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Immune therapies for malignant mesothelioma Expert Review of Anticancer Therapy Downloaded from informahealthcare.com by Virginia Commonwealth University on 03/15/15 For personal use only.

Expert Rev. Anticancer Ther. 14(8), 965–973 (2014)

Sabina Antonela Antoniu*1, Gabriel Dimofte2 and Didona Ungureanu2 1 Palliative Care-Interdisciplinary Department, Faculty of Medicine, University of Medicine and Pharmacy “Grigore T Popa”, 16 Universitat¸ii Str, 700115, Ias¸i, Romania 2 Faculty of Medicine, University of Medicine and Pharmacy “Grigore T Popa”, 16 Universitat¸ii Str, 700115, Ias¸i, Romania *Author for correspondence: [email protected]

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Malignant mesothelioma (MM) is a rare disease which can develop in pleura, pericardium or peritoneum and in which the therapies available have limited efficacy and are associated with various side effects. Therefore, there is a need for more targeted and more effective therapies which are able to halt the disease progression. Among them immune therapies actively or passively directed against various structures of the MM cells seem to be particularly promising given their inhibitory potential demonstrated in both experimental and early clinical studies. Mesothelin in particular seem to be not only a biomarker of disease activity but also a therapeutic target. This review discusses the immune therapies currently investigated for MM. KEYWORDS: antibodies • immunotoxin • mesothelin • mesothelioma • vaccines

Malignant mesothelioma (MM) is a rare form of neoplasia, which is more prevalent in men and arising from the mesothelial cells of pleura, pericardium or peritoneum. Its development is most commonly linked to asbestos or to erionite occupational exposures in men, whereas in women, it has an ‘idiopathic etiology’ [1]. Its prevalence as well as its mortality is reported to increase constantly worldwide: in 2006, MM was the cause of more than 3000 deaths per year in the USA and for more than 5000 per year in Europe [1,2]. The most common form of MM is represented by pleural mesothelioma, which is due to the inhalation of asbestos fibers. MM has a long and variable latency period until it becomes florid and can belong to one of the three major histopathological subtypes: epithelioid, sarcomatoid and biphasic, the former being the most commonly diagnosed pattern [3]. Combined chemotherapy regimens, radiotherapy or surgery are the therapeutic methods currently available for MM, but most commonly because of the tumor extension, these cannot be applied on individual basis and consequently multimodal approaches involving either two or all three methods are used. Among the chemotherapy agents used, pemetrexed, gemcitabine and cisplatin are the most commonly used, and pemetrexed and cisplatin combination was found to be associated with a survival rate superior to that obtained with cisplatin alone [4]. However, especially in more advanced forms of disease, these methods are of limited value in 10.1586/14737140.2014.919859

stopping the disease progression, and this partly explains the high mortality rate associated with this neoplasia. Therefore, in this setting there is a high unmet therapeutic need and sustained efforts should be streamed toward development of other, more effective therapies. Identification of various immune and nonimmune therapeutic targets for MM led to the discovery of novel therapeutic approaches of which the so called immune therapies seem to be of particular interest. This review discusses these therapies and their stage of development and offers a prospective analysis of their therapeutic potential. Mesothelin: its role as a therapeutic target

Mesothelin is a glycoprotein that is overexpressed in various forms of cancers such as pancreatic, ovarian or MM (epithelioid subtype), all of them having in common a highly invasive potential and a poor prognosis. In MM, in particular, it is the biomarker most extensively studied for its ability to quantify the disease-related activity [5]. More recently, it was also demonstrated that mesothelin is also deeply involved in the disease pathogenesis and progression, the most relevant being its interaction with the CA125, which is responsible for tumor expansion [6]. Mesothelin is a mediator in a complex pathogenic pathway, which also involves the upregulation of various immune tumorigenic mechanisms and downregulation of the inhibitory counterparts. Such


2014 Informa UK Ltd

ISSN 1473-7140

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findings support the role of mesothelin as a therapeutic target and explain why various investigational approaches under development for MM are directed against this molecule. Among the immune approaches aimed to target this protein, the antimesothelin antibodies such as amatuximab are in the most advanced phase of clinical development, whereas mesothelin-specific vaccines are evaluated either experimentally or in earlier clinical phase studies. Antibodies

The development of antimesothelin antibodies was initially planned to help the diagnosis of mesothelin-positive cancer. Subsequently, when the role of this molecule in the pathogenesis spread and therapy refractoriness of such cancers were better documented, these antibodies were seen as potential new therapies especially for MM. Antimesothelin antibodies

Amatuximab (MOR-Ab009) is a chimeric IgG1 antibody, which was initially developed as a murine variant in mice. The chimeric structure has a structural similarity of 82.6% with the human antimesothelin antibody [7–9]. The in vitro binding studies showed that in mesothelinpositive cells A431-K5 (epidermoid carcinoma-derived cells), pancreatic or ovary carcinoma cells or in MM cells, amatuximab was able to bind mesothelin, and that the binding was more significant in more differentiated malignant cells [7]. The cytotoxic activity of amatuximab was evaluated in mesothelin-positive cells such as OVCAR-3 cells and NCIH226 and was found to be higher for the second cell line (10.05 as compared with 3.27) and to marginally involve complement activation [7]. Another in vitro effect of amatuximab, which was subsequently speculated in its development for cancers expressing the CA125 antigen, was the ability of this antibody to block the CA125/MUC16 adhesion and cell–cell interaction. This effect is significant at amatuximab level of at least 10 ng/ml, and the effect may be relevant in CA125-expressing tumor metastasis [7]. The tumoricidal effects of amatuximab were evaluated in vivo in mouse engrafted with the A431-K5 tumor cells in comparison with control IgG (rituximab), gemcitabine 80 mg/kg, paclitaxel 50 mg/kg or amatuximab + gemcitabine or amatuximab + paclitaxel. These combinations were found to be superior to amatuximab monotherapy, which in its turn was superior to the control IgG [7]. In another mice model (athymic mice engrafted with the same tumor cells), the most significant and persistent tumor regression was obtained with amatuximab + gemcitabine combination which was found to be superior to amatuximab alone and to the control IgG (p < 0.001). Tumor rebound growth was detected by day 28 with amatuximab + gemcitabine combination [7]. Subsequently, the amount of conjugation of this antibody was found to inversely influence its immunoreactivity and the tumor uptake in mice model of A431/K5 engrafted tumors 966

and to directly correlate with the liver and spleen antibody uptake. The effect of various dosages (0.2, 2 and 30 mg) of the most immunoreactive (with the highest binding affinity) antibody variant (2.4 CHX-A/MORAb-009) on tumor mesothelin shedding was evaluated and found to depend on antibody dosage and on tumor size: the highest (30 mg) dosage was associated with the highest inhibitory effect on mesothelin shedding and with the lowest spleen and liver uptake compared with both lower dosages (0.2 and 2 mg) and with a smaller tumor size [10,11]. Preclinical safety studies performed in mice and in cynomolgus monkeys demonstrated that the antibody exhibited no crossreactivity with the normal mesothelin-positive cells in mice but did bind to mesothelia in cynomolgus monkeys [7]. Toxicokinetic studies performed again in monkeys using two different dosages 2 mg/kg and 15 mg/kg, respectively, found a Cmax of 130–137 mg/ml for the lower dosage and 750–1170 mg/ml for the higher dosage, whereas Tmax was 482–530 h and 386–442 h, respectively. Amatuximab detectable levels could be identified up to 1224 h after the first dosing [7]. Amatuximab is currently evaluated in Phase II studies in various mesothelin-positive advanced cancers and is an orphan drug in the USA and EU for MM [12]. The first Phase I, dose escalation study was conducted in 24 patients with various forms of mesothelin-positive cancers including eight with MM who were unresponsive to the conventional cytotoxic therapy, had a life expectancy of at least 3 months, an Eastern Cooperative Oncology Group (ECOG) score of no more than two and evaluable tumor activity or symptoms related to the tumor [13,14]. Amatuximab was given as a weekly 30-min intravenous infusion. The cycle consisted of four infusions, and cycle repetition was allowed after a 2 week pause, if no therapeutic response and no adverse event were found after the previous one. Dosages of 12.5, 25, 50 and 100 mg/m2 were each given in one patient, whereas 200 and 400 mg/m2 were each given in two patients. In the mesothelioma subset, a variable degree of tumor response was found in six patients, the other two being discontinued from the study due to development of grade 4 elevation of liver enzymes of serum sickness. Serum CA-125 were found to increase as a result of amatuximab therapy, and this finding was concordant with those in other studies and in fact considered as a marker of therapeutic effect, being the result of the inhibition of its coupling with mesothelin [14,15]. The maximum tolerated dose (MTD) was found to be that of 400 mg/m2 and was associated with two dose-limiting toxicities (DLTs): one in a male with mesothelioma, consisting of the hepatic toxic effect mentioned above, and one in a female with peritoneal mesothelioma who developed serum sickness [13]. In the whole sample, a number of seven drug-related adverse events were found: one was an allergic reaction, four were infusion-related reactions, two episodes of grade 1 and 2 episodes of grade 2 of flushing were detected up to 48 h from an amatuximab infusion (three after the first or second infusion, and one after the fourth infusion). No drug discontinuation was necessary in these patients, Expert Rev. Anticancer Ther. 14(8), (2014)

Immune therapies for MM

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Table 1. Monoclonal antibodies evaluated in clinical studies for malignant mesothelioma therapy. Name

Therapeutic target

Development stage

Clinical data in MM patients

Amatuximab (MorAb009)

Mesothelin

Phase II

Progressionfree survival was 52%

GC1008

TGF-b

Phase II

Disease stabilization in patients with pleural mesothelioma, no effect on CD4+, CD8+ or NK cell subsets

Bevacizumab

VEGF-A

Phase III

Modest effect on progression-free survival

Cixutumumab

IGF-1R

Phase II

Not available

Tremelimumab

CTLA-4

Phase II

Progression-free survival of 6.5 months

PF-03446962

ALK-1

Phase II

Sustained stable disease of over 12 months in a patient with MM

BIW-8962

GM-2

Phase I

Not available

Rilotumumab

HGFR

Phase I

Not available

ALK-1: Activin receptor like-kinase 1; CTLA-4: Cytotoxic T lymphocyte-associated antigen 4; MM: Malignant mesothelioma.

and no cytotoxic pleuritis or pericarditis was detected as a result of deleterious antibody effects on normal mesothelia [13]. In terms of pharmacokinetics, Cmax was found to increase in a dose-dependent manner on both days 1 and 22 (7 mg/ml with the 12.5 mg/m2 to 244 mg/ml with 400 mg/m2 on day 1) and the same behavior being detected with the terminal half-lives measured on day 22 (78 h with the 12.5 mg/m2 and 244 h with 400 mg/m2) [13]. In a subsequent Phase II study, the efficacy and safety of amatuximab were investigated in 89 patients with MM in combination with pemetrexed and cisplatin. Amatuximab was given at a dosage of 5 mg/kg on days 1 and 8, whereas pemetrexed and cisplatin were given at a dosage of 500 mg/m2 and 75 mg/ m2, respectively, on day 1, all being given for six consecutive 21 days cycles. In patients in whom after this period tumor regression or stable disease was achieved, amatuximab monotherapy was then given until the earliest signs of disease progression were detected. The primary endpoint was progressionfree survival, while overall survival, objective response rate and safety were the secondary endpoints. In a total of 77 patients with interpretable results, a partial response rate of 39% was detected, whereas disease stabilization was found in 51% patients. The progression-free survival rate was 52% after 6 months, whereas the median progression-free survival was comparable to that associated with pemetrexed or with cisplatin alone and was 6.1 months. The overall median survival was 14.5 months, which was superior to those found with the above-mentioned cytotoxic agents. Amatuximab hypersensitivity developed in 12.4% of patients and was severe (grade 3 or 4) in about 4.5% of the patients [16]. Another antimesothelin antibody is represented by BAY-94-9343, which is a fully human antibody with potent cytotoxic effects resulting from its conjugation with a maytansine derivative called DM4 known to inhibit cell division by binding the intracellular tubulin [17]. SD1, a human single domain antimesothelin antibody formulated as a recombinant human Fc fusion protein, is informahealthcare.com

currently investigated in mesothelioma-positive cells for its potent cytotoxic activity, which is not only due to the antibody-mediated mechanism but also due to its potential to activate the complement pathways [18]. HN1 is a human antibody immunotoxin hybrid component, which demonstrated its high binding affinity to mesothelin, its ability to inhibit its interaction with the CA-125 antigen and its superior cytotoxic potential due to the synergic effects of antibody and immunotoxin-mediated cytotoxicity [19]. 22A31 is a mouse monoclonal antibody against C-ERC/mesothelin, which is currently evaluated in experimental studies: in vivo in an athymic nude mice model bearing human mesothelioma xenograft, it was found to potently inhibit tumor growth via an antibody-dependent cell-mediated cytotoxic effect involving natural killer cells [20,21]. M912 is claimed to be the first human anti-mesothelin antibody of IgG type with good binding affinity and potent cytotoxic effect demonstrated in vitro [22]. Other antibodies

Other antibodies targeting various structures are currently under investigation as potential immune therapies for MM (TABLE 1). They are directed to molecules involved in angiogenesis or to structures involved in inhibition of cell apoptosis, and most of them are in early phases of clinical development. GC1008, for example, was an anti-TGF-b antibody, which was evaluated in an open-label Phase II study in patients with progressive pleural MM after one to two cycles of cytotoxic therapy: GC1008 was given as an intravenous infusion of 3 mg/m2 every 21 days. A number of 13 patients were enrolled when the manufacturer suddenly discontinued this compound from further development for oncological indications [23]. GC1008 was able to stabilize the disease in three patients after 3 months of therapy and was well tolerated. GC1008 therapy resulted in no significant effect on the activity of NK, CD4+ or CD8+ T cell subpopulations. In five patients, antibodies against tumor lysates were found, and their presence was associated 967

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with a significantly increased median overall survival compared to those with no such antibodies (15 compared with 7.5 months, p < 0.03) [23]. Bevacizumab is a monoclonal antibody against VEGF-A, which is currently authorized for solid cancers treatment. In the mesothelioma setting, it was hoped that it could be used in advanced stages in addition to the cytotoxic therapy, in order to slow the tumor expansion. However, in Phase II studies, when added to gemcitabine/cisplatin or to pemetrexed/cisplatin, it failed to meet the primary endpoint, which was the progression-free survival [24,25]. Monoclonal antibodies targeting the EGFR such as cetuximab, panitumumab and trastuzumab are of particular benefit in solid cancers including non-small-cell lung cancer. In the MM setting, their evaluation as potential therapies is supported by the demonstration of the EGFR upregulation in pleural mesothelioma cells [26,27]. Cixutumumab (IMC-A12) is a human monoclonal IgG against the IGF-1 receptor, which is currently assessed in various forms of solid cancers [28,29]. In MM, it is currently evaluated in Phase II studies, but the experimental results suggest that its efficacy depends on the expression of the target receptor, which is not uniform in all patients with this form of malignancy [28]. Tremelimumab is a monoclonal antibody against cytotoxic T lymphocyte-associated antigen 4, which is currently under evaluation in Phase II studies in patients with MM, based on its ability to disinhibit the tumoricidal effects of activated CD8+ lymphocytes [30]. In a Phase II study performed in patients with advanced MM, who failed to the first cisplatinbased cycle but still have a good ECOG score, tremelimumab 15 mg/kg infused every 90 days until disease progression or severe adverse events was given in 29 patients. In this study, it failed to result in any complete response but induced an acceptable disease control in nine (31%) patients, an overall survival of 10.7 months and a progression-free survival of 6.2 months [31]. PF-03446962 is a human monoclonal antibody against activin receptor-like-kinase 1, which is the TGF-b receptor. PF-03446962 is investigated as a potential antiangiogenic therapy. Preclinical studies demonstrated that the antiangiogenic effects were exerted via a VEGF-independent pathway [32]. In MM, it is currently investigated in Phase II studies and in a Phase I study performed in 44 patients, with various forms of solid malignancies. A dose of 6.75 mg/kg was the dose to be put forward in Phase II studies based on the pharmacokinetics data derived from this study. Sustained stable disease for about 12 months was reported in a patient with MM [32]. In MM, another interesting therapeutic target is represented by ganglioside GM2, which is considered to play an important role in tumor metastasis [33]. BIW-8962 is a humanized antiGM2 monoclonal antibody, which is currently evaluated in clinical trials in small cell lung cancer and MM, based on the previous demonstration of the antitumor effects of the chimeric antibody in experimental studies [33]. 968

Rilotumumab (AMG-102) is a human monoclonal antibody against hepatocyte growth factor, which is currently investigated in clinical studies in advanced solid tumors including the idiopathic peritoneal cancer. The ability of rilotumumab to induce apoptosis in sarcomatoid cells is worth being further investigated and might be of a particular value for this MM subtype [34]. Fusion proteins

Another immune therapy approach in cancers is represented by the fusion proteins class: these are compounds in which a single-chain antibody conjugated with the therapeutically active or with another therapeutically active moiety that are able to exert their cytotoxic effect upon antibody chain binding to the cell surface. The most relevant example in the mesothelioma setting is represented by the SS1P immunotoxin, but other similar therapies are currently under investigation for the same therapeutic indication. Given the fact that in MM, mesothelin is the most commonly expressed cell biomarker, it is then plausible to develop such fusion proteins with antimesothelin antibodies as structures aimed at ensuring the intracellular penetration of the tumoricidal agents. SS1P

SS1P (CAT-5001) is a potent recombinant immunotoxin, which initially was planned to be developed as a single agent for the therapy of various cancers including mesothelioma. Early studies to evaluate the cytotoxic effects of immunotoxins on mesothelin-expressing cancer cell lines used a SS1P precursor comprising a murine monoclonal IgG1 antimesothelin antibody (K1) conjugated with LysPE38QQR, which was found to induce a ‘specific, mesothelin-related apoptosis’ in A431-K5 cells at an IC50 of 3–6 ng/ml and complete tumor regression when the same cell line was engrafted in nude mice. This immunotoxin showed signs of negligible effect in A431 cell lines, which do not express mesothelin [35]. However, it was found that despite showing good tumoricidal efficacy, it was also able to rapidly elicit immunogenicity. In order to reduce this risk and to augment the tumoricidal effects, it was subsequently assessed in combination with cytotoxic agents such as gemcitabine, pemetrexed or cyclophosphamide [7,36]. SS1P is derived from the Pseudomonas aeruginosa exotoxin, in which an anti-mesothelin antibody single-chain variable fragment is conjugated with PE38, a truncated exotoxin component that is able to produce apoptosis by inhibiting protein synthesis [37]. It binds the mesothelin-expressing cells via the antibody component, and this allows the toxin to subsequently kill the cells. In preclinical studies, SS1P was found to induce apoptosis in both in vitro and in vivo experiments [37]. In vitro, SS1P was found to exert a dose-dependent cytotoxic effect on mesothelin-expressing human ovary cancer or peritoneal mesothelioma cell lines, the IC50 being 1 ng/ml for the former cells line and varying from 0.08 to 3.9 ng/ml for the latter [38]. In vivo, in an athymic nude mice model of mesothelinexpressing xenografted tumor, SS1P in all three doses tested, that is, 4, 6 and 8 mg produced complete tumor regression [39]. Secondary Expert Rev. Anticancer Ther. 14(8), (2014)

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Immune therapies for MM

tumor inhibition was also reported in another model of lung metastases containing mesothelin-positive NCI-226 cells [39]. SS1P was subsequently evaluated in Phase I dose escalation clinical studies either as alternate day or as continuous infusion regimen [40]. In the first study, 34 patients, most of them having advanced mesothelioma (n = 20), received either a 30-min infusion every other day for six infusions (n = 17) or for three infusions (n = 17) [40]. The MTD was 18 mg/kg/dose for the first schedule, and DLTs included grade 3 urticaria (one patient) or vascular leak syndrome (two patients), whereas for the second schedule, the MTD was 45 mg/kg/dose and was associated with a grade 3 pleuritis in two patients receiving 60 mg/kg and in no patients receiving the MTD [40]. Minor therapeutic response was found in 4 patients, stable disease in 19, and disease progression in 10 patients. In the second study, SS1P was given as cycles of 30-min daily infusions of 4, 8, 12 and 25 mg/kg/day for 10 days with another cycle given after 4 weeks of the therapy if no immunogenicity or progressive disease was reported in 24 patients (n = 11 with mesothelioma) [41]. The MTD was 25 mg/kg/day, and the DLT was found in one patient and was represented by vascular leak syndrome. Immunogenicity was reported in 18 (75%) patients, and in 5 patients, a second cycle could be given. SS1P achieved a constant plasma concentration over 10 days, with median peak levels of up to 153 ng/ml. Partial therapeutic response was found in one patient, and other signs of disease regression such as absence or reduction of ascites, pain amelioration or tumor mass shrinkage were also detected [41]. The subsequent studies were performed with cytotoxic agent – SS1P combination based on the assumption of therapeutic synergy: this was initially proven in an experimental study, which demonstrated that the molecular basis of this synergy could be represented by the ability of Taxol to reduce the expression of mesothelin by the cancer cells (actually to kill a good proportion of such cells) to the ‘right’ amount SS1P is able to neutralize [42,43]. Furthermore, the proof of concept for the ability of cytotoxic agents to reduce the risk of immunogenicity was backed up by the results of various experimental studies using pentostatin + cyclophosphamide combination, gemcitabine or Taxol [7,36,44,45]. Pentostatin + cyclophosphamide was able to reduce significantly the immunogenicity produced by the pretreatment with SS1P [36]. In the other study performed in vitro and in an animal model of mesothelin-positive tumors: in vitro the combined gemcitabine–SS1P therapy was not able to produce a superior apoptosis in the A431/K5 cell line, whereas in vivo, in mice grafted with the same cells both concomitant or sequential SS1P–gemcitabine regimens were able to induce a sustained tumor regression [7]. In the studies using Taxol, it was found that its addition to SS1P was able to reduce the mesothelin shedding and to improve its intracellular penetrability in Taxol-sensitive tumors [44,45]. In a Phase I study, SS1P was also assessed in combination with pemetrexed and cisplatin in patients with pleural MM of Stage III/IV and having an ECOG performance scale of not informahealthcare.com

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more than two. Investigational treatment was represented by six cycles of pemetrexed 500 mg/m2, cisplatin 75 mg/m2 given on the first day of the 3 week cycle, SS1P being given in escalating doses of 25, 35, 45 and 55 mg/kg on days 1, 3 and 5 for the first two cycles. Tumor regression was assessed every 3 months with the modified RECIST criteria. An analysis done on 12 patients was presented: five patients received the lowest SS1P and two of them withdrew after the first cycle, three patients received 35 or 45 mg/kg and one 55 mg/kg. A patient who received the highest dose experienced grade 3 fatigue, and this was labeled as a DLT. Other SS1P-related toxicities included grade 3 or 2 hypoalbuminemia (three or five patients, respectively), grade 3 or 2 pain (two patients), edema (three patients) and fatigue (six patients). Partial response was detected in five patients (response duration ranging 4–10 months), two had stable disease (response duration 4–18 months) and three had progressive disease. Among the dosages assessed, 45 mg/kg was associated with a 100% partial response rate [46]. In patients with chemotherapy-resistant mesothelioma, addition of pentostatin and cyclophosphamide resulted in significant tumor regression (in 3 out of 10 patients) as well as in delayed anti-immunotoxin antibody formation [47]. Other means to improve the cytotoxic potential of the SS1P were more recently explored, and these consisted of the reengineering of the PE38 toxin component to become less immunogenic and less toxic on the endothelial cells (vascular leak syndrome), or SS1P combinations with tyrosine kinase inhibitors or protein kinase inhibitors [48–50]. The reengineered SS1-LR/GGS/8M showed superior antitumor activity in human mesothelioma primary cells, whereas in vivo, in a mouse xenograft mesothelin-positive tumor, this compound was able to elicit a tumor regression effect which was superior to that induced by the MTD of the parent component. It also showed less likelihood to induce vascular leak syndrome and less reactivity with the anti-immunotoxin antibodies developed in patients as a result of the previous SS1P exposure [49]. Combination of SS1P with a tyrosine kinase inhibitor (SU6656) or with Src inhibitor (SKI-606) increased the cytotoxic potential of the immunotoxin in vitro, in mesothelin-expressing cells [48]. A protein kinase inhibitor, enzastaurin was found to act in a synergistic manner with the SS1P on cell apoptosis [50]. Another fusion protein is the recombinant IL12SS1Fv in which the binding component is directed against mesothelin, whereas IL-12 exerts potent tumoricidal effects as demonstrated in vitro on NCI-H226 cell line and in vivo in a mouse model of peritoneal mesothelioma [51]. Another experimental approach performed previously on pancreatic cancer cells consisted of combining the SS1P with TNF-related apoptosis-inducing ligand or with anti-TNFrelated apoptosis-inducing ligand receptor agonist antibody (HGS-ETR2) [52]. A soluble fusion protein consisting of the extracellular domain of human FGF receptor 1 was fused to the Fc portion of human IgG1, with potential antineoplastic and antiangiogenic activities. 969

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Vaccines

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Dendritic cell vaccines

Dendritic cells immunotherapy is currently investigated as a potential anticancer therapy based on their ability to induce a tumor-specific cytotoxic effect as a result of antigen presentation to T cells. Such a therapy (Provenge) is already authorized in the USA for the treatment of refractory prostate cancer [53]. In experimental studies, a vaccine of this type was able to reduce the tumor growth and to improve survival in animals with mesothelioma xenograft [54,55].

adenocarcinomas and in mesothelioma. The viral strain is transfected with the human 5T4 antigen gene, and in preclinical studies, it demonstrated sustained tumoricidal effect involving both cell- and antibody-mediated immune mechanisms [65]. GL-ONC1 is another vaccinia-based vaccine, which was developed from the strain used to prepare the vaccines against the smallpox and demonstrated its immunogenicity in various experimental studies. It is currently evaluated as a topic (intrapleural) therapy in patients with malignant pleural mesothelioma [66]. Nonspecific vaccines

Antimesothelin T lymphocytes vaccines

Antitumor T lymphocytes transduced with the tumor antigen receptor (CAR therapy) became of interest in oncology during the last few years because of its promising therapeutic potential. In experimental studies performed in mesothelin-positive cancers, such a therapy P4 CAR was able to exert targeted cytotoxic effects in vitro and in vivo and unlike other antimesothelin targeted therapies, its efficacy was not negatively influenced by a heavier tumorrelated mesothelin load [56,57]. Granulocyte macrophage colony-stimulating factor vaccines

These vaccines were developed in order to enhance the immunomodulatory properties of such therapies using the granulocyte macrophage colony-stimulating factor (GM-CSF). One such type of vaccine involves the use of irradiated autologous tumor cell lines transduced with the gene encoding for GMCSF and is evaluated in Phase II clinical studies for MM as well as for other mesothelin-positive cancers [58,59]. A previous clinical study using a vaccine made of a mixture of tumor cells lysate and GM-CSF was able to elicit a cell-mediated immune response upon administration in the patients from whom the cells were retrieved [60]. Listeria monocytogenes vaccines

CRS-207 is a vaccine made out of a L. monocytogenes attenuated strain expressing mesothelin, which is currently evaluated in Phase II studies in various types of mesothelin-positive cancers, based on its ability to activate both innate and adaptive immune mechanisms in a streamed manner against the expressed antigen [61,62]. Wilms tumor gene-1 vaccines

Wilms tumor gene 1 is a transcription factor that is overexpressed by the MM cells and is a therapeutic target of the Wilms tumor gene 1 polyvalent peptide vaccine. In a Phase I study performed in patients with advanced mesothelioma, this was able to safely elicit a complex immune response based on antigen-specific polyclonal CD4+ and CD8+ cells proliferation and activation [63,64]. It is currently evaluated in Phase II study as an immune therapy booster given at the end of conventional therapy cycle. Vaccinia vaccines

TroVax is an attenuated viral (Vaccinia Ankara) vaccine, which is investigated as an adjuvant to the chemotherapy in 970

DetoxPc is an antigenic mixture made of the lipid A derived from Salmonella minnesota and of cell wall components from Mycobacterium phlei, which is supposed to boost the immune antitumor mechanisms in a nonspecific manner in patients with malignancies. It is currently investigated as an immune adjuvant in patients with MM who are concomitantly receiving chemotherapy agents. Expert commentary & five-year view

MM is a rare disease with high unmet therapeutic need. The existing pharmacologic therapies consisting of chemotherapy agents are more effective in earlier forms of diseases, but in a small proportion of patients. In more advanced stages, therapy refractoriness is common and contributes to a dramatic reduction in survival and in quality of life. Therefore, the efforts toward the development of newer, more effective therapies are justified. Such therapies can be other chemotherapy agents with new mechanisms of action, more convenient dosing and better safety, or other therapies that are able to specifically boost the immune system of the host to induce tumor regression by augmenting the innate or adaptive tumoricidal pathways. This latter therapeutic category is the one that includes the highest number of investigational therapies and is the one approached in the present review. An important role in this ‘effervescence’ has been due to the detection of mesothelin as a biomarker of tumor activity and as a potential therapeutic target in the same time. This was also fueled by the discovery of other potential targets such as cytokines and tyrosine kinases. Most of these immune therapies are planned to be given in addition to the conventional therapy although ideally the monotherapy would be the preferred method. Antibodies currently under investigation showed a promising efficacy, but the potential immunogenicity risk associated with some of them should be taken into consideration and should be minimized. In the case of vaccines, some of the approaches are spectacular, but the reduction of the immune response with repeated administration might limit their efficacy. Immunotoxins are also interesting compounds, which demonstrated their appropriateness as antibodies did, especially in tumors with refractoriness to conventional therapies, and therefore their effectiveness might be limited in advanced forms of disease. For this last category of patients, the topic immune therapies might work where all the others failed. Such therapies speculate the presence of pleural effusion of ascites that are known to Expert Rev. Anticancer Ther. 14(8), (2014)

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Immune therapies for MM

limit or contraindicate the use of certain chemotherapy agents and might significantly reduce the risk of adverse events associated with systemic exposure to such therapies. In fact, several such therapies are investigated for the pleural subset of MM, and it is hoped that their feasibility can also be extrapolated to the peritoneal subset. Another important issue when developing and evaluating such methods is the fact that mesothelin is highly expressed only by the epithelioid MM subset, which is indeed the most prevalent, but are not able to tackle at all or do it only marginally on the other histological subtypes which may coexist. An immune therapy able to target all MM subtypes would be the most appropriate in this setting and would also have a better potential in terms of financial returns for the manufacturer.

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A monoclonal antibody fulfilling this desiderate is currently assessed experimentally, and it is hoped that it will develop in a promising therapy [67]. Even if their efficacy is not yet conclusive in all cases, immune therapies show promise in the setting of MM and in particular in advanced stages. Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.

Key issues • Malignant mesothelioma (MM) is a rare disease with high unmet therapeutic need because the conventional therapy is not always able to induce a complete and sustained remission. • Consequently, other therapies should be investigated in this disease, and immune therapies are of particular interest. • Some of these therapies are represented by blocking antibodies that can target various molecules such as mesothelin, TGF-b, VEGF-A, EGFR or cytotoxic T lymphocyte-associated antigen 4. • Antimesothelin immune therapies such as amatuximab are in the most advanced stage of clinical development exhibiting promising efficacy. • Fusion proteins can also exert potent antitumor effect in MM, especially if combined with other antitumor therapies such as tyrosine kinase inhibitors or interleukins. • Antitumor vaccines able to elicit immune responses against mesothelin or other tumor antigens are also investigated as potential therapies in MM, and the topic (intrapleural) route of administration for such compounds might be of particular interest in this setting. • Most of such therapies are planned to be given in addition to the conventional therapies. • However, in refractory MM, immune therapies might be given as monotherapies. • Ideal immune therapies should be able to work in all histological subtypes of MM.

References 1.

Carbone M, Ly BH, Dodson RF, et al. Malignant mesothelioma: facts, myths, and hypotheses. J Cell Physiol 2012;227(1): 44-58

2.

Ismail-Khan R, Robinson LA, Williams CC Jr, et al. Malignant pleural mesothelioma: a comprehensive review. Cancer Contr 2006;13(4):255-63

3.

Husain AN, Colby TV, Ordo´n˜ez NG, et al. Guidelines for Pathologic Diagnosis of Malignant Mesothelioma: a Consensus Statement from the International Mesothelioma Interest Group. Arch Pathol Lab Med 2009;133(8):1317-31

4.

Vogelzang NJ, Rusthoven JJ, Symanowski J, et al. Phase III Study of pemetrexed in combination with cisplatin versus cisplatin alone in patients with malignant pleural mesothelioma. J Clin Oncol 2003;21(14): 2636-44

informahealthcare.com

5.

Creaney J, Yeoman D, Naumoff LK, et al. Soluble mesothelin in effusions: a useful tool for the diagnosis of malignant mesothelioma. Thorax 2007;62(7):569-76

6.

Rump A, Morikawa Y, Tanaka M, et al. Binding of ovarian cancer antigen CA125/ MUC16 to mesothelin mediates cell adhesion. J Biol Chem 2004;279(10): 9190-8

7.

Hassan R, Ebel W, Routhier EL, et al. Preclinical evaluation of MORAb-009, a chimeric antibody targeting tumor-associated mesothelin. Cancer Immun 2007;7:20

8.

Smith G. Filamentous fusion phage: novel expression vectors that display cloned antigens on the virion surface. Science 1985; 228(4705):1315-17

9.

Chowdhury PS, Viner JL, Beers R, Pastan I. Isolation of a high-affinity stable single-chain Fv specific for mesothelin from DNA-immunized mice by phage display

and construction of a recombinant immunotoxin with anti-tumor activity. Proc Natl Acad Sci U S A 1998;95(2):669-74 10.

Chopra A. 111In-Labeled CHX-A’’-DTPAconjugated MORAb-009, a chimeric monoclonal antibody directed against mesothelin. In: Zhang H, editor. Molecular Imaging and Contrast Agent Database (MICAD). National Center for Biotechnology Information, Bethesda, MD, USA; 2004

11.

Shin IS, Lee SM, Kim HS, et al. Effect of chelator conjugation level and injection dose on tumor and organ uptake of 111In-labeled MORAb-009, an anti-mesothelin antibody. Nucl Med Biol 2011;38(8):1119-27

12.

Association FaD. Amatuximab Amatuximab. 2012

13.

Hassan R, Cohen SJ, Phillips M, et al. Phase I clinical trial of the chimeric anti-mesothelin monoclonal antibody

971

Review

Antoniu, Dimofte & Ungureanu

MORAb-009 in patients with mesothelin-expressing cancers. Clin Cancer Res 2010;16(24):6132-8

Expert Review of Anticancer Therapy Downloaded from informahealthcare.com by Virginia Commonwealth University on 03/15/15 For personal use only.

14.

15.

16.

17.

18.

19.

Hassan R, Schweizer C, Lu KF, et al. Inhibition of mesothelin– CA-125 interaction in patients with mesothelioma by the anti-mesothelin monoclonal antibody MORAb-009: implications for cancer therapy. Lung Cancer 2010;68(3):455-9 Bertholf RL, Johannsen L, Benrubi G. False elevation of serum CA-125 level caused by human anti-mouse antibodies. Ann Clin Lab Sci 2002;32(4):414-18 Hassan R, Jahan TM, Kindler HL, et al. Amatuximab, a chimeric monoclonal antibody to mesothelin, in combination with pemetrexed and cisplatin in patients with unresectable pleural mesothelioma: results of a multicenter phase II clinical trial. J Clin Oncol 2012; 30(Suppl):Abstract 7030 Bendell J, Blumenschein G, Zinner R, et al. First-in-human phase I dose escalation study of a novel anti-mesothelin antibody drug conjugate (ADC), BAY 94-9343, in patients with advanced solid tumors. Proceedings of the AACR 104th Annual Meeting 2013; 6-10 April 2013; Washington, DC, USA Tang Z, Feng M, Gao W, et al. A human single-domain antibody elicits potent antitumor activity by targeting an epitope in mesothelin close to the cancer cell surface. Mol Cancer Ther 2013;12(4):416-26

Inami K, Abe M, Takeda K, et al. Antitumor activity of anti-C-ERC/ mesothelin monoclonal antibody in vivo. Cancer Sci 2010;101(4):969-74

21.

Ishikawa K, Segawa T, Hagiwara Y, et al. Establishment of novel mAb to human ERC/mesothelin useful for study and diagnosis of ERC/mesothelin-expressing cancers. Pathol Int 2009;59(3):161-6

23.

Feng Y, Xiao X, Zhu Z, et al. A novel human monoclonal antibody that binds with high affinity to mesothelin-expressing cells and kills them by antibody-dependent cell-mediated cytotoxicity. Mol Cancer Ther 2009;8(5):1113-18 Stevenson JP, Kindler HL, Papasavvas E, et al. Immunological effects of the TGFbeta-blocking antibody GC1008 in malignant pleural mesothelioma patients. Oncoimmunology 2013;2(8):e26218

972

Kindler HL, Karrison TG, Gandara DR, et al. Multicenter, Double-Blind, Placebo-Controlled, Randomized Phase II Trial of Gemcitabine/Cisplatin Plus Bevacizumab or Placebo in Patients With Malignant Mesothelioma. J Clin Oncol 2012;30(20):2509-15

(rilotumumab) in the treatment of persistent or recurrent epithelial ovarian, fallopian tube or primary peritoneal carcinoma: a Gynecologic Oncology Group study. Gynecol Oncol 2014;132(3):526-30 35.

Hassan R, Viner JL, Wang Q-C, et al. Anti-Tumor Activity of K1-LysPE38QQR, an Immunotoxin Targeting Mesothelin, a Cell-Surface Antigen Overexpressed in Ovarian Cancer and Malignant Mesothelioma. J Immunother 2000;23(4): 473-9

25.

Dowell JE, Dunphy FR, Taub RN, et al. A multicenter phase II study of cisplatin, pemetrexed, and bevacizumab in patients with advanced malignant mesothelioma. Lung Cancer 2012;77(3):567-71

26.

Favoni RE, Daga A, Malatesta P, Florio T. Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma. Br J Pharmacol 2012;166(2):532-53

36.

Mossoba ME, Onda M, Taylor J, et al. Pentostatin plus cyclophosphamide safely and effectively prevents immunotoxin immunogenicity in murine hosts. Clin Cancer Res 2011;17(11):3697-705

27.

Kindler HL. Systemic treatments for mesothelioma: standard and novel. Curr Treat Options Oncol 2008;9(2-3):171-9

37.

Hassan R, Bera T, Pastan I. Mesothelin: a new target for immunotherapy. Clin Cancer Res 2004;10(12):3937-42

28.

Kalra N, Zhang J, Yu Y, et al. Efficacy of anti-insulin-like growth factor I receptor monoclonal antibody cixutumumab in mesothelioma is highly correlated with insulin growth factor-I receptor sites/cell. Int J Cancer 2012;131(9):2143-52

38.

Hassan R, Lerner MR, Benbrook D, et al. Antitumor activity of SS(dsFv)PE38 and SS1(dsFv)PE38, recombinant antimesothelin immunotoxins against human gynecologic cancers grown in organotypic culture in vitro. Clin Cancer Res 2002;8(11):3520-6

29.

Burtrum D, Zhu Z, Lu D, et al. A fully human monoclonal antibody to the insulin-like growth factor I receptor blocks ligand-dependent signaling and inhibits human tumor growth in vivo. Cancer Res 2003;63(24):8912-21

39.

30.

Ribas A, Hanson DC, Noe DA, et al. Tremelimumab (CP-675,206), a cytotoxic T lymphocyte–associated antigen 4 blocking monoclonal antibody in clinical development for patients with cancer. Oncologist 2007;12(7):873-83

Fan D, Yano S, Shinohara H, et al. Targeted therapy against human lung cancer in nude mice by high-affinity recombinant antimesothelin single-chain Fv immunotoxin 1 supported in part by cancer center support core Grant CA16672 and Grant R35-CA42107 from the National Cancer Institute. NIH.1. Mol Cancer Ther 2002; 1(8):595-600

40.

Hassan R, Bullock S, Premkumar A, et al. Phase I Study of SS1P, a recombinant anti-mesothelin immunotoxin given as a bolus i.v. infusion to patients with mesothelin-expressing mesothelioma, ovarian, and pancreatic cancers. Clin Cancer Res 2007;13(17):5144-9

41.

Kreitman RJ, Hassan R, Fitzgerald DJ, Pastan I. Phase I Trial of continuous infusion anti-mesothelin recombinant immunotoxin SS1P. Clin Cancer Res 2009; 15(16):5274-9

42.

Zhang Y, Xiang L, Hassan R, Pastan I. Immunotoxin and Taxol synergy results from a decrease in shed mesothelin levels in the extracellular space of tumors. Proc Natl Acad Sci U S A 2007;104(43):17099-104

43.

Pak Y, Zhang Y, Pastan I, Lee B. Antigen shedding may improve efficiencies for delivery of antibody-based anticancer agents in solid tumors. Cancer Res 2012;72(13): 3143-52

44.

Hassan R, Broaddus VC, Wilson S, et al. Anti–mesothelin immunotoxin SS1P in

Ho M, Feng M, Fisher RJ, et al. A novel high-affinity human monoclonal antibody to mesothelin. Int J Cancer 2011;128(9): 2020-30

20.

22.

24.

31.

32.

33.

34.

Calabro` L, Morra A, Fonsatti E, et al. Tremelimumab for patients with chemotherapy-resistant advanced malignant mesothelioma: an open-label, single-arm, phase 2 trial. Lancet Oncol 2013;14(11): 1104-11 De Braud F CR, Berlin J, Noberasco C, et al. Phase 1 study of PF-03446962, a fully human mAb against activin receptor-like kinase 1 (ALK 1), a TGFb receptor involved in tumor angiogenesis. Mol Cancer Ther 2011;10(11):A1 Hanibuchi M, Yano S, Nishioka Y, et al. Therapeutic efficacy of mouse-human chimeric anti-ganglioside GM2 monoclonal antibody against multiple organ micrometastases of human lung cancer in NK cell-depleted SCID mice. Int J Cancer 1998;78(4):480-5 Martin LP, Sill M, Shahin MS, et al. A phase II evaluation of AMG 102

Expert Rev. Anticancer Ther. 14(8), (2014)

Immune therapies for MM

combination with gemcitabine results in increased activity against mesothelin-expressing tumor xenografts. Clin Cancer Res 2007;13(23):7166-71

Expert Review of Anticancer Therapy Downloaded from informahealthcare.com by Virginia Commonwealth University on 03/15/15 For personal use only.

45.

46.

47.

48.

49.

50.

51.

52.

Zhang Y, Hansen JK, Xiang L, et al. A flow cytometry method to quantitate internalized immunotoxins shows that taxol synergistically increases cellular immunotoxins uptake. Cancer Res 2010; 70(3):1082-9 Hassan R, Sharon E, Chen HX, et al. Phase I clinical trial of antimesothelin immunotoxin SS1P in combination with pemetrexed and cisplatin for front-line therapy of advanced pleural mesothelioma. J Clin Oncol 2010;28(15):e17518 Hassan R, Miller AC, Sharon E, et al. Major cancer regressions in mesothelioma after treatment with an anti-mesothelin immunotoxin and immune suppression. Sci Transl Med 2013;5(208):208ra147 Liu X-F, Xiang L, Fitzgerald DJ, Pastan I. Antitumor effects of immunotoxins are enhanced by lowering HCK or treatment with SRC kinase inhibitors. Mol Cancer Ther 2014;13(1):82-9 Weldon JE, Xiang L, Zhang J, et al. A recombinant immunotoxin against the tumor-associated antigen mesothelin reengineered for high activity, low off-target toxicity, and reduced antigenicity. Mol Cancer Ther 2013;12(1):48-57 Mattoo AR, Pastan I, Fitzgerald D. Combination treatments with the PKC inhibitor, enzastaurin, enhance the cytotoxicity of the anti-mesothelin immunotoxin, SS1P. PLoS One 2013;8(10): e75576 Kim H GW, Ho M. Novel immunocytokine IL12-SS1 (Fv) inhibits mesothelioma tumor growth in nude mice. PLoS One 2013;8(11):e81919 Du X, Xiang L, Mackall C, Pastan I. Killing of resistant cancer cells with low bak by a combination of an antimesothelin immunotoxin and a TRAIL receptor

informahealthcare.com

2 agonist antibody. Clin Cancer Res 2011; 17(18):5926-34 53.

Vacchelli E, Vitale I, Eggermont A, et al. Trial watch: dendritic cell-based interventions for cancer therapy. Oncoimmunology 2013;2(10):e25771

54.

Mahaweni NM, Kaijen-Lambers MEH, Dekkers J, et al. Tumour-derived exosomes as antigen delivery carriers in dendritic cell-based immunotherapy for malignant mesothelioma. J Extracell Vesicles 2013;doi: 10.3402/jev.v3402i3400.22492

55.

Strioga MM, Felzmann T, Powell DJ Jr, et al. Therapeutic dendritic cell-based cancer vaccines: the state of the art. Crit Rev Immunol 2013;33(6):489-547

56.

Carpenito C, Milone MC, Hassan R, et al. Control of large, established tumor xenografts with genetically retargeted human T cells containing CD28 and CD137 domains. Proc Natl Acad Sci USA 2009;106(9):3360-5

57.

58.

59.

60.

Lanitis E, Poussin M, Hagemann IS, et al. Redirected antitumor activity of primary human lymphocytes transduced with a fully human anti-mesothelin chimeric receptor. Mol Ther 2012;20(3):633-43 Jaffee EM, Hruban RH, Biedrzycki B, et al. Novel allogeneic granulocyte-macrophage colony-stimulating factor–secreting tumor vaccine for pancreatic cancer: a phase I trial of safety and immune activation. J Clin Oncol 2001;19(1):145-56 Borrello I, Sotomayor EM, Cooke S, Levitsky HI. A universal granulocyte-macrophage colony-stimulating factor-producing bystander cell line for use in the formulation of autologous tumor cell-based vaccines. Hum Gene Ther 1999; 10(12):1983-91 Powell A, Creaney J, Broomfield S, et al. Recombinant GM-CSF plus autologous tumor cells as a vaccine for patients with mesothelioma. Lung Cancer 2006;52(2): 189-97

Review

61.

Le DT, Brockstedt DG, Nir-Paz R, et al. A live-attenuated listeria vaccine (ANZ-100) and a live-attenuated listeria vaccine expressing mesothelin (CRS-207) for advanced cancers: phase I studies of safety and immune induction. Clin Cancer Res 2012;18(3):858-68

62.

Kelly RJ, Sharon E, Pastan I, Hassan R. Mesothelin-targeted agents in clinical trials and in preclinical development. Mol Cancer Ther 2012;11(3):517-25

63.

Maslak PG, Dao T, Krug LM, et al. Vaccination with synthetic analog peptides derived from WT1 oncoprotein induces T-cell responses in patients with complete remission from acute myeloid leukemia. Blood 2010;116(2):171-9

64.

Krug L, Dao T, Brown A, et al. WT1 peptide vaccinations induce CD4 and CD8 T cell immune responses in patients with mesothelioma and non-small cell lung cancer. Cancer Immunol Immunother 2010;59(10):1467-79

65.

Harrop R, Ryan M, Myers K, et al. Active treatment of murine tumors with a highly attenuated vaccinia virus expressing the tumor associated antigen 5T4 (TroVax) is CD4+ T cell dependent and antibody mediated. Cancer Immunol Immunother 2006;55(9):1081-90

66.

ClinicalTrials.gov. Intra-pleural administration of GL-ONC1, a genetically modified vaccinia virus, in patients with malignant pleural effusion: primary, metastases and mesothelioma. 2013. Available from: http://clinicaltrials.gov/show/ NCT01766739

67.

Bidlingmaier S, He J, Wang Y, et al. Identification of MCAM/CD146 as the target antigen of a human monoclonal antibody that recognizes both epithelioid and sarcomatoid types of mesothelioma. Cancer Res 2009;69(4):1570-7

973