Risk Factors, Hyaluronidase Expression, and Clinical Immunogenicity of Recombinant Human Hyaluronidase PH20, an Enzyme Enabling Subcutaneous Drug Administration

Multiple FDA-approved and clinical-development stage therapeutics include recombinant human hyaluronidase PH20 (rHuPH20) to facilitate subcutaneous administration. As rHuPH20-reactive antibodies potentially interact with endogenous PH20, we investigated rHuPH20 immunogenicity risk through hyaluronidase tissue expression, predicted B cell epitopes, CD4+ T cell stimulation indices and related these to observed clinical immunogenicity profiles from 18 clinical studies. Endogenous hyaluronidase PH20 expression in humans/mice was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative RT-PCR, and deep RNA-Seq. rHuPH20 potential T cell epitopes were evaluated in silico and confirmed in vitro. Potential B cell epitopes were predicted for rHuPH20 sequence in silico, and binding of polyclonal antibodies from various species tested on a rHuPH20 peptide microarray. Clinical immunogenicity data were collected from 2643 subjects. From 57 human adult and fetal tissues previously screened by RT-PCR, 22 tissue types were analyzed by deep RNA-Seq. Hyaluronidase PH20 messenger RNA expression was detected in adult human testes. In silico analyses of the rHuPH20 sequence revealed nine T cell epitope clusters with immunogenic potential, one cluster was homologous to human leukocyte antigen. rHuPH20 induced T cell activation in 6-10% of peripheral blood mononuclear cell donors. Fifteen epitopes in the rHuPH20 sequence had the potential to cross-react with B cells. The cumulative treatment-induced incidence of anti-rHuPH20 antibodies across clinical studies was 8.8%. Hyaluronidase PH20 expression occurs primarily in adult testes. Low CD4+ T cell activation and B cell cross-reactivity by rHuPH20 suggest weak rHuPH20 immunogenicity potential. Restricted expression patterns of endogenous PH20 indicate low immunogenicity risk of subcutaneous rHuPH20.

A Phase I Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Recombinant Human Hyaluronidase PH20 Administered Intravenously in Healthy Volunteers

Background

Recombinant human hyaluronidase PH20 (rHuPH20) is used in subcutaneous formulations (eg, RITUXAN HYCELA [rituximab and hyaluronidase human], HERCEPTIN HYLECTA [trastuzumab and hyaluronidase-oysk], PHESGO [pertuzumab/trastuzumab/hyaluronidase-zzxf], and Darzalex FASPRO [daratumumab and hyaluronidase-fihj]) to increase the dispersion and absorption of coadministered therapeutics. Although unlikely, subcutaneous products that include rHuPH20 could be mistaken for the intravenous formulation of the corresponding drugs (eg, RITUXAN [rituximab], HERCEPTIN [trastuzumab], and DARZALEX [daratumumab]). To understand the potential effects of inadvertent intravenous injection of rHuPH20, we investigated the safety profile, pharmacokinetics (PK), and pharmacodynamics (PD) of rHuPH20 administered intravenously.

Objectives

This Phase I, open-label, single-center study in healthy volunteers was designed to assess the safety profile, tolerability, PK, and PD of rHuPH20 administered intravenously.

Methods

Healthy volunteers received 5 mL intravenous infusion of either 10,000 U (n = 12) or 30,000 U (n = 12) rHuPH20 over 5 minutes. Blood samples for PK and PD analysis were obtained at baseline and at various times after initiation of infusion. Adverse events and laboratory parameters were measured to assess the safety profile and tolerability of the intravenous infusion. The PK of rHuPH20 was assessed using both an enzymatic assay and a mass-based immunoassay, and plasma hyaluronan concentrations were measured as a PD marker using an HPLC–MS/MS disaccharide assay.

Results

All 24 volunteers (mean age = 36.5 years) completed the study, and no serious adverse events were reported in either treatment group. Overall, 2 adverse events (both Grade 1) were reported; catheter site pain in the 10,000 U group and hypotension in the 30,000 U group. Plasma concentrations of rHuPH20 increased during the 5-minute intravenous infusion (median t_max = 6 minutes from intravenous initiation) followed by a rapid plasma clearance (t_1/2 ∼10 minutes from intravenous initiation). Plasma hyaluronan concentrations increased with dose and time (t_max range = 45‒120 minutes from intravenous initiation) and returned to baseline within 1 week of administration. Changes in both PK and PD measurements appeared proportional to dose.

Conclusions

The study demonstrated that intravenous administration of up to 30,000 U rHuPH20 was well tolerated, rapidly cleared from the plasma, and did not appear to be associated with any serious adverse effects at doses used in subcutaneous therapeutic products. (Curr Ther Res Clin Exp. 2020; 81)

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.

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.

Clinical Immunogenicity of rHuPH20, a Hyaluronidase Enabling Subcutaneous Drug Administration

Recombinant human PH20 hyaluronidase (rHuPH20) is used to facilitate dispersion of subcutaneously delivered fluids and drugs. This report summarizes rHuPH20 immunogenicity findings from clinical trials where rHuPH20 was co-administered with SC human immunoglobulin, trastuzumab, rituximab, or insulin. Plasma samples were obtained from evaluable subjects participating in ten different clinical trials as well as from healthy plasma donors. A bridging immunoassay and a modified hyaluronidase activity assay were used to determine rHuPH20-reactive antibody titers and neutralizing antibodies, respectively. rHuPH20-binding antibody populations from selected subjects with positive titers were affinity-purified and subjected to further characterization such as cross-reactivity with endogenous PH20. Among individual trials, the prevalence of pre-existing rHuPH20-reactive antibodies varied between 3 and 12%, excepting the primary immunodeficiency (PID) studies. Incidence of treatment-induced rHuPH20 antibodies was 2 to 18%, with the highest titers (81,920) observed in PID. No neutralizing antibodies were observed. Within most trials, the kinetics of antibody responses were comparable between pre-existing and treatment-induced antibody responses, although responses classified as persistent were more common in subjects with pre-existing titers. There was no association between antibody positivity and either local or systemic adverse events. Pre-existing and treatment-induced antibody populations were of similar immunoglobulin isotypes and cross-reacted to endogenous PH20 to similar extents. No cross-reactivity to PH20 paralogs was detected. rHuPH20 induces only modest immunogenicity which has no association with adverse events. In addition, antibodies purified from baseline-positive individuals are qualitatively similar to those purified from individuals developing rHuPH20-reactive antibodies following exposure to the enzyme.

Tolerability and pharmacokinetic properties of ondansetron administered subcutaneously with recombinant human hyaluronidase in minipigs and healthy volunteers

BACKGROUND

Subcutaneous ondansetron facilitated by recombinant human hyaluronidase PH20 (rHuPH20) is an alternative for treating nausea/vomiting in patients who cannot receive ondansetron by other routes of administration.

OBJECTIVE

Based on preclinical results in minipigs, a Phase I study was designed to assess the tolerability and pharmacokinetic properties of subcutaneous ondansetron + rHuPH20 compared with intramuscular, intravenous, or oral ondansetron monotherapy in healthy volunteers.

METHODS

In a crossover design, 3 minipigs were dosed with subcutaneous ondansetron 0.08 mg/kg + rHuPH20, or as intramuscular or intravenous monotherapy, for the evaluation of plasma ondansetron concentrations and local tolerability. In a randomized, open-label, 4-way crossover study, subjects received a randomized sequence of SC ondansetron 4 mg + rHuPH20, or ondansetron monotherapy IM (4 mg), IV (4 mg), or PO (8 mg), over 4 daily visits. Study participants included healthy volunteers aged 19 to 65 years with adequate venous access in both upper extremities and no history of QT-interval prolongation. Primary tolerability end points (administration-site observations, systemic adverse events [AEs], and subject-assessed pain) were assessed, and pharmacokinetic parameters (AUC, Cmax, Tmax, t½) were computed to compare relative rate and extent of systemic exposure. Results were described using summary statistics, and bioequivalence was determined with a linear mixed-effects model.

RESULTS

In the preclinical study, no adverse events or significant local reactions were observed. The Cmax (45.8 ng/mL at 0.08 hour) with subcutaneous administration + rHuPH20 was 83% greater and was achieved 68% faster than with intramuscular administration (Cmax = 25 ng/mL at 0.25 hour). In the clinical study, a total of 12 subjects (7 women, 5 men; white majority; mean age, 44.8) were randomized. The majority of AEs were at the injection site, mild in severity, and transient. After subcutaneous administration of ondansetron + rHuPH20, geometric mean Cmax was 35% higher than with intramuscular ondansetron, 43% lower than with intravenous ondansetron, and 126% higher than with oral ondansetron (corrected for dose). Bioequivalence tests demonstrated that systemic exposure after subcutaneous administration was similar to that after intramuscular or intravenous administration and significantly greater than that after oral administration.

CONCLUSIONS

Subcutaneous ondansetron + rHuPH20 was generally well-tolerated. Subcutaneous dosing resulted in an extent of systemic exposure similar to that with intramuscular or intravenous dosing and greater than that with oral administration, and may be an option for clinical administration of ondansetron. ClinicalTrials.gov identifier: NCT01572012.

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 <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

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 >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

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.

Accelerated pharmacokinetics and glucodynamics of prandial insulins injected with recombinant human hyaluronidase

BACKGROUND

This phase 1 study investigated the pharmacokinetics (PK) and glucodynamics of insulin lispro (Humalog; Eli Lilly and Co., Indianapolis, IN) or regular human insulin (Humulin R; Eli Lilly and Co.) administered with or without (+/-) recombinant human hyaluronidase (rHuPH20).

METHODS

Healthy male volunteers (n = 26), 18-55 years old with body mass index 18-28 kg/m(2), weight >70 kg, and normal fasting glucose, were randomized to a crossover sequence of two subcutaneous injections, each followed by a 6-h euglycemic clamp targeting glucose 90-110 mg/dL: Cohort 1 received 20 U of Humalog +/- 300 U of rHuPH20 (11.3 microg/mL), whereas Cohort 2 received 20 U of Humulin R +/- 240 U of rHuPH20 (10 microg/mL). Pharmacokinetic parameters included peak serum insulin concentration (C(max)), time to C(max) (t(max)), and area under the curve (AUC) of serum concentration versus time. Glucodynamic parameters included time to maximal glucose infusion rate (tGIR(max)) and area under the GIR-versus-time curve (G).

RESULTS

For Humalog and Humulin R, respectively, rHuPH20 co-administration reduced t(max) by 51% (P = 0.0006) and 58% (P = 0.0002), increased C(max) by 90% (P = 0.0003) and 142% (P < 0.0001), increased early exposure (AUC(0-2h)) by 85% (P < 0.0001) and 211% (P < 0.0001), and reduced late exposure (AUC(4-6h)) by 41% (P < 0.0001) and 48% (P < 0.0001). Similarly, rHuPH20 reduced tGIR(max) by 41% (P = 0.006) and 35% (P = 0.01), increased early metabolism (G(0-2h)) by 52% (P = 0.001) and 127% (P < 0.0001), and reduced late metabolism (G(4-6h)) by 29% (P = 0.002) and 26% (P = 0.03) for Humalog and Humulin R, respectively. Injections were well tolerated.

CONCLUSIONS

Co-administration of rHuPH20 accelerated the PK and glucodynamics of both insulin formulations. Additional studies are necessary to evaluate the clinical relevance of these findings in patients with diabetes.

Tumor growth inhibition by interferon-alpha using PEGylated protein or adenovirus gene transfer with constitutive or regulated expression

Inducible synthesis and secretion of therapeutic proteins following gene transfer could be a viable strategy to deliver biopharmaceuticals that currently require parenteral administration. Evaluating the protein pharmacokinetics and biological responses generated by different delivery modalities will provide a better understanding of the advantages and disadvantages of each strategy. The interferon-alpha (IFN-alpha) family of proteins, used clinically for infectious and malignant diseases, has a short half-life, and IFN-alpha therapy requires frequent administration of the drug by injection. Subcutaneous xenograft tumors were inhibited by weekly administration of polyethylene glycol modified (PEGylated) IFN-alpha protein or by a single administration of an adenovirus constitutively expressing IFN-alpha (IACB). Both treatment modalities inhibited tumor growth in a dose-dependent manner, suggesting that increasing exposure to IFN-alpha could result in effective tumor control. A single adenovirus that encodes the components necessary for tetracycline induction (IADR) expressed IFN-alpha in a ligand-dependent manner. Adding doxycycline to the drinking water of mice treated intravenously with the inducible adenovirus IADR inhibited tumor growth by 85% compared with mice that were not given doxycycline. The correlation between serum IFN-alpha concentration and the degree of tumor growth inhibition did not depend on the delivery technology used. It is likely that it will be feasible to control expression of IFN-alpha by oral administration of small molecule drugs after gene delivery to induce therapeutic concentrations of proteins.

Interferon-alpha2b secretion by adenovirus-mediated gene delivery in rat, rabbit, and chimpanzee results in similar pharmacokinetic profiles

Gene delivery, with subsequent protein synthesis and secretion, in vivo has been proposed as an alternative way to deliver a therapeutic protein to the systemic circulation. Interferon-alpha (IFN) protein is effective in the treatment of viral and malignant diseases but has short serum half-life that requires frequent administration. An E1 region-deleted adenovirus vector encoding human IFN-alpha2b gene driven by the cytomegalovirus immediate early promoter (rAd-IFN) was generated to assess the serum concentration-time profiles of expressed IFN protein in animal models. Intravenous administration of rAd-IFN, normalized for body weight, resulted in dose-dependent serum IFN concentrations that persisted 8-40 days with similar concentration-time profiles in rats and rabbits. We sought to determine if serum concentration-time profiles in the rat and rabbit animal models would be predictive for a larger animal and would therefore be relevant models for potential dosing of human patients. Two chimpanzees (approximately 70 kg) dosed with rAd-IFN by intravenous administration normalized to body weight achieved serum IFN concentration-time profiles similar to those observed in rats and rabbits. The role of the immune response in limiting the persistence of transgene expression was highlighted by the persistence of serum IFN concentrations for over 200 days in beige/SCID immunodeficient mice. These studies suggest that serum concentration of secreted transgene products after gene delivery in small animal models may be highly predictive for larger species and will help define dosing strategies in human patients.

Interferon alpha2b gene delivery using adenoviral vector causes inhibition of tumor growth in xenograft models from a variety of cancers

A recombinant adenovirus expressing human interferon alpha2b driven by the cytomegalovirus promoter, IACB, was shown to produce and secrete biologically active protein in vitro and in vivo. Intravenous administration of IACB in Buffalo rats resulted in circulating levels of biologically active human interferon at 70,000 international units/mL for up to 15 days. Distribution of interferon protein after IACB administration was different from that seen with the subcutaneous delivery of interferon protein. Higher levels of interferon protein were observed in liver and spleen after IACB delivery compared to protein delivery. The antitumor efficacy of IACB, as measured by suppression of tumor growth, was tested in athymic nude mice bearing established human tumor xenografts from different types of human cancer. Subcutaneous tumors most responsive to the intratumoral administration of IACB ranked as U87MG (glioblastoma) and K562 (chronic myelogenous leukemia), followed by Hep 3B (hepatocellular carcinoma) and LN229 cells (glioblastoma). Intravenous administration of IACB in animals bearing U87MG or Hep 3B xenografts was also effective in suppressing tumor growth, although to a lesser extent than the intratumoral administration. IACB was also tested in a metastatic model in beige/SCID mice generated with H69 (small cell lung carcinoma) cells and was found to prolong survival in tumor-bearing animals. This suggested that interferon gene delivery can be effective in suppressing tumor growth in a wide variety of cells.

Enhanced apoptotic activity of a p53 variant in tumors resistant to wild-type p53 treatment

TP53 is the most commonly altered tumor-suppressor gene in cancer and is currently being tested in Phase II/III gene replacement trials. Many tumors contain wild-type TP53 sequence with elevated MDM2 protein levels, targeting p53 for degradation. These tumors are more refractory to treatment with exogenous wild-type p53. Here we generate a recombinant adenovirus expressing a p53 variant, rAd-p53 (d 13-19), that is deleted for the amino acid sequence necessary for MDM2 binding (amino acids 13-19). We compared the apoptotic activity of rAd-p53 (d 13-19) with that of a recombinant adenovirus expressing wild-type p53 (rAd-p53) in cell lines that differ in endogenous p53 status. rAd-p53 (d 13-19) caused higher levels of apoptosis in p53 wild-type tumor lines compared with wild-type p53 treatment, as measured by annexin V-FITC staining. In p53-altered tumor lines, rAd-p53 (d 13-19) showed apoptotic activity similar to that seen with wild-type p53 treatment. In normal cells, no increase in cytopathicity was detected with rAd-p53 (d 13-19) compared with wild-type p53 treatment. This variant protein displayed synergy with chemotherapeutic agents to inhibit proliferation of ovarian and breast cell lines. The p53 variant showed greater antitumor activity in an established p53 wild-type tumor compared with treatment with wild-type p53. The p53 variant represents a means of expanding TP53 gene therapy to tumors that are resistant to p53 treatment due to the cellular responses to wild-type p53.

Selective expression of nonsecreted interferon by an adenoviral vector confers antiproliferative and antiviral properties and causes reduction of tumor growth in nude mice

Replication-deficient adenoviruses expressing human interferon-alpha2b (HuIFN-alpha2b) or the hybrid IFN-alpha2alpha1 or those with the secretory signal deleted, whose express is driven by the alpha-fetoprotein (AFP) promoter, were constructed and characterized. Synthesis of IFN protein and secretion or intracellular retention were tested by Western blotting and immunoassay. Expression of IFN by the recombinant adenoviruses was restricted to cells that constitutively express AFP. In these cells, expression of both secreted and nonsecreted recombinant IFN resulted in inhibition of cell proliferation, resistance to viral infection, induction of major histocompatibility complex (MHC) class I expression, increased apoptosis, and activation of an IFN-stimulated response element (ISRE)-containing promoter. Also, the induction of protein kinase R (PKR), increased phosphorylation of Stat1, and accumulation of hypophosphorylated pRb were observed for both the secreted and nonsecreted IFN, suggesting that the nonsecreted IFN may act through a similar pathway. Hep3B cells, an AFP-positive line derived from a patient with hepatocellular carcinoma (HCC), were injected subcutaneously (s.c.) into athymic nude mice to generate established tumors. Intratumoral injection of recombinant adenoviruses expressing secreted as well as the nonsecreted IFN caused suppression of tumor growth. As the AFP promoter is activated in many HCC cells but is silent in normal cells, these constructs may be useful in restricting IFN effects to the tumor cells while reducing toxicity to the neighboring tissues.

In vivo tumor suppression by adenovirus-mediated interferon alpha2b gene delivery

A replication-deficient adenovirus encoding human interferon alpha2b, driven by the human cytomegalovirus (CMV) promoter, was constructed and characterized. This construct was used to infect human cells derived from different types of cancer. The production of protein and its secretion into the culture medium were tested by Western blotting and immunoassay. Inhibition of cell proliferation and antiviral activity, two of the most important biological activities of interferon, were observed with this construct. PC-3 cells, derived from human prostatic cancer, or Hep3B cells, derived from human hepatocellular carcinoma, were injected subcutaneously to generate and establish in vivo tumors in athymic nude mice. Intratumoral injection with the recombinant adenovirus expressing interferon alpha2b resulted in complete regression of tumor growth. Our results demonstrate that interferon gene delivery using recombinant adenoviral vectors may be a useful approach to treat a variety of cancers.

Analytical anion-exchange HPLC of recombinant type-5 adenoviral particles

The expanding use of adenoviral vectors for gene therapy has brought about the need for new analytical tools. We have developed an anion-exchange high-performance liquid chromatography method to analyze recombinant adenovirus serotype 5 samples. Before this assay, available analytical methods consisted of either long-term biological assays or required highly purified test articles. These methods were inadequate for optimizing adenovirus production and purification. This assay can quantitate viral particles in either crude lysates or highly pure samples. It can be used to assess particles in both dilute and concentrated samples over a wide dynamic range. Moreover, the population of viral particles eluted in the peak contains most of the infectious virions. This assay is a sensitive technique that overcomes the limitations of previous methods. It provides an essential tool to accomplish process optimization.

Purification of a type 5 recombinant adenovirus encoding human p53 by column chromatography

We have investigated the use of column chromatography for the purification of ACN53, a recombinant adenovirus type 5 encoding the human p53 tumor suppressor protein. Anion exchange, size exclusion, hydrophobic interaction, and metal chelating resins were tested; each was found to have distinct advantages and disadvantages. Based on these data, a rapid method was devised for the purification of ACN53. The resultant product was characterized and compared to cesium chloride density-gradient purified virus by SDS-PAGE, Western blot analysis, absorbance spectrum, total particle-to-infectious particle ratio, expression of p53 gene product in Saos-2 cells, growth inhibition of Saos-2 cells, and contamination by ATCC-293 host cell proteins. The results show that column chromatography offers an alternative to ultracentrifugation for the purification of recombinant adenoviruses for use in human gene therapy trials and other research applications.

Recombinant human transforming growth factor-beta 1: expression by Chinese hamster ovary cells, isolation, and characterization

A partial cDNA clone encoding the gene for human transforming growth factor-beta 1 (TGF-beta 1) was isolated from a human bladder carcinoma cell line (5637) cDNA library. Following restriction enzyme processing and ligation of synthetic oligonucleotide linkers, the gene was inserted into a plasmid and transfected into Chinese hamster ovary cells. Clonal selection and growth conditions resulted in a method for production of recombinant human TGF-beta 1 at 7 mg/liter in conditioned cell medium. Through a combination of low pH treatment, cation-exchange chromatography, and salt precipitation, the recombinant human TGF-beta 1 was purified in milligram amounts to > 95% purity in a yield of about 36%. Purification to homogeneity was accomplished by chromatography on C18 silica gel. Amino acid analysis, N-terminal sequencing, and growth inhibition assays indicate identity with the molecule from human platelets.

Synergistic induction of polypeptides by tumor necrosis factor and interferon-gamma in cells sensitive or resistant to tumor necrosis factor: assessment by computer based analysis of two-dimensional gels using the PDQUEST system

Tumor necrosis factor (TNF) synergistically enhanced the antiproliferative activity of interferon-gamma (IFN-gamma) in both TNF-sensitive and TNF-resistant variants of the cervical carcinoma line, ME-180. TNF alone had no apparent effect on the levels of synthesis of individual proteins in either of these variant cell lines as assessed by computerized two-dimensional gel analysis of cell lysates using the PDQUEST system. However, IFN-gamma enhanced the levels of 18 polypeptides and suppressed the levels of 10 polypeptides in both cell lines. When used in combination in both cell lines, TNF and IFN-gamma induced the synthesis of 10 polypeptides that were not induced by either agent alone. These synergistically induced polypeptides may be crucial to the mechanism of the synergistic antiproliferative action of TNF and IFN-gamma in ME-180 cells.

Modulation of the growth of transformed cells by human tumor necrosis factor-alpha and interferon-gamma

Recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) inhibited growth of the cervical carcinoma cell line, ME-180neo, at doses greater than 50 units/ml, but stimulated the growth of these cells at low doses (0.1-10 units/ml). ME-180neo variants selected for resistance to the cytotoxic effects of rHuTNF-alpha retained the ability to be growth stimulated at all concentrations tested. ME-180neo cells and the rHuTNF-alpha-resistant ME-180neo variants possessed equivalent steady state numbers of TNF-alpha receptors with similar Kd values. Recombinant human interferon-gamma (rHuIFN-gamma) augmented the rHuTNF-alpha-induced cytotoxic response of ME-180neo cells and overcame the resistance of the ME-180neo variants to rHuTNF-alpha cytotoxicity. In separate experiments we were able to show that the number of TNF-alpha binding sites on both rHuTNF-alpha-sensitive and -resistant ME-180neo cells was similar and was increased by treatment with rHuIFN-gamma. These results suggest that the growth stimulation of tumor cells mediated by rHuTNF-alpha can be dissociated from the cytotoxic response and that these responses are not related to the number or affinity of TNF-alpha binding sites.

Effects of growth factors on the antiproliferative activity of tumor necrosis factors

Tumor necrosis factors (TNFs) are a class of cytokines secreted by activated effector cells involved in host defense against tumor progression. Epidermal growth factor (EGF) and recombinant human transforming growth factor-alpha (rHuTGF-alpha) were shown to interfere with the in vitro antiproliferative effects of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) and -beta on a human cervical carcinoma cell line, ME-180. The inhibitory effect could be observed at EGF or rHuTGF-alpha concentrations of 100 pg/ml, and was maximal between 1 and 10 ng/ml. This response was not due to down regulation of the TNF receptor or to alteration of the affinity of TNF-alpha for its receptor. Since the antiproliferative effect of recombinant human interferon-gamma was not significantly affected by the presence of EGF or rHuTGF-alpha, the inhibition was specific for recombinant TNFs and was not due solely to enhanced proliferation induced by the growth factors. Neither growth factor had a substantial protective effect on the synergistic cytotoxicity observed when tumor cells were exposed simultaneously to rHuTNF-alpha and recombinant human interferon-gamma. TGF-beta can also interfere with the antiproliferative effects of rHuTNF-alpha in vitro. At concentrations of less than 1 ng/ml, TGF-beta significantly antagonized the cytotoxic effects of rHuTNF-alpha on NIH 3T3 fibroblasts. Since EGF, platelet-derived growth factor, and TGF-beta all enhanced NIH 3T3 cell proliferation, but only TGF-beta interfered with rHuTNF-alpha cytotoxicity, the protective effects of TGF-beta were not related in a simple manner to enhanced cell proliferation. rHuTGF-alpha and TGF-beta did not have a significant protective effect against rHuTNF-alpha-mediated cytotoxicity on two other tumor cell lines, BT-20 and L-929 cells. Based upon these observations we suggest that growth factors might enhance tumor growth in vivo by a combination of distinct mechanisms: (a) by autocrine stimulation tumor cell growth; and/or (b) by interfering with normal effector mechanisms of host defense.

Tumor necrosis factor: a potent effector molecule for tumor cell killing by activated macrophages

Activated macrophages (aM phi) destroy more effectively cancer cells than normal cells. The mechanism by which macrophages destroy cancer cells is not known. We report here that tumor cells susceptible to aM phi were killed by recombinant (r) tumor necrosis factor type alpha (TNF-alpha), whereas variant tumor cells resistant to aM phi after selection in vitro or in vivo were resistant to killing by rTNF-alpha. The converse selection for rTNF-alpha-resistant variants resulted in cells that were also resistant to killing by aM phi. The sensitivity of macrophage-resistant variants was not changed to other tumoricidal cells or soluble mediators, except that the macrophage-resistant variants were also resistant to the effects of another cytotoxic protein, B-cell lymphotoxin, which is structurally related to rTNF-alpha. Similar results were obtained regardless of whether short-term or long-term cytotoxic effects of aM phi were measured. Finally, it was shown that killing of tumor cells by murine aM phi was completely inhibited with a polyclonal antibody that neutralizes the effects of murine TNF-alpha. These results suggest a major role for TNF-alpha in tumor cell destruction by aM phi in vitro and in vivo.

Recombinant human tumor necrosis factor-alpha: effects on proliferation of normal and transformed cells in vitro

Modulation of the growth of human and murine cell lines in vitro by recombinant human tumor necrosis factor-alpha (rTNF-alpha) and recombinant human interferon-gamma (rIFN-gamma) was investigated. rTNF-alpha had cytostatic or cytolytic effects on only some tumor cell lines. When administered together with rIFN-gamma, rTNF-alpha showed enhanced antiproliferative effects on a subset of the cell lines tested. In contrast to its effects on sensitive tumor cells, rTNF-alpha augmented the growth of normal diploid fibroblasts. Variations in the proliferative response induced by rTNF-alpha were apparently not due to differences in either the number of binding sites per cell or their affinity for rTNF-alpha. These observations indicate that the effects of rTNF-alpha on cell growth are not limited to tumor cells, but rather that this protein may have a broad spectrum of activities in vivo.

Genomic organization, DNA sequence, and expression of chicken embryonic histone genes

We have isolated and characterized in detail 15 lambda Charon 4A recombinant bacteriophage containing histone genes from a chicken genomic library. Restriction enzyme-mapping analysis and Southern hybridization to sequenced, homologous histone probes indicate that these genes are not tandemly reiterated within the chicken genome; they usually reside in clusters even though there is no unique array of genes that appears to constitute a typical cluster. Chicken H4 and H1 genes were identified within the genomic recombinants and subsequently sequenced. Extensive regions of homology exist in the 5'- and 3'-flanking regions of the chicken H4 gene when compared to H4 genes from other organisms. In addition to the well documented histone-specific domains, two previously unreported regions of homology lie 5' to this gene: an octanucleotide and a pentanucleotide sequence lying 59 and 116 nucleotides upstream from the H4 gene CAP site, respectively. The H1 gene sequence predicts that the H1 polypeptide is 217 amino acids in length. The 5'-flanking domain of this gene contains, in addition to the transcriptional initiation site and the ATA box, two unusual sequences: one is a nonamer which resides 29 nucleotides upstream from the "ATA" box and is conserved in both the chicken and sea urchin H1 genes, while the other is a GC-rich repetitive sequence element. The majority of the chicken histone genes among the 15 unique lambda recombinant clones are expressed almost exclusively during in ovo development (i.e. from at least 4 days postfertilization up to hatching, about 20-21 days postfertilization) and appear not to be associated with any particular tissue type.

Chromosomal arrangement of the chicken beta-type globin genes

We have isolated the chicken beta-type globin genes from a library of chicken DNA--lambda Charon 4A recombinant bacteriophage. There are four beta-type genes within this segment of the genome; we believe this represents all of the beta-type genes of the chicken. The recombinant lambda C beta G1 contains the embryonic epsilon- and adult beta-globin genes. The hatching beta H- and embryonic rho-globin genes are found in the recombinant lambda C beta G2. Although lambda C beta G1 and lambda C beta G2 do not physically overlap, we present evidence that all four genes are closely linked and transcribed from the same DNA strand. These experiments demonstrate that the chromosomal regions represented by lambda C beta G1 and lambda C beta G2 lie approximately 1.6 kb apart in the chicken genome. A third recombinant lambda C beta G3 extends the genomic locus studied in the vicinity of the beta-type globin genes to approximately 39 kb. The physical order of the chicken beta-type globin genes within this segment of the chromosome is 5' ... rho--beta H--beta--epsilon ... 3'. This arrangement is unique among the vertebrate beta-type globin gene clusters thus far examined, in that embryonic genes are located at the 5' and 3' ends of the cluster while the hatching and adult genes occupy central positions.

Involvement of menaquinone in the active accumulation of aminoglycosides by Bacillus subtilis

Accumulation of aminoglycoside antibiotics by bacteria requires energy, and it appears that this must be derived from electron transport occurring within the cytoplasmic membrane. Dependence of aminoglycoside accumulation on cellular menaquinone content was examined using a menaquinone auxotroph of bacillus subtilis. This dependence manifested itself only when the menaquinone concentration was decreased to less than 10% of normal. The restricted aminoglycoside accumulation observed under these conditions was closely correlated with susceptibility to growth inhibition by the antibiotics. Evidence of saturation of the accumulation system was observed at low menaquinone concentrations, an effect not seen when menaquinone deficiency was relieved by supplying adequate shikimic acid (a menaquinone precursor) to the auxotroph. Lipophilic quinones may play two roles in aminoglycoside accumulation by bacteria: (i) as a binding site or part of a carrier complex: and (ii) as a crucial component of the electron transport system in maintaining the proton electrochemical gradient.