Results from Companion TELECAST Study Show Consistency with Clinical Benefit in Carcinoid Syndrome Observed in Pivotal TELESTAR Study, Support Planned Filings for Regulatory Approval

The Woodlands, Texas, December 1, 2015 - Lexicon Pharmaceuticals, Inc.'s (Nasdaq: LXRX) announced today that top-line data from its TELECAST Phase 3 study showed results of telotristat etiprate in treating carcinoid syndrome in cancer patients with metastatic neuroendocrine tumors consistent with the clinical benefit observed in its pivotal TELESTAR study. The TELECAST study was designed as a companion to TELESTAR primarily to provide additional safety exposure while further evaluating telotristat etiprate's activity in carcinoid syndrome. TELECAST mostly enrolled patients treated with somatostatin analog (SSA) therapy, the current standard of care, with carcinoid syndrome characterized by less severe bowel movement frequency than those patients in the TELESTAR study, together with a smaller number of carcinoid syndrome patients not treated with SSA therapy.

Telotristat etiprate met the study's primary efficacy endpoint, the percent change from baseline in urinary 5-hydroxyindoleacetic acid (5-HIAA, the main metabolite of serotonin) at week 12, the final week of the double-blind treatment portion of the study (p<0.001 for='' both='' dose='' arms='' compared='' to='' _placebo29_.='' in='' _addition2c_='' despite='' the='' lower='' baseline='' bowel='' movement='' frequency='' than='' _telestar2c_='' telotristat='' etiprate='' achieved='' statistically='' significant='' reductions='' daily='' over='' 12='' weeks='' of='' study='' _28_p='0.004' 250='' mg='' arm='' and=''><0.001 for='' the='' 500='' mg='' dose='' arm='' compared='' to='' _placebo29_.='' safety='' and='' tolerability='' was='' one='' of='' primary='' objectives='' telecast='' _study2c_='' telotristat='' etiprate='' well='' tolerated='' during='' double-blind='' treatment='' _period2c_='' with='' profiles='' similar='' placebo='' both='' 250='' arms='' no='' overall='' differences='' observed='' in='' gastrointestinal='' disorders='' or='' psychiatric='' _disorders2c_='' including='' changes=''>

'We are very pleased with the efficacy and safety results of telotristat etiprate in this study, notably including evidence of benefit in a patient population whose bowel movement frequency was lower at baseline than was the case in TELESTAR,' said Lexicon Executive Vice President and Chief Medical Officer Pablo Lapuerta, M.D. 'TELECAST was intended to complement our pivotal Phase 3 trial, TELESTAR. We now have experience in more than 200 patients with carcinoid syndrome, with TELECAST contributing consistent efficacy data and favorable safety results. The data further support that the compound is acting directly on the cause of carcinoid syndrome, by reducing serotonin production within tumor cells.'

Carcinoid syndrome is a rare disease affecting thousands of cancer patients with metastatic neuroendocrine tumors (mNETs) that have spread to the liver and other organs from the gastrointestinal tract. The condition is characterized by frequent and debilitating diarrhea that often prevents patients from leading active, predictable lives, as well as by facial flushing, abdominal pain, fatigue and, over time, heart valve damage.

Results from Lexicon's pivotal TELESTAR Phase 3 study were presented earlier this year at the European Cancer Conference and the annual symposium of the North American Neuroendocrine Tumor Society.

TELECAST Results

The double-blind TELECAST study enrolled 76 patients with or without concomitant SSA therapy provided they qualified based on at least one sign/symptom of carcinoid syndrome, such as at least two episodes of flushing per day, elevated urinary 5-HIAA at baseline, or nausea present on at least one out of five days at baseline. Patients who were not receiving SSA therapy could also qualify for the study based on experiencing at least four bowel movements per day as their sign/symptom. The three-arm study evaluated two doses of oral telotristat etiprate - 250 mg and 500 mg, each taken three times daily - against placebo over a 12-week period with primary outcome measures consisting of safety and the percent change from baseline in urinary 5-HIAA, and secondary outcome measures including change from baseline in the number of daily bowel movements. Patients in both the treatment and placebo arms who were on SSA therapy at baseline continued their SSA therapy throughout the study.

Data showed that patients treated with telotristat etiprate at both the 250 mg and 500 mg doses experienced a statistically significant percent reduction from baseline compared to placebo in urinary 5-HIAA, the main metabolite of serotonin, at week 12, the final week of the double-blind treatment portion of the study (p<_0.00129_2c_ meeting='' the='' _studye28099_s='' primary='' efficacy=''>

In addition, data showed that patients treated with telotristat etiprate at both the 250 mg and 500 mg doses experienced a statistically significant percent reduction from baseline compared to placebo in the average number of daily bowel movements over the 12 weeks of the study (p=0.004 for the 250 mg dose arm and p<0.001 for='' the='' 500='' mg='' dose='' arm='' compared='' to=''>

Treatment with telotristat etiprate was well tolerated during the double-blind treatment period. The proportions of patients with treatment-emergent adverse events (AEs) were 100% in the 250 mg arm, 84% in the 500 mg arm and 81% in the placebo group during the 12-week study period. The proportions of patients with serious AEs (none of which were deemed related to treatment) were 4% in the 250 mg arm, 8% in the 500 mg arm and 19% in the placebo group. The proportions of patients who discontinued treatment due to AEs were 8% in the 250 mg arm, 0% in the 500 mg arm and 4% in the placebo group. Notably, in terms of pre-defined AEs of special interest, both doses of telotristat etiprate appeared similar to placebo, with three patients experiencing nausea in the 250 mg arm, two in the 500 mg arm and four in the placebo group, and one patient experiencing depression or depressed mood in each of the 250 mg and 500 mg arms and two in the placebo group.

About Telotristat Etiprate

Discovered using Lexicon's unique approach to gene science, telotristat etiprate is the first investigational drug in clinical studies to target tryptophan hydroxylase, an enzyme that triggers the excess serotonin production within mNET cells that leads to carcinoid syndrome. While existing treatments for carcinoid syndrome work to reduce the release of serotonin outside tumor cells, telotristat etiprate works at the source to reduce serotonin production within the tumor cells. By specifically inhibiting serotonin production, telotristat etiprate seeks to control this important driver of carcinoid syndrome and, in turn, provide patients with more control over their disease.

Telotristat etiprate has received Fast Track and Orphan Drug designation from the U.S. Food and Drug Administration.

Lexicon retains rights to market telotristat etiprate in the U.S. and Japan, and is building the in-house commercial infrastructure to serve the U.S. market. Lexicon has a license and collaboration agreement with Ipsen to commercialize telotristat etiprate in Europe and other countries outside the U.S. and Japan.

About Lexicon

Lexicon is a fully integrated biopharmaceutical company that is applying a unique approach to gene science based on Nobel Prize-winning technology to discover and develop precise medicines for patients with serious, chronic conditions. Through its Genome5000™ program, Lexicon scientists have studied the role and function of nearly 5,000 genes over the last 20 years and have identified more than 100 protein targets with significant therapeutic potential in a range of diseases. Through the precise targeting of these proteins, Lexicon is pioneering the discovery and development of innovative medicines to safely and effectively treat disease. Lexicon has a pipeline of promising drug candidates in clinical and pre-clinical development in oncology, diabetes and metabolism. For additional information please visit www.lexpharma.com.

Safe Harbor Statement

This press release contains 'forward-looking statements,' including statements relating to Lexicon's clinical development of telotristat etiprate (LX1032) and the results of and projected timing of clinical trials and the potential therapeutic and commercial potential of telotristat etiprate. In addition, this press release also contains forward-looking statements relating to Lexicon's growth and future operating results, discovery and development of products, strategic alliances and intellectual property, as well as other matters that are not historical facts or information. All forward-looking statements are based on management's current assumptions and expectations and involve risks, uncertainties and other important factors, specifically including the risk that clinical studies of telotristat etiprate may be halted, delayed or otherwise not demonstrate safety or efficacy, the risk that Lexicon and its licensees may be unable to file for regulatory approval of telotristat etiprate with the FDA and other regulatory authorities in accordance with its currently anticipated timelines, the risk that the FDA and other regulatory authorities may not grant regulatory approval of telotristat etiprate in accordance with Lexicon's currently anticipated timelines or at all, and the risk that such regulatory approvals, if granted, may have significant limitations on the approved use of telotristat etiprate. As a result, telotristat etiprate may never be successfully commercialized. Other risks include Lexicon's ability to meet its capital requirements, successfully conduct preclinical and clinical development and obtain necessary regulatory approvals of its other potential drug candidates, achieve its operational objectives, obtain patent protection for its discoveries and establish strategic alliances, as well as additional factors relating to manufacturing, intellectual property rights, and the therapeutic or commercial value of its drug candidates. Any of these risks, uncertainties and other factors may cause Lexicon's actual results to be materially different from any future results expressed or implied by such forward-looking statements. Information identifying such important factors is contained under 'Risk Factors' in Lexicon's annual report on Form 10-K for the year ended December 31, 2014, as filed with the Securities and Exchange Commission. Lexicon undertakes no obligation to update or revise any such forward-looking statements, whether as a result of new information, future events or otherwise.

distributed by