mGlu5 negative allosteric modulators: a patent review (2010 – 2012)

Introduction: The design and development of small molecule negative allosteric modulators (NAMs) of the metabotropic glutamate receptor subtype 5 (mGlu₅) has been an area of intense interest for over a decade. Potential roles have been established for mGlu₅ NAMs in the treatment of diseases such as pain, anxiety, gastroesophageal reflux disease (GERD), Parkinson's disease levodopa-induced dyskinesia (PD-LID), fragile X syndrome (FXS), autism, addiction, and depression.

Areas covered: This review begins with an update of the clinical trial efforts with mGlu₅ NAMs. Following that update, the review summarizes small molecule mGlu₅ NAM patent applications published between 2010 and 2012. These summaries are subdivided into three separate groups: inventions related to improvements in drug properties and/or developability, new chemical entities that contain a disubstituted alkyne, and new chemical entities that do not contain a disubstituted alkyne.

Expert opinion: Given the abundant promise found within the mGlu₅ NAM field, optimism remains that a drug will emerge from this therapeutic class. Still, the launch of a new drug is far from a certainty. It is encouraging to observe the ever-increasing chemical diversity among mGlu₅ NAMs. Finally, in spite of the mature nature of this field, room remains for new advancements.     

Voltage-gated sodium channels: the search for subtype-selective analgesics

Background: Primary afferent or sensory neurons innervate almost all the tissues of the body. They are vital in receiving sensory information and conveying this to the spinal cord and subsequently to the brain, where the higher centres convert this afferent input into an ‘understanding’ of its nature. The nociceptors are a subset of sensory neurons responsible for the transmission of ‘painful’ stimuli into the CNS. Objective/methods: Voltage-gated sodium channels (VGSCs) are pivotal in the transduction of noxious signals at the terminals of the nociceptors and the transmission of the signal along the axon and into the spinal cord and brain. There are nine functional members of the VGSC family. This review aims to briefly summarise the biology of the family, discuss those VGSCs involved in the transduction and transmission of nociceptive signals and to highlight the potential and also the challenges in seeking subtype-selective VGSC modulators for the effective treatment of pain. Results/conclusion: Robust evidence from preclinical models – and better yet, overwhelming human clinical genetic data – provides a compelling rationale for the involvement of VGSCs in nociceptive processing. Some compounds showing a low degree of subtype selectivity have been progressed into clinical development, but the results have been disappointing. It is likely that the high degree of structural homology within the VGSC family is a causative factor in making the discovery of subtype-selective modulators extremely challenging. A much greater understanding of the structure – function relationship for VGSCs and pharmacological modulators is needed if we are to design the compounds that will target those channels involved in nociceptive signalling whilst sparing those in the heart and brain. Only then will we be able to deliver a quantum leap in analgesic pharmacotherapy, providing the effective and well-tolerated drugs that the patient needs.     

Bazedoxifene: a new selective estrogen receptor modulator for the treatment of postmenopausal osteoporosis

Bazedoxifene acetate (WAY-140424; TSE-424) is an oral, nonsteroidal, indole-based selective estrogen receptor modulator (SERM) being developed for the prevention and treatment of osteoporosis. Preclinical studies on bazedoxifene have demonstrated estrogen agonist effects on the skeleton and lipid metabolism but not on breast and uterine endometrium. In combination with estrogen, bazedoxifene antagonizes the stimulatory action of estrogens on proliferation of breast cancer cells and endometrium. Phase III clinical studies have shown favorable effects on the skeleton without stimulation of endometrium and breast. Bazedoxifene prevents bone loss in postmenopausal women without osteoporosis and reduces vertebral fractures in women with postmenopausal osteoporosis. In women at high risk of fracture with multiple risk factors, bazedoxifene reduces nonvertebral fracture risk in post-hoc analysis. Bazedoxifene in combination with conjugated estrogens represents a new form of therapeutic agents for the treatment of postmenopausal symptoms and prevention of postmenopausal osteoporosis. Clinical trials with bazedoxifene/conjugated estrogens have shown beneficial effects on bone mineral density and bone turnover markers with improvement in vasomotor symptoms and little or no stimulation of breast and endometrium.     

Trilostane in advanced breast cancer

Antiestrogens, principally tamoxifen, and aromatase inhibitors have been used as the first- and second-line therapy in patients with advanced postmenopausal breast cancer for many years. However, some patients acquire resistance to these treatments and, at present, further endocrine treatment is achieved by merely substituting the current medication with a different antiestrogen or aromatase inhibitor. Trilostane offers an alternative endocrine treatment due to its unique mode of action. It is an allosteric modulator of the estrogen receptor and targets both the estrogen- and growth factor-dependent pathways through which estradiol stimulates cell proliferation. In clinical trials, trilostane has been shown to be an effective treatment for breast cancer in patients who have relapsed after receiving treatment with one or more forms of endocrine therapy. Ongoing and future clinical trials are examining the potential for the use of trilostane in premenopausal breast cancer, as well as in other malignancies such as prostate cancer.     

Considering the economic principles of pharmaceutical R&D

Importance of the field: Virtual screening (VS) coupled with structural biology is a significantly important approach to increase the number and enhance the success of projects in lead identification stage of drug discovery process. Recent advances and future directions in estrogen therapy have resulted in great demand for identifying the potential estrogen receptor (ER) modulators with more activity and selectivity.

Areas covered in this review: This review presents the current state of the art in VS and structure–activity relationship of ER modulators in recent discovery, and discusses the strengths and weaknesses of the technology.

What the reader will gain: Readers will gain an overview of the current platforms of in silico screening for discovery of ER modulators; they will learn which structural information is significantly correlated with the bioactivity of ER modulators and what novel strategies should be considered for the creation of more effective chemical structures.

Take home message: With the goal of reducing toxicity and/or improving efficacy, challenges to the successful modeling of endocrine agents are proposed, providing new paradigms for the design of ER inhibitors.     

积雪草苷防治支架再狭窄的生化调节机制

目的：探讨积雪草苷能否作为生化调节剂,有效减轻内皮细胞损伤,进一步抑制支架术后内中膜增生。方法：选取原代人主动脉平滑肌细胞和主动脉成纤维细胞各1株,每株细胞设空白对照组、雷帕霉素组（Rapa）、积雪草苷组（At）、积雪草苷+雷帕霉素组。利用qRT-PCR检测平滑肌细胞和成纤维细胞TGF-β1（转化生长因子1）,Smad7,Ⅰ型胶原基因表达水平,通过ELISA检测Ⅰ型胶原蛋白表达量,计算积雪草苷和雷帕霉素两药相互作用指数（CDI）。另将16只中华小型猪随机分为A,B 2组,前降支球囊大压力预扩后,植入同型雷帕霉素支架1枚。术后A组予生理盐水30 mL·d^-1静脉注射;B组予积雪草苷30 mg·kg^-1·d^-1 （生理盐水稀释至30 mL）静注。术后7,14 d ELISA法检测2组血浆vWF（血管性血友病因子）表达水平;术后28 d复查冠脉造影,取支架血管段组织切片及染色,计算血管面积、支架内面积、管腔面积和新生内膜面积。结果：与对照组相比,两药联合组显著上调平滑肌细胞和成纤维细胞Smad7基因,下调TGF-β1,显著抑制Ⅰ型胶原基因表达（P<0.01）;平滑肌细胞中,两药联合组与Rapa组对Ⅰ型胶原抑制无显著性差异,CDI为0.83;成纤维细胞中,两药联合组优于Rapa 组,存在显著性差异（P<0.05）,CDI为0.77。小型猪术后7,14 d,B组血浆vWF水平均显著低于A组（P<0.05）;术后28 d,2组血管面积和支架内面积无统计学差异;B组管腔面积显著大于A组（P<0.05）,B组新生内膜面积显著小于A组（P<0.05）。结论：积雪草苷通过上调Smad7蛋白表达,抑制TGF-β1表达,显著减少胞外基质合成与分泌,进一步抑制支架术后内中膜增生,减轻内皮细胞损伤,是雷帕霉素的有效生化调节剂。     

雷诺昔酚对去势后大鼠骨密度、血生化指标的影响

目的:研究选择性雌激素受体调节剂(SERM)雷诺昔酚(RAL)对去势后雌性大鼠血生化及骨密度(BMD)的影响.方法:将5 mo龄未经产雌性二级SD大鼠24只,随机分为假手术(Sham)组、去势(OVX)组、去势 RAL(OVX RAL)组.OVX RAL组大鼠术后7 d开始给药.术后16wk处死各组大鼠,对各组大鼠血生化指标、BMD进行检测,并进行骨组织形态学观察.结果:OVX组与Sham组相比较,血钙(Ca2 )明显增高[(3.02±0.38)mmol/Lvs(2.24±0.30)mmol/L,P＜0.01],血碱性磷酸酶(ALP)升高[(2.336±0.032)μkat/Lvs(1.832±0.028)μkat/L,P＜0.05],血磷(P)无明显差异.OVX RAL治疗组与OVX组相比,血清Ca ,ALP均降低[(2.38±0.39)mmol/Lvs(3.02±0.38)mmol/L,(1.952±0.023)μkat/Lvs(2.336±0.032)μkat/L,P＜0.05],血P无明显差异.与Sham组相比,OVX组股骨近端[(0.181±0.021)g/cm2vs(0.287±0.025)g/cm2]、股骨干[(0.157±0.034)g/cm2vs(0.260±0.039)g/cm2]及腰椎BMD明显降低(P＜0.01);OVX RAL治疗组各部位BMD高于OVX组(P＜0.05),但未达到Sham组水平(P＞0.05).结论:去势后16 wk大鼠松质骨、皮质骨骨量、骨组织形态计量学指标均明显下降.经RAL治疗后的去势大鼠松质骨、皮质骨密度、骨组织形态计量学指标得到较好维持.     

选择性雄激素受体调节剂（Sarm）对雄性骨质疏松大鼠骨的影响

目的评估S-3-（4-acetylamino-phenoxy）-2-hydroxy-2-methyl-N-（4-nitro-3-trinuoromethyl-phenyl）-propionamide（Sann）对雄性骨质疏松大鼠的疗效。方法建立大鼠骨质疏松模型,皮下注射二氢睾酮（DHT）和Sarm治疗12周,测量骨密度（BMD）、骨生物力学、骨代谢相关血清生化指标和前列腺重量,综合评价Sarm对骨质疏松大鼠的疗效。结果与去势组相比,Sarm中、高剂量可以显著提高去势大鼠骨密度、生物力学参数,降低血清骨源性碱性磷酸酶（BALP）活性,未引起前列腺明显增生。结论Sarm能促进骨形成、防止骨量丢失,为骨质疏松的治疗提供了一种新方案。     

Human sweet taste receptor mediates acid-induced sweetness of miraculin

Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity.