By C. Brant. University of Mary Hardin-Baylor.
Contributors to this process include haemolysis buy betoptic 5 ml free shipping, adhesive interactions between blood cells and endothelial cells and disruption of the balance between vasodilators and vasoconstrictors buy discount betoptic 5ml on-line. Aﬀected individuals incur a chronic disease characterisation that can include acute episodes of intense vaso-occlusive crisis pain aﬀecting the chest, back, abdomen or extremities, vaso-occlusive events aﬀecting the lung (acute chest syndrome) or brain (ischemic stroke), priapism, episodes of splenic sequestration of blood, bacterial sepsis as well as chronic end organ damage that includes progressive retinopathy, renal insuﬃciency, skin ulcers, osteonecrosis and chronic respiratory insuﬃciency. Thirty-nine percent of study subjects had no episodes of pain and 1% had more than six episodes of pain per year. A thorough understanding of the clinical course for sickle cell disease in hydroxyurea-treated patients will become critical for anticipating outcomes for placebo-treated subjects in these future safety and eﬃcacy investigations. View Online The Challenges of Conducting Clinical Trials in Diseases with Small Target Populations 61 3. Overall incidence of the disorder is 1 in 3–5 million people with an autosomal recessive mode of transmission. Of the 92 patients, 23 were receiving exclusively episodic (on-demand) treatment in response to bleeding episodes and data on frequency of bleeding episodes was available for 16. Study subjects on prophylactic treatment with catrideca- cog experienced a mean of 0. When there are no precedented treatments to inform clinical development of new agents, this challenge can become particularly daunting. Validation/qualication of surrogate end points predictive of benecial eﬀect View Online 62 Chapter 3 Table 3. Party responsible for Disease End point development Autosomal dominant Clinical composite Sponsor initiated polycystic kidney of disease severity disease Duchenne muscular 6 minute walk distance Sponsor-academic dystrophy collaboration Chronic myeloid Freedom from disease Sponsor and leukaemia progression investigators (chronic phase) Complete cytogenetic Sponsor and investigators response (surrogate end (based on 5 year point for recently long-term study results) diagnosed chronic phase disease) from treatment can also be challenging. Respective approaches that can be employed to identify end points or surrogate end points for disease activity/ disease progression include analysis of data from natural history studies and analysis of existing data from natural history and interventional studies to qualify/validate end points or surrogate end points. The disease continues with progressive cardiac problems manifesting in the second decade of life and death from pneumonia or cardiac involvement in the late teens or early 20s is commonly observed in aﬀected patients. Natural history studies have helped to dene the temporal chronology of this disease progression. That accelerated approval was based on the high observed frequency of haematological remissions and cytogenetic response rates and the high likelihood that these results would lead to a real benet. By 12 months median follow-up, the imatinib treatment arm had demonstrated superior results with 96. Regulatory approval for imatinib within this indication was sought and a large proportion of the combination therapy subjects subsequently switched to imatinib treatment. Initial publication of study results aer median follow-up of 19 months also described a clear benet in the imatinib treatment arm for the primary end point of freedom from disease progres- sion. Incomplete understanding of the resulting standard of care may introduce excessive heterogeneity into clinical studies, confound sponsor eﬀorts to control for heterogeneity via eligibility criteria, supportive care guidelines or randomisation stratications and compromise the ability to detect treatment eﬀect from the therapeutic intervention. A number of strategies can be employed to better understand the standard of care in rare diseases and thereby inform design of clinical studies. These include accessing supportive care guidelines from clinical experts, review of clinical study databases for information on frequently used concomitant medications and non-pharmacological supportive care and access to disease registries of individual patient data. Given the dismal outcomes for this condition and the limited avenues for pharmacological intervention, substantial eﬀorts have been devoted to improving outcomes by optimising supportive care. Results from these studies, whether positive or not for the primary end point, have the potential to inuence the standard of care used by practitioners based on results for secondary end points. Recently re- ported results for that study did not demonstrate a signicant reduction in the rate of the primary outcome, mortality or major disability 90 days post- event. However, in an ordinal analysis of the primary outcome event, to enhance statistical power for assessing physical functional outcomes, there were signicantly better functional outcomes in patients who received intensive blood pressure control. View Online The Challenges of Conducting Clinical Trials in Diseases with Small Target Populations 67 3. The disease is characterised by red cell aplasia that classically presents with severe anaemia in early infancy, oen in association with physical anomalies and short stature. Across aﬀected individuals the maintenance dose is highly variable; in over 20% of patients glucocorticoids can be completely stopped with maintenance of adequate haemoglobin levels, whereas some patients become refractory to glucocorticoid therapy and require ongoing transfusion support. The limitations in epidemiological knowledge, the variability in clinical responses to treatment and a lack of evidence-based guidance for supportive care creates challenges in antici- pating the standard of care for subjects with this disorder and can compromise the outcome of clinical studies. To address these limitations in knowledge, investigators established the Diamond Blackfan Anemia Registry of North America. With informed consent, the registry collects demographic, laboratory, clinical and survival information and has generated analyses of disease epidemiology, genetics, congenital anomalies, treatment practices, treatment responses and treatment-related toxicities. However, regulatory approval of pharmaceutical agents to treat rare diseases requires adequate and well- controlled investigations as the primary basis for determining whether there is substantial evidence to support claims of eﬀectiveness and that particulars and documents in an application for market authorisation for a medicinal product that demonstrate the potential risks are outweighed by the thera- peutic eﬃcacy of the product. All subjects leukaemia have the fusion oncogene responsible for disease Haemophilia A Kogenate, Enrichment. Population polycystic kidney inhibition best suited to test treatment disease eﬀect selected via clinical study design Haemophilia A Moroctocog alfa Eﬃcient statistical design. Reduced overall sample size requirement access suﬃcient sample size to support hypothesis testing with regard to claims of eﬃcacy and to support conclusions of benet/risk.
Bone marrow transplantation and peripheral blood stem cell transplantation are done to restore stem cells that are destroyed by high doses of radiation or chemotherapy order betoptic 5ml free shipping. Recent research work has been focused on studying gene therapy for cancer treatment cheap 5 ml betoptic visa. Gene therapy is an experimental treatment that involves introducing genetic material into the cancer cells to destroy the cells (6). Angiogen- esis plays an important role in the growth and spread of cancer cells (7). New blood vessels act as a source of oxygen and nutrients to the cancer cells, allowing these cells to grow, invade nearby tissue, spread to other parts of human body, and form new colonies of cancer cells. Angiogenesis inhibitors are used to prevent the for- mation of blood vessels, thereby depleting the cancer cells of oxygen and nutrients. Hyperthermia (also called thermal therapy or thermotherapy) is a type of cancer treatment technique in which the cancer cells are exposed to high temperatures (up to 113◦F). Research has shown that high temperatures can damage and kill cancer cells with minimal injury to normal tissues (8). By damaging proteins and func- tional structures within cells, hyperthermia destroys cancer cells (9). Hyperthermia may make some cancer cells more sensitive to radiation or harm other cancer cells that radiation cannot damage. Thus, it is almost used with other forms of cancer therapy, such as radiation and chemotherapy (10). Laser therapy is most commonly used to treat super- ﬁcial tumors on the surface of the body or the lining of internal organs. Photody- namic therapy is a type of cancer treatment that uses a drug called a photosensitizer or photosensitizing agent (12). When photosensitizers are exposed to this speciﬁc wavelength, they produce singlet oxygen, which destroys cancer cells. Targeted cancer therapy uses target-speciﬁc drugs that invade cancer cells and block the growth and metasta- sis of cancer cells by interfering with speciﬁc molecules involved in carcinogenesis and tumor growth (13). To overcome the disadvantages of current cancer treatment techniques, the scientiﬁc community has turned toward nanotechnology to develop newer and more effective drug carrier systems to safely shepherd the anticancer drugs to the cancer cells. Examples of drugs in this class include methotrexate, ﬂuorouracil, hydroxyurea, and mercaptopurine. A few examples of drugs in this class include cisplatin and antibiotics such as daunorubicin, doxorubicin, and etoposide. Disruption of Synthesis or Breakdown of Mitotic Spindles Mitotic spindles serve as molecular railroads with “north and south poles” in the cell when it starts to divide. These drugs disrupt the formation of these spindles and therefore interrupt cell division. Classic examples of drugs in this class of mitotic disrupters include vinblastine, vincristine, and paclitaxel. The applications of nanoparticles as carriers for these anticancer drugs are discussed in the following sections. Results of numerous scientiﬁc research studies done in nanotech- nology and nanomedicine are inspiring the scientiﬁc community to discover new, innovative, noninvasive tools at the nanoscale level for such purposes. Nanoscale cantilevers (15) and quantum dots (16,17) are being studied as cancer detection tools at the cellular level. If the tumor has not been detected in its early stage, treatment methods should be devised to eradicate the fully developed cancer cells without harming the normal, healthy cells of human body. The various types of nanoparticles that are currently studied for their use as drug delivery systems are polymeric micelles, magnetic nanoparticles, colloidal gold nanoparticles, and ceramic nanoparticles (18–20). These nanoparticulate-based drug delivery systems can be characterized for their localization in tumor cells by coating them with tumor-speciﬁc antibodies, peptides, sugars, hormones, and anticarcinogenic drugs. These nanoparticles have been effectively coupled with the abovementioned anti- carcinogenic chemotherapeutic agents and have been tested for their target speci- ﬁcity. These nanoparticles are superior over conventionally available drug delivery systems, as the chemotherapeutic agents can be targeted to a speciﬁed area of the human body by adding nanoscale surface receptors. These receptors speciﬁcally recognize the target tissue and bind to it and release the drug molecules (21). Drugs can also be pro- tected from degradation by encapsulating them with nanoparticle coatings (22). As nanoparticles are extremely small, they can penetrate through smaller capillaries and are easily taken up by cancer cells. The use of biodegradable nanoparticles allows sustained drug release over a period of time (23). Thus, nanoparticles as drug delivery systems, with enhanced target speciﬁcity, can overcome the limitations of conventional cancer treatment techniques.
The encapsulation of insulin into mucoadhesive alginate/chitosan nanoparticles was shown to be a key factor in the improvement of oral absorption and oral bioactivity in diabetic rats (20) generic betoptic 5 ml mastercard. These approaches substan- tiate the potential use of polymeric nanoparticles in oral administration of insulin buy 5ml betoptic visa, thereby bypassing the enzymatic degradation in the stomach. Insulin Delivery Through Inhalable Nanoparticles Inhalable, polymeric nanoparticle-based drug delivery systems have been tried ear- lier for the treatment of tuberculosis (21). Such approaches can be directed toward 120 Subramani insulin delivery through inhalable nanoparticles. Insulin molecules can be encapsu- lated within the nanoparticles and can be administered into the lungs by inhaling the dry powder formulation of insulin. The nanoparticles should be small enough to avoid clogging up the lungs but large enough to avoid being exhaled. Such a method of administration allows the direct delivery of insulin molecules to the bloodstream without undergoing degradation. A few studies have been done to test the potential use of ceramic nanoparticles (calcium phosphate) as drug deliv- ery agents (22,23). Porous hydroxyapatite nanoparticles have also been tested for the intestinal delivery of insulin (24). Preclinical studies in guinea pig lungs with insulin-loaded poly(lactide-co-glycolide) nanospheres demonstrated a signiﬁcant reduction in blood glucose level with a prolonged effect over 48 hours when com- pared with insulin solution (25). Insulin-loaded poly(butyl cyanoacrylate) nanopar- ticles when delivered to the lungs of rats were shown to extend the duration of hypoglycemic effect over 20 hours when compared with pulmonary administra- tion of insulin solution (26). The major factors limiting the bioavailability of nasally administered insulin include poor permeability across the mucosal membrane and rapid mucociliary clearance mechanism that removes the nonmucoadhesive formu- lations from the absorption site (27). To overcome these limitations, mucoadhesive nanoparticles made of chitosan/tripolyphosphate (28) and starch (29) have been evaluated. These nanoparticles showed good insulin-loading capacity, providing the release of 75% to 80% insulin within 15 minutes after administration. Biosensors and nonporous membranes with pores of 6-nm diameter are located in the exterior to detect the changes in blood glucose level and for insulin release. Another implantable, polymer-based micropump system with integrated biosensors for optimal insulin delivery without user intervention has been described in a recent study (33). Micro- fabrication techniques have taken the miniaturization science to the nanoscale level. Microneedles have also been reported as effective transdermal systems for insulin delivery (34). The concept of an assembled biocapsule consisting of two micro- machined membranes bonded together to form a cell-containing cavity bound by membranes with nanopores was reported earlier (Fig. While the nanopores were designed to be permeable to glucose, insulin, and other metabolically active products, the pores were small enough to prevent the passage of larger cytotoxic cells, macrophages, antibodies, and complement (36) (Fig. Other Nanoparticulate Systems for Insulin Delivery and Diabetes-Associated Symptoms Treatment Other than the ceramic and polymeric nanoparticles, gold nanoparticles have also been tested as insulin carriers. The nanoparticles showed long-term stability in terms of aggregation and good insulin loading of 53%. The use of chitosan served dual purpose by acting as a reducing agent in the synthe- sis of gold nanoparticles and also promoting the penetration and uptake of insulin across the oral and nasal mucosa in diabetic rats. The study concluded that oral and nasal administration of insulin-loaded, chitosan-reduced gold nanoparticles improved pharmacodynamic activity of insulin. Dextran nanoparticle–vitamin B12 combination has been tested to overcome the gastrointestinal degradation of vita- min B12–peptide–protein drug conjugates (38). These nanoparticles were found to protect the entrapped insulin against gut proteases. Dextran nanoparticle–vitamin B12 combination showed a release proﬁle that was suitable for oral delivery systems of insulin. The associated conditions are inﬂammatory diseases of skin and gums, diabetic retinopathy (eyes), diabetic neu- ropathy (nervous system), heart diseases, kidney diseases, delayed wound healing, and many more. Nanoparticulate systems have also been tested for the treatment of these associated conditions. Nanoparticle-based ocular drug delivery systems have been already described in the past decade (39,40). The scientiﬁc com- munity is working toward utilizing nanoparticle-based drug delivery systems for the treatment of diabetes-associated complications. These research studies are being conducted to under- stand how matter behaves at the nanoscale level. Factors and conditions governing the behavior of macrosystems do not really apply to the nanosystems. The major limitations and technological hurdles faced by nanotechnology and its applica- tions in the ﬁeld of drug delivery should be addressed (44,45).
This method was designed to be complementary to the recent structure-based virtual screening studies purchase 5ml betoptic with amex, although it was exclusively based on ligand information only buy 5 ml betoptic otc. This so-called frequent substructure 150 Substructure-based Virtual Screening mining, i. Several screening models were constructed by varying the parameters of substructure generation and score calculation. These models were benchmarked and the best performing model was subsequently applied for large-scale screening on a commercial vendor library. The first set consisted of 892 low-affinity antagonists, with activity values between 5. For analysis of the antagonists, each antagonist set was compared against a background set of 10,000 drug-like molecules. Each pair of antagonist and background sets represented an individual training set from which a model was created. To analyze the structural features of the molecules, the molecular structures were first converted into a machine readable format, i. In addition to normal chemical representation, translation into one of three elaborate chemical representations was also explored as alternative representations when converting the source molecules to graphs. The translated source and background compounds were then subjected to frequent substructure mining. Frequent substructure mining is a data mining technique that finds all frequently occurring substructures that are present in a preset 151 Chapter 5 26,27 minimum number of molecules, which in this study was set to 30% of the size of the set; a substructure is defined as any part of the molecule, ranging from a single atom to the complete structure. The number of generated substructures for each source set and chemical representation are provided in Table 1. In general, smaller sets, such as the high-affinity antagonists set (255 molecules) result in significantly higher numbers of generated substructures compared to larger sets, such as the low-affinity (892 molecules) and combined antagonist (1,147 molecules) sets. With increasing set size, the chance for an individual substructure to occur more frequently than the set minimum decreases, resulting in finding fewer substructures. In addition, the high mutual similarity between antagonists in the high-affinity set results in more substructures with frequencies above the support threshold. Number of generated substructures for each source set and chemical representation. Activity Range [a] Representation pKi ≥ 8 pKi ≥ 5 5 ≤ pKi < 8 Normal 4,424 471 408 Ar. Examples of discriminative substructures for high-affinity adenosine A2A antagonists versus drug-like background compounds. Note that the provided examples are all within the set of the 50 top ranking substructures. A2A Background Score Nr Substructure antagonists compounds contribution a N N 242 (94. Note that the provided examples are all within the set of the 50 top ranking substructures (described below). All substructures in Table 2 are also present in compound 1 (note that substructures may overlap). For two of these substructures, c and d of Table 2, this is illustrated in Figure 2. This figure shows one example of how substructures are positioned in the molecules they originate from. Note that the methanediamine substructure, c, occurs three times in compound 1 (and also once in compound 3 and twice in compound 2, Figure 1). For frequency calculations, however, it was counted 153 Chapter 5 only once per molecule. Substructures c and d each represent one of two types of substructures that exist: substructures that are clear molecular fragments such as rings and functional groups (d) and substructures that have an unspecified shape (c). The structure of compound 1 with two examples of discriminative substructures for A2A antagonists highlighted in bold. For each frequent substructure in the antagonist set, the occurrence in the background set was also determined. For instance, substructure c in Table 2 occurred in 247 of the 255 A2A antagonists, or 96. Since these substructures are frequently occurring in the A2A antagonists and infrequently in background compounds they are signified as ‘discriminative’ for A2A antagonists. This discriminative property is quantified by calculating the difference between the fraction of antagonists and the fraction of background compounds in which the substructures occur. This difference is referred to as ‘score contribution’ of a substructure and is used to rank the substructures. The top-ranked substructures, those with the highest score contribution, are the most ‘discriminative’ ones and were subsequently used for the screening. This is because the frequency of a in the background set is considerably lower than that of b, resulting in a higher score contribution for a.