better prognosis than normal karyotype. Prognostic impact of many abnormalities could not be determined independently because of their association with complex karyotype. Neither complex karyotype nor secondary aberrations affected outcome of patients with t(8;21), inv(16)/t(16;16), or t(9;11). Among other patients, those with complex karyotypes had significantly worse outcomes than cytogenetically normal patients. Based on outcome for specific cytogenetic abnormalities and karyotype complexity, patients were divided into 3 risk groups: favorable (CR 88%, CIR 54%, OS 55%), intermediate (CR 67%, CIR 67%, OS 24%), and adverse (CR 32%, CIR 92%, OS 5%). Multivariate analyses confirmed the major contribution of cytogenetics to the probability of attaining CR, CIR, and OS. For the adverse-risk group, the probability of achieving CR was 4.0 and 11.9 times lower, the probability of relapse 3.0 and 4.4 times higher, and the risk of death 2.1 and 4.3 times higher than those for the intermediate and favorable groups, respectively. We conclude that although the prognostic impact of many recurring abnormalities has not been ascertained independently of complex karyotype, cytogenetics is among the most useful factors predicting attainment of CR, CIR, and long-term survival in adult AML.

Acute Disease↗
PubMed2002

Randomized phase 2 study of fludarabine with concurrent versus sequential treatment with rituximab in symptomatic, untreated patients with B-cell chronic lymphocytic leukemia: results from Cancer and Leukemia Group B 9712 (CALGB 9712).

Recent studies have suggested that rituximab has clinical activity and modulates antiapoptotic proteins associated with drug resistance in chronic lymphocytic leukemia (CLL). We performed a randomized phase 2 study to determine the efficacy, safety, and optimal administration schedule of rituximab with fludarabine in previously untreated CLL patients. Patients were randomized to receive either 6 monthly courses of fludarabine concurrently with rituximab followed 2 months later by 4 weekly doses of rituximab for consolidation therapy or sequential fludarabine alone followed 2 months later by rituximab consolidation therapy. A total of 104 patients were randomized to the concurrent (n = 51) and sequential (n = 53) regimens. During the induction portion of treatment, patients receiving the concurrent regimen experienced more grade 3 or 4 neutropenia (74% versus 41%) and grade 3 or 4 infusion-related toxicity (20% versus 0%) as compared with the sequential arm. The consolidation rituximab therapy was tolerated well in both arms. All other toxicities were similar in the 2 arms. The overall response rate with the concurrent regimen was 90% (47% complete response [CR], 43% partial response [PR]; 95% confidence interval [CI], 0.82-0.98) compared with 77% (28% CR, 49% PR; 95% CI, 0.66-0.99) with the sequential regimen. With a median follow-up time of 23 months, the median response duration and survival have not been reached for either regimen. Rituximab administered concurrently with fludarabine in previously untreated CLL patients demonstrates marked clinical efficacy and acceptable toxicity. Phase 3 studies using this combination approach for patients with CLL are warranted.

Adult↗
PubMed2002

Frequency and type of serious infections in fludarabine-refractory B-cell chronic lymphocytic leukemia and small lymphocytic lymphoma: implications for clinical trials in this patient population.

BACKGROUND: Treatments for fludarabine-refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) are limited. Most new therapies being examined in fludarabine-refractory patients have shown a high frequency of serious infection. Little data exist regarding the frequency of infections in this population treated with noninvestigational best supportive care therapies. METHODS: The infectious courses of 27 patients with fludarabine-refractory CLL/SLL were retrospectively reviewed. Fludarabine-refractoriness was defined as either relapse within six months of completion of or failure to respond to fludarabine treatment. Infections were documented after patients met National Cancer Institute criteria for further treatment. Serious infections were defined as infections mandating admission to the hospital for intravenous antibiotics. RESULTS: Patient characteristics included: median age 67 years (range, 40-83), median 3 chemotherapy treatments (range, 1-8), and hypogammaglobulinemia in 73% of patients. Pneumocystis carinii prophylaxis was given to 89% of patients. Serious infections developed in 24 out of 27 patients (89%). Patients had a median of 2 admissions (range, 0-11) for serious infection occurring at a median of 4 months (range, 0-21) from onset of fludarabine-refractoriness. The median frequency of admission for infection was 0.17 per month. Most common sites for infection in decreasing frequency were: respiratory tract, urinary tract, blood/sepsis, and soft tissues. Bacteria caused 69 out of 88 infections (78.4%); viruses (varicella-zoster and herpes simplex) caused 11 out of 88 (12.5%); fungi caused 4 out of 88 (4.5%); and opportunistic infections caused 4 out of 88 (4.5%). Median survival was 13.0 months (range, 1-44+). CONCLUSIONS: The frequency of serious infections in patients with fludarabine-refractory CLL/SLL is high. These findings are relevant to trials with new and highly effective agents for which the incidence of serious infections after treatment might otherwise appear to be prohibitively high.

Adult↗
PubMed2002

The mechanism of tumor cell clearance by rituximab in vivo in patients with B-cell chronic lymphocytic leukemia: evidence of caspase activation and apoptosis induction.

Rituximab is a chimeric monoclonal antibody directed at CD20 with significant activity in non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL). A variety of pathways of tumor cytotoxicity different from cytotoxic chemotherapy have been proposed for this therapeutic antibody including antibody-dependent cellular cytotoxicity and complement-mediated cell lysis. This report describes that a proportion of patients with CLL receiving rituximab treatment have in vivo activation of caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP) cleavage in blood leukemia cells immediately following infusion of rituximab. This suggests that apoptosis using a pathway similar to fludarabine and other chemotherapeutic agents is intricately involved in the blood elimination of tumor cells after rituximab treatment. Patients having caspase-3 activation and PARP cleavage in vivo had a significantly lower blood leukemia cell count after treatment as compared to those without caspase activation. Significant down-modulation of the antiapoptotic proteins XIAP and Mcl-1 was also noted, possibly explaining in part how rituximab sensitizes CLL cells to the cytotoxic effect of chemotherapy in vivo. These findings suggest that the therapeutic benefit of antibody-based therapy in vivo for patients with CLL depends in part on induction of apoptosis and provides another area of focus for studying mechanisms of antibody-resistance in neoplastic cells.

Antibodies, Monoclonal↗
PubMed2002

Chronic lymphocytic leukemia.

This update of early stage B-cell chronic lymphocytic leukemia (B-CLL) embraces current information on the diagnosis, biology, and intervention required to more fully develop algorithms for management of this disease. Emphasis on early stage is based on the rapid advancement in our understanding of the disease parameters and our increasing ability to predict for a given early stage patient whether there is a need for more aggressive management. In Section I, Dr. Terry Hamblin addresses the nature of the disease, accurate diagnostic procedures, evidence for an early "preclinical" phase, the use of newer prognostic features to distinguish who will be likely to progress or not, and whether it is best to watch or treat early stage disease. In Section II, Dr. Neil Kay and colleagues address the biologic aspects of the disease and how they may relate to disease progression. Review of the newer insights into gene expression, recurring genetic defects, role of cytokines/autocrine pathways, and the interaction of the CLL B cell with the microenvironment are emphasized. The relationship of these events to both trigger disease progression and as opportunities for future therapeutic intervention even in early stage disease is also considered. In Section III, Dr. John Byrd and colleagues review the historical and now current approaches to management of the previously untreated progressive B-CLL patient. They discuss what decision tree could be used in the initial decision to treat a given patient. The use of single agents versus newer combination approaches such as chemoimmunotherapy are discussed here. In addition, the place of marrow transplant and some of the newer antibodies available for treatment of B-CLL are considered. Finally, a challenge to utilize our growing knowledge of the biology of B-CLL in the early stage B-CLL is proffered.

Antineoplastic Agents↗
PubMed2002

Fludarabine-related pulmonary toxicity: a distinct clinical entity in chronic lymphoproliferative syndromes.

BACKGROUND: Little is known about lung injury caused by fludarabine therapy. OBJECTIVES: To establish a case definition, to describe management, and to identify risk factors for fludarabine-related pulmonary toxicity. DESIGN: Case-control study. SETTING: Tertiary-care US Army teaching hospital. PATIENTS: Individuals treated with fludarabine at our institution between January 1989 and June 2000. MEASUREMENTS: Cases of fludarabine-related pulmonary toxicity were defined as follows: dyspnea, fever, hypoxemia, and radiographic infiltrates seen in a patient treated with fludarabine; cases were excluded if there was evidence of pulmonary infection or progression of underlying lymphoproliferative disease affecting the lungs. For each case, demographic data, medical history, radiographic information, available bronchoscopy and pathology data, and details of treatment were reviewed. Cases were compared with fludarabine-treated control subjects to identify potential risk factors. Comparisons were made with regard to age, gender, history of underlying lung disease, lymphoproliferative diagnosis, prior chemotherapy, fludarabine treatment regimen, and pretreatment chest radiograph. RESULTS: During the study period, 105 patients were treated with fludarabine. The incidence of fludarabine-related pulmonary toxicity using our definition was 8.6% (95% confidence interval [CI], 3.2 to 13.9%). One patient died before this entity was suspected; the remainder of the patients underwent bronchoscopy to exclude infection. Patients were treated with corticosteroids with subjective and objective benefits. One patient later died of apparent infection during steroid therapy. One patient was retreated with fludarabine and symptoms of lung toxicity developed again. Patients (n = 9) were similar to control subjects (n = 96) with respect to age, gender, history of underlying lung disease, previous chemotherapy, and fludarabine regimen. Patients with chronic lymphocytic leukemia were 13.3 (95% CI, 1.6 to 300.6) times more likely to have toxicity develop than patients treated with fludarabine for other diagnoses. There was a trend toward an increased incidence in patients with interstitial infiltrates apparent on prefludarabine chest radiographs. CONCLUSIONS: A variety of lung conditions arise in patients treated with fludarabine; however, this agent seems to cause direct pulmonary toxicity. After performing an appropriate evaluation to exclude infection, corticosteroids are an effective therapy. The relative frequency of this condition and potential for mortality underscore the need for increased clinician awareness of fludarabine-related pulmonary toxicity and its risk factors.

Aged↗