Hematology Meeting Reports 2009;3(3):4–9 SESSION I

G. Saglio Molecular targeted therapies for indolent G. Parvis M. Bosa lymphomas: where are we?

Department of Clinical and Biological Sciences, University of Turin, Regione Gonzole, Orbassano, TO, Italy During the last decade the analysis11 suggested that mainte- development of new drugs for the nance therapy with rituximab, treatment of hematologic malig- either as four weekly infusions nancies has become really prom- every 6 months or as a single infu- ising. This innovative drug devel- sion every 2-3 months, should be opment is based on the translation added to standard therapy for into biochemical pharmacology patients with relapsed or refracto- of specific alterations of biologi- ry follicular lymphoma after suc- cal functions affecting tumour cessful induction therapy, to cells1. One of the most important improve progression-free and examples is imatinib: it showed overall survival. In contrast, pre- that it was possible to nullify the viously untreated patients seem pathognomic genetic lesion of not to acquire the same benefit chronic myelogenous leukemia from the maintenance treatment (CML). Drugs targeting unique (i.e. it prolongs the time to pro- disease-specific pathways have gression but does not prolong sur- also found potential applicability vival).12-13 in treating malignancies such as The data recently showed at CD20-positive non-Hodgkin’s 2008 ASH Meeting, coming from lymphoma (rituximab), follicular the clinical phase III studies lymphoma (Bcl-2-targeted named CLL8 and REACH, defi- agents2-6) and other B-cell neo- nitely support the employment of plasms (splenic tyrosine kinase rituximab in addition to chemo- [Syk] inhibitors;7-9 IkB kinase therapy (the standard regimen inhibitors10). being fludarabine plus cyclo- Rituximab, whose initial phosphamide) in patients affected employ in treatment of lym- by chronic lymphocytic leu- phomas dates to more than 10 kaemia, (the most common indo- years ago, is perhaps the most lent lymphoproliferative disorder) exploited and well-known “mol- both in first and in second line ecular-targeted” drug in treatment treatment, achieving superiority of indolent lymphoproliferative in terms of progression free sur- disorders. Its use in first-line ther- vival. apy of indolent CD20+ lym- Since rituximab is a chimeric phomas should not be discussed: antibody, there is a need to devel- nowadays, more concerns are op fully humanised antibodies, in about the most effective schedules order to minimise infusion reac- or combination regimens for tions and eliminate the develop- maintenance, above all in follicu- ment of human antibodies against lar lymphoma. A recent meta- the drug itself. In such a perspec-

| 4 | 7th Meeting New Insights in Hematology, Venice, Italy, 26-29 April tive, new anti-CD20 antibodies named ofatu- al antibodies is offered by radioimmunothera- mumab,14 IMMU-106 (hA20),15 and GA10116 py (RIT), combining monoclonal antibodies have been developed and used in treatment of with radionuclides. Two different murine anti- recurrent lymphomas, with promising results CD20 antibodies (Y-90ibritumomab and 131I in phase I/II clinical studies. tositumomab) have been approved for the Further clinical evaluation of antibodies has treatment of rituximab-resistant, relapsed or been largely based on the knowledge of anti- refractory indolent lymphomas. Y-90ibritu- gen expression on the surface of lymphoma momab (Zevalin®) achieved higher ORR and cells and has led to the development of anti- CR rates than rituximab in relapsed/refractory bodies against many surface molecules: CD22 FL, but time to progression (TTP) and duration (unconjugated epratuzumab and calicheamicin of remission (DOR) were not statistically sig- conjugated CMC-544 [inotuzumab ozogam- nificant.22-23 131I tositumomab (Bexxar®) icin]), CD80 (galiximab), CD52 (alemtuzum- achieved ORR of 60-70% in heavily pretreated ab), CD23 (IDEC-152 [lumiliximab]) are the patients.24 Besides its use in treating refractory surface molecules against which monoclonal lymphomas, radioimmunotherapy also seems antibodies have been directed and employed in promising in consolidation approaches after clinical studies with patient affected by indo- chemoimmunotherapy, and it could represent a lent lymphomas and/or CLL. great chance to replace rituximab as mainte- Epratuzumab17 has induced responses in 24% nance treatment in indolent lymphomas. of patients with follicular lymphoma and in So far only in the context of experimental 15% of patients with recurrent diffuse large-B- studies, some murine and humanized forms of cell lymphoma, without dose-limiting toxic anti-CD22 antibodies have also been used con- effects. jugated with different radionuclides, among Galiximab18 achieved positive responses in which Y-90 is the most promising: this kind of 15% of patients affected by recurrent follicular CD22-RIT has been used in 16 patients with non-Hodgkin’s lymphoma, some of which previously treated NHL,25 obtaining an ORR of occurred as late as a year after treatment. 62% (75% in indolent NHL and 50% in Alemtuzumab19-20 has been approved by the aggressive NHL) with 25% CR/CRu rates. FDA for the treatment of chronic lymphocytic Three weekly infusions were feasible in this leukemia. About 30% of patients with CLL population with minimal toxicity. whose disease progressed after they received Among the best examples of target-therapies alkylating agents and fludarabine have had a in lymphomas, a place is occupied by immuno- response to alemtuzumab. When alemtuzumab toxins, consisting of protein toxins connected is used as the initial therapy in CLL, the to cell binding ligands including monoclonal response rate is about 80%. antibodies and growth factors, have been Lumiliximab21 showed he ability to induce developed for several decades to target hema- apoptosis of CLL cells in vitro; in a phase II tologic malignancies. Protein toxins from trial, CLL patients who received lumiliximab either plants or bacteria are extremely potent and FCR attained higher response rates (ORR based on their enzymatic inhibition of protein 71%, CR 48% and PR/PRu 23%) than histori- synthesis and induction of apoptosis. Plant cal FCR-only controls. A phase III trial com- toxins, particularly ricin, are useful for chemi- paring FCR with and without lumiliximab is cally conjugating to monoclonal antibodies, ongoing. and have shown clinical activity in several A chance to improve the effect of monoclon- types of lymphoma and leukemia; unfortunate-

Hematology Meeting Reports 2009;3(3) | 5| G. Saglio et al. ly, their dose is generally limited by the possi- stantial clinical benefit.35 ble onset of vascular leak syndrome. In addition to proteasome inhibitors, the Denileukin diftitox26(the only approved drug immunomodulatory drugs (IMiDs), such as containing a protein toxin) has shown efficacy lenalidomide, have the potential to improve in cutaneous T-cell lymphoma, chronic lym- outcomes for patients with NHL. These drugs phocytic leukemia, and non-Hodgkin's lym- inhibit cell growth and proliferation by several phoma. Recombinant immunotoxin BL2227 is mechanisms, including blocking the effect of an anti-CD22 Fv fragment fused to truncated growth factors and stimulating T cells and nat- Pseudomonas exotoxin; it induces complete ural killer cells.36-37 Lenalidomide is particular- remissions in a high percentage of patients ly effective in lymphoproliferative disorders with chemoresistant hairy cell leukemia. such as multiple myeloma, and it is active in Proteasome inhibitors are an exciting class patients with various forms of NHL, with a of agents that have been used in multiple favourable side-effect profile. The most inter- myeloma and mantle cell lymphoma. esting results seem to be achieved if employed Proteasome inhibitors disrupt the pathways in mantle cell lymphoma, with a high response involved in the pathogenesis of non-Hodgkin’s rate reached even in patients with relapsed or lymphoma, and preclinical models showed refractory disease.38 Complimentary clinical sensitivity in lymphoma cell lines to protea- and pharmacological features suggest that some inhibitors.28-29 Bortezomib and carfil- lenalidomide may be effective when com- zomib are currently under study for indolent bined with monoclonal antibodies. Ongoing lymphomas.30-33 A 2006 study by de Vos and and future studies will provide further infor- colleagues compared weekly and twice-week- mation. ly schedules of bortezomib in combination During the past several decades, understand- with rituximab in a group of patients who were ing the many complex pathways of cell sur- sensitive to rituximab.34 Eighty-six percent of vival provided a fertile arena for formulating the patients had follicular lymphoma. new strategies to target these pathways in Toxicities differed between the two arms, with human cancer. It was demonstrated (1) the the twice-weekly arm experiencing more grade existence of pro- and anti-apoptotic relatives 3 adverse events (54% vs. 35%), but the out- of Bcl2 which, through specific interactions, comes were similar. However, without a ritux- modulate the balance of pro- and anti-apoptot- imab-alone arm, it is hard to determine the ic fates; (2) the existence of at least two dis- degree to which the bortezomib is contributing tinct pathways leading to apoptosis in mam- to these response rates. As there is not yet a malian cells, one involving the mitochondria good control population for the patients who (the intrinsic pathway) and other involving have relapsed follicular lymphoma, this com- cell-surface death receptors (the extrinsic path- bination is now in a randomized trial compar- way). ing combination bortezomib and rituximab to The fruit of the research on Bcl-2 and its rituximab alone. kinases have led to new therapeutic strategies, Nowadays, bortzomib as single-agent thera- some of which have been tested in clinical tri- py seems even more powerful in treating als in humans. patients with relapsed or refractory mantle cell The first of these is an antisense oligonu- lymphoma, achieving lengthy responses and cleotide targeting Bcl-2 mRNA, Oblimersen:39-40 notable survival, with considerable TTP and it downregulates BCL-2 in a concentration- TTNT in responding patients, suggesting sub- and time-dependent manner. It showed an anti-

| 6 | Hematology Meeting Reports 2009;3(3) 7th Meeting New Insights in Hematology, Venice, Italy, 26-29 April tumor efficacy in CLL patients especially in a first generation inhibitor named ABT-737 association with chemotherapy (fludarabine did); ABT-263 was administered orally in both plus cyclophosphamide) with higher CR and indolent and aggressive lymphomas: some PR and prolonged time to relapse. Superior patients achieved a significant tumour volume benefits were obtained in chemosensitive reduction.47 patients’ group.41 Another way to stimulate the apoptosis is the Obatoclax mesylate (GX-15-070) is a pan activation of extrinsic pathways through the Bcl-2 inhibitor: it inhibits several anti-apoptot- development of TRAIL receptor agonists. ic BCL-2 family proteins including Bcl-XL, These effective agents are antibodies targeting Bcl-2, Bcl-W, Bcl-B, A-1 and MCL-1, and has DR4 (mapatumumab48) and DR5 (lexatumum- got a pro-apoptotic function through activa- ab49) proteins, that induce apoptosis in cancer tion of BAX and BAK. It induces apoptosis in cells but not in normal cells. Antibodies have human CLL cells treated ex-vivo and has an the advantage of a long half-life and addition- additive effect in association with fludarabine al mechanism for cell-killing through anti- and chlorambucil. Dose limiting toxicities body-dependent cellular cytotoxicity and com- were neurological and temporally associated plement-dependent cytotoxicity. In a phase II with drug infusion.42-43 study with mapatumumab in relapsed and Gossypol (AT-101) is an orally available refractory NHL relevant clinical responses compound, which binds to the BH3-binding were reported, including a CR reached in a grooves of Bcl-2, Bcl-XL and MCL-1, dis- patient affected by follicular lymphoma.50 placing BH3-peptides. It promotes an A plethora of novel small molecules, each of allosteric conformational change in Bcl-2 and them with its own distinct pharmacology, rep- loss of mitochondrial membrane potential in a resents a potentially important strategy for BAX/BAK-independent way.44 Gossypol modulating the threshold required to induce induces cytochrome c release from mitochon- programmed cell death, in synergy with other dria and activation of several caspase. Its abil- DNA-damaging agents, and it offers now a ity to improve the efficacy of a combination promising chance to cure some patients with chemotherapy regimen (CHOP) in xenograft lymphoproliferative disorders. models of lymphoproliferative disorders has been recently demonstrated.45 Other compounds can induce a phenotypic References conversion that turns Bcl-2 into a pro-apoptot- 1. Paoluzzi L, Kitagawa Y, Kalac M, et al. New drugs for the treatment of lymphoma. Hematol Oncol Clin North ic protein, by binding to a large unstructured Am 2008;22:1007-35. loop between the Bcl-2 BH3 and BH4 2. Oltvai ZN, Milliman CL, Korsmeyer SJ. Bcl-2 het- erodimerizes in vivo with a conserved homolog, BAX, domains. One of these compounds mimics the that accelerates programmed cell death. Cell 1993;74: 609-19. NUR77 (nuclear receptor) activity on Bcl-2 3. Adams JM, Cory S. The Bcl-2 apoptotic switch in cancer and consists in a 9 amino-acid peptide, named development and therapy. Oncogene 2007;26:1324-37. 4. Kang MH, Reynolds CP. Bcl-2 inhibitors: targeting mito- NuBCP-9. The conformational change in Bcl- chondrial apoptotic pathways in cancer therapy. Clin Cancer Res 2009;15:1126-32. 2 interferes with the binding and sequestering 5. Huang DC, Strasser A. BH3-only proteins-essential ini- of BH3-only proteins, turning them into BH3- tiators of apoptotic cell death. Cell 2000;103:839-42. 6. Sattler M, Liang H, Nettesheim D, et al. Structure of Bcl- like proteins that inhibit anti-apoptotic peptide XL-BAK peptide complex: recognition between regula- 46 tors of apoptosis. Science 1997;275:983-6. Bcl-XL inducing a BAX/BAK-via apoptosis. 7. Turner M, Schweighoffer E, Colucci F, et al. Tyrosine ABT-263 also binds with high affinity to kinase Syk: essential functions for immunoreceptor sig- naling. Immunol Today 2000;21:148-54. several anti-apoptotic Bcl-2 family proteins (as 8. Rinaldi A, Bertoni F. Genomic and expression profiling

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phase I trial of the small molecule pan-Bcl-2 family study evaluating the safety, pharmacokinetics, and effica- inhibitor obatoclax mesylate (GX15-070) administered cy of ABT-263 in subjects with refractory or relapsed by 24 hour infusion every 2 weeks to patients with lymphoid malignancies. Blood (ASH Annual Meeting myeloid malignancies and chronic lymphocytic leukemia Abstracts) 2007;110:1371. (CLL). Blood (ASH Annual Meeting Abstracts) 48. Moretto P, Hotte SJ. Targeting apoptosis: preclinical and 2006;108:2654. early clinical experience with mapatumumab, an agonist 44. Lei X, Chen Y, Du G, et al. Gossypol induces monoclonal antibody targeting TRAIL-R1. Expert Opin BAX/BAK-independent activation of apoptosis and Investig Drugs 2009;18:311-25. cytochrome c release via a conformational change in Bcl- 49. Maddipatla S, Hernandez-Ilizaliturri FJ, Knight J, 2. FASEB J 2006;20:2147-9. 45. Kitada S, Kress CL, Krajewska M, et al. Bcl-2 antagonist Czuczman MS. Augmented antitumor activity against B- apogossypol (NSC736630) displays single-agent activity cell lymphoma by a combination of monoclonal antibod- in Bcl-2-transgenic mice and has superior efficacy with ies targeting TRAIL-R1 and CD20. Clin Cancer Res less toxicity compared with gossypol (NSC19048). 2007;13(15 Pt 1):4556-64. Blood 2008;111:3211-9. 50. Younes A, Vose JM, Zelenetz AD, et al. Results of a 46. Kolluri SK, Zhu X, Zhou X, et al. A short Nur77-derived phase 2 trial of HGS-ETR1 (agonistic human monoclon- peptide converts Bcl-2 from a protector to a killer. al antibody to TRAIL receptor 1) in subjects with Cancer Cell 2008;14:285-98. relapsed/refractory non-Hodgkin’s lymphoma (NHL). 47. Wilson WH, Tulpule A, Levine AM, et al. A phase 1/2a Blood (ASH Annual Meeting Abstracts) 2005;106:489.

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