Wednesday, October 26, 2016

Student guest post on drug repurposing



Antiques Become Modern
     The repositioning process for drugs means discovering new clinical benefits for a drug that has been already approved to treat other diseases or conditions, according to The National Center for Advancing Translational Sciences, part of the National Institutes of Health (NIH), US Department of Health and Human Services. It has been estimated that 30% of new drugs and vaccines approved by the US FDA in recent years attributes to the process of drug repurposing, repositioning, and rescue. This process offers many advantages including the costs and time saved from circumventing the extensive testing typically required for demonstrating the safety of a newly developed drug. Since these drugs have already been approved for human use, the well characterized properties (pharmacology, toxicology, and formulation) of these candidates allow for the process involved in therapeutic switching to a novel clinical use to occur relatively quickly. Because of the extensive financial commitments and time required for developing a new drug, the goal of bringing a new drug to market with a relatively low cost is very attractive.  The cost associated with the development of a new drug is estimated at over $2 billion, and the timeline typically involves more than 12 - 16 years. In contrast, a repurposed drug can be approved in an extensively shorter time frame, 3- 12 years, with an average cost of $300 million. In addition, approval rates for new drugs are typically close to 10%, but is often 30% for therapeutically switched drugs. Finally, the process of repositioning of drugs could represent substantial assistance for low income patients who have chronic diseases, for example autoimmune lymphoproliferative syndrome (ALPS), since they can obtain their medications for considerably lower prices.

     There are a number of successful drug repurposing stories. Perhaps the most famous stories of a repurposed drug involves thalidomide. Thalidomide had been used to treat morning sickness in pregnant women in the 50s of the last century, then it was withdrawn from markets due to birth deformities. This drug has been synthesized as racemic mixture because it is a chiral compound. Lately, it was discovered that one of the enantiomers (the (R)-(+)-enantiomer) was effective to treat pregnant morning sickness, while, the (S)-(-)-enantiomer made the congenital malformations. Nowadays, this drug has been repurposed and has been approved by FDA to treat leprosy in 1998 and multiple myeloma in 2006. Another success story involves sildenafil. This drug was originally developed to treat hypertension, but it failed during development. However, during clinical trials, it was noticed that sildenafil could improve erectile dysfunction. As a result, it was approved to treat erectile dysfunction. Since that time, sildenafil has been subjected for further re-tasking and is now approved to treat pulmonary hypertension.

References:
1.      I. Agranat, H. Caner, J. Caldwell, “The Thalidomide Tragedy: The Myth of a Missed Opportunity,” Nature Reviews Drug Discovery 1, 753-768 (2002).
3.      28. Joseph A. DiMasi & Henry G. Grabowski, The Cost of Biopharmaceutical R&D: Is Biotech Different?, 28 MANAGERIAL & DECISION ECON. 469, 469 & 475 (2007).

4.      UNITED STATES GOVERNMENT ACCOUNTABILITY OFFICE (GAO), NEW DRUG DEVELOPMENT: SCIENCE, BUSINESS, REGULATORY, AND INTELLECTUAL PROPERTY ISSUES CITED AS HAMPERING DRUG DEVELOPMENT EFFORTS 1 (2006).

Wednesday, October 19, 2016

Another student guest post.....

Does Coffee Cause Dehydration?

     It is well known that intake of very large amounts of caffeine can increase blood flow to the kidneys and inhibit the absorption of sodium and thereby cause dehydration, but do lower doses of coffee also cause dehydration?
     It would be interesting to study whether a medium intake of coffee would cause dehydration. I believe the experiments will not be hard to perform. We would need to recruit two groups of volunteers, probably UK students. Volunteers would be divided into a “coffee group” (participants would consume a daily 32oz coffee containing 660mg caffeine for a week) and a “water group” (participants would consume the same normal amount of water as that of the coffee group and an additional 32oz of water daily for one week). Both groups of volunteers would be on identical diets, sleep/wake cycles and physical activity.
     First, we would determine whether there was a significant change in the total amount of body water at the end of experiments in the two groups. Total body water would be determined following ingestion of deuterium oxide as described previously (1). Second, we would determine whether there is a significant difference between the two groups in serum Na+, serum K+, osmolality and creatinine. Blood for serum would be collected on the mornings of day 1-day 7. Serum Na+ and K+ levels would be analyzed using a ILab600(Diamond Diagnostics). Serum creatinine levels would be analyzed using ilab650 and serum osmolality would be analyzed using advanced Osmometer 765(Advanced Instruments Inc). Third, the 24 h urine volume, urinary Na+ excretion, K+ excretion, urine osmolality, and urine creatinine would be compared between the two groups using the same instrumentation. Urine would be collected on the mornings of day 1-day 7. The results above would help me determine whether medium doses of coffee do cause dehydration.



Reference: 1. Silva A, Judice P, Matias C, Santos D, Magalhaes J, et al. (2013) Total body water and its compartments are not affected by ingesting a moderate dose of caffeine in healthy young adult males. Appl Physiol Nutr Metab Just-IN.

Tuesday, October 11, 2016

Class posting on e-cigarettes

E-Cigarette FAQs


The increasing use of e-cigarettes, particularly in our pediatric population is of concern primarily because of uncertainties surrounding chronic exposures to nicotine and other chemicals.  A recent rule finalized by the FDA in August 8, 2016 will likely affect manufacturers, retailers and consumers of e-cigarettes and e-liquids as follows.   Below are a few FAQs regarding e-cigarettes.

1.  How do the FDA rules affect e-cigarette manufacturers? 
         
          If you make, modify, mix, manufacture, fabricate, assemble, process, label, repack, relabel, or import any “tobacco product,” then you are considered a tobacco product manufacturer.  If you are a tobacco product manufacturer, then you must:
2016
·         Stop distributing products with modified risk claims (other than “light,” “low,” or “mild”) by August 8, 2016.
·         Report user fee information for cigars and pipe tobacco by August 20, 2016.4
·         Pay user fees for cigars and pipe tobacco by December 31, 2016.4
2017
·         Submit tobacco health documents by
o     February 8, 2017 or
o     August 8, 2017 forsmall scale tobacco product manufacturers
·         Submit ingredient listing by:
o     February 8, 2017 or
o     August 8, 2017 forsmall scale tobacco product manufacturers
·         Submit cigar warning plans by May 10, 2017.
·         Apply for and receive a Modified Risk Tobacco Product order from the FDA if you would like to label or advertise your product as "light," "low," or "mild" by September 8, 2017.
·         Submit a premarket application for “new” tobacco products to stay on the via market:3,6
o     Exemption from Substantial Equivalence by August 8, 2017

2018
·         Submit a premarket application for “new” tobacco products to stay on the market via:3,6
o     Substantial Equivalence (SE) by February 8, 2018
o     Premarket Tobacco Applications (PMTA) by August 8, 2018
·         Include Required Warning Statements on Packages and Advertisements on “covered” tobacco products by May 10, 2018.7
2019

2.  How do the FDA rules affect e-cigarette retailers? 
         
          If you sell e-liquids, pipes or cigars, but do NOT mix or prepare e-liquids, make or modify vaporizers, or mix loose tobacco, then you are considered a tobacco retailerRequirements for retailers include:

Beginning August 8, 2016:

·         Only sell tobacco products to customers age 18 and older.
·         Check photo ID of everyone under age 27 who attempts to purchase tobacco products.
·         Do NOT give away free samples, including any components or parts.
·         Do NOT sell in a vending machine unless in an adult-only facility.

Beginning May 10, 2018:
·         Do NOT sell, distribute, or display advertisements for any tobacco product without a health warning statement on the package.


3.  How do the FDA rules affect e-cigarette consumers? 
         
          People who buy or use e-cigarettes will also be affected by this new regulation. These new rules are focused on preventing the use of these products by young people.  They  “…prohibit false and misleading product claims, and prevent new tobacco products from being marketed unless a manufacturer demonstrates that the products meet the relevant public health standard.”  E-cigarette users appearing to be under the age of 27 will have to present photo ID’s when purchasing tobacco products or components to the e-cigarette. If consumers are making, modifying or mixing e-liquids, they will have to comply with the same requirements as the manufacturers.


References:

4.  What are the average nicotine levels and range of nicotine levels that users of e-cigarettes exposed to? 
         
          E-cigarettes typically come in 3, 6, 12, 18, 24, 36 and in some cases up to 54 mg/mL of liquid nicotine.   The dosing corresponds to the level of liquid nicotine. The 18 to 24 mg/mL doses are most comparable to regular cigarettes. It has been found in one study that on average, 50-60% of the nicotine from a cartridge is vaporized although different models of e- cigarettes differ in their efficacy (Goniewicz, et al. 2013).   A review on electronic cigarettes stated one study that found the average aerosolized nicotine level in a 18 mg nicotine cartridge was 82.8 µg nicotine/100 mL aerosol (Schroeder and Hoffman, 2014). According to an article published in 2013 that analyzed sixteen popular e-cigarettes, a range of 0.5 to 15.4 mg from 300 puffs (calculates out to 1.67-51.3 µg/puff) of nicotine was measured in the vapor (Goniewicz et al., 2013).   It is estimated that e-cigarettes can deliver  0.35-43.2 µg nicotine/100 mL puff whereas a Marlboro cigarette delivers 152-193 µg nicotine/100 mL puff (Schroeder and Hoffman, 2014).  Differences in puffing duration when comparing experienced consumers (those using e-cigarettes) and naïve users (regular smokers) also contribute to nicotine level differences in plasma. E-cigarette users were shown to have longer puff durations (4.2 seconds) whereas smokers using the e-cigarette exhibited a similar puffing patter as when they smoke and actual cigarette (approximately2.4 seconds) (Konstantinos, et al. 2015).

References: 
Farsalinos, K.E., et al.,  (2015). Nicotine absorption from electronic cigarette use: comparison between experienced consumers (vapers) and naïve users (smokers).  Scientific Reports 5.
Schroeder, M. J., and Hoffman, A. C. (2014) Electronic cigarettes and nicotine.  Clinical Pharmacology,Tobacco control 23 Suppl 2, ii30-35.
Goniewicz, M. L., Kuma, T., Gawron, M., Knysak, J., and Kosmider, L. (2013) Nicotine levels in electronic cigarettes, Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco 15, 158-166.
5. What is the target of nicotine and how does it signal?
          Nicotine is a tertiary amine consisting of a pyridine and a pyrrolidine ring. (S)-nicotine, found in tobacco, binds stereoselectively to nicotinic cholinergic receptors (nAChRs). (R)-nicotine, found in small quantities in cigarette smoke owing to racemization during the pyrolysis process, is a weak agonist at nAChRs.  When a person inhales smoke from a cigarette, nicotine is  distilled from the tobacco and is carried in smoke particles into the lungs, where it is absorbed rapidly into the pulmonary venous circulation. It then enters the arterial circulation and moves quickly to the brain. Nicotine diffuses readily into brain tissue, where it binds to nAChRs, which are ligand-gated ion channels. When a cholinergic agonist binds to the outside of the channel, the channel opens, allowing the entry of cations, including sodium and calcium. These cations further activate voltage-dependent calcium channels, allowing further calcium entry.  The nAChR complex is composed of five subunits and is found in both the peripheral and central nervous systems. In the mammalian brain, there are as many as nine α subunits (α2 to α10) and three β subunits (β2 to β4). The most abundant receptor subtypes in the brains of humans are α4β2, α3β4, and α7 (homomeric). The α4β2* (asterisk indicates possible presence of other subunits in the receptor) receptor subtype is predominant in the human brain and is believed to be the main receptor mediating nicotine dependence. In mice, knocking out the β2 subunit gene eliminates the behavioral effects of nicotine, such that nicotine no longer releases dopamine in the brain or maintains self-administration. Reinserting the β2 subunit gene into the ventral tegmental area of a β2 knockout mouse restores behavioral responses to nicotine. The α4 subunit appears to be an important determinant of sensitivity to nicotine. In mice, a single nucleotide point mutation in the pore-forming region results in a receptor that is hypersensitive to the effects of nicotine. This mutation makes mice much more sensitive to nicotine-induced reward behaviors, as well as to effects on tolerance and sensitization. The α3β4 nAChR is believed to mediate the cardiovascular effects of nicotine. The homomeric α7 nAChR is thought to be involved in rapid synaptic transmission and may play a role in learning and sensory gating. The α4 β2* receptor may include α5, α6, and/or β3 subunits, which may modulate the sensitivity and function of the receptor. For example, α5 knockout mice are less sensitive to nicotine-induced seizures and hypolocomotion.  Brain imaging studies demonstrate that nicotine acutely increases activity in the prefrontal cortex, thalamus, and visual system, consistent with activation of corticobasal ganglia-thalamic brain circuits. Stimulation of central nAChRs by nicotine results in the release of a variety of neurotransmitters in the brain, most importantly dopamine. Nicotine causes the release of dopamine in the mesolimbic area, the corpus striatum, and the frontal cortex. Of particular importance are the dopaminergic neurons in the ventral tegmental area of the midbrain, and the release of dopamine in the shell of the nucleus accumbens, as this pathway appears to be critical in drug-induced reward. Other neurotransmitters, including norepinephrine, acetylcholine, serotonin, γ-aminobutyric acid (GABA), glutamate, and endorphins,  are released as well, mediating various behaviors of nicotine.
Reference:
Benowitz, Neal L. "Pharmacology of nicotine: addiction, smoking-induced disease, and therapeutics." Annual review of pharmacology and toxicology 49 (2009): 57.

6.  Chronic exposure to nicotine poses a number of adverse effects with addiction being the most prevalent.  In addition, however, nicotine also acts as a tumor promoter.  What are the mechanisms by which nicotine is thought to exert its tumor promoting effects.
          Nicotine can contribute in a variety of ways to cancer survival, growth, metastasis, resistance to chemotherapy, and create a tumor-supporting microenvironment, thus implementing a "second hit" that aggravates aberrant signaling and elicits survival and expansion of cells with genomic damage. The list of cancers reportedly connected to nicotine is expanding, and presently includes small- and non-small cell lung carcinomas as well as head and neck, gastric, pancreatic, gallbladder, liver, colon, breast, cervical, urinary bladder and kidney cancers.
          Nicotine can displace the autocrine and paracrine hormone-like molecule acetylcholine (ACh) from the nicotinic class of ACh receptors (nAChRs) expressed in lung cells due to its higher receptor-binding affinity. ACh is produced practically by all types of human cells, and is remarkably abundant in the lung epithelium. Increasingly, a wider role for ACh in cell biology is being recognized, including proliferation, differentiation, apoptosis, adhesion and motility. The final cellular response to ACh is determined by the delicate balance between the growth- promoting and inhibiting signals. The extracellular pool of ACh is replenished by vesicular ACh transporter secreting the ACh-containing vesicles, whereas the intracellular pool is represented mainly by free cytoplasmic ACh. In human bronchioalveolar carcinoma cells, nicotine upregulates choline acetyltransferase and vesicular ACh transporter, thus increasing production and secretion of ACh. Nicotine also can upregulate nAChR expression, thus shifting ACh signaling in lung cells toward the nicotinic vs. muscarinic physiological signaling pathways. The nAChR subunit proteins can physically associate with both protein kinases and protein tyrosine phosphatases in large multimeric complexes. Even a short-term exposure to nicotine activates mitogenic signaling pathways involving signaling kinases. The nAChRs mediate the nicotine- dependent upregulation of genes contributing to progression of lung cancer. Nicotine can permeate lung cells and activate the mitochondrial (mt-)nAChR subtypes found on the mitochondrial outer membrane of lung cells. Activation of these receptors may inhibit opening of mPTP, which can block the initial step of intrinsic apoptosis. The mPTP is a multi-component protein aggregate comprised by structural elements of the inner as well as outer mitochondrial membrane that form a non-specific pore permeant to any molecule of <1.5 kDa in the outer mitochondrial membrane under conditions of elevated matrix Ca2+. mPTP opening causes massive swelling of mitochondria, rupture of outer membrane and release of intermembrane components that induce intrinsic apoptosis, such as cytochrome c (CytC). Mitochondria become depolarised causing inhibition of oxidative phosphorylation and stimulation of ATP hydrolysis.

Reference:
Chernyavsky, Alex I et al. “Mechanisms of Tumor-Promoting Activities of Nicotine in Lung Cancer: Synergistic Effects of Cell Membrane and Mitochondrial Nicotinic Acetylcholine Receptors.” BMC Cancer 15 (2015): 152. PMC. Web. 15 Sept. 2016.

7.  What are some of the most popular flavors of e-cigarettes?
          One website lists the most popular flavors as: Fruit (30%), Tobacco (22%), Dessert/Bakery (19%), other – DIY or flavorless (7%), Menthol (mint/peppermint) (6%), Spicy/Savory (5%), Candy (4%), Menthol (3%), Beverage (3%), all (1%).
Reference:
http://ecigclopedia.com/10-most-popular-e-liquid-flavors-used-by-vapers/

8.   In addition to nicotine, what other chemicals can be found in e-cigarettes?
          Chemicals detected in e-cigarette liquid include, but not limited to: propylene glycol, 3,4- dimethoxybenzaldehyde, methyl cyclopentanolone, ethyl maltol, 3-methylcycopentane-1,2-dione, 5- methyl-2-phenylhex-2-enal, 2,5-dimenthylpyrazine, formaldehyde, acetaldehyde,  nitrosoamines (NNN, NNK, NAT, and NAB).   Chemicals detected in e-cigarette vapor include, but not limited to: p,m-xylene, glycerine, acrolein, toluene, nitrosamines, pyrene, 1-methyl-phenanthrene, phenanthrene, cadmium, nickel, lead, chromium, formaldehyde, acetaldehyde, acetone, NNN, and NNK.   Of these, those of the most concern include nitrosamines, heavy metals and formaldehyde.
References:
Kavvalakis, M. P., Stivaktakis, P. D., Tzatzarakis, M. N., Kouretas, D., Liesivuori, J., Alegakis, A. K., Vynias, D., and Tsatsakis, A. M. (2015) Multicomponent analysis of replacement liquids of electronic cigarettes using chromatographic techniques, Journal of analytical toxicology 39, 262- 269.
Cheng, T. (2014) Chemical evaluation of electronic cigarettes, Tobacco control 23 Suppl 2, ii11-17.
Goniewicz, M. L., Knysak, J., Gawron, M., Kosmider, L., Sobczak, A., Kurek, J., Prokopowicz, A.,
Jablonska-Czapla, M., Rosik-Dulewska, C., Havel, C., Jacob, P., 3rd, and Benowitz, N. (2014) Levels of selected carcinogens and toxicants in vapour from electronic cigarettes, Tobacco control 23, 133-139.