Phase I trial of ImmTher, a new liposome-incorporated lipophilic disaccharide tripeptide

Muramyl dipeptide-based analogs as potential anticancer compounds: Strategies to improve selectivity, biocompatibility, and efficiency

According to the WHO, cancer is the second leading cause of death in the world. This is an important global problem and a major challenge for researchers who have been trying to find an effective anticancer therapy. A large number of newly discovered compounds do not exert selective cytotoxic activity against tumorigenic cells and have too many side effects. Therefore, research on muramyl dipeptide (MDP) analogs has attracted interest due to the urgency for finding more efficient and safe treatments for oncological patients. MDP is a ligand of the cytosolic nucleotide-binding oligomerization domain 2 receptor (NOD2). This molecule is basic structural unit that is responsible for the immune activity of peptidoglycans and exhibits many features that are important for modern medicine. NOD2 is a component of the innate immune system and represents a promising target for enhancing the innate immune response as well as the immune response against cancer cells. For this reason, MDP and its analogs have been widely used for many years not only in the treatment of immunodeficiency diseases but also as adjuvants to support improved vaccine delivery, including for cancer treatment. Unfortunately, in most cases, both the MDP molecule and its synthesized analogs prove to be too pyrogenic and cause serious side effects during their use, which consequently exclude them from direct clinical application. Therefore, intensive research is underway to find analogs of the MDP molecule that will have better biocompatibility and greater effectiveness as anticancer agents and for adjuvant therapy. In this paper, we review the MDP analogs discovered in the last 10 years that show promise for antitumor therapy. The first part of the paper compiles the achievements in the field of anticancer vaccine adjuvant research, which is followed by a description of MDP analogs that exhibit promising anticancer and antiproliferative activity and their structural changes compared to the original MDP molecule.

Therapeutic vaccines for colorectal cancer: The progress and future prospect

Cancer vaccines are usually derived from the patient's tumor cells or the antigens found on their surface, which may help the immune system to identify and kill these malignant cells. Current focus of many researches is designing vaccines with the hope of triggering the immune system to attack cancer cells in a more effective, reliable and safe manner. Although colorectal cancer (CRC) is recognized as the third leading cause of death by cancer, but significant advances in therapy strategies have been made in recent years, including cancer vaccine. In this review, we present various vaccine platforms that have been used in the border battle against CRC, some of which have been approved for clinical use and some are in late-stage clinical trials. Until September 2020 there is approximately 1940 clinical trials of cancer vaccines on patients with different cancer types, and also many more trials are in the planning stages, which makes it the most important period of therapeutic cancer vaccines studies in the history of the immunotherapy. In cancer vaccines clinical trials, there are several considerations that must be taken into account including engineering of antigen-presenting cells, potential toxicity of antigenic areas, pharmacokinetics and pharmacodynamics of vaccines, and monitoring of the patients' immune response. Therefore, the need to overcome immunosuppression mechanisms/immune tolerance is a critical step for the success of introducing therapeutic vaccines into the widely used drugs on market. In this way, better understanding of neoantigens, tumor immune surveillance escape mechanisms and host-tumor interactions are required to develop more effective and safe cancer vaccines.

Translation of peptidoglycan metabolites into immunotherapeutics

The discovery of defined peptidoglycan metabolites that activate host immunity and their specific receptors has revealed fundamental insights into host-microbe recognition and afforded new opportunities for therapeutic development against infection and cancer. In this review, we summarise the discovery of two key peptidoglycan metabolites, γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP) and muramyl dipeptide and their respective receptors, Nod1 and Nod2, and review progress towards translating these findings into therapeutic agents. Notably, synthetic derivatives of peptidoglycan metabolites have already yielded approved drugs for chemotherapy-induced leukopenia and paediatric osteosarcoma; however, the broad effects of peptidoglycan metabolites on host immunity suggest additional translational opportunities for new therapeutics towards other cancers, microbial infections and inflammatory diseases.

Harnessing the untapped potential of nucleotide-binding oligomerization domain ligands for cancer immunotherapy

In the last decade, cancer immunotherapy has emerged as an effective alternative to traditional therapies such as chemotherapy and radiation. In contrast to the latter, cancer immunotherapy has the potential to distinguish between cancer and healthy cells, and thus to avoid severe and intolerable side‐effects, since the cancer cells are effectively eliminated by stimulated immune cells. The cytosolic nucleotide‐binding oligomerization domains 1 and 2 receptors (NOD1 and NOD2) are important components of the innate immune system and constitute interesting targets in terms of strengthening the immune response against cancer cells. Many NOD ligands have been synthesized, in particular NOD2 agonists that exhibit favorable immunostimulatory and anticancer activity. Among them, mifamurtide has already been approved in Europe by the European Medicine Agency for treating patients with osteosarcoma in combination with chemotherapy after complete surgical removal of the primary tumor. This review is focused on NOD receptors as promising targets in cancer immunotherapy as well as summarizing current knowledge of the various NOD ligands exhibiting antitumor and even antimetastatic activity in vitro and in vivo.

Vaccine Adjuvant Nanotechnologies. Micro and Nanotechnology in Vaccine Development. Elsevier; 2017. pp. 127-47. [DOI: 10.1016/b978-0-323-39981-4.00007-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The increasing sophistication of vaccine adjuvant design has been driven by improved understanding of the importance of nanoscale features of adjuvants to their immunological function. Newly available advanced nanomanufacturing techniques now allow very precise control of adjuvant particle size, shape, texture, and surface chemistry. Novel adjuvant concepts include self-assembling particles and targeted immune delivery. These individual concepts can be combined to create a single integrated vaccine nanoparticle-combining antigen, adjuvants, and DC-targeting elements. In the process, the concept of an adjuvant has broadened to include not only immune-stimulatory substances but also any design features that enhance the immune response against the relevant vaccine antigen. The modern definition of an adjuvant includes not only classical immune stimulators but also any aspects of particle size, shape, and surface chemistry that enhance vaccine immunogenicity. It even includes purely physical processes such as texturing of particle surfaces to maximize immunogenicity. Looking forward, adjuvants will increasingly be seen not as separate add-on items but as wholly integrated elements of a complete vaccine delivery package. Hence, vaccine systems will increasingly approach the complexity and sophistication of pathogens themselves, incorporating highly specific particle properties, contents, and behaviors, all designed to maximize immune system recognition and drive the immune response in the specific direction that affords maximal protection.

Carbohydrate-based immune adjuvants

The role for adjuvants in human vaccines has been a matter of vigorous scientific debate, with the field hindered by the fact that for over 80 years, aluminum salts were the only adjuvants approved for human use. To this day, alum-based adjuvants, alone or combined with additional immune activators, remain the only adjuvants approved for use in the USA. This situation has not been helped by the fact that the mechanism of action of most adjuvants has been poorly understood. A relative lack of resources and funding for adjuvant development has only helped to maintain alum's relative monopoly. To seriously challenge alum's supremacy a new adjuvant has many major hurdles to overcome, not least being alum's simplicity, tolerability, safety record and minimal cost. Carbohydrate structures play critical roles in immune system function and carbohydrates also have the virtue of a strong safety and tolerability record. A number of carbohydrate compounds from plant, bacterial, yeast and synthetic sources have emerged as promising vaccine adjuvant candidates. Carbohydrates are readily biodegradable and therefore unlikely to cause problems of long-term tissue deposits seen with alum adjuvants. Above all, the Holy Grail of human adjuvant development is to identify a compound that combines potent vaccine enhancement with maximum tolerability and safety. This has proved to be a tough challenge for many adjuvant contenders. Nevertheless, carbohydrate-based compounds have many favorable properties that could place them in a unique position to challenge alum's monopoly over human vaccine usage.

Chemotherapy response is an important predictor of local recurrence in Ewing sarcoma

BACKGROUND

Local recurrence in Ewing sarcoma is associated with a poor prognosis. The purpose of the study was to determine the factors that predict local recurrence after surgical treatment of the primary tumor.

METHODS

Between 1990 and 2001, 64 patients underwent surgical resection of Ewing sarcoma. Surgical margins were assessed histologically and radiologically. Response to preoperative chemotherapy was determined by detailed specimen mapping. Local recurrence-free survival (LRFS) was calculated by Kaplan-Meier analysis. Multivariate analysis was performed with the Cox proportional hazards model.

RESULTS

A number of factors were found to be associated with local recurrence on univariate analysis. Patients with a good response to chemotherapy (> or = 90% tumor necrosis), had superior LRFS at 5 years (86% vs 51%, P = .015). Central site of disease was associated with an increased rate of recurrence. The LRFS at 5 years was 50% for the chest wall, 74% for pelvic/scapular, and 86% for extremity tumors (P = .083). Positive surgical margin was not a strong predictor of recurrence (P = .72). A critical analysis of minimal surgical margin based on preoperative magnetic resonance imaging (MRI) and computed tomography (CT) scans also failed to reveal an association between margin and local recurrence. In multivariate analysis, the 2 independent predictors of local recurrence were histological response to chemotherapy and central site of disease.

CONCLUSION

Local recurrence after surgical resection is a complex phenomenon. An important predictive factor is the response to chemotherapy. In the current study, this seems to have the largest impact. Central site of disease may be a second independent predictive factor.

Early lymphocyte recovery as a prognostic indicator for high-risk Ewing sarcoma

BACKGROUND

Increasing evidence suggests that lymphocyte recovery plays a major part in tumor control. Facilitating immune reconstitution might be a novel direction of cancer therapy. The purpose of this study was to determine if early lymphocyte recovery is an independent prognostic indicator for high-risk Ewing sarcoma outcome.

RESULTS

Data of 24 Ewing sarcoma patients were analyzed (age, 3 to 50 y; median, 16.5; male to female, 16:8). The 5-year overall survival (OS) of the total population was 47.9% [10.6 standard error (SE)]. Patients were separated into 2 groups: prolonged lymphopenia versus early lymphocyte recovery, using a threshold absolute lymphocyte count (ALC) of > or =500 cells/microL on day 15. The majority (67%; n=16) of the patients had an ALC > or =500 cells/microL, and of these 10/16 are alive with a 5-year OS of 58.7% (13.2 SE). In contrast, 33% (n=8) of patients had an ALC <500 cells/microL on day 15 and only 2/8 are alive with a 5-year OS of 25% (15.3 SE). This difference was significant (P=0.007 using the log rank test). When comparing patients with metastatic disease, patients with an ALC-15 < 500 cells/microL had a median survival of 13 months, whereas patients with an ALC-15 > or =500 cells/microL had a median survival of 29.5 months. All patients had an ALC before chemotherapy of >1000 cells/microL. The difference was significant (P value=0.001 using the log rank test). Univariate analysis of platelet counts, age, sex, and absolute neutrophil count showed no statistically significant association with OS.

CONCLUSIONS

The data demonstrate that an ALC > or =500 cells/microL on day 15 of the first course of chemotherapy is an independent prognostic factor associated with superior OS in high-risk Ewing sarcoma.

The choroidal circulation assessed by laser-targeted angiography

The choroid plays an important role in supplying nutrients to and removing waste products from the outer region of the retina. Abnormal choroidal blood flow can disrupt normal retinal function and lead to alterations in visual function. Visualization of the choriocapillaris in vivo is a great challenge to understanding its normal physiology and involvement in the disease process. Laser-targeted angiography (LTA) is a relatively new method used to visualize and analyze the choroidal circulation. Carboxyfluorescein (CF), encapsulated in heat-sensitive liposomes, is released locally in the choroid through the application of a heat beam provided by an infrared laser. Video angiograms are generated with excitation illumination provided by an argon laser. Obtained images are highly selective to the choriocapillaris and are sharply contrasted against underlying and overlying structures. The images can be obtained repetitively, during which period the circulating liposome concentration is sufficient to generate adequate angiograms. These high-quality images have revealed three distinct phases (filling, plateau, and draining) of the choriocapillaris. In the plateau phase, a cluster of lobules fed by a common arteriole has been uniformly illuminated. This defined cluster area does not change in size while an infrared laser is continuously applied to the same spot, which demonstrates that each cluster is functionally independent and no physiological communication exists between them. Only in posterior regions do the angiograms demonstrate during the filling and draining phases that each lobule is filled from a central spot and drained along a peripheral ring, showing honeycomb flow patterns. The regional differences in choriocapillaris flow patterns revealed by LTA suggests that the choriocapillaris provides a more highly efficient system of outflow in posterior regions than in peripheral regions. LTA is useful in analyzing choroidal circulation in vivo and has the potential for clinical application in the future. Additionally, LTA has a unique capability to image choroidal neovascularization in animal models and it promises potential application in age-related macular degeneration (AMD).

Developments in liposomal drug delivery systems

Liposomes are the leading drug delivery systems for the systemic (iv.) administration of drugs. There are now liposomal formulations of conventional drugs that have received clinical approval and many others in clinical trials that bring benefits of reduced toxicity and enhanced efficacy for the treatment of cancer and other life-threatening diseases. The mechanisms giving rise to the therapeutic advantages of liposomes, such as the ability of long-circulating liposomes to preferentially accumulate at disease sites including tumours, sites of infection and sites of inflammation are increasingly well understood. Further, liposome-based formulations of genetic drugs such as antisense oligonucleotides and plasmids for gene therapy that have clear potential for systemic utility are increasingly available. This paper reviews the liposomal drug delivery field, summarises the success of liposomes for the delivery of small molecules and indicates how this success is being built on to design effective carriers for genetic drugs.

The muramyl dipeptide analog GMTP-N-DPG preferentially induces cellular immunity to soluble antigens

GMTP-N-DPG (N-acetylglucosaminyl-N-acetylmuramyl-L-alanyl-D-isoglutamyl- L-alanyl-dipalmitoylpropylamide) is a lipophilic derivative of the immunologically active compound MDP and has adjuvant properties. GMTP-N-DPG was compared with other adjuvants in model vaccine systems using ovalbumin (OVA) and a synthetic peptide derived from pp89 of murine cytomegalovirus as antigens. When serum from C57/Bl mice immunized with OVA was tested for the presence of anti-OVA antibody, samples from mice immunized with OVA plus GMTP-N-DPG had ELISA optical density (O.D.) readings twice as high as those from mice immunized with antigen alone. In contrast, samples from mice immunized with the liposomal monophosphoryl lipid A (MPL) formulation exhibited ELISA O.D. readings tenfold higher than samples from mice immunized with antigen alone. Relative levels of specific antibody in serum samples from mice immunized with OVA plus the saponin adjuvant QS-21 were equal to the GMTP-N-DPG samples. When spleen cells from immunized mice were tested for their proliferative response to OVA, we found that liposomal MPL was again the optimal adjuvant, whereas the proliferative responses of cells from mice immunized with GMTP-N-DPG or QS-21 were no better than cells from mice immunized with OVA alone. In contrast to the relatively low antibody and proliferation levels, spleen cells from mice immunized with GMTP-N-DPG and OVA demonstrated the highest level of anti-OVA CTL activity. Spleen cells from mice immunized with the pp89 peptide plus GMTP-N-DPG also exhibited CTL activity. Using antibody and complement mediated cytotoxicity it was determined that the CTL were CD8+. Based on these results, we believe that GMTP-N-DPG may be an excellent candidate adjuvant in vaccines for diseases in which a strong cell-mediated response is desired.

Feasibility of laser targeted photo-occlusion of ocular vessels

AIMS/BACKGROUND

Neovascularisation occurs in many major ocular diseases such as diabetes, age-related macular degeneration, and sickle cell disease. Laser photocoagulation is typically used to obliterate the vessels but it also causes severe damage to adjacent normal tissues. This is a very significant limitation especially in the treatment of choroidal neovascularisation which often covers large areas of the posterior pole and the fovea. A method, laser targeted delivery, has been developed capable of releasing drugs locally and non-invasively in the choroidal or retinal vasculature. This method could be used to target a photo-sensitiser to neovascular membranes and cause their selective occlusion by irradiating them. The targeting properties of the method promise to yield a treatment for neovascularisation that does not damage adjacent tissues and thus preserves vision. The purpose of the present study was to test the feasibility of occluding ocular vessels with this method.

METHOD

The iris vessels of the albino rat were chosen because the treatment could be assessed unequivocally and followed with time. Aluminium phthalocyanine tetrasulphonate was encapsulated in heat sensitive liposomes and administered systemically. The iris vessels were irradiated with a yellow laser to raise their temperature to 41 degrees C, cause a phase transition in the liposomes and thereby locally release the photosensitiser. The laser was also used to excite the released photosensitiser and cause occlusion. The effect was monitored immediately and for 8 months thereafter. Controls for the effect of the laser and the unencapsulated drug were conducted.

RESULTS

The results demonstrated that occlusion can be achieved and sustained for the period of follow up. The controls showed that the effect was not due to heat or to the activation of the low dose of free drug.

CONCLUSION

These preliminary findings indicate that laser targeted photo-occlusion is a promising new method for the treatment of neovascularisation.

Systemic toxicology and laser safety of laser targeted angiography with heat sensitive liposomes

Angiography is currently limited by its lack of local and tissue specificity. The dye rapidly fills both the retinal and choroidal vessels and leaks out of the vessels thus hampering visualization of small vascular beds such as occult choroidal neovascularization. We have developed a method of laser targeted delivery based on encapsulating the dye in heat sensitive liposomes, administering the liposomes intravenously and causing them to release their content by noninvasively warming the target tissue with a laser pulse delivered through the pupil. The local release yields a bright fluorescent bolus which selectively highlights retinal or choroidal vessels. A preliminary investigation of the potential side effects of the method is presented. In rats the systemic toxicity of carboxyfluorescein-entrapped liposomes was compared with that of the free dye. No significant difference was found between the two. Non-human primates exposed to repeated laser targeted angiography were monitored over time and no significant side effects were observed. The safety of the laser exposures was assessed by conventional fluorescein angiography and histopathology. Choroidal laser targeted angiography was achieved without damage. Retinal laser targeted angiography was accompanied by mild and local damage in an area remote from the fovea. The study indicates that laser targeted choroidal angiography can be performed safely and holds promise for diseases such as age related macular degeneration with occult choroidal neovascularization. Further improvements are needed to ensure that no side effects accompany retinal laser targeted angiography.

Combination therapy with a synthetic peptide of C-reactive protein and interleukin 2: augmented survival and eradication of pulmonary metastases

A synthetic peptide (RS-83277) derived from the structure of human C-reactive protein (CRP) was previously shown to have antitumor activity in three different murine tumor models when administered in multilamellar vesicles (MLV). The therapeutic effects were comparable to those seen with MLV-encapsulated native CRP. The present study evaluated the therapeutic and immunomodulatory effects of administering CRP peptide RS-83277 MLV simultaneously with low-dose recombinant interleukin-2 (IL-2) to C57Bl/6 mice bearing established pulmonary metastases of fibrosarcoma T241. Results demonstrated that the capacity of RS-83277 MLV to inhibit tumor metastases and prolong survival was significantly augmented by combination with 10,000 U/day IL-2 i.p. Treated animals showed no evidence of toxicity. By immunohistochemistry, increased Thy 1.2+ cells were detectable in lungs of RS-83277 MLV/IL-2-treated animals compared to those receiving RS-83277 MLV alone. Circulating tumor necrosis factor alpha (TNF) and interferon (IFN) were not detectable in animals receiving RS-83277 MLV alone, but TNF was significantly elevated in animals receiving IL-2. In the presence of combination therapy, however, circulating TNF was not detectable. Results suggest that the combination of synthetic CRP peptide RS-83277 MLV and low-dose IL-2 offers a therapeutic advantage over either agent alone.

Interaction of phospholipids with proteins and peptides. New advances III

1. The review deals with the recent achievements in the study of the various interactions of phospholipids with proteins and peptides. 2. The interactions are classified according to the hydrophobic, hydrophilic or mixed character of the interactive forces. 3. The effect of the interaction on the structure and biological activity of the interacting molecules is also discussed.

Liposomes in the treatment of malignancy: a clinical perspective

Technological advances in liposomal preparation and efficient drug entrapment, along with supportive preclinical studies, have led to a number of recent clinical trials utilizing liposomes as drug carriers in the treatment of human malignancy. Although the results of these trials must be considered preliminary, it is clear that liposomal delivery of chemotherapeutic agents is safe at the doses administered. Aside from minor constitutional symptoms, virtually all toxicity could be attributed to release of the incorporated drug. Myelosuppression tends to be the dose-limiting toxicity with free drug, whereas constitutional symptoms are more likely to occur with encapsulated biologic therapy. Prior to human trials, there was fear that intravenous injection of liposomes could result in pulmonary emboli. No cases of pulmonary embolism secondary to liposome therapy have been recorded. The objective response rate in the patients studied appears to be minimal. This is not surprising, since the overwhelming majority of patients studied had disease that was advanced and previously shown to be refractory to therapy. Subgroups of patients that appear to benefit most include those with breast cancer who were treated with liposomal doxorubicin and those with advanced melanoma treated with liposomal tumor vaccines. Additional phase II and III clinical trials will better define the effectiveness of treatment modalities incorporating liposomes. VI-A. Future directions One of the earliest applications of liposomes may be in the amelioration of drug toxicity. Although not yet proven, the clinical studies reviewed suggest that liposomal delivery of doxorubicin reduces cardiotoxicity without sacrificing antitumor effect. Although similar claims have been made in support of continuous infusion doxorubicin [11], one can avoid unnecessary hospitalization or the bulk and expense of portable infusion devices by a single administration of the liposomal preparation. Liposome encapsulation can markedly alter the biodistribution and pharmacokinetics of well-known chemotherapeutic agents. The effectiveness of liposomal drug delivery in human trials thus far has probably been more closely related to altered pharmacokinetics rather than enhanced drug delivery to tumor or increased tumor responsiveness. As demonstrated by Gabizon [19], increased liposome circulating time in the murine model can be achieved by using small unilamellar vesicles containing a phosphatidylcholine of high phase-transition temperature and a small molar fraction of monosialoganglioside or hydrogenated phosphatidylinositol.(ABSTRACT TRUNCATED AT 400 WORDS)