Monday, September 30, 2019

Kesendirian: Sebuah Awal dan Akhir Perjalanan

[Sumber Gambar: Medical Express]


Seketika aku tak mampu mengucapkan sepatah kata pun ketika orang-orang di sekeliling terus menyebut namaku. Aku menjawab setiap pertanyaan mereka dengan gugup. Sungguh, ini merupakan pertama kalinya aku menginjakkan tanah yang baru, suasana yang berbeda, jauh dari rumah. Aku baru mengetahui, sesulit itu ternyata keluar dari zona nyamanku. 

Kupikir aku sudah cukup berani berbicara di depan, setelah sudah berapa kali berbicara di depan publik. Ternyata, lingkungan yang baru ini mampu membungkam suaraku. Benar-benar tidak nyaman. Orang-orang baru, kurindu rumah...

Seminggu kulewati dengan air mata. Di bawah selimut kuteringat wajah ibu bapakku, kumimpikan suasana rumah. Rasanya aku ingin pulang.

Seperti ini ternyata, kurasa kodrat anak bungsu yang melekat pada diriku tidak mudah dihilangkan. Kupikir, aku sudah bisa mandiri, kupikir aku sudah bisa kuat sendiri. Ternyata, lemah sekali diriku. Di saat itu, aku merasakan titik terlemah yang ada di dalam diriku. 

Segugup itu kah? Mampu kah? Kuat kah? Kucoba menguatkan diri, tapi terus kalah dengan air mata yang terus mendorong keluar, tak tertahankan.

Kujalani minggu-minggu pertama, kusapa dengan pelan guruku. Namun, aku tak mampu merasakan kehangatan. Kenapa, di dalam juga dingin, kupikir hanya di luar hawa dingin itu. Rasanya kutak ingin melepas jaket tebalku, tapi beliau berkata, "tidak mau melepas jaket kah?". Aku yang sedari tadi dihinggapi dengan kecemasan, menanggapi muram, menganggap bahwa perkataan itu seperti hentakan. 

Segera kulepas dan kugantungkan ke kursi. Dengan gaya yang masih awkward dan sedikit celingak celinguk, kuperhatikan sekeliling. Kuberharap untuk menemui keramahan. 

Minggu-minggu kulewati dengan observasi yang makin membuat jiwaku tergoncang. Perkataan-perkataan kasar yang dilontarkan ke setiap orang-orang baru yang kukenal, membuatku berpikir, akankah aku menerima perlakukan yang sama. 

Sungguh, jiwa lemahku meronta. Tak sanggup jika aku berada di posisinya. Bergetar sudah. Momen-momen itu terulang kembali tiap minggu. Aku merasa sedih tambah kasihan. Tidak seharusnya diperlakukan begini, ada caranya untuk evaluasi. Seperti ini kah mereka?

Tiba saatnya aku mendapat kesempatan bertanya. Bukannya mendapat apresiasi melontarkan pertanyaan, malah kudapat cacian. Saat itu, tubuhku berusaha menerima, aku terdiam, tanpa berontak. Aku tau, aku lemah, tapi di saat itu, aku berusaha menunjukkan bahwa aku tegar. Bahwa aku baik-baik saja.

Minggu berganti minggu, dalam sebulan aku dihantui dengan kekhawatiran. Seperti ini kah? Aku harus bagaimana? Apa yang harus aku lakukan? Aku hanya ingin kenyamanan, aku hanya ingin pengertian. 

Kuisi kuesioner, dari satu sampai lima, kupilih 2 untuk sebuah soal yang meminta gambaran kesehatan jiwa. Aku jujur, aku tak ada pilihan. 

Kudapati kesempatan bercerita, dengan seseorang yang mengenal mereka. Katanya, seharusnya mereka tidak seperti yang aku khawatirkan. Sehingga berkali-kali aku diminta untuk tidak perlu khawatir. Melainkan, harusnya aku bersyukur.

Kucoba untuk memahami, kucoba untuk mengerti, kemudian kucoba untuk mengikuti. Semua instruksi aku lakukan, bahkan aku lakukan lebih dari yang diminta hanya demi agar jiwa ini tak lagi diguncangkan. Aku hanya butuh kenyamanan tempat belajar. 

Singkat cerita kini, apa yang aku lakukan, apa yang aku perbuat lebih dari yang diminta telah menyentuh hatinya. Kini mereka berbalik memberi kasih sayang. Bahkan besarnya lebih dari yang aku bayangkan. Lepas dari sebulan neraka, hari-hariku telah berbalik terisi kehangatan, sesuatu yang aku impikan sejak awal. Baru datang setelah sebulan. Meskipun telat, tapi tak mengapa, yang penting kini aku bisa merasakan kenyamanan. 

Hidupku di sini tidak hanya soal belajar, tetapi juga pertemanan. Suatu hal yang aku gugup akan halnya. Seorang diri di lingkungan yang baru. Perlukah aku mencari teman? Ah sudahlah, aku sudah cukup dengan empat teman kesayanganku yang jauh di sana. Meskipun hanya terhubung whatsapp dan google drive, kupikir, cukup sudah.

Bagaimana kabar kalian? Kurindu kebersamaan dan berbincang-bincang lama sampai pagi. Nyatanya, long distance friendship tidak bisa bekerja untukku. Ternyata sulit untuk memperoleh kabar dari mereka atau sekedar mendengarkan cerita aku di sini dengan adanya kesibukan mereka juga masing-masing. Tentu, masih didengarkan, tapi memang, adanya jarak, rasanya jadi berbeda. Aku tidak bisa merasakan kehadiran mereka di sini. Sehingga terus, aku merasakan kesepian.

Asrama jauh di selatan, yang dengan lelet aku berjalan kaki hingga 1 jam untuk sampai ke lab, membuat aku makin terasingkan. Belanja, masak, makan, tidur. Beberapa kali kuajak teman Indiaku yang seasrama joging malam. Menyusuri indahnya kota dalam lukisan hitam malam. Betul, indah hingga kutak ingin memejamkan mata. 

Bukan lagi soal kesepian, kondisi kesehatanku kian memburuk di suatu minggu. Berhari-hari kucoba bertahan, namun tak juga kunjung membaik. Hujan yang terus mengguyur perjalananku rupanya kurang bisa bersahabat. Kuputuskan untuk pindah dari asrama. 

Aku sangat menyukai apartemen baruku. Cukup untuk menghidupkan kembali suasana rumah yang aku rindukan. Di ruangan yang bersofa, selalu kuimajinasikan kehadiran teman-temanku. Tempat di mana aku merasa nyaman. Ternyata, kesendirian dan kesepianku membuat aku larut dalam kesedihan. Menyadari bahwa adanya kebutuhan untuk berinteraksi, berkomunikasi, dan saling mengasihi. 

Padahal, sudah kucoba untuk kuat sendiri, sudah kucoba untuk mandiri. Namun, ketidakmampuanku mengatasi masalah mesin cuci, mengingatkanku pada bapakku. Kumenyadari betapa lemah diriku. Kumerindukan sosoknya, yang selalu ada di setiap aku ada masalah. Ternyata, terdapat hal-hal yang tidak bisa aku lakukan sendiri. Ingin ku meminta bantuan, tapi apa daya, aku belum benar-benar mengenal orang sekitar. 

Aku menyerah, aku katakan pada sahabatku bahwa aku membutuhkan teman di sini yang setidaknya dapat membantuku ketika ku dalam kesusahan dan yang selalu mengingatku di berbagai situasi. Aku berjuang untuk mendapatkannya. Aku ikuti kegiatan mereka. Berharap, aku diterima. 

Saat itu, musim sedang cantik-cantiknya. Inginku menikmati keindahan itu bersama teman-teman. Kucek media, sakit kurasakan. Yang tadinya kuharap bisa menjadi teman, ternyata belum bisa menganggapku teman. Jadilah, kunikmati musim itu sendirian.

Kuceritakan pada sahabatku, bagaimana aku berusaha diterima, dan apa yang aku dapatkan. Dikatakan kepadaku untuk berhenti dan jangan lagi berharap. Sungguh mereka sangat sayang kepadaku, agar aku tidak lagi tersakiti.

Tapi, tak kudengar apa yang mereka katakan. Masih aku berusaha. Mengemis agar diingat. Lagi, sakit yang aku dapatkan. Tak henti-hentinya, kumerajuk kepada sahabatku, betapa gagalnya aku mencari teman. Lagi, mereka nasihatkan untuk berhenti dan meyakinkanku bahwa memang tidak semudah itu mendapatkan teman. Mengingatkanku kembali bagaimana persahabatan lebih dari 7 tahun ini dibangun. Kali ini, kudengarkan, kuhentikan langkahku. Aku katakan kepada-Nya bahwa aku menerima kesepianku jika itu memang takdirku. 

Nyatanya, Dia-lah yang menggerakkan seseorang datang kepadaku. Seseorang yang awalnya tak pernah kutoleh sedikit pun yang malah kunilai tidak baik di depan. Ya, akulah si ISTJ yang hanya menilai dari cover-nya. 

Ada alasan kenapa kucap dia demikian. Kaitannya dengan masa laluku bertemu dengan orang yang salah. Sedikit bercerita, dia adalah sesosok agamis yang perkataannya selalu kudengar. Yang perilakunya dapat meluluhkan kerasnya bapakku. Yang ternyata, di akhir malah menyakitiku, mempermainkanku. Sejak saat itu, aku hindari pribadi-pribadi yang mirip dengannya. Tak mau lagi aku tertipu.

Sosok yang datang kepadaku itu, kukira sama dengan masa laluku. Kukatakan kepadanya bahwa aku tidak mudah percaya dengan orang baru. Kukatakan padanya bahwa aku tidak mudah menganggap seseorang menjadi temanku. Dengan yakin dia katakan bahwa aku bisa percaya dengannya. Kukatakan kepadanya bahwa aku akan mencobanya. 

Suatu hari aku memperoleh kemalangan yang menyebabkan aku harus pergi mengembalikan barang yang rusak. Namun, ketidakpercayaanku terkait bahasa mencoba mengajaknya pergi menemaniku. Aku lontarkan keinginanku padanya yang pada saat itu ada orang lain di sekitar. "Tidak", jawabnya. Rasanya, air mata yang mendesak keluar saat itu sudah cukup menggambarkan kekecewaanku. Kupikir dia adalah jawaban dari kesepianku. Nyatanya memang benar kutak bisa mudah memberikan kepercayaanku.

Aku berlanjut pergi sambil menyeka air mata. Kuyakinkan diriku bahwa aku sendiri pun mampu mengatasinya. Dengan langkah gugup, kusampaikan keinginanku dengan terbata-bata yang untungnya mereka memahami kondisiku dan aku bisa pulang dengan lega. 

Penolakan yang lagi-lagi menambah luka, tidak mudah aku lupakan. Kemudian di saat aku belum melupakannya, sosok itu datang kembali. Kukatakan padanya bahwa aku kehilangan kepercayaanku padanya. Dia tidak mundur, malah menjanjikan untuk tidak lagi mengulanginya yang kemudian aku terbujuk untuk menyetujuinya. Kembali, aku katakan padanya bahwa aku akan "mencoba" mempercayainya. Yang hingga entah kapan aku baru bisa benar-benar menganggapnya temanku. 

Bagiku, aku lebih mementingkan temanku mau apa dan bagaimana, dan aku tidak pernah memikirkan orang lain melihat aku dengan temanku seperti apa. Penolakannya terhadap ajakanku, katanya karena dia takut orang lain melihat bagaimana, di situlah alasan aku kesulitan mempercayainya sebagai seseorang yang bisa aku anggap teman, karena temanku seharusnya tidak perlu mendengar apa yang orang lain katakan, tetapi haruslah mengenai aku maunya bagaimana. Seperti dia itu sebenarnya teman mereka, atau teman aku. Jika teman aku, maka aku lah yang harusnya dipedulikan, bukan mereka. 

Setiap kali aku mengungkitnya, dia selalu memintaku untuk menghentikannya. Berkali-kali dia menyesal dan tidak akan melakukannya lagi. Satu per satu, kulihat dia patuh pada janjinya yang membuat aku mulai mempercayainya. 

Kabar baik ini tentu tidak aku lewatkan kepada empat orang sahabatku. Mereka turut berbahagia dengan adanya kehadiran teman baruku dan berharap aku tidak lagi bersedih dalam kesepian. 

Mulai saat itu, duniaku hanya tentang kewajiban, aku, dan dia. Hanya dengan bersamanya aku sudah merasa tenteram. Ketika aku butuh bercerita, kupanggil dirinya dan dengan sigap dia datang dengan senyuman disertai vitamin C dan makanan ringan kesukaanku. Ketika dia bersedih, ku segera datang menjenguknya dan menghiburnya. Kujanjikan untuk selalu ada untuknya. 

Sungguh, aku menikmati pertemanan ini. Tidak ada masa paling indah di sini selain masa-masa yang kuhabiskan bersamanya. 

Sayangnya, kebahagiaan ini hanya berlangsung enam bulan. Ada masanya, dia harus berpindah sehingga tidak bisa lagi menemani kesepianku. Murung aku dibuatnya. Jiwa kebungsuanku tak bisa dibendung. Iya, aku cengeng. Hari demi hari mendekati perpindahannya, banjir air mata tak bisa ditahankan. Betapa tidak, bayang-bayang kesepian mencekam, imajinasi ketakutanku akan ingatan masa-masa sulitku, rasanya tak mampu aku hadapi sendiri. Kehadirannya adalah anugerah yang tak terkira bagiku sehingga seluruh ketakutan dan kekhawatiran tidak pernah aku pedulikan. Namun, tanpanya, hampa yang aku rasakan.

Menjerit aku sedalam-dalamnya. Sesedih itu aku ditinggalnya. Akankah kita akan bertemu kembali? Bayang-bayang pertemuan terakhir selama-lamanya selalu menghantui. Jujur, dia adalah satu-satunya yang kukatakan kepada diriku bahwa sepertinya dia adalah jawaban kesunyianku. Di saat aku menemukannya, aku harus merelakan jalan hidupnya.

Kita berbeda, dia memilih jalan yang berbeda. Sebagai temannya, aku yakin dia akan sukses di jalan yang dia pilih itu. Aku pun memiliki jalanku sendiri, yang aku yakin bahwa inilah jalan yang terbaik untukku. 

Lalu apa yang aku harus lakukan? Rasanya tidak baik larut dalam kesedihan perpisahan. Tuhan yang menghendaki pertemuan, Tuhan jugalah yang menghendaki perpisahan. Sebagaimana aku percaya bahwa ada selalu hikmah di baliknya. Aku percaya, Tuhan telah menyiapkan cerita yang baru untukku dan untuknya. Jadi, yang harus aku lakukan saat ini adalah merelakannya di jalannya dan mengikhlaskan perpisahan ini. Persahabatan tidak harus selalu ada di sisi, dia harus tau bahwa di mana pun aku berada, aku akan selalu mengingatnya dan selalu mendukung yang terbaik untuknya.

Aku berterima kasih kepada Tuhan, telah mempertemukan aku dengannya. Sungguh aku memuji-Nya, sebagaimana aku menyaksikan sendiri bagaimana dia memiliki sosok pribadi yang tulus, penyabar, dan pengertian. Sosok yang sebaik-baiknya manusia. Sosok yang selama ini aku cari. Sungguh salah penilaianku di depan yang akhirnya kini aku belajar, untuk tidak lagi menilai seseorang begitu mudah di depan. Ya Tuhanku, dia adalah sosok yang tampan hatinya. Lindungilah ia selalu, berilah kebahagiaan yang melimpah, serta jauhkanlah dari kesedihan. 

Sesungguhnya, penilaian yang salah ini adalah yang kedua kalinya. Ingat dengan masa laluku? Dulu aku juga salah menilai. Yang kukira baik hatinya, ternyata malah "busuk" sejahat-jahatnya. Mungkin inilah jalan Tuhan untuk mengajarkan kepadaku untuk tidak lagi menilai seseorang dari depannya saja. 

Untuk sisa enam bulan ke depan. Kutau ini akan sulit, tetapi aku harus kuat dan percaya dengan diriku sendiri bahwa aku mampu melewatinya meskipun dalam kesendirian. Bersabarlah, sedikit lagi aku akan pulang.

The Problem of Animal Studies in Drug Discovery

[Picture Source: SciTech Europa]

Drug discovery is exhausting as it is long, expensive, and risky, but still, it doesn't guarantee whether the discovery is a success or not. From 798 drugs investigated between 1991 and 2015 at 36 academic institutions in the United States, the success rates were 75% at phase I, 50% at phase II, 59% at phase III, and 88% at the new drug application (Takebe, Imai, & Ono, 2018). These numbers clearly show that some discoveries end up with failure. Even more pathetic, this paper also observed a very low success rate in the drug discoveries of the disease in the nervous system. The success rates were 5% at phase I, 4% at phase II, and 3% at phase III. In agreement, Kaitin & Milne (2011) also found that the success rate for neuropsychiatric drug candidates was dramatically lower than 8.2% so we may say that fro these discoveries, mostly they have invested so many times and costs, yet ending up with failures still cannot be denied. Of course, we don't want to waste times and more money, so this problem should be resolved for a better future of drug discoveries. 

One of the reasons why the success rate is low for some cases of drug discoveries is the uncertainty in the translation of preclinical experiments to clinical trials. The uncertainty in the translation means the results from animal studies cannot surely represent what will also happen in human studies. Collins, the director of NIH (National Institutes of Health) gave a warning that 80%-85% of drugs effective in mice are ineffective in humans (Collins, 2013). More real examples, thalidomide is not a teratogen in many animal species, but teratogen in humans (Lepper, Smith, Cox, Scripture, & Figg, 2006) and the monoclonal antibody TGN412 is fine during preclinical studies but life-threatening morbidity during the clinical trials in all six healthy volunteers (Attarwala, 2010). That's why some researchers are questioning the relevancy of animal studies to human studies.

There might be some reasons why the relevancy is low. A paper mentioned that it happened because of the lack of robustness from animal to human studies (Lowenstein & Castro, 2009). Robustness is the ability to withstand various conditions or rigorous testing. How come it will have good robustness when usually the animal studies are conducted in a very narrow set of experimental conditions? Meanwhile, in the context of human, humans are varied by age, genetic, geographic, and so on. Thus, the animal studies should be performed in wider set of experimental conditions in order to mimic the real conditions in human. 

For more details why do we need wider set experimental conditions of animal studies is because of the animals being studied themselves are varied in the term of species and strains that with this, firstly, the animals have a variety of metabolic pathways and drug metabolites, leading to variation in efficacy and toxicity. Secondly, there are variations in the drug dosing schedules and regimens in the animal studies that make the adjustment to the human become more complicated. Thirdly, the animal studies are varied in the case of methods of randomization, choice of comparison therapy (none, placebo, vehicle), and the number of experimental groups that are usually small, so it makes the statistical power becomes inadequate (Pound, Ebrahim, Sanderdock, Bracken, & Roberts, 2004).

As a matter of fact, the failure of the translation is not only occurred when the experiments are poorly designed, conducted, and analyzed as already mentioned earlier, but also due to limited animal models that can fully mimic the disease, even there are some diseases without available animal models at all. As an example, King (2018) mentioned that no animal model for Alzheimer's disease was available. This is because no organisms have the same complexity with human brain as human brain is the most complex brain among all organisms. This may also the reason why the success rate of the drug discovery for neural diseases is very low since it also correlates with human brain that the translation from animal models for Alzheimer's disease. 

In another side, some researchers have moved away studying human diseases from animal study. They refocus and adapt new methodologies to understand biology in humans. The alternatives they are studying are in-vitro testing, computer (in silico) modeling, research with human volunteers, and so on. For the case of in-vitro testing. Harvard's Wyss Institute has created a tool named "organs-on-chips" that as its name, the human cells are grown in a state-of-the-art system on a chip to mimic the structure and functions of human organs and organ system so the chip can be used for studying the disease, drug testing, and toxicity rather than using the animals. Organs on a chip is based on microfluidic technology that has rapidly develope as a powerful tool for numerous applications that one of the applications is for this case. The microfluicdic technology provides articficial testing subject that can resembles the human body in every aspect so this tool has enormous potential to accommodate cells/tissues to create a physiologically relevant environment that animal studies may not able to afford (Sosa-Hernandez et al., 2018).

Computer (in silico) modeling, another alternative besides in-vitro testing, allows researcher to study the human biology and the progression of developing diseases without harming the animals through a sophisticated model computer. For example, Quantitative structure-activity relationships (QSAR) that has been developed with an estimation that can accurately predict the ways the new drugs will react in the human body. It was Veith who was pioneering the development of QSAR that through the International QSAR Foundation, he organized some experts with the same value to develop non-animal testing methods (Sullivan, Manupello, & Willet, 2014).

Meanwhile, research with human volunteers, another choice for the alternative, introduced a method called "microdosing" that provides vital information before applying it to the large-scale human trials so with the help from imaging techniques a very small doses of a drug given to the volunteers can be monitored so the way how the drug behaves can be seen in the body. The use of microdose might have prevented the tragedy with TFN1412 mentioned earlier that was life-threatening for the subjects because the microdose study with TGN1412 by systemic dermal application could have determined the amount of antibody without risk to the subjects and even can provide pharmacokinetic and metabolic data relevant to the human species (Langley & Farnaud, 2010).

In summary, as we don't want to waste times and more money on a drug discovery that the success rate is very low, at least there are two choices: to develop wider set of experimental conditions in animal studies or to select the alternative methods without animal testing (in-vitro testing, computer (in silico modeling), and research with human volunteers (microdosing). Whatever it is, of course, we hope a better future for the drug discovery.

(Disclaimer: this is my essay submitted for my master course assignment)



References:

Attarwala, H. (2010). TGN1412: From discovery to disaster. J Young Pharm, 2(3), 332-336.

Collins, F. (2013). Of mice, men and medicine. [http://directorsblog.nih.gov/of-mice-men-and-medicine/comment-page-1/#comment-4902].

Kaitin, K. I., & Milne, C. P. (2011). A dearth of new meds. Sci Am, 305, 16.

King, A. (2018). The search for better animal models of Alzheimer’s disease. Nature (London), 559, S13-S15.

Langley, G., & Farnaud, S. (2010). Microdosing: safer clinical trials and fewer animal tests. Bioanalysis, 2(3), 393-395.

Lepper, E. R., Smith N.F., Cox, M. C., Scripture, C. D., & Figg, W. D. (2006). Thalidomide metabolism and hydrolysis: mechanisms and implications. Curr Drug Metabol, 7, 677–685.

Lowenstein, P. R., Castro M. G. (2009). Uncertainty in the translation of preclinical experiments to clinical trials. Why do most phase III clinical trials fail?. Curr Gene Ther, 9(5), 368–374.

Pound, P., Ebrahim, S., Sandercock, P., Bracken, M. B., & Roberts, I. (2004). Where is the evidence that animal research benefits humans? BMJ, 328, 514–517.

Sosa-Hernández, J. E., Villalba-Rodríguez, A. M., Romero-Castillo, K. D., Aguilar-Aguila-Isaías, M. A., García-Reyes, I. E., Hernández-Antonio, A., & … Iqbal, H. (2018). Organs-on-a-chip module: a review from the development and applications perspective. Micromachines, 9(10), 536.

Sullivan, K. M., Manuppelo, J. R., & Willett, C. E. (2014). Building on a solid foundation: SAR and QSAR as a fundamental strategy to reduce animal testing. SAR and QSAR Environmental Research, 1-9.

Takebe, T., Imai, R., & Ono, S. (2018). The Current Status of Drug Discovery and Development as Originated in United States Academia: The Influence of Industrial and Academic Collaboration on Drug Discovery and Development. Clin Transl Sci, 6, 597–606.

Sunday, September 29, 2019

The Disagreement of PGS Application

[Picture Source: Fertility Associates]

Women after the age of 35 years oftentimes have a gradual decline in fertility (Maheshwari, Hamilton, & Bhattacharya, 2008). A study in 2012 found that the chromosomal abnormality as one of the causes of the miscarriage experience by the aged women (Khandekar, Dive, & Munde, 2016). A procedure in which the genes of embryos created through in vitro fertilization (IVF) are examined for a number of potential genetic disorders before being transferred into a uterus, preimplementation genetic screening (PGS), has been proposed since the early 1990s to improve IVF result (Sermon et al., 2016).

Recently, PGS is such a promising procedure for the aged women to prevent the miscarriage due to chromosomal abnormalities especially aneuploidy, Human embryos are normally euploid which the egg contributes 23 chromosomes and the sperm contributes another 23, so in total 46 chromosomes (Khandekar et al., 2016). While aneuploid embryos contain one more or less than the number of the normal chromosomes which are more likely to fail to implant or end in the miscarriage. This procedure is such good news for the aged women with infertility and the recurrent pregnancy loss. 

In Japan, Japan Society of Obstetrics and Gynecology (JSOG) has made the decision to embark on the clinical research on PGS. The clinical research will investigate how PGS improves the pregnancy and miscarriage rates among women between the ages of 35 and 42 who experience infertility or an inability to give birth (Mainichi Japan, 2017). From 503 women aged 35 to 79 who underwent health checkups in the study conducted in Okazaki, Aichi Prefecture, during a one-year period from February 2007, 458 had experienced pregnancy, of whom 190 or 41.5 percent had suffered the miscarriage (Japan Times, 2009). That's why, with unexpectedly high miscarriage rate, JSOG finally decided to start the clinical research on PGS.

Nevertheless, the decision of JSOG was criticized as being too hasty. PGS is still debatable due to its ethical view and social aspect. Therefore, in my humble opinion, I can not agree with the application of PGS to prevent miscarriage due to some reasons.

Firstly, indirectly PGS deny the existence of the people with disabilities because by applying the PGS before performing IVF, the abnormal embryos can be found and can be decided not to be selected. Indirectly it also puts discrimination toward disable people. Even though, by if the result finds that the embryo is aneuploid (abnormal) and the mother still wants to transfer it to her uterus, the embryo will grow as a disabled person. This condition is also such a dilemma when the mother has already known about the disability but she still wants to transfer it and if her child knows about it, her child may live with regret and hatred. 

Secondly, in the future, it is possible for human with normal embryos to apply PGS to select desired gender of the embryo (to select between girl or boy) since PGS uses screening panels that also contain probes for sex chromosomes, a side effect of this technology, it provides IVF patients with information about the sex of their embryos prior to transfer (Dondorp et al., 2013). If most of the people conduct this procedure, then it will damage the diversity of the people in the world. How if most of the people in the world in the future are women? Then, some of the women will find her life partner difficultly. Then, only a few couples can do reproduction. In the end, the regeneration will also become extremely difficult. No future generation means no life which will be the end of the world.

Thirdly, PGS costs a lot, the IVF/PGS strategy was 100 times more expensive rather than pregnancy management, costing $45,300 per live birth compared with $418 (Murugappan, Ohno, & Lathi, 2015). Therefore, economically, only people with a high income can conduct this procedure which is injustice with the people from the low income. In this case, about the rate of the success of the application of PGS is also still in the investigation which means the procedure may also give a failure. So after performing all the steps, it is still possible to just waste all the money without any good results due to its failure.

Lastly, the cause of the miscarriage is not only because of the abnormal chromosomes, there are still numerous causes, for example, infection, medical conditions in the mother (such as diabetes or thyroid disease), hormone problems, immune system responses, physical problems in the mother, or uterine abnormalities (Adolfsson, 2006). So, I believe, there is still numerous way to prevent the miscarriage rather than applying PGS.

In conclusion, based on my review on its denial disability, the possibility of diversity damage, high cost, and the existence of another way to solve the miscarriage problems, I still in my standpoint that I can not agree with the application of PGS. 



References:

Adolfsson, A. (2006). Miscarriage: Women's Experience and its Cumulative Incidence.

Dondorp, W., De Wert, G., Pennings, G., Shenfield, F., Devroey, P., Tarlatzis, B., … Diedrich, K.
(2013). ESHRE Task Force on ethics and Law 20: Sex selection for non-medical reasons.
Human Reproduction, 28(6), 1448–1454. https://doi.org/10.1093/humrep/det109

Japan Times. 2009. https://www.japantimes.co.jp/news/2009/08/03/national/miscarriagerate-
found-unexpectedly-high/#.WyLdwqczY2w, accessed on June 2018.

Khandekar, S., Dive, A., & Munde, P. (2016). Chromosomal abnormalities -A review
Chromosomal abnormalities - A review, (January 2012).

Maheshwari, A., Hamilton, M., & Bhattacharya, S. (2008). Effect of female age on the
diagnostic categories of infertility. Human Reproduction, 23(3), 538–542.
https://doi.org/10.1093/humrep/dem431

Mainichi Japan. 2017. http://mainichi.jp/english/articles/20170214/p2a/00m/0na/013000c,
accessed on June 2015.

Murugappan, G., Ohno, M. S., & Lathi, R. B. (2015). Cost-effectiveness analysis of
preimplantation genetic screening and in vitro fertilization versus expectant management
in patients with unexplained recurrent pregnancy loss. Fertility and Sterility, 103(5),
1215–1220. https://doi.org/10.1016/j.fertnstert.2015.02.012

Sermon, K., Capalbo, A., Cohen, J., Coonen, E., DeRycke, M., DeVos, A., … Geraedts, J. (2016).
The why, the how and the when of PGS 2.0: Current practices and expert opinions of
fertility specialists, molecular biologists, and embryologists. Molecular Human
Reproduction, 22(8), 545–557. https://doi.org/10.1093/molehr/gaw034


(DISCLAIMER)
This writing is my essay submitted for my master course assignment.

Sunday, September 08, 2019

M(alpha)NP Acid: An Alternative To Separate Alcohol Enantiomers

How do you usually handle alcohol racemic? Do you separate the enantiomers? How to do it? Column Chromatograph? 

Sometimes, using column chromatograph equipped with a chiral column can be helpful in separating the enantiomers. However, sometimes it doesn't work. Introducing M(alpha)NP Acid is one of the alternatives to separate the alcohol enantiomers. This method was developed by Kasai et al (2004). This powerful chiral molecular tool is able to determine their absolute configurations in an unambiguous way through 1H NMR anisotropy Method.  


How to introduce the M(alpha)NP Acid into the molecule? Here is the way:

The racemic of alcohol compound is added with 1,4-dimethylaminopyridine (DMAP), 10-camphorsulfonic acid (CSA), and 1,3-dicyclohexylcarbodiimide (DCC), then dissolved them with dichloromethane (DCM). Stir them at room temperature overnight. After working up the reaction solution, try to purify with column chromatograph, then measure the 1HNMR of first and second eluted sample because we need the chemical shift data from both to do the calculation through 1HNMR anisotrophy method. 

To know whether the 1st eluted sample is  S or R configuration, firstly, assign the proton from the NMR spectrum. Put the chemical shift data like the picture below. Left side for the 1st eluted sample and the right side for the 2nd eluted sample. Then, subtract the value of chemical shift data of 2nd eluted sample with 1st eluted sample. Then put the result on each proton location in the structure and always arrange it based on the sector rule. 


The M(alpha)NP Acid with thick black arrow, H proton with a dashed arrow, and left side for the proton which the result of the subtraction less than 0 (negative), and right side for proton which the result of the subtratction more than 0 (positive). By arranging like that, now we can see the configuration of the 1st eluted sample. The direction is counterclockwise, so the 1st eluted sample is S-configuration. This determination also means that the 2nd sample is in the opposite configuration which is R-configuration.


All the data and explanation is referred to this reference:
Kasai, Y., Ji, H. T. A., Fujita, T., Yamamoto, Y., Akagi, M., Sugio, A., … Harada, N. (2004). M A NP Acid , a Powerful Chiral Molecular Tool for Preparation of Enantiopure Alcohols by Resolution and Determination of Their Absolute Configurations by the 1 H NMR Anisotropy Method, 585(10045022), 569–585. https://doi.org/10.1002/chir.20077

XtalFluor-E: Selective Fluorination Reagent


XtalFluor-E (diethylamino difluorosulfunium tetrafluoroborate) appears as one of deoxyfluorinating reagents that improve the weakness of DAST. Different from DAST which is liquid reagents, XtalFluor-E is a solid reagent so it's more stable. 

The mechanism of deoxyfluorination with XtalFluor-E is similar to DAST. The reaction also involves the dialkylaminodifluorosulfane intermediate. However, the difference is, when using XtalFluor-E, it release tetrafluoroboric acid and the reaction also fluoride starved so the side reactions often occur such as the formation of ether compound. For example, see the scheme below. 


Therefore, the reaction with XtalFluor-E usually involves additive such as Et3N.3HF (triethylamine trihydrofluoride) as the source of exogenous fluoride (see the table below). However, the order of the addition of Et3N.3HF should be noted. The yield will be better if the addition of this additive is done with the reagent (XtalFluor-E) before the addition of the substrate. If it is done after the addition of substrate and reagent, then the yield will not be improved because the deoxyfluorination has occurred instantaneously already. That's why the addition of Et3N.3HF after that will be less meaning.   


The addition of strong base might be improving the yield as it will work for the deprotonation. The work from previous table shown also explained that the addition of DBU as non-nucleophile strong base improved the yield of the reaction and reducing the side reactions. Although the yield was improved, the reaction rates were slower than when using Et3N.3HF.

All the data and explanation is refered to this reference:
Heureux, A. L., Beaulieu, F., Bennett, C., Bill, D. R., Clayton, S., Mirmehrabi, M., … Couturier, M. (2010). Aminodifluorosulfinium Salts : Selective Fluorination Reagents with Enhanced Thermal Stability and Ease of Handling †,‡, 3401–3411. https://doi.org/10.1021/jo100504x

DAST: The First Deoxyfluorination Reagent


Reported by a chemist at Dupont in 1975, DAST (Dietylaminosulfur trifluoride) became a stable to gaseous SF4 (Wen-Li Hua, Xiang-Go Hu, & Hunter, 2017) . This gaseous reagent, SF4, is extremely toxic and corrosive. Hence, DAST appeared as an alternative in liquid form. The excellence of DAST than SF4, DAST is easier to be handled as it doesn't require much higher temperatures.

Nevertheless, it was soon found that DAST also has some weaknesses. If it undergoes heating, it can decompose and produce SF4 as we already knew that this substance is toxic and corrosive. If it undergoes further heating, it can explode into undefined gases and black char (Heureux, et al., 2010). 

Then, Deoxofluor was developed. From differential scanning calorimetry (DSC), Deoxofluor has the same decomposition temperature with DAST, yet it degrades slower so it is considered safe.

Do you know? Soon after DAST and Deoxofluor conducted in larger scale, it is found to be unsafe. The preparation process was problematic. First, the purification of the crude using vacuum distillation is dangerous as they are explosive. Secondly, after the manufacturing, the shipping regulation is very strict. Thirdly, these reagent is also not stable in color. Fourthly, during the use, both may generate free HF which is very volatile, highly toxic, extremely corrosive to the skin and other tissues including bones (Heureux, et al., 2010).

Nonetheless,  DAST remains the most popular deoxyfluorination reagent because of its availability and general scope (Nielsen, Ugaz, Li & Doyle, 2015). Deoxyfluorination is a reaction of introducing fluorine atom into a molecule through the substitution of alcohol functional group. The reaction with DAST proceeds with inversion. It goes with SN2 reaction as the alcohol functional group is a poor leaving group, the alcohol then is converted into weaker base by being attached with the electrophilic sulfur atom. Then, the nucleophile, the fluorine atom with negative charge, attacks from the backside of the carbon atom which is the electrophile. It attacks from the backside since the leaving group which is attached with the electrophile blocks the approach of the nucleophile from the frontside. That's why it simply goes with inversion through SN2 reaction.


In deoxyfluorination, DAST also has limitation. It may produce side products. If the substrate has double bond, it may undergo elimination. And if the substrate has carbonyl group, it may be difluorinated. Therefore, several new reagents has been developed to improve the selectivity.  


Reference:
Heureux, A. L., Beaulieu, F., Bennett, C., Bill, D. R., Clayton, S., Mirmehrabi, M., … Couturier, M. (2010). Aminodifluorosulfinium Salts : Selective Fluorination Reagents with Enhanced Thermal Stability and Ease of Handling †,‡, 3401–3411. https://doi.org/10.1021/jo100504x
Nielsen, M. K., Ugaz, C. R., Li, W., & Doyle, A. G. (2015). PyFluor: A Low-Cost, Stable, and Selective Deoxy fl uorination Reagent, 9571–9574. https://doi.org/10.1021/jacs.5b06307
Wen-Li Hua, Xiang-Guo Hu, L. H. (2017). Recent Developments in the Deoxyfluorination of Alcohols and Phenols : New Reagents , Mechanistic Insights , and Applications, 4917–4930. https://doi.org/10.1055/s-0036-1590881

Friday, September 06, 2019

A Prospective Fluorinated Drugs

[Picture Source: ThoughtCo]


Twenty percents of marketed drugs are fluorinated because fluorine atom can completely change the biological properties, for example, 5-Fluorouracil. Before being introduced by the fluorine atom, the uracil is transformed into DNA by Thymidylate synthase that is not desired in cancer case. By introducing the fluorine atom, the uracil now acts as antimetabolite that inhibits the thymidylate synthase so indirectly inhibit the carcinogenesis also. That's how fluorine atom can completely change the biological properties of natural uracil (Berger, Pittman, & Wyatt, 2009).


Another example is Fludcortisone. Cortisone itself is a steroid that prevents the release of a substance that causes inflammation in the body so it possesses glucocorticoid activity. After being introduced with fluorine atom, the activity exceeded by factor 10 than the parent hormones (cortisone), therefore it possess a remarkable glucocorticoid activity. 

So, how come fluorine atom can completely change biological properties of a compound? What kind of atom is it? 

Fluorine atom as expected in the periodic table of elements possesses ultimate electronegativity and oxidation potential. Talking about the amount, fluorine atom is available abundantly even more significant than other halogens on Earth's crust as it is the 13th most common element on Earth's crust. Compare to other halogens, Fluorine atom also has extraordinary high hydration energy so therefore it behaves as a very poor nucleophile in aqueous solution. Another feature of fluorine atom that makes it different from others is the C-F bond, it is one of the strongest chemical bonds as its biological formation/cleavage will be quiet difficult to generate under normal condition. 

Fluorine atom can give effect to organic compound properties not only due to its electronegativity, but also other properties it possesses such as lipophilicity, size, and electrostatic interaction. Those properties can dramatically influence the chemical reaction. Do you know, even a single fluorine atom is able to change a biological property of a natural product. 

Last but not least, after the fluorination, the fluorine atom can change the acidity or basicity of a parent compound so this can strongly influence binding affinity pharmacokinetic properties and bioavailability of a drug candidate. 

As a powerful functional group, the number fluorinated drugs is expected to increase in the future. How come? Atorvastatin Lipitor became the most profitable drug until 2011. Another example, Fluticasone propionate, the annual sales became more than 5 billion dollars.

You can read all the development of fluorinated drugs from a paper written by Wang et al (2013).

That's all the post I wrote. Thank you for visiting. I apologize if there is a mistake. 

Reference:
Berger, S. H., Pittman, D. L., & Wyatt, M. D. (2009). chemotherapy, 76(6), 697–706. https://doi.org/10.1016/j.bcp.2008.05.019.Uracil
Wang, J., Sánchez-Roselló, M., Aceña, J. L., Del Pozo, C., Sorochinsky, A. E., Fustero, S., … Liu, H. (2014). Fluorine in pharmaceutical industry: Fluorine-containing drugs introduced to the market in the last decade (2001-2011). Chemical Reviews, 114(4), 2432–2506. https://doi.org/10.1021/cr4002879