Drug Insight: thalidomide as a treatment for multiple myeloma

Internal ribosome entry site of bFGF is the target of thalidomide for IMiDs development in multiple myeloma

Although new analogues of immunomodulatory drugs (IMiDs) are being developed for MM, the molecular mechanism of these drugs remains unclear. In the current study, we used MM cell lines as a model to investigate the molecular mechanism of thalidomide and to compare its potency with IMiDs such as pomalidomide. We determined that thalidomide did not inhibit cell proliferation of RPMI8226 and U266 MM cells, whereas pomalidomide showed a significant inhibitory effect on these two MM cell lines. Interestingly, we further demonstrated that although thalidomide down-regulated bFGF translation through the inhibition of IRES even at 0.1 μg/ml, pomalidomide did not have a similar affect bFGF levels. A colony formation assay demonstrated that thalidomide and the bFGF knock-down clones caused a significant reduction in the clonogenic ability of MM cells, and treatment with exogenous bFGF can recover the clonogenic ability of thalidomide-treated cells and knock-down clones, but not that of pomalidomide-treated cells. This implies that thalidomide, but not pomalidomide, targets the IRES of FGF-2.

In conclusion, our results highlight a non-cytotoxic anticancer drug target for thalidomide, the IRES of bFGF, and provide the mechanistic rationale for developing IMiDs as anti-cancer therapeutics in MM patients, with improved potency and fewer side effects.

Myeloma in scar tissue--an underreported phenomenon or an emerging entity in the novel agents' era? A single center series

Tumor relapse in scar tissue is uncommon in cancer patients. Likewise, extramedullary plasmacytoma (EMP) relapse in scar tissue in the setting of multiple myeloma (MM) has been rarely reported. We report a series of 3 patients whose disease progressed as EMP at the site of a wound from previous invasive procedures. All 3 patients were treated for the relapsed disease with different treatment modalities, but failed to respond adequately and died several months after relapse. At original MM diagnosis, all had advanced-stage disease. They were treated with novel agents with or without autologous hematopoietic stem cell transplantation and achieved either a complete or very good partial response. We suggest that these treatments, which have become the standard of care in MM, may permit a predominance of myeloma subclones which are independent of the bone marrow microenvironment. These myeloma subclones then gain a survival advantage in the active scar-tissue niche, allowing for their uncontrolled proliferation. This case series might represent an underreported phenomenon and therefore may indicate an emerging and difficult-to-treat disease in the era of targeted therapies in MM. Physicians treating MM should be aware of this phenomenon, especially when referring their patients for invasive procedures.

Emerging biological insights and novel treatment strategies in multiple myeloma

INTRODUCTION

Survival in multiple myeloma (MM) has improved significantly in the past 10 years due to new treatments, such as thalidomide and lenalidomide (immunomodulatory drugs or IMiDs) bortezomib and advances in supportive care. Nevertheless, almost all MM patients show disease relapse and develop drug resistance.

AREAS COVERED

The authors review the therapeutic approach for untreated MM patients. Furthermore, the prognostic stratification of patients and the proposed risk-adapted strategy are discussed. Finally, preclinical and clinical data regarding newer antimyeloma agents, currently undergoing examination such as proteasome inhibitors (PIs, carfilzomib), IMiDs (pomalidomide), epigenetic agents (histone deacetylase inhibitors vorinostat and panobinostat), humanized monoclonal antibodies (elotuzumab and MOR03087) and targeted therapies (inhibitors of NF-κB, MAPK, HSP90 and AKT) are reported.

EXPERT OPINION

MM patient outcome has remarkably improved due to the use of three to four drug combination therapies including PIs and IMiDs, which target the tumor in its bone marrow microenvironment, however MM treatment remains challenging. The use of high-throughput techniques has allowed to discover new insights into MM biology. The identification of candidate therapeutic targets and availability of respective investigative agents will allow for a substantial progress in the development and implementation of personalized medicine in MM.

Concise asymmetric synthesis of configurationally stable 4-trifluoromethyl thalidomide

BACKGROUND

Thalidomide is one of the promising multidimensional drugs that possess high activity against serious diseases such as rheumatoid arthritis, Crohn's disease, leprosy, AIDS and various cancers. However, its medicinal applications are plagued by its configurational instability, as it easily undergoes racemization under the physiological conditions (t(1/2) = 8 h at pH 7.1, 37°C in water). Consequently, the design and synthesis of configurationally stable analogs of thalidomide continue to be an important area of research in bioorganic and medicinal chemistry.

DISCUSSION

4-trifuoromethyl thalidomide-3c was identified as an important synthetic target, which was expected to be a configurationally stable analog of thalidomide. Synthetic challenges in preparation of compound 3c were truly multipronged, considering the unique steric, electronic as well as electrostatic characteristics of trifluoromethyl group, significantly affecting properties of parent amino acids. After numerous experiments and unsuccessful attempts, both (3S,4R) and (3R, 4S) enantiomers of 4-trifluoromethyl-substituted thalidomide were effectively synthesized in six steps starting from enantio- and diastereomerically pure 3-(trifluoromethyl)pyroglutamates, prepared by highly diastereoselective Michael addition reactions between achiral glycine equivalents and chiral 3-(trifluoromethyl)acrylate.

CONCLUSION

We have developed a reliable asymmetric approach for preparation of hitherto unknown 4-trifluoromethyl-substituted thalidomide in (3S,4R) and (3R,4S) enantiomerically pure forms. These thalidomide derivatives were shown to be configurationally stable and therefore may serve as useful lead compounds for the development of a new generation of thalidomide-based pharmaceuticals.

Thalidomide decreases gelatinase production by malignant B lymphoid cell lines through disruption of multiple integrin-mediated signaling pathways

BACKGROUND

Thalidomide and its analogs are effective agents in the treatment of multiple myeloma. Since gelatinases (matrix metalloproteinases-2 and -9) play a crucial role in tumor progression, we explored the effect of thalidomide on gelatinase production by malignant B lymphoid cell lines.

DESIGN AND METHODS

We investigated the effect of therapeutic doses of thalidomide on integrin-mediated production of gelatinases by malignant B lymphoid cell lines by gelatin zymography, western-blot, reverse transcriptase polymerase chain reaction and invasive capacity through Matrigel-coated Boyden chambers. We also explored the effect of thalidomide on the activation status of the main signaling pathways involved in this process.

RESULTS

Thalidomide strongly inhibited gelatinase production by B-cell lines and primary myeloma cells in response to fibronectin, the most efficient gelatinase inducer identified in lymphoid cells. Thalidomide disrupted integrin-mediated signaling pathways involved in gelatinase induction and release, such as Src and MAP-kinase ERK activation, resulting in decreased cell motility and invasiveness. Unexpectedly, treatment with thalidomide elicited an increase in fibronectin-induced Akt phosphorylation through phosphoinositide 3-kinase-independent pathways since thalidomide decreased fibronectin-induced phosphoinositide 3-kinase phosphorylation and reversed the inhibition of Akt phosphorylation achieved by the phosphoinositide 3-kinase inhibitors wortmannin and LY294002.

CONCLUSIONS

Disruption of integrin-mediated signaling may be an important mechanism through which thalidomide and its analogs impair tumor cell interactions with the microenvironment. The unexpected effects of thalidomide on Akt activation indicate the need for further studies to elucidate whether the interference with Akt downstream effects would synergize with the anti-tumor activity of thalidomide.

Thalidomide in multiple myeloma--clinical trials and aspects of drug metabolism and toxicity

BACKGROUND

After the tragic events in the early 1960s, thalidomide has re-emerged as therapeutic for multiple myeloma (MM). It was first approved for the treatment of erythema nodosum leprosum, and is now under evaluation for hematologic and non-hematologic disorders. Its complex mechanism of action is not fully understood; however extensive preclinical studies in MM have revealed its antiangiogenic and immunomodulatory properties.

OBJECTIVE

In this review, we focus on the importance and toxicity of thalidomide in today's clinical use.

METHODS

Key preclinical and clinical trials available as well as data on the pharmacokinetics and pharmacodynamics of thalidomide in humans are summarized.

CONCLUSIONS

Thalidomide is widely used as first-line treatment and in relapsed/refractory MM. The most common side effects are fatigue, constipation and peripheral neuropathy, and careful monitoring is required to avoid fetal exposure.

Combination of 5-azacytidine and thalidomide for the treatment of myelodysplastic syndromes and acute myeloid leukemia

BACKGROUND

The treatment of myelodysplastic syndromes (MDS) remains a challenge to the clinician despite recent advances. Many patients will either not respond or will have only limited and/or brief responses to single-agent therapy. Eventually, 30% of patients with MDS will progress and develop acute myeloid leukemia (AML). New strategies are needed for these patients.

METHODS

5-Azacytidine (AZA) and thalidomide were administered to 40 patients with MDS or AML. AZA was given at a dose of 75 mg/m2 subcutaneously for 5 of 28 days together with thalidomide starting at a dose of 50 mg per day and increasing to 100 mg per. Six patients had refractory anemia (RA), 2 patients had RA with ringed sideroblasts, 10 patients had RA with excess blasts (RAEB), 1 patient had RAEB in transformation, 4 patients had chronic myelomonocytic leukemia, 1 patient had chronic idiopathic myelofibrosis, and 16 patients had AML. Thirty-six patients were evaluable for outcome.

RESULTS

A hematologic improvement (HI) was observed in 15 of 36 patients (42%), stable disease was observed in 5 of 36 patients (14%), and 10 of 36 patients (28%) had disease progression. Six patients experienced complete remission (CR), 2 patients experienced an erythroid HI (HI-E), 1 patient experience an absolute neutrophil count HI (HI-ANC), 5 patients experienced a platelet HI (HI-P), and 7 patients had bilineage HI (HI-P and HI-ANC or an HI-E and HI-ANC). It was noteworthy that 9 of 14 patients with AML had a history of prior MDS, 2 of 9 patients achieved a CR, 4 of 9 patients had HI (HI-E and bilineage HI), and 1 patient had stable disease and was continuing treatment. DNA microarray analysis of 8 responders and 4 nonresponders revealed that the genes associated with cellular proliferation had higher expression levels in nonresponders.

CONCLUSIONS

The current findings indicated that a combination of low-dose AZA and thalidomide was well tolerated and was effective therapy for the treatment of patients with MDS and AML arising from prior MDS.

Is there still a role for allogeneic stem-cell transplantation in multiple myeloma?

Despite significant improvements in survival for multiple myeloma patients through autologous stem-cell transplantation (SCT) and the introduction of novel drugs, the disease remains incurable for all but a small fraction of patients. Only allogeneic SCT is potentially curative, due in part to a graft-versus-myeloma effect. High transplant-related mortality with allogeneic SCT is currently the major limitation to wider use of this potentially curative modality. Mortality can be reduced through the use of lower-intensity conditioning regimens which allow engraftment of allogeneic stem cells, but this comes at a cost of higher rates of disease progression and relapse. Promising studies to improve outcomes of allogeneic transplants include the use of more intensive non-myeloablative conditioning regimens, tandem transplants, peripheral blood cells, graft engineering to improve the graft-versus-myeloma activity while reducing graft-versus-host disease (GVHD), post-transplant maintenance, and targeted conditioning therapies such as bone-seeking radioisotopes.

Lenalidomide plus dexamethasone for relapsed or refractory multiple myeloma

BACKGROUND

Lenalidomide is a structural analogue of thalidomide with similar but more potent biologic activity. This phase 3, placebo-controlled trial investigated the efficacy of lenalidomide plus dexamethasone in the treatment of relapsed or refractory multiple myeloma.

METHODS

Of 351 patients who had received at least one previous antimyeloma therapy, 176 were randomly assigned to receive 25 mg of oral lenalidomide and 175 to receive placebo on days 1 to 21 of a 28-day cycle. In addition, all patients received 40 mg of oral dexamethasone on days 1 to 4, 9 to 12, and 17 to 20 for the first four cycles and subsequently, after the fourth cycle, only on days 1 to 4. Patients continued in the study until the occurrence of disease progression or unacceptable toxic effects. The primary end point was time to progression.

RESULTS

The time to progression was significantly longer in the patients who received lenalidomide plus dexamethasone (lenalidomide group) than in those who received placebo plus dexamethasone (placebo group) (median, 11.3 months vs. 4.7 months; P<0.001). A complete or partial response occurred in 106 patients in the lenalidomide group (60.2%) and in 42 patients in the placebo group (24.0%, P<0.001), with a complete response in 15.9% and 3.4% of patients, respectively (P<0.001). Overall survival was significantly improved in the lenalidomide group (hazard ratio for death, 0.66; P=0.03). Grade 3 or 4 adverse events that occurred in more than 10% of patients in the lenalidomide group were neutropenia (29.5%, vs. 2.3% in the placebo group), thrombocytopenia (11.4% vs. 5.7%), and venous thromboembolism (11.4% vs. 4.6%).

CONCLUSIONS

Lenalidomide plus dexamethasone is more effective than high-dose dexamethasone alone in relapsed or refractory multiple myeloma. (ClinicalTrials.gov number, NCT00424047 [ClinicalTrials.gov].).

Improved survival in multiple myeloma and the impact of novel therapies

Treatments for myeloma have expanded in the last decade, but it is not clear if the introduction of novel therapies and the increased use of high-dose therapy have translated into better outcome for patients with myeloma. We examined the outcome of 2 groups of patients seen at a single institution, one from time of diagnosis and the other from the time of relapse, to examine the survival trends over time. Among 387 patients relapsing after stem-cell transplantation, a clear improvement in overall survival from the time of relapse was seen, with those relapsing after 2000 having a median overall survival of 23.9 versus 11.8 months (P < .001) for those who relapsed prior to this date. This improvement was independent of other prognostic factors. Patients treated with one or more of the newer drugs (thalidomide, lenalidomide, bortezomib) had longer survival from relapse (30.9 vs 14.8 months; P < .001). In a larger group of 2981 patients with newly diagnosed myeloma, those diagnosed in the last decade had a 50% improvement in overall survival (44.8 vs 29.9 months; P < .001). In this study, we demonstrate improved outcome of patients with myeloma in recent years, both in the relapsed setting as well as at diagnosis.

Efficient asymmetric synthesis of novel 4-substituted and configurationally stable analogues of thalidomide

The preparation of new thalidomide derivatives 4-methyl-(3S,4R)-3a and 4-phenyl-(3S,4S)-3b starting from pyroglutamic acids (2R,3R)-7a and (2R,3S)-7b, possessing an inappropriate stereochemistry, was successfully realized due to stereochemically complete epimerization at the alpha-stereogenic center upon formation of the corresponding N-phthaloyl anhydrides 9a,b. The demonstrated conformational stability of these new thalidomide derivatives provides solid experimental evidence for practical feasibility of the approach described here to overcome the inherent problem of configurational instability of thalidomide by introducing an alkyl or aryl group in the C4 position. [reaction: see text].

New drugs for myeloma

Although multiple myeloma remains incurable with conventional treatments, management of the disease has recently been transformed with the introduction of three novel agents, bortezomib, thalidomide, and lenalidomide. The proteasome inhibitor bortezomib is approved for the treatment of patients who have received one prior therapy; there is a growing body of clinical evidence showing its effectiveness alone and in combination in the frontline setting, with high response rates and consistently high rates of complete response. Thalidomide plus dexamethasone is approved as frontline treatment of multiple myeloma. Other combination regimens including thalidomide have demonstrated substantial activity in both relapsed and frontline settings. Recently, the thalidomide analogue lenalidomide has been approved, in combination with dexamethasone, for the treatment of patients who have received one prior therapy; this regimen has shown promising results in the frontline setting. These agents represent a new generation of treatments for multiple myeloma that affect both specific intracellular signaling pathways and the tumor microenvironment. Other novel, targeted therapies are also being evaluated in preclinical and clinical studies. Regimens incorporating bortezomib, thalidomide, lenalidomide, and other novel agents, together with commonly used conventional drugs, represent a promising future direction in myeloma treatment. At present, further investigation is required to assess the safety and activity of combinations integrating these other novel agents. However, bortezomib, thalidomide, and lenalidomide are now in widespread clinical use. This review therefore focuses on the extensive clinical data available from studies of these drugs in the treatment of newly diagnosed and advanced multiple myeloma.

Initial Therapy of Multiple Myeloma in Patients who are Candidates for Stem Cell Transplantation

Multiple myeloma (MM), a B cell hematologic malignancy involving plasma cells, responds to a variety of drugs including alkylators, steroids, anthracyclines, immunomodulators and proteosome inhibitors. The disease, however, remains largely incurable for the majority of patients. For patients who are suitable candidates, high dose chemotherapy with autologous stem cell support (ASCT) after induction therapy has been shown to improve response rates, progression free survival and overall survival compared to conventional chemotherapy. The availability of new drugs including thalidomide, lenalidomide and bortezomib has rapidly changed induction strategies. These drugs have been combined with corticosteroids, alkylators and anthracyclines to treat front-line patients with MM. Preliminary, phase 1-2 studies have indicated very high response rates and complete response rates formerly only seen with ASCT. Emerging data from randomized trials suggest that older regimens such as vincristine, adriamycin and dexamethasone (VAD) are not as effective for induction as newer combinations. Thus new regimens incorporating novel agents should improve overall response rates, increase complete responders which should translate into improved progression free and overall survival.

Vascular damaging agents

To provide a comprehensive overview on vascular targeting agents and the application of radiobiological principles in pre-clinical and clinical studies, we completed a comprehensive review of published medical studies on vascular targeting agents using Pub Med. Vascular targeting agents are now divided into vascular disrupting agents (VDAs), which target the pre-existing tumour vasculature, and angiogenesis inhibitors (AIs), which prevent the formation of new blood vessels. Modest success has been seen when VDAs and AIs are used as single agents and therefore combination therapies that can work in a complimentary and synergistic manner, targeting both the tumour cells and endothelial cells, are needed. Radiobiological principles have been used to increase our understanding of these agents, and can explain the increased efficacy of combination treatments. In particular, the alteration of the tumour microenvironment by AIs and VDAs can lead to enhanced efficacy when combined with chemotherapy or radiotherapy, with phase II/III trials showing encouraging results. The optimal use and scheduling of AIs and VDAs remains to be determined. Further understanding of the mechanisms of action of these potentially very exciting anti-neoplastic agents is urgently required.

Initial modulation of the tumor microenvironment accounts for thalidomide activity in prostate cancer

PURPOSE

Disruption of stromal-epithelial interactions favoring prostate cancer progression may affect the phenotype of the disease. We did a preoperative study to test the hypothesis that thalidomide, an active agent in metastatic disease, is a modulator of the tumor microenvironment.

EXPERIMENTAL DESIGN

Eighteen men with high-risk prostate cancer were given thalidomide at doses escalated to 600 mg for 12 weeks, followed by radical prostatectomy. We constructed tissue microarrays from prostatectomy specimens from 15 treated patients and 15 matched untreated control subjects to assess effects of thalidomide on the tumor microenvironment. We compared the immunohistochemical expression of three groups of markers linked to angiogenesis, stromal-epithelial interactions, or the epithelial compartment. Levels of circulating basic fibroblast growth factor, interleukin-6, tumor necrosis factor-alpha, and vascular endothelial growth factor were also assessed.

RESULTS

Thalidomide was well tolerated and induced a median reduction in prostate-specific antigen of 41% without affecting testosterone. Tissue microarray analyses indicated modulation of vascular marker expression accompanied by a reduction in microvessel density in the treated group. Comparison of broader stromal-epithelial interaction markers between treated and control groups suggested a transition to a less aggressive phenotype as a result of thalidomide treatment. Hedgehog signaling was attenuated and the ratio of matrix metalloproteinases to E-cadherin shifted to favor E-cadherin. No differences were noted in proliferation or apoptosis in the epithelial compartment.

CONCLUSIONS

These findings are the first clinical evidence to support the hypothesis that the reported thalidomide clinical efficacy is attributable to early modulation of the tumor microenvironment and suggest that stromal-targeting therapies will be effective against prostate cancer.

Final Report of Toxicity and Efficacy of a Phase II Study of Oral Cyclophosphamide, Thalidomide, and Prednisone for Patients with Relapsed or Refractory Multiple Myeloma: A Hoosier Oncology Group Trial, HEM01‐21

Thalidomide has direct antimyeloma and immunomodulatory effects. In addition, both thalidomide and metronomic chemotherapy inhibit angiogenesis. The synergy of such a combination may decrease toxicity while maintaining efficacy. The Hoosier Oncology Group conducted a phase II trial of oral cyclophosphamide (50 mg b.i.d. for 21 days), thalidomide (200 mg/day), and prednisone (50 mg q.o.d.) (CTP) per 28-day course in patients with relapsed multiple myeloma (MM). Of the 37 patients enrolled, 16 had prior stem cell transplantation. The median follow-up time was 25.3 months (95% confidence interval [CI] 23.2-27.7). Of 35 patients treated, 22 patients (62.9%) responded: 7 (20.0%) complete responses, 2 (5.7%) near-complete responses, and 13 (37.1%) partial responses. Eight patients (22.9%) had stable disease, and three (8.6%) had disease progression. Two patients withdrew from the study early due to reasons unrelated to progression or toxicity and were treated as nonresponders. The median time to best response and time to progression were 3.6 months (95% CI 2.8-10.9) and 13.2 months (95% CI 9.4-21.0), respectively. The median number of treatment cycles was seven (range 1-12 cycles). Grade III to IV toxicities included leukopenia (42.9%; febrile neutropenia, 11.4%), hyperglycemia (20%), sensory neuropathy (11.4%), thromboses (8%), and motor neuropathy (5.7%). No patient withdrew from the study due to toxicity. The efficacy and low toxicity of the CTP regimen support the future development of such an approach in MM.

Phase I Trial of First-Line Bortezomib/Thalidomide plus Chemotherapy for Induction and Stem Cell Mobilization in Patients with Multiple Myeloma

BACKGROUND

In preclinical studies, bortezomib was shown to suppress tumor growth, sensitize malignant cells to apoptosis, and reverse chemotherapy resistance.

PATIENTS AND METHODS

We evaluated the addition of escalating doses of bortezomib 0.7, 1, and 1.3 mg/m2 intravenously on days 1, 4, and 8 to DT-PACE (cisplatin 10 mg/m2, doxorubicin 10 mg/m2, cyclophosphamide 400 mg/m2, and etoposide 40 mg/m2 per day by intravenous continuous infusion on days 1-4) plus oral dexamethasone 40 mg on days 1-4 and thalidomide 200 mg on days 1-8 in newly diagnosed patients with multiple myeloma. Peripheral blood stem cells were collected after cycle 1. Twelve patients completed the study, and all received autologous stem cell transplantation (SCT).

RESULTS

Hematologic toxicities were predictable, with 3 episodes of neutropenic fever. Grade >/= 2 nonhematologic toxicities included diarrhea (n = 1), deep vein thrombosis (n = 2), hypotension (n = 2), syncope (n = 1), and peripheral neuropathy (n = 3). The median number of CD34+ cells collected was 20.57 x 10 superset6 CD34+ cells/kg. After 2 cycles, 10 of 12 patients exhibited a partial response or better. Best response after autologous SCT, complete response/near complete response was exhibited in 9 patients, and partial response was exhibited in 3 patients. At a median of 20 months, 4 patients experienced relapse and 1 had died. Bortezomib/DT-PACE compared favorably with DT-PACE with regard to leukapheresis days, total CD34+ cell collection, and engraftment.

CONCLUSION

This novel strategy of simultaneous proteasome inhibition in combination with thalidomide and chemotherapy was effective and safe, allowing for adequate stem cell collection and early autologous SCT; its impact on overall survival, especially in patients with high-risk myeloma, awaits further investigation.

The current status of reduced-intensity allogeneic hematopoietic stem cell transplantation for multiple myeloma

Of all the treatment modalities employed to control multiple myeloma, only allogeneic hematopoietic stem cell transplantation is potentially curative, due in large part to a graft-versus-myeloma (GVM) effect. Whereas patients who receive either allogeneic or autologous stem cell transplants for multiple myeloma have similar 3-5-year survival, only allograft recipients appear to enjoy long-term disease-free survival. High transplant-related mortality (TRM) associated with allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative modality. This high mortality has been the major impetus for exploration of reduced intensity conditioning (RIC) regimens designed to allow engraftment of allogeneic stem cells. With follow-up now extending to 7 years, it is clear that when compared to myeloablative transplants, RIC allografts are associated with lower TRM; however, reduced mortality comes at a cost of higher rates of disease progression and relapse. Strategies designed to improve the therapeutic index of allografts include the use of more intensive, yet still non-myeloablative conditioning regimens, tandem autologous plus RIC allografts, peripheral blood cells rather than bone marrow, graft engineering to improve the GVM activity while reducing graft-versus-host disease, post-transplant maintenance and targeted conditioning therapies such as bone-seeking radioisotopes.