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Researchers are on the verge of unleashing the power of the element boron in a new generation of drugs and therapies as decades of research begins to bear fruit. To date, boron has been one of biology’s best-kept secrets, but it is now attracting growing research interest and investment from the pharmaceutical industry in the quest for novel drugs to tackle cancer and infectious diseases, potentially overcoming limitations and side effects of current products.
Europe’s response to the challenges and opportunities of boron chemistry in medicine was discussed at a recent workshop, Biobor-Exploring New Opportunities Of Boron Chemistry Towards Medicine. According to the event’s moderator, Zbigniew Lesnikowski, the European Science Foundation (ESF) workshop set the stage for a new era of boron therapies going beyond the current application in cancer radiotherapy via boron neutron capture therapy (BNCT), in which the element is used to help translate beams of neutrons into radiation that targets tumor cells with less “collateral damage” of surrounding healthy tissue.
“It became obvious during the workshop that there is now sufficient knowledge and enough compounds to support a broad program of screening in the quest for new antiviral and anticancer drugs containing essential boron components,” said Lesnikowski. There was also scope for improving the application of BNCT to cancer. In addition to these two therapeutic avenues, boron also has potential as the basis for compounds in diagnosis and biosensing, as well as for novel bioorganic materials.
Chemical BenefitsThe applications in biosensing, biomaterials and drug development all spring from the fundamental chemical properties of boron. All life is derived ultimately from the element carbon, which lies next to boron in the periodic table of elements, their respective atomic numbers being six and five. Boron compounds share some similarities with carbon but also have important differences. It is the combination of these similarities and differences that gives boron its unique potential in medicine.
The important similarity is that boron, like carbon, combines with hydrogen to form stable compounds that can participate in biochemical reactions and syntheses. The key difference is that these compounds have distinctive geometrical shapes and electronic charge distributions with greater 3-D complexity than their carbon-based equivalents.
As Lesnikowski put it, while organic carbon molecules tend to comprise rings and chains, boron hydrides (compounds comprising mostly boron and hydrogen) are made up of clusters and cages. This 3-D structure makes it possible to design molecules with specific charge distributions by varying their internal structure, which in turn brings the potential to tune how each part of the structure relates to water molecules and biomolecules present in living organisms. If a component is hydrophobic, meaning it repels water, it is well-placed to enter cells by crossing the membrane. If it is hydrophilic, meaning water-loving, it will naturally be soluble in water. The hydrophobic/hydrophilic interactions also affect how a molecule makes contact and communication with target proteins and nucleic acids.
Future PotentialThe fact that novel boron compounds will be unfamiliar to life has potential advantages for antibiotic drugs, since pathogens will be less able to develop resistance against them. “Also, the kind of interactions would be somehow different from the key-lock systems built up in living cell lines in nature for billions of years,” said Lesnikowski. “We can thus anticipate that active substances would be less prone to the development of resistance. This is an obvious advantage of boron drugs.”
While pathogens such as bacteria and viruses are capable of evolving resistance against almost any molecule that attacks them, Lesnikowski believes that it would take longer for this to happen in the case of boron-based compounds. This would therefore make it easier for humans to remain one step ahead rather than struggling to keep pace.
Apart from a lack of knowledge over boron’s potential, the development of boron compounds for medicine has been held back until now by the high cost of the catalysts and boron-based intermediate compounds used in the synthesis. Another important recent development was therefore the availability of lower-cost intermediates in the synthesis processes, according to Lesnikowski.
For more information, visit www.esf.org.