a 50-week trial that compared combination therapy to IFX alone in 126 patients with CD who had initiated prednisone induction therapy, 15 to 40 mg daily, within 6 weeks of entry.Patients were randomly assigned to receive MTX at an initial weekly dose of 10 mg s.c., escalating to 25 mg, or placebo.Both groups received IFX; 5 mg/kg of body weight at weeks 1, 3, 7, 14 and every 8 weeks thereafter.Prednisone was tapered, beginning at week 1, and discontinued no later than week 14.The primary outcome was time to treatment failure, defined as failure to enter prednisone-free remission (CDAI <150) at week 14 or failure to maintain this remission through week 50.ATIs and trough serum IFX concentrations were measured every 8 weeks using the Prometheus® assays.RESULTS Sixty-three patients were randomized.Baseline characteristics were similar.By week 50 the actuarial rate of treatment failure was 30.6% in the combination group vs. 29.8% in the monotherapy group (P=0.63;hazard ratio 1.16, 95% CI 0.62 to 2.17).Patients who received MTX were less likely to develop antibodies to IFX (4.0% vs. 20.4%,P=0.01) than those who were assigned to placebo.The median serum trough IFX concentration was higher in patients receiving MTX, 6.35 mg per mL compared with 3.75 mg per mL, P=0.08.The proportion of patients with detectable drug at trough was also higher, 25.9% vs. 14.0%,P=0.13) in those assigned to MTX.Overall, patients who had detectable IFX at trough were more likely to be a treatment success (72.3% vs. 52.4%,P=0.08).CONCLUSIONS The combination of IFX and MTX, although safe, was no more effective than IFX alone in CD patients requiring treatment with prednisone.However, patients treated with MTX were less likely to form ATIs and have high serum trough IFX concentrations.Detectable IFX at trough was associated with treatment success independent of MTX assignment.

e13543 Background: Carcinoid syndrome (CS) occurs when metastatic carcinoid tumors secrete large amounts of serotonin (5-HT) and other bioactive substances into systemic circulation causing a variety of symptoms, including GI symptoms such as profound diarrhea. Reduction in 5-HT production by the tumor would be expected to improve symptoms in patients with CS. We therefore have examined the utility of inhibiting tryptophan hydroxylase (TPH), the enzyme that catalyzes the rate-limiting step in the synthesis of 5-HT, as a strategy to reduce 5-HT production in vivo with the goal of developing a new therapeutic approach to CS. The ability of LX1031 and LX1032, two novel TPH inhibitors to reduce 5-HT production was determined in clinical trials. Methods: Single and multiple ascending dose studies with LX1031 and LX1032 were conducted in normal volunteers. In addition, a 28-day study was conducted with the locally acting TPH inhibitor LX1031 in patients with non-constipating IBS. In the IBS study, multiple measures of GI symptoms were recorded daily along with a weekly global assessment. In all studies, blood and urine was collected for measurement of 5-HT and 5-HIAA, biomarkers of 5-HT production. Results: In normal volunteers LX1032 significantly reduced 5-HT production in a dose-dependent manner. Both LX1031 and LX1032 gave a 50-60% decrease in 24-hour urinary 5-HIAA after 14 days of 1000 mg QID and 500 mg TID, respectively, compared to placebo. In IBS patients, LX1031 produced a similar dose-dependent reduction in 5-HT production, and in the high dose arm demonstrated statistically significant improvements in parameters of global relief and stool consistency that correlated with the decrease in 5-HT production. Conclusions: These results demonstrate that TPH inhibitors, such as LX1032 and the locally acting LX1031, can significantly reduce 5-HT production in normal subjects at well-tolerated dose levels. In patients with IBS, administration of LX1031 was shown to lower 5-HT production and improve clinical GI symptoms. These results indicate that inhibiting serotonin synthesis via TPH inhibition is a viable new strategy for the symptomatic treatment of patients with carcinoid syndrome. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Lexicon Pharmaceuticals, Inc. Lexicon Pharmaceuticals, Inc. No significant financial relationships to disclose.

The development of molecular biological tools for mutant-mouse production signaled the new era of contemporary mammalian genetics. Recent technology advances coupled with completed sequence of the mouse and human genomes are converging synergistically such that today's scientists are exploring their fields of interest in arguably the most productive period for research and discovery of modern biological science. Scientists can now take advantage of an unprecedented ability to manipulate the mouse genome using versatile techniques that afford both custom genetic alteration and random mutagenesis approaches. Together, these strategies can be employed to quickly and comprehensively saturate the genome with a high percentage of gene coverage. Productivity estimates of the leading commercial biotechnology groups that have knockout mouse production and analysis capabilities, together with published knockout reports, suggest that roughly one-fourth of the approximate 25,000 genes in the mouse genome have been knocked out and studied to varying degrees. The international mouse-genomics community has recently begun an initiative to produce knockout alleles for all mouse genes and to develop a system for open access to data and reagents for the broader scientific community. Clearly we can look forward to an escalation of discovery productivity in the upcoming years. It will be even more exciting to track how mouse gene-function discoveries will drive the drug discovery industry's efforts to develop the next generation of therapies for human disease.

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 ≈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.