Immunotherapy in gynecologic malignancies

In 1893, William Bradley Coley reported the case of a German immigrant with a neck sarcoma that was deemed inoperable and yet disappeared after an erysipelas infection ). Coley hypothesized that the immune response provoked by the bacterial infection led to remission of the sarcoma. Therefore, he went on to develop Coley’s toxins, a mixture of initially live and later dead bacteria that included Streptococcus pyogenes and Serratia marcescens species, and used it for therapeutic purposes . The American surgeon and cancer researcher William Bradley Coley has been considered the “father of cancer immunotherapy.” Coley’s work is certainly noteworthy, but it should be noted that current opinion is that Coley’s toxins are not effective in treating cancer.

Immunotherapy for cancer is utilizing components of the immune system to induce anti-tumor responses. Cancer immunotherapy can be divided into active and passive immunotherapy. Passive immunotherapy enhances existing anti-tumor responses and includes the use of monoclonal antibodies, and cytokines. Active immunotherapy directs the immune system against specific cancer antigens and includes immune cell therapies and therapeutic cancer vaccines.

The cancer immunity cycle illustrates the stepwise process that activates tumor-specific immune responses ( Fig. 17.1 ). Solid tumors present and release tumor-associated antigens (TAAs) that are processed by professional antigen-presenting cells (APCs), e.g., dendritic cells. APCs present these antigens to T cells at local lymph nodes. The T cells are activated and primed to recognize the TAAs. T cells reach distant tumor sites via the systemic circulation, recognize specific TAAs on tumor cells, and infiltrate the tumor tissue. Cytotoxic T cells can elicit potent anti-tumor responses and cause regression of solid tumors.

Every step in the process of antigen presentation, T cell activation, and tumor cell killing is regulated by complex mechanisms. Cytokines like interleukin (IL)-2, for example, can activate T cells. The interaction between B7 expressed on dendritic cells and CD28 on T cells generates activating signals, while the interaction between B7 and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) inhibits the activation of T cells during antigen presentation. In the tumor microenvironment, various immune checkpoints modify the activity of T cells. The interaction between programmed cell death receptor 1 (PD-1) and the programmed cell death ligand 1 (PD-L1) inactivates T cells and suppresses anti-tumor immunity. Other checkpoint inhibitors including PD-L2, V-type immunoglobulin domain suppressor of T cell activation (VISTA), and lymphocyte-activation gene 3 (LAG-3) have similar T-cell suppressive function.

Several important immunologic concepts should be considered. Clinically, in ovarian cancer and other solid tumors, the neoantigen load can be considered a prognostic biomarker for survival. Strickland et al. reported a statistically significant difference in overall survival ( P = 0.0331) among patients with a high neoantigen load compared with those with a low neoantigen load ( ). The tumor microenvironment is also a dynamic region in which vascular endothelial growth factor has been noted to have immunosuppressive properties. Zhang et al. have observed improved clinical outcome with high levels of tumor-infiltrating lymphocytes (TILs) within tumor cell islets ( ). Indeed, the effectiveness of immunologic checkpoint inhibitors has been shown to track with infiltration by TILs.

When considering the different immune checkpoints described previously, it is important to invoke the hierarchy of co-inhibitory receptors. It appears that all checkpoint inhibitors have some effect on CD8+ T cell and natural kill (NK) cell effector function, PD-1 blockade is more robust than that of LAG-3, T cell immunoglobulin mucin domain-3 (TIM-3), or TIGIT blockade, with the latter three preferentially having an impact on tumor tissue Treg and IL-10-producing cells. The dendritic cell phenotype is also affected by TIM-3 and TIGIT inhibition. This suggests that different immune checkpoint inhibitors (ICIs) can be combined to achieve distinct immunologic responses.

The most commonly used immunotherapies utilize ICIs. The currently available ICIs are monoclonal antibodies that target PD-1, PD-L1, or CTLA-4. The blockade of these proteins by monoclonal antibodies will prevent the interaction with their respective binding partners and thereby prevent T-cell activation. Cell therapies utilize different subpopulations of white blood cells for treatment. T cells, for example, can be extracted from peripheral blood mononuclear cells or from tumor tissues. The latter approach generates so-called tumor infiltrating lymphocytes that can be expanded in cell culture and selected for the recognition of specific TAAs. Genetic engineering techniques generate T cells that express chimeric antigen receptors (CARs) or T-cell receptors (TCRs) for the recognition of specific TAAs. Vaccines stimulate anti-tumor immune responses by presenting TAAs to APCs. Both cell therapies and therapeutic vaccine are still under investigation in gynecologic malignancies and are currently not approved for use in patients.

Cytokines

Early immunotherapies in gynecologic cancers have used cytokines such as IL-2, IL-12, and interferon (IFN)-α and -γ as single-agents or in combination with other treatment modalities. These cytokines primarily activate cytotoxic T cells and enhance antigen presentation. A variety of clinical trials has demonstrated anti-tumor efficacy via intraperitoneal application. Despite these positive results, cytokine therapy is only used in clinical trials for gynecologic malignancies and has not been approved for standard treatment in patients. Cytokine therapy can induce significant side effects including fever and cardiovascular compromise often requiring intensive care unit management.

Interleukin-2

Intravenous infusion of recombinant IL-2 in high doses is associated with high morbidity. Weekly intraperitoneal infusions were reportedly better tolerated and yielded in a phase II trial of platinum-resistant ovarian cancer a 25% response rate. Four patients showed a complete and two a partial response with a long duration of response.

Interleukin-12

Intravenous and intraperitoneal application of recombinant IL-12 has, in the treatment of ovarian cancer, only modest success thus far. In a phase II trial of recombinant IL-12 , the maximum response was stable disease. Two patients showed stable disease and nine patients progression of disease.

Interferons

Intraperitoneal infusions of single-agent interferons and combination treatments of recombinant IFN-α and -γ plus chemotherapy for ovarian cancer have been mainly studied in the 1990s. Although these are mainly phase I trials, they demonstrated that immunotherapy in ovarian cancer can have efficacy.

Monoclonal antibodies

Monoclonal antibodies are tools of immunotherapy. Epidermal growth factor receptor (EGFR), HER-2/neu, and vascular endothelial growth factor (VEGF) antibodies predominantly interfere with overexpressed molecules that are critical for cancer cell proliferation and invasion; they do not stimulate the immune system. However, this classification becomes somewhat blurred because of partially overlapping mechanisms, e.g., trastuzumab triggers antibody-dependent cellular cytotoxicity (ADCC) and functions in part as an immune stimulator, while its main mechanism is thought to be the interference with an upregulating signaling cascade. Antibodies that stimulate the immune system are described in the following sections.

The WHO nomenclature provides an antibody classification. The stem “-mab” indicates monoclonal antibodies. The substem for the animal origin of the antibody was dropped in 2017 but is still part of older antibody names (-o- for mouse, -a- for rat, -e- for hamster, -i- for primates). For humanized antibodies, -zu- follows, or -xi- for chimeric antibodies (only fragment crystallizable [Fc] region replaced). The subset preceding the source of the antibody defines its target. Examples are -ciI- for circulatory system, -li(m) for immune system. The old system used different tumor designations, e.g., -go(v) for ovarian cancer, while the new system only employs the site agnostic -t(u). The leading first one to two syllables in an antibody name are without any meaning. With this classification in mind, antibody names can be dissected, as exemplified with the anti-folate receptor α (FRα) antibody farle-tu-zu-mab : according to the new classification a tumor site of the antibody’s anti-tumor effect is not designated (-tu-); however, it is a humanized (-zu-) monoclonal antibody (-mab).

Oregovomab

Oregovomab is a mouse monoclonal antibody directed against the membrane bound and soluble Ca-125. The antigen-antibody complexes trigger broad cellular and humoral immune responses. The Ca-125-oregovomab complexes can prime dendritic cells. Anti-idiotypic antibodies are formed against oregovomab and Ca-125 which are able to induce Fc-mediated tumor cell killing. Improved survival was noted in ovarian cancer patients who develop specific B- and T-cell responses after oregovomab injection. In a phase III trial, oregovomab maintenance therapy after standard adjuvant chemotherapy of primary ovarian cancer did not show any benefit. In another phase II trial in the same setting, however, simultaneous day infusion with oregovomab on alternate cycles with adjuvant platinum-based chemotherapy permitted an immune effect and significantly improved progression-free survival. Based on these data, a randomized phase III trial of carboplatin and paclitaxel with or without oregovomab has been initiated.

Human Milk Fat Globule 1

The Human Milk Fat Globule 1 (HMFG1) is a murine monoclonal antibody that recognizes an epitope on the extracellular domain of mucin 1 (MUC1). This antibody has been labeled with Yttrium 90 and used for radioimmunotherapy of ovarian cancer. After promising initial clinical studies on its intraperitoneal application, a phase III trial showed no difference between standard treatment of ovarian cancer and standard treatment plus a single intraperitoneal infusion of Y-90-labeled HFMG1 in progression-free and overall survival.

Catumaxomab

Catumaxomab is a trifunctional monoclonal antibody. It consists of one half (one heavy and one light chain) of an anti-EpCAM antibody and one half of an anti-CD3 antibody. It can simultaneously bind to EpCAM on the tumor cell and CD3 on the T cell. In addition, with its Fc region it can bind to accessory cells, including macrophages, NK and dendritic cells. In phase II and phase II/III trials, catumaxomab was effective in decreasing malignant ascites production in ovarian cancer, improved quality of life, and prolonged puncture-free interval with an acceptable safety profile. However, only a 5% response rate was seen in platinum-resistant ovarian cancer. Catumaxomab was voluntarily withdrawn in the United States in 2013 and for commercial reasons by the European Commission in 2017.

Farletuzumab (MORab003)

Farletuzumab is a humanized monoclonal IgG1 antibody directed against the FRα. Farletuzumab does not prevent folate binding to the receptor, nor inhibit receptor-mediated endocytosis. Instead it induces ADCC, complement-dependent cytotoxicity (CDC), and tumor cell autophagy. In a phase II trial, patients with recurrent platinum-sensitive ovarian cancer treated with farletuzumab and carboplatin and paclitaxel followed by farletuzumab maintenance therapy showed favorable responses compared to historic controls. However, in a subsequent phase III trial analyzing recurrent platinum-sensitive ovarian cancer treated with chemotherapy plus farletuzumab or plus placebo, the progression-free survival did not improve. Subsequent analyses showed that ovarian cancer patients with higher FRα levels may benefit more from farletuzumab use.

Antibody-drug conjugate

Antibody-drug conjugates (ADCs) are a new class of anticancer drugs which employ the specificity of an antibody in combination with the cytotoxicity of a small molecule anticancer drug. It does not enhance the immune response and thus does not meet the strict definition of immunotherapy; however, given the recent promising results of ADCs in gynecologic cancers, we would like to introduce their concept here. In ADCs, a monoclonal antibody is fused by a linker to a small cytotoxic molecule ( Fig. 17.2 ). The antibody provides selectivity. The cells take up the ADC by endocytosis. The cytotoxic drug, the payload, is released in intracellular compartments such as endosomes or lysosomes. The linker can be cleavable, e.g., by cathepsins that are located in lysosomes and activated by the low pH in lysosomes, or it can be non-cleavable. In the latter case, the antibody will be degraded intracellularly and only the cytotoxic agent remains and thereby becomes active. In the former case, the cytotoxic agent may evade the cell and kill tumor cells nearby as well, the so-called “bystander killing.”

Mirvetuximab soravtansine (IMGN853)

This is an ADC combining a monoclonal antibody against the FRα with the maytansinoid DM4 (N(2´)-deacetyl-N(2´)-(4-mercapto-4-methyl-1-oxopentyl)-maytansine) via a sulfo-SPDB linker (N-succinimidyl 4-(2-pyridyldithio)-2-sulfobutanoate). Maytansine inhibits microtubule assembly and induces mitotic arrest, and is thereby cytotoxic.

Clinical use of antibody drug conjugates

Ovarian cancer

Following a promising dose-escalation study on single-agent mirvetuximab, a recently published phase Ib trial of mirvetuximab soravtansine (6 mg/kg adjusted ideal body weight every 3 weeks) combined with bevacizumab in platinum-resistant ovarian cancer showed that this combination was well tolerated and effective. The objective response rate was 39% (including 5 complete and 21 partial responses) and the median progression-free survival 6.9 months.

Cervical cancer

Tisotumab vedotin targets tissue factor, a protein highly expressed in cervical cancer. This ADC has demonstrable activity in pretreated recurrent and metastatic cervical cancer and is discussed in detail in the chapter 3 ( ).

Immune checkpoint inhibitors

Negative regulators of the immune system, so-called immune checkpoints, prevent an overshooting immune response with possible self-recognition and subsequent autoimmune phenomena. Since cancer antigens may be at times similar to self, immune checkpoints also limit anti-tumor responses of the immune system. The inhibition of these negative regulators unleashes the immune anti-tumor response ( Fig. 17.3 ).

Anti-cytotoxic T lymphocyte-associated protein 4 antibodies

In 1994, it was demonstrated for the first time that CTLA-4 plays an inhibitory role in regulating the T-cell response. CTLA-4 is primarily an intracellular protein. Its cell surface expression is tightly regulated by restricted trafficking and rapid internalization. It is inducibly expressed by native T cells and constitutively expressed by FoxP3 ⁺ regulatory T cells (Tregs). Upon T-cell activation, i.e., T-cell receptor engagement and co-stimulation with CD28, CTLA-4 translocates to the plasma membrane. Here, CTLA-4 outcompetes CD28, prevents co-stimulatory signals from binding, and thereby inhibits the T cell. CTLA-4 activation arrests T-cell proliferation and activation. Mice lacking CTLA-4 die of a fulminant lymphocytic infiltration of almost all organs. In 1996, James Allison and colleagues blocked CTLA-4 with antibodies to inhibit its immune suppressive effects and showed an increased anti-tumor response. Early clinical trials yielded durable anti-tumor responses in solid tumors but also mechanism-related toxicities including autoimmune enterocolitis, hepatitis, and dermatitis. Algorithmic use of steroids alleviated the autoimmune side effects of anti - CTLA-4 antibody treatment without abrogating its antitumor response.

Ipilimumab

Ipilimumab is a fully human monoclonal anti-CTLA-4 IgG1 antibody. It has been hypothesized that the anti-CTLA-4 antibodies disinhibit the immune response by two possible mechanisms: (i) interference of the CTLA-4/ B7 binding and (ii) depletion of immunosuppressive Tregs via Fc-mediated antibody dependent cell-mediated cytotoxicity (ADCC) and CDC.

Tremelimumab

Like ipilimumab, tremelimumab is a fully human monoclonal anti-CTLA-4 antibody. However, it is the non-complement fixing isotype IgG2 and may have fewer effects on the density of Tregs (see earlier). The experience with tremelimumab in gynecologic malignancies is thus far limited.

Zalifrelimab

Zalifrelimab (AGEN1884) is another fully human monoclonal anti-CTLA-4 IgG1 antibody. As an IgG1 antibody it displays the same mechanism of action as proposed for ipilimumab .

Clinical use of anti-CTLA-4 antibodies

Ovarian cancer, cervical cancer

Single-agent ipilimumab has been used in recurrent ovarian cancer with only modest success. Similarly, ipilimumab did not show significant single-agent activity in recurrent cervical cancer, even though it was well tolerated and able to induce an immune response. The combined use of e.g., CTLA-4 antibodies with PD-L1 antibodies showed more clinical benefit (see later).

Anti-programmed cell death receptor-1 antibodies

In 1992, PD-1 (or CD279) was first described by Tasuku Honjo and colleagues. The name programmed cell death receptor was chosen, since the receptor was believed to be involved in T-cell death. Later, PD-1 was found to be an immune checkpoint. The tyrosine phosphatases SHP-1 and SHP-2 ( S rc h omology region 2 domain-containing p hosphatase) mediate PD-1’s inhibitory function and dephosphorylate signaling molecules downstream of the TCR and thereby inhibit cytokine production, e.g., IL-2 and IFN-γ, and T-cell proliferation.

PD-1 is a cell surface receptor and, in contrast to CTLA-4, is expressed on a wide variety of cells, including CD4 and CD8 T cells, B cells, monocytes, NK cells, and dendritic cells. PD-1 is not expressed on resting T cells but can be induced upon activation. It can also be induced on APCs, PD-1 has two ligands, PD-L1 (or CD274 or B7-H1) and PD-L2 (or CD273 or B7-DC). PD-L1 is expressed by many cell types including epithelial, endothelial, and stromal cells. Its expression is induced by pro-inflammatory cytokines such as interferons, tumor necrosis factor (TNF), and VEGF. PD-L2 is expressed by APCs.

Upon TCR activation, T cells produce IFN-γ, the strongest stimulator of reactive PD-L1 expression. Repeated exposure to cognate antigens thereby results in high PD-L1 expression and continuous PD-1 signaling which continuously counteracts the stimulating effect of the antigen and eventually induces T-cell exhaustion. T-cell exhaustion is a state of acquired T-cell dysfunction and a hallmark of chronic infection and cancer. It is defined by progressive poor effector function and sustained expression of inhibitory receptors. Immune checkpoint inhibition using PD-1 and PD-L1 inhibitors aims to reverse T-cell exhaustion.

Currently available monoclonal antibodies recognize the receptor PD-1 and the ligand PD-L1.

Pembrolizumab (MK-3475)

Pembrolizumab is a humanized monoclonal anti-PD-1 IgG4 antibody. It does not activate complement or bind Fc receptors, and thereby avoids cytotoxic effects on T cells. It binds to the PD-1 receptor and blocks the interaction with PD-L1.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here