The yew is an evergreen tree with wood that is very hard, dense and flexible and has been used throughout history to make bows. There are seven closely related species with hybrids common and all have flat needles and fleshy berries, which are usually red although yellow in some varieties. Slow to grow, European yews over 2000 years old still exist. Of all the yews, the Pacific yew is significant because it contains the highest ‘taxol’ content. It originates from the past great moist temperate Pacific rainforests of North-West America and is mainly to be found only in parts of Montana and Idaho where it is considered a weed. It grows only in sporadic isolated clumps in ancient woodland, on average, perhaps one per acre.

Throughout history, the European yew has been used as a poison. All parts of the tree except the flesh of the fruit, contain the poisonous alkaloid taxin. There is even a fungus that grows on yew bark that contains this poison. It is named as an ingredient of the witches’ brew in Macbeth and as early as the 2nd century BC, was noted by Nicander, a Greek poet who warned others as to its fatal effects. In Greek mythology, the yew is sacred to Hecate, goddess of the waning moon, who ruled over the land of the dead. Symbolically then, it is associated with death and is commonly found planted in graveyards. Medicinally, it has also found use. The Native Americans used it to treat amongst other maladies; TB and kidney disease and Chinese healers used it to treat arthritis.

In 1962, random samples of the Pacific yew were collected. Tests showed that extracts from the inner bark appeared to slow the growth of cancerous cells fairly dramatically. Further tests by chemists Monroe Wall at the Research Triangle Institute uncovered positive action against mouse leukaemia. In 1967, the active compound was finally isolated and it was named ‘taxol’ after the tree’s genus ‘taxus’. In 1977, scientists at the Albert Einstein College of Medicine in the Bronx carried out yet further tests. They found that the division of cancer cells was inhibited by taxol, which appeared to glue the structures that formed the framework of the cells, disallowing their rearrangement into new configurations. And then the cells died…. As an anti-cancer possibility it shone. More successful tests took place, using mice with transplanted human cancers. There were two great problems however.

The first was supply. Yew bark was scarce and stripping the bark killed the tree. Unrestricted felling was already taking place and fears were that the species could be wiped out. Artificial synthesis was also proving too complex. The second problem was that it was not soluble in water and so difficult to administer. Scientists chose to combine it with a mixture of alcohol, castor oil and a saline solution, a combination known as a ‘cremophore’. First experiments were carried out in 1982 on no-hope cases for whom all other treatments had failed but they turned out disastrously. Two died and the others became very sick. Possibly, even probably, the cause may have been the cremaphore. Either way, these trials were halted. The remaining trials threw up several side effects such as nausea, aching muscles, fever, loss of feeling in extremities (or tingling), and more seriously, suppression of blood cell production by bone marrow. Conclusions reached were that taxol did no serious harm but neither were wonderful improvements remarked.

In 1985, an ovarian cancer sufferer given just weeks to live and wanting to try taxol, approached William McGuire of the John Hopkins University’s medical centre. She was granted the chance and the results were unexpectedly successful. As a result, McGuire instigated more research with other ovarian cancer patients. Again, the results were remarkable. In August of 1989, these results were published, claiming an improvement in 30% of patients. Hauntingly, demand was to be of paramount importance. A cause of treatment required 2gm of taxol, supplied by 60lb of bark or three mature trees. Taxol was also proving successful with breast cancer. To support the demand, nearly ¾ million trees would be required each year and this was unimaginable. Synthesising taxol from scratch was still proving impossible as well.

In 1991, a chemist Robert Holton from the Florida State University patented a method he had discovered to synthetically create taxol’s large side chain. Obtaining financial support from Bristol-Myers, he succeeded in creating taxol using a molecule found in the needles of common species of yew together with his synthesised molecule. Bristol-Myers formed a semi-synthetic version of taxol called Paclitaxel and made it available to the public in 1995. Taxol is now an official cancer drug as recognised by the US Food and Drug Administration. The European company Rhone-Poulenc Rorer manufactures an almost identical drug ‘Taxotere’.