First-in-Human Pharmacokinetics and Safety Study of GSK3008356, a Selective DGAT1 Inhibitor, in Healthy Volunteers

Diacylglycerol acyltransferase (DGAT) enzymes are involved in triglyceride (TG) biosynthesis. GSK3008356 is a potent and selective DGAT1 inhibitor that was administered orally in a 2-part study as double-blind, randomized, placebo-controlled single doses (SDs) and repeat doses (RDs) in healthy subjects to investigate its pharmacokinetics, pharmacodynamics, and safety/tolerability. Gastrointestinal adverse events were considered drug related and increased with dose and when given as multiple doses. In the SD part (n = 80), GSK3008356 was dosed from 5 to 200 mg as single or multiple doses per day. In the RD part (n = 24), GSK3008356 was dosed twice daily at 1, 3, and 10 mg for 14 days. GSK3008356 was generally well tolerated in the SD and RD parts. With single doses, absorption was rapid (median t_max , 0.5-1.5 hours), whereas single-day divided dosing resulted in higher t_max . Following 14-day RD oral administration, GSK3008356 was also rapidly absorbed, with median t_max ranging from 0.5 to 0.75 hours on days 1 and 14. Estimated mean half-life ranged from 1.5 to 4.6 hours with SDs and 1.3 to 2.1 hours with RDs. Exposure of GSK3008356 was largely dose proportional after RDs. At higher doses, there was a trend toward lower absolute postprandial TG level in some subjects.

A population analysis of the DGAT1 inhibitor GSK3008356 and its effect on endogenous and meal-induced triglyceride turnover in healthy subjects

Non-alcoholic steatohepatitis (NASH) is a liver disease in which fatty infiltration is accompanied by liver inflammation. GSK3008356 is under development as a selective inhibitor of diacylglycerol acyltransferase 1 (DGAT1), a key enzyme involved in the formation of triglyceride (TG). Decreased DGAT1 activity can reduce circulating TG and liver TG, and therefore could potentially prevent or treat NASH. The aim of the current study was to develop a population pharmacokinetic-pharmacodynamic (PKPD) model that characterizes the PK disposition of GSK3008356 and its relation to the changes in blood TG. Drug concentrations were measured in 104 healthy adults receiving various single (SD) and repeat doses (RD) in a first time in human (FiH) study. A 30% fat meal was given at hour 2 postdose, and blood postprandial TG concentrations were measured at various time points. The population PKPD model consists of several parts including a PK model, drug effect model, meal effect model, and a turnover model. The pharmacokinetic data were described using a 3-compartment model. Drug effect was described by an inhibitory sigmoidal Emax model. Since TG levels change with the introduction of a meal, a bi-exponential meal effect model was utilized. The total change in TG was fitted using a turnover model with drug and meal effects on the TG production rate. The current analysis presents a PKPD modeling strategy of time-varying TG data coming from both endogenous and exogenous sources. In general, the presented model could be utilized in the model-based drug development of drugs that influence TG levels in blood.

A Phase 1 Randomized, Placebo-Controlled Trial With a Topical Inhibitor of Stearoyl-Coenzyme A Desaturase 1 Under Occluded and Nonoccluded Conditions

Stearoyl‐coenzyme A desaturase 1 (SCD‐1) in sebaceous glands is a key enzyme in the synthesis of monounsaturated fatty acids essential for acne development. GSK1940029 gel, a novel SCD‐1 inhibitor, is being developed as a potential treatment for acne. To assess the irritation potential, pharmacokinetics (PK), and safety of topical GSK1940029 to the skin of healthy adults, two interdependent studies were conducted in parallel. Study 1 (n = 54) investigated the irritation potential of GSK1940029 (0.3% and 1%, occluded application) to allow for its application to larger surface areas in study 2 (n = 39), which investigated the safety, tolerability, and PK of GSK1940029 after single and repeat doses as occluded and nonoccluded applications. GSK1940029 was not a primary or cumulative irritant after 2 and 21 days of dosing in study 1. In study 2, single and repeat applications of GSK1940029 (0.1% to 1%) doses were well tolerated with little or no influence on AUC and C_max under occluded or unoccluded conditions. Systemic exposure increased proportionally with surface area and was higher in occluded conditions. Design of these interdependent studies allowed for the assessment of the irritation potential for topical GSK1940029 in parallel with the investigation of PK and safety profiles.

Comparison of vestipitant with ondansetron for the treatment of breakthrough postoperative nausea and vomiting after failed prophylaxis with ondansetron

BACKGROUND

Postoperative nausea and vomiting (PONV) is common; ondansetron is often used as prophylaxis or for breakthrough episodes. Vestipitant is a neurokinin 1 (NK-1) receptor antagonist that is effective for prophylaxis, but its efficacy for treating established PONV is unknown. This study was performed to evaluate the efficacy and safety of vestipitant, compared with ondansetron for the treatment of breakthrough PONV in patients who had already received prophylactic ondansetron before surgery.

METHODS

A multicentre, randomized, single-blind (sponsor-open), parallel group study. Of 527 surgical patients, 130 (25%) had breakthrough PONV and were equally randomized to one of six i.v. doses of vestipitant (4-36 mg) or ondansetron 4 mg. The primary endpoint was the rate of patients exhibiting complete response, defined as no emesis and no further rescue medication from 10 min after infusion up to 24 h after surgery or hospital discharge.

RESULTS

All doses of vestipitant were non-inferior to ondansetron in treating PONV after failed prophylaxis with ondansetron. However, vestipitant was superior to ondansetron in decreasing episodes of postoperative emesis and retching. The complete response rate analysis using Bayesian model averaging indicated that no vestipitant dose was superior to ondansetron. Nausea numerical rating scale scores and the times-to-PONV or discharge were similar between the vestipitant and ondansetron treatment groups.

CONCLUSIONS

Although overall efficacy was non-inferior between vestipitant and ondansetron, the rate of emesis was lower with vestipitant. These data suggest that vestipitant may be a useful agent for the management of PONV, similar to other NK-1 antagonists.

CLINICAL TRIAL REGISTRATION

NCT01507194.

Intravenous Pharmacokinetics, Local Tolerability, and Hemolysis of an SBE7-β-Cyclodextrin Formulation of the Neurokinin-1 Receptor Antagonist Vestipitant

Vestipitant is a potent and selective neurokinin 1 (NK-1) receptor antagonist that was investigated as a potential treatment for post-operative nausea and vomiting (PONV). A previous mannitol-based formulation of vestipitant was associated with hemolytic activity in preclinical studies. In an effort to reduce the hemolytic potential and develop an IV formulation of vestipitant that could be administered more rapidly, an IV formulation containing sulfobutylether-7-beta-cyclodextrin (SBE7-β-CD, Captisol™) was developed and tested in a phase 1 clinical study. This was a randomized, single-blind (subjects and investigator—blinded, sponsor-unblinded), placebo controlled, dose escalation study in healthy subjects in which 7 cohorts of 8 subjects per cohort received SBE7-β-CD -based vestipitant (2 mg/mL) or placebo (saline) in a 3:1 ratio (active:placebo) at different doses and infusion rates. The results demonstrated the ability to infuse up to 48 mg vestipitant in a 2 mg/mL formulation over 30 seconds with no evidence of hemolytic effects. Cohorts of subjects at lower doses and longer infusion duration (>1 minute) reported more AEs related to the infusion site than those at the higher doses and faster infusion rates.

Emerging therapeutic targets in psoriasis

Biopharmaceuticals that target specific disease-mediating molecules have advanced our understanding of the pathogenesis of psoriasis. The traditional paradigm that psoriasis is primarily a disease of epidermal cells has been replaced with a model that now includes keratinocyte-derived factors, inflammatory mediators and angiogenic mechanisms. Recent studies have highlighted some of the key molecules involved in all of these pathogenic processes. Several have already been evaluated as putative targets in in vitro and in vivo studies, whereas other molecules are significantly upregulated in psoriasis and require further study to elucidate their role and contribution to disease. Although not all these molecules will eventually qualify as drug targets, data from similar experimental strategies are predicted to underpin the next generation of candidate targets and novel therapeutic approaches.

Strongyloides stercoralis host-adapted third-stage larvae are the target of eosinophil-associated immune-mediated killing in mice

Host-adapted, transformed, Strongyloides stercoralis third-stage larvae (L3+) were previously found to be antigenically different from free-living, infective, third-stage larvae (L3). These antigenic differences were reproduced by transformation of free-living larvae in tissue culture medium at 37 C over 24 hr. Transformed L3 of both derivations were given as challenge infections in diffusion chambers to naive mice and mice immunized with S. stercoralis L3. Within 12 hr, the challenge infections were killed regardless of whether the L3+ were generated in vitro or in vivo. Eosinophils, previously found to be important in the immune response to S. stercoralis larvae, were recruited into the L3+ microenvironment within 12 hr of challenge infection in immune mice, which supports the previously proposed mechanisms of S. stercoralis larval killing. Thus, S. stercoralis L3+ appear to be targets of the immune response in mice instead of being involved in immune evasion.

Chronicity in Strongyloides stercoralis infections: dichotomy of the protective immune response to infective and autoinfective larvae in a mouse model

Strongyloidiasis is an intestinal disease that can last for decades due to the occurrence of autoinfective larvae (L3a) in an infected person, which contribute to the maintenance of the population of adult worms in the intestine. The goal of the present study was to determine if L3a are susceptible to the protective immunity that targets the infective stage of the worm, the third-stage larvae (L3). Mice immunized and challenged with Strongyloides stercoralis L3 kill more than 90% of challenge larvae contained within diffusion chambers. The L3 do not remain antigenically static in mice, however, but undergo some degree of antigenic change before they are killed, becoming host-activated larvae (L3+). The L3/L3+ are killed in this model system by the combined effects of both parasite-specific IgM and eosinophils. Mice immunized with L3 were able to kill L3/L3+, but did not kill L3a, in challenge infections. Eosinophils were, however, present in diffusion chambers containing L3a, and IgM bound to the surface of L3a. We hypothesized that differential IgM recognition of soluble L3a, L3, and L3+ antigens is the reason why the immune response generated against L3 could not kill L3a. Many common antigens on L3, L3+, and L3a were recognized by serum from mice immunized with L3, as determined by immunoblotting. However, several unique L3, L3+, and L3a antigens were also recognized by immune serum, thus indicating that antigen recognition with IgM antibodies is different between the L3, L3+, and L3a stages. This difference in antigen recognition could explain why L3a are able to evade the immune response that targets L3/L3+ in chronically infected hosts.

Strongyloides stercoralis: role of antibody and complement in immunity to the third stage of larvae in BALB/cByJ mice

Mice immunized against Strongyloides stercoralis L3 were shown to kill greater than 90% of challenge larvae contained within diffusion chambers. The objective of the present study was to identify the host components responsible for immunity. Serum from unprotected, control mice and protected, immune mice in doses of 25-500 microliters was transferred into naive mice at the same time and location as larval challenge. Transfer of as little as 50 microliters of immune serum was able to confer protective immunity. The serum-transferred immunity was ablated by excluding cells from the larval microenvironment or by depleting granulocytes through monoclonal antibody treatment in the recipient mice. Specific antibody isotypes were isolated using protein G and isotype-specific affinity columns. The resulting transfer experiments identified IgM as the isotype responsible for protective immunity to S. stercoralis L3. Antibody binding studies in vivo were performed and only IgM bound to the surface of infective L3 and host-derived L3 (L3+) in immune animals. Elevated levels of C3 were also found bound to the surface of L3/L3+ in immune mice. Cobra venom factor treatment of immunized mice to deplete complement completely eliminated C3 binding to the surface of L3/L3+ and ablated immunity. Therefore, IgM, complement, and granulocytes are necessary for immune elimination of S. stercoralis L3/L3+. Identification of antigens recognized by IgM may help select possible vaccine candidates.

Strongyloides stercoralis: eosinophil-dependent immune-mediated killing of third stage larvae in BALB/cByJ mice

Challenge worm survival was significantly reduced when BALB/cByJ mice were vaccinated against Strongyloides stercoralis infective third stage larvae (L3) regardless of whether the challenge infections consisted of systemically migrating L3 or L3 implanted in diffusion chambers. The only cell type that increased in number in diffusion chambers in immunized mice, 1 week after booster immunizations, was the eosinophil, and maximal levels of eosinophils were coincident with parasite killing. Mice were treated with mAb to eliminate IL-5 or granulocytes to assess the role that eosinophils play in larval killing. Treated animals showed no decrease in immunity when challenge infections consisted of systemically migrating L3 administered 3 weeks after booster immunizations. Eosinophil numbers in immunized mice decreased to control levels when measured 3 weeks post-booster immunization, both in diffusion chambers and in the peripheral blood, whereas they were elevated at 1 week after booster immunizations. Direct contact between host cells and L3 was, however, still required for larval killing in immunized hosts 3 weeks after booster immunizations. Elimination of eosinophils by treatment with mAb to IL-5 or granulocytes significantly reduced protective immunity, when L3 were implanted in diffusion chambers at 1 and 3 weeks post-booster. However, as systemically migrating L3 were still killed in immunized, eosinophil-depleted animals, other cell types may play a role in larval destruction. Two human eosinophil granule products were found to be toxic for host-adapted L3+, but had no effect on infective L3, indicating that host-adapted larvae are possible targets for eosinophil-mediated destruction of third stage larvae. These findings suggest that inactivation of eosinophils by mAb treatment abolishes protective immunity to L3 contained within diffusion chambers and that small numbers of eosinophils are sufficient for immune-mediated killing of S. stercoralis L3.

Structural and molecular specificity of antibody responses in mice immune to third stage larvae of Onchocerca volvulus

Immunization of mice with irradiated Onchocerca volvulus infective stage larvae (L3) has been demonstrated to confer protection against challenge infections with these larvae. Additionally, cytokine level measurements and cytokine depletion studies have shown that both IL-4 and IL-5 are important in generating a protective immune response against O. volvulus challenge infections, thus suggesting a dependency of protective immunity on IgG1, IgE and/or eosinophils. In the present study, we examined the humoral responses of immunized mice to O. volvulus L3 antigens. ELISA measurements of total serum antibody levels indicated that IgE was the only antibody isotype elevated in mice immunized with O. volvulus L3. IgM from immunized mice was the only isotype that recognized surface antigens on intact O. volvulus L3. IgG1, IgG3, IgE and IgA recognized internal parasite antigens on O. volvulus L3 frozen sections. Western blot analysis of L3 proteins showed that in serum from mice immunized with O. volvulus L3 IgG1, IgG2a/2b, IgA, and IgE, as well as IgM, recognized unique L3 proteins. Antibodies in serum from L3 immunized mice were able to detect O. volvulus adult antigens in a pattern similar to the recognition found in O. volvulus L3. Some L3 antigens were shared by adults, while other antigens were L3 specific. The ELISA, immunohistochemistry and Western blot findings thus demonstrate a complex pattern of antigen recognition of parasite antigens by antibodies found in mice immune to the L3 of O. volvulus.

Strongyloides stercoralis: protective immunity to third-stage larvae inBALB/cByJ mice

A murine model system was developed to study the induction and mechanism of protective immunity to L3 of Strongyloides stercoralis. L3 were implanted in BALB/cByJ mice in diffusion chambers constructed with 0.1- or 2.0-microns-pore-size membranes. Parasites survived equally well regardless or membrane type for 7 days, after which larval survival decreased in diffusion chambers constructed with 2.0-microns-pore-size membranes, which allowed host cells to enter. Survival of S. stercoralis L3 in diffusion chambers implanted in mice was assayed after immunization with live, heat-killed, and homogenized L3. Optimal immunization was achieved with 10,000 live L3, whereby immunized mice eliminated 97% of the larvae either contained within diffusion chambers or free within the tissues of the mouse by 24 hr postinfection. Sera from immunized mice had elevated levels of IgG1, IgM, and IgA parasitic-specific antibody; IgM was the only antibody isotype that recognized surface antigens of L3. Larvae were not killed in immunized mice if contact between host cells and the parasites was prevented. In the peripheral blood and diffusion chamber fluid of immunized mice, eosinophil levels were significantly higher when compared to the levels found in control mice. The rodent model developed in the present study has thus demonstrated that virtually complete immunity can be induced to the L3 of S. stercoralis and that larval killing was found to be associated with the presence of both specific antibody and eosinophils.

Genetically engineered bacteria to identify and produce anti-viral agents

We have prepared a strain of Escherichia coli that expresses both the HIV protease and a Tet protein which has been modified to contain the HIV protease recognition sequence. When the protease is expressed, the bacteria will not grow in the presence of tetracycline. However, when the protease is inhibited the bacteria can grow in tetracycline containing media (Block and Grafstrom 1990). We have selected spontaneously arising Tet resistant mutants and have screened them for those that could be producing an inhibitor of HIV protease. The problems in the construction of this strain and the characterization of the various Tetr mutants are discussed.