A mechanistically novel peptide agonist of the IL-7 receptor that addresses limitations of IL-7 cytokine therapy.

Interleukin (IL)-7 is broadly active on T-cell populations, and modified versions have been clinically evaluated for a variety of therapeutic applications, including cancer, lymphopenia, and infectious diseases; and found to be relatively well-tolerated and biologically active. Here we describe novel IL-7R agonists that are unrelated in structure to IL-7, bind to the receptor subunits differently from IL-7, but closely emulate IL-7 biology. The small size, low structural complexity, and the natural amino acid composition of the pharmacologically active peptide MDK1472 allows facile incorporation into protein structures, such as the IgG2-Fc fusion MDK-703. This molecule possesses properties potentially better suited to therapeutic applications than native IL-7 or its derivatives. We compared these compounds with IL-7 for immune cell selectivity, induction of IL-7R signaling, receptor-mediated internalization, proliferation, and generation of immune cell phenotypes in human and non-human primate (NHP) peripheral blood cells in vitro; and found them to be similar in biological activity to IL-7. In cynomolgus macaques, MDK-703 exhibits a circulating half-life of 46 hr and produces sustained T-cell expansion characteristic of IL-7 treatment. In the huCD34+-engrafted NSG mouse model of the human immune system, MDK-703 induces an immune cell profile very similar to that generated by IL-7-derived compounds; including the pronounced expansion of memory T-cells, particularly the population of stem-like memory T-cells (Tscm) which may be important for anti-tumor activities reported with IL-7 treatment. Clinical administration of IL-7 and modified variants has been reported to induce anti-drug antibodies (ADAs), including IL-7 neutralizing antibodies. The novel peptide agonist reported here scores very low in predicted immunogenicity, and because the peptide lacks sequence similarity with IL-7, the problematic immunogenic neutralization of endogenous cytokine should not occur. The properties we report here implicate MDK-703 as a candidate for clinical evaluation in oncology, anti-viral and other infectious disease, vaccine enhancement, and treatment of lymphopenia.

Dose response of Gabapentin Enacarbil versus placebo in subjects with moderate-to-severe primary restless legs syndrome: an integrated analysis of three 12-week studies.

BACKGROUND: The efficacy and tolerability of gabapentin enacarbil (Horizant®; GlaxoSmithKline, Brentford, UK) has been demonstrated in several restless legs syndrome (RLS) phase II and phase III clinical studies at various doses from 600 mg to 2400 mg. OBJECTIVE: The objective of this study was to evaluate key efficacy and safety outcomes in subjects with RLS treated with once-daily gabapentin enacarbil 600 mg, 1200 mg, 1800 mg and 2400 mg, providing supportive evidence of the efficacy of gabapentin enacarbil 600 mg compared with higher doses and placebo. STUDY DESIGN: Integrated post hoc analysis of three 12-week, randomized, double-blind, placebo-controlled trials in subjects with RLS. SETTING: The three studies were carried out at multiple centres in the US. PATIENTS: In total, 760 subjects were included in the pooled analysis (placebo, n = 245; gabapentin enacarbil 600 mg, n = 163; gabapentin enacarbil 1200 mg, n = 269; gabapentin enacarbil 1800 mg, n = 38; gabapentin enacarbil 2400 mg, n = 45). INTERVENTION: In all studies, gabapentin enacarbil or placebo was administered once daily at approximately 5 p.m. with food. Gabapentin enacarbil was initiated at a dose of 600 mg with subsequent titration in 600 mg increments every 3 days up to the randomized dose. MAIN OUTCOME MEASURE: The efficacy endpoints analysed for the purpose of this integrated analysis were change from baseline in International Restless Legs Scale (IRLS) total score and the proportion of responders (subjects rated as 'much' or 'very much' improved) on the investigator-rated Clinical Global Impression-Improvement (CGI-I) scale. Safety endpoints assessed were the incidence of treatment-emergent adverse events (AEs) and serious AEs. RESULTS: Gabapentin enacarbil 600 mg significantly improved IRLS total score compared with placebo (adjusted mean [standard error] change in IRLS total score from baseline to week 12 last observation carried forward: -13.6 [0.71] vs -9.3 [0.55]; adjusted mean treatment difference: -4.3; 95% CI -6.01, -2.52; p < 0.0001). A significantly higher proportion of subjects was rated as responders on the investigator-rated CGI-I scale with gabapentin enacarbil 600 mg compared with placebo (70.2% vs 42.2%; adjusted odds ratio 3.1; 95% CI 1.96, 4.89; p < 0.0001). Similar treatment benefits were seen with both efficacy endpoints for the three higher doses. The AEs reported most frequently were somnolence and dizziness; there was a dose-response relationship to these AEs. No new or unexpected safety issues were identified by this integrated analysis. CONCLUSION: The lowest dose of gabapentin enacarbil evaluated (600 mg) significantly improved RLS symptoms compared with placebo. The safety profile was consistent with that described previously in the literature.

A randomized, double-blind, placebo-controlled study to assess the efficacy and tolerability of gabapentin enacarbil in subjects with restless legs syndrome.

STUDY OBJECTIVE: To evaluate the efficacy and tolerability of gabapentin enacarbil (GEn) 1200 mg or 600 mg compared with placebo in subjects with moderate-to-severe primary restless legs syndrome (RLS). METHODS: This 12-week, multicenter, double-blind, placebo-controlled study randomized subjects (1:1:1) to GEn 1200 mg, 600 mg, or placebo. Co-primary endpoints: mean change from baseline in International Restless Legs Scale (IRLS) total score and proportion of responders (rated as "very much" or "much" improved) on the investigator-rated Clinical Global Impression-Improvement scale (CGI-I) at Week 12 LOCF for GEn 1200 mg compared with placebo. Secondary endpoints included GEn 600 mg compared with placebo on the IRLS and CGI-I at Week 12 LOCF and subjective measures for sleep. Safety and tolerability assessments included adverse events. RESULTS: 325 subjects were randomized (GEn 1200 mg = 113; 600 mg = 115; placebo = 97). GEn 1200 mg significantly improved mean [SD] IRLS total score at Week 12 LOCF (baseline: 23.2 [5.32]; Week 12: 10.2 [8.03]) compared with placebo (baseline: 23.8 [4.58]; Week 12: 14.0 [7.87]; adjusted mean treatment difference [AMTD]: -3.5; p = 0.0015), and significantly more GEn 1200 mg-treated (77.5%) than placebo-treated (44.8%) subjects were CGI-I responders (p < 0.0001). Similar significant results were observed with GEn 600 mg for IRLS (AMTD: -4.3; p < 0.0001) and CGI-I (72.8% compared with 44.8%; p < 0.0001). GEn also significantly improved sleep outcomes (Post-Sleep Questionnaire, Pittsburgh Sleep Diary and Medical Outcomes Sleep Scale) compared with placebo. The most commonly reported adverse events were somnolence (GEn 1200 mg = 18.0%; 600 mg = 21.7%; placebo = 2.1%) and dizziness (GEn 1200 mg = 24.3%; 600 mg = 10.4%; placebo = 5.2%). Dizziness increased with increased dose and led to discontinuation in 2 subjects (GEn 1200 mg, n = 1; GEn 600 mg, n = 1). Somnolence led to discontinuation in 3 subjects (GEn 600 mg). CONCLUSIONS: GEn 1200 mg and 600 mg significantly improve RLS symptoms and sleep disturbance compared with placebo and are generally well tolerated.

Long-term maintenance treatment of restless legs syndrome with gabapentin enacarbil: a randomized controlled study.

OBJECTIVE: To assess maintenance of efficacy and tolerability of gabapentin enacarbil in patients with moderate to severe primary restless legs syndrome (RLS). PATIENTS AND METHODS: This study (conducted April 18, 2006, to November 14, 2007) comprised a 24-week, single-blind (SB) treatment phase (gabapentin enacarbil, 1200 mg) followed by a 12-week randomized, double-blind (DB) phase. Responders from the SB phase (patients with improvements on the International Restless Legs Scale [IRLS] and investigator-rated Clinical Global Impression-Improvement scale at week 24 and stable while taking a gabapentin enacarbil dose of 1200 mg for at least 1 month before randomization) were randomized to gabapentin enacarbil, 1200 mg, or placebo once daily at 5 pm with food. The primary end point was the proportion of patients experiencing relapse (worse scores on the IRLS and investigator-rated Clinical Global Impression of Change scale on 2 consecutive visits at least 1 week apart or withdrawal because of lack of efficacy) during the DB phase. RESULTS: A total of 221 of 327 patients completed the SB phase, 194 (96 in the gabapentin enacarbil group and 98 in the placebo group) were randomized to DB treatment, and 168 (84 in the gabapentin enacarbil group and 84 in the placebo group) completed the DB phase. A significantly smaller proportion of patients treated with gabapentin enacarbil (9/96 [9%]) experienced relapse compared with the placebo-treated patients (22/97 [23%]) (odds ratio, 0.353; 95% confidence interval, 0.2-0.8; P=.02). Somnolence and dizziness were the most common adverse events. One death occurred (unintentional choking during the SB phase) and was judged as being unrelated to the study drug. No clinically relevant changes were observed in laboratory values, in vital signs, or on electrocardiograms. CONCLUSION: Gabapentin enacarbil, 1200 mg, maintained improvements in RLS symptoms compared with placebo and showed long-term tolerability in adults with moderate to severe primary RLS for up to 9 months of treatment.

Gabapentin enacarbil in restless legs syndrome: a phase 2b, 2-week, randomized, double-blind, placebo-controlled trial.

OBJECTIVES: Assess the efficacy and tolerability of gabapentin enacarbil (GEn), a transported prodrug of gabapentin with improved gabapentin exposure, in adults with moderate-to-severe primary restless legs syndrome. METHODS: This 14-day, double-blind, randomized, controlled trial of GEn at 1200 or 600 mg or placebo taken once daily, evaluated the mean change from baseline International Restless Legs Scale (IRLS) total score at end of treatment (day 14:primary comparison, GEn at 1200 mg vs placebo). Secondary end points included Clinical Global Impression-Improvement scale outcomes at day 14. RESULTS: Ninety-five subjects were randomized (GEn: 1200 mg, n = 33 and 600 mg, n = 29; placebo, n = 33); 2 subjects (GEn at 1200 mg) withdrew because of adverse events. At day 14,the mean (SD) change from baseline IRLS total score was significantly greater with GEn at 1200 mg (-16.1 [7.93]) compared with placebo (-8.9 [7.72]; adjusted mean treatment difference, -7.2; P < 0.0001). Investigator-rated Clinical Global Impression-Improvement scale responses also significantly favored GEn at 1200 mg compared with placebo (P G 0.0001).The mean (SD) change from baseline IRLS total score with GEn at 600 mg at day 14 was -9.1 (5.95), similar to placebo. The most commonly reported treatment-emergent adverse events were somnolence (GEn: 1200 mg, 36% and 600 mg, 14%; placebo,15%) and dizziness (GEn: 1200 mg, 18% and 600 mg, 14%; placebo, 3%), most of which were rated mild or moderate in intensity. CONCLUSIONS: Gabapentin enacarbil at 1200 mg significantly improved restless legs syndrome symptoms compared with placebo. Efficacy outcomes for GEn at 600 mg were similar to placebo. Both GEn doses were generally well tolerated.

A randomized, double-blind, placebo-controlled, crossover study of XP13512/GSK1838262 in the treatment of patients with primary restless legs syndrome.

STUDY OBJECTIVE: To evaluate the efficacy and tolerability of XP13512/ GSK1838262, an investigational nondopaminergic agent for the treatment of moderate-to-severe primary restless legs syndrome (RLS). DESIGN: Randomized, double-blind, placebo-controlled, crossover trial. SETTING: Nine US clinical sites. PATIENTS: Thirty-eight treatment-naive subjects with RLS (mean +/- SD age 50.1 +/- 13.2 years). INTERVENTIONS: XP13512 1800 mg/day followed by placebo or placebo followed by XP13512 1800 mg/day for 14 days, with a 7-day washout between treatment periods. MEASUREMENTS AND RESULTS: The primary endpoint was mean change from baseline International RLS Study Group rating scale (IRLS) total score on Day 14, analyzed using analysis of variance with sequence, period, and treatment as fixed effects and subjects within sequence as a random effect. XP13512 significantly reduced IRLS total score on Day 14 compared with placebo (mean +/- SD: XP13512 -12.1 +/-6.5, placebo -1.9 +/- 6.3; P < 0.0001). Polysomnographic data showed that XP13512 significantly improved sleep architecture on Day 14 compared with placebo (mean +/- SD change from baseline sleep time [minutes]: stage 1: XP13512 -9.8 +/- 23.9, placebo 0.4 +/-23.2; adjusted P<0.0054, nominal P<0.0001; stage 3/4 (slow-wave sleep): XP13512 22.8 +/- 40.8, placebo 1.4 +/- 34.3; adjusted P=0.0092, nominal P=0.0002). The most frequently reported adverse events were somnolence (XP13512 30.6%, placebo 2.8%) and dizziness (XP13512 27.8%, placebo 5.6%). CONCLUSIONS: XP13512 1800 mg/day significantly reduced RLS symptoms, improved sleep, and was generally well tolerated in subjects with moderate-to-severe primary RLS across 14 days of treatment.

Allosteric activation of the follicle-stimulating hormone (FSH) receptor by selective, nonpeptide agonists.

The pituitary glycoprotein hormones, luteinizing hormone and follicle-stimulating hormone (FSH), act through their cognate receptors to initiate a series of coordinated physiological events that results in germ cell maturation. Given the importance of FSH in regulating folliculogenesis and fertility, the development of FSH mimetics has been sought to treat infertility. Currently, purified and recombinant human FSH are the only FSH receptor (FSH-R) agonists available for infertility treatment. By screening unbiased combinatorial chemistry libraries, using a cAMP-responsive luciferase reporter assay, we discovered thiazolidinone agonists (EC50's = 20 microm) of the human FSH-R. Subsequent analog library screening and parallel synthesis optimization resulted in the identification of a potent agonist (EC50 = 2 nm) with full efficacy compared with FSH that was FSH-R-selective and -dependent. The compound mediated progesterone production in Y1 cells transfected with the human FSH-R (EC50 = 980 nm) and estradiol production from primary rat ovarian granulosa cells (EC50 = 10.5 nm). This and related compounds did not compete with FSH for binding to the FSH-R. Use of human FSH/thyroid-stimulating hormone (TSH) receptor chimeras suggested a novel mechanism for receptor activation through a binding site independent of the natural hormone binding site. This study is the first report of a high affinity small molecule agonist that activates a glycoprotein hormone receptor through an allosteric mechanism. The small molecule FSH receptor agonists described here could lead to an oral alternative to the current parenteral FSH treatments used clinically to induce ovarian stimulation for both in vivo and in vitro fertilization therapy.

XP13512 [(+/-)-1-([(alpha-isobutanoyloxyethoxy)carbonyl] aminomethyl)-1-cyclohexane acetic acid], a novel gabapentin prodrug: I. Design, synthesis, enzymatic conversion to gabapentin, and transport by intestinal solute transporters.

Gabapentin is thought to be absorbed from the intestine of humans and animals by a low-capacity solute transporter localized in the upper small intestine. Saturation of this transporter at doses used clinically leads to dose-dependent pharmacokinetics and high interpatient variability, potentially resulting in suboptimal drug exposure in some patients. XP13512 [(+/-)-1-([(alpha-isobutanoyloxyethoxy)carbonyl] aminomethyl)-1-cyclohexane acetic acid] is a novel prodrug of gabapentin designed to be absorbed throughout the intestine by high-capacity nutrient transporters. XP13512 was stable at physiological pH but rapidly converted to gabapentin in intestinal and liver tissue from rats, dogs, monkeys, and humans. XP13512 was not a substrate or inhibitor of major cytochrome P450 isoforms in transfected baculosomes or liver homogenates. The separated isomers of XP13512 showed similar cleavage in human tissues. The prodrug demonstrated active apical to basolateral transport across Caco-2 cell monolayers and pH-dependent passive permeability across artificial membranes. XP13512 inhibited uptake of (14)C-lactate by human embryonic kidney cells expressing monocarboxylate transporter type-1, and direct uptake of prodrug by these cells was confirmed using liquid chromatography-tandem mass spectrometry. XP13512 inhibited uptake of (3)H-biotin into Chinese hamster ovary cells overexpressing human sodium-dependent multivitamin transporter (SMVT). Specific transport by SMVT was confirmed by oocyte electrophysiology studies and direct uptake studies in human embryonic kidney cells after tetracycline-induced expression of SMVT. XP13512 is therefore a substrate for several high-capacity absorption pathways present throughout the intestine. Therefore, administration of the prodrug should result in improved gabapentin bioavailability, dose proportionality, and colonic absorption compared with administration of gabapentin.

XP13512 [(+/-)-1-([(alpha-isobutanoyloxyethoxy)carbonyl] aminomethyl)-1-cyclohexane acetic acid], a novel gabapentin prodrug: II. Improved oral bioavailability, dose proportionality, and colonic absorption compared with gabapentin in rats and monkeys.

The absorption of gabapentin (Neurontin) is dose-dependent and variable between patients. Rapid clearance of the drug necessitates dosing three or more times per day to maintain therapeutic levels. These deficiencies appear to result from the low capacity, limited intestinal distribution, and variable expression of the solute transporter responsible for gabapentin absorption. Saturation of this transporter at doses used clinically leads to unpredictable drug exposure and potentially ineffective therapy in some patients. XP13512 [(+/-)-1-([(alpha-isobutanoyloxyethoxy)carbonyl]aminomethyl)-1-cyclohexane acetic acid] is a novel prodrug of gabapentin designed to be absorbed by high-capacity nutrient transporters located throughout the intestine. XP13512 was efficiently absorbed and rapidly converted to gabapentin after oral dosing in rats and monkeys. Exposure to gabapentin was proportional to prodrug dose, whereas exposure to intact XP13512 was low. In rats, >95% of an oral dose of (14)C-XP13512 was excreted in urine in 24 h as gabapentin. In monkeys, oral bioavailability of gabapentin from XP13512 capsules was 84.2% compared with 25.4% after a similar oral Neurontin dose. Compared with intracolonic gabapentin, intracolonic XP13512 gave a 17-fold higher gabapentin exposure in rats and 34-fold higher in monkeys. XP13512 may therefore be incorporated into a sustained release formulation to provide extended gabapentin exposure. XP13512 demonstrated improved gabapentin bioavailability, increased dose proportionality, and enhanced colonic absorption. In clinical use, XP13512 may improve the treatment of neuropathic pain, epilepsy, and numerous other conditions by increasing efficacy, reducing interpatient variability, and decreasing frequency of dosing.

Agonists of the follicle stimulating hormone receptor from an encoded thiazolidinone library.

The design, synthesis, characterization, and screening of a large, encoded thiazolidinone library are described. Three sets of 35 building blocks were combined by encoded split-pool synthesis to give a library containing more than 42 000 members. Building block selection was based in part on a novel small molecule follicle stimulating hormone receptor agonist hit and in part for diversity. HPLC/MS techniques were applied at the single-bead level to build confidence in the reliability of library construction. Application of two distinct screening strategies resulted in the identification of compounds with significantly improved potency over the initial hit. This work demonstrates the versatility of encoded libraries for preparing a large number of analogues of a given hit while simultaneously generating a large collection of compounds for screening against other targets.

Synthetic compound libraries displayed on the surface of encoded bacteriophage.

We describe a technology for attaching libraries of synthetic compounds to coat proteins of bacteriophage particles such that the identity of the chemical structure is encoded in the genome of the phage, analogous to peptides displayed on phage surfaces by conventional phage-display techniques. This format allows a library of synthetic compounds to be screened very efficiently as a single pool. Encoded phage serve as extremely robust reporters of the presence of each compound, providing exquisite sensitivity for identification of active compounds engaged in complex biological processes such as receptor-mediated endocytosis and transcytosis. To evaluate this approach, we constructed a library of 980 analogs of folic acid displayed on T7 phage, and demonstrated rapid identification of compounds that bind to folate receptor and direct endocytosis of associated phage particles into cells that express the targeted receptor.