An ALK2 inhibitor, BLU-782, prevents heterotopic ossification in a mouse model of fibrodysplasia ossificans progressiva.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease driven by gain-of-function variants in activin receptor-like kinase 2 (ALK2), the most common variant being ALK2R206H. In FOP, ALK2 variants display increased and dysregulated signaling through the bone morphogenetic protein (BMP) pathway resulting in progressive and permanent replacement of skeletal muscle and connective tissues with heterotopic bone, ultimately leading to severe debilitation and premature death. Here, we describe the discovery of BLU-782 (IPN60130), a small-molecule ALK2R206H inhibitor developed for the treatment of FOP. A small-molecule library was screened in a biochemical ALK2 binding assay to identify potent ALK2 binding compounds. Iterative rounds of structure-guided drug design were used to optimize compounds for ALK2R206H binding, ALK2 selectivity, and other desirable pharmacokinetic properties. BLU-782 preferentially bound to ALK2R206H with high affinity, inhibiting signaling from ALK2R206H and other rare FOP variants in cells in vitro without affecting signaling of closely related homologs ALK1, ALK3, and ALK6. In vivo efficacy of BLU-782 was demonstrated using a conditional knock-in ALK2R206H mouse model, where prophylactic oral dosing reduced edema and prevented cartilage and heterotopic ossification (HO) in both muscle and bone injury models. BLU-782 treatment preserved the normal muscle-healing response in ALK2R206H mice. Delayed dosing revealed a short 2-day window after injury when BLU-782 treatment prevented HO in ALK2R206H mice, but dosing delays of 4 days or longer abrogated HO prevention. Together, these data suggest that BLU-782 may be a candidate for prevention of HO in FOP.

Evaluation of Protein Kinase cAMP-Activated Catalytic Subunit Alpha as a Therapeutic Target for Fibrolamellar Carcinoma.

Background and Aims: Fibrolamellar carcinoma (FLC) is a rare, difficult-to-treat liver cancer primarily affecting pediatric and adolescent patients, and for which precision medicine approaches have historically not been possible. The DNAJB1-PRKACA gene fusion was identified as a driver of FLC pathogenesis. We aimed to assess whether FLC tumors maintain dependency on this gene fusion and determine if PRKACA is a viable therapeutic target. Methods: FLC patient-derived xenograft (PDX) shRNA cell lines were implanted subcutaneously into female NOD-SCID mice and tumors were allowed to develop prior to randomization to doxycycline (to induce knockdown) or control groups. Tumor development was assessed every 2 days. To assess the effect of treatment with novel selective PRKACA small molecule kinase inhibitors, BLU0588 and BLU2864, FLC PDX tumor cells were implanted subcutaneously into NOD-SCID mice and tumors allowed to develop. Mice were randomized to treatment (BLU0588 and BLU2864, orally, once daily) or control groups and tumor size determined as previously. Results: Knockdown of DNAJB1-PRKACA reversed a FLC-specific gene signature and reduced PDX tumor growth in mice compared to the control group. Furthermore, FLC PDX tumor growth was significantly reduced with BLU0588 and BLU2864 treatment vs control (P = .003 and P = .0005, respectively). Conclusion: We demonstrated, using an inducible knockdown and small molecule approaches, that FLC PDX tumors were dependent upon DNAJB1-PRKACA fusion activity. In addition, this study serves as a proof-of-concept that PRKACA is a viable therapeutic target for FLC and warrants further investigation.

Evaluation of Therapeutics for Severely Debilitating or Life-Threatening Diseases or Conditions: Defining Scope to Enable Global Guidance Development.

A significant regulatory gap exists to facilitate global development of therapeutics for nononcology severely debilitating or life-threatening diseases or conditions (SDLTs). In a 2017 publication, a streamlined approach to the development of treatments for SDLTs was proposed to facilitate earlier and continued patient access to new, potentially beneficial therapeutics.1 However, a major hindrance to broad adoption of this streamlined approach has been the lack of universally accepted, objective criteria to define SDLTs. This article serves to extend the 2017 publication by further addressing the challenge of defining SDLT scope in order to stimulate broader discussion and facilitate development of regional and ultimately international guidelines on the development of therapeutics for SDLTs. Using case examples, we describe key attributes of SDLTs and provide criteria for consideration of an SDLT scope definition.

In vitro secondary pharmacological profiling: An IQ-DruSafe industry survey on current practices.

INTRODUCTION: In 2015, IQ DruSafe conducted a survey of its membership to identify industry practices related to in vitro off target pharmacological profiling of small molecules. METHODS: An anonymous survey of 20 questions was submitted to IQ-DruSafe representatives. Questions were designed to explore screening strategies, methods employed and experience of regulatory interactions related to in vitro secondary pharmacology profiling. RESULTS: The pharmaceutical industry routinely utilizes panels of in vitro assays to detect undesirable off-target interactions of new chemical entities that are deployed at all stages of drug discovery and early development. The formats, approaches and size of panels vary between companies, in particular i) choice of assay technology; ii) test concentration (single vs. multiple concentrations) iii) rationale for targets and panels selection (taking into account organizational experience, primary target, therapeutic area, availability at service providers) iv) threshold level for significant interaction with a target and v) data interpretation. Data are generated during the early phases of drug discovery, principally before in vivo GLP studies (i.e., hit-to-lead, lead optimization, development candidate selection) and used to contextualize in vivo non-clinical and clinical findings. Data were included in regulatory documents, and around half of respondents experienced regulatory questions about the significance of the results. CONCLUSION: While it seems that in vitro secondary pharmacological profiling is generally considered valuable across the industry, particularly as a tool in early phases of drug discovery for small molecules, there is only loose consensus on testing paradigm, the required interpretation and suitable follow up strategies to fully understand potential risk.

Current nonclinical testing paradigm enables safe entry to First-In-Human clinical trials: The IQ consortium nonclinical to clinical translational database.

The contribution of animal testing in drug development has been widely debated and challenged. An industry-wide nonclinical to clinical translational database was created to determine how safety assessments in animal models translate to First-In-Human clinical risk. The blinded database was composed of 182 molecules and contained animal toxicology data coupled with clinical observations from phase I human studies. Animal and clinical data were categorized by organ system and correlations determined. The 2×2 contingency table (true positive, false positive, true negative, false negative) was used for statistical analysis. Sensitivity was 48% with a 43% positive predictive value (PPV). The nonhuman primate had the strongest performance in predicting adverse effects, especially for gastrointestinal and nervous system categories. When the same target organ was identified in both the rodent and nonrodent, the PPV increased. Specificity was 84% with an 86% negative predictive value (NPV). The beagle dog had the strongest performance in predicting an absence of clinical adverse effects. If no target organ toxicity was observed in either test species, the NPV increased. While nonclinical studies can demonstrate great value in the PPV for certain species and organ categories, the NPV was the stronger predictive performance measure across test species and target organs indicating that an absence of toxicity in animal studies strongly predicts a similar outcome in the clinic. These results support the current regulatory paradigm of animal testing in supporting safe entry to clinical trials and provide context for emerging alternate models.

Proteasome inhibitors bortezomib and carfilzomib used for the treatment of multiple myeloma do not inhibit the serine protease HtrA2/Omi.

The proteasome inhibitor bortezomib is associated with the development of peripheral neuropathy in patients, but the mechanism by which bortezomib can induce peripheral neuropathy is not fully understood. One study suggested that off-target inhibition of proteases other than the proteasome, particularly HtraA2/Omi, may be the underlying mechanism of the neuropathy. The same study also concluded that carfilzomib, a second proteasome inhibitor that is associated with less peripheral neuropathy in patients than bortezomib, showed no inhibition of HtrA2/Omi. The goal of the work described here was to determine whether either proteasome inhibitors truly affected HtrA2/Omi activity. A variety of methods were used to test the effects of both bortezomib and carfilzomib on HtrA2/Omi activity that included in vitro recombinant enzyme assays, and studies with the human neuroblastoma SH-SY5Y cell line and HtrA2/Omi-knockout mouse embryonic fibroblasts. The compound ucf-101 was used to assess the effects of specific HtrA2/Omi inhibition. In contrast to previously published data, our results clearly demonstrated that neither bortezomib nor carfilzomib inhibited HtrA2/Omi activity in recombinant enzyme assays at concentrations up to 100 µM, while the specific inhibitor ucf-101 did inhibit the enzyme. The proteasome inhibitors did not inhibit HtrA2/Omi activity in either SH-SY5Y cells or mouse embryonic fibroblasts, as determined by expression of the HtrA2/Omi substrates eIF4G1 and UCH-L1. Based on our biochemical and cell-based assays, we conclude that neither bortezomib nor carfilzomib inhibited HtrA2/Omi activity. Therefore, it is unlikely that bortezomib associated peripheral neuropathy is a direct result of off-target inhibition of HtrA2/Omi.

MLN8054 and Alisertib (MLN8237): Discovery of Selective Oral Aurora A Inhibitors.

The Aurora kinases are essential for cell mitosis, and the dysregulation of Aurora A and B have been linked to the etiology of human cancers. Investigational agents MLN8054 (8) and alisertib (MLN8237, 10) have been identified as high affinity, selective, orally bioavailable inhibitors of Aurora A that have advanced into human clinical trials. Alisertib (10) is currently being evaluated in multiple Phase II and III clinical trials in hematological malignancies and solid tumors.

Use of animals for toxicology testing is necessary to ensure patient safety in pharmaceutical development.

There is an active debate in toxicology literature about the utility of animal testing vis-a-vis alternative in vitro paradigms. To provide a balanced perspective and add to this discourse it is important to review the current paradigms, explore pros and cons of alternatives, and provide a vision for the future. The fundamental goal of toxicity testing is to ensure safety in humans. In this article, IQ Consortium DruSafe, while submitting the view that nonclinical testing in animals is an important and critical component of the risk assessment paradigm in developing new drugs, also discusses its views on alternative approaches including a roadmap for what would be required to enhance the utilization of alternative approaches in the safety assessment process.

Exclusive antagonism of the α4 ß7 integrin by vedolizumab confirms the gut-selectivity of this pathway in primates.

BACKGROUND: Biological therapies that antagonize specific molecules have demonstrated efficacy in inflammatory bowel diseases, but infections resulting from systemic immunosuppression underscore the need for safer therapies. The objective of this investigation was to determine if antagonism of the α(4) ß(7) integrin would exclusively yield gut-selective antiinflammatory activity in primates. METHODS: A series of experiments were conducted to investigate potential intra- and extraintestinal effects in healthy nonhuman primates dosed repeatedly with the α(4) ß(7) -exclusive antagonist vedolizumab (former versions: MLN0002, MLN02, LDP-02) for 4, 13, and 26 weeks. RESULTS: No adverse clinical effects of vedolizumab were observed in healthy cynomolgus monkeys up to the highest doses tested (100 mg/kg). Histomorphologic analyses indicated a reduction in the frequency of leukocytes in gastrointestinal tissue, but not other organs. A significant (P < 0.05) decrease in the frequency of ß 7+ lymphocytes in gastrointestinal tissues corresponded to a significant (P < 0.05) increase in α(4) ß 7+ memory helper T lymphocytes in peripheral blood. This elevation was specific to α(4) ß 7+ memory helper T lymphocytes; levels of other leukocyte subsets remained unaffected. Systemic opportunistic infections were not observed, and vedolizumab did not inhibit adaptive or innate immune responses systemically. CONCLUSIONS: These data demonstrate that blocking the α(4) ß(7) integrin exclusively yields gut-selective antiinflammatory activity in primates.

Identification and characterization of amino-piperidinequinolones and quinazolinones as MCHr1 antagonists.

Several potent, functionally active MCHr1 antagonists derived from quinolin-2(1H)-ones and quinazoline-2(1H)-ones have been synthesized and evaluated. Pyridylmethyl substitution at the quinolone 1-position results in derivatives with low-nM binding potency and good selectivity with respect to hERG binding.

Transgenic mice with cardiac-specific over-expression of MLK7 have increased mortality when exposed to chronic beta-adrenergic stimulation.

Mixed lineage kinase 7 (MLK7) is a recently identified mitogen-activated protein kinase kinase kinase with enriched expression in skeletal muscle and heart. When over-expressed in cardiac myocytes, MLK7 activates both the p38 and c-Jun N-terminal kinase (JNK) stress-activated pathways and induces a cellular phenotype characteristic of cardiac hypertrophy, including a fetal gene expression pattern and increased protein synthesis. We sought to determine the effect of MLK7 on cardiac function in vivo by generating transgenic (Tg) mice with cardiac restricted over-expression of the enzyme. The mice were viable and demonstrated no visible signs of distress at rest. Microscopic examination of the hearts showed myocardial fibrosis and hypertrophy. Hemodynamic analysis of the Tg mice revealed impaired systolic function and significant diastolic dysfunction. Furthermore, significant mortality was observed in MLK7 Tg mice following 24-48 h of isoproterenol administration. Isoproterenol activation of JNK and p38, but not extracellular signal-regulated kinase, was significantly greater in the MLK7 Tg mice compared to littermate controls. These data indicate that MLK7 is an important signal transducer in cardiac compensation. Simultaneous activation of JNK and p38 by MLK7 may contribute to cardiac decompensation during the periods of acute cardiac stress.

Heart block, ventricular tachycardia, and sudden death in ACE2 transgenic mice with downregulated connexins.

Angiotensin converting enzyme related carboxypeptidase (ACE2) is a recently discovered homolog of angiotensin converting enzyme with tissue-restricted expression, including heart, and the capacity to cleave angiotensin peptides. We tested the hypothesis that cardiac ACE2 activity contributes to features of ventricular remodeling associated with the renin-angiotensin system by generating transgenic mice with increased cardiac ACE2 expression. These animals had a high incidence of sudden death that correlated with transgene expression levels. Detailed electrophysiology revealed severe, progressive conduction and rhythm disturbances with sustained ventricular tachycardia and terminal ventricular fibrillation. The gap junction proteins connexin40 and connexin43 were downregulated in the transgenic hearts, indicating that ACE2-mediated gap junction remodeling may account for the observed electrophysiologic disturbances. Spontaneous downregulation of the ACE2 transgene in surviving older animals correlated with restoration of nearly normal conduction, rhythm, and connexin expression.

Differential regulation of p38 mitogen-activated protein kinase mediates gender-dependent catecholamine-induced hypertrophy.

OBJECTIVE: Exogenous catecholamine exposure has been associated with p38 mitogen-activated protein kinase (MAPK) and cardiac hypertrophy. In this study, we investigated the regulation of p38 MAPK in cardiac remodeling elicited by endogenous adrenergic mechanisms. METHODS: Transgenic male and female mice with fourfold phospholamban (PLB) overexpression exhibited enhanced circulating norepinephrine (NE), as a physiological compensatory mechanism to attenuate PLB's inhibitory effects. This enhanced noradrenergic state resulted in left ventricular hypertrophy/dilatation and depressed function. RESULTS: Male transgenics exhibited ventricular hypertrophy and mortality at 15 months, concurrent with cardiac p38 MAPK activation. Female transgenics, despite similar contractile dysfunction, displayed a temporal delay in p38 activation, hypertrophy, and mortality (22 months), which was associated with sustained cardiac levels of MAP Kinase Phosphatase-1 (MKP-1), a potent inhibitor of p38. At 22 months, decreases in cardiac MKP-1 were accompanied by increased levels of p38 activation. In vitro studies indicated that preincubation with 17-beta-estradiol induced high MKP-1 levels, which precluded NE-induced p38 activation. CONCLUSION: These findings suggest that norepinephrine-induced hypertrophy is linked closely with p38 MAP kinase activation, which can be endogenously modulated through estrogen-responsive regulation of MKP-1 expression.

Hypertrophy and functional alterations in hyperdynamic phospholamban-knockout mouse hearts under chronic aortic stenosis.

OBJECTIVE: To determine whether the hyperdynamic phospholamban-knockout hearts are capable of withstanding a chronic aortic stenosis. METHODS: The transverse section of the aorta was banded in phospholamban-knockout and their isogenic wild-type mice, which were followed with echocardiography in parallel, along with sham-operated mice, before and at 2.5, 5 and 10 weeks after surgery. RESULTS: Cardiac decompensation was evidenced by the presence of lung congestion in some banded knockouts and wild-types, giving rise to a subset of non-failing and failing hearts within each group. The incidence of heart failure was not genotype-dependent but rather associated with higher heart rates before surgery. The development of left ventricular hypertrophy was similar between knockouts and wild-types and longitudinal assessment of end-diastolic dimension indicated progressive increases after banding, with a greater dilation in failing mice. Fractional shortening was reduced in failing knockouts and wild-types to a similar degree, with an earlier onset in the knockouts. In addition, fractional shortening was decreased in non-failing knockouts but not wild-types. Ejection times shortened after aortic banding particularly for failing hearts. Assessment of the SR Ca(2+)-ATPase protein levels indicated similar downregulation for failing knockouts and wild-types, while the phospholamban levels were not significantly altered in wild-types. CONCLUSION: The hyperdynamic phospholamban-knockout hearts are able to compensate against a sustained aortic stenosis similar to wild-types.