In Vitro Studies
We investigated the effects of dexamethasone and IL-1Ra on stromal cell IL-6 production and myeloma cell apoptosis using an in vitro myeloma cell/stromal cell coculture assay. Control vector-transduced, IL-1β-negative KAS-6/1 cells were cocultured with stromal cells and dexamethasone (10 μM), IL-1Ra (1 μg/mL), or both (or, for controls, with neither) for 48 hours, and the percentage of apoptotic cells was quantified by flow cytometry (). Results in are expressed as the percent increase in apoptotic cells above levels in control cultures without drugs. The numbers in pg/mL represent the amount of IL-6 generated in the cocultures of myeloma and stromal cells. Because the KAS-6/1 cells are IL-1β negative, very little paracrine IL-6 was generated (6885 pg/mL). Addition of IL-1Ra alone had little effect on IL-6 production and was unable to induce apoptosis. However, administration of dexamethasone alone induced substantial apoptosis (64%) above control, and this increased apoptosis was minimally enhanced with the addition of IL-1Ra (73%). However, no detectable levels of IL-1β were found in these cultures, and therefore they are not representative of the myeloma microenvironment. When IL-1β-transduced KAS-6/1 cells were cocultured with stromal cells, large amounts of IL-6 (267,921 pg/mL) were generated. In this situation, dexamethasone decreased IL-6 production but caused no change in apoptosis above control. The large amount of remaining paracrine IL-6 (77,725 pg/mL) was sufficient to completely inhibit dexamethasone-induced apoptosis. Alone, IL-1Ra was unable to induce apoptosis, but it was more efficient than dexamethasone at inhibiting paracrine IL-6 production, thereby returning levels to the vector control baseline. When both agents were administered, dexamethasone was again able to increase apoptosis substantially (25%) in the presence of IL-1Ra, thereby inhibiting paracrine IL-6 production (38 pg/mL). These in vitro results suggest that IL-1Ra alone does not induce apoptosis; however, its ability to inhibit paracrine IL-6 production is superior to that of dexamethasone at the concentrations tested. Furthermore, the combination of IL-1Ra and dexamethasone appear to complement each other in the inhibition of IL-6 production and induction of myeloma cell apoptosis.
FIGURE 1. Effects of an interleukin 1 receptor antagonist (IL-1Ra) and dexamethasone on myeloma cell apoptosis and interleukin 6 (IL-6) production in myeloma cell-stromal cell cocultures. Normal stromal cells (1 × 105 cells/mL) were cocultured directly (more ...)
Phase 2 Clinical Trial
On the basis of these preclinical findings, we conducted a phase 2 clinical trial in patients with SMM or IMM to determine the biologic activity of IL-1Ra and dexamethasone and to assess their potential toxicity and their effect on PFS in patients with SMM or IMM. Because IL-1β induces paracrine IL-6, we hypothesized that IL-1Ra would inhibit IL-6 production and myeloma cell growth. Patients were deemed eligible for the study if they had 10% or more bone marrow plasma cells and/or an IgG or IgA M-spike of 3 g/dL or greater and did not require immediate chemotherapy. Patients received subcutaneous administrations of 100 mg/d of IL-1Ra for 6 months. If they showed signs of clinical improvement (ie, reduction in M-protein levels), they continued receiving IL-1Ra alone. However, if their disease was stable after 6 months of IL-1Ra or if they had clinical features worrisome for progression (ie, rising M-protein levels), they began receiving low-dose dexamethasone (20 mg/wk) in conjunction with the IL-1Ra. As a surrogate for IL-6 production, hs-CRP levels were monitored. Forty-seven patients were included for analysis on the basis of intent to treat at diagnosis.
The characteristics of the study patients are summarized in . Of the 47 patients, 34 had SMM and 13 had IMM with lytic bone disease. Almost all patients (46/47) had 10% or more bone marrow plasma cells, and 85% generated IL-1 levels (IL-6 FI) consistent with myeloma (≥1).
Characteristics of 47 Study Patientsa
IL-1Ra Alone Inhibits Paracrine IL-6 Production and Myeloma Cell Growth. When administered alone, IL-1Ra appeared to target the proliferative myeloma fraction, resulting in a decrease in the PCLI (a measure of the myeloma cell proliferative rate). As shown in , 7 patients with a baseline PCLI greater than zero who were treated with IL-1Ra alone had a 75% to 100% reduction from their baseline PCLI value after 6 months of therapy. The change in the PCLI paralleled a decrease in hs-CRP levels in all cases (33%-90% decrease; ). Although an attempt was made to measure IL-6 levels, they were found to be too low in most patients to be reproducible, and the hs-CRP was judged to be more informative. These findings suggest that IL-1Ra inhibited IL-6 production in the myeloma microenvironment, as evidenced by a reduction in hs-CRP levels, resulting in suppression of myeloma cell proliferation. Notably, proliferation was suppressed independently of a reduction in M-protein production.
Effect of IL-1Ra Alone on PCLI, hs-CRP Levels, and M-spikea
Induction of a Chronic Disease State in Patients at High Risk of Active Myeloma. In our phase 2 clinical trial, we combined IL-1Ra with low-dose dexamethasone
on the basis of our in vitro findings that IL-1Ra inhibits paracrine IL-6 production and dexamethasone decreases IL-1β levels through myeloma cell apoptosis. Data for 2 representative patients treated with combined IL-1Ra and low-dose dexamethasone therapy are provided in . One patient (, left) had worsening anemia and an increasing IgG level during the 2 years before participation in this clinical trial. After 6 months of IL-1Ra alone, the patient's PCLI decreased from 0.8% to 0%, and his hs-CRP level decreased from 0.89 to 0.58 mg/L (to convert to nmol/L, multiply by 9.524).
FIGURE 2. Clinical effects of the combination of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) and low-dose dexamethasone. Left, This patient received IL-1Ra alone at month 0 and the combination of IL-1Ra and low-dose dexamethasone at month 6. Right, This patient (more ...)
At 6 months, when dexamethasone was added to the IL-1Ra, the M-spike and percentage of bone marrow plasma cells decreased while hemoglobin levels returned to normal (, left). The osteolytic lesions in the right radius of this patient have remained stable, as evidenced by findings on positron emission tomography and bone survey. He continues to be asymptomatic with stable disease after 4.5 years of participation in this trial.
The other patient (, right), who was anemic when enrolled in the study, had 45% bone marrow plasma cells and an elevated PCLI (0.8%). The IgG levels continued
to increase, and dexamethasone was added after 4.5 months. Response to the combined treatment was noted 1.5 months after addition of low-dose dexamethasone. Both the PCLI and hs-CRP levels decreased at 6 months (, right) and have remained low on combination therapy. Levels of IgG decreased by 65%, and hemoglobin increased to near normal levels. The patient remains asymptomatic and stable after more than 3 years of therapy.
Serial IL-1 levels were determined by coculturing supernatants harvested from unsorted patient bone marrow cells with normal stromal cells and measuring IL-6 production (IL-6 FI), as previously described.14
Levels of IL-1 (IL-6 FI) of 1.0 or more were consistent with active/progressive myeloma, and values less than 1.0 were typical of MGUS.14
For the patient described in , left, the IL-1 levels at baseline (1.3) and at 6-month follow-up (1.8) remained stable while he was taking IL-1Ra alone. However, after dexamethasone was added, the IL-1 levels decreased to 0.11 at 1 year and remained low (0.44) at 18 months. Because dexamethasone therapy was initiated at month 4.5, the effect of IL-1Ra alone on IL-1 levels cannot be determined for the patient described in , right; however, like the patient described in , left, this patient's IL-1 levels decreased while receiving combination therapy, from 4.8 to 1.5. In summary, serial measurements showed that dexamethasone, but not IL-1Ra, can lower IL-1 levels.
All 47 patients received IL-1Ra initially; 25 (53%) of 47 patients subsequently received combined IL-1Ra and dexamethasone therapy. The median follow-up was 40 months. The overall PFS was 37.5 months (95% confidence interval, 9.6-~). In the clinical trial, 3 patients achieved an MR to IL-1Ra alone; 5 patients achieved a PR and 4 patients an MR after addition of dexamethasone.
Eight patients have now maintained a chronic disease state for more than 4 years while receiving therapy. One of these patients had an initial high PCLI of 1.2% and an increasing M-protein level. He was the only patient enrolled in the study with less than 10% bone marrow plasma cells but an M-spike of 3 g/dL or greater. His disease continues to be controlled by IL-1Ra alone. Disease control has also been achieved in other patients with less than 20% bone marrow plasma cells by IL-1Ra alone. Another patient with an exceptionally high PCLI of 6.4% has remained stable while receiving combined IL-1Ra and dexamethasone therapy for more than 4 years.
Reduction in Baseline hs-CRP Levels Predicts Stability of Disease. In addition to clinical outcomes, we also evaluated changes in other correlative markers from baseline to 6 months. Because hs-CRP levels are often used as a surrogate marker for IL-6 levels, we investigated whether hs-CRP levels can be used to identify patients who can maintain stable disease while receiving this treatment. Statistical analysis using a partitioning algorithm showed that the median PFS for patients without (n=12) or with (n=35) a greater than 15% decrease in 6-month vs baseline levels of hs-CRP was 6 months and more than 3 years, respectively (P=.002) (, left). Disease progression was more likely in patients with IMM. Of the 35 patients with a decrease in hs-CRP levels, 20% presented with IMM, whereas 50% of the 12 patients without a decrease in hs-CRP levels had IMM. Stability of the M protein also distinguished the 2 groups. The median PFS for patients with (n=19) and without (n=28) a 5% or greater increase in 6-month vs baseline M-protein levels was 6 months and more than 3 years, respectively (P<.0001) (, right).
FIGURE 3. Progression-free survival (PFS). Left, The median PFS for patients without (n=12) and with (n=35) a decrease at 6 mo of greater than 15% from the baseline hs-CRP level was 6 mo and more than 3 y, respectively (P=.002). Right, The median PFS for patients (more ...)
Toxicity of Therapy. Injection site reactions (ISRs) from the IL-1Ra were the most common side effects, occurring in 86% of patients. Two patients were withdrawn from the study because of ISRs in the first months of treatment. Grade 4 adverse events occurred in 5 patients, and grade 3 adverse events occurred in 16. The most common grade 3 to 4 toxicity was asymptomatic neutropenia (8 patients) due to the IL-1Ra; this toxicity was managed by decreasing the IL-1Ra dosage to every other day. Thrombosis was infrequent in this trial, occurring in only 3 patients (6%). Two patients (4%) developed grade 4 infections (pneumonias), and 5 (11%) experienced grade 3 infections. In patients with infections requiring antibiotics, IL-1Ra and dexamethasone were withheld until the illness resolved. Two patients (4%) developed a grade 3 increase in creatinine level. Other potentially dexamethasone-related toxicities were colon perforation (1 patient), myocardial infarction (1 patient), and cataracts (2 patients). Four patients ended active treatment because of adverse events (2 from ISRs within the first month of therapy). No grade 5 events were reported.