Phase II trial of the IDO pathway inhibitor indoximod plus pembrolizumab for the treatment of patients with advanced melanoma.

BACKGROUND: The indoleamine 2,3-dioxygenase (IDO) pathway is a key counter-regulatory mechanism that, in cancer, is exploited by tumors to evade antitumor immunity. Indoximod is a small-molecule IDO pathway inhibitor that reverses the immunosuppressive effects of low tryptophan (Trp) and high kynurenine (Kyn) that result from IDO activity. In this study, indoximod was used in combination with a checkpoint inhibitor (CPI) pembrolizumab for the treatment for advanced melanoma. METHODS: Patients with advanced melanoma were enrolled in a single-arm phase II clinical trial evaluating the addition of indoximod to standard of care CPI approved for melanoma. Investigators administered their choice of CPI including pembrolizumab (P), nivolumab (N), or ipilimumab (I). Indoximod was administered continuously (1200 mg orally two times per day), with concurrent CPI dosed per US Food and Drug Administration (FDA)-approved label. RESULTS: Between July 2014 and July 2017, 131 patients were enrolled. (P) was used more frequently (n=114, 87%) per investigator's choice. The efficacy evaluable population consisted of 89 patients from the phase II cohort with non-ocular melanoma who received indoximod combined with (P).The objective response rate (ORR) for the evaluable population was 51% with confirmed complete response of 20% and disease control rate of 70%. Median progression-free survival was 12.4 months (95% CI 6.4 to 24.9). The ORR for Programmed Death-Ligand 1 (PD-L1)-positive patients was 70% compared with 46% for PD-L1-negative patients. The combination was well tolerated, and side effects were similar to what was expected from single agent (P). CONCLUSION: In this study, the combination of indoximod and (P) was well tolerated and showed antitumor efficacy that is worth further evaluation in selected patients with advanced melanoma.

Phase Ia study of the indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor navoximod (GDC-0919) in patients with recurrent advanced solid tumors.

BACKGROUND: Indoleamine-2,3-dioxygenase 1 (IDO1) catalyzes the oxidation of tryptophan into kynurenine and is partially responsible for acquired immune tolerance associated with cancer. The IDO1 small molecule inhibitor navoximod (GDC-0919, NLG-919) is active as a combination therapy in multiple tumor models. METHODS: This open-label Phase Ia study assessed safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary anti-tumor activity of navoximod in patients with recurrent/advanced solid tumors, administered as 50-800 mg BID on a 21/28 day and at 600 mg on a 28/28 day schedule. Plasma kynurenine and tryptophan were longitudinally evaluated and tumor assessments were performed. RESULTS: Patients (n = 22) received a median of 3 cycles of navoximod. No maximum tolerated dose was reached. One dose-limiting toxicity of Grade 4 lower gastrointestinal hemorrhage was reported. Adverse events (AEs) regardless of causality in ≥20% of patients included fatigue (59%), cough, decreased appetite, and pruritus (41% each), nausea (36%), and vomiting (27%). Grade ≥ 3 AEs occurred in 14/22 patients (64%), and were related to navoximod in two patients (9%). Navoximod was rapidly absorbed (Tmax ~ 1 h) and exhibited dose-proportional increases in exposure, with a half-life (t1/2 ~ 11 h) supportive of BID dosing. Navoximod transiently decreased plasma kynurenine from baseline levels with kinetics consistent with its half-life. Of efficacy-evaluable patients, 8 (36%) had stable disease and 10 (46%) had progressive disease. CONCLUSIONS: Navoximod was well-tolerated at doses up to 800 mg BID decreasing plasma kynurenine levels consistent with its half-life. Stable disease responses were observed. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02048709 .

Addition of αGal HyperAcute™ technology to recombinant avian influenza vaccines induces strong low-dose antibody responses.

Highly pathogenic avian influenza represents a severe public health threat. Over the last decade, the demand for highly efficacious vaccines against avian influenza viruses has grown, especially after the 2013 H7N9 outbreak in China that resulted in over 600 human cases with over 200 deaths. Currently, there are several H5N1 and H7N9 influenza vaccines in clinical trials, all of which employ traditional oil-in-water adjuvants due to the poor immunogenicity of avian influenza virus antigens. In this study, we developed potent recombinant avian influenza vaccine candidates using HyperAcute™ Technology, which takes advantage of naturally-acquired anti-αGal immunity in humans. We successfully generated αGal-positive recombinant protein and virus-like particle vaccine candidates of H5N1 and H7N9 influenza strains using either biological or our novel CarboLink chemical αGal modification techniques. Strikingly, two doses of 100 ng αGal-modified vaccine, with no traditional adjuvant, was able to induce a much stronger humoral response in αGT BALB/c knockout mice (the only experimental system readily available for testing αGal in vivo) than unmodified vaccines even at 10-fold higher dose (1000 ng/dose). Our data strongly suggest that αGal modification significantly enhances the humoral immunogenicity of the recombinant influenza vaccine candidates. Use of αGal HyperAcute™ technology allows significant dose-sparing while retaining desired immunogenicity. Our success in the development of highly potent H5N1 and H7N9 vaccine candidates demonstrated the potential of αGal HyperAcute™ technology for the development of vaccines against other infectious diseases.

A phase I study of indoximod in patients with advanced malignancies.

PURPOSE: Indoximod is an oral inhibitor of the indoleamine 2,3-dioxygenase pathway, which causes tumor-mediated immunosuppression. Primary endpoints were maximum tolerated dose (MTD) and toxicity for indoximod in patients with advanced solid tumors. Secondary endpoints included response rates, pharmacokinetics, and immune correlates. EXPERIMENTAL DESIGN: Our 3+3 phase I trial comprised 10 dose levels (200, 300, 400, 600, and 800 mg once/day; 600, 800, 1200, 1600, and 2000 mg twice/day). Inclusion criteria were measurable metastatic solid malignancy, age ≥18 years, and adequate organ/marrow function. Exclusion criteria were chemotherapy ≤ 3 weeks prior, untreated brain metastases, autoimmune disease, or malabsorption. RESULTS: In 48 patients, MTD was not reached at 2000 mg twice/day. At 200 mg once/day, 3 patients previously treated with checkpoint inhibitors developed hypophysitis. Five patients showed stable disease >6 months. Indoximod plasma AUC and Cmax plateaued above 1200mg. Cmax (~12 µM at 2000 mg twice/day) occurred at 2.9 hours, and half-life was 10.5 hours. C reactive protein (CRP) levels increased across multiple dose levels. CONCLUSIONS: Indoximod was safe at doses up to 2000 mg orally twice/day. Best response was stable disease >6 months in 5 patients. Induction of hypophysitis, increased tumor antigen autoantibodies and CRP levels were observed.

Algenpantucel-L immunotherapy in pancreatic adenocarcinoma.

Pancreatic adenocarcinoma is the 4th leading cause of cancer death in the USA and the EU. A minority of patients presents with surgically resectable and potentially curable disease, but among these, 80% are destined to relapse and overall survival rates with adjuvant chemotherapy average 24 months. Immunotherapy is a promising therapeutic option and a potential paradigm shift in the treatment of patients with pancreatic cancer, and may be particularly effective when used early in the disease course to prevent metastatic spread. Algenpantucel-L (HyperAcute Pancreas, NewLink Genetics, Ames, IA, USA) is a whole-cell immunotherapy consisting of irradiated allogeneic pancreatic cancer cells genetically engineered to express the murine enzyme α-GT, which results in hyperacute rejection of the tumor cells with complement- and antibody-dependent cytotoxicity. Phase II clinical trial data has been encouraging, particularly for patients who demonstrated humoral immunologic responses. Here, we report preliminary results and biomarkers correlations with clinical activity of algenpantucel-L in pancreatic cancer.

Pancreatic cancer: Update on immunotherapies and algenpantucel-L.

Pancreatic adenocarcinoma is notoriously lethal, and despite improvements in systemic chemotherapy approaches bringing survival rates for metastatic disease to almost 1 year, by 2030 it is expected to become the second leading cause of cancer death. Pancreatic cancer (PC) prognosis has been associated with both the presence of intratumoral helper and cytotoxic T lymphocytes, as well as humoral immune responses to tumor associated antigens like mesothelin. It is well described that the PC microenvironment is characterized by a fibroinflammatory and immunosuppressive stroma. On these premises several immune-targeted strategies have been developed to harness the adaptable immune system with a goal of improving survival with little toxicity. Cancer vaccines involve the administration of tumor-associated antigens with the goal of inducing an endogenous anti-tumor response. Among several strategies discussed, we will focus on the algenpantucel-L (HyperAcute™ Pancreas) immunotherapy. Algenpantucel-L is a whole cell immunotherapy consisting of irradiated allogeneic PC cells genetically engineered to express the murine enzyme α(1,3)-galactosyltransferase (αGT), which ultimately leads to hyperacute rejection with complement- and antibody-dependent cytotoxicity. While phase III data in the adjuvant treatment of pancreatic cancer are pending, phase II results have been encouraging, particularly for patients who demonstrated humoral immunologic responses. Novel strategies using immune checkpoint inhibitors, costimulatory antibodies, and combinations with cancer vaccines may overcome immunotolerance and improve treatment success.

A first in man phase I trial of the oral immunomodulator, indoximod, combined with docetaxel in patients with metastatic solid tumors.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) is an enzyme that tumors use to create a state of immunosuppression. Indoximod is an IDO pathway inhibitor. Preclinical studies demonstrated that indoximod combined with chemotherapy was synergistic in a mouse model of breast cancer. A phase I 3+3 trial was designed to study the combination of docetaxel and indoximod. METHODS: Docetaxel was administered at 60 mg/m2 intravenously every 3 weeks dose levels 1-4 and 75 mg/m2 for dose level 5. Indoximod was given at 300, 600, 1000, 2000, and 1200 mg PO twice daily continuously for levels 1-5, respectively. Serum drug levels were measured. RESULTS: Twenty-seven patients were treated, with 22 evaluable for response. DLTs included grade 3 dehydration (level 1), hypotension(level 4), mucositis (level 4) and grade 5 enterocolitis (level 2). Dose level 5 is the recommended phase II dose. The most frequent adverse events were fatigue (58.6%), anemia (51.7%), hyperglycemia (48.3%), infection (44.8%), and nausea (41.4%). There were 4 partial responses (2 breast, 1 NSCLC, 1 thymic tumor). No drug-drug interactions were noted. CONCLUSIONS: Docetaxel plus indoximod was well tolerated with no increase in expected toxicities or pharmacokinetic interactions. It was active in a pretreated population of patients with metastatic solid tumors.

Combination immunotherapy for high-risk resected and metastatic melanoma patients.

BACKGROUND: Patients with advanced melanoma have a poor outcome. We hypothesize that combination immunotherapy can synergistically activate host immunity to generate an effective treatment for patients with high-risk, resected stage 3, recurrent, refractory, or stage 4 melanoma. METHODS: We conducted a phase 2 clinical trial of HyperAcute Melanoma (HAM) vaccine (NLG-12036, NewLink Genetics) combined with pegylated interferon (Sylatron, Merck). Trial design consisted of a 12-week regimen with the initial 4 weekly treatments consisting of HAM alone (intradermally) followed by 8 additional treatments of HAM plus Sylatron (subcutaneously, 6 µg/kg). Trial endpoint outcomes include clinical response, overall safety, and correlative findings for observed antitumor effect. RESULTS: Our cohort consisted of 25 patients with a median age of 60. Twenty-one patients completed the trial and 4 stopped because of progressive disease (PD). According to the Response Evaluation Criteria in Solid Tumors, of the 16 stage 4 patients, 2 had a complete response (CR), 1 had stable disease, and 4 had no evidence of disease (NED) after resection. For stage 2/3 patients, 3 of 9 remained NED, and the 1 stage 2C patient had slow PD with a single site resected and is currently NED. The median overall survival time was 29 months, with 60% of the patients surviving for >1 year. Of the 25 patients, 12 (48%) are still alive. All evaluable patients (21/21) seroconverted, developing autoimmune antibodies. Four of 25 patients developed vitiligo, correlating with 2 CR patients and 2 NED patients. CONCLUSION: Combination immunotherapy with HAM plus Sylatron shows clinical efficacy with tumor regression and concomitant immune activation. Optimization of dosing schedules and therapeutic efficacy should be further explored to enhance the benefit of this promising immunotherapeutic approach.

Cellular immunotherapy study of prostate cancer patients and resulting IgG responses to peptide epitopes predicted from prostate tumor-associated autoantigens.

The immunogenicity of a cellular immunotherapy using genetically modified vaccines to express α(1,3)galactosyl epitopes (αGal) was evaluated in advanced prostate cancer (PC) patients. In this dose escalation phase I study, we report safety, feasibility, and immunologic data of an immunotherapy composed of 2 human PC cell lines engineered to express αGal epitopes (HyperAcute-Prostate, HAP, NewLink Genetics). Eight patients received up to 12 biweekly vaccinations with HAP. Enrolled patients (aged range, 53-85 y) had American Joint Committee on Cancer stage IV, any T, any N, M1, Eastern Cooperative Oncology Group PS≤2, at least 1 prior hormonal treatment and <3 prior chemotherapies, adequate bone marrow and organ function, and albumin ≥3.0 g/dL. Serum IgG antibodies to synthetic peptides overexpressed in PC were determined by enzyme-linked immunosorbent assay. Results indicate that HAP immunotherapy induced humoral immune responses to autoantigens in 2 of 8 patients. These patients developed IgG antibody to multiple epitopes overexpressed in PC after immunization. These responding patients received higher doses of the immunotherapy suggesting a dose response. Two immunogenic proteins (prostate-specific membrane antigen, hepsin) belong to the extracellular molecules family participating in malignant cell invasion. Median overall survival for patients was 25.1 months with 1 patient surviving over 70 months with stable PSA and bone metastasis before expiring of other causes. Three of 8 patients showed PSA stabilization (>100 d). In conclusion, HAP immunotherapy induces IgG responses to epitopes from autoantigens overexpressed in PC suggesting dose-dependent effect. HAP represents a viable immunotherapy approach to induce immune responses against tumor cells and may provide clinical benefit with minimal toxicity.

IDO inhibits a tryptophan sufficiency signal that stimulates mTOR: A novel IDO effector pathway targeted by D-1-methyl-tryptophan.

Tryptophan catabolism by indoleamine 2,3-dioxygenase (IDO) alters inflammation and favors T-cell tolerance in cancer, but the underlying molecular mechanisms remain poorly understood. The integrated stress response kinase GCN2, a sensor of uncharged tRNA that is activated by amino acid deprivation, is recognized as an important effector of the IDO pathway. However, in a mouse model of inflammatory carcinogenesis, ablation of Gcn2 did not promote resistance against tumor development like the absence of IDO does, implying the existence of additional cancer-relevant pathways that operate downstream of IDO. Addressing this gap in knowledge, we report that the IDO-mediated catabolism of tryptophan also inhibits the immunoregulatory kinases mTOR and PKC-Θ, along with the induction of autophagy. These effects were relieved specifically by tryptophan but also by the experimental agent 1-methyl-D-tryptophan (D-1MT, also known as NLG8189), the latter of which reversed the inhibitory signals generated by IDO with higher potency. Taken together, our results implicate mTOR and PKC-Θ in IDO-mediated immunosuppressive signaling, and they provide timely insights into the unique mechanism of action of D-1MT as compared with traditional biochemical inhibitors of IDO. These findings are important translationally, because they suggest broader clinical uses for D-1MT against cancers that overexpress any tryptophan catabolic enzyme (IDO, IDO2 or TDO). Moreover, they define mTOR and PKC-Θ as candidate pharmacodynamic markers for D-1MT responses in patients recruited to ongoing phase IB/II cancer trials, addressing a current clinical need.

A replication-incompetent Rift Valley fever vaccine: chimeric virus-like particles protect mice and rats against lethal challenge.

Virus-like particles (VLPs) present viral antigens in a native conformation and are effectively recognized by the immune system and therefore are considered as suitable and safe vaccine candidates against many viral diseases. Here we demonstrate that chimeric VLPs containing Rift Valley fever virus (RVFV) glycoproteins G(N) and G(C), nucleoprotein N and the gag protein of Moloney murine leukemia virus represent an effective vaccine candidate against Rift Valley fever, a deadly disease in humans and livestock. Long-lasting humoral and cellular immune responses are demonstrated in a mouse model by the analysis of neutralizing antibody titers and cytokine secretion profiles. Vaccine efficacy studies were performed in mouse and rat lethal challenge models resulting in high protection rates. Taken together, these results demonstrate that replication-incompetent chimeric RVF VLPs are an efficient RVFV vaccine candidate.

Hematopoietic mixed chimerism derived from allogeneic embryonic stem cells prevents autoimmune diabetes mellitus in NOD mice.

Embryonic stem cell (ESC)-derived hematopoietic stem cells (HSC), unlike HSC harvested from the blood or marrow, are not contaminated by lymphocytes. We therefore evaluated whether ESC-derived HSC could produce islet cell tolerance, a phenomenon termed graft versus autoimmunity (GVA), without causing the usual allogeneic hematopoietic stem cell transplant complication, graft-versus-host disease (GVHD). Herein, we demonstrate that ESC-derived HSC may be used to prevent autoimmune diabetes mellitus in NOD mice without GVHD or other adverse side effects. ESC were cultured in vitro to induce differentiation toward HSC, selected for c-kit expression, and injected either i.v. or intra-bone marrow (IBM) into sublethally irradiated NOD/LtJ mice. Nine of 10 mice from the IBM group and 5 of 8 from the i.v. group did not become hyperglycemic, in contrast to the control group, in which 8 of 9 mice developed end-stage diabetes. All mice with >5% donor chimerism remained free of diabetes and insulitis, which was confirmed by histology. Splenocytes from transplanted mice were unresponsive to glutamic acid decarboxylase isoform 65, a diabetic-specific autoantigen, but responded normally to third-party antigens. ESC-derived HSC can induce an islet cell tolerizing GVA effect without GVHD. This study represents the first instance, to our knowledge, of ESC-derived HSC cells treating disease in an animal model.