Growth Hormone-releasing Factor Analog Research Articles

Safety and metabolic effects of tesamorelin, a growth hormone-releasing factor analogue, in patients with type 2 diabetes: A randomized, placebo-controlled trial.

ObjectiveUse of growth hormone is associated with side effects, including insulin resistance. The objective of this study was to determine whether tesamorelin, a stabilized growth hormone-releasing hormone analogue, would alter insulin sensitivity or control of diabetes.DesignA 12-week randomized, placebo-controlled study of 53 patients with type 2 diabetes. Three treatment groups: placebo, 1 and 2 mg tesamorelin.MeasurementsFasting glucose, glucose and insulin from oral glucose tolerance test, glycosylated hemoglobin (HbA1c), home blood glucose, insulin-like growth factor-1, and lipids.Main outcome measureRelative insulin response following oral ingestion of glucose.ResultsNo significant differences were observed between groups in relative insulin response over the 12-week treatment period. At Week 12, fasting glucose, HbA1c and overall diabetes control were not significantly different between groups. In addition, relevant modifications in diabetes medications were similar between groups. Total cholesterol (-0.3±0.6 mmol/L) and non-HDL cholesterol (-0.3±0.5 mmol/L) significantly decreased from baseline to Week 12 in the tesamorelin 2 mg group (p<0.05 vs. placebo). No patient discontinued the study due to loss of diabetes control.ConclusionsTreatment of type 2 diabetic patients with tesamorelin for 12 weeks did not alter insulin response or glycemic control.Trial registrationClinicalTrials.gov NCT01264497.

Safety and metabolic effects of tesamorelin, a growth hormone-releasing factor analogue, in patients with type 2 diabetes: A randomized, placebo-controlled trial

Safety and metabolic effects of tesamorelin, a growth hormone-releasing factor analogue, in patients with type 2 diabetes: A randomized, placebo-controlled trial

Predictors of Treatment Response to Tesamorelin, a Growth Hormone-Releasing Factor Analog, in HIV-Infected Patients with Excess Abdominal Fat

BackgroundTesamorelin, a synthetic analog of human growth hormone-releasing factor, decreases visceral adipose tissue (VAT) in human immunodeficiency virus (HIV)-infected patients with lipodystrophy.Objectives1) To evaluate the utility of patient characteristics and validated disease-risk scores, namely indicator variables for the metabolic syndrome defined by the International Diabetes Federation (MetS-IDF) or the National Cholesterol Education Program (MetS-NCEP) and the Framingham Risk Score (FRS), as predictors of VAT reduction during tesamorelin therapy at 3 and 6 months, and 2) To explore the characteristics of patients who reached a threshold of VAT <140 cm2, a level associated with lower risk of adverse health outcomes, after 6 months of treatment with tesamorelin.MethodsData were analyzed from two Phase 3 studies in which HIV-infected patients with excess abdominal fat were randomized in a 2:1 ratio to receive tesamorelin 2 mg (n = 543) or placebo (n = 263) subcutaneously daily for 6 months, using ANOVA and ANCOVA models.ResultsMetabolic syndrome (MetS-IDF or MetS-NCEP) and FRS were significantly associated with VAT at baseline. Presence of metabolic syndrome ([MetS-NCEP), triglyceride levels >1.7 mmol/L, and white race had a significant impact on likelihood of response to tesamorelin after 6 months of therapy (interaction p-values 0.054, 0.063, and 0.025, respectively). No predictive factors were identified at 3 months. The odds of a VAT reduction to <140 cm2 for subjects treated with tesamorelin was 3.9 times greater than that of subjects randomized to placebo after controlling for study, gender, baseline body mass index (BMI) and baseline VAT (95% confidence interval [CI] 2.03; 7.44).ConclusionsIndividuals with baseline MetS-NCEP, elevated triglyceride levels, or white race were most likely to experience reductions in VAT after 6 months of tesamorelin treatment. The odds of response of VAT <140 cm2 was 3.9 times greater for tesamorelin-treated patients than that of patients receiving placebo.

Tesamorelin: A Growth Hormone-Releasing Factor Analogue for HIV-Associated Lipodystrophy

To evaluate the efficacy and safety of tesamorelin, a growth hormone releasing factor analogue approved by the Food and Drug Administration in November 2010 for the treatment of lipodystrophy associated with HIV infection. Literature was obtained through MEDLINE (1948-November 2011) and International Pharmaceutical Abstracts (1970-October 2011) using the search terms tesamorelin, TH9507, growth hormone releasing factor, and HIV-associated lipodystrophy syndrome. Additional publications were obtained through review of references within primary literature publications as well as pertinent Web sites. All articles published in English identified from the data sources were evaluated and all pertinent information was included. All studies relevant to the evaluation of efficacy and safety of tesamorelin in the management of HIV-associated lipodystrophy were included, with a focus on trials completed in humans. In 2 Phase 3 clinical trials and their pooled analyses, tesamorelin was proven to significantly decrease waist circumference and visceral adipose tissue (VAT) following 26 weeks of treatment. Both trials also demonstrated significant improvements in some subjective body image parameters. Both studies had 26-week extension phases that confirmed maintenance of VAT improvements on treatment without adverse impact on blood glucose and lipid parameters. Limited data support off-label uses of tesamorelin at this time. Tesamorelin is effective in improving visceral adiposity and body image in patients with HIV-associated lipodystrophy over 26-52 weeks of treatment. Potential limitations for its use include high cost and lack of long-term safety and adherence data. Tesamorelin provides a useful treatment option for management of patients with significant lipodystrophy related to HIV infection.

Tesamorelin: A novel therapeutic option for HIV/HAART-associated increased visceral adipose tissue

Metabolic complications are common in treated HIV patients. Their etiology is multifactorial and the development of increased abdominal fat contributes to cardiovascular risk and impaired quality of life. Treated patients with fat mass distribution changes have relative growth hormone deficiency. Both pharmacologic and physiologic doses of growth hormone reduce the increased visceral adipose tissue and improve the associated abnormal lipid profiles in short-term studies. However, impaired glucose homeostasis changes and significant musculoskeletal toxicity occurs. A novel growth hormone-releasing factor analogue, tesamorelin, provides a physiologic means of restoring a normal growth hormone secretion profile and reduces increased visceral adipose tissue, improving both abnormal lipid profiles and patients' quality of life. Glucose homeostasis is generally well maintained. Cessation of treatment with either growth hormone or tesamorelin results in a prompt return of truncal obesity. Management strategies for the long-term maintenance of the reduced visceral adipose tissue have not yet been clarified and long-term effects on decreasing cardiovascular risks and improving clinical outcomes are uncertain.

Tesamorelin for the treatment of excess abdominal fat in HIV-1-infected patients with lipodystrophy

Morphologic and metabolic abnormalities remain a common problem in patients with HIV-1 infection, which contributes to poor self image and may negatively impact on patient’s adherence to medication and success of therapy. In addition, these physiological and metabolic changes can lead to increased cardiovascular risk. In such patients, excess central fat could be associated with loss of subcutaneous fat. Several strategies to decrease the excess of visceral fat have been assessed. Tesamorelin, an injectable growth hormone-releasing factor analogue, has been shown to improve visceral fat adiposity with relatively little effect on subcutaneous fat with improvement in triglycerides and belly appearance distress. It is well tolerated overall without clinically significant changes in mean glucose or insulin levels. However, these benefits cease if treatment is discontinued.

Tesamorelin Approved for the Treatment of HIV-Related Visceral Adiposity

On November 10, 2010, the FDA approved the growth hormone-releasing factor analogue tesamorelin (Egrifta) for the treatment of visceral fat

Effects of Tesamorelin (TH9507), a Growth Hormone-Releasing Factor Analog, in Human Immunodeficiency Virus-Infected Patients with Excess Abdominal Fat: A Pooled Analysis of Two Multicenter, Double-Blind Placebo-Controlled Phase 3 Trials with Safety Extension Data

HIV patients treated with antiretroviral therapy (ART) often develop increased visceral adipose tissue (VAT). Our objective was to perform a pooled analysis of two phase-3 studies of tesamorelin in ART-treated HIV patients with excess abdominal fat. Two multicenter, international studies were conducted; a 26-wk randomized, placebo-controlled primary intervention phase was followed by a 26-wk safety extension. A total of 806 ART-treated HIV patients with excess abdominal fat were randomized in a 2:1 fashion to receive tesamorelin 2 mg (n = 543) or placebo (n = 263) sc daily. At wk 26, patients initially on tesamorelin were rerandomized to 2 mg tesamorelin (T-T group, n = 246) or placebo (T-P, n = 135) for an additional 26 wk, whereas patients on placebo were switched to tesamorelin (P-T, n = 197). Tesamorelin (GHRH(1-44)) at a dose of 2 mg or identical placebo, sc, was given daily. We evaluated percent change in VAT by computed tomography scan at wk 26. At wk 26, VAT decreased significantly in tesamorelin-treated patients (-24 +/- 41 vs. 2 +/- 35 cm(2), tesamorelin vs. placebo, P < 0.001; treatment effect, -15.4%). No significant changes were observed in abdominal sc adipose tissue (-2 +/- 32 vs. 2 +/- 29 cm(2), P = 0.08; treatment effect, -0.6%). Treatment with tesamorelin resulted in significant decreases in triglycerides (-37 +/- 139 vs. 6 +/- 112 mg/dl, P < 0.001; treatment effect, -12.3%) and cholesterol to high-density lipoprotein ratio (-0.18 +/- 1.00 vs. 0.18 +/- 0.94, P < 0.001; treatment effect, -7.2%) vs. placebo. Tesamorelin improved body image [belly appearance distress (P = 0.002)], patient rating of belly profile (P = 0.003), and physician rating of belly profile (P < 0.001). Mean IGF-I increased 108 +/- 112 vs.-7 +/- 64 ng/ml (P < 0.001 vs. placebo). At wk 52, decreases in VAT [-35 +/- 50 cm(2) (-17.5 +/- 23.3%)], waist circumference (-3.4 +/- 6.0 cm), triglycerides (-48 +/- 182 mg/dl), cholesterol (-8 +/- 38 mg/dl), and non-high-density lipoprotein (-7 +/- 38 mg/dl) were maintained (all P < 0.001 vs. original baseline) in the T-T group. Treatment with tesamorelin was generally well tolerated. No clinically meaningful differences were observed between groups in glucose parameters at wk 26 and 52. Treatment with tesamorelin reduces VAT and maintains the reduction for up to 52 wk, preserves abdominal sc adipose tissue, improves body image and lipids, and is overall well tolerated without clinically meaningful changes in glucose parameters.

Tesamorelin: A Synthetic Growth Hormone-Releasing Factor Analog for the Treatment of HIV-Associated Lipodystrophy

HIV-associated lipodystrophy has become a major challenge in the treatment of HIV infection. Recombinant human growth hormone has shown clinical effectiveness in therapy for growth hormone-deficient disorders and HIV-associated lipodystrophy, but its association with a variety of adverse effects has led to the development of human growth hormone-releasing factor analogs. Tesamorelin, a synthetic growth hormone-releasing factor, has been developed for the potential treatment of HIV-associated lipodystrophy. A multicenter, randomized, placebo-controlled, Phase III clinical trial demonstrated that tesamorelin was a beneficial treatment strategy for HIV-associated lipodystrophy with a good safety profile and a positive effect on reducing visceral fat and improving lipid profiles.

Tesamorelin, a human growth hormone releasing factor analogue

Background: The combination of clinical effectiveness with a variety of adverse side effects from the use of recombinant human growth hormone (rhGH) in therapy for growth hormone (GH)-deficient disorders has led to the development of human growth hormone releasing factor (GFR) analogues, which may be better tolerated. Tesamorelin, a synthetic GFR, has been developed as a potential treatment for a variety of conditions that may be associated with a relative deficiency of GH including HIV-related lipodystrophy. Objective: This article reviews the development of tesamorelin and its purported role in HIV-related lipodystrophy and other potential indications. Methods: Relevant articles and abstracts were obtained from searches of the medical and chemical literature databases and the references from published articles. Results/conclusion: A multicenter, randomized, placebo-controlled, Phase III clinical trial suggested that tesamorelin might be a beneficial treatment strategy for HIV-related lipodystrophy with a good safety profile and a positive effect on reducing visceral fat. Other potential indications for tesamorelin appear less promising from the current data.

Long-term safety and effects of tesamorelin, a growth hormone-releasing factor analogue, in HIV patients with abdominal fat accumulation

Treatment of HIV patients with daily tesamorelin, a growth hormone-releasing factor analogue, for 26 weeks resulted in a significant decrease in visceral adipose tissue (VAT) and improvement in lipids. The objective of the 26-week extension phase was to evaluate long-term safety and effects of tesamorelin. HIV patients with central fat accumulation in the context of antiretroviral therapy were randomized to tesamorelin 2 mg (n = 273) or placebo (n = 137) s.c. daily for 26 weeks. At week 26, patients originally on tesamorelin were rerandomized to 2 mg tesamorelin (T-T group, n = 154) or placebo (T-P group, n = 50), whereas patients originally on placebo were switched to tesamorelin (P-T group, n = 111). Safety included adverse events and glucose parameters. Tesamorelin was generally well tolerated. The prevalence of adverse events and serious adverse events during the extension phase was comparable with the initial phase. Changes in glucose parameters over 52 weeks were not clinically significant and similar to those after 26 weeks. The change in VAT was sustained at -18% over 52 weeks of treatment (P < 0.001 versus baseline) as was the change in triglycerides (-51 mg/dl, P < 0.001 versus baseline). Similar sustained beneficial effects were seen for total cholesterol, but high-density lipoprotein decreased minimally over 52 weeks. Upon discontinuation of tesamorelin, VAT reaccumulated. Treatment with tesamorelin was generally well tolerated and resulted in sustained decreases in VAT and triglycerides over 52 weeks without aggravating glucose. Though effects on VAT are sustained during treatment for 52 weeks, these effects do not last beyond the duration of treatment.

Metabolic Effects of a Growth Hormone–Releasing Factor in Patients with HIV

Visceral adipose tissue accumulates during antiretroviral therapy in many patients who are infected with the human immunodeficiency virus (HIV); this process is associated with an increased cardiovascular risk. We assessed the use of a growth hormone-releasing factor analogue, tesamorelin, to decrease visceral adiposity. We randomly assigned 412 patients with HIV (86% of whom were men) who had an accumulation of abdominal fat to receive a daily subcutaneous injection of either 2 mg of tesamorelin or placebo for 26 weeks. The primary end point was the percent change from baseline in visceral adipose tissue as shown on computed tomography. Secondary end points included triglyceride levels, the ratio of total cholesterol to high-density lipoprotein (HDL) cholesterol, the level of insulin-like growth factor I (IGF-I), and self-assessed body image. Glycemic measures included glucose and insulin levels. The measure of visceral adipose tissue decreased by 15.2% in the tesamorelin group and increased by 5.0% in the placebo group; the levels of triglycerides decreased by 50 mg per deciliter and increased by 9 mg per deciliter, respectively, and the ratio of total cholesterol to HDL cholesterol decreased by 0.31 and increased by 0.21, respectively (P<0.001 for all comparisons). Levels of total cholesterol and HDL cholesterol also improved significantly in the tesamorelin group. Levels of IGF-I increased by 81.0% in the tesamorelin group and decreased by 5.0% in the placebo group (P<0.001). Adverse events did not differ significantly between the two study groups, but more patients in the tesamorelin group withdrew from the study because of an adverse event. No significant differences were observed in glycemic measures. Daily tesamorelin for 26 weeks decreased visceral fat and improved lipid profiles, effects that might be useful in HIV-infected patients who have treatment-associated central fat accumulation. (ClinicalTrials.gov number, NCT00123253 [ClinicalTrials.gov] .).

Non‐Clinical Pharmacology and Safety Evaluation of TH9507, a Human Growth Hormone‐Releasing Factor Analogue

TH9507, an analogue of human growth hormone-releasing factor (hGRF1-44NH2) minimally modified by addition of a trans-3-hexenoyl moiety to Tyr1 of the amino acid sequence, was found to be resistant to dipeptidyl aminopeptidase-IV deactivation. Compared to natural hGRF1-44NH2, the modification slowed the in vitro degradation of the peptide in rat, dog and human plasma and prolonged the in vivo plasma elimination kinetics of immunoreactive TH9507. Plasma growth hormone and insulin-like growth factor-1 (IGF-1) markedly increased in pigs, rats and dogs after daily repeat intravenous or subcutaneous injections of TH9507 at doses up to 600 microg/kg. Subchronic toxicity studies in rats and dogs with TH9507 treatment for up to 4 months showed a significant, but not dose-related, increase in body weight gain associated with increased biomarker response. Although TH9507 was well tolerated by both rats and dogs, a more pronounced anabolic effect and more evident (reversible) adverse effects (liver and kidney findings, anaemia, clinical chemistry changes, organ weight effects) were observed in dogs after repeat daily subcutaneous injections, which were attributed to prolonged exposure to supraphysiological levels of growth hormone and/or IGF-1. In both rats and dogs, toxicokinetic evaluations indicated that exposure to immunoreactive TH9507 was dose related after both routes of administration. The apparent elimination t1/2 in dogs ranged from 21 to 45 min. In conclusion, TH9507 is a modified hGRF peptide having enhanced potency and duration of action. The adverse treatment-related effects in dogs appear to be associated with sustained exposure to supraphysiological levels of growth hormone and IGF-1 induced by prolonged TH9507 treatment.

Growth-hormone-releasing factor given to early-pregnant Genex-Meishan and Large White gilts: Effects on growth, carcass, meat quality and histochemical traits of the progeny

The objective of this study was to determine the effects of growth hormone-releasing factor (GRF) given in early gestation on post-weaning performance, carcass and meat quality and histochemical properties of two pig genotypes. Large White (LW, n = 10) and Genex Meishan-derived dam line (GM, with 50% Meishan genes, n = 10) gilts were treated during gestation with either saline injections (control, n = 5 LW and 5 GM), or 6.6 µg kg-1 of a GRF analog (n = 5 LW and 5 GM), given thrice daily from days 18 to 33 of gestation. After birth, at 56 d of age, four piglets (two barrows and two gilts) each from 20 litters were selected, allotted into individual pens and grown to slaughter weight (108.2 ± 2.3 kg). Feed intake was measured daily and pigs were weighed weekly. Prenatal GRF treatment had a detrimental effect (P &lt; 0.05) on daily gain in both genotypes, but did not affect carcass quality. Significant interactions between GRF, genotype and sex (P &lt; 0.01) for colour traits of the longissimus (L) and semimembranosus (SM) muscles and between GRF and genotype (P &lt; 0.01) for shear force of the L muscle were found. GM pigs had lower growth rate (P &lt; 0.01), higher feed intake (P &lt; 0.05), fatter and shorter carcass (P &lt; 0.001) than LW. L and SM muscles from GM pigs were less exudative (P &lt; 0.05) than LW. L muscle from LW had higher percentages of slow oxidative (SO) (P &lt; 0.001) and fast oxidative glycolytic (FOG) (P &lt; 0.01) fibres but lower percentage of fast glycolytic (FG) fibres (P &lt; 0.001) than that of GM. The results suggest that GRF given in early lactation reduces post-weaning growth of pigs from either breed, but does not affect carcass quality. GM pigs have poorer carcass quality than LW. Key words: Gestating gilts, growth hormone releasing factor, growth, carcass characteristics, meat quality traits, muscle fibre, pig

Pulmonary delivery of TH9507, a growth hormone releasing factor analogue, in the dog

A modified growth hormone releasing factor (GRF; TH9507), a 44 amino acid peptide analogue of natural human growth hormone releasing factor, is being developed for the treatment of age-associated conditions resulting from diminished growth hormone (GH) secretion. The inhalation route of administration is being considered as an alternative to subcutaneous injection. A study was undertaken in dogs to investigate the absorption of TH9507 following pulmonary delivery. Male beagle dogs were administered TH9507 by intratracheal dry powder insufflation and subcutaneous injection at doses of approximately 375 and 38 μg/kg, respectively. In a separate study, male and female dogs received 100 μg/kg intravenously. Blood samples were collected at selected sampling times after dosing and plasma levels of TH9507 were measured by radioimmunoassay. The bioavailability by the inhaled route was 41% relative to subcutaneous dosing, with an absolute bioavailability estimated at 13%. No significant difference was observed for the terminal half-life of TH9507 after intratracheal (39 min) and subcutaneous (26 min) administrations. The mean residence time (MRT) was greater following intratracheal administration (74 min versus 52 min; P<0.01). These data indicate that the delivery of the TH9507 by the inhalation route may provide a suitable alternative to subcutaneous injection.

Effects of GRF in early gestation on foetal development in Large White and Genex-Meishan gilts

The effects of growth hormone-releasing factor (GRF), given in early gestation, on reproductive traits, foetal development and pre-weaning growth of piglets from two breeds were studied. Large White (LW, n = 26) and Genex-Meishan (GM, containing 50% Meishan genes, n = 37) pregnant gilts were divided in two groups: (1) saline injections (n = 33) and, (2) injections of 6.66 µg kg-1 of a GRF analogue (n = 30), given thrice daily from days 18 to 33 of gestation. Jugular blood samples were collected on days 17, 34 and 109 of gestation and were assayed for various hormones and metabolites. Thirty-six gilts were slaughtered on day 110 of gestation and uterine, foetal and placental measurements were obtained. The other 27 gilts farrowed. There was a day × treatment interaction (P &lt; 0.001) for glucose, insulin, free fatty acids (FFA) and insulin-like growth factor I (IGF-I), with values being greater on day 34 in gilts receiving GRF. The increase in insulin concentration was greater in LW- than in GM-treated gilts (P = 0.02). Exogenous GRF increased foetal weight in LW litters only (1.13 ± 0.04 vs. 1.05 ± 0.03 kg; P = 0.04) whereas fat content of carcasses tended to be lower only in foetuses of treated GM gilts (5.3 ± 0.2 vs. 5.8 ± 0.2%; P = 0.1). Weight of the longissimus muscle and its fibre number were not influenced by GRF. Furthermore, growth of piglets to 28 d was not affected by GRF treatment (P &gt; 0.1). In conclusion, GRF given in early gestation seems to have different effects in LW and GM litters, yet it does not alter pre-weaning growth rate. Key words: Molybdenum, molybdenosis, copper, mine tailings, reclamation, animal health

Physiological traits in preterm calves during their first week of life.

Morbidity and mortality of preterm neonatal calves are higher than of calves born at normal term, possibly and in part due to immaturity of physiological functions. Physiological parameters were therefore studied during the first week of life in seven preterm calves, born on day 277 of gestation after dams were injected prostaglandin F2alpha and flumethason. Calves were fed colostrum of the first milking for the first 3 days and from day 4 to day 7 the same colostrum diluted with milk replacer. Body weight increased during the first week of life by 2.2 kg. Heart rate and respiratory rate were always relatively high, whereas values of rectal temperature, blood gases, haematological, metabolic and endocrine traits were in the range and behaved similarly as is the experience in full-term neonatal calves. Major exceptions were glucose and insulin, the concentrations of which barely rose postprandially, and growth hormone, the responses of which to growth hormone releasing factor analogue 1-29 were extremely variable and in part very small. In conclusion, calves born 2 week before normal term that survived the first week of life, although physiologically immature, were well able to handle ingested nutrients and to control their metabolism.

Characterization of subcutaneous Contramid® implantation: host response and delivery of a potent analog of the growth hormone-releasing factor

Cross-linked high amylose starch (Contramid®) was investigated as a solid implant for evaluation of host response in mice and as a possible delivery system for a human growth hormone-releasing factor analog (Hex-hGRF) release profile in pigs. Seventy mice were administered subcutaneously one 3 mm diameter Contramid® pellet and host reaction was evaluated over 6 months. Thirty pigs were divided into four groups. All animals of the three implanted groups were administered subcutaneously 15 mg Hex-hGRF, (1) one pure Hex-hGRF implant; (2) four 30/70 w/w Hex-hGRF/Contramid® implants; or (3) eight 15/85 w/w Hex-hGRF/Contramid® implants. The fourth group ( n=6) was injected subcutaneously twice daily with 10 μg/kg of Hex-hGRF over 5 consecutive days. Serum insulin-like growth factor-I (IGF-I) was monitored over 1 month. In mice, no adverse reaction occurred after implantation. Macroscopic and microscopic inflammatory reactions were always localized. Polymorphonuclear cells (PMNs) and macrophages predominated within and around the pellets, respectively. Thin fibrovascular septas eventually subdivided Contramid® pellets which were progressively phagocytosed by macrophages. In pigs, serum IGF-I concentrations were increased over a 10 day period in all implanted groups. The initial IGF-I peak observed in the daily injected group was avoided in both Contramid® implant groups but not in the pure Hex-hGRF implant group. These encouraging results warrant the development of Contramid® implants as a sustained delivery system for peptidic drugs.

GI side-effects of a possible therapeutic GRF analogue in monkeys are likely due to VIP receptor agonist activity

1 Growth hormone (GH) is used or is being evaluated for efficacy in treatment of short stature, aspects of aging, cardiac disorders, Crohn’s disease, and short bowel syndrome. Therefore, we synthesized several stable growth hormone-releasing factor (GRF) analogues that could be therapeutically useful. One potent analog, [D-Ala 2,Aib 8, 18,Ala 9, 15, 16, 22, 24–26,Gab 27]hGRF(1–27)NH 2 (GRF-6), with prolonged infusion caused severe diarrhea in monkeys; however, it had no side-effects in rats. Because GRF has similarity to VIP/PACAP and VIPomas cause diarrhea, this study investigated the ability of this and other GRF analogues to interact with the VIP/PACAP receptors. Rat VPAC 1-R (rVPAC 1-R), human VPAC 1-R (hVPAC 1-R), rVPAC 2-R and hVPAC 2-R stably transfected CHO and PANC 1 cells were made and T47D breast cancer cells containing native human VPAC 1-R and AR4–2J cells containing PAC 1-R were used. hGRF(1–29)NH 2 had low affinity for both rVPAC 1-R and rVPAC 2-R while VIP had a high affinity for both receptors. GRF-6 had a low affinity for both rVPAC 1-R and rVPAC 2-R and very low affinity for the rPAC 1-R. VIP had a high affinity, whereas hGRF(1–29)NH 2 had a low affinity for both hVPAC 1-R and hVPAC 2-R. In contrast GRF-6, while having a low affinity for hVPAC 2-R, had relatively higher affinity for the hVPAC 1-R. In guinea pig pancreatic acini, all GRF analogues were full agonists at the VPAC 1-R causing enzyme secretion. These results demonstrate that in contrast to native hGRF(1–29)NH 2, GRF-6 has a relatively high affinity for the human VPAC 1-R but not for the human VPAC 2-R, rat VPAC 1-R, rat VPAC 2-R or rat PAC 1-R. These results suggest that the substituted GRF analog, GRF-6, likely causes the diarrheal side-effects in monkeys by interacting with the VPAC 1-R. Furthermore, they demonstrate significant species differences can exist for possible therapeutic peptide agonists of the VIP/PACAP/GRF receptor family and that it is essential that receptor affinity assessments be performed in human cells or from a closely related species.

Modification of the carboxy-terminal amino acid sequence alters the Escherichia coli expression of a gene encoding multiple repeats of a bovine growth hormone releasing factor analog

Since investigations into the determinants of intracellular protein degradation have shown that the carboxy terminal sequence can be a critical factor for protein expression in Escherichia coli, we attempted to increase the expression of a protein containing multiple repeats of a bovine growth hormone releasing factor analog (bGRF30) by modifying the carboxy terminus with the addition of short amino acid extensions derived from stable E. coli proteins. Extensions capable of increasing bGRF30 per liter titers up to four-fold, as well as extensions that completely abolished bGRF30 expression were identified. Select C-terminal extensions were investigated further to determine the mechanism by which they affected bGRF30 expression. Analysis of mRNA levels and protein production titers suggests that extensions which increase bGRF30 titers primarily affect protein stability and ribosomal release. Negative extensions exert their influence through a more complex mechanism, appearing to interfere with the ability of ribosomes to be efficiently released from their cognate mRNA.