*2.1.1.4 Conclusions/future directions*

*Advances in Precision Medicine Oncology*

(PFS) in patients with advanced sarcoma [16].

6 months of treatment.

Events (CTCAE) version 5.0.

*Society Meetings, November, 2020*

rate: 51%), while the median OS was >17.0 months.

*2.1.1.2 Methods*

This group accounts for only 1% of adult cancers in the United States, but it has a higher mortality rate than testicular cancer, thyroid cancer, and Hodgkin lymphoma combined [12]. The most commonly used modalities of treatment for sarcoma have been surgery, radiation and chemotherapy. Currently, chemotherapy treatment options have been shown to slow down disease progression but are ineffective in keeping most patients from eventually developing recurrent and metastatic disease [13]. Once unresectable or metastatic, the majority of soft tissue sarcomas remain incurable with chemotherapy. Immune checkpoint blockades do not act directly on the cancer cell, thus they can theoretically be applied to the treatment of any type of solid tumor, including the rarest and most aggressive malignancies. The precedent set by the approval of immune checkpoint inhibition for the treatment of numerous cancer types provides a strong rationale for studying their effects on soft tissue sarcoma. Studies with ipilimumab and nivolumab have since been done showing promising results when used in patients with advanced soft tissue sarcoma [14]. The third drug in this trial is a marine-derived alkaloid, trabectedin, an FDA approved chemotherapy treatment for leiomyosarcoma and liposarcoma [15]. A recently published retroactive analysis of 442 patients treated with trabectedin over a 10 year period confirms that trabectedin can prolong progression free survival

Gordon et al. designed the SAINT protocol based on the fact that sarcoma cells

are most immunogenic early in the disease process [17] and prior to any other treatment, allowing immune checkpoint inhibitors to exploit this advantage and deploy the immune system to recognize and destroy them. This study was designed to evaluate the best objective response rates (BORR) assessed via CT scan or MRI and to assess the overall survival (OS) and progression-free survival (PFS) after

Eligible patients for this Phase II clinical trial were treatment-naïve adult patients with advanced unresectable or metastatic soft tissue sarcoma. Trabectedin was administered to the study subjects at the maximum tolerated dose determined previously in the dose escalation phase of this trial. Ipilimumab and nivolumab were be administered at defined doses in order to assess the overall safety profile and potential efficacy of this treatment regimen. Patients continued on the treatment until they experienced significant disease progression or unmanageable toxicities. Best objective response was measured according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 using CT scan or MRI. Median progression-free survival (PFS) and overall survival (OS) were also measured in months. Adverse events were assessed and categorized as related or unrelated to the treatment and listed by severity according to the Common Terminology Criteria for Adverse

*2.1.1.3 Preliminary results were presented at the Connective Tissue Oncology* 

Sixty subjects were evaluated using RECIST v1.1 for analysis of treatment efficacy. Twenty-five percent (25%) had either a complete response (11.7%) or a partial response (13.3%), and 37 patients (61.7%) had stable disease. Disease control rate was 86.6%. The median PFS was >6.7 months (6-month OS rate: 90%; 6-month PFS

Grade 3 TRAEs included fatigue (n = 6), adrenal insufficiency (n = 1), hyperglycemia (n = 1), dehydration (n = 1), hyponatremia (n = 2), bipedal edema (n = 2),

**6**

The positive results from this trial thus far strongly suggest that using combination therapy with ipilimumab, nivolumab, and trabectedin as first-line treatment in patients with advanced or metastatic sarcoma allows the treatments to engage synergistically without causing any additive toxicities. This combination may be superior to known therapies for STS. Overall, the adverse events experienced less severe than toxicities typically experienced with standard first line treatment (doxorubicin/ifosfamide) for metastatic soft tissue sarcoma. Future Phase 3 randomized studies are proposed to evaluate the safety and efficacy of first-line combinatorial therapy with ipilimumab, nivolumab and trabectedin in comparison to standard therapy for patients with advanced soft tissue sarcomas.

*2.1.2 The TNT Protocol: A Phase II Study Using Talimogene Laherparepvec, Nivolumab, and Trabectedin as First, Second/Third Line Therapy for Advanced Sarcoma, including Desmoid Tumor and Chordoma (NCT03886311). Sant P. Chawla and Erlinda M. Gordon, co-Principal Investigators*

### *2.1.2.1 Background & rationale*

The significant immunotherapeutic potential of oncolytic virotherapy is due to its ability to induce a multifaceted anti-tumor response involving aspects of both the innate and adaptive immune systems [18]. A multitude of viral vectors have been explored for their potential oncolytic properties, particularly as a method of delivering targeted treatment to sites of malignant disease [19]. The ability to genetically modify these viruses to target and exploit essential oncogenic signaling pathways has kept them at the forefront of immuno-oncology research [20]. This particular vulnerability triggers selective replication of the viral genome and directly contributes to furthering the oncolytic process. Infected tumor cells secrete viral progeny composed in part by tumor-associated antigens and neoantigens in response to their infection, causing the innate immune system to activate an NK cell-mediated cytotoxic response. The tumor-associated antigens that are released into the tumor microenvironment are phagocytosed by antigen-presenting cells, thus initiating the process of T-cell-mediated adaptive anti-tumor immunity. In addition to the anti-tumor response, the presence of the oncolytic virus also triggers a concurrent anti-viral response, and regulatory mechanisms become crucial to ensuring a controlled immune response, including the upregulation of immune checkpoints [20].

Oncolytic viruses derived from Herpes simplex virus 1 (HSV-1) vectors are amongst the most frequently investigated in pre-clinical trials and have been shown to encompass the combined ability to induce oncolysis and anti-tumor immune responses simultaneously [21]. Talimogene Laherparepvec (T-VEC) is an injectable live, attenuated, oncolytic HSV-1 virus that has been genetically engineered to express human granulocyte-macrophage colony-stimulating factor (huGM-CSF), a known immune modulator and hematopoietic growth factor that stimulates the

#### *Advances in Precision Medicine Oncology*

differentiation of multipotent progenitor cells and plays a key role in the functional abilities of many different circulating lymphocytes, including T-cells [22].

The objective of this ongoing study is to evaluate the potentially synergistic effects T-VEC may evoke when used in combination with anti-PD-L1 monoclonal antibody, nivolumab and marine derived alkaloid, trabectedin. The study is ongoing.

#### *2.1.2.2 Methods*

This open-label Phase II study is designed to assess the safety and efficacy of this combination treatment. This will be accomplished by determining the median month of progression-free survival, median duration of response, and best overall response rates based on each patients' percent of change in their tumor sizes. This study plans to enroll 40 participants with advanced disease who have at least one tumor that is easily accessible for intratumoral injection with T-VEC. Regarding the statistical analysis, continuous variables will be summarized by the sample size (n) and measures of central tendency and variation will be calculated including mean, standard deviation, first and third quartiles, maximum and minimum. Categorical variables will be summarized by the sample and by the percent in each category. "Point estimates for efficacy endpoint incidences will be accompanied by a 2-sided 95% exact binomial CI. Time to event endpoints will be summarized descriptively using the KM method. Safety (incidence and severity of adverse events and significant laboratory abnormalities) will be performed on all patients (ITT population). Patient incidence of all treatment emergent AEs will be tabulated by system organ class and preferred term" [23].

### *2.1.2.3 Preliminary results presented at the Connective Tissue Oncology Society meetings, November, 2020*

Efficacy analysis (n = 31): There were 6.5% partial responses, 80.6% disease control rate, with 74.1% PFS rate and 92.6% OS rate at 4 months.

Safety Analysis (n = 41): Grade 3 TRAEs include fatigue (n = 2), decreased ejection fraction (n = 1), anasarca (n = 1), dehydration (n = 1), decreased cortisol (n = 1), anemia (n = 9), thrombocytopenia (n = 4), neutropenia (n = 4), gastroenteritis (n = 1), increased ALT (n = 8), increased AST (n = 1), and increased GGT (n = 1). Grade 4 TRAEs observed were thrombocytopenia (n = 2). There was no conversion from unresectable to resectable tumor. There were thirty-one evaluable subjects for efficacy analysis.

#### *2.1.2.4 Conclusions/future directions*

Second- or third- line combinatorial therapy with talimogene laherparepvec, nivolumab, and trabectedin.


#### *2.1.2.4.1 Future directions for research*

Studies are proposed to evaluate the efficacy and safety of first, second/ third line combinatorial therapy with talimogene laherparepvec, nivolumab and

**9**

*2.1.3.2 Methods*

*Immune and Cell Cycle Checkpoint Inhibitors for Cancer Immunotherapy*

clinical outcomes for patients with advanced sarcoma.

trabectedin vs. standard therapy (doxorubicin/ifosfamide) in randomized studies

Aberrant mTOR signaling, typically due to either an activating mutation in oncogenes related to the mTOR pathway or a loss of function mutation in an upstream tumor suppressor gene, has been found to play a significant, multifaceted role in oncogenesis [24, 25]. Originally discovered while investigating the targets of the drug rapamycin, a potent immunosuppressive agent, in the early 1990's, the protein kinase, mammalian target of rapamycin (mTOR), is a major signaling hub for directing cellular growth, metabolism, and proliferation [26]. While studying the mechanism of action behind rapamycin's inhibitory effects on mTOR signaling, the drug was also found to be involved in the inhibition of T-cell proliferation, specifically between the G1 and S phases of the cell cycle. This finding launched a multitude of studies to better understand the role of mTOR signaling in T-cell activation and proliferation [27], culminating in the discovery that T-cells are also highly dependent on mTOR signaling to maintain normal T-cell activation and proliferation [28]. When t-cells receive immune stimuli, they then rely on signals from mTOR to promote t-helper cell differentiation while simultaneously inhibiting the induction of regulatory T-cells. Thus, mTOR exerts control over essential regulatory signals in both adaptive and innate immunity. Initial clinical studies investigating the anti-cancer effects of single agent mTOR inhibitor, were disappointing, reporting its limited effects, thus leading to the investigation of rapamycin in combination with various chemotherapy agents where it was successful in inhibiting cancer growth in prostate cancer patients [29]. However, the experimental drug, ABI-009 or nab-sirolimus, a novel albuminbound mTOR inhibitor, has been shown to be effective and safe for the treatment of malignant perivascular epithelioid cell tumors (PEComa) [30]. A phase 1/2 trial is currently ongoing to investigate the potential synergistic activity of nab-sirolimus when administered with an immune checkpoint inhibitor, nivolumab, in improving

The original objectives of the study are: (1) To investigate the maximum tolerated dose (MTD) of ABI-009 when given with nivolumab, a PD-1 inhibitor, in previously treated advanced undifferentiated pleomorphic sarcoma, liposarcoma, chondrosarcoma, osteosarcoma and Ewing sarcoma; (2) To investigate the disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) of this combination therapy in the aforementioned patient group, and (3) To correlate

This is an IRB approved protocol with 2 parts. The phase 1 part is a dose-finding

, and sequentially

. Phase 2 of the study will enroll 31 addi-

study using the "cohort of three design", wherein a standard dose of nivolumab 240 mg is given IV every 3 weeks (day 1 of every 21-day cycle). Escalating doses of ABI-009 are given IV on days 8 and 15 of each cycle starting in Cycle 2 following the

PFS with PD-L1 and other biomarker expression in patients' tumors.

2nd nivolumab dose. The starting dose of ABI-009 is 56 mg/m2

tional patients to further assess efficacy and safety at the MTD.

escalating doses are 75, and 100 mg/m2

*2.1.3 A Phase Ib investigation of safety/efficacy of nivolumab and ABI-009 (nabrapamycin) in advanced undifferentiated pleomorphic sarcoma (UPS), liposarcoma (LPS), chondrosarcoma (CS), osteosarcoma (OS) and Ewing sarcoma (NCT03190174). Erlinda M. Gordon, Principal Investigator*

*DOI: http://dx.doi.org/10.5772/intechopen.96664*

for advanced soft tissue sarcomas.

*2.1.3.1 Background & rationale*

*Immune and Cell Cycle Checkpoint Inhibitors for Cancer Immunotherapy DOI: http://dx.doi.org/10.5772/intechopen.96664*

trabectedin vs. standard therapy (doxorubicin/ifosfamide) in randomized studies for advanced soft tissue sarcomas.

*2.1.3 A Phase Ib investigation of safety/efficacy of nivolumab and ABI-009 (nabrapamycin) in advanced undifferentiated pleomorphic sarcoma (UPS), liposarcoma (LPS), chondrosarcoma (CS), osteosarcoma (OS) and Ewing sarcoma (NCT03190174). Erlinda M. Gordon, Principal Investigator*

#### *2.1.3.1 Background & rationale*

*Advances in Precision Medicine Oncology*

class and preferred term" [23].

subjects for efficacy analysis.

nivolumab, and trabectedin.

disease control.

*2.1.2.4 Conclusions/future directions*

coma with no unexpected toxicities.

*2.1.2.4.1 Future directions for research*

*meetings, November, 2020*

*2.1.2.2 Methods*

differentiation of multipotent progenitor cells and plays a key role in the functional

The objective of this ongoing study is to evaluate the potentially synergistic effects T-VEC may evoke when used in combination with anti-PD-L1 monoclonal antibody, nivolumab and marine derived alkaloid, trabectedin. The study is ongoing.

This open-label Phase II study is designed to assess the safety and efficacy of this combination treatment. This will be accomplished by determining the median month of progression-free survival, median duration of response, and best overall response rates based on each patients' percent of change in their tumor sizes. This study plans to enroll 40 participants with advanced disease who have at least one tumor that is easily accessible for intratumoral injection with T-VEC. Regarding the statistical analysis, continuous variables will be summarized by the sample size (n) and measures of central tendency and variation will be calculated including mean, standard deviation, first and third quartiles, maximum and minimum. Categorical variables will be summarized by the sample and by the percent in each category. "Point estimates for efficacy endpoint incidences will be accompanied by a 2-sided 95% exact binomial CI. Time to event endpoints will be summarized descriptively using the KM method. Safety (incidence and severity of adverse events and significant laboratory abnormalities) will be performed on all patients (ITT population). Patient incidence of all treatment emergent AEs will be tabulated by system organ

*2.1.2.3 Preliminary results presented at the Connective Tissue Oncology Society* 

control rate, with 74.1% PFS rate and 92.6% OS rate at 4 months.

Efficacy analysis (n = 31): There were 6.5% partial responses, 80.6% disease

Safety Analysis (n = 41): Grade 3 TRAEs include fatigue (n = 2), decreased ejection fraction (n = 1), anasarca (n = 1), dehydration (n = 1), decreased cortisol (n = 1), anemia (n = 9), thrombocytopenia (n = 4), neutropenia (n = 4), gastroenteritis (n = 1), increased ALT (n = 8), increased AST (n = 1), and increased GGT (n = 1). Grade 4 TRAEs observed were thrombocytopenia (n = 2). There was no conversion from unresectable to resectable tumor. There were thirty-one evaluable

Second- or third- line combinatorial therapy with talimogene laherparepvec,

1.may be equal or better than standard second/third line therapy in achieving

2.may be safer than standard therapy for patients with advanced soft tissue sar-

Studies are proposed to evaluate the efficacy and safety of first, second/ third line combinatorial therapy with talimogene laherparepvec, nivolumab and

abilities of many different circulating lymphocytes, including T-cells [22].

**8**

Aberrant mTOR signaling, typically due to either an activating mutation in oncogenes related to the mTOR pathway or a loss of function mutation in an upstream tumor suppressor gene, has been found to play a significant, multifaceted role in oncogenesis [24, 25]. Originally discovered while investigating the targets of the drug rapamycin, a potent immunosuppressive agent, in the early 1990's, the protein kinase, mammalian target of rapamycin (mTOR), is a major signaling hub for directing cellular growth, metabolism, and proliferation [26]. While studying the mechanism of action behind rapamycin's inhibitory effects on mTOR signaling, the drug was also found to be involved in the inhibition of T-cell proliferation, specifically between the G1 and S phases of the cell cycle. This finding launched a multitude of studies to better understand the role of mTOR signaling in T-cell activation and proliferation [27], culminating in the discovery that T-cells are also highly dependent on mTOR signaling to maintain normal T-cell activation and proliferation [28]. When t-cells receive immune stimuli, they then rely on signals from mTOR to promote t-helper cell differentiation while simultaneously inhibiting the induction of regulatory T-cells. Thus, mTOR exerts control over essential regulatory signals in both adaptive and innate immunity.

Initial clinical studies investigating the anti-cancer effects of single agent mTOR inhibitor, were disappointing, reporting its limited effects, thus leading to the investigation of rapamycin in combination with various chemotherapy agents where it was successful in inhibiting cancer growth in prostate cancer patients [29]. However, the experimental drug, ABI-009 or nab-sirolimus, a novel albuminbound mTOR inhibitor, has been shown to be effective and safe for the treatment of malignant perivascular epithelioid cell tumors (PEComa) [30]. A phase 1/2 trial is currently ongoing to investigate the potential synergistic activity of nab-sirolimus when administered with an immune checkpoint inhibitor, nivolumab, in improving clinical outcomes for patients with advanced sarcoma.

#### *2.1.3.2 Methods*

The original objectives of the study are: (1) To investigate the maximum tolerated dose (MTD) of ABI-009 when given with nivolumab, a PD-1 inhibitor, in previously treated advanced undifferentiated pleomorphic sarcoma, liposarcoma, chondrosarcoma, osteosarcoma and Ewing sarcoma; (2) To investigate the disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) of this combination therapy in the aforementioned patient group, and (3) To correlate PFS with PD-L1 and other biomarker expression in patients' tumors.

This is an IRB approved protocol with 2 parts. The phase 1 part is a dose-finding study using the "cohort of three design", wherein a standard dose of nivolumab 240 mg is given IV every 3 weeks (day 1 of every 21-day cycle). Escalating doses of ABI-009 are given IV on days 8 and 15 of each cycle starting in Cycle 2 following the 2nd nivolumab dose. The starting dose of ABI-009 is 56 mg/m2 , and sequentially escalating doses are 75, and 100 mg/m2 . Phase 2 of the study will enroll 31 additional patients to further assess efficacy and safety at the MTD.

### *2.1.3.3 Preliminary results presented at the ASCO annual meeting in June, 2019*

The Phase I part of study included 9 patients who were treated successfully at 3 dose levels. No dose-limiting toxicities (DLTs) were observed, the MTD was not reached, and 100 mg/m<sup>2</sup> ABI-009 was designated as the recommended Phase II dose. Safety analysis: At Dose 1 (n = 3): Grade 3 treatment-related adverse events (TRAEs) included dyslipidemia (n = 1) and hyperglycemia (n = 1). At Dose 2 (n = 3): Grade 3 TRAEs included increased ALT (n = 1). At Dose 3 (n = 3): Grade 3 TRAEs included hypophosphatemia (n = 1).

### *2.1.3.4 Conclusions/future directions*

The primary endpoint has been met with no DLTs, the MTD was not reached and Dose 3 (100 mg/m2) of ABI-009 has been designated as the phase 2 dose which is on-going.

#### **2.2 Company sponsored clinical research**

*2.2.1 Phase I Study of INBRX-109 in Subjects With Locally Advanced or Metastatic Solid Tumors Including Sarcomas (NCT03715933) Sant P. Chawla, Principal Investigator*

### *2.2.1.1 Background & rationale*

The initiation of the extrinsic apoptosis pathway is mediated by several death domain receptors including death receptor 5 (DR5), a transmembrane protein receptor activated by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) [31]. The DR5 apoptosis pathway naturally occurs to rid the body of neoplastic cells and is known to be crucial in immune system surveillance against cancer growth and metastasis. Normally, when an anchorage-dependent cell becomes detached, the cell will undergo a process of detachment-induced apoptosis called anoikis, initiated by a death receptor-mediated apoptotic pathway. A reduction in DR5 expression was found in melanoma tumor samples, strongly implying the TRAIL/DR5 pathway is associated with the prevention of tumor metastasis [32]. In 1999, Walczak et al. observed tumor cells to have a significantly higher sensitivity to TRAIL than normal cells, emphasizing its potential as a therapeutic cancer agent [33]. The subsequent development of agonistic antibodies against DR5 (i.e. recombinant human TRAIL proteins) was shown to be successful in stimulating apoptosis when tested in various tumor cell lines, and was later also shown to enhance the efficacy of chemotherapy and radiotherapy [34].

INBRX-109 is a tetravalent DR5 agonist antibody designed to initiate the DR5 apoptosis pathway and precisely engineered to avoid unnecessary crosslinking to lower the risk of hepatotoxicity.

#### *2.2.1.2 Methods*

This is the first in-human, open-label, non-randomized Phase I clinical trial for INBRX-109. Eligible patients had metastatic or unresectable solid tumors refractory to standard treatment or for which there is no FDA approved standard treatment. Phase I consists of two parts, part 1 being a 3 + 3 dose escalation cohort and part 2 being a dose expansion cohort. Safety, tolerability and dose-limiting toxicity were measured and analyzed using the National Cancer Institute's Common Terminology

**11**

*Immune and Cell Cycle Checkpoint Inhibitors for Cancer Immunotherapy*

activity and was reported according to RECIST v1.1 standard.

*2.2.1.3 Preliminary results presented at the CTOS meeting, November, 2020*

Criteria for Adverse Events (CTCAE) criteria to assess the severity of adverse events experienced. This study's exploratory objective is an assessment of anti-tumor

Overall, INBRX-109 was well tolerated and approximately 90% of patients showed no signs of hepatotoxicity. The pharmacokinetics of INBRX-109 were approximately dose proportional across all doses tested and thus support dosing every 3 weeks without administration of any premedications. All patients have thus far tested negative for anti-drug antibodies. Maximum tolerated dose was not reached in the dose escalation cohort and only one dose-limiting toxicity was experienced. Very few serious adverse events that occurred were attributable to the drug being studied. One patient with mesothelioma has been reported to have experienced acute hepatic failure leading to death that could possibly be related to the study drug. Evidence of anti-cancer effects were observed in patients with chondrosarcoma, resulting in durable partial responses and stable disease.

NBRX-109, a precisely engineered tetravalent DR5 agonist antibody, showed promising results that warrant further exploration. The pharmacokinetics of INBRX-109 were essentially dose-proportional across all three dose levels, supporting dosing every three weeks with no premedications necessary. Specifically, the chondrosarcoma cohort of this Phase I study has been expanded to include twenty

Unregulated angiogenesis is one of the key characteristics of malignant tumors [35]. In addition to creating neovasculature, tumor angiogenesis plays a key role in creating an immunosuppressive tumor microenvironment by causing an accumulation of pro-tumor immune cells and a decrease in the abundance and function of anti-tumor immune cells. Anti-angiogenic cancer treatments have been shown to reverse this process, essentially 'reprogramming' the tumor microenvironment by converting it from an immunosuppressive to an immunogenic one. This has been accomplished by targeting and inhibiting vascular endothelial growth factor (VEGF), a well-known cell surface-signaling proangiogenic protein that becomes stimulated when bound to tyrosine kinase receptors. With the use of antiangiogenic small molecule tyrosine kinase inhibitors (TKIs), VEGF can be blocked from binding its receptor, stopping the tumor from being able to continue to create neovasculature [36]. However, cancer has been able to circumvent this blockade using multiple other pathways, suggesting the use of antiangiogenic therapies that inhibit

The experimental drug, apatinib, is a highly selective VEGFR-2 TKI, administered orally, that has already been approved in China for ≥3rd-line treatment for advanced gastric cancer. The potential benefit of combining TKI and PD-1 therapies has been demonstrated in preclinical murine models, suggesting that

*2.2.2 An Open-labeled, Phase I Study to Evaluate the Safety and Tolerability of Apatinib with Nivolumab in Patients with Unresectable or Metastatic* 

*Cancer (NCT03396211) Sant P. Chawla, Principal Investigator*

*DOI: http://dx.doi.org/10.5772/intechopen.96664*

*2.2.1.4 Conclusions/future directions*

patients and is currently ongoing.

*2.2.2.1 Background & rationale*

more than one signaling pathway simultaneously.

Criteria for Adverse Events (CTCAE) criteria to assess the severity of adverse events experienced. This study's exploratory objective is an assessment of anti-tumor activity and was reported according to RECIST v1.1 standard.
