In vitro studies of ways to overcome resistance to VAMP--high dose melphalan in the treatment of multiple myeloma

Pharmacokinetics of High-Dose Propylene Glycol-Free Melphalan in Multiple Myeloma Patients Undergoing Autologous Hematopoietic Cell Transplantation

High-dose melphalan followed by autologous stem cell transplant (ASCT) is standard of care for eligible patients with multiple myeloma (MM). Evomela (propylene glycol-free melphalan HCl [PG-Free Mel]; Spectrum Pharmaceuticals, Irvine, CA) was approved by the US Food and Drug Administration as conditioning therapy for ASCT in MM in 2 daily 100-mg/m² doses for a total dose of 200 mg/m². In this phase II, open-label study PG-Free Mel (Evomela) conditioning was given at single dose of 200 mg/m² on day -2 pre-ASCT to establish pharmacokinetic (PK) parameters and safety. Twenty-four patients (median age, 64 years) were enrolled between August 2016 and February 2017. Myeloablation followed by successful neutrophil engraftment occurred at a median of 10 days in all patients. Peak melphalan concentration was observed at 10 minutes after infusion, whereas there was considerable variation in the maximum plasma concentration (C_max) and area under concentration time curve (AUC). Median C_max was 7380 ng/mL (interquartile range [IQR], 6522 to 8027). Similarly, median AUC was 533,552 ng/mL∙min (IQR, 450,850 to 662,936). PG-Free Mel had an acceptable safety profile regardless of the exposure, with no mortality and an overall response rate of 96% and a very good partial response rate of 75%. In conclusion, although PG-Free Mel at a single dose of 200 mg/m² was safe, considerable PK variability was observed with the highest quartile having an ~3-fold higher AUC than the first quartile, suggesting that strategies for higher targeted exposure could be explored in future trials to optimize clinical benefit.

Dose escalation therapy in previously untreated patients with multiple myeloma following Z-Dex induction treatment

A phase I-II study of high-dose (HD) alkylating agents in newly diagnosed patients with multiple myeloma after maximum response to Z-Dex (idarubicin, dexamethasone) therapy and DHAP (cisplatin, HD cytosine arabinoside, dexamethasone), stem cell mobilization is reported. Twenty-six patients, median age 56 years (range 42-66), completed Z-Dex chemotherapy and peripheral blood stem cells (PBSC) were mobilized with DHAP. Patients then preceded to cyclophosphamide (HD Cy: 6 g/m(2)) with granulocyte colony-stimulating factor followed by busulphan-melphalan-conditioned PBSC autograft. Interferon alpha was introduced at 3 months post transplant as maintenance therapy. Six patients failed to complete the full protocol. Median time from diagnosis to transplantation was 8 months (range 6-12). Mean CD34+ cell dose collected was 15.8 x 10(6)/kg (CI 11.8, 19.8). Median time from DHAP to HD-Cy was 6 weeks (range 4-12) and from HD-Cy to transplant was 8 weeks (range 6-12). The median follow-up was 36 months (range 6-63). On an intent-to-treat basis, the response rates were three complete response (CR, 12%), 21 partial response (PR, 80%) and two stable disease (SD, 8%) post Z-Dex, five CR (19%) and 21 PR (81%) post HD-Cy, and 14 CR (54%) and 12 PR (46%) post transplant. The treatment-related mortality (TRM) was 4% (1 patient). Median overall survival (OS) and progression-free survival (PFS) have not been reached; estimated values were 60 and 48 months respectively. The 3-year OS and PFS were 72% and 62%. Actuarial 5-year OS and event-free survival were 49% and 32%. DHAP produces effective PBSC mobilization and sequential HD therapy, including autologous PBSCT, in patients who received Z-Dex; this offers significant durable disease response rates with acceptable TRM.

Some early phase II trials in previously untreated multiple myeloma: The Royal Marsden experience

Multiple myeloma is at a stage today where acute leukemia was in the 1960s and 1970s when the aim was to attain complete remission (CR), which would translate into prolonged overall survival (OS) and a cure. The Royal Marsden group was the first to establish a dose-response effect for melphalan leading to CR in patients with myeloma. Since then, different strategies have been developed to improve the results of high-dose therapy, including alternating conditioning regimens, peripheral blood stem cells (PBSC) as a source of stem cells, purging techniques to decrease graft contamination by the myeloma cell, increased dose intensity by means of tandem transplants, and finally, allogeneic matched or unmatched stem cell transplantation. Components of treatment offered at Royal Marsden since 1980 are upfront high-dose melphalan (HDM) 140 mg/m(2), induction infusional chemotherapy followed by consolidation with HDM with autotransplantation, and maintenance with interferon-alpha2b (IFN) (collectively termed sequential therapy). Each of these components has shown benefits in selected studies and together they have dramatically improved the outlook for patients with myeloma.

Busulfan and melphalan as conditioning regimen for autologous peripheral blood stem cell transplantation in multiple myeloma

Twenty-four patients with multiple myeloma (MM), three (12.5%) in complete remission (CR) and 21 (87.5%) in partial remission (PR) were treated with high-dose chemotherapy (HDCT) (busulfan 12 mg/kg+melphalan 140 mg/m2) as preparative regimen for autologous peripheral blood stem cell (PBSC) transplantation. These cells were previously collected by leukapheresis after mobilization by high-dose cyclophosphamide (HD Cy)+rhGM-CSF (18 patients) or rhG-CSF alone (six patients). Considering 23 evaluable patients following HDCT, the CR rate was 58% (14 patients) and the PR rate was 38% (nine patients). One transplant-related death occurred following this regimen (4%). With a median follow-up of 20 months (range 4-34) after transplantation, 21 patients are alive (87%). Disease progression after transplantation was observed in four patients. Overall and relapse-free actuarial survival at 24 months was 91% and 74%, respectively. 12 patients (50%) remain in CR 15 months (4-34) post transplant. The major toxicity was mucositis. Busulfan+melphalan is a safe and feasible conditioning regimen for APBSCT in MM with acceptable toxicity and a high objective response rate, which may result in prolonged survival.

Refractory and relapsing multiple myeloma treated by blood stem cell transplantation

Between June 1989 and June 1992, 12 patients with advanced multiple myeloma underwent peripheral blood stem cell autotransplantation after high-dose chemotherapy and radiotherapy. The conditioning regimen included melphalan (140 mg/m2), high-dose cyclophosphamide (120 mg/kg), methylprednisolone (2 g daily x 7), and total body irradiation (9-12 Gy). Transplant morbidity included severe mucositis (n = 7) and acute renal failure (n = 2) related to infusion of the stem cells. Engraftment was delayed (n = 4) in this heavily pretreated population, and two patients had complete graft failure. Despite the advanced nature and chemotherapy-refractory state of their disease, 11 of 11 evaluable patients achieved an objective response. Six patients survived to leave the hospital, and four remain alive--one died of acute leukemia induced by prior melphalan exposure. Three of the four are relapse-free at a median of 24.9 months (range, 18-28 months). Some patients with advanced refractory multiple myeloma can achieve objective responses from highdose chemoradiotherapy with peripheral blood stem cell rescue. Harvesting peripheral blood stem cells from high-risk patients early in their disease for later use may decrease the risk of graft failure. Peripheral blood stem cell transplantation after high-dose chemotherapy and total body irradiation can produce durable responses in patients with advanced refractory myeloma.

Interleukin-6 is a cofactor for the growth of myeloid cells from human bone marrow aspirates but does not affect the clonogenicity of myeloma cells in vitro

Several groups have claimed that IL-6 is a growth factor for human myeloma cells in vitro. Bone marrow aspirates from 30 patients at different stages of treatment with VAMP/high dose melphalan, were examined for myeloma colony formation (MY-CFUc) using a clonogenic assay in vitro. Myeloma cells from 16/30 patients produced MY-CFUc in our assay system, which uses heavily irradiated HL60 cells as an underlay in soft agar. These heavily irradiated cells were shown to be essential for the inhibition of granulocyte-macrophage colonies (GM-CFUc). The addition of recombinant human IL-6 (10 ng/plate) reduced the number of bone marrow samples which produced MY-CFUc from 16 to six. Furthermore, the addition of antibody to IL-6 (1 microgram/plate) failed to inhibit MY-CFUc from 6/7 samples. Conditioned medium from human peripheral blood mononuclear cells (PBMC-CM) contains approximately 2 ng/ml IL-6 and can be used to stimulate the growth and maintenance of the B9 murine IL-6 dependent hybridoma cell line. Recombinant human IL-6 supported the growth of B9 cells in a clonogenic assay and growth was inhibited by anti-IL-6 in the presence of rhIL-6 or PBMC-CM. Mononuclear cells from a second group of myeloma patients were cultured in soft agar in a mixture of PBMC-CM and fresh growth medium. Nine of the 10 samples produced myeloid colonies which consisted of granulocytes, monocytes and macrophages and the number of colonies was reduced by at least 50% in 6/8 samples when anti-IL-6 was added to the cultures. In no instance were MY-CFUc produced. Also, conditioned medium from the bladder carcinoma cell line 5637, which is used routinely as a source of granulocyte-macrophage colony stimulating factor (GM-CSF), contains approximately 4 ng/ml IL-6. Although rhIL-6 failed to stimulate GM-CFUc in the absence of other growth factors, addition of anti-IL-6 to cultures containing a suboptimal amount of 5637-CM reduced the number of colonies by 50%. These data provide evidence that IL-6 is a cofactor for the growth of myeloid precursors but does not affect the proliferation of human myeloma cells in vitro.

Decrease in clonogenic tumour cells in bone marrow aspirates from multiple myeloma patients due to the incorporation of cyclophosphamide into treatment with vincristine, adriamycin and methyl prednisolone

A study of 32 patients receiving cyclophosphamide (CY) and verapamil (VER) in addition to the drug combination vincristine, adriamycin and methyl prednisolone (VAMP) was made in which the clinical response and growth of clonogenic myeloma cells (MY-CFUc) from bone marrow aspirates were compared. At presentation, MY-CFUc were grown from 72 per cent (23/32) of the patients. After treatment with CY-VAMP or VERCY-VAMP, MY-CFUc were grown from 25 per cent (8/32) of patients of whom only 50 per cent responded clinically. The overall clinical response rate for patients receiving CY-VAMP and VERCY-VAMP was 64 per cent (9/14) and 72 per cent (13/18) respectively of whom 14 per cent in each group achieved complete remission. There was no concomitant increase in normal tissue toxicity as measured by granulocyte-macrophage colony (GM-CFUc) formation. Comparison of these data with our previous study of patients receiving VAMP alone, suggests that the addition of CY to the regimen may increase the tumour cell kill. Further clinical studies will determine whether there is a significant increase in the complete remission rate.

Colony stimulating activity in the serum of patients with multiple myeloma is enhanced by interleukin 3: a possible role for interleukin 3 after high dose melphalan and autologous bone marrow transplantation for multiple myeloma

Sera from 36/37 multiple myeloma patients and 19/21 sera from patients with other solid or liquid tumours had granulocyte-macrophage colony stimulating activity (CSA) towards normal human donor bone marrow whereas 1/16 sera from normal donors had this activity. Unlike human rhGM-CSF and GM-CSF from 5637 (human bladder cell line) conditioned medium which is heat stable, CSA from serum is heat labile (56 degrees C/30 min). In multiple myeloma patients, CSA was detectable more than 2 years after treatment with 'high dose melphalan. Although multiple myeloma patients, at relapse, have sufficient CSA in their serum to produce maximal stimulation of GM-CFUc from normal donor bone marrow in vitro, their own GM population responds poorly. The results suggest that the failure of patients own bone marrow to respond to endogenous CSA may be due to damage to the stem cells of the marrow or the failure of precursor cells to respond to CSA. Addition of rhIL-3 to myelomatous serum increased the number of GM-CFUc from both normal and myelomatous bone marrow but did not stimulate the growth of MY-CFUc significantly. The results suggest that rhIL-3 may assist bone marrow recovery in multiple myeloma patients after intensive chemotherapy.

Evidence that multiple myeloma may be regulated by homeostatic control mechanisms: correlation of changes in the number of clonogenic myeloma cells in vitro with clinical response

Myeloma colonies (MY-CFUc) could be grown in vitro for 6 months (median time) after a group of 12 myeloma patients had reached complete remission (CR). In a second group of 25 patients MY-CFUc increased in 17/25 and GM-CFUc in 20/25 patients after cyclophosphamide even though 24/25 patients had a partial response to VAMP and one was in CR. These data suggest that cell killing by cyclophosphamide stimulates residual tumour cells into proliferation and adds further support to the idea that myeloma is under some degree of homeostatic control which may be analogous to that in normal bone marrow. Although lymphoplasmacytoid myeloma cells may be more drug resistant than plasmacytoid myeloma cells in vitro, it was not possible to conclude that the emergence of lymphoplasmacytoid cells at relapse was indicative of resistance to further treatment.

Increase in clonogenic tumour cells in bone marrow of patients with multiple myeloma treated with vincristine, doxorubicin, and methylprednisolone

The relation between clonogenic myeloma cells, assayed in vitro, and clinical status was studied in 20 patients with multiple myeloma before and after VAMP therapy (vincristine, doxorubicin, and methylprednisolone). 14 patients showed an improvement in clinical status, as judged by a fall in myeloma protein and a decrease in plasmacytoid myeloma cell infiltration in the bone marrow. However, in 11 of these 14, there was an increase in the number of clonogenic myeloma cells. This suggests that the treatment changed the myeloma cell population in the residual bone marrow. To be effective, subsequent chemotherapy should be aimed at destroying this population of myeloma cells.