Discovery and Preclinical Pharmacology of NX-2127, an Orally Bioavailable Degrader of Bruton's Tyrosine Kinase with Immunomodulatory Activity for the Treatment of Patients with B Cell Malignancies.

Bruton's tyrosine kinase (BTK), a member of the TEC family of kinases, is an essential effector of B-cell receptor (BCR) signaling. Chronic activation of BTK-mediated BCR signaling is a hallmark of many hematological malignancies, which makes it an attractive therapeutic target. Pharmacological inhibition of BTK enzymatic function is now a well-proven strategy for the treatment of patients with these malignancies. We report the discovery and characterization of NX-2127, a BTK degrader with concomitant immunomodulatory activity. By design, NX-2127 mediates the degradation of transcription factors IKZF1 and IKZF3 through molecular glue interactions with the cereblon E3 ubiquitin ligase complex. NX-2127 degrades common BTK resistance mutants, including BTKC481S. NX-2127 is orally bioavailable, exhibits in vivo degradation across species, and demonstrates efficacy in preclinical oncology models. NX-2127 has advanced into first-in-human clinical trials and achieves deep and sustained degradation of BTK following daily oral dosing at 100 mg.

Improved glycemic control in mice lacking Sglt1 and Sglt2.

Sodium-glucose cotransporter 2 (SGLT2) is the major, and SGLT1 the minor, transporter responsible for renal glucose reabsorption. Increasing urinary glucose excretion (UGE) by selectively inhibiting SGLT2 improves glycemic control in diabetic patients. We generated Sglt1 and Sglt2 knockout (KO) mice, Sglt1/Sglt2 double-KO (DKO) mice, and wild-type (WT) littermates to study their relative glycemic control and to determine contributions of SGLT1 and SGLT2 to UGE. Relative to WTs, Sglt2 KOs had improved oral glucose tolerance and were resistant to streptozotocin-induced diabetes. Sglt1 KOs fed glucose-free high-fat diet (G-free HFD) had improved oral glucose tolerance accompanied by delayed intestinal glucose absorption and increased circulating glucagon-like peptide-1 (GLP-1), but had normal intraperitoneal glucose tolerance. On G-free HFD, Sglt2 KOs had 30%, Sglt1 KOs 2%, and WTs <1% of the UGE of DKOs. Consistent with their increased UGE, DKOs had lower fasting blood glucose and improved intraperitoneal glucose tolerance than Sglt2 KOs. In conclusion, 1) Sglt2 is the major renal glucose transporter, but Sglt1 reabsorbs 70% of filtered glucose if Sglt2 is absent; 2) mice lacking Sglt2 display improved glucose tolerance despite UGE that is 30% of maximum; 3) Sglt1 KO mice respond to oral glucose with increased circulating GLP-1; and 4) DKO mice have improved glycemic control over mice lacking Sglt2 alone. These data suggest that, in patients with type 2 diabetes, combining pharmacological SGLT2 inhibition with complete renal and/or partial intestinal SGLT1 inhibition may improve glycemic control over that achieved by SGLT2 inhibition alone.

The knockout mouse project.

Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain.

High-Throughput Screening of Mouse Gene Knockouts Identifies Established and Novel High Body Fat Phenotypes.

PURPOSE: Obesity is a major public health problem. Understanding which genes contribute to obesity may better predict individual risk and allow development of new therapies. Because obesity of a mouse gene knockout (KO) line predicts an association of the orthologous human gene with obesity, we reviewed data from the Lexicon Genome5000TM high throughput phenotypic screen (HTS) of mouse gene KOs to identify KO lines with high body fat. MATERIALS AND METHODS: KO lines were generated using homologous recombination or gene trapping technologies. HTS body composition analyses were performed on adult wild-type and homozygous KO littermate mice from 3758 druggable mouse genes having a human ortholog. Body composition was measured by either DXA or QMR on chow-fed cohorts from all 3758 KO lines and was measured by QMR on independent high fat diet-fed cohorts from 2488 of these KO lines. Where possible, comparisons were made to HTS data from the International Mouse Phenotyping Consortium (IMPC). RESULTS: Body fat data are presented for 75 KO lines. Of 46 KO lines where independent external published and/or IMPC KO lines are reported as obese, 43 had increased body fat. For the remaining 29 novel high body fat KO lines, Ksr2 and G2e3 are supported by data from additional independent KO cohorts, 6 (Asnsd1, Srpk2, Dpp8, Cxxc4, Tenm3 and Kiss1) are supported by data from additional internal cohorts, and the remaining 21 including Tle4, Ak5, Ntm, Tusc3, Ankk1, Mfap3l, Prok2 and Prokr2 were studied with HTS cohorts only. CONCLUSION: These data support the finding of high body fat in 43 independent external published and/or IMPC KO lines. A novel obese phenotype was identified in 29 additional KO lines, with 27 still lacking the external confirmation now provided for Ksr2 and G2e3 KO mice. Undoubtedly, many mammalian obesity genes remain to be identified and characterized.

NOTUM inhibition increases endocortical bone formation and bone strength.

The disability, mortality and costs caused by non-vertebral osteoporotic fractures are enormous. Existing osteoporosis therapies are highly effective at reducing vertebral but not non-vertebral fractures. Cortical bone is a major determinant of non-vertebral bone strength. To identify novel osteoporosis drug targets, we phenotyped cortical bone of 3 366 viable mouse strains with global knockouts of druggable genes. Cortical bone thickness was substantially elevated in Notum -/- mice. NOTUM is a secreted WNT lipase and we observed high NOTUM expression in cortical bone and osteoblasts but not osteoclasts. Three orally active small molecules and a neutralizing antibody inhibiting NOTUM lipase activity were developed. They increased cortical bone thickness and strength at multiple skeletal sites in both gonadal intact and ovariectomized rodents by stimulating endocortical bone formation. Thus, inhibition of NOTUM activity is a potential novel anabolic therapy for strengthening cortical bone and preventing non-vertebral fractures.

Knockouts model the 100 best-selling drugs--will they model the next 100?

The biopharmaceutical industry is currently faced with a tremendous number of potential drug targets identified through the sequencing of the human genome. The challenge ahead is to delineate those targets with the greatest value for therapeutic intervention. Here, we critically evaluate mouse-knockout technology for target discovery and validation. A retrospective evaluation of the knockout phenotypes for the targets of the 100 best-selling drugs indicates that these phenotypes correlate well with known drug efficacy, illuminating a productive path forward for discovering future drug targets. Prospective mining of the druggable genome is being catalysed by large-scale mouse knockout programs combined with phenotypic screens focused on identifying targets that modulate mammalian physiology in a therapeutically relevant manner.

Telotristat Ethyl, a Tryptophan Hydroxylase Inhibitor for the Treatment of Carcinoid Syndrome.

Purpose Preliminary studies suggested that telotristat ethyl, a tryptophan hydroxylase inhibitor, reduces bowel movement (BM) frequency in patients with carcinoid syndrome. This placebo-controlled phase III study evaluated telotristat ethyl in this setting. Patients and Methods Patients (N = 135) experiencing four or more BMs per day despite stable-dose somatostatin analog therapy received (1:1:1) placebo, telotristat ethyl 250 mg, or telotristat ethyl 500 mg three times per day orally during a 12-week double-blind treatment period. The primary end point was change from baseline in BM frequency. In an open-label extension, 115 patients subsequently received telotristat ethyl 500 mg. Results Estimated differences in BM frequency per day versus placebo averaged over 12 weeks were -0.81 for telotristat ethyl 250 mg ( P < .001) and ‒0.69 for telotristat ethyl 500 mg ( P < .001). At week 12, mean BM frequency reductions per day for placebo, telotristat ethyl 250 mg, and telotristat ethyl 500 mg were -0.9, -1.7, and -2.1, respectively. Responses, predefined as a BM frequency reduction ≥ 30% from baseline for ≥ 50% of the double-blind treatment period, were observed in 20%, 44%, and 42% of patients given placebo, telotristat ethyl 250 mg, and telotristat ethyl 500 mg, respectively. Both telotristat ethyl dosages significantly reduced mean urinary 5-hydroxyindole acetic acid versus placebo at week 12 ( P < .001). Mild nausea and asymptomatic increases in gamma-glutamyl transferase were observed in some patients receiving telotristat ethyl. Follow-up of patients during the open-label extension revealed no new safety signals and suggested sustained BM responses to treatment. Conclusion Among patients with carcinoid syndrome not adequately controlled by somatostatin analogs, treatment with telotristat ethyl was generally safe and well tolerated and resulted in significant reductions in BM frequency and urinary 5-hydroxyindole acetic acid.

Rescue of Mdm4-deficient mice by Mdm2 reveals functional overlap of Mdm2 and Mdm4 in development.

The Mdm2 and Mdm4 genes are amplified and overexpressed in a variety of human cancers and encode structurally related oncoproteins that bind to the p53 tumor suppressor protein and inhibit p53 activity. Mice deleted for either Mdm2 or Mdm4 die during embryogenesis, and the developmental lethality of either mouse model can be rescued by concomitant deletion of p53. However, the phenotypes of Mdm2 and Mdm4-deficient mice suggest that Mdm2 and Mdm4 play nonoverlapping roles in regulating p53 activity during development, with Mdm2 regulating p53-mediated cell death and Mdm4 regulating p53-mediated inhibition of cell growth. Here, we describe complete rescue of Mdm4-deficient mice by expression of an Mdm2 transgene, and demonstrate that Mdm2 can regulate both p53-mediated apoptosis and inhibition of cell growth in the absence of Mdm4 in primary cells. Furthermore, deletion of Mdm4 enhances the ability of Mdm2 to promote cell growth and tumor formation, indicating that Mdm4 has antioncogenic properties when Mdm2 is overexpressed.

mdmx is a negative regulator of p53 activity in vivo.

Regulation of p53 protein activity is required for normal embryogenesis, tumor suppression, and cellular response to DNA damage. Here we report that loss of mdmx, a p53-binding protein, results in midgestational embryo lethality, a phenotype that is completely rescued by the absence of p53. Mice homozygous for both mdmx and p53 null mutations are viable and appear developmentally normal. Fibroblasts derived from embryos with reduced mdmx expression demonstrate a decreased growth rate and increased UV-induced apoptosis compared with wild-type cells and contain elevated levels of p53 and several p53 target proteins including the proapoptotic bax protein. These observations demonstrate that mdmx functions as a critical negative regulator of p53 in vivo.

Absence of p21 partially rescues Mdm4 loss and uncovers an antiproliferative effect of Mdm4 on cell growth.

Mdm4 (MdmX) is a p53-binding protein that shares structural similarities with Mdm2 and has been proposed to be a negative regulator of p53 function. Like Mdm2, the absence of Mdm4 has recently been found to induce embryonic lethality in mice that is rescued by p53 deletion. Mdm4-null embryos are reduced in size and die at mid-gestation, and Mdm4-deficient embryos and embryonic fibroblasts displayed reduced rates of cell proliferation. The p53-induced, cyclin-dependent kinase inhibitor p21 is strongly upregulated in Mdm4-null embryos and cells. Here, we report that deletion of p21 delays the mid-gestation lethality observed in Mdm4-null mice, suggesting that Mdm4 downregulates p53-mediated suppression of cell growth. Surprisingly, the absence of p21 also uncovers an antiproliferative effect of Mdm4 on cell growth in vitro and in Mdm4-heterozygous mice. These results indicate that p21 is a downstream modifier of Mdm4, and provides genetic evidence that Mdm4 can function to regulate cell growth both positively and negatively.

Predicting drug efficacy: knockouts model pipeline drugs of the pharmaceutical industry.

One of the major challenges for the pharmaceutical industry is to develop innovative drugs to new targets from the human genome. A systematic approach for target selection could significantly increase the rate of successful new drug development, thereby enhancing industry productivity. It has previously been shown that mouse knockout phenotypes for the targets of the 100 best-selling pharmaceutical drugs correlate well with known drug efficacy. Furthermore, physiological validation of novel pipeline targets of the pharmaceutical industry has been provided using mouse knockout data. These data demonstrate an excellent correlation between knockout phenotype and anticipated drug efficacy, establishing an important marker for superior new drug targets from the genome.

Sotagliflozin, a Dual SGLT1 and SGLT2 Inhibitor, as Adjunct Therapy to Insulin in Type 1 Diabetes.

OBJECTIVE: To assess the safety and efficacy of dual sodium-glucose cotransporter (SGLT) 1 and SGLT2 inhibition with sotagliflozin as adjunct therapy to insulin in type 1 diabetes. RESEARCH DESIGN AND METHODS: We treated 33 patients with sotagliflozin, an oral dual SGLT1 and SGLT2 inhibitor, or placebo in a randomized, double-blind trial assessing safety, insulin dose, glycemic control, and other metabolic parameters over 29 days of treatment. RESULTS: In the sotagliflozin-treated group, the percent reduction from baseline in the primary end point of bolus insulin dose was 32.1% (P = 0.007), accompanied by lower mean daily glucose measured by continuous glucose monitoring (CGM) of 148.8 mg/dL (8.3 mmol/L) (P = 0.010) and a reduction of 0.55% (5.9 mmol/mol) (P = 0.002) in HbA1c compared with the placebo group that showed 6.4% reduction in bolus insulin dose, a mean daily glucose of 170.3 mg/dL (9.5 mmol/L), and a decrease of 0.06% (0.65 mmol/mol) in HbA1c. The percentage of time in target glucose range 70-180 mg/dL (3.9-10.0 mmol/L) increased from baseline with sotagliflozin compared with placebo, to 68.2% vs. 54.0% (P = 0.003), while the percentage of time in hyperglycemic range >180 mg/dL (10.0 mmol/L) decreased from baseline, to 25.0% vs. 40.2% (P = 0.002), for sotagliflozin and placebo, respectively. Body weight decreased (1.7 kg) with sotagliflozin compared with a 0.5 kg gain (P = 0.005) in the placebo group. CONCLUSIONS: As adjunct to insulin, dual SGLT1 and SGLT2 inhibition with sotagliflozin improved glycemic control and the CGM profile with bolus insulin dose reduction, weight loss, and no increased hypoglycemia in type 1 diabetes.

Full-speed mammalian genetics: in vivo target validation in the drug discovery process.

The completion of the Human Genome Project has signaled the beginning of the post-genome era, with a corresponding shift in focus from the sequencing and identification of genes to the exploration of gene function. A rate-limiting step in deriving value from this gene sequence information is determining the potential pharmaceutical applications of genes and their encoded proteins. This validation step is crucial for focusing efforts and resources on only the most promising targets. Strategies using reverse mouse genetics provide excellent methods for validating potential targets and therapeutic proteins in vivo in a mammalian model system.

Severe retinal degeneration associated with disruption of semaphorin 4A.

PURPOSE: Semaphorin 4A (Sema4A) is a member of the transmembrane class 4 family of semaphorins. It has recently been shown to participate in cell-cell communication in the immune system. High levels of sema4A are also present in brain and eye, but its function in the central nervous system has not been studied. To investigate the function of Sema4A, we generated mice deficient in this transmembrane signaling molecule. METHODS: An embryonic stem (ES) cell clone with a retroviral gene-trap insertion in the sema4A gene was used to generate mice lacking this transmembrane semaphorin. Fundus photography, fluorescein angiography, and electroretinography were used to evaluate retinal anatomy and physiology in mice lacking Sema4A. Electron microscopy and immunohistochemistry with cell-type-specific markers were used to characterize retinal development. In situ hybridization with sema4A-specific riboprobes was used to localize expression of this gene in the developing and adult eye. RESULTS: Fundus photography performed at 14 weeks of age revealed severe retinal degeneration, attenuated retinal vessels, and depigmentation in mice lacking Sema4A. At this age, the outer nuclear layer was reduced to a single row of photoreceptor cells, and the outer plexiform layer was thin and disorganized. Disruption of Sema4A also compromised the physiological function of both rod and cone photoreceptors. Developmental studies in Sema4A-deficient mice revealed abnormal morphology of photoreceptor outer segments during the time at which they establish contacts with apical microvilli of the retinal pigment epithelium (RPE). Sema4A is expressed in the inner retina and RPE during the time at which photoreceptor outer segments elongate. CONCLUSIONS: These findings identify a previously unknown function of Sema4A in the developing visual system and provide a useful model for understanding cell-cell interactions that occur between photoreceptors and the RPE.

High-throughput screening of mouse gene knockouts identifies established and novel skeletal phenotypes.

Screening gene function in vivo is a powerful approach to discover novel drug targets. We present high-throughput screening (HTS) data for 3 762 distinct global gene knockout (KO) mouse lines with viable adult homozygous mice generated using either gene-trap or homologous recombination technologies. Bone mass was determined from DEXA scans of male and female mice at 14 weeks of age and by microCT analyses of bones from male mice at 16 weeks of age. Wild-type (WT) cagemates/littermates were examined for each gene KO. Lethality was observed in an additional 850 KO lines. Since primary HTS are susceptible to false positive findings, additional cohorts of mice from KO lines with intriguing HTS bone data were examined. Aging, ovariectomy, histomorphometry and bone strength studies were performed and possible non-skeletal phenotypes were explored. Together, these screens identified multiple genes affecting bone mass: 23 previously reported genes (Calcr, Cebpb, Crtap, Dcstamp, Dkk1, Duoxa2, Enpp1, Fgf23, Kiss1/Kiss1r, Kl (Klotho), Lrp5, Mstn, Neo1, Npr2, Ostm1, Postn, Sfrp4, Slc30a5, Slc39a13, Sost, Sumf1, Src, Wnt10b), five novel genes extensively characterized (Cldn18, Fam20c, Lrrk1, Sgpl1, Wnt16), five novel genes with preliminary characterization (Agpat2, Rassf5, Slc10a7, Slc26a7, Slc30a10) and three novel undisclosed genes coding for potential osteoporosis drug targets.

Large-scale gene trapping in C57BL/6N mouse embryonic stem cells.

We report the construction and analysis of a mouse gene trap mutant resource created in the C57BL/6N genetic background containing more than 350,000 sequence-tagged embryonic stem (ES) cell clones. We also demonstrate the ability of these ES cell clones to contribute to the germline and produce knockout mice. Each mutant clone is identified by a genomic sequence tag representing the exact insertion location, allowing accurate prediction of mutagenicity and enabling direct genotyping of mutant alleles. Mutations have been identified in more than 10,000 genes and show a bias toward the first intron. The trapped ES cell lines, which can be requested from the Texas A&M Institute for Genomic Medicine, are readily available to the scientific community.

High-throughput screening of mouse knockout lines identifies true lean and obese phenotypes.

We developed a high-throughput approach to knockout (KO) and phenotype mouse orthologs of the 5,000 potential drug targets in the human genome. As part of the phenotypic screen, dual-energy X-ray absorptiometry (DXA) technology estimates body-fat stores in eight KO and four wild-type (WT) littermate chow-fed mice from each line. Normalized % body fat (nBF) (mean KO % body fat/mean WT littermate % body fat) values from the first 2322 lines with viable KO mice at 14 weeks of age showed a normal distribution. We chose to determine how well this screen identifies body-fat phenotypes by selecting 13 of these 2322 KO lines to serve as benchmarks based on their published lean or obese phenotype on a chow diet. The nBF values for the eight benchmark KO lines with a lean phenotype were > or =1 s.d. below the mean for seven (perilipin, SCD1, CB1, MCH1R, PTP1B, GPAT1, PIP5K2B) but close to the mean for NPY Y4R. The nBF values for the five benchmark KO lines with an obese phenotype were >2 s.d. above the mean for four (MC4R, MC3R, BRS3, translin) but close to the mean for 5HT2cR. This screen also identifies novel body-fat phenotypes as exemplified by the obese kinase suppressor of ras 2 (KSR2) KO mice. These body-fat phenotypes were confirmed upon studying additional cohorts of mice for KSR2 and all 13 benchmark KO lines. This simple and cost-effective screen appears capable of identifying genes with a role in regulating mammalian body fat.

Lipid-lowering effects of anti-angiopoietin-like 4 antibody recapitulate the lipid phenotype found in angiopoietin-like 4 knockout mice.

We used gene knockout mice to explore the role of Angiopoietin-like-4 (Angptl4) in lipid metabolism as well as to generate anti-Angptl4 mAbs with pharmacological activity. Angptl4 -/- mice had lower triglyceride (TG) levels resulting both from increased very low-density lipoprotein (VLDL) clearance and decreased VLDL production and had modestly lower cholesterol levels. Also, both Angptl4 -/- suckling mice and adult mice fed a high-fat diet showed reduced viability associated with lipogranulomatous lesions of the intestines and their draining lymphatics and mesenteric lymph nodes. Treating C57BL/6J, ApoE -/-, LDLr -/-, and db/db mice with the anti-Angptl4 mAb 14D12 recapitulated the lipid and histopathologic phenotypes noted in Angptl4 -/- mice. This demonstrates that the knockout phenotype reflects not only the physiologic function of the Angptl4 gene but also predicts the pharmacologic consequences of Angptl4 protein inhibition with a neutralizing antibody in relevant models of human disease.

Wnk1 kinase deficiency lowers blood pressure in mice: a gene-trap screen to identify potential targets for therapeutic intervention.

The availability of both the mouse and human genome sequences allows for the systematic discovery of human gene function through the use of the mouse as a model system. To accelerate the genetic determination of gene function, we have developed a sequence-tagged gene-trap library of >270,000 mouse embryonic stem cell clones representing mutations in approximately 60% of mammalian genes. Through the generation and phenotypic analysis of knockout mice from this resource, we are undertaking a functional screen to identify genes regulating physiological parameters such as blood pressure. As part of this screen, mice deficient for the Wnk1 kinase gene were generated and analyzed. Genetic studies in humans have shown that large intronic deletions in WNK1 lead to its overexpression and are responsible for pseudohypoaldosteronism type II, an autosomal dominant disorder characterized by hypertension, increased renal salt reabsorption, and impaired K+ and H+ excretion. Consistent with the human genetic studies, Wnk1 heterozygous mice displayed a significant decrease in blood pressure. Mice homozygous for the Wnk1 mutation died during embryonic development before day 13 of gestation. These results demonstrate that Wnk1 is a regulator of blood pressure critical for development and illustrate the utility of a functional screen driven by a sequence-based mutagenesis approach.