**6.2. Immunotherapeutics**

Immune checkpoints are emerging as promising targets for treatment of HCC. The immune system helps to distinguish body's own cells from foreign cells. To help it achieve this, immune checkpoints which are molecules on certain immune cells, need to be activated or inactivated to start an immune response. Cancer cells find ways to use such checkpoints to escape immune response.

and showed promising partial response rate and disease control rate of 17.6% and 76.4%,

Emerging Targeted Therapies for Treatment of Hepatocellular Carcinoma (HCC)

http://dx.doi.org/10.5772/intechopen.71480

183

Chromatin remodelling is a critical epigenetic mechanism regulating gene expression and plays an important role in cell proliferation, differentiation and DNA repair. Epigenetics alters gene expression without any changes to the DNA sequence and involves the enzymatic covalent modification of histones such as methylation, phosphorylation and acetylation. Histone deacetylases (HDACs) remove the acetyl group from histones, making DNA more compact resulting in gene silencing. There are a total of 18 HDACs identified in mammals. Accumulating evidence suggests the overexpression of HDACs to be correlated advanced tumour stage, recurrence after surgery and poor prognosis in several cancers including HCC [67, 68]. For these reasons HDAC inhibitors may serve as potential therapeutic targets.

Currently 2 HDAC inhibitors have been approved by the FDA i.e. vorinostat and romidepsin, for treatment of cutaneous T cell lymphoma. These inhibitors demonstrate anti-tumour activity by means of histone hyperacetylation reducing DNA-histone affinity and allowing access to transcription factors enhancing gene expression. Currently, a phase I clinical trial (NCT01075113) is underway to evaluate vorinostat in combination with sorafenib in

Aberrant up regulation of several HDACs (HDAC1, 2, 3, 4, 5, and 11) and changes in copy number of HDAC3 and HDAC5 have been reported in HCC. Treatment with panobinostat (HDAC inhibitor) demonstrated strong anti-tumour activity *in vitro* and *in vivo* and the effect was enhanced in combination with sorafenib [69]. In a recently completed phase I/II trial (SHELTER, NCT00943449), combination of resminostat (HDAC inhibitor) with sorafenib yielded a progression-free survival-rate of 12.5% for resminostat alone and 62.5% for resminostat plus sorafenib. Median TTP and OS were 1.8 months and 4.1 months for resminostat and 6.5 months and 8.0 months for the combination, respectively [70]. These results support

New therapeutic options are needed for the treatment of HCC despite the availability of sorafenib, which has limited survival benefits in advanced HCC patients. Several clinical trials are investigating the efficacy and tolerability of combining sorafenib with other agents. Future studies should continue to delineate dysregulated signalling pathways in hepatocarcinogenesis to introduce new molecular targets for therapeutic intervention. Simultaneously it is critical to identify biomarkers and/or aberrant genotypes that would predict clinical efficacy to these targeted agents. Much work also remains to evaluate the role of targeted therapy in adjuvant, neoadjuvant or metastatic settings to determine the most suitable combination of treatment. The battle against HCC is far from over and requires a multidisciplinary approach.

respectively. The TTP was 6.5 months [66].

HCC. Romidepsin has not been tested in a clinical setting.

further evaluation of HDAC inhibitors in clinical settings in HCC.

**7. Conclusion**

**6.3. Epigenetic-based therapeutics**

Programed death-1 (PD-1) is a check-point receptor found on CD8<sup>+</sup> T-cells and directs it from attacking other cells in the body. PD-1 binds to PD ligands (PDL)-1 and PDL-2. Cancer cells have high amount of PD-1 and PDL-1 which helps them evade immune response. In HCC, CD8+ T-cells that express PD-1 is much higher in both tumour regions and peripheral blood compared to healthy controls [60, 61]. Additionally, several correlative studies have associated PD-1 and PDL-1 in tumours to be significantly associated with HCC recurrence, and poor prognosis [62, 63]. Monoclonal antibodies against PD-1 and PD-L1 have been developed and are under clinical trials in HCC patients.

Cytotoxic T lymphocyte associated antigen 4 (CTLA-4) is another example of an immune check-point, which serves an inhibitory co-receptor that interferes with T cell activation and proliferation. CTLA-4 pathway downregulates an immune response by binding to CD80. Inhibiting the CTLA-4 pathway leads to T-cell activation and proliferation and may help generate memory T cells. Monoclonal antibody against CTLA-4 are also under trial in HCC [64].

Pembrolizumab and nivolumab are monoclonal antibodies targeting PD-1. A phase II study (KEYNOTE-224, NCT02702414) is currently underway to access the toxicity and activity of pembrolizumab in advanced HCC patients who have been treated with sorafenib. The primary objective of this study is to determine the objective response rate (ORR) of pembrolizumab given as monotherapy. Recently, a case study reported a decrease in tumour size and AFP levels in a 75 year old man with metastatic HCC who was treated pembrolizumab after failure to respond to sorafenib [65]. Another single-arm phase II trial of pembrolizumab is underway (Keytruda, NCT02658019) and is recruiting advanced HCC patients with unresectable HCC. The primary end points of this study are PFS, OS, RR, duration of response and toxicity.

A phase I/II study is underway (CheckMate040, NCT01658878) to evaluate the safety and tolerability of nivolumab. HCC patients who were either not responsive to sorafenib or failed sorafenib are also included in the study. Another phase III study (CheckMate-459, NCT02576509) is recruiting HCC patients to compare nivolumab with sorafenib as a first line treatment for advanced HCC patients.

Durvalumab is a monoclonal antibody targeting PDL-1. A phase II study (NCT02519348) is currently recruiting patients with unresectable HCC to evaluate durvalumab and tremelimumab either alone or in combination.

Tremelimumab is an inhibitor of CTLA-4. In a small pilot clinical trial including 21 patients with metastatic HCV-related HCC, tremelimumab induced a significant decrease in viral load and showed promising partial response rate and disease control rate of 17.6% and 76.4%, respectively. The TTP was 6.5 months [66].

#### **6.3. Epigenetic-based therapeutics**

**6.2. Immunotherapeutics**

escape immune response.

response and toxicity.

treatment for advanced HCC patients.

umab either alone or in combination.

and are under clinical trials in HCC patients.

182 Hepatocellular Carcinoma - Advances in Diagnosis and Treatment

CD8+

Immune checkpoints are emerging as promising targets for treatment of HCC. The immune system helps to distinguish body's own cells from foreign cells. To help it achieve this, immune checkpoints which are molecules on certain immune cells, need to be activated or inactivated to start an immune response. Cancer cells find ways to use such checkpoints to

attacking other cells in the body. PD-1 binds to PD ligands (PDL)-1 and PDL-2. Cancer cells have high amount of PD-1 and PDL-1 which helps them evade immune response. In HCC,

Cytotoxic T lymphocyte associated antigen 4 (CTLA-4) is another example of an immune check-point, which serves an inhibitory co-receptor that interferes with T cell activation and proliferation. CTLA-4 pathway downregulates an immune response by binding to CD80. Inhibiting the CTLA-4 pathway leads to T-cell activation and proliferation and may help generate memory T cells. Monoclonal antibody against CTLA-4 are also under trial in HCC [64]. Pembrolizumab and nivolumab are monoclonal antibodies targeting PD-1. A phase II study (KEYNOTE-224, NCT02702414) is currently underway to access the toxicity and activity of pembrolizumab in advanced HCC patients who have been treated with sorafenib. The primary objective of this study is to determine the objective response rate (ORR) of pembrolizumab given as monotherapy. Recently, a case study reported a decrease in tumour size and AFP levels in a 75 year old man with metastatic HCC who was treated pembrolizumab after failure to respond to sorafenib [65]. Another single-arm phase II trial of pembrolizumab is underway (Keytruda, NCT02658019) and is recruiting advanced HCC patients with unresectable HCC. The primary end points of this study are PFS, OS, RR, duration of

A phase I/II study is underway (CheckMate040, NCT01658878) to evaluate the safety and tolerability of nivolumab. HCC patients who were either not responsive to sorafenib or failed sorafenib are also included in the study. Another phase III study (CheckMate-459, NCT02576509) is recruiting HCC patients to compare nivolumab with sorafenib as a first line

Durvalumab is a monoclonal antibody targeting PDL-1. A phase II study (NCT02519348) is currently recruiting patients with unresectable HCC to evaluate durvalumab and tremelim-

Tremelimumab is an inhibitor of CTLA-4. In a small pilot clinical trial including 21 patients with metastatic HCV-related HCC, tremelimumab induced a significant decrease in viral load

 T-cells that express PD-1 is much higher in both tumour regions and peripheral blood compared to healthy controls [60, 61]. Additionally, several correlative studies have associated PD-1 and PDL-1 in tumours to be significantly associated with HCC recurrence, and poor prognosis [62, 63]. Monoclonal antibodies against PD-1 and PD-L1 have been developed

T-cells and directs it from

Programed death-1 (PD-1) is a check-point receptor found on CD8<sup>+</sup>

Chromatin remodelling is a critical epigenetic mechanism regulating gene expression and plays an important role in cell proliferation, differentiation and DNA repair. Epigenetics alters gene expression without any changes to the DNA sequence and involves the enzymatic covalent modification of histones such as methylation, phosphorylation and acetylation. Histone deacetylases (HDACs) remove the acetyl group from histones, making DNA more compact resulting in gene silencing. There are a total of 18 HDACs identified in mammals. Accumulating evidence suggests the overexpression of HDACs to be correlated advanced tumour stage, recurrence after surgery and poor prognosis in several cancers including HCC [67, 68]. For these reasons HDAC inhibitors may serve as potential therapeutic targets.

Currently 2 HDAC inhibitors have been approved by the FDA i.e. vorinostat and romidepsin, for treatment of cutaneous T cell lymphoma. These inhibitors demonstrate anti-tumour activity by means of histone hyperacetylation reducing DNA-histone affinity and allowing access to transcription factors enhancing gene expression. Currently, a phase I clinical trial (NCT01075113) is underway to evaluate vorinostat in combination with sorafenib in HCC. Romidepsin has not been tested in a clinical setting.

Aberrant up regulation of several HDACs (HDAC1, 2, 3, 4, 5, and 11) and changes in copy number of HDAC3 and HDAC5 have been reported in HCC. Treatment with panobinostat (HDAC inhibitor) demonstrated strong anti-tumour activity *in vitro* and *in vivo* and the effect was enhanced in combination with sorafenib [69]. In a recently completed phase I/II trial (SHELTER, NCT00943449), combination of resminostat (HDAC inhibitor) with sorafenib yielded a progression-free survival-rate of 12.5% for resminostat alone and 62.5% for resminostat plus sorafenib. Median TTP and OS were 1.8 months and 4.1 months for resminostat and 6.5 months and 8.0 months for the combination, respectively [70]. These results support further evaluation of HDAC inhibitors in clinical settings in HCC.
