IRX4204 Induces Senescence and Cell Death in HER2-positive Breast Cancer and Synergizes with Anti-HER2 Therapy.

PURPOSE: Rexinoids, agonists of nuclear retinoid X receptor (RXR), have been used for the treatment of cancers and are well tolerated in both animals and humans. However, the usefulness of rexinoids in treatment of breast cancer remains unknown. This study examines the efficacy of IRX4204, a highly specific rexinoid, in breast cancer cell lines and preclinical models to identify a biomarker for response and potential mechanism of action. EXPERIMENTAL DESIGN: IRX4204 effects on breast cancer cell growth and viability were determined using cell lines, syngeneic mouse models, and primary patient-derived xenograft (PDX) tumors. In vitro assays of cell cycle, apoptosis, senescence, and lipid metabolism were used to uncover a potential mechanism of action. Standard anti-HER2 therapies were screened in combination with IRX4204 on a panel of breast cancer cell lines to determine drug synergy. RESULTS: IRX4204 significantly inhibits the growth of HER2-positive breast cancer cell lines, including trastuzumab and lapatinib-resistant JIMT-1 and HCC1954. Treatment with IRX4204 reduced tumor growth rate in the MMTV-ErbB2 mouse and HER2-positive PDX model by 49% and 44%, respectively. Mechanistic studies revealed IRX4204 modulates lipid metabolism and induces senescence of HER2-positive cells. In addition, IRX4204 demonstrates additivity and synergy with HER2-targeted mAbs, tyrosine kinase inhibitors, and antibody-drug conjugates. CONCLUSIONS: These findings identify HER2 as a biomarker for IRX4204 treatment response and demonstrate a novel use of RXR agonists to synergize with current anti-HER2 therapies. Furthermore, our results suggest that RXR agonists can be useful for the treatment of anti-HER2 resistant and metastatic HER2-positive breast cancer.

End binding-3 inhibitor activates regenerative program in age-related macular degeneration.

Wet age-related macular degeneration (AMD), characterized by leaky neovessels emanating from the choroid, is a main cause of blindness. As current treatments for wet AMD require regular intravitreal injections of anti-vascular endothelial growth factor (VEGF) biologics, there is a need for the development of less invasive treatments. Here, we designed an allosteric inhibitor of end binding-3 (EB3) protein, termed EBIN, which reduces the effects of environmental stresses on endothelial cells by limiting pathological calcium signaling. Delivery of EBIN via eye drops in mouse and non-human primate (NHP) models of wet AMD prevents both neovascular leakage and choroidal neovascularization. EBIN reverses the epigenetic changes induced by environmental stresses, allowing an activation of a regenerative program within metabolic-active endothelial cells comprising choroidal neovascularization (CNV) lesions. These results suggest the therapeutic potential of EBIN in preventing the degenerative processes underlying wet AMD.

A novel retinoic acid receptor-γ agonist antagonizes immune checkpoint resistance in lung cancers by altering the tumor immune microenvironment.

All-trans-retinoic acid (ATRA), the retinoic acid receptors (RARs) agonist, regulates cell growth, differentiation, immunity, and survival. We report that ATRA-treatment repressed cancer growth in syngeneic immunocompetent, but not immunodeficient mice. The tumor microenvironment was implicated: CD8+ T cell depletion antagonized ATRA's anti-tumorigenic effects in syngeneic mice. ATRA-treatment with checkpoint blockade did not cooperatively inhibit murine lung cancer growth. To augment ATRA's anti-tumorigenicity without promoting its pro-tumorigenic potential, an RARγ agonist (IRX4647) was used since it regulates T cell biology. Treating with IRX4647 in combination with an immune checkpoint (anti-PD-L1) inhibitor resulted in a statistically significant suppression of syngeneic 344SQ lung cancers in mice-a model known for its resistance to checkpoints and characterized by low basal T cell and PD-L1 expression. This combined treatment notably elevated CD4+ T-cell presence within the tumor microenvironment and increased IL-5 and IL-13 tumor levels, while simultaneously decreasing CD38 in the tumor stroma. IL-5 and/or IL-13 treatments increased CD4+ more than CD8+ T-cells in mice. IRX4647-treatment did not appreciably affect in vitro lung cancer growth, despite RARγ expression. Pharmacokinetic analysis found IRX4647 plasma half-life was 6 h in mice. Yet, RARα antagonist (IRX6696)-treatment with anti-PD-L1 did not repress syngeneic lung cancer growth. Together, these findings provide a rationale for a clinical trial investigating an RARγ agonist to augment check point blockade response in cancers.

Preserving and enhancing mitochondrial function after stroke to protect and repair the neurovascular unit: novel opportunities for nanoparticle-based drug delivery.

The neurovascular unit (NVU) is composed of vascular cells, glia, and neurons that form the basic component of the blood brain barrier. This intricate structure rapidly adjusts cerebral blood flow to match the metabolic needs of brain activity. However, the NVU is exquisitely sensitive to damage and displays limited repair after a stroke. To effectively treat stroke, it is therefore considered crucial to both protect and repair the NVU. Mitochondrial calcium (Ca2+) uptake supports NVU function by buffering Ca2+ and stimulating energy production. However, excessive mitochondrial Ca2+ uptake causes toxic mitochondrial Ca2+ overloading that triggers numerous cell death pathways which destroy the NVU. Mitochondrial damage is one of the earliest pathological events in stroke. Drugs that preserve mitochondrial integrity and function should therefore confer profound NVU protection by blocking the initiation of numerous injury events. We have shown that mitochondrial Ca2+ uptake and efflux in the brain are mediated by the mitochondrial Ca2+ uniporter complex (MCUcx) and sodium/Ca2+/lithium exchanger (NCLX), respectively. Moreover, our recent pharmacological studies have demonstrated that MCUcx inhibition and NCLX activation suppress ischemic and excitotoxic neuronal cell death by blocking mitochondrial Ca2+ overloading. These findings suggest that combining MCUcx inhibition with NCLX activation should markedly protect the NVU. In terms of promoting NVU repair, nuclear hormone receptor activation is a promising approach. Retinoid X receptor (RXR) and thyroid hormone receptor (TR) agonists activate complementary transcriptional programs that stimulate mitochondrial biogenesis, suppress inflammation, and enhance the production of new vascular cells, glia, and neurons. RXR and TR agonism should thus further improve the clinical benefits of MCUcx inhibition and NCLX activation by increasing NVU repair. However, drugs that either inhibit the MCUcx, or stimulate the NCLX, or activate the RXR or TR, suffer from adverse effects caused by undesired actions on healthy tissues. To overcome this problem, we describe the use of nanoparticle drug formulations that preferentially target metabolically compromised and damaged NVUs after an ischemic or hemorrhagic stroke. These nanoparticle-based approaches have the potential to improve clinical safety and efficacy by maximizing drug delivery to diseased NVUs and minimizing drug exposure in healthy brain and peripheral tissues.

Targeting the Retinoid X Receptor Pathway Prevents and Ameliorates Murine Chronic Graft-Versus-Host Disease.

Most allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients receive peripheral blood stem cell grafts resulting in a 30%-70% incidence of chronic graft-versus-host disease (cGVHD), a major cause of mortality and morbidity in long-term survivors. While systemic steroids remain the standard of care for first-line therapy, patients may require long-term administration, and those with steroid-resistant or refractory cGVHD have a worse prognosis. Although durable and deep responses with second-line therapies can be achieved in some patients, there remains an urgent need for new therapies. In this study, we evaluated the efficacy of IRX4204, a novel agonist that activates RXRs and is in clinical trials for cancer treatment to prevent and treat cGVHD in two complementary murine models. In a major histocompatibility complex mismatched, non-sclerodermatous multiorgan system model with bronchiolitis obliterans, IRX4204 prevented and reversed cGVHD including associated pulmonary dysfunction with restoration of germinal center T-follicular helper: T-follicular regulatory cell balance. In a minor histocompatibility antigen disparate sclerodermatous model, IRX4204 treatment significantly prevented and ameliorated skin cGVHD by reducing Th1 and Th17 differentiation due to anti-inflammatory properties. Together, these results indicate that IRX4204 is a promising therapeutic option to treat cGVHD with bronchiolitis obliterans or sclerodermatous manifestations.

Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1.

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27─a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Predicting Metastasis in Melanoma by Enumerating Circulating Tumor Cells Using Photoacoustic Flow Cytometry.

BACKGROUND AND OBJECTIVES: Enumerating circulating tumor cells has been used as a method of monitoring progression of various cancers. Various methods for detecting circulating melanoma cells (CMCs) have been reported, but none has had sufficient sensitivity to determine if the presence of rare CMCs in the blood of Stage I-III melanoma patients predicts if those patients eventually develop metastatic disease. STUDY DESIGN: We quantified CMCs in serial blood samples from 38 early stage melanoma patients to determine if CMC numbers predict development of metastatic melanoma. CMCs were enumerated using a photoacoustic flow cytometric detection system that uses a laser to induce high frequency acoustic signals in pigmented CMCs. RESULTS: We observed that detection of greater than 2 CMCs/ml of blood from patients with Stage I-III melanoma predicts metastatic disease. Of the 11 patients we studied who had two or fewer CMCs detected at all time points tested, none progressed to metastatic disease over a mean follow-up of 1288 days. In contrast, 18 of the 27 patients (67%) having more than 2 CMCs/ml at one or more time points progressed to metastatic disease over a mean follow-up of 850 days. CONCLUSIONS: Photoacoustic flow cytometry can detect rare CMCs in the blood of Stage I-III melanoma patients and detectionof these cells is predictive of subsequent development of metastatic disease. Lasers Surg. Med.

A Phase 1 Study of IRX195183, a RARα-Selective CYP26 Resistant Retinoid, in Patients With Relapsed or Refractory AML.

Subsets of non-acute promyelocytic leukemia (APL) acute myelogenous leukemia (AML) exhibit aberrant retinoid signaling and demonstrate sensitivity to retinoids in vitro. We present the results of a phase 1 dose-escalation study that evaluated the safety, pharmacodynamics, and efficacy of IRX195183, a novel retinoic acid receptor α agonist, in patients with relapsed or refractory myelodysplastic syndrome (MDS) or AML. In this single center, single arm study, eleven patients with relapsed or refractory MDS/AML were enrolled and treated. Oral IRX195183 was administered at two dose levels: 50 mg daily or 75 mg daily for a total of two 28-day cycles. Patients with stable disease or better were allowed to continue on the drug for four additional 28-day cycles. Common adverse events included hypertriglyceridemia, fatigue, dyspnea, and edema. Three patients at the first dose level developed asymptomatic Grade 3 hypertriglyceridemia. The maximally tolerated dose was not reached. Four of the eleven patients had (36%) stable disease or better. One had a morphological complete remission with incomplete hematologic recovery while on the study drug. Two patients had evidence of in vivo leukemic blast maturation, as reflected by increased CD38 expression. In a pharmacodynamics study, plasma samples from four patients treated at the lowest dose level demonstrated the capacity to differentiate leukemic cells from the NB4 cell line in vitro. These results suggest that IRX195183 is safe, achieves biologically meaningful plasma concentrations and may be efficacious in a subset of patients with MDS/AML. Clinical Trial Registration: clinicaltrials.gov, identifier NCT02749708.

Photoacoustic detection of circulating melanoma cells in late stage patients.

Melanoma is the deadliest skin cancer and is responsible for over 7000 deaths in the US annually. The spread of cancer, or metastasis, is responsible for these deaths, as secondary tumors interrupt normal organ function. Circulating tumor cells, or those cells that spread throughout the body from the primary tumor, are thought to be responsible for metastasis. We developed an optical method, photoacoustic flow cytometry, in order to detect and enumerate circulating melanoma cells (CMCs) from blood samples of patients. We tested the blood of Stage IV melanoma patients to show the ability of the photoacoustic flow cytometer to detect these rare cells in blood. We then tested the system on archived blood samples from Stage III melanoma patients with known outcomes to determine if detection of CMCs can predict future metastasis. We detected between 0 and 66 CMCs in Stage IV patients. For the Stage III study, we found that of those samples with CMCs, 2 remained disease free and 5 developed metastasis. Of those without CMCs, 6 remained disease free and 1 developed metastasis. We believe that photoacoustic detection of CMCs provides valuable information for the prediction of metastasis and we postulate a system for more accurate prognosis.

Confounding Factors in the Interpretation of Preclinical Studies.

A number of issues may arise during the conduct of a study which can complicate interpretation of in vitro and in vivo datasets. Speakers discussed the implications of differing interpretations and how to avoid complicating factors during study planning and execution. Consideration needs to be given to study design factors including defining objectives, consideration of expected pharmacological effects, dose selection and drug kinetics, species used, and vehicle selection. In addition, the effects of vivarium temperature effects on various endpoints, how to control variables affecting clinical pathology, and how early death animals, common background findings, and artifacts can affect histopathology interpretation all play into the final interpretation of study data.

Selective brain penetrable Nurr1 transactivator for treating Parkinson's disease.

Parkinson's disease (PD) is one of the most common movement disorders, and currently there is no effective treatment that can slow disease progression. Preserving and enhancing DA neuron survival is increasingly regarded as the most promising therapeutic strategy for treating PD. IRX4204 is a second generation retinoid X receptor (RXR) agonist that has no cross reactivity with retinoic acid receptors, farnesoid X receptor, liver X receptors or peroxisome proliferator-activated receptor PPARγ. We found that IRX4204 promotes the survival and maintenance of nigral dopaminergic (DA) neurons in a dose-dependent manner in primary mesencephalic cultures. Brain bioavailability studies demonstrate that IRX4204 can cross the blood brain barrier and reach the brain at nM concentration. Oral administration of IRX4204 can activate nuclear receptor Nurr1 downstream signaling in the substantia nigra (SN) andattenuate neurochemical and motor deficits in a rat model of PD. Our study suggests that IRX4204 represents a novel, potent and selective pharmacological means to activate cellular RXR-Nurr1 signaling and promote SN DA neuron survival in PD prevention and/or treatment.

How do the top 12 pharmaceutical companies operate safety pharmacology?

INTRODUCTION: How does safety pharmacology operate in large pharmaceutical companies today? By understanding our current position, can we prepare safety pharmacology to successfully navigate the complex process of drug discovery and development? METHODS: A short anonymous survey was conducted, by invitation, to safety pharmacology representatives of the top 12 pharmaceutical companies, as defined by 2009 revenue figures. A series of multiple choice questions was designed to explore group size, accountabilities, roles and responsibilities of group members, outsourcing policy and publication record. RESULTS: A 92% response rate was obtained. Six out of 11 companies have 10 to 30 full time equivalents in safety pharmacology, who hold similar roles and responsibilities; although the majority of members are not qualified at PhD level or equivalent. Accountabilities were similar across companies and all groups have accountability for core battery in vivo studies and problem solving activities but differences do exist for example with in vitro safety screening and pharmacodynamic/pharmokinetic modeling (PK/PD). The majority of companies outsource less than 25% of studies, with in vitro profiling being the most commonly outsourced activity. Finally, safety pharmacology groups are publishing 1 to 4 articles each year. CONCLUSION: This short survey has highlighted areas of similarity and differences in the way large pharmaceutical companies operate safety pharmacology.

Estimating the risk of drug-induced proarrhythmia using human induced pluripotent stem cell-derived cardiomyocytes.

Improved in vitro systems for predicting drug-induced toxicity are needed in the pharmaceutical and biotechnology industries to decrease late-stage drug attrition. One unmet need is an early screen for cardiotoxicity, which accounts for about one third of safety-based withdrawn pharmaceuticals. Herein, the first published report of a high-throughput functional assay employing a monolayer of beating human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is described, detailing a model that accurately detects drug-induced cardiac abnormalities. Using 96-well plates with interdigitated electrode arrays that assess impedance, the rhythmic, synchronous contractions of the iPSC-CMs were detected. Treatment of the iPSC-CMs with 28 different compounds with known cardiac effects resulted in compound-specific changes in the beat rate and/or the amplitude of the impedance measurement. Changes in impedance for the compounds tested were comparable with the results from a related technology, electric field potential assessment obtained from microelectrode arrays. Using the results from the set of compounds, an index of drug-induced arrhythmias was calculated, enabling the determination of a drug's proarrhythmic potential. This system of interrogating human cardiac function in vitro opens new opportunities for predicting cardiac toxicity and studying cardiac biology.

The electrophysiological effects of cardiac glycosides in human iPSC-derived cardiomyocytes and in guinea pig isolated hearts.

BACKGROUND/AIMS: Monitoring changes in the field potential (FP) of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) following compound administration has been proposed as a novel screening tool to evaluate cardiac ion channel interactions and QT liability. Here we extended the use of FP to evaluate the pharmacological and toxicological properties of cardiac glycosides. METHODS: FPs were recorded using microelectrode arrays (MEAs) in spontaneously beating hiPSC-CMs. The in vitro effects of ouabain and digoxin on FPs were compared with data generated on hemodynamic and ECG parameters in guinea pig Langendorff hearts. RESULTS: In hiPSC-CMs, ouabain and digoxin reduced Na(+)-spike amplitude, shortened FP duration (FPD), increased Ca(2+)-wave amplitude, and dose-dependently induced arrhythmic beats. The ouabain-induced changes observed in hiPSC-CMs correlated well with the effects seen in isolated hearts which revealed QT shortening, enhancement of contractility, and arrhythmogenesis. Nifedipine, an L-type Ca(2+) channel blocker, reduced Ca(2+)-wave amplitude and FPD in hiPSC-CMs, and led to parallel effects of decreased ventricular contractility and shortened QT interval in isolated hearts. Further, nifedipine attenuated the Ca(2+)-peak amplitude and proarrhythmic effect of both glycosides. These results suggested that FPD and Ca(2+)-wave amplitude are comparable surrogates of QT interval and contractility of intact hearts, respectively. CONCLUSION: hiPSC-CMs reflect similar cardiac pharmacology as seen in isolated cardiac preparations and thus are a suitable model in study of the pharmacology and toxicology of cardioactive ion channel and transporter modulators.

Discovery and evaluation of pyrazolo[1,5-a]pyrimidines as neuropeptide Y1 receptor antagonists.

A novel series of pyrazolo[1,5-a]pyrimidine derivatives was synthesized and evaluated as NPY Y1R antagonists. High binding affinity and selectivity were achieved with C3 trisubstituted aryl groups and C7 substituted 2-(tetrahydro-2H-pyran-4-ylamino)ethylamine moieties. Efforts to find close analogs with low plasma clearance in the rat and minimal p-glycoprotein efflux in the mouse were unsuccessful. Compound 2f (CP-671906) inhibited NPY-induced increases in blood pressure and food intake after iv and icv administration, respectively, in Sprague-Dawley (SD) rat models. Oral administration of compound 2f resulted in a modest, but statistically significant, reduction in food intake in a Wistar rat model of feeding behavior. Small inhibitions of food intake were also observed in an overnight fasting/refeeding model in SD rats. These data suggest a potential role for Y1R in the regulation of food intake in rodents.

Recombinant human relaxin in the treatment of systemic sclerosis with diffuse cutaneous involvement: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: A phase II randomized controlled trial of recombinant human relaxin suggested that a dosage of 25 microg/kg/day was safe and clinically effective in improving skin disease and reducing functional disability in scleroderma (systemic sclerosis; SSc). We undertook a large randomized, double-blind, placebo-controlled clinical trial to compare placebo with 10 microg/kg/day and 25 microg/kg/day recombinant human relaxin, given for 24 weeks in patients with stable, diffuse, moderate-to-severe SSc. METHODS: Men and women ages 18-70 years with diffuse cutaneous SSc (dcSSc) were administered recombinant human relaxin (10 microg/kg/day or 25 microg/kg/day) or placebo for 24 weeks as a continuous subcutaneous infusion. There was a followup safety visit at week 28. RESULTS: The primary outcome measure, the modified Rodnan skin thickness score, was similar among the 3 groups at baseline and at weeks 4, 12, and 24. Secondary outcomes such as functional disability were similar in all 3 groups, while the forced vital capacity decreased significantly in the relaxin groups. The discontinuation of both doses of relaxin at week 24 led to statistically significant declines in creatinine clearance and serious renal adverse events (defined as doubling of serum creatinine, renal crisis, or grade 3 or 4 essential hypertension) in 7 patients who had received relaxin therapy but in none who had received placebo. CONCLUSION: Recombinant relaxin was not significantly better than placebo in improving the total skin score or pulmonary function or in reducing functional disability in patients with dcSSc. In addition, relaxin was associated with serious renal adverse events, the majority of which occurred after stopping the infusion. If relaxin is used therapeutically for any conditions other than scleroderma, close monitoring of blood pressure and renal function must be performed.

Natalizumab induction and maintenance therapy for Crohn's disease.

BACKGROUND: Natalizumab, a humanized monoclonal antibody against alpha4 integrin, inhibits leukocyte adhesion and migration into inflamed tissue. METHODS: We conducted two controlled trials to evaluate natalizumab as induction and maintenance therapy in patients with active Crohn's disease. In the first trial, 905 patients were randomly assigned to receive 300 mg of natalizumab or placebo at weeks 0, 4, and 8. The primary outcome was response, defined by a decrease in the Crohn's Disease Activity Index (CDAI) score of at least 70 points, at week 10. In the second trial, 339 patients who had a response to natalizumab in the first trial were randomly reassigned to receive 300 mg of natalizumab or placebo every four weeks through week 56. The primary outcome was a sustained response through week 36. A secondary outcome in both trials was disease remission (a CDAI score of less than 150). RESULTS: In the first trial, the natalizumab and placebo groups had similar rates of response (56 percent and 49 percent, respectively; P=0.05) and remission (37 percent and 30 percent, respectively; P=0.12) at 10 weeks. Continuing natalizumab in the second trial resulted in higher rates of sustained response (61 percent vs. 28 percent, P<0.001) and remission (44 percent vs. 26 percent, P=0.003) through week 36 than did switching to placebo. Serious adverse events occurred in 7 percent of each group in the first trial and in 10 percent of the placebo group and 8 percent of the natalizumab group in the second trial. In an open-label extension study, a patient treated with natalizumab died from progressive multifocal leukoencephalopathy, associated with the JC virus, a human polyomavirus. CONCLUSIONS: Induction therapy with natalizumab for Crohn's disease resulted in small, nonsignificant improvements in response and remission rates. Patients who had a response had significantly increased rates of sustained response and remission if natalizumab was continued every four weeks. The benefit of natalizumab will need to be weighed against the risk of serious adverse events, including progressive multifocal leukoencephalopathy. (ClinicalTrials.gov numbers, NCT00032786 and NCT00032799.)