Recombinant human growth hormone: rationale for use in the treatment of HIV-associated lipodystrophy

Lipodystrophy HIV-related and FGF21: A new marker to follow the progression of lipodystrophy?

Recently new evidence about fibroblast growth factor 21 (FGF21) highlights the opportunities to use this molecule in new pharmaceutical formulations to combat type 2 diabetes and metabolic syndrome. It is well known that HIV is per se a condition of insulin resistance and in particular the patient with HIV-related lipodystrophy has a condition strictly related to metabolic syndrome. Lipodystrophy is associated with severe metabolic side effects, including dyslipidemia, hepatic insulin resistance, and lipid oxidation impairment. Research carried out showed that FGF21 levels were significantly increased in untreated HIV-1-infected patients and the increase was much marked in HIV-1-infected antiretroviral-treated patients that have developed lipodystrophy and in the patients with greatest metabolic alterations. FGF21 is expressed mainly by the liver, but also by other tissues such as the thymus, adipose tissue, and skeletal muscle. Therefore, many researchers have considered the investigation of possible variations of FGF21 in patients with significant alterations in body composition both in regard to fat mass and lean mass. In the light of the possible interactions between FGF21 and metabolic syndrome, it seems interesting to evaluate the implication of this hormone in patients with HIV-related lipodystrophy who have a severe metabolic picture of insulin resistance with important alterations in body composition.

Population pharmacokinetic analysis of tesamorelin in HIV-infected patients and healthy subjects

BACKGROUND AND OBJECTIVES

Tesamorelin is a synthetic analogue of growth hormone-releasing factor (GRF), which increases basal and pulsatile growth hormone (GH) secretion and subsequently increases insulin-like growth factor (IGF)-1. Limited information is available about the pharmacokinetics of this compound. Consequently, the aim of this study was to characterize the population pharmacokinetics of tesamorelin in HIV-infected patients and healthy subjects.

METHODS

A total of 38 HIV-infected patients and healthy subjects receiving subcutaneous tesamorelin doses of 1 or 2 mg administered daily during 14 consecutive days were included in the analysis. An open one-compartment model with first- and zero-order absorption and first-order elimination was developed to best describe the data using NONMEM(®) VII. The effect of different covariates on tesamorelin pharmacokinetics was investigated. Model evaluation was performed using predictive checks and non-parametric bootstrap.

RESULTS

Plasma clearance and its interindividual variability [% coefficient of variation (CV)] was estimated to be 1,060 L/h (33.6 %). Volume of distribution was calculated to be 200 L (17.7 %). Age, body size measures, race and health status were not related to tesamorelin pharmacokinetic parameters within the range of covariates studied. The fraction of tesamorelin absorbed by a first-order process is 13.1 % higher on day 14 compared with day 1. Predictive checks and non-parametric bootstrap demonstrated that the model is appropriate in describing the time course of tesamorelin plasma concentrations in both HIV-infected patients and healthy subjects.

CONCLUSIONS

An open one-compartment model with first and zero order absorption processes and linear elimination is suitable to characterize the pharmacokinetics of tesamorelin. The fraction of tesamorelin absorbed by a first-order process evolves with time. No clinically relevant covariates were identified as predictors of tesamorelin pharmacokinetics.

Recombinant Human Growth Hormone: HIV-Related Lipodystrophy

This Hospital Pharmacy feature is extracted from Off-Label Drug Facts, a publication available from Wolters Kluwer Health. Off-Label Drug Facts is a practitioner-oriented resource for information about specific drug uses that are unapproved by the US Food and Drug Administration. This new guide to the literature enables the health care professional or clinician to quickly identify published studies on off-label uses and determine if a specific use is rational in a patient care scenario. References direct the reader to the full literature for more comprehensive information before patient care decisions are made. Direct questions or comments regarding Off-Label Drug Uses to jgeneral@ku.edu.

Incomplete immune recovery in HIV infection: mechanisms, relevance for clinical care, and possible solutions

Treatment of HIV-infected patients with highly active antiretroviral therapy (HAART) usually results in diminished viral replication, increasing CD4+ cell counts, a reversal of most immunological disturbances, and a reduction in risk of morbidity and mortality. However, approximately 20% of all HIV-infected patients do not achieve optimal immune reconstitution despite suppression of viral replication. These patients are referred to as immunological nonresponders (INRs). INRs present with severely altered immunological functions, including malfunction and diminished production of cells within lymphopoetic tissue, perturbed frequencies of immune regulators such as regulatory T cells and Th17 cells, and increased immune activation, immunosenescence, and apoptosis. Importantly, INRs have an increased risk of morbidity and mortality compared to HIV-infected patients with an optimal immune reconstitution. Additional treatment to HAART that may improve immune reconstitution has been investigated, but results thus far have proved disappointing. The reason for immunological nonresponse is incompletely understood. This paper summarizes the known and unknown factors regarding the incomplete immune reconstitution in HIV infection, including mechanisms, relevance for clinical care, and possible solutions.

Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy

Tesamorelin (Egrifta™) is a synthetic analogue of human growth hormone-releasing hormone (also known as growth hormone-releasing factor) that stimulates the synthesis and release of endogenous growth hormone. It is the first and, so far, only treatment indicated for the reduction of excess abdominal fat in patients with HIV-associated lipodystrophy. This article reviews the pharmacological properties, clinical efficacy and tolerability of tesamorelin in patients with HIV-associated central fat accumulation. Subcutaneous tesamorelin was effective in reducing visceral adipose tissue (VAT), but did not affect subcutaneous adipose tissue to a clinically significant extent in two 26-week, well designed, clinical trials in patients with HIV-associated central fat accumulation. This reduction in VAT was maintained in the longer term in patients who continued to receive tesamorelin until week 52 in the extension phases of the two trials. However, discontinuation of therapy during this period resulted in the reaccumulation of VAT. Tesamorelin therapy was also associated with significant improvements in other body composition measures (e.g. trunk fat and waist circumference) and improvements were generally seen in some body image parameters (e.g. belly image distress). Tesamorelin was generally well tolerated, with treatment-emergent serious adverse events occurring in <4% of patients during 26 weeks of therapy. Most of these events were injection-site reactions or events known to be associated with growth hormone therapy (e.g. arthralgia, headache and peripheral oedema). Although long-term clinical experience is needed to further assess the benefits and risks of therapy, current evidence suggests that tesamorelin may be useful for reducing visceral adiposity in patients with HIV-associated lipodystrophy, thereby potentially improving self image.

Spotlight on tesamorelin in HIV-associated lipodystrophy

Tesamorelin (Egrifta™) is a synthetic analog of human growth hormone-releasing hormone (also known as growth hormone-releasing factor) that stimulates the synthesis and release of endogenous growth hormone. It is the first and, so far, only treatment indicated for the reduction of excess abdominal fat in patients with HIV-associated lipodystrophy. This article reviews the pharmacological properties, clinical efficacy and tolerability of tesamorelin in patients with HIV-associated central fat accumulation. Subcutaneous tesamorelin was effective in reducing visceral adipose tissue (VAT), but did not affect subcutaneous adipose tissue to a clinically significant extent in two 26-week, well designed, clinical trials in patients with HIV-associated central fat accumulation. This reduction in VAT was maintained in the longer term in patients who continued to receive tesamorelin until week 52 in the extension phases of the two trials. However, discontinuation of therapy during this period resulted in the reaccumulation of VAT. Tesamorelin therapy was also associated with significant improvements in other body composition measures (e.g. trunk fat and waist circumference) and improvements were generally seen in some body image parameters (e.g. belly image distress). Tesamorelin was generally well tolerated, with treatment-emergent serious adverse events occurring in <4% of patients during 26 weeks of therapy. Most of these events were injection-site reactions or events known to be associated with growth hormone therapy (e.g. arthralgia, headache and peripheral edema). Although long-term clinical experience is needed to further assess the benefits and risks of therapy, current evidence suggests that tesamorelin may be useful for reducing visceral adiposity in patients with HIV-associated lipodystrophy, thereby potentially improving self image.

Growth hormone and HIV infection: contribution to disease manifestations and clinical implications

In untreated HIV patients growth hormone deficiency contributes to loss of lean and fat mass. Pharmacologic doses of growth hormone successfully reverse this wasting process. In patients responding to antiretroviral therapies several non AIDS-related complications usually common among older, uninfected persons now occur more frequently in younger HIV patients. Among these conditions are cardiovascular disease and metabolic disorders. Although their etiology is multifactorial, changes in growth hormone biology reflecting relative growth hormone deficiency occur and may be involved. In these patients truncal obesity, and associated dyslipidemia and glucose homeostasis changes contribute to impaired quality of life and increased cardiovascular risk. Treatment with growth hormone and growth hormone releasing factor leads to short-term improvement of some of these abnormalities. This paper will review abnormalities of growth hormone biology and the use of growth hormone and growth hormone releasing factor as therapeutic agents in HIV patients.

Sequence and structure continuity of evolutionary importance improves protein functional site discovery and annotation

Protein functional sites control most biological processes and are important targets for drug design and protein engineering. To characterize them, the evolutionary trace (ET) ranks the relative importance of residues according to their evolutionary variations. Generally, top-ranked residues cluster spatially to define evolutionary hotspots that predict functional sites in structures. Here, various functions that measure the physical continuity of ET ranks among neighboring residues in the structure, or in the sequence, are shown to inform sequence selection and to improve functional site resolution. This is shown first, in 110 proteins, for which the overlap between top-ranked residues and actual functional sites rose by 8% in significance. Then, on a structural proteomic scale, optimized ET led to better 3D structure-function motifs (3D templates) and, in turn, to enzyme function prediction by the Evolutionary Trace Annotation (ETA) method with better sensitivity of (40% to 53%) and positive predictive value (93% to 94%). This suggests that the similarity of evolutionary importance among neighboring residues in the sequence and in the structure is a universal feature of protein evolution. In practice, this yields a tool for optimizing sequence selections for comparative analysis and, via ET, for better predictions of functional site and function. This should prove useful for the efficient mutational redesign of protein function and for pharmaceutical targeting.