The COMPARE head-to-head, randomized controlled trial of SEL-212 (pegadricase plus rapamycin-containing nanoparticle, ImmTOR™) versus pegloticase for refractory gout.

OBJECTIVES: Serum urate (SU) lowering with PEGylated uricases in gout can reduce flares and tophi. However, treatment-emergent anti-drug antibodies adversely affect safety and efficacy and the currently approved PEGylated uricase pegloticase requires twice-monthly infusions. Investigational SEL-212 therapy aims to promote uricase-specific tolerance via monthly sequential infusions of a proprietary rapamycin-containing nanoparticle (ImmTOR) and pegadricase. METHODS: COMPARE was a randomized, phase 2, open-label trial of SEL-212 vs pegloticase in adults with refractory gout. SEL-212 [ImmTOR (0.15 mg/kg) and pegadricase (0.2 mg/kg)] was infused monthly or pegloticase (8 mg) twice monthly for 6 months. The primary endpoint was the proportion of participants with SU <6 mg/dl for ≥80% of the time during 3 and 6 months. Secondary outcomes were mean SU, gout flares, number of tender and/or swollen joints and safety. RESULTS: During months 3 and 6 combined, numerically more participants achieved and maintained a SU <6 mg/dl for ≥80% of the time with SEL-212 vs pegloticase (53.0% vs 46.0%, P = 0.181). The percentage reductions in SU levels were statistically greater during months 3 and 6 with SEL-212 vs pegloticase (-73.79% and -47.96%, P = 0.0161). Reductions in gout flare incidence and number of tender and/or swollen joints were comparable between treatments. There were numerical differences between the most common treatment-related adverse events of interest with SEL-212 and pegloticase: gout flares (60.2% vs 50.6%), infections (25.3% vs 18.4%) and infusion-related reactions (15.7% vs 11.5%), respectively. Stomatitis (and related terms) was experienced by eight participants (9.6%) with SEL-212 and none with pegloticase. Stomatitis, a known event for rapamycin, was associated with ImmTOR only. CONCLUSIONS: SEL-212 efficacy and tolerability were comparable to pegloticase in refractory gout. This was associated with a substantial reduction in treatment burden with SEL-212 due to decreased infusion frequency vs pegloticase. CLINICAL TRIAL REGISTRATION: NCT03905512.

Monosodium urate crystal depletion and bone erosion remodeling during pegloticase treatment in patients with uncontrolled gout: Exploratory dual-energy computed tomography findings from MIRROR RCT.

OBJECTIVE: Monosodium-urate (MSU) crystal deposits can be visualized and quantified with dual-energy CT (DECT). Pegloticase lowers serum urate (SU) in uncontrolled gout patients, with methotrexate (MTX) co-therapy recommended to increase SU-lowering response rate and decrease infusion reaction risk. The literature on serial DECT-imaging during pegloticase+MTX co-therapy is sparse, with only 2 prior cases of rapid MSU deposition depletion with subsequent bone-erosion remodeling reported from a small open-label trial. Here, we report DECT findings during pegloticase treatment in a larger number of patients from a randomized controlled trial to confirm bone-erosion remodeling that follows MSU depletion with pegloticase. The influence of length-of-therapy is also explored. METHODS: Patients received pegloticase (8mg every 2weeks)+MTX (15mg/week orally) or pegloticase+placebo (PBO) during the MIRROR RCT trial. A subset underwent DECT-imaging on Day1 (first pegloticase infusion) and at Weeks 14, 24, and 52. Patients with paired baseline-Week 52 images were included. Imaged regions with baseline MSU-crystal volume (VMSU)<0.5cm3 were excluded to minimize artifact contributions. VMSU and bone-erosion remodeling were assessed. RESULTS: Eight patients (6 MTX, 2 PBO) were included. Included patients had received 52weeks (5 MTX), 42weeks (1 PBO), and 6weeks (1 MTX, 1 PBO) of pegloticase therapy. Patients who prematurely discontinued pegloticase maintained SU<6mg/dL on allopurinol (n=2)/febuxostat (n=1). At Week 52, VMSU had markedly decreased in both the pegloticase+MTX and pegloticase+PBO treatment groups, with faster depletion during pegloticase therapy. Bone-erosion remodeling was observed in 29/42 (69%) evaluated erosions: 29 (69%) size decrease, 4 (9.5%) recortication, 3 (7.1%) new bone formation. CONCLUSION: Rapid VMSU depletion during pegloticase therapy was observed with concomitant bone remodeling within 1year. Following pegloticase discontinuation, VMSU reduction slowed or stopped even when SU was maintained<6mg/dL with oral ULT. CLINICAL TRIAL REGISTRATION: NCT03994731.

Targeting Drugs to Larval Zebrafish Macrophages by Injecting Drug-Loaded Liposomes.

Zebrafish (Danio rerio) larvae have developed into a popular model to investigate host-pathogen interactions and the contribution of innate immune cells to inflammatory disease due to their functionally conserved innate immune system. They are also widely used to examine how innate immune cells help guide developmental processes. By taking advantage of the optical transparency and genetic tractability of larval zebrafish, these studies often focus on live imaging approaches to functionally characterize fluorescently marked macrophages and neutrophils within intact animals. Due to their diverse functional heterogeneity and ever-expanding roles in disease pathogenesis, macrophages have received significant attention. In addition to genetic manipulations, chemical interventions are now routinely used to manipulate and examine macrophage behavior in larval zebrafish. Delivery of these drugs is typically limited to passive targeting of free drug through direct immersion or microinjection. These approaches rely on the assumption that any changes to macrophage behavior are the result of a direct effect of the drug on the macrophages themselves, and not a downstream consequence of a direct effect on another cell type. Here, we present our protocols for targeting drugs specifically to larval zebrafish macrophages by microinjecting drug-loaded fluorescent liposomes. We reveal that poloxamer 188-modified drug-loaded blue fluorescent liposomes are readily taken up by macrophages, and not by neutrophils. We also provide evidence that drugs delivered in this way can impact macrophage activity in a manner consistent with the mechanism of action of the drug. This technique will be of value to researchers wanting to ensure targeting of drugs to macrophages and when drugs are too toxic to be delivered by traditional methods like immersion.

Bovine bone particulates containing bone anabolic factors as a potential xenogenic bone graft substitute.

BACKGROUND: Alternative grafts are needed to improve the healing of bone non-union. Here, we assessed a bovine bone product which retains the inorganic and organic components of bone, as an alternative bone graft. METHODS: Bovine bone matrix proteins (BBMPs) were isolated from bovine bone particulates (BBPs) and tested in vitro. Primary rat osteoblast viability, differentiation, and mineralisation were assessed with alamarBlue®, real-time PCR, and von Kossa staining assays, respectively. Osteoclast formation was assessed in primary murine bone marrow cultures with TRAP staining. Human osteoblast growth and differentiation in the presence of BBPs was evaluated in 3D collagen gels in vitro using alamarBlue® and real-time PCR, respectively. The efficacy of BBPs as an alternative bone graft was tested in a rat critical-size calvarial defect model, with histology scored at 4 and 12 weeks post-surgery. RESULTS: In vitro, the highest concentration of BBMPs increased mineral deposition five-fold compared to the untreated control group (P < 0.05); enhanced the expression of key osteoblast genes encoding for RUNX2, alkaline phosphatase, and osteocalcin (P < 0.05); and decreased osteoclast formation three-fold, compared to the untreated control group (P < 0.05). However, the BBPs had no effect on primary human osteoblasts in vitro, and in vivo, no difference was found in healing between the BBP-treated group and the untreated control group. CONCLUSIONS: Overall, despite the positive effects of the BBMPs on the cells of the bone, the bovine bone product as a whole did not enhance bone healing. Finding a way to harness the positive effect of these BBMPs would provide a clear benefit for healing bone non-union.

Liposome-Mediated Drug Delivery in Larval Zebrafish to Manipulate Macrophage Function.

Chemical interventions are regularly used to examine and manipulate macrophage function in larval zebrafish. Given chemicals are typically administered by simple immersion or injection, it is not possible to resolve whether their impact on macrophage function is direct or indirect. Liposomes provide an attractive strategy to target drugs to specific cellular compartments, including macrophages. As an example, injecting liposomal clodronate into animal models, including zebrafish, is routinely used to deliver toxic levels of clodronate specifically to macrophages for targeted cell ablation. Here we show that liposomes can also target the delivery of drugs to zebrafish macrophages to selectively manipulate their function. We utilized the drugs etomoxir (a fatty acid oxidation inhibitor) and MitoTEMPO (a scavenger of mitochondrial reactive oxygen species [mROS]), that we have previously shown, through free drug delivery, suppress monosodium urate (MSU) crystal-driven macrophage activation. We generated poloxamer 188 modified liposomes that were readily phagocytosed by macrophages, but not by neutrophils. Loading these liposomes with etomoxir or MitoTEMPO and injecting into larvae suppressed macrophage activation in response to MSU crystals, as evidenced by proinflammatory cytokine expression and macrophage-driven neutrophil recruitment. This work reveals the utility of packaging drugs into liposomes as a strategy to selectively manipulate macrophage function.

Advances in pharmacotherapy for the treatment of gout.

INTRODUCTION: Gout is a common inflammatory arthritis affecting almost 6% of US males and 2% of US females. The central cause of gout is deposition of monosodium urate crystals, and the focus of treatment is aimed at crystal dissolution using urate-lowering therapy. AREAS COVERED: The review describes the current treatments for urate-lowering therapy including allopurinol, febuxostat, probenecid, benzbromarone and pegloticase. Anti-inflammatory treatment of acute flares and prophylaxis of flares with NSAIDs, colchicine, corticosteroids and anti-IL-1 agents is also reviewed. In addition, drugs in Phase III clinical trials for gout indications are reviewed. EXPERT OPINION: In the last decade, there has been major progress in the pharmacotherapy of gout. Management guidelines have emphasized the importance of a therapeutic serum urate target for effective gout management. Studies have identified the safe and effective dosing strategies for 'old' drugs such as allopurinol and colchicine. New therapeutic agents have been developed and approved for both urate-lowering therapy and anti-inflammatory treatment of acute flares. However, quality of care remains a major challenge in gout management, and strategies to ensure best practice require further focus to ensure that the progress of the last decade translates into clinical benefit for people with gout.

Exploratory study of radiographic change in patients with tophaceous gout treated with intensive urate-lowering therapy.

OBJECTIVE: Tophi are strongly associated with structural damage in gout, and urate-lowering therapy reduces tophus size. Pegloticase leads to dramatic reductions in serum urate and subcutaneous tophi in treatment responders. The aim of this analysis was to examine whether profound urate lowering can alter radiographic findings in gout. METHODS: Serial plain radiographs of the hands and feet were obtained from 8 patients with tophaceous gout treated with pegloticase. Radiographs were scored for erosion and joint space narrowing (JSN) according to the gout-modified Sharp/van der Heijde method. Scorers were blinded to each other's scores and to the clinical characteristics of the patients (including the clinical response to pegloticase). A detailed qualitative site-by-site analysis was undertaken to define additional changes observed from baseline. RESULTS: All patients experienced a profound urate-lowering response (serum urate level <1 mg/dl) during pegloticase treatment. For the entire group, the median total radiographic scores reduced from 69.25 (range 1.5-138) at baseline to 57.25 (range 1.5-110) at 12 months (P = 0.02). Median erosion scores reduced over 1 year (P = 0.008), but JSN scores did not change (P = 0.50). Further reductions were observed in total scores and erosion scores in 5 patients with 24-month followup films (one-way analysis of variance P = 0.009 for total score, 0.02 for erosion, and 0.95 for JSN). Qualitative site-by-site analysis identified regression of soft tissue masses, increased sclerosis, and filling in of erosions in the followup films. CONCLUSION: This exploratory study suggests that profound urate lowering can lead to improvement in structural damage, particularly bone erosion, in patients with tophaceous gout.