Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM

Multiple sclerosis (MS) is a heterogenous autoimmune disease in which autoreactive lymphocytes attack the myelin sheath of the central nervous system. B lymphocytes in the cerebrospinal fluid (CSF) of patients with MS contribute to inflammation and secrete oligoclonal immunoglobulins^1,2. Epstein-Barr virus (EBV) infection has been epidemiologically linked to MS, but its pathological role remains unclear³. Here we demonstrate high-affinity molecular mimicry between the EBV transcription factor EBV nuclear antigen 1 (EBNA1) and the central nervous system protein glial cell adhesion molecule (GlialCAM) and provide structural and in vivo functional evidence for its relevance. A cross-reactive CSF-derived antibody was initially identified by single-cell sequencing of the paired-chain B cell repertoire of MS blood and CSF, followed by protein microarray-based testing of recombinantly expressed CSF-derived antibodies against MS-associated viruses. Sequence analysis, affinity measurements and the crystal structure of the EBNA1-peptide epitope in complex with the autoreactive Fab fragment enabled tracking of the development of the naive EBNA1-restricted antibody to a mature EBNA1-GlialCAM cross-reactive antibody. Molecular mimicry is facilitated by a post-translational modification of GlialCAM. EBNA1 immunization exacerbates disease in a mouse model of MS, and anti-EBNA1 and anti-GlialCAM antibodies are prevalent in patients with MS. Our results provide a mechanistic link for the association between MS and EBV and could guide the development of new MS therapies.

Off-the-shelf Vδ1 gamma delta T cells engineered with glypican-3 (GPC-3)-specific chimeric antigen receptor (CAR) and soluble IL-15 display robust antitumor efficacy against hepatocellular carcinoma

BACKGROUND

Glypican-3 (GPC-3) is an oncofetal protein that is highly expressed in various solid tumors, but rarely expressed in healthy adult tissues and represents a rational target of particular relevance in hepatocellular carcinoma (HCC). Autologous chimeric antigen receptor (CAR) αβ T cell therapies have established significant clinical benefit in hematologic malignancies, although efficacy in solid tumors has been limited due to several challenges including T cell homing, target antigen heterogeneity, and immunosuppressive tumor microenvironments. Gamma delta (γδ) T cells are highly cytolytic effectors that can recognize and kill tumor cells through major histocompatibility complex (MHC)-independent antigens upregulated under stress. The Vδ1 subset is preferentially localized in peripheral tissue and engineering with CARs to further enhance intrinsic antitumor activity represents an attractive approach to overcome challenges for conventional T cell therapies in solid tumors. Allogeneic Vδ1 CAR T cell therapy may also overcome other hurdles faced by allogeneic αβ T cell therapy, including graft-versus-host disease (GvHD).

METHODS

We developed the first example of allogeneic CAR Vδ1 T cells that have been expanded from peripheral blood mononuclear cells (PBMCs) and genetically modified to express a 4-1BB/CD3z CAR against GPC-3. The CAR construct (GPC-3.CAR/secreted interleukin-15 (sIL)-15) additionally encodes a constitutively-secreted form of IL-15, which we hypothesized could sustain proliferation and antitumor activity of intratumoral Vδ1 T cells expressing GPC-3.CAR.

RESULTS

GPC-3.CAR/sIL-15 Vδ1 T cells expanded from PBMCs on average 20,000-fold and routinely reached >80% purity. Expanded Vδ1 T cells showed a primarily naïve-like memory phenotype with limited exhaustion marker expression and displayed robust in vitro proliferation, cytokine production, and cytotoxic activity against HCC cell lines expressing low (PLC/PRF/5) and high (HepG2) GPC-3 levels. In a subcutaneous HepG2 mouse model in immunodeficient NSG mice, GPC-3.CAR/sIL-15 Vδ1 T cells primarily accumulated and proliferated in the tumor, and a single dose efficiently controlled tumor growth without evidence of xenogeneic GvHD. Importantly, compared with GPC-3.CAR Vδ1 T cells lacking sIL-15, GPC-3.CAR/sIL-15 Vδ1 T cells displayed greater proliferation and resulted in enhanced therapeutic activity.

CONCLUSIONS

Expanded Vδ1 T cells engineered with a GPC-3 CAR and sIL-15 represent a promising platform warranting further clinical evaluation as an off-the-shelf treatment of HCC and potentially other GPC-3-expressing solid tumors.

Correlations between macrophage/microglial activation marker sTREM-2 and measures of T-cell activation, neuroaxonal damage and disease severity in multiple sclerosis

Background

Soluble triggering receptor expressed on myeloid cells-2 (sTREM-2) is a marker of macrophage and microglial activation and is increased in the cerebrospinal fluid (CSF) in multiple sclerosis (MS).

Objective

To determine the relationships among sTREM-2, T cell activation, neuroaxonal damage and clinical features of MS.

Methods

Enzyme-linked immunosorbent assays were used to measure the levels of sTREM-2, soluble CD27 (sCD27, a marker of T cell activation), neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH) in the CSF of 42 patients with MS (including nine with clinically isolated syndrome) and 15 patients with other neurological diseases (OND) and in the serum of 164 patients with MS, 87 patients with OND and 62 healthy controls.

Results

sTREM-2 was significantly elevated in the CSF (p = 0.012), but not in the serum, in MS compared to OND. In MS, CSF sTREM-2 correlated positively with CSF sCD27 (p = 0.005), CSF NfL (p = 0.0001), CSF pNfH (p = 0.0006), Expanded Disability Status Scale (EDSS) score (p = 0.0079) and MS Severity Score (MSSS) (p = 0.0006).

Conclusion

In MS the level of sTREM-2 in the CSF is related to measures of T cell activation (sCD27), neuroaxonal damage (NfL and pNfH), disability (EDSS) and disease severity (MSSS).

Profiling HPV-16-specific T cell responses reveals broad antigen reactivities in oropharyngeal cancer patients

Cellular immunotherapeutics targeting the human papillomavirus (HPV)–16 E6 and E7 proteins have achieved limited success in HPV-positive oropharyngeal cancer (OPC). Here we have conducted proteome-wide profiling of HPV-16–specific T cell responses in a cohort of 66 patients with HPV-associated OPC and 22 healthy individuals. Unexpectedly, HPV-specific T cell responses from OPC patients were not constrained to the E6 and E7 antigens; they also recognized E1, E2, E4, E5, and L1 proteins as dominant targets for virus-specific CD8⁺ and CD4⁺ T cells. Multivariate analysis incorporating tumor staging, treatment status, and smoking history revealed that treatment status had the most significant impact on HPV-specific CD8⁺ and CD4⁺ T cell immunity. Specifically, the breadth and overall strength of HPV-specific T cell responses were significantly higher before the commencement of curative therapy than after therapy. These data provide the first glimpse of the overall human T cell response to HPV in a clinical setting and offer groundbreaking insight into future development of cellular immunotherapies for HPV-associated OPC patients.

Potent Activity of an Anti-ICAM1 Antibody-Drug Conjugate against Multiple Myeloma

PURPOSE

New therapies have changed the outlook for patients with multiple myeloma, but novel agents are needed for patients who are refractory or relapsed on currently approved drug classes. Novel targets other than CD38 and BCMA are needed for new immunotherapy development, as resistance to daratumumab and emerging anti-BCMA approaches appears inevitable. One potential target of interest in myeloma is ICAM1. Naked anti-ICAM1 antibodies were active in preclinical models of myeloma and safe in patients, but showed limited clinical efficacy. Here, we sought to achieve improved targeting of multiple myeloma with an anti-ICAM1 antibody-drug conjugate (ADC).

EXPERIMENTAL DESIGN

Our anti-ICAM1 human mAb was conjugated to an auristatin derivative, and tested against multiple myeloma cell lines in vitro, orthotopic xenografts in vivo, and patient samples ex vivo. The expression of ICAM1 was also measured by quantitative flow cytometry in patients spanning from diagnosis to the daratumumab-refractory state.

RESULTS

The anti-ICAM1 ADC displayed potent anti-myeloma cytotoxicity in vitro and in vivo. In addition, we have verified that ICAM1 is highly expressed on myeloma cells and shown that its expression is further accentuated by the presence of bone marrow microenvironmental factors. In primary samples, ICAM1 is differentially overexpressed on multiple myeloma cells compared with normal cells, including daratumumab-refractory patients with decreased CD38. In addition, ICAM1-ADC showed selective cytotoxicity in multiple myeloma primary samples.

CONCLUSIONS

We propose that anti-ICAM1 ADC should be further studied for toxicity, and if safe, tested for clinical efficacy in patients with relapsed or refractory multiple myeloma.

Correlation of Epstein-Barr virus-specific cytotoxic T lymphocyte precursors (EBV-CTLp) after tabelecleucel with response and survival in rituximab relapsing or refractory EBV+ post-transplant lymphoproliferative disease (PTLD)

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Background: EBV+ PTLD is often a fatal disease. Tabelecleucel is an investigational off-the-shelf, allogeneic T-cell immunotherapy specific for EBV antigens. Functional in vivo expansion approximated by a limiting dilution analysis of EBV-CTLp has previously been correlated to clinical response. Methods: We conducted analyses of reported peak circulating EBV-CTLp levels following tabelecleucel administration in correlation to response and safety across two studies (N=42) in rituximab refractory or relapsing EBV+ PTLD following HCT or SOT. Results: Two cohorts were defined by the lowest EBV-CTLp quartile (n=11) and the combined upper 3 quartiles (n=31). Twenty-five of 31 subjects (80.6%) in upper quartiles exhibited a clinical response compared to 3 of 11 subjects (27.3%) in the lowest quartile. Eighteen of 20 complete responses and 7 of 8 partial responses demonstrated peak CTLp values in the upper quartiles of the population. Overall survival (OS) rate in subjects exhibiting CTLp values in the upper quartiles was 83.9% (95% CI: 65.5-92.9%) at 1 year and 66.1% (95% CI: 45.9-80.2%) at 2 years, compared to 18.2% (95% CI: 2.9-44.2%) in the lowest quartile over the same periods. OS is commensurate with a hazard ratio of 0.168 in favor of subjects with higher EBV-CTLp (95% CI: 0.067-0.425; Log-Rank Test p-value <0.001). Subjects demonstrating clinical responses experienced median CTLp values of 36.2 CTLp/ml (15.6-155 interquartile range), whereas non-responders exhibited significantly lower (p=0.001, based on Wilcoxon Rank Sum test) median CTLp of 0.07/ml (0.01-5.5 interquartile range). Tabelecleucel was well tolerated across both studies, with a safety profile in each group consistent with the underlying clinical condition of patients. Conclusions: These analyses illustrate the correlation of peak EBV-CTLp to clinical benefit in subjects receiving tabelecleucel. Significant correlation of EBV-CTLp with ORR and OS are consistent with potential use as a functional biomarker for the expansion of EBV-specific T-cells in the treatment of EBV+ PTLD in the rituximab refractory/relapsing setting. Clinical trial information: NCT01498484.

Proteome-wide analysis of T-cell response to BK polyomavirus in healthy virus carriers and kidney transplant recipients reveals a unique transcriptional and functional profile

Objectives

Cellular immunity against BK polyomavirus (BKV)‐encoded antigens plays a crucial role in long‐term protection against virus‐associated pathogenesis in transplant recipients. However, in‐depth understanding on dynamics of these cellular immune responses is required to develop better immune monitoring and immunotherapeutic strategies.

Methods

Here, we have conducted a proteome‐wide analysis of BKV‐specific T‐cell responses in a cohort of 53 healthy individuals and 26 kidney transplant recipients to delineate the functional and transcriptional profile of these effector cells and compared these characteristics to T cells directed against cytomegalovirus, which is also known to cause significant morbidity in transplant recipients.

Results

Profiling of BKV‐specific CD4⁺ and CD8⁺ T cells revealed that kidney transplant recipients with high levels of circulating viraemia showed significantly reduced T‐cell reactivity against large T and/or small T antigens when compared to healthy donors. Interestingly, T cells specific for these antigens showed strong cross‐recognition to orthologous JC virus (JCV) peptides, including those exhibiting varying degrees of sequence identity. Ex vivo functional and phenotypic characterisation revealed that the majority of BKV‐specific T cells from renal transplant recipients expressed low levels of the key transcriptional regulators T‐bet and eomesodermin, which was coincident with undetectable expression of granzyme B and perforin. However, in vitro stimulation of T cells with BKV epitopes selectively enhanced the expression of T‐bet, granzyme B and cellular trafficking molecules (CCR4, CD49d and CD103) with minimal change in eomesodermin and perforin.

Conclusions

These observations provide an important platform for the future development of immune monitoring and adoptive T‐cell therapy strategies for BKV‐associated diseases in transplant recipients, which may also be exploited for similar therapeutic value in JCV‐associated clinical complications.

Epstein-Barr Virus in Multiple Sclerosis: Theory and Emerging Immunotherapies

New treatments for multiple sclerosis (MS) focused on B cells have created an atmosphere of excitement in the MS community. B cells are now known to play a major role in disease, demonstrated by the highly impactful effect of a B cell-depleting antibody on controlling MS. The idea that a virus may play a role in the development of MS has a long history and is supported mostly by studies demonstrating a link between B cell-tropic Epstein–Barr virus (EBV) and disease onset. Efforts to develop antiviral strategies for treating MS are underway. Although gaps remain in our understanding of the etiology of MS, the role, if any, of viruses in propagating pathogenic immune responses deserves attention.

Abstract 2310: Functional demonstration of CD19 chimeric antigen receptor (CAR) engineered Epstein-Barr virus (EBV) specific T cells: An off-the-shelf, allogeneic CAR T-cell immunotherapy platform

Chimeric antigen receptor (CAR) T cells have transformed the treatment of advanced B cell malignancies, but broad application has been limited due to technical and operational challenges in the autologous approach. Virus-specific T cells maintain native T cell receptors and have an established clinical profile and potential utility as an off-the-shelf, allogeneic CAR T-cell immunotherapy platform.

Tabelecleucel (tab-cel®) is an investigational off-the-shelf, allogeneic T-cell immunotherapy that utilizes endogenous T cell receptors targeting EBV antigens associated with select lymphomas and solid tumors. Tab-cel® functions through endogenous TCRs restricted to EBV antigens and has been shown to be generally well tolerated with low incidence of GvHD and cytokine release syndrome, as well as efficacy in EBV+ post-transplant lymphoproliferative disorders (PTLD). Introduction of CAR transgenes into EBV-specific T cells provides an appealing approach for developing off-the-shelf, allogeneic CAR T immunotherapies.

To evaluate feasibility for this platform, we engineered EBV-specific T cells to express second-generation CD19 CARs, utilizing CD28 or 4-1BB co-stimulatory domains. Resulting allo-EBV.CD19.CAR T cells exhibit high expression of both the CD19 CAR and EBV TCR. Additionally, allo-EBV.CD19.CAR T cells demonstrate an enriched central memory phenotype with higher frequency expression of CD62L, CCR7, and CD45RO. Allo-EBV.CD19.CAR T cells also show increased frequency of activation markers CD25 and 4-1BB, and produce activation-associated levels of IFN-γ comparable to EBV-specific T cells. Allo-EBV.CD19.CAR T cells exert potent and specific cytotoxicity against CD19-positive Nalm6 and Raji cells but have limited activity against CD19-negative K562 cells. Both CD19.CAR T and allo-EBV.CD19.CAR T-mediated cytotoxicity displayed rapid and comparable kinetics. Stimulation of allo-EBV.CD19.CAR T cells with either EBV- or CD19-positive targets also induced robust proliferation over several days of antigen challenge. Like unmodified EBV-specific T cells, allo-EBV.CD19.CAR T cells retain the ability to kill B-lymphoblastoid cell lines (BLCL) but spare autologous and allogeneic PHA-blast targets lacking CD19 and EBV antigen expression. This specificity in cytotoxicity is further supported by inflammatory cytokine profiles of effector-target cultures.

From these results, allo-EBV.CD19.CAR T cells demonstrate efficient and effective lysis of antigen-positive target cells, while maintaining low allo-cytotoxic potential. These findings establish feasibility for engineering EBV-specific T cells by leveraging next-generation CAR technologies, and support further development as an off-the-shelf, allogeneic CAR-T immunotherapy platform to generate IND clinical candidates.

Citation Format: Rhine R. Shen, Christina D. Pham, Michelle Min Wu, Daniel J. Munson, Blake T. Aftab. Functional demonstration of CD19 chimeric antigen receptor (CAR) engineered Epstein-Barr virus (EBV) specific T cells: An off-the-shelf, allogeneic CAR T-cell immunotherapy platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2310.

Correlation of circulating EBV-targeted cytotoxic T lymphocyte precursors (EBV-CTLp) and clinical response following tabelecleucel (tab-cel) infusion in patients with EBV-driven disease

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Background: EBV is implicated in a variety of diseases. Tab-cel is an investigational off-the-shelf, allogeneic T-cell immunotherapy utilizing endogenous T cell receptors targeting EBV antigens. We hypothesized the clinical activity of tab-cel is mediated by expansion and persistence of EBV-specific T cells. Therefore, we quantified circulating EBV- CTLp after tab-cel administration and examined the correlation between expansion and clinical response. Methods: Samples from 10 patients with EBV+ post-transplant lymphoproliferative disease (PTLD) and other EBV-associated diseases enrolled in an multicenter expanded access protocol (EAP) study ( NCT02822495 ) were analyzed. To evaluate CTLp frequencies, limited dilution analysis was performed on samples taken at baseline and day 34 post first tab-cel dose (end cycle 1). The day 34 persistence of circulating EBV-CTLp from best overall response to initial tab-cel product was tested using the two-tailed Mann-Whitney test. Changes in inflammatory cytokines were also measured. Results: Responders represented in this sampling (n=6; 2 PR and 4 CR) showed a median 5.8-fold increase in circulating CTLp between baseline and day 34 (range: 0.8 to 133-fold). Five of 6 responders showed an increase in EBV-CTLp at day 34 of ≥ 3.8-fold while 1 pt showed no change in CTLp (0.8-fold change). In contrast, the 4 non-responders (3 SD; 1 PD) showed a median 0.3-fold decrease in EBV-CTLp from baseline (range: 1.2 to 0.02-fold; ns). Cumulative analyses revealed a statistically significant correlation between the fold-change of circulating CTLp at day 34 and clinical response (p=0.038) which did not appear to correlate with the type of the EBV-associated disease. Inflammatory cytokines showed no meaningful change from baseline. The safety profile remains consistent with previously reported data. Conclusions: These data support the correlation of clinical activity of tab-cel with the expansion and persistence of EBV-specific T-cells at day 34 post-treatment, as well as the use of circulating CTLp as a biomarker for response in clinical studies. Clinical trial information: NCT02822495.

Epstein-Barr virus-specific T cell therapy for progressive multiple sclerosis

BACKGROUND

Increasing evidence indicates a role for EBV in the pathogenesis of multiple sclerosis (MS). EBV-infected autoreactive B cells might accumulate in the CNS because of defective cytotoxic CD8+ T cell immunity. We sought to determine the feasibility and safety of treating progressive MS patients with autologous EBV-specific T cell therapy.

METHODS

An open-label phase I trial was designed to treat 5 patients with secondary progressive MS and 5 patients with primary progressive MS with 4 escalating doses of in vitro-expanded autologous EBV-specific T cells targeting EBV nuclear antigen 1, latent membrane protein 1 (LMP1), and LMP2A. Following adoptive immunotherapy, we monitored the patients for safety and clinical responses.

RESULTS

Of the 13 recruited participants, 10 received the full course of T cell therapy. There were no serious adverse events. Seven patients showed improvement, with 6 experiencing both symptomatic and objective neurological improvement, together with a reduction in fatigue, improved quality of life, and, in 3 patients, reduced intrathecal IgG production. All 6 patients receiving T cells with strong EBV reactivity showed clinical improvement, whereas only 1 of the 4 patients receiving T cells with weak EBV reactivity showed improvement (P = 0.033, Fisher's exact test).

CONCLUSION

EBV-specific adoptive T cell therapy was well tolerated. Clinical improvement following treatment was associated with the potency of EBV-specific reactivity of the administered T cells. Further clinical trials are warranted to determine the efficacy of EBV-specific T cell therapy in MS.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12615000422527.

FUNDING

MS Queensland, MS Research Australia, Perpetual Trustee Company Ltd., and donations from private individuals who wish to remain anonymous.

Molecular signature of Epstein-Barr virus infection in MS brain lesions

Objective

We sought to confirm the presence and frequency of B cells and Epstein-Barr virus (EBV) (latent and lytic phase) antigens in archived MS and non-MS brain tissue by immunohistochemistry.

Methods

We quantified the type and location of B-cell subsets within active and chronic MS brain lesions in relation to viral antigen expression. The presence of EBV-infected cells was further confirmed by in situ hybridization to detect the EBV RNA transcript, EBV-encoded RNA-1 (EBER-1).

Results

We report the presence of EBV latent membrane protein 1 (LMP-1) in 93% of MS and 78% of control brains, with a greater percentage of MS brains containing CD138⁺ plasma cells and LMP-1–rich populations. Notably, 78% of chronic MS lesions and 33.3% of non-MS brains contained parenchymal CD138⁺ plasma cells. EBV early lytic protein, EBV immediate-early lytic gene (BZLF1), was also observed in 46% of MS, primarily in association with chronic lesions and 44% of non-MS brain tissue. Furthermore, 85% of MS brains revealed frequent EBER-positive cells, whereas non-MS brains seldom contained EBER-positive cells. EBV infection was detectable, by immunohistochemistry and by in situ hybridization, in both MS and non-MS brains, although latent virus was more prevalent in MS brains, while lytic virus was restricted to chronic MS lesions.

Conclusions

Together, our observations suggest an uncharacterized link between the EBV virus life cycle and MS pathogenesis.

Repurposing tofacitinib as an anti-myeloma therapeutic to reverse growth-promoting effects of the bone marrow microenvironment

The myeloma bone marrow microenvironment promotes proliferation of malignant plasma cells and resistance to therapy. Activation of JAK/STAT signaling is thought to be a central component of these microenvironment-induced phenotypes. In a prior drug repurposing screen, we identified tofacitinib, a pan-JAK inhibitor Food and Drug Administration (FDA) approved for rheumatoid arthritis, as an agent that may reverse the tumor-stimulating effects of bone marrow mesenchymal stromal cells. Herein, we validated in vitro, in stromal-responsive human myeloma cell lines, and in vivo, in orthotopic disseminated xenograft models of myeloma, that tofacitinib showed efficacy in myeloma models. Furthermore, tofacitinib strongly synergized with venetoclax in coculture with bone marrow stromal cells but not in monoculture. Surprisingly, we found that ruxolitinib, an FDA approved agent targeting JAK1 and JAK2, did not lead to the same anti-myeloma effects. Combination with a novel irreversible JAK3-selective inhibitor also did not enhance ruxolitinib effects. Transcriptome analysis and unbiased phosphoproteomics revealed that bone marrow stromal cells stimulate a JAK/STAT-mediated proliferative program in myeloma cells, and tofacitinib reversed the large majority of these pro-growth signals. Taken together, our results suggest that tofacitinib reverses the growth-promoting effects of the tumor microenvironment. As tofacitinib is already FDA approved, these results can be rapidly translated into potential clinical benefits for myeloma patients.

The p97 Inhibitor CB-5083 Is a Unique Disrupter of Protein Homeostasis in Models of Multiple Myeloma

Inhibition of the AAA ATPase, p97, was recently shown to be a novel method for targeting the ubiquitin proteasome system, and CB-5083, a first-in-class inhibitor of p97, has demonstrated broad antitumor activity in a range of both hematologic and solid tumor models. Here, we show that CB-5083 has robust activity against multiple myeloma cell lines and a number of in vivo multiple myeloma models. Treatment with CB-5083 is associated with accumulation of ubiquitinated proteins, induction of the unfolded protein response, and apoptosis. CB-5083 decreases viability in multiple myeloma cell lines and patient-derived multiple myeloma cells, including those with background proteasome inhibitor (PI) resistance. CB-5083 has a unique mechanism of action that combines well with PIs, which is likely owing to the p97-dependent retro-translocation of the transcription factor, Nrf1, which transcribes proteasome subunit genes following exposure to a PI. In vivo studies using clinically relevant multiple myeloma models demonstrate that single-agent CB-5083 inhibits tumor growth and combines well with multiple myeloma standard-of-care agents. Our preclinical data demonstrate the efficacy of CB-5083 in several multiple myeloma disease models and provide the rationale for clinical evaluation as monotherapy and in combination in multiple myeloma. Mol Cancer Ther; 16(11); 2375-86. ©2017 AACR.

Antibody-drug conjugate targeting CD46 eliminates multiple myeloma cells

Multiple myeloma is incurable by standard approaches because of inevitable relapse and development of treatment resistance in all patients. In our prior work, we identified a panel of macropinocytosing human monoclonal antibodies against CD46, a negative regulator of the innate immune system, and constructed antibody-drug conjugates (ADCs). In this report, we show that an anti-CD46 ADC (CD46-ADC) potently inhibited proliferation in myeloma cell lines with little effect on normal cells. CD46-ADC also potently eliminated myeloma growth in orthometastatic xenograft models. In primary myeloma cells derived from bone marrow aspirates, CD46-ADC induced apoptosis and cell death, but did not affect the viability of nontumor mononuclear cells. It is of clinical interest that the CD46 gene resides on chromosome 1q, which undergoes genomic amplification in the majority of relapsed myeloma patients. We found that the cell surface expression level of CD46 was markedly higher in patient myeloma cells with 1q gain than in those with normal 1q copy number. Thus, genomic amplification of CD46 may serve as a surrogate for target amplification that could allow patient stratification for tailored CD46-targeted therapy. Overall, these findings indicate that CD46 is a promising target for antibody-based treatment of multiple myeloma, especially in patients with gain of chromosome 1q.

Abstract A2-57: Identification of genetic vulnerabilities within the proteostasis network of multiple myeloma

Multiple myeloma (MM) remains an incurable disease afflicting more than 20,000 patients yearly in the US alone. Because of their secretory nature, MM cells rely on the proteostasis network and re-wire it to their advantage. We focused on two interconnected essential pathways within the proteostasis network to query genetic vulnerabilities yielding synthetic lethality. These pathways are the ubiquitin-proteasome system (UPS) and the unfolded protein response (UPR). Standard-of-care proteasome inhibitors, like bortezomib, remain non-curative in MM patients, suggesting the selection of genetic escape routes. The same rationale is applicable to the UPR, a conserved regulatory network overseeing the processing capacity of the endoplasmic reticulum (ER). Since proteasomal degradation of unfolded ER client proteins is accomplished after their dislocation and ubiquitination, we reasoned that common genetic escape routes might exist within the UPS and the UPR. Because single agents provide the driving force for acquired drug resistance and do not lead to long-term remission, we employed a systems-level shRNA screening method that systematically identified synthetic-lethal interactions that can enhance the therapeutic benefit of proteasome inhibition or modulation of the UPR. In the latter, we focused on the UPR branch overseen by the sensor kinase/nuclease IRE1 because it is thought to confer a survival advantage to MM. Applying chemical-genetics approaches using bortezomib or novel chemical inhibitors of IRE1, and an ultra-complex shRNA library we developed, we performed pooled shRNA screens in RPMI-8226 and MM1-S MM cells and identified genes whose diminished function impact the response to proteasome or IRE1 inhibition. Unlike proteasome inhibition, blocking IRE1 did not lead to considerable MM cell death, suggesting that IRE1 alone is not a fate determinant but a weakness that can be exploited through the identification of synthetic-lethal combinations. We applied the same rationale to proteasome inhibition and found synthetic-lethal pairs. Because some of these genes can be targeted pharmacologically, we explored the susceptibility of a panel of MM cells to combinations of bortezomib and drug-like molecules, including novel Hsp70 inhibitors. Retrospective analyses on publicly available gene expression datasets of MM patients treated with bortezomib indicated that several of the genes we found in our screen also predicted clinical outcomes. Together, our preliminary results indicate our approach is a powerful tool for the discovery of synthetic-lethal pairs that can be exploited in combination therapies.

Citation Format: Diego Acosta-Alvear, Martin Kampmann, Min Y. Cho, Blake T. Aftab, Xiaokai Li, Jason E. Gestwicki, Marc A. Shuman, Jonathan S. Weissman, Peter Walter. Identification of genetic vulnerabilities within the proteostasis network of multiple myeloma. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr A2-57.

Targeting the AAA ATPase p97 as an Approach to Treat Cancer through Disruption of Protein Homeostasis

p97 is a AAA-ATPase with multiple cellular functions, one of which is critical regulation of protein homeostasis pathways. We describe the characterization of CB-5083, a potent, selective, and orally bioavailable inhibitor of p97. Treatment of tumor cells with CB-5083 leads to accumulation of poly-ubiquitinated proteins, retention of endoplasmic reticulum-associated degradation (ERAD) substrates, and generation of irresolvable proteotoxic stress, leading to activation of the apoptotic arm of the unfolded protein response. In xenograft models, CB-5083 causes modulation of key p97-related pathways, induces apoptosis, and has antitumor activity in a broad range of both hematological and solid tumor models. Molecular determinants of CB-5083 activity include expression of genes in the ERAD pathway, providing a potential strategy for patient selection.

Validation of the Hsp70-Bag3 protein-protein interaction as a potential therapeutic target in cancer

Hsp70 is a stress-inducible molecular chaperone that is required for cancer development at several steps. Targeting the active site of Hsp70 has proven relatively challenging, driving interest in alternative approaches. Hsp70 collaborates with the Bcl2-associated athanogene 3 (Bag3) to promote cell survival through multiple pathways, including FoxM1. Therefore, inhibitors of the Hsp70-Bag3 protein-protein interaction (PPI) may provide a noncanonical way to target this chaperone. We report that JG-98, an allosteric inhibitor of this PPI, indeed has antiproliferative activity (EC50 values between 0.3 and 4 μmol/L) across cancer cell lines from multiple origins. JG-98 destabilized FoxM1 and relieved suppression of downstream effectors, including p21 and p27. On the basis of these findings, JG-98 was evaluated in mice for pharmacokinetics, tolerability, and activity in two xenograft models. The results suggested that the Hsp70-Bag3 interaction may be a promising, new target for anticancer therapy.

Abstract PR07: Systematic genetic interaction maps reveal rewiring of the stress response network and resulting vulnerabilities in leukemia and multiple myeloma cells

Systematic, high-density mapping of genetic interactions is a powerful approach to elucidate functional pathways and reveal synthetic lethal gene pairs, and has successfully been applied in microorganisms. We have recently developed a functional genomics platform that enables the construction of high-density genetic interaction maps in mammalian cells. In a first step, we conduct pooled primary screens using an ultracomplex shRNA library that targets each protein-coding gene with 25 independent shRNAs and contains &gt;1,000 negative control shRNAs. This strategy enables us to robustly identify hit genes and shRNAs that target them effectively, while minimizing the identification of false-positive hits, which has plagued many genome-wide RNAi screens. In a second step, we construct and screen a double-shRNA library targeting all pairwise combinations of hit genes of interest to construct a high-density genetic interaction map. Thus, our approach enables us to determine 100,000s of genetic interactions in a single experiment.

Here, we present the application of our platform to identify adaptations and vulnerabilities in the stress response network of leukemia and multiple myeloma cells. Stress response pathways, including the unfolded protein response, starvation, hypoxia and oxidative stress responses, and the associated induction of autophagy, play important roles in cancer cell survival, drug resistance and tumor progression. The goal of the research presented here is to systematically characterize vulnerabilities in the stress response network of cancer cells, and in particular, to identify synthetic-lethal vulnerabilities that are potential new targets for combination drug therapy.

We conducted our first experiments in two human cell lines derived from hematologic malignancies, K562 (leukemia) and RPMI-8226 (multiple myeloma), for which we determined genetic vulnerabilities and their genetic interactions in the absence and presence of stress-inducing agents. We discovered several genetic vulnerabilities that can be targeted pharmacologically. An important class of factors we detected as vulnerabilities in our screens are Hsp70 proteins, which are commonly upregulated under stress conditions and in cancer cells. We have recently synthesized a series of small-molecule Hsp70 inhibitors, which we have successfully used to selectively kill cancer cells. Using a chemical-genetics approach, we have probed the genetic factors affecting the sensitivity of cancer cells to two of these inhibitors with selectivity for Hsp70 proteins in different subcellular compartments.

We externally validated several of the synthetic-lethal vulnerabilities identified in our screens by demonstrating synergistic effects of drug combinations targeting these gene pairs in panels of cancer cell lines. Comparison of drug sensitivities across our cell line panel, in conjunction with our experimentally derived set of genetic vulnerabilities, has generated testable hypotheses for the role of the genetic background in determining vulnerabilities related to the stress response network. Intriguingly, expression levels of several genes we identified as vulnerabilities in multiple myeloma cells are prognostic of patient survival in a published multiple myeloma clinical trial.

This abstract is also presented as poster B25.

Citation Format: Martin Kampmann, Diego Acosta-Alvear, Min Cho, Yuwen Chen, Xiaokai Li, Luke Gilbert, Blake T. Aftab, Jason Gestwicki, Peter Walter, Jonathan S. Weissman. Systematic genetic interaction maps reveal rewiring of the stress response network and resulting vulnerabilities in leukemia and multiple myeloma cells. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr PR07.

Abstract C01: Systematic blueprinting of genetic vulnerabilities using ultra-complex shRNA libraries identifies genes synergizing with proteasome inhibition or blockade of IRE1 in multiple myeloma cells

Multiple myeloma (MM) remains a devastating incurable disease. Because of their secretory nature, MM cells rely on proper endoplasmic reticulum (ER) function. The unfolded protein response (UPR) oversees the folding capacity of the ER and adjusts it according to need. Paraprotein production by MM cells imposes an ER burden that provides an opportunity for therapeutic intervention. High ER function exceeds the buffering capacity of the cell for protein degradation, rendering MM cells exquisitely sensitive to proteasome inhibitors. While successful, standard-of-care proteasome inhibitors, like bortezomib, remain palliative, as patients ultimately become refractory, suggesting the selection of genetic escape routes. ER and proteasome functions are intimately connected. Proteasomal degradation of unfolded ER client proteins is accomplished after dislocation and ubiquitination of unfolded proteins from the ER. Therefore, genetic escape routes can exist within the ubiquitin-proteasome system and the UPR. The most conserved branch of the UPR, overseen by the sensor kinase IRE1 and its downstream effector, XBP1, has been a primary focus of the MM research community in recent years. In healthy cells IRE1/XBP1 allow adaptation to rises in ER function, while in MM cells IRE1/XBP1 are thought to confer a survival advantage.

For these reasons, we hypothesized that modulation of the UPR, alone or in combination with proteasome inhibitors, while therapeutically beneficial, might also provide the driving force for acquired drug resistance. Therefore, a single agent is unlikely to lead to long-term remission. Here we show that the therapeutic benefit of blocking the proteasome or IRE1 in MM cells can be enhanced when combined with additional therapies targeting synthetic-lethal interactions, and that these can be systematically identified using an shRNA screening method developed by our groups. Employing an ultra-complex shRNA library, we performed pooled shRNA screens in RPMI-8226 and MM1-S MM cells and identified genes whose diminished function impact the cell's response to proteasome or IRE1 inhibition. Importantly, we show that unlike proteasome inhibition, blocking IRE1 function does not lead to substantial MM cell death, strongly suggesting that IRE1 alone is not a fate determinant. Instead, we posit IRE1 is a handicap that might be therapeutically exploited through the identification of synthetic-lethal combinations. We applied the same rationale to proteasome inhibition and found several synthetic-lethal pairs. Some of these genes can be targeted pharmacologically, which allowed us to query the susceptibility of a panel of MM cells to combinations of bortezomib and several drug-like molecules, including novel Hsp70 inhibitors. Our results inform which pathways may be selectively blocked to shut down potential escape routes that may lead to drug resistance. Notably, retrospective analyses on publicly available gene expression datasets of MM patients indicate that several of the genes we found on our screens are predictors of poor survival. Taken together, our preliminary results indicate our screening platform is a powerful tool for the discovery of (i) novel therapy targets, (ii) synthetic-lethal pairs that can be exploited in potential combination therapies, and (iii) diagnostics biomarkers. Currently, we continue to validate our results in additional cell lines prior to verification in primary patient samples and in an orthotopic xenograft model developed by our groups (DAA and PW, unpublished).

Citation Format: Diego Acosta-Alvear, Martin Kampmann, Michael C. Bassik, Crystal P. Lee, Min Y. Cho, Blake T. Aftab, Xiaokai Li, Jason E. Gestwicki, Marc A. Shuman, Jonathan S. Weissman, Peter Walter. Systematic blueprinting of genetic vulnerabilities using ultra-complex shRNA libraries identifies genes synergizing with proteasome inhibition or blockade of IRE1 in multiple myeloma cells. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C01.

Abstract 5469: SAR650984, an anti-CD38 antibody, shows anti-tumor activity in a preclinical model of multiple myeloma

Multiple myeloma (MM) is the second most common cancer of the blood and one that is difficult to treat. Although survival has greatly improved over the past decade, MM remains fatal, necessitating development of novel therapies. CD38 is a promising target for antibody therapeutics for the treatment MM and various other hematological malignancies. CD38 is a type II transmembrane glycoprotein with ectozyme activity that has been implicated in Ca2+ mobilization and is found highly expressed on malignant plasma cells of MM. CD38 expression correlates with poor disease prognosis in a subset of hematological malignancies, including MM, where CD38 expression in circulating cells is associated with decreased progression free survival. Previous studies have identified several potential mechanisms of action in the context of anti-myeloma activity, including antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and pro-apoptotic activity in cancer cell lines.

To determine the potential therapeutic value of targeting CD38 in the context of MM, a humanized anti-CD38 antibody, SAR650984, was generated and evaluated for anti-tumor activity. We evaluated anti-tumor activity of SAR650984 in xenograft-based models of multiple myeloma . SAR650984 demonstrated potent anti-tumor activity in NCI-H929 and RPMI-8226 MM xenograft models.

These results strongly support continued clinical examination of the therapeutic potential for SAR650984 in the treatment of MM and further demonstrates that targeting CD38 with SAR650984 has potential to impact MM disease.

Citation Format: Byron Hann, Ti Cai, Donghui Wang, Yun-Kit Hom, Blake T. Aftab, Tom Martin, Jeffrey Wolf. SAR650984, an anti-CD38 antibody, shows anti-tumor activity in a preclinical model of multiple myeloma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5469. doi:10.1158/1538-7445.AM2013-5469

Itraconazole and arsenic trioxide inhibit Hedgehog pathway activation and tumor growth associated with acquired resistance to smoothened antagonists

Recognition of the multiple roles of Hedgehog signaling in cancer has prompted intensive efforts to develop targeted pathway inhibitors. Leading inhibitors in clinical development act by binding to a common site within Smoothened, a critical pathway component. Acquired Smoothened mutations, including SMO(D477G), confer resistance to these inhibitors. Here, we report that itraconazole and arsenic trioxide, two agents in clinical use that inhibit Hedgehog signaling by mechanisms distinct from that of current Smoothened antagonists, retain inhibitory activity in vitro in the context of all reported resistance-conferring Smoothened mutants and GLI2 overexpression. Itraconazole and arsenic trioxide, alone or in combination, inhibit the growth of medulloblastoma and basal cell carcinoma in vivo, and prolong survival of mice with intracranial drug-resistant SMO(D477G) medulloblastoma.

Hedgehog pathway inhibition radiosensitizes non-small cell lung cancers

PURPOSE

Despite improvements in chemoradiation, local control remains a major clinical problem in locally advanced non-small cell lung cancer. The Hedgehog pathway has been implicated in tumor recurrence by promoting survival of tumorigenic precursors and through effects on tumor-associated stroma. Whether Hedgehog inhibition can affect radiation efficacy in vivo has not been reported.

METHODS AND MATERIALS

We evaluated the effects of a targeted Hedgehog inhibitor (HhAntag) and radiation on clonogenic survival of human non-small cell lung cancer lines in vitro. Using an A549 cell line xenograft model, we examined tumor growth, proliferation, apoptosis, and gene expression changes after concomitant HhAntag and radiation. In a transgenic mouse model of Kras(G12D)-induced and Twist1-induced lung adenocarcinoma, we assessed tumor response to radiation and HhAntag by serial micro-computed tomography (CT) scanning.

RESULTS

In 4 human lung cancer lines in vitro, HhAntag showed little or no effect on radiosensitivity. By contrast, in both the human tumor xenograft and murine inducible transgenic models, HhAntag enhanced radiation efficacy and delayed tumor growth. By use of the human xenograft model to differentiate tumor and stromal effects, mouse stromal cells, but not human tumor cells, showed significant and consistent downregulation of Hedgehog pathway gene expression. This was associated with increased tumor cell apoptosis.

CONCLUSIONS

Targeted Hedgehog pathway inhibition can increase in vivo radiation efficacy in lung cancer preclinical models. This effect is associated with pathway suppression in tumor-associated stroma. These data support clinical testing of Hedgehog inhibitors as a component of multimodality therapy for locally advanced non-small cell lung cancer.

Bridging the gap between preclinical and clinical studies using pharmacokinetic-pharmacodynamic modeling: an analysis of GDC-0973, a MEK inhibitor

PURPOSE

GDC-0973 is a potent and selective mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor. Pharmacokinetic-pharmacodynamic (PK-PD) modeling was used to relate GDC-0973 plasma and tumor concentrations, tumor pharmacodynamics and antitumor efficacy to establish pharmacokinetic endpoints and predict active doses in the clinic.

EXPERIMENTAL DESIGN

A PK-PD model was used to characterize GDC-0973 tumor disposition and in vivo potency in WM-266-4 xenograft mice. Simulations were conducted using the PK-PD model along with human pharmacokinetics to identify a target plasma concentration and predict active doses. In vivo potency and antitumor efficacy were characterized in A375 melanoma xenograft mice, and a population-based integrated PK-PD-efficacy model was used to relate tumor pharmacodynamics (%pERK decrease) to antitumor activity.

RESULTS

GDC-0973 showed a sustained tumor pharmacodynamic response due to longer residence in tumor than in plasma. Following single doses of GDC-0973, estimated in vivo IC(50) values of %pERK decrease based on tumor concentrations in xenograft mice were 0.78 (WM-266-4) and 0.52 μmol/L (A375). Following multiple doses of GDC-0973, the estimated in vivo IC(50) value in WM-266-4 increased (3.89 μmol/L). Human simulations predicted a minimum target plasma concentration of 83 nmol/L and an active dose range of 28 to 112 mg. The steep relationship between tumor pharmacodynamics (%pERK decrease) and antitumor efficacy suggests a pathway modulation threshold beyond which antitumor efficacy switches on.

CONCLUSIONS

Clinical observations of %pERK decrease and antitumor activity were consistent with model predictions. This article illustrates how PK-PD modeling can improve the translation of preclinical data to humans by providing a means to integrate preclinical and early clinical data.

Abstract C147: Itraconazole side-chain analogs reveal a distinct structure-activity relationship for inhibition of hedgehog pathway signaling

Itraconazole is an antifungal drug that was recently found to potently inhibit the Hedgehog (Hh) signaling pathway. The mechanism of inhibition of Hh signaling is distinct from that of cyclopamine-competitive inhibitors currently in late-stage clinical development. Itraconazole has also been described as a potent inhibitor of activation of vascular endothelial growth factor receptor-2 (VEGFR-2) and tumor associated angiogenesis. The unexpected activities associated with this FDA-approved agent offer a unique opportunity for expansion of its use to the oncology arena. As such, itraconazole is currently being evaluated in several clinical trials targeting proliferative disease, including basal cell carcinoma and recurrent metastatic non-small cell lung cancer. To date, the target(s) of itraconazole responsible for these activities remain to be determined. In these studies we expand the characterization of the activity profile for itraconazole by examining potency in the context of a Smoothened receptor point-mutation associated with clinical resistance to vismodegib (GDC-0449). Additionally, in the interest of understanding the structure-activity relationship (SAR) guiding Hh pathway targeting and working towards the identification and development of inhibitors demonstrating greater potency and specificity; twenty-five itraconazole side chain analogs were synthesized and assayed for inhibition of Hh pathway activation. Furthermore, the SAR associated with the inhibition of phospho-activatable forms of VEGFR2 is also described. Through these analyses we report that itraconazole maintains potency against the Hh pathway in the context of the D477G Smoothened mutation (mouse homologue to human D473H). We also conclude that SAR trends for targeting of the Hh pathway are divergent from those associated with inhibition of VEGFR2 signaling. Taken together, these results suggest that modification of the sec-butyl side chain of itraconazole can enhance compound activity and differentially affects inhibition of the Hh pathway and VEGFR2 signaling.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C147.

Itraconazole inhibits angiogenesis and tumor growth in non-small cell lung cancer

The antiangiogenic agent bevacizumab has been approved for the treatment of non-small cell lung cancer (NSCLC), although the survival benefit associated with this agent is marginal, and toxicities and cost are substantial. A recent screen for selective inhibitors of endothelial cell proliferation identified the oral antifungal drug itraconazole as a novel agent with potential antiangiogenic activity. In this article, we define and characterize the antiangiogenic and anticancer activities of itraconazole in relevant preclinical models of angiogenesis and lung cancer. Itraconazole consistently showed potent, specific, and dose-dependent inhibition of endothelial cell proliferation, migration, and tube formation in response to both VEGF- and basic fibroblast growth factor-mediated angiogenic stimulation. In vivo, using primary xenograft models of human NSCLC, oral itraconazole showed single-agent growth-inhibitory activity associated with induction of tumor hypoxia-inducible factor 1 alpha expression and marked inhibition of tumor vascularity. Itraconazole significantly enhanced the antitumor efficacy of the chemotherapeutic agent cisplatin in the same model systems. Taken together, these data suggest that itraconazole has potent and selective inhibitory activity against multiple key aspects of tumor-associated angiogenesis in vitro and in vivo, and strongly support clinical translation of its use. Based on these observations, we have initiated a randomized phase II study comparing the efficacy of standard cytotoxic therapy with or without daily oral itraconazole in patients with recurrent metastatic NSCLC.

A polymeric nanoparticle encapsulated small-molecule inhibitor of Hedgehog signaling (NanoHHI) bypasses secondary mutational resistance to Smoothened antagonists

Aberrant activation of the hedgehog (Hh) signaling pathway is one of the most prevalent abnormalities in human cancer. Tumors with cell autonomous Hh activation (e.g., medulloblastomas) can acquire secondary mutations at the Smoothened (Smo) antagonist binding pocket, which render them refractory to conventional Hh inhibitors. A class of Hh pathway inhibitors (HPI) has been identified that block signaling downstream of Smo; one of these compounds, HPI-1, is a potent antagonist of the Hh transcription factor Gli1 and functions independent of upstream components in the pathway. Systemic administration of HPI-1 is challenging due to its minimal aqueous solubility and poor bioavailability. We engineered a polymeric nanoparticle from [poly(lactic-co-glycolic acid); (PLGA)] conjugated with polyethylene glycol (PEG), encapsulating HPI-1 (NanoHHI). NanoHHI particles have an average diameter of approximately 60 nm, forms uniform aqueous suspension, and improved systemic bioavailability compared with the parent compound. In contrast to the prototype targeted Smo antagonist, HhAntag (Genentech), NanoHHI markedly inhibits the growth of allografts derived from Ptch(-/+); Trp53(-/-) mouse medulloblastomas that harbor a Smo(D477G) binding site mutation (P < 0.001), which is accompanied by significant downregulation of mGli1 as well as bona fide Hh target genes (Akna, Cltb, and Olig2). Notably, NanoHHI combined with gemcitabine also significantly impedes the growth of orthotopic Pa03C pancreatic cancer xenografts that have a ligand-dependent, paracrine mechanism of Hh activation when compared with gemcitabine alone. No demonstrable hematologic or biochemical abnormalities were observed with NanoHHI administration. NanoHHI should be amenable to clinical translation in settings where tumors acquire mutational resistance to current Smo antagonists.

Itraconazole side chain analogues: structure-activity relationship studies for inhibition of endothelial cell proliferation, vascular endothelial growth factor receptor 2 (VEGFR2) glycosylation, and hedgehog signaling

Itraconazole is an antifungal drug that was recently found to possess potent antiangiogenic activity and anti-hedgehog (Hh) pathway activity. To search for analogues of itraconazole with greater potency and to understand the structure-activity relationship in both antiangiogenic and Hh targeting activity, 25 itraconazole side chain analogues were synthesized and assayed for inhibition of endothelial cell proliferation and Gli1 transcription in a medulloblastoma (MB) culture. Through this analysis, we have identified analogues with increased potency for inhibiting endothelial cell proliferation and the Hh pathway, as well as VEGFR2 glycosylation that was recently found to be inhibited by itraconazole. An SAR analysis of these activities revealed that potent activity of the analogues against VEGFR2 glycosylation was generally driven by side chains of at least four carbons in composition with branching at the α or β position. SAR trends for targeting the Hh pathway were divergent from those related to HUVEC proliferation or VEGFR2 glycosylation. These results also suggest that modification of the sec-butyl side chain can lead to enhancement of the biological activity of itraconazole.

Abstract 3271: Inhibition of angiogenesis and tumor growth by itraconazole in primary xenograft models of human non-small cell lung cancer

Introduction: Lung cancer is the most common cause of cancer-related death in the US. Approximately 85 percent of cases are non-small cell lung cancer (NSCLC). Angiogenesis is a critical component to tumor growth. Bevacizumab is the only anti-angiogenic agent currently approved for NSCLC. Despite aggressive multimodality therapy, 5-year survival in patients with advanced stage NSCLC is exceedingly poor. Novel therapeutic strategies for NSCLC are critically needed.

The azole anti-fungal agent, itraconazole (ITRA) has been identified as a potential anti-angiogenic agent. In this study we further characterize the activity of ITRA in human umbilical vascular endothelial cell (HUVEC) based assays. Preclinical efficacy of ITRA is also examined as a single-agent and in combination with cisplatin in xenograft models of NSCLC generated with primary tumor tissue.

Methods: HUVECs were cultured in EGM-2 media (Lonza) and assayed in EGM-2 or EBM-2 media supplemented with recombinant growth factors, vascular endothelial growth factor (VEGF; 10 ng/ml), and basic fibroblast growth factor (bFGF; 12 ng/ml). Effects of ITRA on proliferation of HUVECs and three NSCLC cell lines, including H358 (bronchioalveolar carcinoma), H596 (adenosquamous carcinoma) and H1838 (adenocarcinoma) were evaluated by AqueousOne® (Promega). Additionally, HUVEC migration assays were carried out using an 8-micron pore Boyden chamber apparatus and endothelial tube formation assays were conducted using Geltrex® (Invitrogen) coated culture plates. To determine in vivo efficacy, mice bearing established xenografts derived from primary tumor tissue were treated orally with ITRA BID or QD at doses ranging from 75 to 100 mg/kg. In combination experiments, cisplatin (4 mg/kg) administered IP once weekly was given with ITRA. Mice were exposed to intravenous Hoechst 33342 prior to collection of tumors. Vascular area was determined by Hoechst 33342 and anti-CD31 staining. Tumor lysates were analyzed by immunoblot for Hif1α induction.

Results: ITRA demonstrates potent dose-dependent inhibition of HUVEC proliferation (IC50 &lt;0.7 μM). ITRA had no effect on proliferation in the panel of NSCLC cell lines tested (IC50 &lt;100 μM). ITRA inhibits HUVEC migration and tube formation with similar potency. In vivo, ITRA inhibits NSCLC tumor xenograft growth with maximum single-agent activity seen with 100 mg/kg BID treatment. Addition of ITRA to a cisplatin regimen significantly enhanced anti-tumor effects compared to either single-agent alone (p &lt;0.01). ITRA therapy resulted in increased tumor expression of HIF1α and significantly decreased tumor vascular area (p &lt;0.01).

Conclusion: The anti-angiogenic activity of ITRA and efficacy demonstrated in preclinical models of NSCLC supports development of this agent for the management of NSCLC in combination with standard of care chemotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3271. doi:10.1158/1538-7445.AM2011-3271