Role of gamma globulin for immunoprophylaxis in multiple myeloma

Recommendations on prevention of infections during chimeric antigen receptor T-cell and bispecific antibody therapy in multiple myeloma

Chimeric antigen receptor T (CAR T) cell and bispecific antibody therapies have shown unprecedented efficacy in heavily pretreated patients with multiple myeloma (MM). However, their use is associated with a significant risk of severe infections, which can be attributed to various factors such as hypogammaglobulinemia, neutropenia, lymphopenia, T-cell exhaustion, cytokine-release syndrome and immune-effector cell-associated neurotoxicity syndrome. As these therapies have been recently approved by regulatory agencies, it is crucial to establish practical guidelines for infection monitoring and prevention until robust data from prospective clinical trials become available. To address this issue, a panel of experienced investigators from the Academic Consortium to Overcome Multiple Myeloma through Innovative Trials (COMMIT) developed consensus recommendations for mitigating infections associated with CAR T-cell and bispecific antibody therapies in MM patients.

Multiple Myeloma: What Do We Do About Immunodeficiency?

Multiple myeloma (MM) is an incurable hematological malignancy. Immunodeficiency results in the incapability of immunity to eradicate both tumor cells and pathogens. Immunotherapies along with antibiotics and other anti-infectious agents are applied as substitutes for immunity in MM. Immunotherapies including monoclonal antibodies, immune checkpoints inhibitors, affinity- enhanced T cells, chimeric antigen receptor T cells and dendritic cell vaccines are revolutionizing MM treatment. By suppressing the pro-inflammatory milieu and pathogens, prophylactic and therapeutic antibiotics represent anti-tumor and anti-infection properties. It is expected that deeper understanding of infection, immunity and tumor physio-pathologies in MM will accelerate the optimization of combined therapies, thus improving prognosis in MM.

Management of infectious complications in multiple myeloma patients: Expert panel consensus-based recommendations

The introduction of new therapeutic agents in multiple myeloma (MM), including proteasome inhibitors, immunoregulatory drugs and monoclonal antibodies, has improved the outcomes of patients, but in parallel has changed the frequency and epidemiology of infections. Hence, the great strides in the indications and use of new active treatments for MM need parallel progresses on the best approach to prophylaxis and supportive therapy for infections. Moving from the recognition that the above issue represents an unmet clinical need in MM, an expert panel assessed the scientific literature and composed a framework of recommendations for optimal infection control in patients candidate to active treatment for MM. The present publication represents a consensus document from questionnaires and consensus meetings held during 2017. The issues tackled in the project dealt with: infectious risk assessment, risk management and prophylaxis, intravenous immunoglobulin replacement therapy, antiviral and antibacterial vaccination. Considering the lack of conclusive and/or enough large studies for certain topics several recommendations derived from the personal experience of the experts.

European Myeloma Network guidelines for the management of multiple myeloma-related complications

The European Myeloma Network provides recommendations for the management of the most common complications of multiple myeloma. Whole body low-dose computed tomography is more sensitive than conventional radiography in depicting osteolytic disease and thus we recommend it as the novel standard for the detection of lytic lesions in myeloma (grade 1A). Myeloma patients with adequate renal function and bone disease at diagnosis should be treated with zoledronic acid or pamidronate (grade 1A). Symptomatic patients without lytic lesions on conventional radiography can be treated with zoledronic acid (grade 1B), but its advantage is not clear for patients with no bone involvement on computed tomography or magnetic resonance imaging. In asymptomatic myeloma, bisphosphonates are not recommended (grade 1A). Zoledronic acid should be given continuously, but it is not clear if patients who achieve at least a very good partial response benefit from its continuous use (grade 1B). Treatment with erythropoietic-stimulating agents may be initiated in patients with persistent symptomatic anemia (hemoglobin <10g/dL) in whom other causes of anemia have been excluded (grade 1B). Erythropoietic agents should be stopped after 6-8 weeks if no adequate hemoglobin response is achieved. For renal impairment, bortezomib-based regimens are the current standard of care (grade 1A). For the management of treatment-induced peripheral neuropathy, drug modification is needed (grade 1C). Vaccination against influenza is recommended; vaccination against streptococcus pneumonia and hemophilus influenza is appropriate, but efficacy is not guaranteed due to suboptimal immune response (grade 1C). Prophylactic aciclovir (or valacyclovir) is recommended for patients receiving proteasome inhibitors, autologous or allogeneic transplantation (grade 1A).

Infections in patients with leukemia and lymphoma

Infectious complications remain a significant issue in the care of patients with hematologic malignancies. Inherent immune defects related to the primary disease process are present in patients with disorders such as chronic lymphocytic leukemia, multiple myeloma, hairy cell leukemia, and Hodgkin lymphoma. Therapy-related immunosuppression is also commonplace in these patients. This includes not only treatment-related neutropenia, but also defects in cell-mediated immunity, such as those that occur with purine analog therapy. In this chapter, we will review the pathogenesis of infection in these disorders, as well as the spectrum of infectious complications seen and suggested strategies for the prevention of infection.

Oral antibiotic prophylaxis of early infection in multiple myeloma: a URCC/ECOG randomized phase III study

Multiple myeloma (MM) is a malignancy of clonal plasma cells, resulting in an increased production of ineffective immunoglobulins with suppression of non-involved immunoglobulins. Patients with MM are at increased risk of infectious complications, particularly streptococcal and staphylococcal infections. This study evaluated the impact of prophylactic antibiotics on the incidence of serious bacterial infections (SBIs) during the first 2 months of treatment in patients with newly diagnosed MM. Patients with MM receiving initial chemotherapy were randomized on a 1:1:1 basis to daily ciprofloxacin (C; 500 mg twice daily), trimethoprim-sulfamethoxazole (T; DS twice daily) or observation (O) and evaluated for SBI (Eastern Cooperative Oncology Group ≥grade 3) for the first 2 months of treatment. From July 1998 to January 2008, 212 MM patients were randomized to C (n=69), T (n=76) or O (n=67). The incidence of SBI was comparable among groups: C=12.5%, T=6.8% and O=15.9%; P=0.218. Further, any infection during the first 2 months was also comparable (20% vs 23% vs 22%, respectively, P=0.954). We demonstrate that prophylactic antibiotics did not decrease the incidence of SBI (≥grade 3) within the first 2 months of treatment. We conclude that routine use of prophylactic antibiotics should not be mandated for patients receiving induction chemotherapy.

Immunoglobulin prophylaxis in hematopoietic stem cell transplantation: systematic review and meta-analysis

PURPOSE

Because the role of immunoglobulins (IVIG) prophylaxis in patients undergoing hematopoietic stem-cell transplantation (HSCT) has not been established in terms of survival and infection prevention, we conducted a meta-analysis evaluating these issues.

METHODS

Systematic review and meta-analysis of randomized-controlled trials comparing prophylaxis with polyvalent IVIG or cytomegalovirus (CMV)-IVIG and control or another preparation or dose. PUBMED, Cochrane Library, LILACS, and conference proceedings were searched. Two reviewers appraised the quality of trials and extracted data. Relative risks (RRs) with 95% CIs were estimated and pooled.

RESULTS

Thirty trials including 4,223 patients undergoing bone marrow transplantation (BMT) were included. There was no difference in all-cause mortality when polyvalent IVIG or CMV-IVIG was compared to control (RR, 0.99; 95% CI, 0.88 to 1.12; and RR, 0.86; 95% CI, 0.63 to 1.16, respectively). There was no difference in clinically documented infections when polyvalent IVIG was compared with control (RR, 1.00; 95% CI, 0.90 to 1.10; five trials). CMV infections were not significantly reduced with either polyvalent IVIG or CMV-IVIG. Interstitial pneumonitis was reduced with polyvalent IVIG in older studies but not in the more recent ones, nor in studies assessing CMV-IVIG. Polyvalent IVIG increased the risk for veno-occlusive disease (RR, 2.73; (95% CI, 1.11 to 6.71). Graft-versus-host disease was not affected.

CONCLUSION

Because there is no advantage in terms of survival or infection prevention, IVIG does not have a role in HSCT.

Immunoglobulin prophylaxis in hematological malignancies and hematopoietic stem cell transplantation

BACKGROUND

Patients undergoing hematopoietic stem cell transplantation (HSCT) and those with lymphoproliferative disorders (LPD) have a higher incidence of infections due to secondary hypogammaglobulinemia. One approach is the prophylactic administration of intravenous immunoglobulins (IVIG). Randomized controlled trials (RCTs) showed conflicting results in terms of type, schedule, dose and hematological patients benefiting from IVIG. We therefore performed a systematic review and meta-analysis to evaluate the role of IVIG in these patients.

OBJECTIVES

To determine whether prophylaxis with IVIG reduces mortality or affects other outcomes in patients with hematological malignancies.

SEARCH STRATEGY

PubMed (January 1966 to December 2007), CENTRAL (The Cochrane Library, up to 2007, issue 1), LILACS and conference proceedings published between 2002-2007 were searched. The terms "immunoglobulins" or "gammaglobulins" or specific gammaglobulins and similar and the terms "hematologic neoplasms" or "hematologic malignancies" or "transplant" or "autotransplant" or "allotransplant" or "bone marrow transplant" or "peripheral stem cell transplant" and similar were selected. References of all included trials and reviews identified were scanned for additional trials.

SELECTION CRITERIA

All RCTs comparing prophylaxis of IVIG with placebo, no treatment or another immunoglobulin preparation, different administration schedules or doses for patients with hematological malignancies were included. One author screened all abstracts identified through the search strategy and two reviewers independently inspected each reference identified by the search and applied inclusion criteria.

DATA COLLECTION AND ANALYSIS

For each trial, results were expressed as relative risks (RR) with 95% confidence intervals (CI) for dichotomous data and weighted mean differences for continuous data. We conducted meta-analysis, where enough similar trials were available, using the fixed- effects model, unless significant heterogeneity was present. We performed sensitivity analyses to assess the effect of individual methodological quality measures on effect estimates, including allocation generation, concealment and blinding.

MAIN RESULTS

Forty trials were included: thirty included HSCT patients and ten included patients LPD. When polyvalent immunoglobulins or hyperimmune cytomegalovirus (CMV)-IVIG was compared to control for HSCT, there was no difference in all-cause mortality. Polyvalent immunoglobulins significantly reduced the risk for interstitial pneumonitis but increased the risk for veno-occlusive disease and adverse events. In LPD, no benefit in terms of mortality IVIG could be demonstrated but there was a decrease in clinically and microbiologically documented infections.

AUTHORS' CONCLUSIONS

In patients undergoing HSCT, routine prophylaxis with IVIG is not supported. Its use may be considered in LPD patients with hypogammaglobulinemia and recurrent infections, for reduction of clinically documented infections.

Complications of multiple myeloma

Multiple myeloma, also known as myeloma or plasma cell myeloma, is a progressive hematologic disease. Complications of multiple myeloma include renal insufficiency, hematologic complications (anemia, bone marrow failure, bleeding disorders), infections, bone complications (pathologic fractures, spinal cord compression, hyercalcemia), and neurologic complications (spinal cord and nerve root compression, intracranial plasmacytomas, leptomeningeal involvement, among others). This article reviews these various complications connected to multiple myeloma, examining their various causes and possible treatment.

Immunodeficiency and immunotherapy in multiple myeloma

Multiple myeloma is a malignant tumour of plasma cells that remains incurable for the vast majority of patients, with a median survival of 2-3 years. It is characterized by the patchy accumulation of tumour cells within bone marrow leading to variable anaemia, bone destruction, hypercalcaemia, renal failure and infections. Immune dysfunction is an important feature of the disease and leads to infections that are both a major cause of morbidity and mortality and may promote tumour growth and resistance to chemotherapy. Numerous defects of the immune system have been described in multiple myeloma although the relative clinical importance of these remains elusive. There has been considerable interest in the identification of an autologous response against myeloma. Although T cells and humoral responses directed against myeloma-associated antigens have been described, it is uncertain if the immune system plays a role in preventing or controlling myeloma cell growth. There is increasing interest in the potential role of immunotherapy but the success of these interventions is likely to be modified by the immunologically hostile environment associated with multiple myeloma. This review attempts to summarize the current knowledge relating to the immune defects found in multiple myeloma.

Early mortality after diagnosis of multiple myeloma: analysis of patients entered onto the United kingdom Medical Research Council trials between 1980 and 2002--Medical Research Council Adult Leukaemia Working Party

PURPOSE

Early mortality in multiple myeloma (MM) is usually attributed to combined effects of active disease and comorbid factors. We have studied early deaths in a series of large multicenter trials to assess direct causes of death, their predictability, and whether current management strategies have reduced their frequency.

PATIENTS AND METHODS

A total of 3,107 newly diagnosed patients entered onto United Kingdom Medical Research Council MM trials from 1980 to 2002 were studied. Trial files, final clinical summaries, and postmortem reports were analyzed.

RESULTS

Death within 60 days of trial entry occurred in 299 patients (10%). Logistic regression modeling identified beta 2-microglobulin, performance status, and age as the most important predictors of early death, but only with 61% sensitivity and 73% specificity. Forty-five percent of deaths were attributable to infection, which was often associated with bone pain (particularly thoracic pain) and delay in presenting to medical care. Neutropenia was present at diagnosis in only 11 of the 135 deaths from infection. Renal failure was present in 28% of early deaths and was linked to light-chain MM, hypercalcemia, dehydration, and nonsteroidal anti-inflammatory drugs. There was no time related reduction in the percentage or nature of early deaths in 1,550 patients older than 65 years receiving similar therapy between 1982 and 2002.

CONCLUSION

A tenth of patients die within 60 days of diagnosis of MM. Infection and renal failure are the main direct causes of early mortality, which cannot be accurately predicted by presenting prognostic features. All patients should be considered at high risk of death during induction therapy.

Host immunologic augmentation for the control of infection

The emergence of resistance to pharmacologic antimicrobial agents and the desire to increase chemotherapy dose-intensity have necessitated the search for alternative means to control infectious disease. Enhancement of host immunity against infection has been permitted through the use of hematopoietic growth factors, which can shorten the duration of neutropenia and reduce the risk for bacterial and fungal infections. Hematopoietic growth factor-mobilized hematopoietic stem cells have also proven to be highly efficacious in permitting high-dose chemotherapy. Interferons, immunoregulatory cytokines, immune globulins, and immune lymphocytes also hold promise to enhance host immunity and reduce susceptibility for serious infectious morbidity.

Prophylactic antibiotics for the prevention of early infection in multiple myeloma

PURPOSE

Patients with multiple myeloma are at increased risk for bacterial infection. During the first 2 months of initial chemotherapy the rate of infection is twice that experienced during the remainder of the disease course. As many as one-third of these early infections are fatal, and many more prevent adequate administration of chemotherapy. This study was designed to determine whether the morbidity and mortality of early infection can be prevented by prophylactic administration of trimethoprim-sulfamethoxazole (TMP-SMX).

PATIENTS AND METHODS

Eligible patients about to begin chemotherapy for multiple myeloma were randomly assigned to prophylaxis for 2 months or to no prophylaxis (control). Antibiotic prophylaxis consisted of TMP-SMX 160/800 mg orally every 12 hours administered for the first 2 months of initial chemotherapy. All patients were observed for infection for 3 months after the start of chemotherapy.

RESULTS

Of 57 patients entered into the study, 54 were evaluable, representing 13.1 patient-years of observation. The 28 TMP-SMX patients and 26 control patients were comparable in terms of chemotherapy regimen, age, gender, stage, and bone marrow function. Bacterial infection during the 3-month study period occurred in 11 control patients but in only 2 patients assigned TMP-SMX (P = 0.004). Eight severe infections occurred in controls compared with 1 in a TMP-SMX patient (P = 0.010) leading to 4 and 1 infection deaths, respectively (P = not significant). Severe infections included 5 pneumonias (3 with sepsis), 2 urinary tract infections with complicating pneumonia or sepsis, 1 diverticulitis with perforation, and 1 staphylococcal scalded skin syndrome. None of the 4 nonbacterial infections was severe. The rate of bacterial infection was 2.43 per patient-year for controls and 0.29 per patient-year for the TMP-SMX group (P = 0.001). Toxicity (skin rash 6 patients, nausea 1 patient) was not life-threatening but required discontinuation of TMP-SMX in 25% of patients.

CONCLUSION

Administering TMP-SMX for the first 2 months of initial chemotherapy is effective, inexpensive prophylaxis for early bacterial infection in multiple myeloma.

Complement abnormalities in multiple myeloma

PURPOSE

Patients with multiple myeloma have been shown to have defective opsonization and C3 deposition. Previous studies have suggested that defective C3 deposition may be related to a failure of C3 activation in myeloma serum, the mechanism of which is unknown. We therefore decided to investigate the underlying mechanism responsible for the failure in C3 activation and deposition.

PATIENTS AND METHODS

The study consisted of 10 patients from whom a total of 12 serum specimens were obtained. Normal serum was prepared from a pool of serum specimens in four healthy male donors. We evaluated, in vitro, the kinetics of C3 deposition onto zymosan using radiolabeled C3 under various conditions. We also measured the serum levels of a variety of complement components using standard methods.

RESULTS

Five of 10 patients' sera demonstrated poor C3 deposition onto zymosan at all time points, whereas an additional two showed poor C3 deposition at early time points but a rebound to normal by 30 minutes. Multiple components of the classical and alternative complement pathways were decreased in many patients, with the most striking abnormalities occurring in those with the poorest C3 deposition. No single complement component abnormality was found to be common to the group. Elevations in Bb fragment concentration strongly suggest in vivo activation as the likely mechanism for depletion of alternative pathway components; the mechanism for classical pathway abnormalities is less clear. There was an inverse correlation between paraprotein concentration and abnormal C3 deposition (p less than 0.0001) and C3 (p less than 0.0005) and C4 (p less than 0.0001) concentrations. However, no consistent evidence of fluid-phase complement consumption was present.

CONCLUSION

The defect in C3 activation and deposition in multiple myeloma cannot be explained on the basis of a single complement component abnormality but rather is due to a heterogeneous group of complement abnormalities. Although no correlation between in vitro abnormalities and clinical status was identified in this small group of patients, it is likely that the described complement defects play an important role in defective host defense in multiple myeloma.

Phase I study of intravenous gamma globulin in multiple myeloma

Seventeen patients with multiple myeloma were given intravenous immunoglobulin at doses ranging from 150 mg/kg to 500 mg/kg in a phase I study. The intravenous immunoglobulin was well tolerated with only three transient episodes of mild clinical toxicity during 27 infusions. In no instance was hepatic or renal toxicity seen. Marked biologic variability over the one month study period in total IgG levels in patients with non-IgG myeloma and IgG subclasses in many of the patients was observed, making intravenous immunoglobulin half-life determinations based on IgG or IgG subclass levels problematical. The decay of functional antibody to hepatitis B surface antigen was determined. Analysis of the hepatitis antibody data suggested that intravenous immunoglobulin half-life was in the range of seven to 20 days for the entire study group and was not related to the isotype of the myeloma paraprotein or to the baseline levels of IgG. No infections were observed in the study group during the study period, but the potential for infection prophylaxis by intravenous immunoglobulin in myeloma patients must be evaluated in a randomized, prospective, controlled phase III study.

Influence of treatment and response status on infection risk in multiple myeloma

The clinical course of 60 patients with multiple myeloma was examined for risk factors associated with infection. The overall incidence of infusion was 1.46 per patient-year. The greatest risk period for the occurrence of infection was the first two months after the start of initial chemotherapy. The incidence of infection during this period was 4.68 infections per patient-year compared with 1.04 infections per patient-year for subsequent months. Serum creatinine levels of 2 mg/dl or more (p less than 0.03) and decreased polyclonal serum immunoglobulins (p less than 0.01) predicted increased risk of early infections. Patients infected during the first two months of initial chemotherapy had the same rate of infection during the subsequent clinical course as did patients free of infection during the early treatment period. Thus, the early risk period does not represent only the attrition of susceptible patients. Patients who achieved an objective response had a decrease in infection risk during the time of the response (0.44 infections per patient-year). While response to chemotherapy prolongs life in multiple myeloma, the initiation of chemotherapy is associated with a definable risk period for infections.

Polyvalent pneumococcal immunization of patients with plasma cell dyscrasias

Thirteen patients with plasma cell dyscrasias and 27 healthy adults were immunized with polyvalent pneumococcal vaccine. Antibody responses were determined by radioimmunoassay. Patients with plasma cell disorders had significantly lower preimmunization and postimmunization antibody titers compared with those of the controls (P-0.01 abd 0.008, respectively). Even though the overall response in myeloma patients was poor, occasional rises in antibody titers occurred. Immunizing myeloma patients with the pneumococcal vaccine is recommended.

Multiple myeloma: current concepts in diagnosis and management

The basic pathologic process in multiple myeloma is the neoplastic proliferation of a single clone of plasma cells. Although the events which trigger autonomous cell growth are not well understood, the secretion of an M component, a serum or urinary immunoglobulin molecule or a light chain fragment by the vast majority of myeloma cells has provided a biologic marker which has greatly facilitated the study of this disease Some of the more recent clinical concepts which have evolved from studies on the plasma cell and the immunoglobulin molecule are discussed.

Light chain isotype-associated suppression of normal plasma cell numbers in patients with multiple myeloma: Medical Research Council's Working Party for Leukaemia in Adults and the Oxford Lymphoma Group

The number of plasma cells in the lamina propria of the gut has been assessed in patients with multiple myeloma and other B-cell neoplasms. The total number of these plasma cells was reduced in most patients with myelomatosis and one-third of patients with lymphoplasmacytoid tumours. This reduction was not, however, seen in patients with other neoplasms of B-cell origin, although hypogammaglobulinaemia was common to all groups of patients. The depletion of gut plasma cell numbers was not uniform in myelomatosis patients. They showed selective loss of plasma cells with the same light chain isotype as that produced by the neoplastic clone.

Phagocytes and C4 in paraproteinaemia

Immunological studies were performed on patients with multiple myeloma. A defect in polymorphonuclear leucocyte (PMN) function as evidenced by diminished adherence of these cells to nylon fibre columns was detected in 16, and low levels of the fourth component of complement (C4) were observed in 14, of the 26 patients studied. Twelve of the patients with low C4 exhibited the defect in PMN adhesiveness whereas only four of the 12 patients with normal C4 showed the defect. The PMN defect was not caused solely by the low C4, since PMNs from seven patients with hereditary angioedema, which is associated with low levels of C4, did not show the defect. The low C4 and defect in PMN adhesiveness occurred primarily in patients with IgG myeloma; all but one of the patients with IgA myeloma, macroglobulinaemia, or light chain disease were normal in both parameters. Results of skin window studies indicated that patients with the PMN defect also had a defect in the early PMN inflammatory response. The defect in PMN adhesiveness could be completely corrected by incubating the cells in normal plasma. Binding of the C4 to paraprotein could not be demonstrated, and C1 activation was found to be caused only by one of 10 isolated paraproteins studied. These studies indicate that patients with paraproteinaemia have immunological abnormalities in addition to low immunoglobulin levels and suggest that these abnormalities may be involved in the pathogenesis of the recurrent infections commonly associated with this disease.

Immunologic Aspects of the Hematologic Neoplasms

Understanding the pathogenesis and pathophysiology of the hematologic malignancies now requires knowledge of their immunology. Many of these tumors appear to arise from the immune cells themselves (B or T cell tumors); most have associated disturbances in immune cell function. New immunodiagnostic methods may become potentially useful clinical tools for evaluating extent of disease, tumor cell kinetics, response to treatment, and prognosis.

Kinetics of tumor growth and regression in IgG multiple myeloma

Studies of immunoglobulin synthesis, total body tumor cell number, and tumor kinetics were carried out in a series of patients with IgG multiple myeloma. The changes in tumor size associated with tumor growth or with regression were underestimated when the concentration of serum M-component was used as the sole index of tumor mass. Calculation of the total body M-component synthetic rate (corrected for concentration-dependent changes in IgG metabolism) and tumor cell number gave a more accurate and predictable estimate of changes in tumor size. Tumor growth and drug-induced tumor regression were found to follow Gompertzian kinetics, with progressive retardation of the rate of change of tumor size in both of these circumstances. This retardation effect, describable with a constant alpha, may be caused by a shift in the proportion of tumor cells in the proliferative cycle. Drug sensitivity of the tumor could be described quantitatively with a calculation of B(O), the tumor's initial sensitivity to a given drug regimen. Of particular clinical significance, the magnitude of a given patient's tumor regression could be predicted from the ratio of B(O) to alpha. Mathematical proof was obtained that the retardation constant determined during tumor regression also applied to the earlier period of tumor growth, and this constant was used to reconstruct the preclinical history of disease. In the average patient, fewer than 5 yr elapse from the initial tumor cell doubling to its clinical presentation with from 10(11) to more than 10(12) myeloma cells in the body. The reduction in total body tumor mass in most patients responding to therapy ranges from less than one to almost two orders of magnitude. Application of predictive kinetic analysis to the design of sequential drug regimens may lead to further improvement in the treatment of multiple myeloma and other tumors with similar growth characteristics.