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To assess efficacy, safety, pharmacokinetics, and immunogenicity of pegloticase plus methotrexate (MTX) versus pegloticase plus placebo cotreatment for uncontrolled gout in a randomized, placebo-controlled, double-blind trial.This study included adults with uncontrolled gout, defined as serum urate ≥7 mg/dl, oral urate-lowering therapy failure or intolerance, and presence of ongoing gout symptoms including ≥1 tophus, ≥2 flares in the past 12 months, or gouty arthritis. Key exclusion criteria included MTX contraindication, current immunosuppressant use, G6PDH deficiency, and estimated glomerular filtration rate40 ml/minute/1.73 mA total of 152 patients were randomized, 100 to receive pegloticase plus MTX, 52 to receive pegloticase plus placebo. Significantly higher treatment response occurred during month 6 in the MTX group versus the placebo group (71.0% [71 of 100 patients] versus 38.5% [20 of 52 patients], respectively; between-group difference 32.3% [95% confidence interval 16.3%, 48.3%]) (P 0.0001 for between-group difference). During the first 6 months of pegloticase plus MTX or pegloticase plus placebo treatment, 78 (81.3%) of 96 MTX patients versus 47 (95.9%) of 49 placebo patients experienced ≥1 adverse event (AE), most commonly gout flare (64 [66.7%] of 96 MTX patients and 34 [69.4%] of 49 placebo patients). Reports of AEs and serious AEs were comparable between groups, but the infusion reaction rate was considerably lower with MTX cotherapy (4.2% [4 of 96 MTX patients, including 1 patient who had anaphylaxis]) than with placebo cotherapy (30.6% [15 of 49 placebo patients, 0 who had anaphylaxis]) (P 0.001). Antidrug antibody positivity was also lower in the MTX group.MTX cotherapy markedly increased pegloticase response rate over placebo (71.0% versus 38.5%) during month 6 with no new safety signals. These findings verify higher treatment response rate, lower infusion reaction incidence, and lower immunogenicity when pegloticase is coadministered with MTX.

Background and Objective Thyroid eye disease (TED) is characterized by inflammation/expansion of orbital tissues, proptosis, and diplopia. Teprotumumab is the first US Food and Drug Administration-approved therapy for TED, administered as an initial intravenous infusion of 10 mg/kg followed by 20 mg/kg every 3 weeks for an additional seven infusions. The objective of this article is to discuss the pharmacokinetics and exposure-response profile for teprotumumab in patients with TED. Methods A population pharmacokinetic analysis was performed to characterize pharmacokinetics and select dosing in patients with TED. Exposure-response was evaluated for efficacy (proptosis response, clinical activity score categorical response, and diplopia response) and safety (hyperglycemia, muscle spasms, and hearing impairment) parameters. Results Teprotumumab pharmacokinetics was linear in patients with TED, with low systemic clearance (0.334 L/day), low volume of distribution (3.9 and 4.2 L for the central and peripheral compartment, respectively), and a long elimination half-life (19.9 days). The approved dosing regimen provided > 20 µg/mL for > 90% insulin-like growth factor 1 receptor saturation throughout the dosing interval. Model-predicted mean (± standard deviation) steady-state area under the concentration-time curve, peak, and trough concentrations in patients with TED were 131 (± 30.9) mg∙h/mL, 643 (± 130) µg/mL, and 157 (± 50.6) µg/mL, respectively. Female patients had a 15% higher steady-state peak concentration but a similar steady-state area under the concentration-time curve vs male patients. No other covariates affected teprotumumab pharmacokinetics. No meaningful correlations between teprotumumab exposures and efficacy or safety parameters were observed. Conclusions Teprotumumab pharmacokinetics was well characterized in patients with TED, and generally consistent with other IgG1 antibodies. Efficacy was consistent across the exposure range with a well-tolerated safety profile supporting the current dose regimen for patients with TED. Supplementary Information The online version contains supplementary material available at 10.1007/s40262-021-01003-3.

Background and aims GS-9688 (selgantolimod) is an oral selective small molecule agonist of toll-like receptor 8 in clinical development for the treatment of chronic hepatitis B. In this study, we evaluated the antiviral efficacy of GS-9688 in woodchucks chronically infected with woodchuck hepatitis virus (WHV), a hepadnavirus closely related to hepatitis B virus. Approach and results WHV-infected woodchucks received eight weekly oral doses of vehicle, 1 mg/kg GS-9688, or 3 mg/kg GS-9688. Vehicle and 1 mg/kg GS-9688 had no antiviral effect, whereas 3 mg/kg GS-9688 induced a >5 log10 reduction in serum viral load and reduced WHV surface antigen (WHsAg) levels to below the limit of detection in half of the treated woodchucks. In these animals, the antiviral response was maintained until the end of the study (>5 months after the end of treatment). GS-9688 treatment reduced intrahepatic WHV RNA and DNA levels by >95% in animals in which the antiviral response was sustained after treatment cessation, and these woodchucks also developed detectable anti-WHsAg antibodies. The antiviral efficacy of weekly oral dosing with 3 mg/kg GS-9688 was confirmed in a second woodchuck study. The antiviral response to GS-9688 did not correlate with systemic GS-9688 or cytokine levels but was associated with transient elevation of liver injury biomarkers and enhanced proliferative response of peripheral blood mononuclear cells to WHV peptides. Transcriptomic analysis of liver biopsies taken prior to treatment suggested that T follicular helper cells and various other immune cell subsets may play a role in the antiviral response to GS-9688. Conclusions Finite, short-duration treatment with a clinically relevant dose of GS-9688 is well tolerated and can induce a sustained antiviral response in WHV-infected woodchucks; the identification of a baseline intrahepatic transcriptional signature associated with response to GS-9688 treatment provides insights into the immune mechanisms that mediate this antiviral effect.

Background: Publications suggest immunomodulation co-therapy improves responder rates in uncontrolled/refractory gout patients undergoing pegloticase treatment. The MIRROR open-label trial showed a 6-month pegloticase+methotrexate co-therapy responder rate of 79%, compared to an established 42% pegloticase monotherapy responder rate. Longer-term efficacy/safety data are presented here.Methods: Uncontrolled gout patients (serum urate [SU]≥6 mg/dL and SU≥6 mg/dL despite urate-lowering therapy [ULT], ULT intolerance, or functionally-limiting tophi) were included. Patients with immunocompromised status, G6PD deficiency, severe kidney disease, or methotrexate contraindication were excluded. Oral methotrexate (15 mg/week) and folic acid (1 mg/day) were administered 4-weeks before and during pegloticase therapy. Twelve-month responder rate (SUResults: Fourteen patients were included (all male, 49.3 ± 8.7 years, 13.8 ± 7.4 year gout history, pre-therapy SU: 9.2 ± 2.5 mg/dL). Three patients were non-responders and discontinued study treatment before 24-weeks, one patient exited the study per-protocol at 24-weeks (enrolled prior to treatment extension amendment), and 10 remained in study through Week 52. Of the 10, 8 completed 52-weeks of pegloticase+methotrexate and were 12-month responders. The remaining two discontinued pegloticase+methotrexate at Week 24 (met treatment goals) and stayed in study under observation (allopurinol prescribed at physicians’ discretion); one remained a responder at 12-months. At 52-weeks, change from baseline in SU was -8.2 ± 4.1 mg/dL (SU: 1.1 ± 2.4 mg/dL, n=10). Gout flares were common early in treatment but progressively decreased while on therapy (Weeks 1-12: 13/14 [92.9%], Weeks 36-52: 2/8 [25.0%]). One patient recovered from sepsis (serious AE). Two non-responders developed high ADA titres; fewer patients had trough concentrations (Cmin) below quantitation limit (BQL) and median Cmin was higher (1.03 mg/mL vs. BQL) than in pegloticase monotherapy trials.Conclusions: Methotrexate+pegloticase co-therapy was well-tolerated over 12-months, with sustained SU lowering, progressive gout flare reduction, and no new safety concerns. Antibody/PK findings suggest methotrexate attenuates ADA formation, coincident with higher treatment response rates.Trial registration: ClinicalTrials.gov: NCT03635957, registered 17 August 2018, https://clinicaltrials.gov/ct2/show/NCT03635957

Introduction: Teprotumumab treatment resulted in statistically and clinically meaningful improvements across multiple facets of active TED and was generally well-tolerated in Phase 2 and 3 trials.1,2 An initial intravenous infusion of 10 mg/kg followed by 20 mg/kg every 3 weeks was selected based on in vitro activity and clinical PK profile, to maintain pharmacologically active exposures and >90% saturation of IGF-1R over dosing intervals and to achieve efficacy at a well-tolerated dose for this vision-threatening disease. Methods: Population PK analysis were performed on data from a Phase 1 oncology study (n=60)3 and Phase 2 and 3 trials in active TED (N=83)2,3 and covariate effect on PK was assessed. Exposure-response relationship was evaluated in TED studies for key efficacy endpoints (proptosis response rate, % patients with a clinical activity score value of 0 or 1, and diplopia responder rate) and selected safety variables (hyperglycemia and muscle spasms). Results: Teprotumumab PK was linear in TED patients and consistent with other immunoglobulin G1 monoclonal antibodies (IgG1 mAbs), with low systemic clearance (0.334 L/day), low volume of distribution (3.9 L for central compartment and 4.2 L for peripheral compartment), and long elimination half-life (19.9 days). 4,5 Model-predicted mean (± standard deviation) steady-state area under the concentration curve (AUCss), peak (Cmax,ss), and trough (Cmin,ss) concentrations in TED patients were 131 (± 30.9) mg∙hr/mL, 643 (± 130) µg/mL and 157 (± 50.6) µg/mL, respectively, suggesting low inter-subject variability. Population PK analysis indicated no significant impact of baseline age, gender, race, weight, smoking status, renal impairment (mild/moderate), and hepatic function (total bilirubin, aspartate and alanine aminotransferases) on teprotumumab PK. Female patients had 15% higher Cmax,ss but similar AUC compared to male patients, which is not considered clinically relevant. Exposure-response analysis from the TED dose regimen indicated no meaningful correlations between exposures (AUCss, Cmax,ss and Cmin,ss) and key efficacy endpoints or selected safety variables, supporting the demonstrated, favorable benefit-risk profile of the TED dose regimen.2 Conclusion: Teprotumumab PK was characterized in TED patients by long elimination half-life, low systemic clearance and low volume of distribution, consistent with other IgG1 mAbs. There was no meaningful exposure-response relationship at the selected TED dose regimen for both efficacy and safety endpoints, supporting the teprotumumab dose regimen used in TED patients. Reference: (1) Smith TJ, et al. N Engl J Med 2017;376:1748-1761. (2) Douglas RS, et al. AACE 2019 late-breaking abstract. (3) ClinicalTrials.gov: NCT00400361. (4) Dirks NL et al. Clin Pharmacokinet. 2010;49(10):633-59. (5) Ryman JT et al. CPT Pharmacometrics Syst Pharmacol. 2017;6(9):576-88.

We took advantage of the proliferative and permissive environment of the developing preimmune fetus to develop a noninjury large animal model in sheep, in which the transplantation of defined populations of human hematopoietic stem cells resulted in the establishment of human hematopoiesis and led to the formation of significant numbers of long-lasting, functional human liver cells, with some animals exhibiting levels as high as 20% of donor (human) hepatocytes 11 months after transplantation. A direct correlation was found between hepatocyte activity and phenotype of transplanted cells, cell dose administered, source of cells used on a cell-per-cell basis (bone marrow, cord blood, mobilized peripheral blood), and time after transplantation. Human hepatocytes generated in this model retained functional properties of normal hepatocytes, constituted hepatic functional units with the presence of human endothelial and biliary duct cells, and secreted human albumin that was detected in circulation. Transplanting populations of hematopoietic stem cells can efficiently generate significant numbers of functional hepatic cells in this noninjury large animal model and thus could be a means of ameliorating or curing genetic diseases in which a deficiency of liver cells or their products threatens the life of the fetus or newborn.

Background— We have investigated the usefulness of a model of cardiac development in a large mammal, sheep, for studies of engraftment of human stem cells in the heart. Methods and Results— Adult and fetal human mesenchymal stem cells were injected intraperitoneally into sheep fetuses in utero. Hearts at late fetal development were analyzed for engraftment of human cells. The majority of the engrafted cells of human origin formed segments of Purkinje fibers containing exclusively human cells. There were no differences in engraftment of human mesenchymal stem cells from adult bone marrow, fetal brain, and fetal liver. On average, 43.2% of the total Purkinje fibers in random areas (n=11) of both ventricles were of human origin. In contrast, ≈0.01% of cardiomyocytes were of human origin. Conclusions— Human mesenchymal stem cells preferentially engraft at high levels in the ventricular conduction system during fetal development in sheep. These findings raise the possibility that stem cells contribute to normal development of the fetal heart.

Alternative methods to whole liver transplantation require a suitable cell that can be expanded to obtain sufficient numbers required for successful transplantation while maintaining the ability to differentiate into hepatocytes. Mesenchymal stem cells (MSCs) possess several advantageous characteristics for cell-based therapy and have been shown to be able to differentiate into hepatocytes. Thus, we investigated whether the intrahepatic delivery of human MSCs is a safe and effective method for generating human hepatocytes and whether the route of administration influences the levels of donor-derived hepatocytes and their pattern of distribution throughout the parenchyma of the recipient's liver. Human clonally derived MSCs were transplanted by an intraperitoneal (n = 6) or intrahepatic (n = 6) route into preimmune fetal sheep. The animals were analyzed 56–70 days after transplantation by immunohistochemistry, enzyme-linked immunosorbent assay, and flow cytometry. The intrahepatic injection of human MSCs was safe and resulted in more efficient generation of hepatocytes (12.5% ± 3.5% versus 2.6% ± 0.4%). The animals that received an intrahepatic injection exhibited a widespread distribution of hepatocytes throughout the liver parenchyma, whereas an intraperitoneal injection resulted in a preferential periportal distribution of human hepatocytes that produced higher amounts of albumin. Furthermore, hepatocytes were generated from MSCs without the need to first migrate/lodge to the bone marrow and give rise to hematopoietic cells. Conclusion: Our studies provide evidence that MSCs are a valuable source of cells for liver repair and regeneration and that, by the alteration of the site of injection, the generation of hepatocytes occurs in different hepatic zones, suggesting that a combined transplantation approach may be necessary to successfully repopulate the liver with these cells. (HEPATOLOGY 2007.)

Objective To study the early time course of engraftment of human mesenchymal stem cells in fetal sheep heart and determine the relative roles of proliferation and homing in formation of aggregates of human Purkinje fiber cells. Methods The human sheep xenograft model was utilized for these studies. Prior to injection in the preimmune fetus, human cells were labeled with fluorescent dyes to be able to track human cells at early times of engraftment. Results Human stem cells were detected in fetal hearts between 29 and 39 hours after intraperitoneal injection. Engraftment was primarily in the Purkinje fiber system. By 45 hours engrafted human cells had a cardiac phenotype. When two groups of human mesenchymal stem cells, each labeled with a different fluorescent dye, were combined prior to injection, aggregates of human Purkinje fiber cells contained cells labeled with either one dye or the other, no aggregate contained cells labeled with both dyes. Conclusions Human mesenchymal stem cells introduced into fetal sheep rapidly enter the myocardium. The swift differentiation into a cardiac phenotype indicates that the cardiac milieu has a strong influence on the fate of engrafting human mesenchymal stem cells. The absence of any aggregates of human Purkinje fiber cells containing both fluorescent dyes demonstrates that each aggregate of human Purkinje fiber cells is derived from a single mesenchymal stem cell and not from homing of multiple cells to a hotspot.

We have previously reported the isolation of Stro-1+, CD45-, GlyA-human MSC from human bone marrow (BM), liver (LV), and brain (BR). Despite their similar morphology and phenotype, these cells, upon in vivo transplantation into the pre-immune fetal sheep model, seemed to differentiate more efficiently into cells of their tissue of origin. For instance, all 3 sources of MSC gave rise to blood, with average levels of human CD45+ cells in chimeric animals of 8.7% for LVMSC, 3.3% for BRMSC, and 4.5%for BMMSC. Human neural cells were also detected in the brain of transplanted animals with the highest levels obtained with BRMSC (1.33%) and lowest with LVMSC (0.4%). However, BRMSC generated very few human hepatocytes (2–10 hepatocytes/section), while both LVMSC and BMMSC gave rise to much higher levels of hepatocytes. This led us to hypothesize that despite the similar phenotype, the proteome makeup of MSC from different tissues may be distinct. To test this hypothesis, we examined the commonalities and differences in the protein repertoire of cultured MSC from these 3 different sources. The eighty most prominent protein spots from the 2-D gel of each cell population were removed and identified by MOLDI-TOF/TOF mass spectroscopy after Trypsin digestion. Our results demonstrate that there are a large number of common proteins between the LV, BM and BR MSC (> 75%). Besides the cytoskeletal and associative proteins such as Vimentin, β-actin, cofilin, Tropomyosin and Lamin A/C, the cells contained a large quantity of proteins for protein processing such as Cyclophilin A, Endoplasmic reticulum protein ERp29, Disulfide-isomerase ER60 and Glucose-regulated proteins 75 and 78, which may be important for the broad differentiative potential of MSC. Despite these similarities, forty percent of the identified proteins showed significantly different expression levels between the three types of cells (> 300%), the majority of which were not proteins previously shown to be BM-, Liver or Brain-specific. Interestingly, however, LV-derived cells contained a 5-fold greater concentration of Albumin than BM or Brain cells, which may explain their greater tendency to form liver tissue in vivo. Likewise, since BMMSC were enriched in smooth muscle associated proteins, potentially they may constitute a better source to be used for muscle repair. Thus, the definition of the different MSC proteomes can lead not only to the discover of critical differences involved in differentiation/plasticit into different cell fates, but may also help us to identify distinct cell populations that are ideally suited for cell therapies for specific organs.

The ability of bone marrow-derived Hematopoietic and Mesenchymal Stem Cells (MSC) to generate hepatocytes in a large non-injury sheep model of human stem cell transplantation has been demonstrated. Although in our sheep model the liver is still a hematopoietic organ at the time of transplantation, we hypothesized that the human BM-derived MSCs migrated preferentially to the BM, thus leaving few MSCs available to lodge in the liver and give rise to hepatocytes. Thus, in the present studies, we compared the ability and efficiency of clonally-derived BM MSC populations to give rise to liver cells upon either intra-hepatic (IH) or intra-peritoneal (IP) transplantation into fetal sheep. Five MSC clones were established from human adult BM by single cell deposition of Stro-1+ Gly-A-CD45- cells and expanded until sufficient cells were obtained. Phenotypic characterization demonstrated that all clones were positive for CD90, CD13, and CD29, and negative for hematopoietic markers such as CD34, CD133, and CD45. Five different clonal populations were used and each clone was transplanted either IP (n=7) or IH (n=6) into 55-60 days old fetal sheep recipients at 5x105cells/fetus. Evaluation of the recipients at 56-70 days post-transplant showed that clonally-derived MSC were not only able to generate hepatocytes, but they were also able to generate hematopoietic cells detectable both in the BM and in the PB. IP transplanted animals had a significantly higher level of human CD45+ in their BM (CD45=2.7±0.4%) compared to the IH transplanted animals (CD45=0.25±0.05%), demonstrating that IP injection favors the homing of these cells to the BM while upon IH injection, the human blood cells generated remain in circulation (2.6% CD45+). When we evaluated the presence of hematopoietic cells in the livers of these animals, the IP transplanted animals contained almost 2% CD45+ cells within their livers, while IH transplanted animals had levels of only 0.5-0.65%. When we looked at the generation of liver cells in both groups of animals by immunohistochemistry using monoclonal antibodies specific for human hepatocytes and albumin, we observed that IH injection was much more efficient at generating human hepatocytes than IP injection. The levels of human hepatocytes in most of the IH transplanted animals (10-15% positive cells) were roughly 5X higher than their IP counterparts (2.5-3%). Furthermore, human hepatocytes produced following IH injection were widely distributed throughout the liver parenchyma, while IP injection resulted in a periportal pattern of human hepatocytic activity. We also confirmed the functionality of the generated hepatocytes by detecting human albumin in circulation in these animals by ELISA. In conclusion, these studies show that in a non-injury model the number of available donor cells reaching the liver can be controlled by altering the route of administration, and that this availability determines both the levels of donor-derived hepatocytes generated and the pattern of distribution of these hepatocytes throughout the recipient liver.