Delivery of interleukin 2 for immunotherapy

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

Microparticulate formulations for the controlled release of interleukin-2

Interleukin 2 (IL-2) is a pleotropic growth factor essential to immune system function. Current methods of administration are limited by the necessity of hospitalization as well as dose-limiting toxicities and side effects. There is also the issue of low therapeutic concentrations at the desired site of action; for instance, in the case of solid tumor treatment. Here we describe the design of controlled-release vehicles for the local administration of IL-2 based on single (SE) and double emulsion (DE) poly(lactic-co-glycolic acid) (PLGA) systems and a newly developed class of spray-dried lipid-protein-sugar systems composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC) and 0.2% Eudragit E 100. All three systems demonstrated the release of therapeutic drug quantities. Totals of 2.0, 0.5, and 2.8 microg of IL-2 (per mg of solid) were encapsulated in the SE, DE, and spray-dried formulations, respectively. The SE and DE released of 30 and 15% of the encapsulated protein, respectively, with delivery of biologically active IL-2 during the first 5 to 10 days. The lipid-protein-sugar-based system demonstrated extended sustained release of biologically active IL-2 for a period of 4 months. These systems provide a potential framework for long-term loco-regional immunotherapeutic treatment regimens.

Short- and long-term effects of interleukin-2 on weight, food intake, and hedonic mechanisms in the rat

In the present work, we investigated the short- and long-term effects of a single systemic injection of rat recombinant interleukin-2 on weight, food intake, and brain stimulation reward thresholds elicited from the ventral tegmental area. An inverted U-shaped dose-function was obtained with 0.5 microg producing the greatest increases in the threshold for rewarding brain stimulation which were sustained during the month long tests. No differences between groups in terms of maximum response rates, a measure of performance, were observed. Although all injected groups showed a minor decline in the rate of weight gain over time, percent efficiency of food utilization (percent weight gain/food intake) was the same across groups, suggesting that metabolic function was not affected by the cytokine. In animals with bilateral ventral tegmental area implants, there was no consistent correspondence between the threshold change obtained from ipsilateral stimulation and that associated with the contralateral site; side-to-side differences ranged from 0 to 100%, suggesting a specific interaction between cytokine activity and the locus of rewarding brain stimulation. These data suggest that peripheral IL-2 significantly modifies hedonic processes arising from medial forebrain bundle stimulation in a long-term manner. We further suggest that since this modulation appears to be notably site-specific, IL-2 receptors or its metabolites may not be evenly distributed within the medial forebrain bundle.

Formulation of liposomes associated with recombinant interleukin-2: effect on interleukin-2 activity

Association of the cytokine interleukin-2 (rIL-2) within liposomes could prolong its circulating half-life and thus reduce side-effects and improve its efficacy in cancer and AIDS treatment. The effects of physical procedures used in liposome preparation on the biological activity of rIL-2 were determined. While heating to 50 degrees C reduced the activity of IL-2 in the CTLL-2 proliferation assay by 50%, sonication, either bath or probe, was less detrimental. The combination of all three treatments resulted in only 10% loss of activity. Probe sonication led to the appearance of dimers which were stable under reducing conditions. Small unilamellar and large unilamellar liposomes were formed, respectively, by probe sonication or extrusion of multilamellar vesicles of dipalmitoylphosphatidylcholine hydrated in the presence of rIL-2. A high proportion of the rIL-2 was associated with the vesicles. However, the biological activity of the liposome-associated rIL-2 was reduced 7- to 10-fold compared with control rIL-2. rIL-2 dimers were formed on contact with lipid, even without sonication. We can conclude that the association of rIL-2 with lipid masks its access to its cell-surface receptor at least under cell culture conditions.

Interleukin-2-collagen chimeric protein which liberates interleukin-2 upon collagenolysis

Interleukin-2 (IL-2) is a potent activator of cellular immunity and has been utilized as an immunotherapeutic agent. We stably immobilized human IL-2 to collagen by covalently binding it to the N-terminus of human type III collagen (3A1) as IL2-3A1 chimeric protein using recombinant technology. The present study was aimed at liberating IL-2 from the immobilized chimeric protein by treating the chimera with bacterial collagenase. These IL2-3A1 chimeras were synthesized in insect cells which had been infected with baculovirus vectors carrying IL2-3A1 cDNA. The IL2-3A1 protein produced was shown to be in a pepsin-resistant triple helical structure and exhibited IL-2 activity to a similar extent as IL-2 itself. IL2-3A1 could be immobilized on the surface of plastic dishes by incubating it in the dishes. The IL-2 region of the immobilized IL2-3A1 was liberated to culture media by collagenase treatment and this freed IL-2 stimulated the growth of lined T cells. Thus, IL2-3A1 chimeric protein could be utilized as an IL-2 deliverer whose T cell mitogenic activity can be liberated by a collagenolytic environment.

Therapeutic efficacy of IL-2-loaded hydrogels in a mouse tumor model

Interleukin-2 (IL-2) is a highly effective anticancer drug if it is applied locally for 5 consecutive days. In most cases this requires 5 invasive treatments, which is not usually acceptable for either the patient or the clinician. For this reason we have developed dextran-based hydrogels from which the required amount of encapsulated IL-2 (1-4 x 10(6) IU of IL-2) is gradually released during 5-10 days. Initially IL-2-containing macroscopic cylinder-shaped gels (implants), and later IL-2-containing injectable microspheres, were developed. These preparations were characterized in vitro, and the therapeutic activity was tested in DBA/2 mice with SL2 lymphosarcoma. The therapy was given to mice with a large and extensively metastasized tumor load (at least 5% of the body weight). If 1-4 x 10(6) IU of IL-2 was slowly released from the hydrogels over a period of 5-10 days, the therapeutic effects were very good and comparable to the effects of free IL-2 injections for 5 consecutive days. In conclusion, dextran-based hydrogels are promising systems for the controlled release of IL-2.

Interleukin-2 liposomes for primary immune deficiency using the aerosol route

This is the first report of aerosol interleukin 2 (IL-2) liposome administration to individuals with immune deficiency. Parenteral IL-2 therapy has shown beneficial effects in some patients with cancer, common variable immunodeficiency (CVID), and human immunodeficiency virus (HIV) but is problematic because of side effects including fever and malaise as well as local swelling (delayed type hypersensitivity like reaction) after each subcutaneous IL-2 injection. Provision of an IL-2:human albumin liposome formulation via the aerosol route had few side effects in a recent clinical trial in cancer patients. Details of good manufacturing practice (GMP) synthesis and analysis of IL-2 liposomes (N= 6 lots) made without albumin carrier protein and placebo liposomes (three lots) are presented. After centrifugation, IL-2 was closely associated with the liposome pellet (99%). Mean diameter of liposomes was 1.1 microm. Patient acceptance, safety, toxicity, and immune effects of IL-2 liposomes were studied in individuals with primary immune deficiency (N = 15) and subsequently, a larger cohort of patients with hepatitis C. Experience in the immune deficient patients is the subject of this report. Placebo liposomes (12 weeks) and IL-2 liposomes (12 weeks) were provided using a nebulizer. Aerosol placebo liposomes and IL-2 liposomes were well tolerated. No changes in chest X-ray or pulmonary function were seen. Since biologic activity of aerosol IL-2 liposomes has been seen in viral disease (hepatitis C), additional studies of aerosol IL-2 liposomes in individuals with hepatitis C and HIV are planned.

Interleukin-2 liposome inhalation therapy is safe and effective for dogs with spontaneous pulmonary metastases

BACKGROUND

Systemic in vivo toxicity of interleukin-2 (IL-2) has been problematic. Antineoplastic activity of IL-2 has been modest. The authors have previously demonstrated the biologic activity and safety of aerosols of IL-2 liposomes in normal dogs. They now report objective regression of naturally occurring pulmonary metastases in dogs after 1 month of nebulized IL-2 liposome therapy.

METHODS

Dogs with pulmonary metastases (n = 7) and primary lung carcinoma (n = 2) were treated with aerosols of IL-2 liposomes. Response to therapy was monitored with serial chest radiographs. Effector populations, collected by bronchoalveolar lavage (BAL) and from heparinized whole blood, were assessed for cell type, immunophenotype, and tumor cytolytic activity. Immunogenicity of human IL-2 and human serum albumin (HSA) in dogs was assessed by immunofluorescence assay.

RESULTS

Two of four dogs with metastatic pulmonary osteosarcoma had complete regression of metastases; the regression remained stable for more than 12 and more than 20 months, respectively. One of two dogs with lung carcinoma had stabilization of disease for more than 8 months; the other had disease progression. Toxicity was minimal. BAL cell numbers increased more than fourfold (P = 0.01) and included significantly greater proportions and total numbers of eosinophils (P = 0.006) and lymphocytes (P = 0.008). Mean BAL effector lytic activity was significantly greater after 15 days of IL-2 liposome inhalation compared with pretreatment activity (P = 0.01); however, mean BAL lytic activity decreased after 30 days and was no longer significantly greater than pretreatment BAL lytic activity. No allergic reactions were associated with inhaled IL-2 liposome therapy. Canine antibodies against human IL-2 and HSA were detected in all dogs.

CONCLUSIONS

Pet dogs with naturally occurring pulmonary metastases and primary lung carcinomas accepted inhalation treatments easily. Nontoxic and effective treatment of pulmonary metastases of osteosarcoma is possible with nebulized IL-2 liposomes.

Controlled delivery of antigens and adjuvants in vaccine development

Advances in the understanding of the pathogenesis of infectious diseases and cancer immunology have inspired many new approaches to vaccine development. Many subunit antigens and peptides that are effective for vaccination have been discovered. These subunit antigens in tum stimulate synthesis of effective adjuvants to enhance their immunogenicity. Controlled-release technology offers the potential of further improving the efficacy of conventional vaccine formulations by optimizing the temporal and spatial presentation of the-antigens and adjuvants to the immune system. The combination of sustained release and depot effect may also reduce the amount of antigens or adjuvants needed and eliminate the booster shots that are necessary for the success of many vaccinations. This review examines the contribution controlled release technology can make in various areas of vaccination, with an emphasis on tumor vaccines.