Challenges and gaps in immunosafety evaluation of therapeutics: An IQ DruSafe survey.

Immunotoxicology/immunosafety science is rapidly evolving, with novel modalities and immuno-oncology among the primary drivers of new tools and technologies. The Immunosafety Working Group of IQ/DruSafe sought to better understand some of the key challenges in immunosafety evaluation, gaps in the science, and current limitations in methods and data interpretation. A survey was developed to provide a baseline understanding of the needs and challenges faced in immunosafety assessments, the tools currently being applied across the industry, and the impact of feedback received from regulatory agencies. This survey also focused on current practices and challenges in conducting the T-cell-dependent antibody response (TDAR) and the cytokine release assay (CRA). Respondents indicated that ICH S8 guidance was insufficient for the current needs of the industry portfolio of immunomodulators and novel modalities and should be updated. Other challenges/gaps identified included translation of nonclinical immunosafety assessments to the clinic, and lack of relevant nonclinical species and models in some cases. Key areas of emerging science that will add future value to immunotoxicity assessments include development of additional in vitro and microphysiological system models, as well as application of humanized mouse models. Efforts are ongoing in individual companies and consortia to address some of these gaps and emerging science.

Salt Selection Matters: Differential Renal Toxicity With MDV1634.Maleate Versus MDV1634.2HCl.

Salt forms of pharmaceutical compounds can have unique pharmacokinetic and toxicity properties. MDV1634 was evaluated for neurology indication and also demonstrated blood pressure (BP)-lowering effects in nonclinical studies. During the chemistry manufacturing campaign, 2 salt forms, dihydrochloride (2HCl) and maleate (MAL), which improved chemical stability and water solubility of the free base were identified. MDV1634.MAL showed better chemical attributes and was evaluated in toxicology studies for further development. A 28-day oral toxicity study in dogs with MDV1634.MAL demonstrated partially reversible renal toxicity. Although MAL salt is generally regarded as safe, renal toxicity is sometimes observed in rats and dogs. To evaluate contribution of each salt form to renal toxicity and BP lowering, an additional 28-day study was conducted with MDV1634.2HCL and MDV1634.MAL, which included toxicokinetics, continuous BP measurement in a subset of dogs, and sensitive urinary biomarker evaluation for temporal monitorability and reversibility of potential renal findings. In the repeat study, both salt forms showed similar exposures during the dosing period, but renal tubular toxicity was observed only with MDV1634.MAL and not with MDV1634.2HCl. The renal findings with MDV1634.MAL included early urinary biomarker changes (increase in albumin, clusterin, ß2 microglobulin, and neutrophil gelatinase-associated lipocalin); elevations in serum blood urea nitrogen and creatinine; and microscopic findings of partially reversible tubular basophilia, single cell necrosis, pigmentation, and mineralization. The renal findings in contrast to the BP findings were MAL-specific and considered not related to MDV1634, thereby under scoring the importance of salt forms in pharmaceutical development.

Mutational tail loss is an evolutionary mechanism for liberating marapsins and other type I serine proteases from transmembrane anchors.

Human and mouse marapsins (Prss27) are serine proteases preferentially expressed by stratified squamous epithelia. However, mouse marapsin contains a transmembrane anchor absent from the human enzyme. To gain insights into physical forms, activities, inhibition, and roles in epithelial differentiation, we traced tail loss in human marapsin to a nonsense mutation in an ancestral ape, compared substrate preferences of mouse and human marapsins with those of the epithelial peptidase prostasin, designed a selective substrate and inhibitor, and generated Prss27-null mice. Phylogenetic analysis predicts that most marapsins are transmembrane proteins. However, nonsense mutations caused membrane anchor loss in three clades: human/bonobo/chimpanzee, guinea pig/degu/tuco-tuco/mole rat, and cattle/yak. Most marapsin-related proteases, including prostasins, are type I transmembrane proteins, but the closest relatives (prosemins) are not. Soluble mouse and human marapsins are tryptic with subsite preferences distinct from those of prostasin, lack general proteinase activity, and unlike prostasins resist antiproteases, including leupeptin, aprotinin, serpins, and α2-macroglobulin, suggesting the presence of non-canonical active sites. Prss27-null mice develop normally in barrier conditions and are fertile without overt epithelial defects, indicating that marapsin does not play critical, non-redundant roles in development, reproduction, or epithelial differentiation. In conclusion, marapsins are conserved, inhibitor-resistant, tryptic peptidases. Although marapsins are type I transmembrane proteins in their typical form, they mutated independently into anchorless forms in several mammalian clades, including one involving humans. Similar pathways appear to have been traversed by prosemins and tryptases, suggesting that mutational tail loss is an important means of evolving new functions of tryptic serine proteases from transmembrane ancestors.

Accumulation of intraepithelial mast cells with a unique protease phenotype in T(H)2-high asthma.

BACKGROUND: Previously, we found that mast cell tryptases and carboxypeptidase A3 (CPA3) are differentially expressed in the airway epithelium in asthmatic subjects. We also found that asthmatic subjects can be divided into 2 subgroups ("T(H)2 high" and "T(H)2 low" asthma) based on epithelial cell gene signatures for the activity of T(H)2 cytokines. OBJECTIVES: We sought to characterize intraepithelial mast cells (IEMCs) in asthma. METHODS: We performed gene expression profiling in epithelial brushings and stereology-based quantification of mast cell numbers in endobronchial biopsy specimens from healthy control and asthmatic subjects before and after treatment with inhaled corticosteroids (ICSs). We also performed gene expression and protein quantification studies in cultured airway epithelial cells and mast cells. RESULTS: By means of unsupervised clustering, mast cell gene expression in the airway epithelium related closely to the expression of IL-13 signature genes. The levels of expression of mast cell genes correlate positively with lung function improvements with ICSs. IEMC density was 2-fold higher than normal in subjects with T(H)2-high asthma compared with that seen in subjects with T(H)2-low asthma or healthy control subjects (P = .015 for both comparisons), and these cells were characterized by expression of tryptases and CPA3 but not chymase. IL-13 induced expression of stem cell factor in cultured airway epithelial cells, and mast cells exposed to conditioned media from IL-13-activated epithelial cells showed downregulation of chymase but no change in tryptase or CPA3 expression. CONCLUSION: IEMC numbers are increased in subjects with T(H)2-high asthma, have an unusual protease phenotype (tryptase and CPA3 high and chymase low), and predict responsiveness to ICSs. IL-13-stimulated production of stem cell factor by epithelial cells potentially explains mast cell accumulation in T(H)2-high asthmatic epithelium.

Mast cell alpha and beta tryptases changed rapidly during primate speciation and evolved from gamma-like transmembrane peptidases in ancestral vertebrates.

Human mast cell tryptases vary strikingly in secretion, catalytic competence, and inheritance. To explore the basis of variation, we compared genes from a range of primates, including humans, great apes (chimpanzee, gorilla, orangutan), Old- and New-World monkeys (macaque and marmoset), and a prosimian (galago), tracking key changes. Our analysis reveals that extant soluble tryptase-like proteins, including alpha- and beta-like tryptases, mastins, and implantation serine proteases, likely evolved from membrane-anchored ancestors because their more deeply rooted relatives (gamma tryptases, pancreasins, prostasins) are type I transmembrane peptidases. Function-altering mutations appeared at widely separated times during primate speciation, with tryptases evolving by duplication, gene conversion, and point mutation. The alpha-tryptase Gly(216)Asp catalytic domain mutation, which diminishes activity, is present in macaque tryptases, and thus arose before great apes and Old World monkeys shared an ancestor, and before the alphabeta split. However, the Arg(-3)Gln processing mutation appeared recently, affecting only human alpha. By comparison, the transmembrane gamma-tryptase gene, which anchors the telomeric end of the multigene tryptase locus, changed little during primate evolution. Related transmembrane peptidase genes were found in reptiles, amphibians, and fish. We identified soluble tryptase-like genes in the full spectrum of mammals, including marsupial (opossum) and monotreme (platypus), but not in nonmammalian vertebrates. Overall, our analysis suggests that soluble tryptases evolved rapidly from membrane-anchored, two-chain peptidases in ancestral vertebrates into soluble, single-chain, self-compartmentalizing, inhibitor-resistant oligomers expressed primarily by mast cells, and that much of present numerical, behavioral, and genetic diversity of alpha- and beta-like tryptases was acquired during primate evolution.

STAT4 signal pathways regulate inflammation and airway physiology changes in allergic airway inflammation locally via alteration of chemokines.

Mice homozygous for the STAT4-null mutation were sensitized to cockroach Ag, challenged intratracheally 21 days later, and compared with STAT4-competent allergic mice. The STAT4(-/-) mice showed significant decreases in airway hyperreactivity (AHR) and peribronchial eosinophils compared with wild-type controls. In addition, pulmonary levels of chemokines were decreased in the STAT4(-/-) mice, including CC chemokine ligand (CCL)5, CCL6, CCL11, and CCL17. However, levels of Th2-type cytokines, such as IL-4 and IL-13, as well as serum IgE levels were similar in the two groups. Transfer of splenic lymphocytes from sensitized wild-type mice into sensitized STAT4(-/-) mice did not restore AHR in the mutant mice. Furthermore, chemokine production and peribronchial eosinophilia were not restored during the cellular transfer experiments. Thus, it appears that STAT4 expression contributes to a type 2 process such as allergen-induced chemokine production and AHR. In additional studies, competent allergic mice were treated with anti-IL-12 locally in the airways at the time of allergen rechallenge. These latter studies also demonstrated a decrease in AHR. Altogether, these data suggest that STAT4-mediated pathways play a role locally within the airway for the exacerbation of the allergen-induced responses.