Drug discovery and testing

Newly developed drugs have to be proved as efficient and safe before marketing. For this purposes, adsorption, distribution, metabolism and toxicology screening of the drugs are performed on in vitro models before1. Drug toxicity is mostly performed through primary hepatocytes in preclinical drug testing. However the process is not perfect, due to complications and unforeseen toxicity, some drugs have to be withdrawn from the market. As indicated by a recent study, about 19% of the drugs that failed in Phase II clinical trials and 21% of the drugs that failed in Phase III clinical trials1.

Recently it is discovered that Phase I and Phase II drug metabolizing enzyme activities in hepatocytes can be sustained for weeks when cultured in microgravity simulating devices such as rotating wall vessels, clinostats and random positioning machines1. Moreover, it was also shown that hepatocytes cultured in 3D culture in microgravity are capable of producing albumin, storing glycogen and forming bile canaliculi between hepatocytes with complicated tubular branches like in human body2. Since they also express elevated levels of mature hepatocyte genetic markers in function wise, they are considered as excellent candidates for preclinical drug testing3.

A recent research performed by Nislow et al, sent genetically engineered yeast to space with STS-135 program. The results revealed a unique chemogenomic pattern of yeast cells caused by the reduced convection of oxygen and carbondioxide. Thus, this altered pattern of mitochondrial and ribosomal respiratory function can allow analysis of drug pathways, which are not possible to obtain on Earth4.

All in all, microgravity offers a unique platform for drug discovery and testing due to the fact that in microgravity hepatocytes can sustain Phase I and Phase II drug metabolizing enzyme activities for a long time. Moreover, the altered redox potential with changes in reactive oxygen species that occur in microgravity is not achievable on Earth, therefore microgravity offer a new perspective to drug pathway analysis.


1. Hammond, T., Allen, P., & Birdsall, H. (2016) Is There a Space-Based Technology Solution to Problems with Preclinical Drug Toxicity Testing? Pharmaceutical research, 1-7.
2. Ishikawa M, Sekine K, Okamura A, Zheng YW, Ueno Y, Koike N, et al. (2011) Reconstitution of hepatic tissue architectures from fetal liver cells obtained from a three-dimensional culture with a rotating wall vessel bioreactor. J Biosci Bioeng. 2011;111(6):711–8.
3. Fey SJ, Wrzesinski K. (2012) Determination of drug toxicity using 3D spheroids constructed from an immortal human hepatocyte cell line. Toxicol Sci. 2012;127(2):403–11.
4. Nislow C, Lee AY, Allen PL, Giaever G, Smith A, Gebbia M, et al. (2015) Genes required for survival in microgravity revealed by genome- wide yeast deletion collections cultured during spaceflight. Biomed Res Int. 2015;2015:976458.