The world desperately needs painkillers that aren't addictive or heavy with damaging side effects. A strong candidate has been found in the venom of a tarantula known as a Chinese bird spider, and fortunately no further tarantula involvement is required.
Venoms are exceptionally chemically complex, usually involving hundreds of different molecules. With so many animals having adopted them for hunting or defense, they provide a biochemical bonanza, including one of the most prescribed drugs in the world captopril.
Dr Christina Schroeder of the University of Queensland is hunting for a replacement for opioids such as fentanyl and oxycontin in treating chronic pains like back pain. She told IFLScience she has a particular interest in neuropathic pain, which can be such a severe side effect of chemotherapy some people discontinue treatment.
“Although opioids are effective in producing pain relief, they come with unwanted side-effects like nausea, constipation and the risk of addiction, placing a huge burden on society,” Schroeder said in a statement.
Having identified the 1.7 sodium channel as an important chronic pain relief target, Schroeder went looking for molecules to fit. She told IFLScience another team had already identified Huwentoxin-IV in bird spider venom as a candidate.
Schroeder set about modifying Huwentoxin-IV to make it more specific, seeking something that would block the channel she needed but not affect the body's eight other sodium channels, minimizing the risk of side effects.
The process proved particularly complex. “We normally talk about receptors and molecules as a lock and key,” Schroeder told IFLScience, “But in this case we had to look at the whole frame around the lock.” The doorframe in this analogy is the lipid membrane that surrounds the channel, which influences molecular binding.
In the Journal of Biological Chemistry, Schroeder has announced that the modified Huwentoxin-IV proved successful at blocking pain in mouse trials without obvious side-effects. It's not clear why the spiders target this particular channel in their venom, but Schroeder says the diversity of molecules they inject hits their prey from many angles at once, minimizing capacity to run away or fight back.
Schroeder assured IFLScience that even if a drug from her work eventually hits the market, there will be no spider farms to terrorize our dreams. The molecule will either be synthesized inorganically or produced by genetically modified bacteria. Indeed, Schroeder added, “I don't much like spiders. I have a postdoc who enjoys finding animals and milking them,” allowing her to concentrate on the chemistry undisturbed.
More preclinical research is required before studies can begin on humans, so a product is probably 15 years away. “People are starting to understand how hard it is to get a drug on the market quickly now we need a vaccine so much,” she said.