Use of Protease Inhibitors

Existing treatment for HIV focuses mainly on the use of protease inhibitors and reverse transcriptase inhibitors. This strategy, however, is to inhibit the HIV from repheating after it has invaded the CD4 cell. 

Use of protease inhibitors other than LPV/r and NFV is problematic in children due to lack of suitable pediatric drug formulations for IDV and SQV (Table 10(a) and (b)). 

Garcfa-Carreno, F.L. and Hernandez-Cortes, P. 2000. Use of Protease Inhibitors in Seafood Products. In Seafood Enzymes Utilization and influence on postharvest seafood quality (N. Haard and B. Simpson, eds.) pp. 531-548. Marcel Dekker, New York. 

Previously, both in our laboratory and elsewhere, cellulases subjected to purification procedures were obtained from commercial sources (5,6, 8,9,10,13,39,46). Three cellobiases and several endoglucanases and cellobiohydrolases from commercial preparations were purified in our laboratory. While use of protease inhibitors in the fractionation procedures minimized proteolysis during enzyme purification, the existence of enzymes proteolytically modified, presumedly during prolonged fermentation (required for obtaining high titres for commercial production), was a source of confusion, as previously explained. Therefore, we prepared T. reesei cellulase harvested from young culture broth. This was used to carry out the enzyme purification procedures described below. 

In the HIV infected population, further evidence suggested that visceral fat accumulation, dyslipidemia, and insulin resistance are closely linked and associated with antiretroviral treatment, most pronounced with the use of protease inhibitors. In contrast, subcutaneous fat wasting is primarily determined by the choice of nucleoside reverse transcriptase inhibitor (NRTI). Switching studies have supported this notion, since substitution of stavudine has been associated with improvement in fat wasting, while switching a protease inhibitor had no beneficial effect in more than 30 clinical trials (142). 

In a cohort study (164) in 1785 women, 69 incident cases of diabetes mellitus were diagnosed, with an average incidence of 1.5 cases per 100 patient-years. In patients taking protease inhibitors, incidence rates were about twice as high (2.8 cases per 100 patient-years) as among users of NNRTIs or untreated patients (1.2%) and uninfected controls (1.4%). In a multivariate model use of protease inhibitors (HR = 2.9 1.5, 5.6), age, and BMI were independent risk factors for diabetes. 

Soon after the introduction of highly active antiretroviral combination treatments (HAART), lipodystrophy was associated with the use of protease inhibitors, and several reports have confirmed that a syndrome of peripheral lipodystrophy, central adiposity, breast hypertrophy in women, hyperlipidemia, and insulin resistance with hyperglycemia is an adverse event associated with the use of potent combination antiretroviral therapy, particularly including HIV-1 protease inhibitors (982-987). 

As mentioned above, the rectal route is very attractive for systemic delivery of peptide and protein drugs, but rectal administration of peptides often results in very low bioavailability due to not only poor membrane penetration characteristics (transport barrier) but also due to hydrolysis of peptides by digestive enzymes of the GI tract (enzymatic barrier). Of these two barriers, the latter is of greater importance for certain unstable small peptides, as these peptides, unless they have been degraded by various proteases, can be transported across the intestinal membrane. Therefore, the use of protease inhibitors is one of the most promising approaches to overcome the delivery problems of these peptides and proteins. Many compounds have been used as protease inhibitors for improving the stability of various peptides and proteins. These include aprotinin, trypsin inhibitors, bacitracin, puromycin, bestatin, and bile salts such as NaCC and are frequently used with absorption enhancers for improvement in rectal absorption. 

The one nagging question that remained from this study was whether the optimal use of protease inhibitors should be restricted to those patients with advanced disease. The lack of a clinical effect in the substudy of patients with 50 to 200 CD4 cells did not spark a controversy in... 

The main aspect for monitoring intracellular components was to find the bottlenecks in cephalosporin synthesis. For this it was important to measure the activities of the relevant enzymes in the biosynthesis. After tests in the past [49, 51] and new investigations [22] it was known that the use of protease inhibitors in the disintegration buffer was necessary for routine analysis of activities in crude material. The expense for such measurements was very high and so the main point was the detection of ACVS- and IPNS-activity. But all other important activities were monitored as well. 

The inclusion of enzyme inhibitors in a formulation may help to overcome the enzymatic activity of the epithelial barrier. Work in this field has concentrated on the use of protease inhibitors to facilitate the absorption of therapeutic peptides and proteins. Protease inhibitors demonstrating potential to increase... 

Dose may need to be adjusted when there is concomitant use of protease inhibitors or nonnucieoside reverse transcriptase inhibitors,... 

In contrast, a detailed report on a large series of patients has provided impressive evidence that the use of protease inhibitors in HIV-infected patients with hereditary bleeding disorders can lead to an increased bleeding tendency (41). This effect, which is most likely to occur when ritonavir is used, is also unexplained. 

Any proteomic study starts with the collection of proteins from biological samples such as cell culture media, cultured cells, serum, or any biological fluid, and a variety of animal tissues. The first step is to obtain a protein sample under conditions of least protein degradation. This involves use of various protease inhibitors that stop the protein degradation. The use of protease inhibitors depends on the type of sample and the analytical technique used in the subsequent analysis. The selection of protease inhibitors used is critical since many protease inhibitors and detergents used in the preparation of tissue homogenates can interfere with mass spectrometry (MS)... 

Finally, there is an increased use of protease inhibitors (e.g. indinavir sulphate) that inhibit viral low molecular weight polypeptide gene products. Despite the tremendous increase in antiviral... 

Researchers have evaluated the use of protease inhibitors with the aim of slowing the rate of degradation of proteins and peptides in the GI tract. The hypothesis was that a slow rate of degradation would increase the amount of protein and peptide drug available for absorption. 

Thus, in this chapter we will introduce the use of protease inhibitors to improve the stability and absorption of peptide and protein biopharmaceuticals in the gut. 

NaGC). The use of protease inhibitors to improve absorption of peptides and proteins is summarized in Table 5.2. As shown in the table, protease inhibitors were utilized not only for the oral route but also for other routes such as nasal, buccal, and rectal. 

These findings indicated that the action of protease inhibitors on the mucosal membrane was both reversible and nontoxic. Consequently, the use of protease inhibitors is one of the most useful approaches for improving the stabihty and absorption of biopharmaceutical peptides and proteins, despite the involved mechanisms not being fully understood. 

The enzymes called proteases are necessary for the digestion of proteins. A newly proposed treatment for acquired immune deficiency syndrome (AIDS) involves the use of protease inhibitors, and as AIDS is an immunodeficiency disease, with cancer sometimes described in the same way, there may be a connection. (AIDS is by most accounts caused by the retrovirus HIV, and cancer may in some instances be traced to retroviruses.)... 

D. Effects on Carbohydrate and Lipid Metaboiism The use of protease inhibitors in HAART drug combinations has led to the development of disorders in carbohydrate and lipid metabolism. It has been suggested that this is due to the inhibition of lipid-regulating proteins which have active sites with structural homology to that of HIV protease. The syndrome includes hyperglycemia and insulin resistance or hyperlipidemia, with altered body fat distribution. Buffalo hump, gynecomastia, and truncal obesity may occur with facial and peripheral lipodystrophy. The syndrome has been observed with protease inhibitors used in HAART regimens, with an incidence of 30-50% and a median onset time of approximately 1 year s duration of treatment. 

Use of protease inhibitor-based regimens has been found to be associated with a higher incidence of infections and neutropenia in patients receiving cyciophosphamide, doxorubicin and etoposide (CDE) than use of a NNRTI-based regimen. 

TaJ>le 21.4 Summary of the manufacturers dosage recommendations (unless stated otherwise) for combined use of protease inhibitors and NNRTIs... 

The current use of protease inhibitors and voriconazole is predicted to interfere with the metabolism of both drugs. Studies suggest that ritonavir decreases voriconazole levels, but no interaction was seen between indinavir and voriconazole in one study. 

Established interactions of clinical importance. The protease inhibitors increase the levels of rifabutin, with a consequent increase in adverse effects unless the rifabutin dose is reduced. Ritonavir is the most potent protease inhibitor in this regard, and the combination has been considered contraindicated. However, the CDC in the US say that the combination may be used if the dose of rifabutin is markedly reduced. In addition, rifabutin decreases the levels of some protease inhibitors, particularly saquinavir, increasing the risk of treatment failure. Rifabutin should not be used when saquinavir is the sole protease inhibitor (no longer recommended). However, there is some evidence that rifabutin can be used with ritonavir-boosted saquinavir. Table 21.5 , (p.827) summarises the clinical recommendations for the concurrent use of protease inhibitors and rifabutin. Therapy should be well monitored. Note that, in one analysis, the use of rifabutin 150 mg twice weekly with low-dose ritonavir and a second protease inhibitor was associated with low rifabutin levels. " Recommended doses of rifabutin in patients taking ritonavir-boosted protease inhibitors are 150 mg every other day or three times per week. ... 

The subcutaneous route for administration of insulin has many serious drawbacks, and alternative routes continue to attract considerable research interest. Nearly all available orifices of the human body seem to have gained attention as presenting possible noninvasive sites for insulin absorption. However, even by using modem enhancer techniques, only a small or minor fraction of the hormone becomes bioavailable when provided by most of these routes, except perhaps the pulmonary route. Key barriers to insulin absorption via the alternative routes are the resistance of those membranes to insulin penetration, the tendency of insulin to exist in associated form, and insulin proteolysis. Protection from proteolysis through some sort of encapsulation, the use of complex emulsion systems, and/or the use of protease inhibitors—association of the hormone with polymeric particles, and addition of permeation enhancers have been utilized to overcome those barriers. The absorption and enzymatic barriers to nonparenterally administered protein dmgs and the use of enhancers to modify absorption have been discussed in recent reviews (Lee, 1986 Lee e/a/., 1991a Zhou, 1994). The present review of alternative administration of insulin mainly covers investigations published since 1970. 

Tozaki H, Odoriba T, Iseki T, Taniguchi T, Fujita T, Murakami M, Muranishi S, Yamamoto A. Use of protease inhibitors to improve calcitonin absorption from the small and large intestine in rats. JPharm Pharmacol. 1998 Aug 50(8) 913-20. 

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