New Directions in the Treatment of Mantle Cell
`Lymphoma: An Overview
`
`Andre Goy
`Abstract
`
`Mantle cell lymphoma (MCL) is one of the most challenging lymphomas to treat. In the first-line setting, high-dose therapy (HDT) and autologous
`stem cell transplantation or hyperCVAD/rituximab suggest benefit, especially in patients aged < 60 years. Nucleoside analogue–based regimens
`represent an alternate option in patients ineligible for HDT. Fludarabine in combination with cyclophosphamide or mitoxantrone has shown activ-
`ity, and the results were superior with the addition of rituximab. Other cytotoxic agents, such as cladribine, clofarabine, or bendamustin, showed
`promising activity as well. A variety of new monoclonal antibody (MoAb) agents, such as humanized anti-CD20, alemtuzumab, anti–HLA-DR,
`anti-CD22 (as an immunotoxin carrier), anti-CD40, as well as MoAb-targeting TRAIL-R1 and TRAIL-R2 are being tested. Radioimmunotherapy
`with Yttrium 90–ibritumomab tiuxetan and Iodine 131 tositumomab have been tested alone or in combination with chemotherapy, including as
`part of HDT and autologous stem cell transplantation, in which they showed the best results. New vaccine modalities are exploring the use of
`tumor cell–based vaccines or of agents that block or activate costimulatory pathways/molecules, such as CTLA-4–Ig. Allogenic transplantation
`represents a potential curative option for MCL, especially nonmyeloablative transplantation, more feasible in that population. A plethora of novel
`biologic agents have surfaced, such as bortezomib, temsirolimus, thalidomide, lenalidomide, MoAb anti–vascular endothelial growth factor or
`vascular endothelial growth factor–Trap, and flavopiridol. Other targets include gene transcription through histone regulation; nuclear factor–(cid:103)B
`pathway; protein kinase C inhibitors; small-molecules targeting apoptosis, such as antisense Bcl-2, pan–Bcl-2 family member inhibitors; MoAb
`agonists of cell death receptors; caspases regulators (inhibitors of apoptosis proteins, survivin); and MDM2 antagonist regulators of p53. A
`molecular approach to define biomarkers might help identify subgroups of patients and help develop rational therapies.
`
`Clinical Lymphoma & Myeloma, Vol. 7, Suppl. 1, S24-S32, 2006
`Key words: Antisense, Bcl-2 inhibitors, Cytotoxic agents, Idiotype vaccine, Mammalian target of
`rapamycin inhibitors, Monoclonal antibodies, Nucleoside analogues, Proteasome inhibitors
`
`Introduction
`Although mantle cell lymphoma (MCL) represents only 6%
`of non-Hodgkin’s lymphomas (NHLs), it remains the most
`challenging lymphoma to treat and, hence, is also one of the most
`active fields of clinical research with multiple novel options, some
`of which will be highlighted in this review.
`Mantle cell lymphoma is recognized as a distinct clinicopathologic
`subtype of B-cell lymphoma derived from a CD5+, antigen-naive,
`pregerminal center B cell within the mantle zone surrounding
`normal germinal center follicles. Mantle cell lymphoma cells
`carry the following immunophenotype: positive for CD20,
`CD5, CD43, FMC7, as well as a surface immunoglobulin but
`negative for CD10, CD23, and Bcl-6. Mantle cell lymphoma
`cells also overexpress cyclin D1 as a result of the landmark
`t(11;14)(q13;q32) translocation.
`Patients with MCL are typically older adults (median age,
`early to mid 60s) with a male predominance and usually
`advanced stage, though B symptoms are seen in only a third
`
`Hackensack University Medical Center, NJ
`
`Submitted: Sep 19, 2006; Revised: Oct 5, 2006; Accepted: Oct 5, 2006
`
`Address for correspondence: Andre Goy, MD, Hackensack University
`Medical Center, 20 Prospect Ave, Hackensack, NJ 07601
`Fax: 201-336-9246; e-mail: agoy@humed.com
`
`to half of patients.1,2 Patients present with lymphadenopathy,
`splenomegaly, and a variable degree of leukemic phase3 but almost
`constant extranodal involvement, which includes bone marrow,
`liver, and characteristically gastrointestinal (GI) involvement. The
`GI tract involvement can vary from extensive and symptomatic
`polyposis coli to just positive random biopsy results in > 90% of
`patients at baseline.4
`Despite response rates to many regimens in the 50%-70%
`range, the disease typically progresses after chemotherapy with
`a median survival time of approximately 3-4 years. There is no
`clear standard approach for treating MCL, making it critical that
`patients be enrolled in clinical trials. This review will highlight
`some of the ongoing changes in the paradigm of MCL from new
`directions in conventional chemotherapy as well as more recent
`developments, including biological agents, which by targeting
`specific pathways, might represent a step toward more rational
`therapeutics.
`Update on Conventional Cytotoxic Regimens
`CHOP (cyclophosphamide/vincristine/doxorubicin/prednisone)–
`based chemotherapy remains, by default and too often, the standard
`of care. Although rituximab in itself has a relatively modest overall
`response rate (ORR) and duration of response (DOR) in MCL
`compared with follicular lymphoma in the relapsed setting,5 its
`combination with the CHOP regimen (R-CHOP) appears superior
`
`Dr. Goy is a member of the Speaker’s Bureau for Millennium, Genentech BioOncology, GlaxoSmithKline, and Biogen Idec.
`This article includes discussion of investigational and/or unlabeled uses of drugs, including the use of rituximab, alemtuzumab, epratuzumab,Yttrium 90 ibritumomab tiuxetan or Iodine
`131 tositumomab alone or in combination with chemotherapy and bendamustine, bortezomib, NPI-0052, PR 171, temsirolimus, everolimus, thalidomide, flavopiridol, bryostatin,
`oblimersen, and GX-15070 in the treatment of relapsed mantle cell lymphoma.
`
`S24 • Clinical Lymphoma & Myeloma Vol 7 Suppl 1 October 2006
`
`Apotex Ex. 1016, p.1
`
`

`

`to CHOP alone. However, in a small randomized study comparing
`CHOP with R-CHOP, Howard et al showed a trend in favor of
`R-CHOP in time to treatment failure but no clear difference in
`outcome. Interestingly, the molecular complete response (CR) rate,
`which appeared superior in the R-CHOP arm, showed no impact on
`progression-free survival (PFS) in that series.
`
`Hyper-CVAD
`Given the poor results seen with standard anthracycline regimens,
`M. D. Anderson Cancer Center (MDACC) developed a dose-intense
`regimen, hyper-CVAD (hyperfractionated cyclophosphamide/
`vincristine/doxorubicin/dexamethasone alternating with high-dose
`methotrexate/cytarabine), initially used as an induction therapy
`for patients with MCL before consolidation with autologous
`stem cell transplantation (ASCT).6 A subset of patients who were
`found not eligible or refused to pursue ASCT continued receiving
`hyper-CVAD and had similar outcomes, serving as rationale for
`the current hyper-CVAD, which was given in conjunction with
`rituximab.7 This prospective study included 97 assessable patients,
`with an ORR of 97% and 87% CR/unconfirmed CR (CRu). Of
`notice, restaging studies included upper and lower endoscopies in
`all patients. With a median follow-up time of 40 months, the 3-year
`failure-free survival rate was 64%, and overall survival was 82%.
`Although there was no plateau, these results are very encouraging,
`especially in the subgroup of patients aged (cid:41) 65 years, in whom
`the 3-year failure-free survival was 73%. For the patients aged > 65
`years, the overall results were inferior except in the group with
`normal (cid:96)2-microglobulin at baseline who had similar outcome as
`younger patients. The main toxicity was hematologic as expected.
`A modified version of rituximab-hyper-CVAD with rituximab
`maintenance suggests, in preliminary results, an ORR comparable
`with conventional hyper-CVAD (85% vs. 93%) and appears less
`toxic, especially in patients aged > 60 years.8 When compared with
`historical controls, the original and modified hyper-CVAD regimens
`provide a much greater CR rate than R-CHOP (87%, 70%, and
`34%-48%, respectively) and considerably longer median PFS (not yet
`reached vs. 16-20 months).
`
`Role of Nucleoside Analogues
`Fludarabine is the purine nucleoside analogue with the most data
`in MCL; single-agent activity showed an ORR of 30%-40% and
`63% when combined with cyclophosphamide.9-11 Recent studies
`looking at fludarabine/mitoxantrone with or without rituximab
`showed a clear benefit for the rituximab arm combination.12 A
`randomized study comparing R-CHOP and FCR (fludarabine/
`cyclophosphamide/rituximab) is ongoing in Europe in patients
`aged > 60 years.
`Cladribine, or 2CDA, also showed activity as a single agent13 or
`combined with mitoxantrone14 or with rituximab.15 Clofarabine
`showed some activity in preliminary studies and is currently being
`evaluated in larger trials.
`
`New Cytotoxic Agents
`Bendamustin, previously known as SDX-105, was only available
`in the German Democratic Republic as Cytostasan between 1971
`and 1992. This compound contains a nitrogen mustard group
`and a benzimidazole ring, which might act as a purine analogue.
`Bendamustin has therefore been studied for years and has shown
`activity against cell lines resistant to other alkylating agents as
`well as clinical activity against a variety of lymphomas, including
`
`MCL. It has been more recently integrated in other regimens
`including in combination with rituximab (BR), in which BR
`showed considerable activity, with an ORR of 75% and CR rate
`of 50%.16 Additional studies in combination with mitoxantrone or
`fludarabine are also under way.
`Multiple new cytotoxic agents are being evaluated in an attempt
`to improve on anthracycline toxicity profile with pixantrone to
`the epothilones group (ixabepilone, a microtubule stabilizer)
`or SY2121 (a mitosin kinase spindle inhibitor), which are
`all currently in phase I/II trials. Second-generation polyamin
`analogues with conformational restriction, which can inhibit
`polyamine synthesis and disrupt the cell cycle, are also just
`entering the clinic.
`High-Dose Therapy and Transplantation
`Because of the poor results again seen with conventional standard
`chemotherapy regimens, high-dose therapy has been studied
`extensively in MCL, initially in the relapse setting but also in first-
`line as consolidation.17,18
`Unfortunately, the results of these studies have been mixed, and
`although most studies showed a benefit compared with standard-
`dose therapy, there is no confirmed indication that the procedure is
`curative. A recent study by the German group comparing CHOP-
`based chemotherapy followed by interferon (IFN) maintenance
`versus intensification with high-dose therapy has shown to be
`superior, although there was no plateau, and patients continue to
`experience relapse.19
`Despite encouraging reports from single centers and registries,
`the impact of stem cell transplantation on the outcome for MCL is
`unclear, and several issues remain unresolved.
`Prospective randomized trials have been difficult to design and
`conduct in this “nonconsensus disease” because of an absence of
`optimal first-line regimens in MCL. Preliminary results suggest that
`the role of high-dose cytarabine is important as part of induction/
`consolidation therapy in MCL.20 This hypothesis is currently being
`tested for confirmation in a large randomized study in Europe
`looking at R-CHOP/Dexa-BEAM (melphalan/dexamethasone/
`carmustine/cytarabine/etoposide)/cyclophosphamide/total-body
`irradiation (TBI) regimen versus R-CHOP/DHAP (cisplatin/
`cytarabine/dexamethasone)/TBI/cytarabine/melphalan.
`The role of stem cell transplantation as a part of salvage therapy
`is also unknown, although available data suggest that it does not
`improve survival in heavily pretreated patients.21
`Efforts to define prognostic factors for HDT/ASCT in patients
`with MCL suggest that:
`
`• A TBI conditioning regimen versus a chemotherapy-based
`regimen might be an important factor in outcome after ASCT
`and might explain some differences among studies, because TBI
`is more commonly used in Europe than the United States. This
`would be consistent with the promising results seen with high-
`dose radioimmunotherapy detailed herein,22 though in small
`studies so far.
`• Other factors include (cid:96)2-microglobulin and tumor score as per
`the MDACC experience.23
`• For minimal residual disease, so far the data are based on small
`numbers but suggest that high-dose therapy might improve
`minimal residual disease, which would then translate into a
`better outcome.24 The addition of rituximab peritransplantation
`might also improve minimal residual disease and risk of relapse
`after ASCT.25-28
`
`Clinical Lymphoma & Myeloma Vol 7 Suppl 1 October 2006 • S25
`
`Apotex Ex. 1016, p.2
`
`

`

`Mantle Cell Lymphoma: Treatment Options
`
`Allogeneic Transplantation
`Mantle cell lymphoma remains incurable with conventional
`chemotherapy, and though some patients have long-term
`remission after dose-intense therapy, in the relapse setting, the
`prognosis remains very poor, because the disease quickly becomes
`chemotherapy resistant. The presence of a graft-versus-tumor
`effect has now been well established in a variety of hematologic
`malignancies, including indolent lymphomas and MCL. Because
`of the median age of MCL (mid 60s), the risks of conventional
`allogeneic transplantation make it a rarely valid option. The
`development of nonmyeloablative regimens has dramatically
`changed the outcome of those patients as shown by several
`studies.29,30 Results vary depending on the studies but clearly
`show that a subset of patients can have prolonged DFS up to
`60% at 2 years. Although these studies remain relatively small
`and mostly based on single-institution experiences, they suggest
`nonmyeloablative allogenic transplantation might be the only
`potentially curative option in MCL. This implies that a donor
`search should be initiated in all patients with MCL, especially in
`the younger population with poor prognostic features at baseline
`or certainly those in first relapse.
`
`Impact of Immune-Based Therapy in the
`Management of Mantle Cell Lymphoma
`Monoclonal Antibodies
`Rituximab. As mentioned previously, rituximab has modest
`activity as a single agent when compared with follicular lymphoma
`for example; however, its combination with a variety of regimens
`discussed previously (R-CHOP or FCR) has shown to be beneficial.
`In a more complex study, patients with relapsed/refractory follicular
`lymphoma (FL) and MCL were randomized to receive 4 courses
`of FCM (fludarabine/cyclophosphamide/mitoxantrone) alone
`or combined with rituximab (R-FCM). Responding patients
`underwent a second randomization for rituximab maintenance
`comprising 2 further courses of 4 weekly doses of rituximab after 3
`months and 9 months. The first randomization was stopped after
`147 patients were enrolled, when R-FCM revealed a significantly
`superior outcome, and all subsequent patients received R-FCM.12
`In addition, DOR was significantly prolonged by rituximab
`maintenance after R-FCM, with the median DOR not being reached
`versus 16 months (P = 0.001). This beneficial effect was also observed
`when analyzing FL (P = 0.035) and MCL (P = 0.049) separately.
`This study suggests that rituximab maintenance is effective after salvage
`therapy with rituximab and significantly prolongs DOR in patients
`with relapsed/refractory FL or MCL.31 This observation was not true
`when rituximab was given as maintenance after rituximab induction
`as a single agent, consistent with the modest activity of rituximab
`by itself in MCL.5 Rituximab also appears beneficial as part of an
`ASCT conditioning regimen and as posttransplantation consolidation
`therapy, with which it seems to improve PFS.26,28,32-34
`
`New Antibodies. A variety of humanized antibodies (to improve
`infusion reaction and potentially antibody-dependent cellular
`cytotoxicity) also targeting CD20 are currently in trials including
`MCL. A large number of other monoclonal antibodies (MoAbs)
`are still under investigation including anti-CD52 (alemtuzumab),
`which is mostly used as part of conditioning regimens in allogeneic
`transplantation35 or also tested in combination with rituximab as
`salvage therapy in MCL, knowing that MCL strongly expresses
`CD52. Other MoAbs include anti-CD22 (epratuzumab), which
`
`has not been as effective as a single agent but, because of its rapid
`internalization,36 might reveal itself to be more useful as a “drug
`shuttle” or immunotoxin. This provided a rationale for ongoing
`studies with calicheamycin (CMC-544) in B-cell NHL, including
`in MCL.37,38 Other MoAbs include anti–human leukocyte antigen
`DR-1 or anti-CD40, which can induce antibody-dependent
`cellular cytotoxicity and inhibit proliferation in preclinical models
`in a variety of B-cell lymphoma cell lines.39 Multiple other MoAbs
`are in development, including antibodies against cell surface death
`receptors targeting the Fas/tumor necrosis factor (TNF)–related
`apoptosis-inducing ligand (TRAIL) pathway detailed herein.40
`
`Idiotype Vaccine
`In order to prevent recurrence of disease in MCL after
`chemotherapy (at the stage of minimal residual disease), active
`immunization using an anti-idiotype vaccine have been attempted in
`MCL. The main study was done using an induction with R-EPOCH
`(cyclophosphamide/doxorubicin/etoposide/prednisone/rituximab/
`vincristine) chemotherapy followed by conventional anti-idiotype
`vaccine.41 Results showed the induction of tumor-specific humoral
`responses that were delayed because of B-cell depletion secondary to
`rituximab (and occurred only after peripheral blood B-cell recovery).
`In contrast, in most individuals (even in the absence of circulating B
`cells), T-cell CD4+ and CD8+ antitumor type I cytokines responses
`were induced. However, all immune responses did not translate into
`any clinical benefit or risk of recurrence. Mantle cell leukemia is still
`a rather aggressive disease overall, making it a challenging subtype of
`lymphoma for vaccine approaches, which remain time consuming,
`and when likely, the humoral response seems critical, as seen in other
`NHLs. Additional schedules and other vaccine models are being
`evaluated and might benefit the more indolent subtypes of MCL.
`
`Cell-Based Vaccines After Chemotherapy
`In the first example, after CHOP or hyper-CVAD (without
`rituximab), patients receive a vaccine composed of autologous
`tumor cells and GM.CD40L intradermally on day 1 and low-dose
`interleukin-2 subcutaneously twice daily on days 1-14. Another
`approach is to use proteinase-3 peptides for immunization after
`allogeneic transplantation in MCL, though both studies are still
`in development.
`Immunomodulation through the use of agents that block or
`activate costimulatory pathways/molecules might help induce a
`strong autologous antitumor effect (ie, break tumor tolerance) as
`shown with encouraging success of CTLA-4–immunoglobulin,
`which is also being investigated in refractory/relapsed MCL.42
`
`Radioimmunotherapy
`At this point, radioimmunotherapy (RIT) is essentially targeting
`anti-CD20 and encompasses 2 agents: ibritumomab tiuxetan and
`tositumomab. Promising activity has been shown for both as single
`agents and in combination. In a small series with ibritumomab
`tiuxetan, 5 of 15 relapsed MCLs responded (33%) including 3 CRs
`and 2 CRus, although the median DOR of patients with CR/CRu
`was only 5.7 months.43,44 The combination of RIT with standard
`chemotherapy as first-line therapy has been explored as sequential
`tositumomab followed by CHOP45 or R-CHOP followed by
`ibritumomab tiuxetan (Eastern Cooperative Oncology Group 1499,
`just recently completed). The tositumomab/CHOP combination
`study showed activity of RIT in the first-line setting with an ORR
`of 83% and CR rate of 46%.45 In addition, 7 of 20 informative
`
`S26 • Clinical Lymphoma & Myeloma Vol 7 Suppl 1 October 2006
`
`Apotex Ex. 1016, p.3
`
`

`

`patients by clonotypic PCR exhibited a molecular CR. Although the
`clinical CR/CRu rate went up to 64% after CHOP, there was no
`additional molecular CR. This remains a small series (24 patients);
`there was no rituximab, and the requirement of < 25% bone marrow
`involvement at baseline might be a limiting factor in MCL. In the
`Eastern Cooperative Oncology Group study, 50 evaluable patients
`with previously untreated MCL received 4 cycles of R-CHOP
`followed by consolidation with ibritumomab tiuxetan.46 Results
`showed that consolidation with ibritumomab tiuxetan after R-CHOP
`chemotherapy increased (tripled) the CR rate, though more follow-
`up is needed to see how these responses are sustained (in an otherwise
`relatively short chemotherapy induction).
`The most impressive results of RIT in MCL have been as part
`of a conditioning regimen before ASCT in MCL22 using high-dose
`iodine 131–labeled tositumomab, etoposide, and cyclophosphamide
`with stem cell support in 16 patients with relapsed MCL. The
`response rate was 100% with a 91% CR rate, 93% survival at 3
`years, and 61% of patients who remained disease free at 3 years.
`This approach to replace TBI is now being explored on a larger
`scale as a full dose or a reduced dose as part of nonmyeloablative
`allogenic bone marrow transplantation regimens.
`
`New Biologic Agents
`Proteasome Inhibitors
`Proteasome inhibition has been one of the exciting and promising
`new approaches in MCL. The proteasome is a large multiunit
`protease complex, which processes the vast majority of intracellular
`proteins including abnormal proteins (more common in cancer
`cells) and short-lived proteins (33% of nascent proteins have a
`half-life of < 10 minutes), which are typically involved in critical
`functions such as cell cycle, cell growth, differentiation, and/or
`apoptosis.47 Proteasome inhibition results in the disruption of
`a variety of pathways and checkpoints leading to apoptosis.
`Bortezomib is a novel small molecule with potent selective and
`reversible inhibition of the chymotrypsin-like enzyme (1 of the 3
`enzymes located within the core of the proteasome).48
`Bortezomib is the first in class of proteasome inhibitors
`with activity initially seen in the original phase II studies49,50
`and now confirmed by other investigators in Canada51 and
`the United Kingdom,52 with an ORR in the range of 40%
`altogether. The intermediate analysis of the pivotal international
`trial (PINNACLE study), completed in May 2005 (with 155
`patients enrolled) again confirmed the activity of bortezomib
`in patients with relapsed/refractory MCL in the multicenter
`setting.53 This study was updated at American Society of Clinical
`Oncology in June 2006 with a final ORR of 33% (including an
`8% CR/CRu rate) and a median DOR of 9.2 months and up to
`13.5 months in patients who had exhibited a CR.54 The activity
`was confirmed in patients with primary refractory disease or
`patients whose disease had failed to respond to previous high-
`dose therapy and did not seem to correlate with the number
`of previous treatments, as shown in our previous experience
`at MDACC. Moreover, a similar response rate was found in
`untreated versus treated MCL in the Canadian experience.51 All
`phase II studies showed similar toxicity profiles with fatigue, GI
`toxicity, neuropathy, and thrombocytopenia. The similar range
`of ORRs (35%-45%) to bortezomib across all studies underlines
`the need for biomarkers predictive of response to bortezomib
`in MCL. Recent work suggests that the proteasome inhibitor
`bortezomib induces distinct changes in MCL compared with
`
`Andre Goy
`
`other types of lymphoma, including the overexpression of MCL1
`(an antiapoptotic protein described as myeloid cell leukemia 1) and
`induction of apoptosis through NOXA (from Latin: damage) and
`reactive oxygen species independently of p53 status.55 Additional
`work is under way to refine our understanding of mechanisms and
`resistance to bortezomib in MCL.
`Ongoing studies are also exploring the use of bortezomib in
`combination with a variety of other chemotherapy regimens,
`including R-EPOCH (National Cancer Institute), R-CHOP,56
`and hyper-CVAD (MDACC and Hackensack University Medical
`Center), among others, as well as other biologic agents and
`small molecules as detailed later. The mechanisms of resistance
`to proteasome inhibition appear to involve heat-shock proteins,
`providing a rationale for combination with heat-shock protein
`inhibitors, some of which have also shown preliminary evidence
`of activity in lymphoma on their own as well (ie, 17-allylamino-
`17-demethoxygeldanamycin or geldamycin). Interestingly, many
`of these combinations using bortezomib and other agents appear
`to be schedule dependent,57 which might impact the design of our
`clinical trials.
`
`Second Generation Proteasome Inhibitors
`NPI-0052. NPI-0052 is an oral compound that can inhibit all
`3 enzymes of the 20S unit of the proteasome and is just entering
`the clinic.
`
`PR171. PR171 is a novel, irreversible proteasome inhibitor
`under investigation in phase I/II studies. Despite being irreversible,
`preclinical data showed that the half-life of recovery from proteasome
`inhibition in tissues was approximately 24 hours. PR-171 was found
`to be active in cell lines and murine models and is currently being
`tested in hematologic malignancies including lymphomas using 2
`different schedules: days 1-2 weekly for 3 weeks every 4 weeks or
`days 1-5 every other week in an attempt to increase duration of
`proteasome inhibition and potentially its efficacy.
`
`Mammalian Target of Rapamycin Inhibitors
`The Mammalian Target of Rapamycin Pathway
`The mammalian target of rapamycin (mTOR) is a downstream
`effector of the phosphatidylinositol 3–kinase (PI3K)/Akt (protein
`kinase B) signaling pathway, which mediates cell survival and
`proliferation. Mammalian target of rapamycin regulates essential
`signal-transduction pathways, in particular the coupling of growth
`stimuli and nutrient status with cell cycle progression and initiation of
`messenger RNA translation (Figure 1). Hence, the mTOR pathway
`is involved in regulating many aspects of cell growth, including
`membrane trafficking, protein degradation, protein kinase C signaling,
`ribosome biogenesis, and transcription; as such, the mTOR complex
`is sometimes called an "integrator" of the cellular environment.
`The mTOR kinase regulates protein translation by phosphorylation
`of 2 critical substrates: the eukaryotic initiation factor 4E and the
`p70S6 kinase, which will control the final step in protein translation
`including that of cyclin D1, an important potential target in MCL.
`The activity of mTOR can be inhibited by rapamycin analogues, and
`in preclinical models, mTOR inhibitors induce apoptosis and can
`inhibit angiogenesis. Several rapamycin derivatives are currently being
`evaluated in lymphomas, especially in MCL.
`
`Temsirolimus
`Temsirolimus has been shown to be active in relapsed/refractory
`MCL using a dose of 250 mg intravenously (I.V.) weekly as a single
`
`Clinical Lymphoma & Myeloma Vol 7 Suppl 1 October 2006 • S27
`
`Apotex Ex. 1016, p.4
`
`

`

`Mantle Cell Lymphoma: Treatment Options
`
`Figure 1
`
`Novel Targets in Anticancer Therapy
`
`PI3K
`Inhibitors
`
`Flavopiridol/
`CDK
`Inhibitors
`
`PKC
`Inhibitors
`
`I(cid:103)K/NF-(cid:103)B
`Inhibitors
`
`Proteasome
`Inhibitors:
`Bortezomib
`PR171
`NPI-0052
`
`I(cid:103)K
`
`I(cid:103)B
`
`Cell Surface
`Death Receptor
`
`FAS
`
`FAD
`
`FAS/TRAIL MoAbs
`TRAIL-R1
`TRAIL-R2
`
`Proteasome
`
`Caspases
`
`IAP/
`ICAD
`
`Apoptosis
`
`Bcl-2 Family
`Member
`Inhibitors:
`Oblimersen
`AT101
`ABT737
`GX-15070
`
`IAPs
`Survivin
`Caspase
`Modulators
`
`P P
`
`P P
`
`P P
`
`PI3K
`
`PIP2
`
`PKC
`
`PIP3
`
`AKT
`
`mTOR
`
`ATM
`
`P
`
`p53
`
`p21
`
`B
`
`I (cid:103)
`
`PDK
`
`Cyclin
`D1
`
`Bcl-2
`
`Cyt C
`
`Apaf-1
`Caspase
`
`mTOR
`Inhibitors:
`Temsirolimus
`Everolimus
`AP23573
`
`X-Ray
`Damage
`
`P53
`Modulators
`
`The 2 apoptosis pathways are represented around the central figure played by the mitochondria. A variety of factors modulating apoptosis pathways or cell cycle are shown from membrane receptors
`to intracellular signaling key proteins, which represent potential targets currently being evaluated in preclinical and/or clinical settings. The targets are highlighted in distinct colors with examples of
`corresponding agents or class of agents.
`Abbreviations: IAP = inhibitor of apoptosis; ICAD = inhibitor of caspase-activated DNase; PKC = protein kinase C
`
`agent, with an ORR of 38% with 1 CR (3%), 12 PRs (35%),
`and a DOR of 6.9 months. Hematologic toxicities were the most
`common, with 81% grade 3/4, especially thrombocytopenia.
`Although this was reversible, ongoing trials are testing lower doses
`(25 mg weekly), and preliminary results suggest a maintained
`activity and less myelosuppression with thrombocytopenia in a
`quarter of patients. This study will also help in deciding dosing only
`for future combination studies. Meanwhile, a large international
`randomized trial is currently under way to evaluate temsirolimus
`against treatment of choice (among a defined set of options) in
`relapsed MCL. Temsirolimus is also being tested in relapsed MCL
`in combination with rituximab.
`As in other biologic agents, it will become important to define
`which subsets of patients might benefit most from mTOR
`inhibitors. Recent data confirm that the constitutive activation of
`P13K/Akt contributes to the pathogenesis and survival of MCL.
`The activation of AKT and its downstream targets in MCL appears
`dependent on P13K. This seems to result from a loss of PTEN
`rather common in MCL cells and not as a consequence of P13K
`mutations. Akt was found phosphorylated in 12 of 12 aggressive
`blastoid MCL variants and in 4 of 4 NCL cell lines, but only 5 of
`16 typical MCL (2 of them at low level). Preclinical data suggest
`that P13K/Akt pathway inhibitors such as mTOR inhibitors might
`be more effective in the treatment of Akt-activated MCL, especially
`in blastoid variants.58
`
`Other Mammalian Target of Rapamycin Inhibitors
`Everolimus, an oral derivative of rapamycin, appeared to be
`well tolerated from a phase I study59 and is currently being
`evaluated in phase II studies including relapsed MCL. AP23573
`is a nonprodrug rapamycin analogue tested as an mTOR inhibitor
`as well. In phase I clinical trials, AP23573 completely inhibited
`in vivo mTOR activity in peripheral blood mononuclear cells as
`measured by decreased phosphorylation levels of the mTOR target
`protein 4EBP-1. AP23573 was tested in early trials (12.5 mg I.V.
`daily for 5 days every 2 weeks) and was well tolerated with no
`thrombocytopenia. Efficacy was seen in leukemia and is currently
`being evaluated in lymphoma, including MCL.60
`
`Inhibitors of Angiogenesis
`Thalidomide
`Based on its activity on the microenvironment and activity in other
`B-cell malignancies, including multiple myeloma, thalidomide was
`tested in MCL. The preliminary activity of thalidomide seen in MCL
`cases led to testing its combination with rituximab.61 Rituximab was
`administered at 375 mg/m2 weekly for 4 doses concomitantly with
`thalidomide (200 mg daily with a dose increment up to 400 mg on day
`15), which was continued as maintenance therapy until progression or
`relapse. Thirteen patients (81%) experienced an objective response,
`with 5 CRs (31%). Median PFS was impressive at 20.4 months, and
`
`S28 • Clinical Lymphoma & Myeloma Vol 7 Suppl 1 October 2006
`
`Apotex Ex. 1016, p.5
`
`

`

`the estimated 3-year survival was 75%. Severe adverse events included
`2 thromboembolic events and 1 incidence of grade 4 neutropenia
`associated with thalidomide. Rituximab/thalidomide appears to have
`marked antitumor activity in relapsed/refractory MCL and might
`represent a good option in elderly patients. These results provide a
`rationale to explore thalidomide in the first-line setting with R-CHOP
`or other regimens (R-PEPC). The Austrian study with thalidomide/R-
`CHOP will also look at the role of maintenance with thalidomide in
`MCL after chemotherapy induction.
`In order to improve on the thalidomide experience, the next step
`was to test the potential activity of lenalidomide parallel to multiple
`myeloma. Lenalidomide showed activity as a single agent in NHL,
`including in MCL (European Hematology Association 2006), and
`is currently being tested in combination with rituximab and/or
`other agents in relapsed MCL.
`Other ways to target angiogenesis have been through MoAbs,
`including bevacizumab and vascular endothelial growth factor trap,
`also currently being tested in B-cell NHL, including MCL, again
`with rituximab or in combination with chemotherapy.
`
`Histone Deacetylases
`The chromatin structure (open vs. closed chromatin) affects gene
`transcription. This occurs as a result of the opposing activities of 2
`types of enzymes, the histone deacetylases (HDACs; which remove
`acetylation