INTERview

Immunotherapy in : hype or hope?

Interview with B.J. Monk1 and E. Pujade Lauraine2 by C. Marchetti3

In favor of immunotherapy: for the field of immunotherapy in cancer-related disease. B.J. Monk1 Since then there are been many more steps forward and, in Against immunotherapy: the last two decades, advances in the understanding of OC E. Pujade Lauraine2 immunogenicity have further opened the door to immuno- therapeutic approaches. Introduction Immunotherapy as a potential approach for the treatment Ovarian cancer (OC) is the most important cause of gyne- of OC is based on the following evidence: cologic cancer-related mortality, with the majority of wom- • ovarian cancers express tumor-associated antigens, en presenting with advanced disease. Although surgery and including HER2/neu [2], MUC1 [3], OA3 [4], mem- chemotherapy can improve survival rates, alternative strat- brane folate receptor [5], NY-ESO-1 [6], and many egies need to be integrated to improve outcomes. Advances others, which can serve as targets for humoral and cel- in understanding about the role of the immune system in the lular immune responses; pathogenesis of cancer have contributed to the rapidly- • the presence of tumor infiltrating lymphocytes (TILs) evolving field of immunotherapy, which might facilitate a correlates strongly with survival [7]; sustained immune system response against recurring cancer • ovarian cancers express peptide/major histocompat- cells. However, to date there are only limited data on which ibility complex (MHC) complexes, which can be rec- the role of immunotherapy in OC can be based. In this in- ognized by CD8+ T lymphocytes; terview, two experts will discuss the main data, as well as • the dynamic interaction between host immunity and the next challenges and limitations in the development of cancer indicates that the balance between the two forc- immunotherapy for the treatment of OC. es can be tipped to favor the host immunity, with the ever increasing arsenals of immunology. 1. Can we consider ovarian cancer as an immunogenic disease? Taken together, it has been hypothesized that immuno- therapy could be an innovative and effective supportive Pro immunotherapy therapy for OC. Immunogenicity is the ability of antigens to elicit an im- mune response. The first cancer vaccine in humans was Against immunotherapy attributed to William Coley in 1893 [1]. He observed that There is much evidence in favor of this assumption, such some patients with cancer benefitted from bacterial infec- as documentation of spontaneous antitumor immune re- tion, resulting in tumor shrinkage. This was the first step sponse and the association between this and longer sur- vival, evidence of tumor immune evasion mechanisms and a link with short survival, and pilot data supporting the ef- 1Division of Gynecologic Oncology, Department of Obstetrics ficacy of immune therapy [8]. Indeed, OC can no longer be and Gynecology, St Joseph’s Hospital and Medical Center, University of Arizona Cancer Center, Phoenix, AZ 85013, USA. considered as an immunologically inert class of tumors. [email protected] Nevertheless, the mechanisms of immune surveillance and 2Université Paris Descartes, AP-HP, Hˆopitaux Universitaire Paris Centre, Site Hˆotel Dieu, Oncologie, 75004 Paris, France. immune-escape in cancer patients seem to be quite com- [email protected]. plex and have not been fully explained. In fact, immune 3Department of Gynaecological and Obstetrical Sciences and suppressive signals are often dominant, and may prevent Urological Sciences, Università di Roma “Sapienza”, . effective clearance of tumor cells by the immune system. A Correspondence to: Dr. Claudia Marchetti, Policlinico Umberto I, conspicuous group of immune suppressive factors and Viale del Policlinico 155, 00161 Roma, Italy. cells halt the generation and clonal expansion of antitumor Phone: +39 06 4940550 – Fax: +39 06 49972564 E-mail: [email protected] immunity. Furthermore, genetic changes in tumor cells al- CANCER BREAKING NEWS 2015;3(2):14-19 low them to be ignored by an immune response. This may

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explain why, until recently, that only important changes in is a that recognizes immunological features have been observed and there is a CA125 and forms circulating immune complexes that can lack of relevant clinical results. elicit immunity against both tumor antigen and tumor. Ore- govomab was not associated with a significant survival ad- 2. How should we interpret data coming vantage when given as maintenance therapy after front-line from clinical trials on antibody-based treatment [10]. In addition, although it elicited an immune immunotherapies for ovarian cancer? response when combined with standard chemotherapy, no tumor-antigen specific T cell immunity could be detected in Pro immunotherapy the circulation [12]. Results from the trials of abagovomab Antibodies are fascinating anti-cancer agents given their and oregovomab highlight two important lessons. Firstly, high specificity for antigens, stability, and ability to be they caution against becoming overly excited about novel mass-produced by bioengineering technology. They can drugs that show promise in phase I and/or II clinical trials potentially induce tumor cell apoptosis via a number of because high expectations are often not met in phase III mechanisms, including complement-dependent cytotoxici- studies. Secondly, immune reactivity is common when pa- ty, mediated when the Fc portion of immunoglobulins acti- tients are treated with immunomodulatory drugs and is more vates the complement system; antibody-dependent cellular frequent in patients with a favorable prognosis, which ac- cytotoxicity; limiting tumor growth by binding to growth counts for the better prognostic of immune-reactive com- receptors, preventing interactions with endogenous ligands pared with non-immune reactive patients, but generating and hence inhibiting downstream signaling events; and by specific anti-tumor T cells instead of a non-specific immune inducing tumor cell death through modulation of anti-tumor response remains one of the most difficult, but ultimate, immunity via blockade of immune checkpoint inhibitors. goals of immunotherapy. Antibody-based cancer immunotherapy has now become standard practice in the treatment of lymphoma and other 3. Immune checkpoint inhibitors have cancers. emerged as promising therapies in Many attempts at immunotherapy have been undertaken in several tumors and interesting data have OC. After controversial results with the use of anti-idiotyp- recently been presented in recurrent ic antibodies [9, 10], interesting data have been obtained ovarian cancer. Do they have the with antibodies able to inhibit immune checkpoints and ac- potential to be incorporated into clinical tivate effector T cells. In the near future we will see the ef- practice in this setting? fects of combining different monoclonal antibodies and this may truly be the right way forward. Pro immunotherapy As mentioned previously, we have recently seen the clinical Against immunotherapy development and approval of immunomodulators, also Results with immunotherapy in OC are controversial. The known as immune checkpoint inhibitors. Briefly, T cell acti- tumor-associated antigen CA125, a well-known surface gly- vation is triggered via the T cell receptor (TCR) by recogni- coprotein that is frequently expressed in OC, was thought to tion of the cognate antigen complexed with the MHC. This be the most interesting target. Two monoclonal antibodies activation is regulated by complex signals downstream of with different mechanisms of action, abagovomab and ore- the CD28 family of immune receptors, which includes co- govomab, have been developed. Abagovomab has one of stimulatory (CD28 and ICOS) and inhibitory (CTLA-4, the most captivating mechanisms of action, which is that of PD-1, and BTLA) receptors. PD-1 and CTLA-4 are induced the anti-idiotypic antibodies. The term idiotype (Id) means on T cells after a TCR signal, and result in cell cycle arrest the typical antigenic determinant of the antibody variable and termination of T cell activation. The use of monoclonal region that allows differentiation between Ig binding to dif- antibodies that block CTLA-4 or PD-1 can sustain the acti- ferent antigens. The most immediate application of this re- vation and proliferation of tumor-specific T cells, preventing lates to the targeting of tumor antigens to which the Id is di- anergy or exhaustion, and thereby allowing the development rected. On the basis of this information, anti-Id antibodies of an effective tumor-specific immune response. After prom- were developed to mimic tumor antigens. After promising ising results in preclinical studies, many clinical trials have results in early phase trials [11], abagovomab was found to demonstrated the acceptable safety and efficacy profiles of be safe and had the ability to induce measurable immune immune checkpoint inhibitors in a variety of cancers. responses, but without prolongation of relapse-free and The first approved immune checkpoint inhibitor was ipili- overall survival (OS) [9]. mumab, an anti-CTLA-4 (cytotoxic T lymphocyte anti-

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gen-4) monoclonal antibody, in the setting of advanced fects and could therefore decrease the efficacy of Anti- melanoma. Several clinical trials with have PD-L1/anti-P1 immunotherapy. Anti-PD-L1/anti-P1 also included patients with OC and anti-tumor effects have molecules will also be evaluated in combination with been noted [13, 14]. because vascular endothelial growth factor There are now many antibodies targeting CTLA-4, PD-1 (VEGF) is inversely correlated with T cell epithelial in- or PD-L1 undergoing clinical trials in OC (, at- filtration in OC. Finally, the question of combining ezolizumab, durvalumab, avelumab). Preliminary results checkpoint inhibitors with different mechanism of action of some of these studies have been recently presented and remains an unresolved topic in OC. showed very promising results [15, 16]. Also, there is cur- A strategy to selectively manipulate the tumor microenvi- rently an ongoing a study investigating the combination of ronment rather than systemic promotion of T cell immu- ipilimumab and nivolumab (a monoclonal antibody tar- nity is desirable. This is particularly important because geting PD-1) (NRG-GY003). many tumor cells express ligands for the co-inhibitory re- The rationale of this trial is based on the non-redundant ceptors, whereas there is minimal expression of these nature of CTLA-4- and PD-1-mediated T cell inhibition, molecules in normal tissues [19]. Also, the potential to as well as the co-expression of CTLA-4 and PD-1 evident combine multiple T cell checkpoint blockade strategies to on molecular profiling of tumor-reactive infiltrating T maximize anti-cancer immunity needs to be further inves- cells (CD137+) from ovarian cancers. Furthermore, in tigated, in line with some published results [17]. Blockade animal studies, co-administration of anti-PD-1 antibodies of CTLA-4 with antibody, however, led to significant tu- and anti-CTLA-4 antibodies reversed TIL dysfunction mor regression in patients with advanced melanoma but and induced tumor regression in 50% of the mice com- severe autoimmune toxicity was evident in 15% of pa- pared with 25% of mice when either agent was given as a tients [13]. Therefore, the next step will be to integrate monotherapy [17]. This is definitely an active area of re- checkpoint inhibitors into the therapeutic armamentari- search and, considering experiences in other solid tumors, um for OC, although optimization of their use in clinical it is reasonable to hypothesize that these agents might be practice may be a bit further away. incorporated into OC treatment strategies at some point in the near future. 4. What is the possible role of adoptive cell therapy in ovarian cancer therapy? Are Against immunotherapy chimeric TCReng T cell-based strategies Recent findings demonstrate that a variety of functionally really promising? non-overlapping co-inhibitory receptors can be expressed by T cells to turn off their effector function [18]. These inhibitory Pro immunotherapy receptors include CTLA-4, PD-1, TIM-3, BTLA, PD-L1. Adoptive cellular therapy (ACT) has received much at- The possibility of overcoming this immunosuppressive tention as a realistic technique for cancer treatment. Can- phenomena and stimulating a tumor response is obviously cer immunotherapy is dependent on the presence of intriguing. Clinical data with anti-PD-L1/anti-PD-1 TILs, which correlate with survival in OC. Chimeric an- agents in several tumors are promising, as are recently tigen receptors (CARs) are artificial cell receptors that reported data in OC, with a 10-20% objective response allow T cells to target a tumor-associated antigen (TAA); rate in heavily pre-treated OC patients including some CARs bypass the downregulation of MHC-I and antigen patients with very prolonged disease control [13-16]. Al- presentation (a common immune evasion mechanism of though these results are still very preliminary, it is be- tumor cells), and provide engineered T cells without coming clear that individual anti-PD-L1/anti-PD-1 MHC restriction and with potent costimulatory signals. agents will need to be combined to optimize their action. Furthermore, antibody-antigen affinity is several times Several combinations including checkpoint inhibitors stronger than natural TCR-mediated recognition. A large will be tested in future studies. Anti-PD-L1/anti-P1 will number of CARs targeting diverse tumors have been de- be tested with chemotherapy, either with standard carbo- veloped [20]; however, clinical pilot studies are only just platin- combination or with pegylated liposo- beginning. The first study of adoptive transfer of CAR T mal doxorubicin, the immunomodulatory properties of cells in OC demonstrated the safety of this approach but which are well known. However, this type of immuno- activity was disappointing, with no clinically-evident tu- therapy depends on a healthy immune system and con- mor responses, most likely due to low expression of the ventional cancer treatments, including chemotherapy transgenic CAR and poor persistence of the transferred T and radiation therapy, often have immunosuppressive ef- cells [21].

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Persistence can be improved by adding costimulatory effectiveness of manufacturing a drug for each patient signaling capabilities to the intracytoplasmic domain of will remain a challenge for these therapies, even if their CARs; second and third generation CARs now include efficacy is proven. additional co-stimulatory signaling domains, such as those from CD28, CD27 and 41-BB, all designed to en- 5. What are the critical hurdles and hance immune activation and T cell persistence. A phase upcoming challenges in ovarian cancer I clinical trial is investigating the safety, feasibility and immunotherapy? preliminary activity of the adoptive transfer of autolo- gous T cells transduced with CAR recognizing the fo- Pro immunotherapy late receptor alpha (FRa) and carrying the CD3z domain Immune-based therapies have now demonstrated efficacy along with the 41-BB co-stimulatory signaling domain in a range of clinical studies and types of cancer. We have to address the issue of persistence of FRa-specific seen that the selective manipulation of T cell checkpoint CAR-T cells [22]. Eligible patients have FRa-positive inhibitors or the adoptive transfer of tumor-reactive T cells epithelial stage II-IV OC that had relapsed after two or promises some efficacy in the treatment of OC. However, more chemotherapy regimens; all are receiving untrans- the more realistic and achievable application of immuno- duced autologous peripheral blood lymphocytes intra- therapy in the short-to-medium term is probably as an ad- venously to contain the exponential expansion of junctive therapy rather than as a front-line monotherapy. CAR-T cells [22, 23]. Chemo-immunotherapy is appealing not only because che- motherapies directly induce apoptosis of tumor cells and Against immunotherapy result in the release of antigen to drive immune responses, Immune cells, including T cells, natural killer (NK) cells, but they often also disrupt essential immune regulatory dendritic cells (DCs) and macrophages, can be removed mechanisms that limit the development of immunity, an in- from a patient, manipulated ex vivo and then infused creasingly appreciated attribute [25]. An ideal combination back into the same patient in order to boost anti-tumor of chemo-immunotherapy would be where one or both cellular immune responses. After early data in melanoma agents have minimal overlapping toxicities and work via tumors established the feasibility of adoptive T cell independent mechanisms, but have additive or synergistic transfer, attention has focused on optimizing the anti-tu- antitumor effects. Several trials are currently ongoing to ad- mor efficacy of this therapy. Given that the availability dress this question, and some of the preliminary data are of TILs is limited, investigators are looking into generat- promising [26]. Selection of appropriate patients for clini- ing tumor-specific T cells via the ex vivo CD3/CD28- cal trial participation will be quite important because evi- costimulation of vaccine-primed peripheral blood T cells dence to date indicates that many patients with OC display or by genetically modifying peripheral blood T cells to a spontaneous antitumor immune response. These patients express high affinity cloned TCRs or CARs. CARs are may be best suited for vaccine therapy or TIL-based thera- recombinant receptors that combine the specificity of an py because they are the most likely to harbor a natural rep- antigen-specific antibody with the activating functions ertoire of tumor-reactive T cells with tumor-rejecting poten- of a T cell. This is clearly a very interesting process that, tial that can be expanded in vivo or ex vivo. In addition, pa- intuitively, may help to obtain a more specific immune tients whose tumors exhibit intraepithelial T cells may be response. Nonetheless, the process by which these CARs most likely to respond to immune therapy because the tu- are generated is technically difficult, labor-intensive and mor microenvironment is already conducive to T cell hom- time-consuming. Furthermore, even if this treatment is ing and engraftment. Additional biomarkers are needed to thought to be safe, the clinical benefits have yet to be optimize selection of patients who may benefit from im- clearly defined [21]. It is reasonable to hypothesize that mune therapy. In conclusion, more than ever before, the the existence of a number of different immunosuppressive field of cancer immunology is permeated with a sense of pathways can limit the full potential of CAR T cell thera- optimism. The key question today is not whether immune- pies. The interaction of inhibitory molecules on activated based therapies will transform cancer therapy, but how will T cells and their ligands on tumor cells compromises T these approaches transform cancer medicine in the future. cell function. This includes the increased expression of inhibitory immune receptors such as T cell membrane Against immunotherapy protein-3 (TIM-3), CTLA-4, and/or PD-1 on T cells fol- Innovative immunotherapeutic strategies offer the promise lowing T cell activation, which can limit the duration and of enhancing host anti-tumor responses, which may im- strength of the adaptive immune response [24]. The cost- prove clinical outcomes in women with OC. While many

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preliminary phase I/II studies have demonstrated induction a need to optimize the timing of treatment administration, of anti-tumor responses, current data on clinical outcomes and surgery and chemotherapy are extremely immunosup- in the OC setting are controversial. To date, interesting re- pressive making them very difficult to combine with immu- sults have been achieved by immunomodulation strategies notherapy. Therefore, what is the best time for immunother- including anti-CTLA-4, anti-PD-1 and anti-PD-L1 mono- apy to be administered? Should immunotherapy be given clonal antibodies, and the combination of immunotherapy first, then followed by surgery and chemotherapy? Does with chemotherapy is another area of interest. Nonetheless, corticosteroid premedication before chemotherapy adminis- there are a number of questions to be answered and some tration prevent checkpoint inhibitor monoclonal antibodies limitations need to be considered. Primarily, although there from being active? There should also be a focus on finding is no lack of OC antigens due to genomic instability and biomarkers for early diagnosis or prognosis and individual- accumulation of mutated genes at this point, the generation ization of treatment. For example, what is the role of tumor of immune responses against these antigens is likely to be PD-L1 expression? The presence of TIL? Or the presence of unproductive in the late stage of disease due to multiple immunosuppressive immune cells such as T regulatory immune tolerance mechanisms. cells, immature dendritic cells or M2 macrophages in the Thus, multiple immunological ‘brakes’ need to be consid- tumor microenvironment? Finally, conventional response ered to increase the productive immune response. As a re- criteria (RECIST or WHO) may not reflect the patterns of sult, combined immunotherapeutic modalities need to be response to immunotherapies and therefore the correlation seriously considered. However, the application of multiple between clinical and immunological response needs to be therapies (a combination of immunotherapies or immuno- better defined. The next trials in this field should be designed therapy plus chemotherapy) simultaneously requires careful to include careful selection of candidates as well as an ap- consideration of important factors such as the potential for propriate reporting of standardized treatment responses and overlapping toxicities and an elevated risk of severe organ adverse events. This might facilitate clarification of the role damage due to immune system dis-inhibition. There is also of immunotherapy in the treatment of OC.

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