Systemic lupus erythematosus (SLE) is a chronic, systemic autoimmune disease which can present with mixed organ involvement. Kidney involvement in lupus nephritis (LN) is a severe complication and major cause of mortality in SLE patients, second only to cardiovascular disease. While mouse models have helped uncover some molecular pathways involved in SLE/LN, we need a better understanding of the connection of these pathways and the immune cells involved in disease pathogenesis to develop new and effective therapies. Furthermore, models used for studying SLE/LN in mice have a heterogeneous immune response and may not always represent disease manifestations observed in patients. Identifying models that have shared pathways with human disease would allow for better translation for developing effective SLE/LN therapies. The molecular pathways of five different SLE/LN models (MRL/lpr, poly (I:C)-induced, interferon-α-induced, bm12 GvHD, and spontaneous NZB/W F1) were compared to characterize the immune response in mouse kidneys. These models demonstrated varied magnitudes in immune responses and proportions of innate vs. adaptive cell involvement. These findings were compared to human molecular pathways and cell types from public databases, including the Accelerating Medicine Partnership–Systemic Lupus Erythematosus Program (AMP-SLE), to help corelate mechanisms involved in mouse models to human disease.

B cells contribute to multiple aspects of autoimmune disorders, and B cell-targeting therapies, including B cell depletion, have been proven to be efficacious in treatment of multiple autoimmune diseases. However, the development of novel therapies targeting B cells with higher efficacy and a nondepleting mechanism of action is highly desirable. Here we describe a nondepleting, high-affinity anti-human CD19 antibody LY3541860 that exhibits potent B cell inhibitory activities. LY3541860 inhibits B cell activation, proliferation, and differentiation of primary human B cells with high potency. LY3541860 also inhibits human B cell activities in vivo in humanized mice. Similarly, our potent anti-mCD19 antibody also demonstrates improved efficacy over CD20 B cell depletion therapy in multiple B cell-dependent autoimmune disease models. Our data indicate that anti-CD19 antibody is a highly potent B cell inhibitor that may have potential to demonstrate improved efficacy over currently available B cell-targeting therapies in treatment of autoimmune conditions without causing B cell depletion.

The Th17 pathway has been implicated in autoimmune diseases. The retinoic acid receptor-related orphan receptor C2 (RORγt) is a master regulator of Th17 cells and controls the expression of IL-17A. RORγt is expressed primarily in IL-17A-producing lymphoid cells. Here we describe a virtual screen of the ligand-binding pocket and subsequent screen in a binding assay that identified the 1-benzyl-4',5'-dihydrospiro[piperidine-4,7'-thieno[2,3-c]pyran]-2'-carboxamide scaffold as a starting point for optimization of binding affinity and functional activity guided by structure-based design. Compound 12 demonstrated activity in a mouse PK/PD model and efficacy in an inflammatory arthritis mouse model that were used to define the level and duration of target engagement required for efficacy in vivo. Further optimization to improve ADME and physicochemical properties with guidance from simulations and modeling provided compound 22, which is projected to achieve the level and duration of target engagement required for efficacy in the clinic.

The spinal nucleus of the bulbocavernosus (SNB) neuromuscular system is a highly conserved and well-studied model of sexual differentiation of the vertebrate nervous system. Sexual differentiation of the SNB is currently thought to be mediated by the direct action of perinatal testosterone on androgen receptors (ARs) in the bulbocavernosus/levator ani muscles, with concomitant motoneuron rescue. This model has been proposed based on surgical and pharmacological manipulations of developing rats as well as from evidence that male rats with the testicular feminization mutation (Tfm), which is a loss of function AR mutation, have a feminine SNB phenotype. We examined whether genetically replacing AR in muscle fibers is sufficient to rescue the SNB phenotype of Tfm rats. Transgenic rats in which wild-type (WT) human AR is driven by a human skeletal actin promoter (HSA-AR) were crossed with Tfm rats. Resulting male HSA-AR/Tfm rats express WT AR exclusively in muscle and nonfunctional Tfm AR in other tissues. We then examined motoneuron and muscle morphology of the SNB neuromuscular system of WT and Tfm rats with and without the HSA-AR transgene. We observed feminine levator ani muscle size and SNB motoneuron number and size in Tfm males with or without the HSA-AR transgene. These results indicate that AR expression in skeletal muscle fibers is not sufficient to rescue the male phenotype of the SNB neuromuscular system and further suggest that AR in other cell types plays a critical role in sexual differentiation of this system.

Selective androgen receptor modulators (SARMs) are a new class of molecules in development to treat a variety of diseases. SARMs maintain the beneficial effects of androgens, including increased muscle mass and bone density, while having reduced activity on unwanted side effects. The mechanisms responsible for the tissue-selective activity of SARMs are not fully understood, and the pharmacokinetic (PK)/pharmacodynamic (PD) relationships are poorly described. Tissue-specific compound distribution potentially could be a mechanism responsible for apparent tissue selectivity. We examined the PK/PD relationship of a novel SARM, LGD-3303 [9-chloro-2-ethyl-1-methyl-3-(2,2,2-trifluoroethyl)-3H-pyrrolo[3,2-f]quinolin-7(6H)-one], in a castrated rat model of androgen deficiency. LGD-3303 has potent activity on levator ani muscle but is a partial agonist on the preputial gland and ventral prostate. LGD-3303 never stimulated ventral prostate above intact levels despite increasing plasma concentrations of compound. Tissue-selective activity was maintained when LGD-3303 was dosed orally or by continuous infusion, two routes of administration with markedly different time versus exposure profiles. Despite the greater muscle activity relative to prostate activity, local tissue concentrations of LGD-3303 were higher in the prostate than in the levator ani muscle. LGD-3303 has SARM properties that are independent of its pharmacokinetic profile, suggesting that the principle mechanism for tissue-selective activity is the result of altered molecular interactions at the level of the androgen receptor.

Although it is evident that androgens increase muscle mass and strength, little is known about the critical molecular targets of androgens in skeletal muscle. In rodents, the skeletal alpha-actin gene is a tissue-specific gene expressed only in the levator ani and other skeletal muscles but not in the prostate or preputial gland, the well-known androgen target tissue. We identified tissue-specific androgen-regulated genes in the skeletal muscle in rats after oral administration of androgens and focused on androgen-dependent up-regulation of the skeletal alpha-actin gene. To investigate the mechanism of action, an in vitro system with various cell lines and a series of deletion mutants of the alpha-actin promoter were used. The human skeletal alpha-actin promoter was activated by androgens in the muscle cell line C2C12 but not in the liver, prostate, or breast cancer cell lines in which exogenous human androgen receptor is expressed. The sequence of the promoter is sufficient for cell-specific androgen response, providing a model for the tissue specificity demonstrated in vivo. Using a series of deletion mutants, the androgen response can be maintained using just the proximal promoter region. The importance of androgen regulation of this small portion of the human skeletal alpha-actin promoter was demonstrated by the correlation between muscle and the alpha-actin promoter activity for an array of selective androgen receptor modulators (SARMs), including an orally active SARM LGD2226. Taken together, the results suggest that the regulation of skeletal alpha-actin by androgens/SARMs may represent an important model system for understanding androgen anabolic action in the muscle.

Modification on a lead series of [1,4]oxazino[3,2-g]quinolin-7-ones at the 2-position led to selective androgen receptor modulators with improved in vivo activity. The most potent analog (-)-33a exhibited full maintenance of levator ani muscle at 3mg/kg and reduced activity on ventral prostate weight in a 2-week orally-dosed and orchidectomized rat maintenance assay.

A series of selective androgen receptor modulators (SARMs) with a wide spectrum of receptor modulating activities was developed based on optimization of the 4-substituted 6-bisalkylamino-2-quinolinones (3). Significance of the trifluoromethyl group on the side chains and its interactions with amino acid residues within the androgen receptor (AR) ligand binding domain are discussed. A representative analog (9) was tested orally in a rodent model of hypogonadism and demonstrated desirable tissue selectivity.

The androgen receptor is a ligand inducible transcription factor that is involved in a broad range of physiological functions. Here we describe the discovery of a new class of orally available selective androgen receptor modulators. The lead compound, 6-[(2R,5R)-2-methyl-5-((R)-2,2,2-trifluoro- 1-hydroxyethyl)pyrrolidin-1-yl]-4-trifluoromethylquinolin-2(1H)-one (6a), showed excellent anabolic activity in muscle with reduced effect on the prostate in a rat model of hypogonadism. The compound also improved bone strength in a rat model of post-menopausal osteoporosis.

A number of conditions, including osteoporosis, frailty, and sexual dysfunction in both men and women have been improved using androgens. However, androgens are not widely used for these indications because of the side effects associated with these drugs. We describe an androgen receptor (AR) ligand that maintains expected anabolic activities with substantially diminished activity in the prostate. LGD2226 is a nonsteroidal, nonaromatizable, highly selective ligand for the AR, exhibiting virtually no affinity for the other intracellular receptors. We determined that AR bound to LGD2226 exhibits a unique pattern of protein-protein interactions compared with testosterone, fluoxymesterone (an orally available steroidal androgen), and other steroids, suggesting that LGD2226 alters the conformation of the ligand-binding domain. We demonstrated that LGD2226 is fully active in cell-based models of bone and muscle. LGD2226 exhibited anabolic activity on muscle and bone with reduced impact on prostate growth in rodent models. Biomechanical testing of bones from animals treated with LGD2226 showed strong enhancement of bone strength above sham levels. LGD2226 was also efficacious in a sex-behavior model in male rats measuring mounts, intromissions, ejaculations, and copulation efficiency. These results with an orally available, nonaromatizable androgen demonstrate the important role of the AR and androgens in mediating a number of beneficial effects in bone, muscle, and sexual function independent from the conversion of androgens into estrogenic ligands. Taken together, these results suggest that orally active, nonsteroidal selective androgen receptor modulators may be useful therapeutics for enhancing muscle, bone, and sexual function.

Brief exposure to estrogens during the neonatal period interrupts rat prostatic development by reducing branching morphogenesis and by blocking epithelial cells from entering a normal differentiation pathway. Upon aging, ventral prostates exhibit extensive hyperplasia and dysplasia suggesting that neonatal estrogens may predispose the prostate gland to preneoplastic lesions. To determine whether these prostatic lesions may be manifested through aberrant cell-to-cell communications, the present study examined specific gap junction proteins, Connexins (Cx) 32, and Cx 43, and the cell adhesion molecule, E-cadherin, in the developing, adult and aged rat prostate gland. Male rat pups were given 25 μg estradiol benzoate or oil on days 1, 3, and 5 of life. Prostates were removed on days 1, 4, 5, 6, 10, 15, 30, or 90 or at 16 months, and frozen sections were immunostained for E-cadherin, Cx 43, and Cx 32. Colocalization studies were performed with immunofluorescence using specific antibodies for cell markers. Gap junctions in undifferentiated epithelial cells at days 1–10 of life were composed of Cx 43, which always colocalized with basal cell cytokeratins (CK 5/15). Cx 32 expression was first observed between days 10–15 and colocalized to differentiated luminal cells (CK 8/18). Cx 43 and Cx 32 never colocalized to the same cell indicating that gap junction intercellular communication differs between basal and luminal prostatic cells. While epithelial connexin expression was not initially altered in the developing prostates following estrogen exposure, adult prostates of neonatally estrogenized rats exhibited a marked decrease in Cx 32 staining and an increased proportion of Cx 43 expressing cells. In the developing prostate, E-cadherin was localized to lateral surfaces of undifferentiated epithelial cells and staining intensity increased as the cells differentiated into luminal cells. By day 30, estrogenized prostates had small foci of epithelial cells that did not immunostain for E-cadherins. In the adult and aged prostates of estrogenized rats, larger foci with differentiation defects and dysplasia were associated with a decrease or loss in E-cadherin staining. The present findings suggest that estrogen-induced changes in the expression of E-cadherin, Cx32 and Cx43 may result in impaired cell-cell adhesion and defective cell-cell communication and may be one of the key mechanisms through which changes toward a dysplastic state are mediated. These findings are significant in light of the data on human prostate cancers where carcinogenesis and progression are associated with loss of E-cadherin and a switch from Cx32 to Cx43 expression in the epithelium.

The purpose of this study was to examine whether changes in extracellular matrix (ECM) molecules are associated with the growth inhibition and differentiation defects of the prostate gland following neonatal exposure to estradiol. Using immunocytochemistry (ICC), laminin and collagen IV were localized to the basement membrane (BM) as well to the basal lamina of the periductal smooth muscle of the control developing prostates. In contrast, fibronectin and collagen III were localized throughout the stromal ECM. Exposure to neonatal estrogen altered the staining profile for specific ECM molecules. In the estrogenized rats, a thick layer of cells negative for laminin and collagen IV was observed adjacent to the BM. Electron microscopy and ICC for α-actin, fibronectin, and vimentin identified this multicellular layer of periductal cells as differentiated fibroblasts. Peripheral to these fibroblasts, actin-positive smooth muscle formed a second layer of periductal stromal cells. PCNA labeling showed that estrogen exposure increased the fibroblast proliferation. Because many periductal fibroblasts were positive for estrogen receptor α (ERα) in estrogenized rats, a direct effect of estradiol on their proliferation is suggested. Gelatinolytic gels revealed that estrogen exposure did not alter the activity of matrix metalloproteinases associated with tissue remodeling during prostate morphogenesis. However, the periductal fibroblast layer in estrogenized prostates was devoid of urokinase- and tissue-plasminogen activator, which may potentially alter the localized proteolysis involved in matrix remodeling. It is proposed that proliferation of a multicellular layer of periductal fibroblasts in estrogenized prostates results in a physical barrier that constrains branching morphogenesis and blocks paracrine communications between smooth muscle and epithelial cells which normally regulate differentiation.