**5. Immunotherapy in ovarian cancer**

In 2003 Zhang and colleagues showed that the presence or absence of tumour-infiltrating lymphocytes (TILs) in EOC is an independent prognostic factor (in multivariate analysis) for PFS and OS. Of 174 patients, those with TILs had a median overall survival of 50.3 months compared to 18.0 months in the 72 patients without [69]. Tumour-associated antigens discovered in EOC include mesothelin, Her2, NY-ESO and ca125 amongst others [70].

Around 50% of EOC has genomic/epigenetic changes in genes implicated in HRD [45]. Therefore there is a subset of EOC with a higher mutational burden possibly more likely to benefit from immunotherapy. Analysis of TCGA data showed a significantly higher predicted neoantigen load in HRD vs. HR proficient tumours [71]. In addition, BRCA1/2 status and neoantigen load were independent predictors of OS in multivariate analysis and BRCA mutated tumours had an increased TIL burden and PD-L1 expression. Lastly, tumour burden/volume is an important factor in predicting the response to immunotherapy [72]. Ovarian cancer is unusual as patients presenting *de novo* with bulky disease can be treated with radical surgery to no residual disease. Although the majority relapse, there is a window of time where disease remains undetectable. Given the data that exists on enhanced effectiveness of immunotherapy in patients with a low overall tumour burden, this may present a window of opportunity to maximise effectiveness of this therapeutic approach.

### **5.1. Checkpoint blockade**

an ORR with a 24% and 18% rate of G3 anaemia and thrombocytopenia respectively [64]. Given its unique potency for trapping, there is hope that it may have efficacy as a second line

PARPi were originally developed as potential chemo/radiosensitizers. There is obvious rationale in combining PARPi with other agents, especially in tumours that are HR proficient. When combining PARPi with chemotherapy, rational combination necessitates consideration of the mechanism of action of the chemotherapy plus the relative catalytic inhibitory/trapping properties of the PARPi. For example, PARPi combination with topo-1 inhibitors is synergistic primarily because of catalytic PARP inhibition whereas synergy with alkylating agents relies on trapping too [66]. Several PARPi/chemotherapy combinations are in trials, reviewed here [67]. Synergistic toxicity (e.g. myelotoxicity) will have to be borne in mind. PARPi/VEGFR targeting combinations have previously been discussed. Other targeted combinations include PI3K/MTOR pathway inhibitors, HSP90 and CHK1/2 inhibitors [67]. Finally, talazoparib had immunomodulatory effects in a pre-clinical mouse model; studies looking at immunotherapy

Several putative mechanisms of resistance have been described. These include a secondary mutation in BRCA which either restores the correct open reading frame (i.e. where the original mutation caused a frameshift) or which fully reverts the original mutation to wild-type. This also causes platinum resistance and in one study of platinum resistance in BRCAm patients, 46% had acquired a secondary BRCA mutation [68]. Other mechanisms include upregulation of P-glycoprotein and loss of 53BP1 (which usually promotes NHEJ and prevents HR). Knowledge of the specific resistance mechanism may have clinical relevance as some (e.g. secondary mutations) cause platinum resistance too whereas others do not. Also, 53BP1 loss

In 2003 Zhang and colleagues showed that the presence or absence of tumour-infiltrating lymphocytes (TILs) in EOC is an independent prognostic factor (in multivariate analysis) for PFS and OS. Of 174 patients, those with TILs had a median overall survival of 50.3 months compared to 18.0 months in the 72 patients without [69]. Tumour-associated antigens discov-

Around 50% of EOC has genomic/epigenetic changes in genes implicated in HRD [45]. Therefore there is a subset of EOC with a higher mutational burden possibly more likely to benefit from immunotherapy. Analysis of TCGA data showed a significantly higher predicted neoantigen load in HRD vs. HR proficient tumours [71]. In addition, BRCA1/2 status and neoantigen load

ered in EOC include mesothelin, Her2, NY-ESO and ca125 amongst others [70].

agent for patients who have progressed on a previous PARPi [65].

**4.8. Combination therapy with PARP inhibitors**

342 Ovarian Cancer - From Pathogenesis to Treatment

with PARPi are underway (NCT0257172).

causes resistance in BRCA1 but not BRAC2 deficient tumours.

**5. Immunotherapy in ovarian cancer**

**4.9. Resistance to PARP inhibitors**

Co-inhibitory checkpoints usually act to minimize collateral tissue damage during immuneactivation. Upregulation of these checkpoints can subvert anti-tumour immunity. The binding of CTLA-4 to B7.1/B7.2 is one such inhibitory interaction that can be prevented by the anti CTLA-4 monoclonal antibody ipilimumab.

In a phase I study including 2 patients with ovarian cancer, one patient had a 43% reduction in ca125 levels while the other developed a plateau in ca125 levels despite rapidly rising levels before treatment [73]. In a follow-up study of 9 patients one developed a radiologic PR with complete resolution of mesenteric lymphadenopathy. Three others achieved radiographic and ca125-defined stable disease of 2, 4 and >6 months duration. In a phase II study of 40 patients with recurrent platinum-sensitive EOC (NCT01611558), 50% developed at least G3 toxicity and the ORR was 10.9% by RECIST. A phase II trial testing a combination of nivolumab and ipilimumab for recurrent ovarian cancer is currently underway (NCT02498600).

A trial using another CTLA4 antagonist, tremelimumab, is currently enrolling patients for phase I trials in combination with olaparib (NCT02571725, NCT02485990).

Another inhibitory checkpoint interaction is between PD-1 (on T-cells) and PD-L1 (that may be upregulated on tumour cells and their microenvironment). Avelumab, a fully humanised IgG1 anti-PD-L1 antibody, was tested in a phase Ib trial in 124 patients with platinum resistant/refractory disease after a median of 4 lines of therapy [73, 74]. The drug was well tolerated with a grade 3/4 adverse event rate of 6.4%. ORR in this heavily pre-treated population was 9.7% and the relationship between germline BRCA status and probability of response is being investigated. Avelumab is currently being tested in two randomised phase III trials. The three-arm JAVELIN Ovarian 200 study (NCT02580058)I is recruiting patients with their first platinum resistant/refractory relapse and randomising to either Avelumab or PLD alone or in combination. In JAVELIN Ovarian 100 (NCT02718417) patients with previously untreated III/ IV ovarian cancer are randomised to carboplatin and paclitaxel followed by placebo or avelumab maintenance or carboplatin and paclitaxel with concurrent *and* maintenance avelumab.

Atezolizumab is also a fully humanized IgG1 anti-PD-L1 antibody. In the phase III ATALANTE trial (NCT02891824) patients with platinum-sensitive relapse are being randomised to platinum-based chemotherapy with concurrent and maintenance bevacizumab + placebo (control arm) or bevacizumab + avelumab (experimental arm). The combination of bevacizumab and avelumab is a rational one based on evidence that endogenous VEGF signalling has a variety of immunomodulatory effects. VEGF-A has been postulated to suppress dendritic cell maturation, increase the presence of immunosuppressive CD34+ haematopoetic progenitor cells in the tumour microenvironment and inhibit T-cell maturation [75]. Another trial combining atezolizumab with bevacizumab (NCT02839707) in a phase II/III setting is randomising platinum resistant patients between 3 arms each containing PLD with either bevacizumab alone (control), atezolizumab alone or bevacizumab and atezolizumab.

which binds to epithelial cell adhesion molecule (EpCAM), CD3 (found on T-cells) and has an Fc portion that is recognised by various cells including macrophages. This allows immune cells to colocalize with tumour and cause cytotoxicity. EpCAM positive cells are found in 70–100% of malignant effusions and in a phase II study intraperitoneal (IP) administration of catumaxomab significantly improved the puncture free interval in heavily pre-treated patients [81]. It was given EMA approval for IP administration but the manufacturer withdrew this for commercial reasons in July 2017. One of the problems of 'targeted' immune therapy such as this is toxicity with systemic administration. Consequently, IP administration may be the only

Novel Systemic Treatments in High Grade Ovarian Cancer

http://dx.doi.org/10.5772/intechopen.71583

345

Combination immune therapy PARP inhibitors, VEGF therapy and chemotherapy have already been mentioned. In addition, checkpoint inhibition has recently been combined with epacadostat, an inhibitor of 2,3-dioxygenase (IDO). IDO activation in tumours is associated with immune escape via T-cell dysfunction. Combining epacadostat and pembrolizumab has shown efficacy in patients with EOC although randomised trials are needed to ascertain the

The aforementioned systemic strategies are of most relevance because they are either already in (or close to) the clinic. There are however various other strategies being explored, some of which have already been trialled in clinical studies. One approach involves targeting folate receptor and, specifically, the α isoform (FRα). This receptor is absent from normal ovarian epithelium but expressed on the majority of EOC [83]. The receptor has been targeted by various classes of therapy including folate-drug conjugates, small molecule FRα inhibitors, monoclonal antibodies, vaccines and oncolytic viruses. The phase III trial of vintafolide (folate conjugated with a derivative of vinblastine) in combination with PLD (NCT01170650) was discontinued for futility. Further trials of folate-drug conjugates are ongoing [84]. Farletuzumab, a monoclonal antibody that causes antibody and complement- dependant cellular cytotoxicity is being investigated in combination with platinum-based chemotherapy in patients with relapsed EOC and low ca125 following promising sub-group analysis from a previous phase III trial (NCT02289950). Phase I results for ONX-0801, a FRα-targeted thymidylate synthase inhibitor that accumulates in EOC cells generated a PR in 5/11 patients at the MTD with 4/4

Aside from FRα targeting therapy, there are multiple other targeted strategies in EOC in pre-clinical and early clinical phases. Cell cycle targeting with WEE-1 inhibition has been discussed but other strategies including CHK1/2 inhibition with prexasertib (which yielded a PR in 5/13 patients in cohort 1 of a recent phase II trial [86]) are being explored. PI3k/AKT/ mTOR, Her2 and molecules in the apoptotic machinery are amongst a plethora of other avenues being explored. As our understanding of the molecular basis of EOC progresses, future

effect of epacadostat over and above pembolizumab monotherapy [82].

viable route with some therapies.

**5.4. Combinations**

**6. Other novel agents**

FRα expressing tumours showing response [85].

Instead of targeting PD-L1, pembrolizumab is a humanized anti PD-1 antibody. Keynote-028 included 26 EOC patients. 1 patient had a CR and 2 had PR by RECIST. The median duration of response was not reached (range 24.9+ to 26.5+) [76]. There are currently several ongoing phase I/II trials with pembrolizumab both as monotherapy and in combination with chemotherapy, niraparib and various small molecule inhibitors in the frontline and recurrent settings (NCT02865811, NCT02520154, NCT02440425, NCT02674061).

Nivolumab, a PD-1 blocking antibody, was given to 20 patients with platinum resistant EOC. 40% of patients developed G3/4 toxicity (lymphopenia, anaemia, hypoalbuminaemia, maculopapular rash, fever, ALT increase). Three patients (15%) had an OR including 2 CRs. One of these was in a patient with clear cell carcinoma (often chemoresistant) and this response was ongoing at the time of study reporting [77]. As with the pembrolizumab data, although the ORR was modest, there was evidence of durable responses in both studies. Nivolumab is being studied in several ongoing trials including in combination with ipilimumab for (NCT02498600), in combination with bevacizumab (NCT02873962) and with a vaccine against the tumour-associated antigen WT1 (NCT02737787).

#### **5.2. Adoptive T-cell therapy**

Adoptive T-cell therapy (ATT) involves the direct administration of various types of anti-tumour T-cells to the patient. Given the prognostic value of TILs (see above), TIL-based ATT seems logical. In one study, 13 patients who had no residual disease after surgery and adjuvant therapy were treated with TIL infusion. A matched control group was followed up concurrently [78]. In this small study 3 year OS was 100% in the TIL group vs. 67.5% in the control group. TIL-based trials are ongoing (NCT02482090, NCT01883297). Another ATT approach involves using chimeric antigen receptor (CAR) T-cells that have been engineered to express a CAR with an extracellular single chain variable fragment incorporating immunoglobulin heavy and light chains capable of targeting any extracellular target (not just those complexed with MHC). There are currently over 20 trials registered on ClinicaTrials.gov testing CAR-T-cell-based therapy in ovarian cancer against targets including Her2, mesothelin, folate receptor-α (FRα) and NY-ESO-1.

#### **5.3. Other approaches**

The field of immunotherapy is advancing rapidly and various other approaches are in early phase trials. Vaccine based therapy has yielded objective responses demonstrating proof-ofconcept, for example using a dendritic cell whole-tumour based approach [79]. Although clinical trials for vaccines have been disappointing, various techniques for optimisation are leading to renewed enthusiasm [80]. Another approach used a tri-functional antibody, catumaxomab, which binds to epithelial cell adhesion molecule (EpCAM), CD3 (found on T-cells) and has an Fc portion that is recognised by various cells including macrophages. This allows immune cells to colocalize with tumour and cause cytotoxicity. EpCAM positive cells are found in 70–100% of malignant effusions and in a phase II study intraperitoneal (IP) administration of catumaxomab significantly improved the puncture free interval in heavily pre-treated patients [81]. It was given EMA approval for IP administration but the manufacturer withdrew this for commercial reasons in July 2017. One of the problems of 'targeted' immune therapy such as this is toxicity with systemic administration. Consequently, IP administration may be the only viable route with some therapies.

#### **5.4. Combinations**

of immunomodulatory effects. VEGF-A has been postulated to suppress dendritic cell maturation, increase the presence of immunosuppressive CD34+ haematopoetic progenitor cells in the tumour microenvironment and inhibit T-cell maturation [75]. Another trial combining atezolizumab with bevacizumab (NCT02839707) in a phase II/III setting is randomising platinum resistant patients between 3 arms each containing PLD with either bevacizumab alone

Instead of targeting PD-L1, pembrolizumab is a humanized anti PD-1 antibody. Keynote-028 included 26 EOC patients. 1 patient had a CR and 2 had PR by RECIST. The median duration of response was not reached (range 24.9+ to 26.5+) [76]. There are currently several ongoing phase I/II trials with pembrolizumab both as monotherapy and in combination with chemotherapy, niraparib and various small molecule inhibitors in the frontline and recurrent set-

Nivolumab, a PD-1 blocking antibody, was given to 20 patients with platinum resistant EOC. 40% of patients developed G3/4 toxicity (lymphopenia, anaemia, hypoalbuminaemia, maculopapular rash, fever, ALT increase). Three patients (15%) had an OR including 2 CRs. One of these was in a patient with clear cell carcinoma (often chemoresistant) and this response was ongoing at the time of study reporting [77]. As with the pembrolizumab data, although the ORR was modest, there was evidence of durable responses in both studies. Nivolumab is being studied in several ongoing trials including in combination with ipilimumab for (NCT02498600), in combination with bevacizumab (NCT02873962) and with a vaccine against

Adoptive T-cell therapy (ATT) involves the direct administration of various types of anti-tumour T-cells to the patient. Given the prognostic value of TILs (see above), TIL-based ATT seems logical. In one study, 13 patients who had no residual disease after surgery and adjuvant therapy were treated with TIL infusion. A matched control group was followed up concurrently [78]. In this small study 3 year OS was 100% in the TIL group vs. 67.5% in the control group. TIL-based trials are ongoing (NCT02482090, NCT01883297). Another ATT approach involves using chimeric antigen receptor (CAR) T-cells that have been engineered to express a CAR with an extracellular single chain variable fragment incorporating immunoglobulin heavy and light chains capable of targeting any extracellular target (not just those complexed with MHC). There are currently over 20 trials registered on ClinicaTrials.gov testing CAR-T-cell-based therapy in ovarian cancer against targets including Her2, mesothelin, folate receptor-α (FRα) and NY-ESO-1.

The field of immunotherapy is advancing rapidly and various other approaches are in early phase trials. Vaccine based therapy has yielded objective responses demonstrating proof-ofconcept, for example using a dendritic cell whole-tumour based approach [79]. Although clinical trials for vaccines have been disappointing, various techniques for optimisation are leading to renewed enthusiasm [80]. Another approach used a tri-functional antibody, catumaxomab,

(control), atezolizumab alone or bevacizumab and atezolizumab.

tings (NCT02865811, NCT02520154, NCT02440425, NCT02674061).

the tumour-associated antigen WT1 (NCT02737787).

**5.2. Adoptive T-cell therapy**

344 Ovarian Cancer - From Pathogenesis to Treatment

**5.3. Other approaches**

Combination immune therapy PARP inhibitors, VEGF therapy and chemotherapy have already been mentioned. In addition, checkpoint inhibition has recently been combined with epacadostat, an inhibitor of 2,3-dioxygenase (IDO). IDO activation in tumours is associated with immune escape via T-cell dysfunction. Combining epacadostat and pembrolizumab has shown efficacy in patients with EOC although randomised trials are needed to ascertain the effect of epacadostat over and above pembolizumab monotherapy [82].
