Targeting deoxycytidine kinase improves symptoms in mouse models of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease driven by lymphocyte activation against myelin autoantigens in the central nervous system leading to demyelination and neurodegeneration. The deoxyribonucleoside salvage pathway with the rate-limiting enzyme deoxycytidine kinase (dCK) captures extracellular deoxyribonucleosides for use in intracellular deoxyribonucleotide metabolism. Previous studies have shown that deoxyribonucleoside salvage activity is enriched in lymphocytes and required for early lymphocyte development. However, specific roles for the deoxyribonucleoside salvage pathway and dCK in autoimmune diseases such as MS are unknown. Here we demonstrate that dCK activity is necessary for the development of clinical symptoms in the MOG35-55 and MOG1-125 experimental autoimmune encephalomyelitis (EAE) mouse models of MS. During EAE disease, deoxyribonucleoside salvage activity is elevated in the spleen and lymph nodes. Targeting dCK with the small molecule dCK inhibitor TRE-515 limits disease severity when treatments are started at disease induction or when symptoms first appear. EAE mice treated with TRE-515 have significantly fewer infiltrating leukocytes in the spinal cord, and TRE-515 blocks activation-induced B and T cell proliferation and MOG35-55 -specific T cell expansion without affecting innate immune cells or naïve T and B cell populations. Our results demonstrate that targeting dCK limits symptoms in EAE mice and suggest that dCK activity is required for MOG35-55 -specific lymphocyte activation-induced proliferation.

Abstract 2635: Inhibiting deoxycytidine kinase significantly inhibits tumor growth in xenograft models of castration resistant prostate cancer

Mammalian cells synthesis deoxyribonucleoside triphosphate (dNTP) precursors for DNA replication via the de novo pathway (DNP), and to a lesser extent, via the nucleoside salvage pathway (NSP). Evidence suggests that rapid tumor cell growth associated with increased dNTP needs results in elevated NSP activity. As deoxycytidine kinase (dCK) is the rate-limiting enzyme of the NSP, and the only enzyme that can supply cells with all dNTP precursors for DNA replication, dCK has been implicated as a promising therapeutic target. Data from the Cancer Cell Line Encyclopedia demonstrated that most human cancer cell lines have elevated dCK gene expression (2- to 17-fold) therefore suggesting selective susceptibility of tumor cells to dCK inhibition. Accordingly, a potent first-in-class oral dCK inhibitor, TRE-515, was evaluated as a single agent in two human castration-resistant prostate cancer (CRPC) models. In the first CRPC model, C4-2, TRE-515 was administered intraperitoneally once a day for eight consecutive days (50 mg/kg, QDx8). TRE-515 significantly inhibited tumor growth (50.7%, p=0.021, relative to vehicle control), with 50% of the TRE-15 treated tumors regressing during the eight-day treatment window. In a repeat C4-2 study, TRE-515 monotherapy trended toward tumor growth inhibition, (53.7%, p=0.061, relative to vehicle control). A second CRPC model, 22Rv1, was then selected as it has been shown to carry DNP mutations, suggesting enhanced sensitivity to dCK inhibition. In this study, TRE-515 was dosed orally two times a day for 28 days (75 mg/kg, BIDx28) and plasma deoxycytidine (dC) concentrations (a substrate for dCK) were measured 7 hours after the morning dose on day 21. TRE-515 alone significantly inhibited tumor growth (49.9%, p=0.0004, relative to vehicle control), and growth inhibition was associated with a 77% increase in plasma dC levels (p<0.0001), relative to vehicle control, consistent with TRE-515 inhibitory activities on dCK. These data are in agreement with a previously reported study on target enzyme inhibition by TRE-515 which employed a clinically validated PET probe imaging of dCK. Taking together these results support the therapeutic potential for TRE-515 to selectively inhibit cancer cells that rely on dCK for DNA synthesis and rapid malignant proliferation. As such, TRE-515 is currently being evaluated in a phase 1 open-label, dose escalation study in solid tumors (NCT #05055609).

Citation Format: Caius G. Radu, Kenneth A. Schultz, Katharina Lückerath, H Michael Shepard, Johannes Czernin. Inhibiting deoxycytidine kinase significantly inhibits tumor growth in xenograft models of castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2635.

Targeting Adenosine with Adenosine Deaminase 2 to Inhibit Growth of Solid Tumors

Extracellular adenosine in tumors can suppress immune responses and promote tumor growth. Adenosine deaminase 2 (ADA2) converts adenosine into inosine. The role of ADA2 in cancer and whether it can target adenosine for cancer therapy has not been investigated. Here we show that increased ADA2 expression is associated with increased patient survival and enrichment of adaptive immune response pathways in several solid tumor types. Several ADA2 variants were created to improve catalytic efficiency, and PEGylation was used to prolong systemic exposure. In mice, PEGylated ADA2 (PEGADA2) inhibited tumor growth by targeting adenosine in an enzyme activity-dependent manner and thereby modulating immune responses. These findings introduce endogenous ADA2 expression as a prognostic factor and PEGADA2 as a novel immunotherapy for cancer. SIGNIFICANCE: This study identifies ADA2 as a prognostic factor associated with prolonged cancer patient survival and introduces the potential of enzymatic removal of adenosine with engineered ADA2 for cancer immunotherapy.

Abstract PO074: Logic-gating HER2 CAR-T to the tumor microenvironment mitigates on-target, off-tumor toxicity without compromising cytotoxicity against HER2-over-expressing tumors

Chimeric antigen receptor (CAR) modified T cells have demonstrated promising anti-tumor effects in hematologic cancers. Because CD19 expression is restricted to B cells, CD19 CAR-T B cell aplasia is a tolerable on-target, off-tumor toxicity. However, antigens found in solid tumors, such as HER2, are also expressed in many critical tissues. HER2 overexpression/amplification occurs in many malignancies, including breast, gastric, lung, ovarian and pancreas. With its elevated receptor copy number and relatively homogeneous expression following gene amplification, HER2 represents an attractive antigen to target via CAR-T. Unfortunately, severe toxicity related to off-tumor binding of the CAR-T to HER2 present in normal tissue may limit the use of CAR-T therapy. To circumvent this issue, we designed a “logic-gated” HER2-targeted CAR-T that preferentially recognizes HER2 in the tumor microenvironment (TME), thereby limiting on-target toxicity of low HER2 levels expressed in normal tissue. HER2 scFvs with pH-restricted binding towards physiologic levels of HER2 were screened as CARs in primary T cells and demonstrated pH dependent cytotoxicity and cytokine release in vitro; the pH-dependence was also preserved in the context of HER2 CAR-Ts vs. ungated HER2 CARs. Antitumor activity and cellular kinetics were assessed in NSG mice bearing human HER2-amplified xenografts. Logic-gated HER2 CARs were capable of regressing established gastric (NCI-N87), breast (BT-474), and ovarian (SK-OV-3) tumors with HER2 amplification. Importantly, logic-gated HER2 CAR-T cells were also capable of completely regressing large established gastric carcinoma xenografts that had progressed on prior trastuzumab therapy. Anti-tumor activity and cellular kinetics were dose dependent, with robust in vivo expansion to peak levels of 190,000 copies/µg gDNA. On-target, off-tumor safety of the CAR-Ts was assessed in NSG mice with enforced expression of human HER2 and luciferase in hepatocytes using a hydrodynamic gene delivery (HGD) model. Compared to ungated HER2 CAR-T constructs, logic-gated HER2 CAR-Ts did not eliminate hepatocyte luciferase expression with human HER2 +1 staining in mouse livers as determined by Herceptest scoring of livers at necropsy. In conclusion, these results demonstrate that a logic-gated HER2-targeted CAR-T is capable of eliminating established HER2-amplified malignancies in a xenograft model, while mitigating potential on-target, off-tumor toxicity.

Citation Format: Wei Zhang, Qun He, Benjamin Lopez, Jianfang Hu, Anirban Kundu, Michelle C. Andraza, Alissa R. Kerner, Gregory H. Schreiber, H. Michael Shepard, Gregory I. Frost. Logic-gating HER2 CAR-T to the tumor microenvironment mitigates on-target, off-tumor toxicity without compromising cytotoxicity against HER2-over-expressing tumors [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO074.

The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

Hyaluronan accumulation in the tumor microenvironment is associated with poor prognosis in several solid human cancers. To understand the role of stromal hyaluronan in tumor progression, we engineered 3T3HAS3, a hyaluronan-producing fibroblast cell line, by lentiviral transduction of Balb/c 3T3 cells with the human hyaluronan synthase 3(HAS3) gene. 3T3HAS3 cells significantly enhanced tumor growth when co-grafted with MDA-MB-468 cells in nude mice. Immunohistochemical analysis of the xenograft tumors showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of MDA-MB-468 + 3T3HAS3 co-grafts was greatly reduced upon hyaluronan degradation by lentiviral transduction of a human hyaluronidase gene in 3T3HAS3 cells, or by systemic administration of pegvorhyaluronidase alfa (PEGPH20). In contrast, the growth of the co-graft tumors was not inhibited when CD44 expression was reduced or ablated by small hairpin RNA-mediated CD44 knockdown in MDA-MB-468 cells, CD44 CRISPR knockout in 3T3HAS3 cells, or by grafting these cells in CD44 knockout nude mice. Collectively, these data demonstrate that tumor growth of an engineered xenograft breast cancer model with hyaluronan-accumulating stroma can be dependent on hyaluronan and independent of CD44.

Multiple cancer-specific antigens are targeted by a chimeric antigen receptor on a single cancer cell

Human cancer cells were eradicated by adoptive transfer of T cells transduced with a chimeric antigen receptor (CAR) made from an antibody (237Ab) that is highly specific for the murine Tn-glycosylated podoplanin (Tn-PDPN). The objectives were to determine the specificity of these CAR-transduced T (CART) cells and the mechanism for the absence of relapse. We show that although the 237Ab bound only to cell lines expressing murine Tn-PDPN, the 237Ab-derived 237CART cells lysed multiple different human and murine cancers not predicted by the 237Ab binding. Nevertheless, the 237CART cell reactivities remained cancer specific because all recognitions were dependent on the Tn glycosylation that resulted from COSMC mutations that were not present in normal tissues. While Tn was required for the recognition by 237CART, Tn alone was not sufficient for 237CART cell activation. Activation of 237CART cells required peptide backbone recognition but tolerated substitutions of up to 5 of the 7 amino acid residues in the motif recognized by 237Ab. Together, these findings demonstrate what we believe is a new principle whereby simultaneous recognition of multiple independent Tn-glycopeptide antigens on a cancer cell makes tumor escape due to antigen loss unlikely.

Abstract 3067: OHM-581, a dual JAK2-BET inhibitor for the treatment of myelofibrosis and other hematologic malignancies

Ruxolitinib is the only JAK2 inhibitor approved for myelofibrosis (MF). Although JAK2 inhibitor therapy improves splenomegaly and systemic symptoms, it does not significantly reduce the MF clone or alter the natural history and survival in most patients. The novel small molecule OHM-581 not only inhibits JAK2, but also BET (bromodomain and extra terminal) proteins such as BRD4. Dual JAK2 and BET inhibition using other molecules has shown superior efficacy in murine MF models compared with JAK2 inhibition alone including amelioration of fibrosis, synergistic induction of apoptosis of primary patient, post-MF secondary acute myeloid leukemia (sAML) blasts, and significant improvement of the survival of mice engrafted with human sAML cells. OHM-581 is being developed for the treatment of MF and other hematologic malignancies to leverage these advantages of dual JAK2-BET inhibition.

Results: In vitro biochemical assays show OHM-581 to inhibit BRD4 BD1 and BD2 with IC50s of 189 and 116 nM, respectively, and JAK2 with an IC50 of 7.1 nM (JAK1=244 nM; JAK3=76 nM). No significant hERG liability was seen. OHM-581 displays significant anti-proliferative activity against multiple liquid cancer cell lines. Notably, the GI50 values for MV4-11 (AML, MLL fusion+), HEL 92.1.7 (AML, JAK2V617F+) and UKE-1 (AML, JAK2V617F+) are 32, 87 and 140 nM, respectively. Consistent with its mechanism of action, OHM-581 robustly down-regulates cMYC expression (cMYC mRNA down-regulation IC50=18.6 nM compared with 41.4 nM for BET inhibitor JQ1) and JAK2 signaling. Moreover, the compound triggers apoptosis in MV4-11 cells (~7-fold increase in Caspase 3/7 activity at 24-h). OHM-581 does not reflect an efflux liability, the efflux ratio being nearly 1.8. OHM-581 is soluble in PBS pH7.4 at 26 µM and metabolically stable with nearly 51%, 67% and 88% remaining in mouse, rat and human liver microsomes, respectively, after 30 min. OHM-581 exhibits an oral bioavailability of ~40%. As compared to the small molecule fedratinib, which is also being developed for MF, OHM-581 does not inhibit thiamine uptake. Dose proportionality with a greater than proportional increase in both Cmax and AUC at doses up to 60 mg/kg, and a saturation of Cmax at doses of 60 mg/kg and higher, are observed for OHM-581. In vivo efficacy studies using an MV4-11 xenograft model demonstrate robust tumor inhibition (~75-90%) following doses of 30 and 60 mg/kg po BID for 20 days.

Conclusion: OHM-581 is a novel dual inhibitor of JAK2 and BET that has potential as a therapeutic agent for MF and other hematologic malignancies. In addition to IND-enabling studies, current OHM-581 development activities are focused on further proof-of-concept analyses using preclinical models of MF and other myeloproliferative neoplasms, with results to be reported.

Citation Format: Ram S. Upadhayaya, Raghava Reddy Kethiri, Stephan W. Morris, H. Michael Shepard, Samuel R. Saks, Michael J. Weickert. OHM-581, a dual JAK2-BET inhibitor for the treatment of myelofibrosis and other hematologic malignancies [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 3067.

KIAA1199 expression and hyaluronan degradation colocalize in multiple sclerosis lesions

Modification of hyaluronan (HA) accumulation has been shown to play a key role in regulating inflammatory processes linked to the progression of multiple sclerosis (MS). The aim of this study was to characterize the enzymatic activity involved in HA degradation observed within focal demyelinating lesions in the experimental autoimmune encephalomyelitis (EAE) animal model. EAE was induced in 3-month-old female C57BL/6J mice by immunization with myelin oligodendrocyte glycoprotein 33–35 (MOG33–35) peptide. The mice were monitored for 21 days. Formalin-fixed paraffin-embedded tissue from control and EAE mice were labeled with an immunoadhesin against HA, antibodies against KIAA1199 and glial fibrillary acidic protein, a marker for astrocytes. In situ hybridization was conducted using a KIAA1199 nucleic acid probe. In histologic sections of spinal cord from EAE mice, abnormal HA accumulation was observed in the close vicinity of the affected areas, whereas HA was totally degraded within the focal loci of damaged tissue. KIAA1199 immunoreactivity was exclusively associated with focal loci in damaged white columns of the spinal cord. KIAA1199 was mainly expressed by activated astrocytes that invaded damaged tissue. Similar findings were observed in tissue from an MS patient. Here, we show that KIAA1199, a protein that plays a role in a HA degradation pathway independent of the canonical hyaluronidases such as PH20, is specifically expressed in tissue lesions in which HA is degraded. KIAA1199 expression by activated astrocytes may explain the focal HA degradation observed during progression of MS and could represent a possible new therapeutic target.

Parallel Accumulation of Tumor Hyaluronan, Collagen, and Other Drivers of Tumor Progression

Purpose: The tumor microenvironment (TME) evolves to support tumor progression. One marker of more aggressive malignancy is hyaluronan (HA) accumulation. Here, we characterize biological and physical changes associated with HA-accumulating (HA-high) tumors.Experimental Design: We used immunohistochemistry, in vivo imaging of tumor pH, and microdialysis to characterize the TME of HA-high tumors, including tumor vascular structure, hypoxia, tumor perfusion by doxorubicin, pH, content of collagen. and smooth muscle actin (α-SMA). A novel method was developed to measure real-time tumor-associated soluble cytokines and growth factors. We also evaluated biopsies of murine and pancreatic cancer patients to investigate HA and collagen content, important contributors to drug resistance.Results: In immunodeficient and immunocompetent mice, increasing tumor HA content is accompanied by increasing collagen content, vascular collapse, hypoxia, and increased metastatic potential, as reflected by increased α-SMA. In vivo treatment of HA-high tumors with PEGylated recombinant human hyaluronidase (PEGPH20) dramatically reversed these changes and depleted stores of VEGF-A165, suggesting that PEGPH20 may also diminish the angiogenic potential of the TME. Finally, we observed in xenografts and in pancreatic cancer patients a coordinated increase in HA and collagen tumor content.Conclusions: The accumulation of HA in tumors is associated with high tIP, vascular collapse, hypoxia, and drug resistance. These findings may partially explain why more aggressive malignancy is observed in the HA-high phenotype. We have shown that degradation of HA by PEGPH20 partially reverses this phenotype and leads to depletion of tumor-associated VEGF-A165. These results encourage further clinical investigation of PEGPH20. Clin Cancer Res; 24(19); 4798-807. ©2018 AACR.

Abstract 2101: The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

The abnormal accumulation of hyaluronan in the solid tumor microenvironment is associated with poor prognosis in several human cancers. Hyaluronan often accumulates in the tumor stroma. To understand the role of hyaluronan-accumulating stroma in tumor progression, we engineered a hyaluronan-producing fibroblast cell line 3T3HAS3 by lentiviral transduction of the human hyaluronan synthase 3 gene into Balb/c 3T3 cells. The 3T3HAS3 cells produced significant amounts of hyaluronan in vitro, which bind to the cell surface of the human breast cancer cell line MDA-MB-468. When co-grafted with MDA-MB-468 cells in nude mice, 3T3HAS3 significantly enhanced tumor growth. Immunohistochemical analysis of tumor xenografts showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of this co-graft model required hyaluronan production from 3T3HAS3 cells, as demonstrated by the delayed tumor growth upon hyaluronan removal by expression of the human PH20 gene in 3T3HAS3 cells, or by systemic administration of PEGylated recombinant human PH20 (PEGPH20). In contrast, neither the expression of CD44, a well-characterized hyaluronan receptor, in tumor and stromal fibroblasts, nor the binding of hyaluronan to CD44 in MDA-MB-468 tumor cells was essential for tumor growth. Small scale screening of signaling changes in xenograft tumors suggested that the AMPK/mTOR pathway may respond to hyaluronan removal by PEGPH20. Collectively, these data demonstrate that the growth of an engineered breast cancer xenograft model with hyaluronan-accumulating stroma is dependent on hyaluronan, and that hyaluronan-CD44 interaction may not be the main mechanism through which hyaluronan promotes tumor progression in certain tumors.

Citation Format: Chunmei Zhao, Benjamin J. Thompson, Kelly Chen, Mathieu Marella, Susan Zimmerman, Trevor Kimbler, Barbara Blouw, Sheryl Garrovillo, Lei Huang, Adrian Radi, Zhongdong Huang, H. Michael Shepard, Sanna Rosengren, Christopher D. Thanos, Daniel C. Maneval. The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2101.

Phase 1 trials of PEGylated recombinant human hyaluronidase PH20 in patients with advanced solid tumours

Background:

Hyaluronan accumulation in tumour stroma is associated with reduced survival in preclinical cancer models. PEGPH20 degrades hyaluronan to facilitate tumour access for cancer therapies. Our objective was to assess safety and antitumour activity of PEGPH20 in patients with advanced solid tumours.

Methods:

In HALO-109-101 (N=14), PEGPH20 was administered intravenously once or twice weekly (0.5 or 50 μg kg⁻¹) or once every 3 weeks (0.5–1.5 μg kg⁻¹). In HALO-109-102 (N=27), PEGPH20 was administered once or twice weekly (0.5–5.0 μg kg⁻¹), with dexamethasone predose and postdose.

Results:

Dose-limiting toxicities included grade ⩾3 myalgia, arthralgia, and muscle spasms; the maximum tolerated dose was 3.0 μg kg⁻¹ twice weekly. Plasma hyaluronan increased in a dose-dependent manner, achieving steady state by Day 8 in multidose studies. A decrease in tumour hyaluronan level was observed in 5 of the 6 patients with pretreatment and posttreatment tumour biopsies. Exploratory imaging showed changes in tumour perfusion and decreased tumour metabolic activity, consistent with observations in animal models.

Conclusions:

The tumour stroma has emerging importance in the development of cancer therapeutics. PEGPH20 3.0 μg kg⁻¹ administered twice weekly is feasible in patients with advanced cancers; exploratory analyses indicate antitumour activity supporting further evaluation of PEGPH20 in solid tumours.

Interstitial Pressure in Pancreatic Ductal Adenocarcinoma Is Dominated by a Gel-Fluid Phase

Elevated interstitial fluid pressure can present a substantial barrier to drug delivery in solid tumors. This is particularly true of pancreatic ductal adenocarcinoma, a highly lethal disease characterized by a robust fibroinflammatory response, widespread vascular collapse, and hypoperfusion that together serve as primary mechanisms of treatment resistance. Free-fluid pressures, however, are relatively low in pancreatic ductal adenocarcinoma and cannot account for the vascular collapse. Indeed, we have shown that the overexpression and deposition in the interstitium of high-molecular-weight hyaluronan (HA) is principally responsible for generating pressures that can reach 100 mmHg through the creation of a large gel-fluid phase. By interrogating a variety of tissues, tumor types, and experimental model systems, we show that an HA-dependent fluid phase contributes substantially to pressures in many solid tumors and has been largely unappreciated heretofore. We investigated the relative contributions of both freely mobile fluid and gel fluid to interstitial fluid pressure by performing simultaneous, real-time fluid-pressure measurements with both the classical wick-in-needle method (to estimate free-fluid pressure) and a piezoelectric pressure catheter transducer (which is capable of capturing pressures associated with either phase). We demonstrate further that systemic treatment with pegylated recombinant hyaluronidase (PEGPH20) depletes interstitial HA and eliminates the gel-fluid phase. This significantly reduces interstitial pressures and leaves primarily free fluid behind, relieving the barrier to drug delivery. These findings argue that quantifying the contributions of free- and gel-fluid phases to hydraulically transmitted pressures in a given cancer will be essential to designing the most appropriate and effective strategies to overcome this important and frequently underestimated resistance mechanism.

Developments in therapy with monoclonal antibodies and related proteins

Monoclonal antibody therapeutics have been approved for over 30 targets and diseases, most commonly cancer. Antibodies have become the new backbone of the pharmaceutical industry, which previously relied on small molecules. Compared with small molecules, monoclonal antibodies (mAbs) have exquisite target selectivity and hence less toxicity as a result of binding other targets. The clinical value of both mAbs and ligand traps has been proven. New applications of mAbs are being tested and mAbs have now been designed to target two (bi-specific, eg TNF-α and IL-17) or more targets simultaneously, augmenting their therapeutic potential. Because of space limitations and the wide ranging scope of this review there are regrettably, but inevitably, omissions and missing citations. We have chosen to highlight the first successes in inflammatory diseases and cancer, but a broader overview of approved mAbs and related molecules can be found in Table 1.

PH20 is not expressed in murine CNS and oligodendrocyte precursor cells

Objective

Expression of Spam1/PH20 and its modulation of high/low molecular weight hyaluronan substrate have been proposed to play an important role in murine oligodendrocyte precursor cell (OPC) maturation in vitro and in normal and demyelinated central nervous system (CNS). We reexamined this using highly purified PH20.

Methods

Steady‐state expression of mRNA in OPCs was evaluated by quantitative polymerase chain reaction; the role of PH20 in bovine testicular hyaluronidase (BTH) inhibition of OPC differentiation was explored by comparing BTH to a purified recombinant human PH20 (rHuPH20). Contaminants in commercial BTH were identified and their impact on OPC differentiation characterized. Spam1/PH20 expression in normal and demyelinated mouse CNS tissue was investigated using deep RNA sequencing and immunohistological methods with two antibodies directed against recombinant murine PH20.

Results

BTH, but not rHuPH20, inhibited OPC differentiation in vitro. Basic fibroblast growth factor (bFGF) was identified as a significant contaminant in BTH, and bFGF immunodepletion reversed the inhibitory effects of BTH on OPC differentiation. Spam1 mRNA was undetected in OPCs in vitro and in vivo; PH20 immunolabeling was undetected in normal and demyelinated CNS.

Interpretation

We were unable to detect Spam1/PH20 expression in OPCs or in normal or demyelinated CNS using the most sensitive methods currently available. Further, “BTH” effects on OPC differentiation are not due to PH20, but may be attributable to contaminating bFGF. Our data suggest that caution be exercised when using some commercially available hyaluronidases, and reports of Spam1/PH20 morphogenic activity in the CNS may be due to contaminants in reagents.

Abstract A46: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma

Hyaluronan (also known as hyaluronic acid or HA) is a megadalton sized glycosaminoglycan present in the extracellular matrix. The abnormal accumulation of HA in the solid tumor microenvironment (TME) of several human cancers, including pancreatic, breast, colon and prostate, has been well studied and is associated with poor prognosis. In certain breast cancer specimens with a HA-high status, HA is found to be significantly associated with the stromal compartment rather than with tumor cells. To understand the interaction between tumor cells and a HA containing stromal compartment, we engineered a HA-high stromal cell line by lentiviral transduction of the human HAS3 gene into Balb/c 3T3 fibroblast cells. The 3T3/HAS3 cells produced significant amounts of HA in vitro, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Immunohistochemical analysis of tumor xenograft samples showed that MDA-MB-468 cells were surrounded by HA-high stromal cells, closely resembling the tumor morphology observed in human breast cancer specimens. Tumor growth in this co-grafting model was highly dependent on the presence of 3T3/HAS3 cells, and required HA produced by 3T3/HAS3 cells. Ganciclovir blocked the growth of MDA-MB-468 co-inoculated with 3T3/HAS3/hsv-TK, as did HA removal either by the expression of the HA degrading enzyme PH20, directly in 3T3/HAS3 cells or by exogenous administration of PEGPH20, a pegylated version of PH20 engineered for extended half-life. Interestingly, the presence of 3T3/HAS3 cells was found to be most critical during early stages of tumor progression and was non-essential for tumor maintenance once tumors were fully established, as ganciclovir had little impact on tumor growth when tumor size was larger than 500 mm3 but prevented tumor growth when administered at inoculation and inhibited tumor growth when treatment started at a smaller tumor size (200 mm3, 90.4% TGI). We have developed a tumor xenograft model that mimics breast cancer with a HA-high status in the tumor stromal compartment. Further characterization of this model will provide insight into the mechanisms by which increased levels of HA and the associated changes in the TME promote disease progression in breast cancer.

Citation Format: Chunmei Zhao, Mathieu Marella, Lei Huang, Anne Kultti, Susan Zimmerman, Caroline EN Chou, Jesse Bahn, Adrian Radi, Zhongdong Huang, H Michael Shepard, Christopher D. Thanos. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A46.

Phase Ib Study of PEGylated Recombinant Human Hyaluronidase and Gemcitabine in Patients with Advanced Pancreatic Cancer

PURPOSE

This phase Ib study evaluated the safety and tolerability of PEGylated human recombinant hyaluronidase (PEGPH20) in combination with gemcitabine (Gem), and established a phase II dose for patients with untreated stage IV metastatic pancreatic ductal adenocarcinoma (PDA). Objective response rate and treatment efficacy using biomarker and imaging measurements were also evaluated.

EXPERIMENTAL DESIGN

Patients received escalating intravenous doses of PEGPH20 in combination with Gem using a standard 3+3 dose-escalation design. In cycle 1 (8 weeks), PEGPH20 was administrated twice weekly for 4 weeks, then once weekly for 3 weeks; Gem was administrated once weekly for 7 weeks, followed by 1 week off treatment. In each subsequent 4-week cycle, PEGPH20 and Gem were administered once weekly for 3 weeks, followed by 1 week off. Dexamethasone (8 mg) was given pre- and post-PEGPH20 administration. Several safety parameters were evaluated.

RESULTS

Twenty-eight patients were enrolled and received PEGPH20 at 1.0 (n = 4), 1.6 (n = 4), or 3.0 μg/kg (n = 20), respectively. The most common PEGPH20-related adverse events were musculoskeletal and extremity pain, peripheral edema, and fatigue. The incidence of thromboembolic events was 29%. Median progression-free survival (PFS) and overall survival (OS) rates were 5.0 and 6.6 months, respectively. In 17 patients evaluated for pretreatment tissue hyaluronan (HA) levels, median PFS and OS rates were 7.2 and 13.0 months for "high"-HA patients (n = 6), and 3.5 and 5.7 months for "low"-HA patients (n = 11), respectively.

CONCLUSIONS

PEGPH20 in combination with Gem was well tolerated and may have therapeutic benefit in patients with advanced PDA, especially in those with high HA tumors. Clin Cancer Res; 22(12); 2848-54. ©2016 AACR.

Breaching the Castle Walls: Hyaluronan Depletion as a Therapeutic Approach to Cancer Therapy

Hyaluronan (HA) has many functions in the extracellular milieu of normal and diseased tissues. Disease-associated HA accumulation has been shown to predict a worsened prognosis in cancer patients, with tumors having a high-extracellular HA content (HA-high) being more aggressive than their HA-low counterparts. HA-high tumor aggressiveness is derived from the specialized biomechanical and molecular properties of the HA-based assembly of HA binding proteins and the growth-promoting factors that accumulate in it. Biophysical characteristics of an HA-high tumor microenvironment include high tumor interstitial pressure, compression of tumor vasculature, and resulting tumor hypoxia. Within the tumor cell membrane, HA receptors, primarily CD44 and RHAMM, anchor the HA-high extracellular network. HA-CD44 association on the tumor cell surface enhances receptor tyrosine kinase activity to drive tumor progression and treatment resistance. Together, malignant cells in this HA-high matrix may evolve dependency on it for growth. This yields the hypothesis that depleting HA in HA-high tumors may be associated with a therapeutic benefit. A pegylated form of recombinant human hyaluronidase PH20 (PEGPH20) has been deployed as a potential cancer therapeutic in HA-high tumors. PEGPH20 can collapse this matrix by degrading the HA-assembled tumor extracellular framework, leading to tumor growth inhibition, preferentially in HA-high tumors. Enzymatic depletion of HA by PEGPH20 results in re-expansion of the tumor vasculature, reduction in tumor hypoxia, and increased penetration of therapeutic molecules into the tumor. Finally, HA-depletion results in reduced signaling via CD44/RHAMM. Taken together, HA-depletion strategies accomplish their antitumor effects by multiple mechanisms that include targeting both biophysical and molecular signaling pathways. Ongoing clinical trials are examining the potential of PEGPH20 in combination with partner therapeutics in several cancers.

Abstract 982: Hyaluronan (HA) depletion increases tumor accessibility of T cell and therapeutic PD-L1 monoclonal antibody in HAhigh tumors

Tumor initiation and progression is a complex interaction between host and tumor. One of the essential elements for tumor progression is evasion of the host immune system. Among the mechanisms important for host immune cell evasion is the amplification of receptor tyrosine kinases, and tumor secretion of immune suppressive cytokines, like TGF-β, suppression of activated T cells by various intrinsic immune response regulatory mechanisms 1-3. Additionally, tumor cells evolve to express cell-associated programmed death 1 (PD1) ligands (PD-L1 or LD-L2), which promotes tumor cell growth by inactivating PD1 expressing activated T cells 3-4. Recent reports suggest a role of the tumor microenvironment (TME) as an immunosuppressive environment by accumulating hyaluronan (HA)5-7, which then results in accumulation of water and resulting high interstitial fluid pressure and sequelae, including blood vessel compression, and decreased perfusion8-10. Hyaluronan depletion from solid tumors with high levels of HA (HAhigh) reverses these physiological effects, resulting in increased chemotherapeutic drug penetration and tumor growth inhibition in preclinical animal models 8-10. In this report we investigated whether increasing the access of therapeutic immune checkpoint monoclonal antibodies and effector T cells into the HAhigh tumor can enhance activated T cell-mediated tumor cell lysis. We have generated human hyaluronan synthase and PD-L1 overexpressing tumor cell lines to study (i) the role of HA in PD-1 and PD-L1 interaction in HAhigh tumor cells, and (ii) whether HA depletion increases the efficacy of tumor cell killing by PD-1 positive cytotoxic T lymphocytes in the presence of PD-L1 blocking monoclonal antibody. Our data show that HAhigh tumor cells form an HA-rich barrier that restricts T cell access to tumor cell and HA depletion by PEGPH20, a pegylated PH20, allowed T cells to access tumor cell. HA depletion increases HAhigh PD-L1 positive tumor cells killing by activated T cell in the presence of anti-human PD-L1 monoclonal antibody (MAb). Furthermore, HA depletion by PEGPH20 increased the access of T cell and anti-human PD-L1 MAb in HAhigh xenograft tumors, suggesting that PEGPH20 may enhance efficacy of immune check point blocking therapeutic PD-L1 MAb in HAhigh tumors.

References:

1. Rabinovich et al. Annu Rev Immunol., 2007;25:267-96.

2. Hudzika et al. Cell Growth Differ. 1990; 1:129-34.

3. Quezada et al. British Journal of Cancer, 2013; 108: 1560-1565.

4. Zou et al. Nature Reviews Immunology, 2008; 8: 467-477.

5. Sironen et al. Exp Cell Res 2011;317:383-91.

6. Kultti et al. Cancers 2012;4:873-903.

7. Tlsty et al. Annu Rev Pathol 2006;1:119-50.

8. Thompson et al. Mol Cancer Ther 2010;9:3052-64.

9. Jacobetz et al. Gut 2013;62:112-20.

10. Provenzano et al. Cancer Cell 2012;21:418-29.

Citation Format: Netai C. Singha, Chunmei Zhao, Jesse Bahn, Adrian Radi, H. Michael Shepard, Zhongdong Huang. Hyaluronan (HA) depletion increases tumor accessibility of T cell and therapeutic PD-L1 monoclonal antibody in HAhigh tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 982. doi:10.1158/1538-7445.AM2015-982

Abstract 2392: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models

Hyaluronan (also known as hyaluronic acid or HA) is a nonsulfated glycosaminoglycan in the extracellular matrix. Elevated levels of HA in the tumor microenvironment have been associated with poor prognosis of several human cancers, including pancreatic, breast, colon and prostate. In many cases of breast cancer, HA is found to be associated with the stromal compartment. To understand the interaction between tumor cells and HA containing stromal compartment, we engineered a HA-high stromal cell line by overexpressing the human HAS3 gene in Balb/c 3T3 fibroblast cells. In vitro, the 3T3/HAS3 cells produced and secreted HA, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Furthermore, depletion of HA with PEGPH20 (a pegylated form of the recombinant human PH20 protein) significantly inhibited the growth of MDA-MB-468 cells co-grafted with 3T3/HAS3 cells, suggesting that the HA provided by 3T3/HAS3 cells is critical for the growth of MDA-MB-468 cells in vivo. Immunohistochemical analysis of tumor xenograft samples showed that HA-low MDA-MB-468 cells were surrounded by HA-high stromal cells, resembling the tumor morphology observed in certain breast cancer patients. To model for breast cancers with tumor cell-associated HA, we overexpressed the human HAS3 gene directly in MDA-MB-468 cells. The in vivo growth of MDA-MB-468 was significantly enhanced by HAS3 overexpression. Depletion of HA by PEGPH20 synergized with Abraxane and improved its anti-cancer efficacy in the MDA-MB-468/HAS3 xenograft model compared to PEGPH20 and Abraxane alone. Taken together, we have developed tumor xenograft models that mimic HA-high breast cancers and can be used to test the pharmacological activity of anticancer agents. Further characterization of these models will provide insights into the understanding of the mechanisms by which increased levels of HA and the associated changes in the tumor microenvironment promote the disease progression in breast cancer and how depletion of HA can interfere with this process and synergize with chemotherapies to inhibit tumor progression.

Citation Format: Chunmei Zhao, Mathieu Marella, Susan Zimmerman, Lei Huang, H. Michael Shepard, Zhongdong Huang. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2015-2392

Abstract 576: Development and analytical validation of a novel assay for tissue detection of hyaluronan in the tumor microenvironment to select patients for molecularly targeted pancreatic cancer therapies

Background: Hyaluronan (HA), a glycosaminoglycan distributed in the extracellular matrix, is frequently upregulated in cancer and correlates with disease progression. Administration of a first-in-class PEGylated recombinant human hyaluronidase (PEGPH20) depletes HA, unmasks HA around tumor cells and decreases tumor interstitial fluid pressure, increasing accessibility to systemically administered agents in preclinical models. PEGPH20 recently received Orphan Drug designation in pancreatic ductal adenocarcinoma (PDA) in the USA. We report the development and analytical validation of a novel prototype assay for a companion diagnostic to select patients with PDA for molecularly targeted therapies with PEGPH20.

Design: A recently described biotinylated recombinant immunoadhesin (HTI-601, Jadin 2014) was adapted for use in an immunohistochemistry-based assay on formalin-fixed paraffin-embedded tissue. Sensitivity, specificity, and within-laboratory precision studies were performed in a research mode and then at a central laboratory on a validation set of approximately 200 tumor and normal tissues under GCP conditions. Both pathologist scoring and operator-assisted image analysis (positive pixel count for strong positive pixels) were evaluated.

Results: Analytical sensitivity studies identified an optimal probe dilution of 0.417 μg/mL on an immunostainer based on dynamic range in 4 human tumor xenografts containing differential levels of HA. The frequency of high HA observed was 62.7% of archival PDA (N = 75). During analytical specificity, 5.1% of 75 PDA and 3 normal adjacent tissue samples had faint or focal staining after pre-digestion with recombinant PH20 hyaluronidase. No cross-reactivity was identified in 99 normal human tissues across a panel of histotypes; only 1 (1.0%) colon sample had staining of macrophages. Within-laboratory precision among three observers’ annotations had average%CVs as follows: between day 4.8%, between run 12.2%, and repeatability 16.6%.

Conclusion: The sensitivity, specificity and within-laboratory precision of the prototype assay using image analysis are acceptable. The frequency of high HA expression is similar to other studies in the literature. Cross-reactivity was focal and faint so is unlikely to interfere. Subset analysis showed contributions to%CV to be higher for HAlow than HAmedium or HAhigh samples as expected. These findings warrant further evaluation of HTI-601 staining on biopsies for PEGPH20-associated therapies in clinical studies.

Citation Format: Arnold B. Gelb, Ping Jiang, Laurence Jadin, Daniel C. Maneval, H. Michael Shepard. Development and analytical validation of a novel assay for tissue detection of hyaluronan in the tumor microenvironment to select patients for molecularly targeted pancreatic cancer therapies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 576. doi:10.1158/1538-7445.AM2015-576

Abstract B86: Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances nab-paclitaxel plus gemcitabine efficacy in human pancreatic cancer xenografts

Hyaluronan (HA) over-accumulation in the extracellular matrix (ECM) of many solid tumors is associated with tumor progression and poor prognosis. Accordingly, an HA-degrading enzyme, PEGPH20, is being developed to deplete tumor-associated HA in the ECM. In preclinical animal models, enzymatic removal of ECM HA with PEGPH20 is associated with remodeling of the tumor stroma, reduction of tumor interstitial fluid pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy. As pancreatic ductal adenocarcinoma (PDA) has been identified as a cancer type that accumulates high levels of HA, and the combination of albumin-bound paclitaxel (nab-paclitaxel, NAB) and gemcitabine (GEM) has been shown to improve survival in patients with metastatic pancreatic cancer (Von Hoff 2013), preclinical studies were conducted using human PDA xenograft models to investigate whether PEGPH20 enhanced the anti-tumor activity of NAB and GEM. In brief, nude mice were inoculated with human BxPC3 PDA cells, or with HA-high BxPC3/HAS3 cells, a cell line engineered to over-express HA, adjacent to the right tibial periosteum. Tumor growth was monitored via ultrasonography. When tumors reached ~350 mm3, mice were staged into 8 treatment groups: (1) vehicle control; (2) PEGPH20 alone, 4.5 mg/kg; (3) NAB alone, 10 mg/kg; (4) GEM alone, 180 mg/kg; (5) NAB plus PEGPH20; (6) GEM plus PEGPH20; (7) NAB plus GEM; and (8) NAB plus GEM plus PEGPH20. Vehicle, PEGPH20 and/or NAB was administered intravenously starting on study day 0, and then dosed twice weekly for four weeks. GEM was administered intraperitoneally starting on study day 1 and then dosed weekly for three weeks. Histology of tumors confirmed HA removal in all PEGPH20 treated groups. In the parental BxPC3 model, the addition of PEGPH20 increased the anti-tumor efficacy of NAB plus GEM by 15% (81% vs. 66%, respectively) and extended median survival time (MST) by >31% (68d vs. 52d, respectively); whereas in the HA-high BxPC3/HAS3 model, PEGPH20 increased the anti-tumor efficacy of NAB plus GEM by 34% (104% vs. 70%) and extended MST by >125% (72d vs. 32d, respectively). As Jacobetz et al. (2013) have shown that PEGPH20 treatment increases the intratumoral delivery of GEM in genetically engineered mouse PDA models; we evaluated whether PEGPH20 also improves intratumoral accumulation of paclitaxel in the BxPC3/HAS3 model vs. NAB alone. The co-administration of PEGPH20 with NAB increased intratumoral paclitaxel accumulation by >43% one hour following a single administration. Further, PEGPH20 enhanced NAB plus GEM mediated reduction in the PDA serum biomarkers CA19-9 and CEA in both models. As KRAS mutations occur in 90% of non neuro-endocrine pancreatic tumors (Thomas 2007), and BxPC3 cells are KRAS WT, we repeated these studies in KRAS mutant/HA-low AsPC1 xenografts, and engineered KRAS mutant/HA-high AsPC1/HAS3 PDA xenografts. Mice were inoculated and tumor growth was monitored as described above. Animals were then staged into 8 groups and then dosed when tumors reached ~350 mm3. The PEGPH20 dose in these studies was reduced to 37.5 μg/kg to approximate dosing in ongoing clinical trials (NCT01839487). As predicted by tumor HA level, the addition of PEGPH20 did not increase the anti-tumor efficacy or survival in the HA-low parental AsPC1 model. In the HA-high AsPC1/HAS3 model, the addition of PEGPH20 increased the anti-tumor efficacy of NAB plus GEM by 25% (78% vs. 53%, respectively) and extended MST by >31% (74d vs. 48d, respectively). Taken together, the data suggest that PEGPH20-mediated HA removal significantly increases the anti-tumor efficacy of NAB plus GEM in HA-high mouse models of PDA. Clinical trials are currently ongoing to evaluate PEGPH20 plus NAB plus GEM in stage IV patients with metastatic pancreatic cancer (NCT01839487).

Citation Format: Ryan J. Osgood, James F. Skipper, Jessica A. Cowell, Yanling Chen, Li Zhu, Michael E. Bledsoe, Susan J. Zimmerman, David W. Kang, H. Michael Shepard, Daniel C. Maneval, Curtis B. Thompson. Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances nab-paclitaxel plus gemcitabine efficacy in human pancreatic cancer xenografts. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B86.

Desmoplasia in Primary Tumors and Metastatic Lesions of Pancreatic Cancer

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is characterized by high levels of fibrosis, termed desmoplasia, which is thought to hamper the efficacy of therapeutics treating PDAC. Our primary focus was to evaluate differences in the extent of desmoplasia in primary tumors and metastatic lesions. As metastatic burden is a primary cause for mortality in PDAC, the extent of desmoplasia in metastases may help to determine whether desmoplasia targeting therapeutics will benefit patients with late-stage, metastatic disease.

EXPERIMENTAL DESIGN

We sought to assess desmoplasia in metastatic lesions of PDAC and compare it with that of primary tumors. Fifty-three patients' primaries and 57 patients' metastases were stained using IHC staining techniques.

RESULTS

We observed a significant negative correlation between patient survival and extracellular matrix deposition in primary tumors. Kaplan-Meier curves for collagen I showed median survival of 14.6 months in low collagen patients, and 6.4 months in high-level patients (log rank, P < 0.05). Low-level hyaluronan patients displayed median survival times of 24.3 months as compared with 9.3 months in high-level patients (log rank, P < 0.05). Our analysis also indicated that extracellular matrix components, such as collagen and hyaluronan, are found in high levels in both primary tumors and metastatic lesions. The difference in the level of desmoplasia between primary tumors and metastatic lesions was not statistically significant.

CONCLUSIONS

Our results suggest that both primary tumors and metastases of PDAC have highly fibrotic stroma. Thus, stromal targeting agents have the potential to benefit PDAC patients, even those with metastatic disease.

Tumor-associated hyaluronan limits efficacy of monoclonal antibody therapy

Despite tremendous progress in cancer immunotherapy for solid tumors, clinical success of monoclonal antibody (mAb) therapy is often limited by poorly understood mechanisms associated with the tumor microenvironment (TME). Accumulation of hyaluronan (HA), a major component of the TME, occurs in many solid tumor types, and is associated with poor prognosis and treatment resistance in multiple malignancies. In this study, we describe that a physical barrier associated with high levels of HA (HA(high)) in the TME restricts antibody and immune cell access to tumors, suggesting a novel mechanism of in vivo resistance to mAb therapy. We determined that approximately 60% of HER2(3+) primary breast tumors and approximately 40% of EGFR(+) head and neck squamous cell carcinomas are HA(high), and hypothesized that HA(high) tumors may be refractory to mAb therapy. We found that the pericellular matrix produced by HA(high) tumor cells inhibited both natural killer (NK) immune cell access to tumor cells and antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro. Depletion of HA by PEGPH20, a pegylated recombinant human PH20 hyaluronidase, resulted in increased NK cell access to HA(high) tumor cells, and greatly enhanced trastuzumab- or cetuximab-dependent ADCC in vitro. Furthermore, PEGPH20 treatment enhanced trastuzumab and NK cell access to HA(high) tumors, resulting in enhanced trastuzumab- and NK cell-mediated tumor growth inhibition in vivo. These results suggest that HA(high) matrix in vivo may form a barrier inhibiting access of both mAb and NK cells, and that PEGPH20 treatment in combination with anticancer mAbs may be an effective adjunctive therapy for HA(high) tumors.

Abstract 4844: Extracellular hyaluronan accumulation by hyaluronan synthase 3 promotes pancreatic cancer growth and modulates tumor microenvironment via epithelial-mesenchymal transition

Pancreatic cancer is one of most deadly cancers with a 5-year survival rate of 6%. Accumulation of hyaluronan (HA) is found in about 87% of human pancreatic adenocarcinomas, and removal of HA suppresses tumor growth in HA-rich preclinical models. In a transgenic pancreatic cancer mouse model (LSL-KrasG12D/+;LSLTrp53R172H/+;Pdx-1-Cre, KPC), removal of HA by pegylated human recombinant PH20 hyaluronidase (PEGPH20) inhibits tumor growth and increases survival in combination with gemcitabine compared to gemcitabine monotherapy. In this study, we explored the role of HA synthesizing (HAS) enzymes HAS2 and HAS3 and HA accumulation in pancreatic cancer tumor growth and remodeling of tumor microenvironment.

HAS2 and HAS3 were overexpressed in BxPC3 human pancreatic cancer cells using lentiviral vectors. Stable HAS2 and HAS3 overexpressing pancreatic cancer cell lines secreted more HA to culture medium and produced larger pericellular HA matrices than parental BxPC3 cells. In vivo, overexpression of HAS2 or HAS3 led to an increase in BxPC3 xenograft tumor growth (peritibial i.m. tumor model) compared to parental cells. Interestingly, overexpression of HAS3 was more effective to enhance tumor growth than overexpression of HAS2. In addition, massive accumulation of extracellular HA was found in HAS3 overexpressing tumors while HAS2 overexpressing tumors contained both extracellular and intracellular HA. Treatment with PEGPH20 removed the majority of extracellular HA and induced a 87% reduction of tumor volume in BxPC3 HAS3 model (p&lt;0.001) but had weaker effect on BxPC3 HAS2 (33%, p&lt;0.001) and BxPC3 tumors (36%, p&lt;0.01). Accumulation of extracellular HA was associated with enriched tumor stroma, loss of membranous E-cadherin and accumulation of cytoplasmic β-catenin in pancreatic cancer cells, suggesting HA-induced epithelial-mesenchymal transition (EMT). Removal of HA by PEGPH20 reversed the remodeling of the tumor stroma and induced translocation of E-cadherin and β-catenin to the plasma membrane.Translocation of E-cadherin was also observed in the KPC pancreatic tumors after PEGPH20 treatment.

In conclusion, accumulation of extracellular HA by HAS3 overexpression favors tumor growth and leads to a strong response to PEGPH20 in a pancreatic cancer xenograft model. Deposition of extracellular HA is associated with optimization of the tumor microenvironment and EMT. Depletion of HA by PEGPH20 reverses changes in the tumor stroma and induces translocation of epithelial markers to the plasma membrane.

Citation Format: Anne Kultti, Chunmei Zhao, Susan Zimmerman, Ryan J. Osgood, Yanling Chen, Rebecca Symons, Ping Jiang, Curtis B. Thompson, David A. Tuveson, Gregory I. Frost, H Michael Shepard, Zhongdong Huang. Extracellular hyaluronan accumulation by hyaluronan synthase 3 promotes pancreatic cancer growth and modulates tumor microenvironment via epithelial-mesenchymal transition. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4844. doi:10.1158/1538-7445.AM2014-4844

Characterization of a novel recombinant hyaluronan binding protein for tissue hyaluronan detection

Tumor necrosis factor-Stimulated Gene 6 protein (TSG-6) is a hyaluronan (HA)-binding glycoprotein containing an HA-binding Link module. Because of its well-defined structure, HA binding properties and small size, TSG-6 is an excellent candidate as an alternative to animal-derived HA-binding protein (HABP) for the detection of HA. The present work describes the generation and characterization of a novel recombinant HA-binding probe obtained by fusion of a modified TSG-6 Link module with mutationally inactivated heparin-binding sequence and the Fc portion of human IgG1 (TSG-6-ΔHep-Fc) for tissue HA detection in histological samples. Direct binding assays indicated strong binding of TSG-6-ΔHep-Fc to HA, with little residual binding to heparin. Histolocalization of HA in formalin-fixed, paraffin-embedded tissue sections using biotin-TSG-6-ΔHep-Fc resulted in hyaluronidase-sensitive staining patterns similar to those obtained with biotin-HABP, but with improved sensitivity. HA was detected in many human tissues, and was most abundant in soft connective tissues such as the skin dermis and the stroma of various glands. Digital image analysis revealed a linear correlation between biotin-HABP and biotin-TSG-6-ΔHep-Fc staining intensity in a subset of normal and malignant human tissues. These results demonstrate that TSG-6-ΔHep-Fc is a sensitive and specific probe for the detection of HA by histological methods.

Recombinant human hyaluronidase PH20 does not stimulate an acute inflammatory response and inhibits lipopolysaccharide-induced neutrophil recruitment in the air pouch model of inflammation

Hyaluronidase (Hyal) and low m.w. hyaluronan (LMW HA) fragments have been widely reported to stimulate the innate immune response. However, most hyaluronidases used were purified from animal tissues (e.g., bovine testis Hyal [BTH]), and contain endotoxin and other unrelated proteins. We tested a highly purified recombinant human Hyal (rHuPH20) and endotoxin-free HA fragments from M(r) 5,000 to 1,500,000 in the rodent air pouch model of inflammation to determine their potential for stimulation of the innate immune response. Exogenous LMW HA fragments (average M(r) 200,000) failed to induce either cytokine/chemokine production or neutrophil infiltration into the air pouch. Challenging the air pouch with LPS or BTH stimulated production of cytokines and chemokines but rHuPH20 did not, suggesting that neither PH20 nor generation of LMW HA fragments in situ stimulates cytokine and chemokine production. LPS and BTH also induced neutrophil infiltration into the air pouch, which was not observed with rHuPH20 treatment. Endotoxin-depleted BTH had much reduced proinflammatory activity, suggesting that the difference in inflammatory responses between rHuPH20 and BTH is likely due to endotoxin contaminants in BTH. When rHuPH20 was dosed with LPS, the induction of cytokines and chemokines was the same as LPS alone, but neutrophil infiltration was inhibited, likely by interrupting HA-CD44 interaction. Our results indicate that neither rHuPH20 nor its directly generated HA catabolites have inflammatory properties in the air pouch model, and rHuPH20 can instead inhibit some aspects of inflammation, such as neutrophil infiltration into the air pouch.

Abstract 3375: Phase 1 pharmacodyamic activity of multiple-dose PEGylated hyaluronidase PH20 (PEGPH20) in patients with solid tumors

Enzymatic degradation of hyaluronan (HA), a key component of the extracellular matrix (ECM), can enhance tumor perfusion, improve delivery of chemotherapeutics, and enhance the effects of anti-tumor agents. HA accumulation has been correlated with local invasion, the presence of distal metastasis, higher tumor grade, and poorer overall survival. PEGPH20, a pegylated form of recombinant human hyaluronidase PH20, is an investigational therapeutic agent under clinical development for the treatment of patients with solid tumors that may accumulate HA. Preclinical studies have demonstrated that sustained HA removal, accomplished with PEGPH20, inhibits tumor growth and enhances chemotherapeutic activity in HA-rich xenografts and genetically engineered mouse tumor models.

Twenty-six patients with advanced solid tumors were enrolled in a Phase 1 multi-center trial. Patients received weekly or twice weekly doses of IV PEGPH20 (0.5 - 5 μg/kg) for the first 4-week cycle, followed by once-weekly dosing for the subsequent 4-week cycles. Serial blood samples were drawn from each patient, and plasma concentrations were measured by an ultrasensitive hyaluronidase activity assay to assess PEGPH20 pharmacokinetics (PK). Plasma levels of HA catabolites were measured using a quantitative HPLC method to characterize PEGPH20 pharmacodynamics (PD). Other measures of PD activity were evaluated in selected patients, including DCE-MRI, DW-MRI, 18FDG-PET, textural analysis on CT, and histochemical staining of HA in tumor biopsies collected both before and after PEGPH20 treatment.

Peak plasma PEGPH20 concentrations increased with dose, and plasma pharmacokinetics (PK) were well described by a linear PK model. Pre-treatment plasma HA levels were typically &lt;1 μg/mL and increased in a dose-dependent fashion after PEGPH20 treatment. Increased plasma HA corresponded with decreased HA staining in patients with available tumor biopsies. DCE-MRI analysis indicated early (24-48 hr) and rapid increase in tumor perfusion compared to baseline in 4 patients with serial MRI assessments. Pharmacodynamic activity was also demonstrated when pre-treatment 18FDG-PET scans were compared with images collected at scheduled times after PEGPH20 dosing. Reduction in FDG uptake exceeding 25% was demonstrated in 3 of 4 patients after one cycle of treatment, consistent with a partial metabolic response.

These data are consistent with the mechanism of action reported in preclinical models, and results support continued evaluation of PEGPH20 in combination with anti-tumor agents via modification of the ECM.

Citation Format: Ping Jiang, Daniel C. Maneval, Ramesh K. Ramanathan, Jeffrey R. Infante, Mitesh Borad, Alberto Bessudo, Patricia LoRusso, Barry J. Sugarman, Deborah Carson, Marie A. Printz, Curtis B. Thompson, Paneer Selvam, Joy Zhu, Ronald Korn, H Michael Shepard, Gregory I. Frost. Phase 1 pharmacodyamic activity of multiple-dose PEGylated hyaluronidase PH20 (PEGPH20) in patients with solid tumors. [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 3375. doi:10.1158/1538-7445.AM2013-3375

Mutations in the catalytic domain of human matrix metalloproteinase-1 (MMP-1) that allow for regulated activity through the use of Ca2+

Conditionally active proteins regulated by a physiological parameter represent a potential new class of protein therapeutics. By systematically creating point mutations in the catalytic and linker domains of human MMP-1, we generated a protein library amenable to physiological parameter-based screening. Mutants screened for temperature-sensitive activity had mutations clustered at or near amino acids critical for metal binding. One mutant, GVSK (Gly(159) to Val, Ser(208) to Lys), contains mutations in regions of the catalytic domain involved in calcium and zinc binding. The in vitro activity of GVSK at 37 °C in high Ca(2+) (10 mm) was comparable with MMP-1 (wild type), but in low Ca(2+) (1 mm), there was an over 10-fold loss in activity despite having similar kinetic parameters. Activity decreased over 50% within 15 min and correlated with the degradation of the activated protein, suggesting that GVSK was unstable in low Ca(2+). Varying the concentration of Zn(2+) had no effect on GVSK activity in vitro. As compared with MMP-1, GVSK degraded soluble collagen I at the high but not the low Ca(2+) concentration. In vivo, MMP-1 and GVSK degraded collagen I when perfused in Zucker rat ventral skin and formed higher molecular weight complexes with α2-macroglobulin, an inhibitor of MMPs. In vitro and in vivo complex formation and subsequent enzyme inactivation occurred faster with GVSK, especially at the low Ca(2+) concentration. These data suggest that the activity of the human MMP-1 mutant GVSK can be regulated by Ca(2+) both in vitro and in vivo and may represent a novel approach to engineering matrix-remodeling enzymes for therapeutic applications.

Hyaluronan impairs vascular function and drug delivery in a mouse model of pancreatic cancer

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDA) is characterised by stromal desmoplasia and vascular dysfunction, which critically impair drug delivery. This study examines the role of an abundant extracellular matrix component, the megadalton glycosaminoglycan hyaluronan (HA), as a novel therapeutic target in PDA.

METHODS

Using a genetically engineered mouse model of PDA, the authors enzymatically depleted HA by a clinically formulated PEGylated human recombinant PH20 hyaluronidase (PEGPH20) and examined tumour perfusion, vascular permeability and drug delivery. The preclinical utility of PEGPH20 in combination with gemcitabine was assessed by short-term and survival studies.

RESULTS

PEGPH20 rapidly and sustainably depleted HA, inducing the re-expansion of PDA blood vessels and increasing the intratumoral delivery of two chemotherapeutic agents, doxorubicin and gemcitabine. Moreover, PEGPH20 triggered fenestrations and interendothelial junctional gaps in PDA tumour endothelia and promoted a tumour-specific increase in macromolecular permeability. Finally, combination therapy with PEGPH20 and gemcitabine led to inhibition of PDA tumour growth and prolonged survival over gemcitabine monotherapy, suggesting immediate clinical utility.

CONCLUSIONS

The authors demonstrate that HA impedes the intratumoral vasculature in PDA and propose that its enzymatic depletion be explored as a means to improve drug delivery and response in patients with pancreatic cancer.

Therapeutic targeting of hyaluronan in the tumor stroma

The tumor stroma, consisting of non-malignant cells and the extracellular matrix, undergoes significant quantitative and qualitative changes throughout malignant transformation and tumor progression. With increasing recognition of the role of the tumor microenvironment in disease progression, stromal components of the tumor have become attractive targets for therapeutic intervention. Stromal accumulation of the glycosaminoglycan hyaluronan occurs in many tumor types and is frequently associated with a negative disease prognosis. Hyaluronan interacts with other extracellular molecules as well as cellular receptors to form a complex interaction network influencing physicochemical properties, signal transduction, and biological behavior of cancer cells. In preclinical animal models, enzymatic removal of hyaluronan is associated with remodeling of the tumor stroma, reduction of tumor interstitial fluid pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy. This leads to inhibition of tumor growth and increased survival. Current evidence shows that abnormal accumulation of hyaluronan may be an important stromal target for cancer therapy. In this review we highlight the role of hyaluronan and hyaluronan-mediated interactions in cancer, and discuss historical and recent data on hyaluronidase-based therapies and the effect of hyaluronan removal on tumor growth.

Abstract B6: PEGPH20 depletion of pericellular hyaluronan sensitizes high hyaluronan-producing tumor cells in antibody-dependent cell-mediated cytotoxicity

Monoclonal antibodies (MAbs) have been developed successfully as part of the anticancer armamentarium. However, even in cases where the target of the antibody is stably and abundantly expressed, efficacy often falls below expectations. The tumor microenvironment (TME) has previously been shown to contribute to resistance to MAb therapy because matrix-associated high interstitial fluid pressure inhibits efficient drug penetration (1). Hyaluronan is an important component of the extracellular matrix (ECM) in about 25% of tumors, and 56% of breast cancers. This glycosaminoglycan is produced by malignant and stromal cells and acts to cross-link ECM proteins, contributing to the desmoplastic phenotype. Accumulation of HA has been associated with more aggressive malignancy (2).In this work, we show that &gt;50% of p185HER2-overexpressing breast tumors have a high accumulation of HA (HA+3). We hypothesized that tumor cells which overexpress HA create a protective “turtle shell” when it cross-links other ECM proteins (e.g., versican), and this pericellular structure protects the HER2-overexpressing tumor cell from attack by antibody-mediated cellular cytotoxicity (ADCC). SKBR3 (overexpressing p185HER2) and MDA-MB-231 (expressing EGFR) breast tumor cells were transfected with hyaluronan synthase 2 (HAS2), creating SKBR3/HAS2 (HA+3) and MDA-MB-231/HAS2 (HA+2), enabling these cells to form substantial pericellular matrices. NK-cell/trastuzumab/cetuximab-mediated ADCC is diminished in both of the HAS2-transfected cell types, suggesting that HA accumulation may contribute to tumor cell resistance to ADCC. Similarly, when these cells are treated in vitro with PEGPH20, a pegylated PH20 hyaluronidase (3), sensitivity to trastuzumab/cetuximab-mediated ADCC of the HAS2-overexpressing tumor cells is increased by up to 2-fold. These experiments show that the pericellular matrix coat (“turtle shell”) of high HA-producing tumor cells can inhibit the access of human immune cells to target cells, and that this effect can be reversed by depleting HA using PEGPH20. In vivo studies have shown that only PEGPH20, and not native PH20, has the bioavailability to induce antitumor activity in vivo. Models are currently in development to test whether PEGPH20 will enhance the activity of therapeutic MAbs in vivo.

Abstract 2672: Phase 1 pharmacokinetics (PK) & pharmacodynamics (PD) of PEGylated hyaluronidase PH20 (PEGPH20) in patients with solid tumors

Enzymatic degradation of hyaluronan (HA), a key component of the extracellular matrix (ECM), can enhance tumor perfusion, improve delivery of chemotherapeutics, and enhance the effects of anti-tumor agents. Recombinant human hyaluronidase (rHuPH20), used clinically to facilitate local dispersion and absorption after subcutaneous delivery, is rapidly cleared from the blood after intravenous (IV) injection. To prolong serum residence time, a pegylated form of rHuPH20 was manufactured and shown to have anti-tumor activities in preclinical models (Thompson et al., Mol Cancer Ther 2010). PEGPH20 is a novel agent in early clinical trials to evaluate the safety and biological activities of hyaluronidase-based therapy. Twenty-three patients enrolled in two Phase 1 trials received IV PEGPH20 (0.5 - 50 μg/kg). To assess PEGPH20 PK, serial blood samples were drawn from patients, and plasma concentrations were measured using an in vitro hyaluronidase activity assay (LLOQ 0.3 U/mL). Plasma levels of HA catabolites were measured using a quantitative HPLC method to characterize PD. After a single 50 μg/kg dose, the PEGPH20 PK profile was well described by a two-compartment open model with a low initial distribution volume (V1 ∼ 60 mL/kg) and a terminal half-life of ∼2 days. Observed Cmax and AUC0-8hr values increased with increasing dose, suggesting linearity within the dose range. Model simulations derived from single-dose PK parameters were predictive of plasma concentrations from patients who received twice weekly dosing. There was no evidence for accumulation of PEGPH20 in the plasma after multiple dosing. Systemic concentrations of HA catabolites were measured to assess the PEGPH20 PD. HA levels detected 24 hours post administration increased with increasing dose of PEGPH20. Observed Cmax and AUC0-168hr values were also dose-dependent. After a 50 μg/kg bolus, HA concentrations increased 100-fold above baseline and persisted for &gt;2 weeks. Repeat dosing with PEGPH20 resulted in sustained plasma concentrations of HA catabolites. Inter-patient variability in PD was notably greater than inter-patient variability in PK. Initial clinical PK/PD analysis indicates that systemic exposure after IV PEGPH20 is proportional to dose and is well described by a two-compartment PK model. Dose-dependent increases in HA catabolites provided a quantitative measure of PEGPH20 PD, consistent with the enzymatic activity of hyaluronidase. These data support continued evaluation of PEGPH20 to enhance delivery of anti-tumor agents via modification of the ECM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2672. doi:1538-7445.AM2012-2672

Abstract 3796: Pegylated human recombinant hyaluronidase PH20 reduces solid tumor hypoxia

Tumor hypoxia, the pathophysiological result of the structural and functional disruption of the tumor microcirculation and the deterioration of normal diffusion geometry, is strongly associated with tumor proliferation and resistance to therapy, both chemotherapy and radiotherapy. Indeed, hypoxia-associated resistance to photon radiotherapy is a severe clinical problem, as the radiation doses required to achieve the same treatment effect in hypoxic tumors can be three times the doses required in normoxic tumors. The extracellular matrix (ECM) glycosaminoglycan hyaluronan (HA) accumulates to high levels in ∼30% of solid tumors. Since HA is highly hydrophilic, ECM HA accumulation is believed to contribute to the elevated interstitial fluid pressure (IFP) and subsequent tumor vessel constriction observed in solid tumors. This vascular constriction contributes to the pathologic hypoxia present in these tumors. PEGPH20, a pegylated human recombinant hyaluronidase PH20, when delivered intravenously in preclinical models has been shown to enzymatically remove tumor HA and decrease both tumor IFP and water, leading to increased tumor vascular perfusion and enhanced chemotherapeutic delivery (Thompson 2010). Here we aimed to extend these observations and determine whether PEGPH20 would both increase tumor blood flow and reduce tumor hypoxia following PEGPH20-mediated HA removal. Nude mice were inoculated with human BxPC-3 pancreatic cancer cells adjacent to the right tibial periosteum. When tumors reached 15-20 mm in diameter (nα8/group), mice were staged into two treatment groups: (1) vehicle control and (2) PEGPH20 monotherapy. Vehicle or PEGPH20 (4.5 mg/kg) was administered to animals intravenously twice weekly for one week. The hypoxyprobe pimonidazole (60 mg/kg, ip) was administered to animals two hours prior to sacrifice, and fluorescent carbocyanine (75 μL, iv) 5 minutes prior to sacrifice. At sacrifice, whole tumors were removed, bisected, embedded in OCT medium, and processed for immunohistochemistry (hypoxyprobe and CD31) or simply imaged microscopically (carbocyanine). Hypoxia, blood vessel position, and tumor perfusion were assessed using pimonidazole, CD31 and carbocyanine, respectively. Compound images were created and the spatial relationship between hypoxia and vasculature perfusion evaluated. Consistent with prior studies, tumor HA was depleted in the PEGPH20-treated tumors. Further, tumor vascular perfusion (carbocyanine) increased 86% (p=0.0007) and tumor hypoxia decreased by 66% (p=0.03) in PEGPH20-treated animals, relative to the vehicle controls. These findings suggest that PEGPH20-mediated reduction in tumor HA increases tumor perfusion, while concomitantly reducing tumor hypoxia.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3796. doi:1538-7445.AM2012-3796

Abstract 5635: Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances Nab-Paclitaxel efficacy in BxPC-3 human pancreatic cancer xenografts

Hyaluronan (HA) accumulates in the extracellular matrix (ECM) of many solid tumors, including those of the prostate, colon, breast, stomach, ovary, and pancreas. This accumulation is associated with tumor progression and a negative clinical outcome. Accordingly, an HA-degrading enzyme, pegylated recombinant human hyaluronidase PH20 (PEGPH20), was developed to target tumor-associated HA in the ECM. Preclinical studies demonstrated that PEGPH20-mediated removal of HA from HA-rich xenograft tumors in mice decreased tumor interstitial fluid pressure and tumor water content resulting in a decompression of tumor vasculature, increased tumor vascular perfusion, tumor growth inhibition (TGI) and enhanced chemotherapeutic activity (Thompson 2010). We further characterized HA expression across multiple human tumor types and identified pancreatic ductal adenocarcinoma (PDA) as the cancer type with the most HA (∼87% express high levels). These observations coupled with a lack of curative therapy for PDA led us to evaluate alternative treatment strategies for PDA. Specifically, using the peritibial BxPC-3 human pancreatic cancer xenograft model, we investigated whether the antitumor activity of Nab-Paclitaxel was significantly enhanced with PEGPH20 treatment. Nude mice were inoculated with human PDA BxPC-3 cells adjacent to the right tibial periosteum, and tumor growth was monitored with ultrasonography. When tumors reached ∼400 mm3 (n≥8/group), mice were staged into 8 treatment groups: (1) vehicle control; (2) PEGPH20 monotherapy, 4.5 mg/kg; (3) Nab-Paclitaxel, 3 mg/kg; (4) Nab-Paclitaxel, 10 mg/kg; (5) Nab-Paclitaxel, 30 mg/kg; (6) Nab-Paclitaxel, 3 mg/kg, plus PEGPH20; (7) Nab-Paclitaxel, 10 mg/kg, plus PEGPH20; or (8) Nab-Paclitaxel, 30 mg/kg, plus PEGPH20. Vehicle or PEGPH20 ± Nab-Paclitaxel was administered intravenously starting on study day 0, and then dosed every third day for 15 days. At study termination, the average TGIs from animals treated with either PEGPH20 alone (12.2%), low dose (3 mg/kg) Nab-Paclitaxel (20.3%), or low dose Nab-Paclitaxel (3 mg/kg) plus PEGPH20 (25%) were not significantly different from vehicle-treated animals. However, Nab-Paclitaxel alone at both 10 mg/kg (61.5%, p&lt;0.01) and 30 mg/kg (73.6%, p&lt;0.01) inhibited tumor growth. High doses of Nab-Paclitaxel (30 mg/kg) ± PEGPH20 was associated with dose-related toxicity. The addition of PEGPH20 to the 10 mg/kg and 30 mg/kg Nab-Paclitaxel groups increased TGI to 71.7% (p&lt;0.01), and 90.8% (p&lt;0.01), respectively, relative to vehicle. These findings suggest that PEGPH20 significantly increases the anti-tumor efficacy of Nab-Paclitaxel in HA-rich PDA tumors at moderate to high Nab-Paclitaxel doses (10 and 30 mg/kg).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5635. doi:1538-7445.AM2012-5635

Effective targeting of the tumor microenvironment for cancer therapy

BACKGROUND

The tumor microenvironment is an emerging source of novel therapeutic targets in cancer. The glycosaminoglycan hyaluronan (HA) accumulates in 20-30% of tumors and is often associated with poor prognosis.

MATERIALS AND METHODS

We developed a digitized, semiquantitative scoring system for tumor-associated HA content, then grouped tumors (from animal models or patients) according to the degree of HA accumulation (HA+1,2,3). The antitumor response to HA-depletion by pegylated PH20 hyaluronidase (PEGPH20) was then characterized as a function of HA accumulation.

RESULTS

Semiquantitative grouping of tumors demonstrated that HA accumulation predicts the response of tumors in animal models to PEGPH20. Prospective analysis of HA content was used to predict response to PEGPH20 of squamous cell-type explants from patients with non-small cell lung cancer in nude mice.

CONCLUSION

Measurement of HA is a viable biomarker approach for predicting antitumor response in animal models to the HA-depleting agent, PEGPH20.

Human epidermal growth factor receptor bispecific ligand trap RB200: abrogation of collagen-induced arthritis in combination with tumour necrosis factor blockade

Introduction

Rheumatoid arthritis (RA) is a chronic disease associated with inflammation and destruction of bone and cartilage. Although inhibition of TNFα is widely used to treat RA, a significant number of patients do not respond to TNFα blockade, and therefore there is a compelling need to continue to identify alternative therapeutic strategies for treating chronic inflammatory diseases such as RA. The anti-epidermal growth factor (anti-EGF) receptor antibody trastuzumab has revolutionised the treatment of patients with EGF receptor-positive breast cancer. Expression of EGF ligands and receptors (known as HER) has also been documented in RA. The highly unique compound RB200 is a bispecific ligand trap that is composed of full-length extracellular domains of HER1 and HER3 EGF receptors. Because of its pan-HER specificity, RB200 inhibits responses mediated by HER1, HER2 and HER3 in vitro and in vivo. The objective of this study was to assess the effect of RB200 combined with TNF blockade in a murine collagen-induced arthritis (CIA) model of RA.

Methods

Arthritic mice were treated with RB200 alone or in combination with the TNF receptor fusion protein etanercept. We performed immunohistochemistry to assess CD31 and in vivo fluorescent imaging using anti-E-selectin antibody labelled with fluorescent dye to elucidate the effect of RB200 on the vasculature in CIA.

Results

RB200 significantly abrogated CIA by reducing paw swelling and clinical scores. Importantly, low-dose RB200 combined with a suboptimal dose of etanercept led to complete abrogation of arthritis. Moreover, the combination of RB200 with etanercept abrogated the intensity of the E-selectin-targeted signal to the level seen in control animals not immunised to CIA.

Conclusions

The human pan-EGF receptor bispecific ligand trap RB200, when combined with low-dose etanercept, abrogates CIA, suggesting that inhibition of events downstream of EGF receptor activation, in combination with TNFα inhibitors, may hold promise as a future therapy for patients with RA.

Abstract 3665: Enzymatic depletion of pericellular HA from tumor cell surface sensitizes Erbitux dependent immune cell-mediated cytotoxicity

Hyaluronan (HA), a ubiquitous high-molar-mass linear glycosaminoglycan (GAG) plays a critical role in cell adhesion, motility, growth and differentiation. HA accumulation is associated with many human cancers. Human tumor cells can form HA rich pericellular matrix which might favor tumor growth by preventing the access of host immune cells to malignant cells. Monoclonal antibody (MAb) based therapeutics are emerging as an important component of therapy for human malignancies. Despite the very high specificity of monoclonal antibodies, resistance to MAb therapy is common. Antibody Dependent Cell-mediated Cytotoxicity (ADCC) is an important effector for the clinical efficacy of MAbs and relies on effective interaction between the Fc domain of antigen bound antibody and FcγRIII positive immune cells. We hypothesize that pericellular HA coating may contribute to resistance of HA-rich malignant cells to MAb mediated therapy by preventing efficient access of effector cells to their tumor targets. Enzymatic depletion of HA with PEGPH20 hyaluronidase could potentially sensitize such tumors to MAb mediated therapy. remove ell surface and ated therapy by preventing tumor cells contact

EGFR positive breast carcinoma cell line MDA-MB-231luc and genetically engineered HAS2 over expressing MDA-MB-231HAS2 were used to investigate the role of HA-rich pericellular matrix in inhibition of ADCC. ADCC assay was performed by incubating Calcein AM labeled monolayer cells with monoclonal antibody (1h at 37°C) followed by co-incubation of recombinant human IL-2 (rhIL-2) activated human peripheral blood mononuclear cells (PBMC, 5h at 37°C, 5% CO2) with or without PEGPH20. Live cells from each treatment were assessed by fluorescence readings at Ex/Em 488nm/537nm (SpectraMax M2e plate reader) at the end of the assay. Percentages of cell killing were calculated against control. The student's t test was used to compare the difference between treatments.

Particle exclusion assay demonstrated that HAS2 over expressing MDA-MB-231HAS2 cells formed a pericellular coat that inhibited access of the rhIL-2 activated PBMC to tumor cells. Incubation with PEGPH20 removed the HA-rich pericellular matrix and promoted contact of PBMC to tumor cells. Incubation of Erbitux with rhIL-2 activated PBMC induced a dose dependent killing of both MDA-MB-231luc and MDA-MB-231HAS2 cells. PEGPH20 increased ADCC by 10% on MDA-MB-231luc (HAlow) and 25% on MDA-MB-231HAS2 (HAhigh) tumor cells. Our results show that the HA-rich pericellular matrix on adherent tumor cells inhibits ADCC and PEGPH20 depletion of this coat sensitizes the tumor cells to ADCC.

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 3665. doi:10.1158/1538-7445.AM2011-3665

Enzymatic depletion of tumor hyaluronan induces antitumor responses in preclinical animal models

Hyaluronan (HA) is a glycosaminoglycan polymer that often accumulates in malignancy. Megadalton complexes of HA with proteoglycans create a hydrated connective tissue matrix, which may play an important role in tumor stroma formation. Through its colloid osmotic effects, HA complexes contribute to tumor interstitial fluid pressure, limiting the effect of therapeutic molecules on malignant cells. The therapeutic potential of enzymatic remodeling of the tumor microenvironment through HA depletion was initially investigated using a recombinant human HA-degrading enzyme, rHuPH20, which removed HA-dependent tumor cell extracellular matrices in vitro. However, rHuPH20 showed a short serum half-life (t(1/2) < 3 minutes), making depletion of tumor HA in vivo impractical. A pegylated variant of rHuPH20, PEGPH20, was therefore evaluated. Pegylation improved serum half-life (t(1/2) = 10.3 hours), making it feasible to probe the effects of sustained HA depletion on tumor physiology. In high-HA prostate PC3 tumors, i.v. administration of PEGPH20 depleted tumor HA, decreased tumor interstitial fluid pressure by 84%, decreased water content by 7%, decompressed tumor vessels, and increased tumor vascular area >3-fold. Following repeat PEGPH20 administration, tumor growth was significantly inhibited (tumor growth inhibition, 70%). Furthermore, PEGPH20 enhanced both docetaxel and liposomal doxorubicin activity in PC3 tumors (P < 0.05) but did not significantly improve the activity of docetaxel in low-HA prostate DU145 tumors. The ability of PEGPH20 to enhance chemotherapy efficacy is likely due to increased drug perfusion combined with other tumor structural changes. These results support enzymatic remodeling of the tumor stroma with PEGPH20 to treat tumors characterized by the accumulation of HA.

Signal integration: a framework for understanding the efficacy of therapeutics targeting the human EGFR family

The human EGFR (HER) family is essential for communication between many epithelial cancer cell types and the tumor microenvironment. Therapeutics targeting the HER family have demonstrated clinical success in the treatment of diverse epithelial cancers. Here we propose that the success of HER family-targeted monoclonal antibodies in cancer results from their ability to interfere with HER family consolidation of signals initiated by a multitude of other receptor systems. Ligand/receptor systems that initiate these signals include cytokine receptors, chemokine receptors, TLRs, GPCRs, and integrins. We further extrapolate that improvements in cancer therapeutics targeting the HER family are likely to incorporate mechanisms that block or reverse stromal support of malignant progression by isolating the HER family from autocrine and stromal influences.

Antagonism of the human epidermal growth factor receptor family controls disease severity in murine collagen-induced arthritis

OBJECTIVE

To evaluate the therapeutic potential of the human epidermal growth factor receptor (HER) family inhibitor, herstatin, in an animal model of arthritis.

METHODS

Constructs of herstatin and modified tissue plasminogen activator (tPA)-herstatin were expressed in HEK 293T cells, and secreted protein was analyzed by Western blotting. Tissue PA-herstatin adenovirus (Ad-tPA-Her) was prepared, and titers established. Gene expression of Ad-tPA-Her was determined by polymerase chain reaction using HeLa cells. Pharmacokinetics of gene and protein expression in vivo in liver tissue and serum samples were confirmed via intravenous administration of Ad-tPA-Her. Clinical signs of disease were monitored in arthritic DBA/1 mice after therapeutic administration of Ad-tPA-Her, and histologic analysis of hind foot specimens was performed.

RESULTS

Native herstatin was not secreted in supernatants, while modified tPA-herstatin was detected in abundance. HeLa cells stably expressed the tPA-herstatin gene when infected with virus. Additionally, tPA-herstatin gene and protein expression was observed over time in mice treated with virus. Importantly, Ad-tPA-Her, when administered therapeutically to arthritic mice, controlled clinical and histologic signs of disease and reduced the number of joints with severe damage.

CONCLUSION

Our results support the notion that the human epidermal growth factor receptor family has a role in the progression of collagen-induced arthritis. The novel tPA-herstatin fusion protein could be used as an effective therapeutic tool for control of inflammatory disorders involving an angiogenic component.

Rational optimization of a bispecific ligand trap targeting EGF receptor family ligands

The human epidermal growth factor (EGF) receptor (HER) family members cooperate in malignancy. Of this family, HER2 does not bind growth factors and HER3 does not encode an active tyrosine kinase. This diversity creates difficulty in creating pan-specific therapeutic HER family inhibitors. We have identified single amino acid changes in epidermal growth factor receptor (EGFR) and HER3 which create high affinity sequestration of the cognate ligands, and may be used as receptor decoys to downregulate aberrant HER family activity. In silico modeling and high throughput mutagenesis were utilized to identify receptor mutants with very high ligand binding activity. A single mutation (T15S; EGFR subdomain I) enhanced affinity for EGF (two-fold), TGF-alpha (twenty-six-fold), and heparin-binding (HB)-EGF (six-fold). This indicates that T15 is an important, previously undescribed, negative regulatory amino acid for EGFR ligand binding. Another mutation (Y246A; HER 3 subdomain II) enhanced neuregulin (NRG)1-beta binding eight-fold, probably by interfering with subdomain II-IV interactions. Further work revealed that the HER3 subunit of an EGFR:HER3 heterodimer suppresses EGFR ligand binding. Optimization required reversing this suppression by mutation of the EGFR tether domain (G564A; subdomain IV). This mutation resulted in enhanced ligand binding (EGF, ten-fold; TGF-alpha, thirty-four-fold; HB-EGF, seventeen-fold; NRG1-beta, thirty-one-fold). This increased ligand binding was reflected in improved inhibition of in vitro tumor cell proliferation and tumor suppression in a human non-small cell lung cancer xenograft model. In conclusion, amino acid substitutions were identified in the EGFR and HER3 ECDs that enhance ligand affinity, potentially enabling a pan-specific therapeutic approach for downregulating the HER family in cancer.

Human epidermal growth factor receptor (HER-1:HER-3) Fc-mediated heterodimer has broad antiproliferative activity in vitro and in human tumor xenografts

All four members of the human epidermal growth factor (EGF) receptor (HER) family are implicated in human cancers. Although efficacious in a subset of patients, resistance to single-targeted anti-HER therapy [i.e., cetuximab (Erbitux) and trastuzumab (Herceptin)] is often associated with coexpression of other HER family members. This may be overcome by a HER ligand binding molecule that sequesters multiple EGF-like ligands, preventing ligand-dependent receptor activation. Toward this end, we have combined the HER-1/EGFR and HER-3 ligand binding domains, dimerized with fusion of an Fc fragment of human IgG1. This resulted in a mixture of HER-1/Fc homodimer (HFD100), HER-3/Fc homodimer (HFD300), and HER-1/Fc:HER-3/Fc heterodimer (RB200), also termed Hermodulins. The purified first-generation RB200 bound EGF and neuregulin 1 (NRG1)-beta1 ligands, determined by cross-linking and direct binding studies. The binding affinity for both was approximately 10 nmol/L by dissociation-enhanced lanthanide fluorescence immunoassay using europium (Eu)-labeled ligands. Competition studies with RB200 using Eu-EGF or Eu-NRG1-beta1 revealed that RB200 bound HER-1 ligands, including transforming growth factor-alpha and heparin-binding EGF, and HER-3 ligands NRG1-alpha and NRG1-beta3. RB200 inhibited EGF- and NRG1-beta1-stimulated tyrosine phosphorylation of HER family proteins, proliferation of a diverse range of tumor cells in monolayer cell growth assays, tumor cell proliferation as a single agent and in synergy with tyrosine kinase inhibitors, lysophosphatidic acid-stimulated cell proliferation, and tumor growth in two human tumor xenograft nude mouse models. Taken together, the data reveal that RB200 has the potential to sequester multiple HER ligands and interfere with signaling by HER-1, HER-2, and HER-3.

Novel splice variants derived from the receptor tyrosine kinase superfamily are potential therapeutics for rheumatoid arthritis

INTRODUCTION

Despite the advent of biological therapies for the treatment of rheumatoid arthritis, there is a compelling need to develop alternative therapeutic targets for nonresponders to existing treatments. Soluble receptors occur naturally in vivo, such as the splice variant of the cell surface receptor for vascular endothelial growth factor (VEGF)--a key regulator of angiogenesis in rheumatoid arthritis. Bioinformatics analyses predict that the majority of human genes undergo alternative splicing, generating proteins--many of which may have regulatory functions. The objective of the present study was to identify alternative splice variants (ASV) from cell surface receptor genes, and to determine whether the novel proteins encoded exert therapeutic activity in an in vivo model of arthritis.

METHODS

To identify novel splice variants, we performed RT-PCR using an mRNA pool representing major human tissue types and tumors. Novel ASV were identified by alignment of each cloned sequence to its respective genomic sequence in comparison with full-length transcripts. To test whether these ASV have biologic activity, we characterized a subset of them for ligand binding, and for efficacy in an animal model of arthritis. The in vivo study was accomplished using adenoviruses expressing secreted ASV.

RESULTS

We cloned 60 novel human ASV from 21 genes, encoding cell surface receptors--many of which are known to be important in the regulation of angiogenesis. The ASV were characterized by exon extension, intron retention and alternative exon utilization. Efficient expression and secretion of selected ASV--corresponding to VEGF receptor type 1, VEGF receptor type 2, VEGF receptor type 3, angiopoietin receptor Tie1, Met (receptor for hepatocyte growth factor), colony-stimulating factor 1 receptor, platelet-derived growth factor receptor beta, fibroblast growth factor receptor 1, Kit, and RAGE--was demonstrated, together with binding to their cognate ligands. Importantly, ASV derived from VEGF receptor type 1 and Tie1, and to a lesser extent from VEGF receptor type 2 and fibroblast growth factor receptor 1, reduced clinical signs of arthritis in vivo. The reduction was paralleled by decreased joint inflammation and destruction.

CONCLUSION

The present study shows that unique ASV derived from receptors that play key roles in angiogenesis--namely, VEGF receptor type 1 and, for the first time, Tie1--can markedly reduce arthritis severity. More broadly, our results demonstrate that ASV are a source of novel proteins with therapeutic potential in diseases in which angiogenesis and cellular hyperplasia play a central role, such as rheumatoid arthritis.