Researchers push big pharma to rethink asthma treatment

Researchers at the Telethon Institute for Child Health Research in Perth are hoping to persuade big pharma to test therapeutics targeting specific inflammatory response effector molecules in young children at risk of developing persistent asthma.

If they succeed, the scientists, led by Prof Patrick Holt and Prof Peter Sly, say they may be able to prevent the chronic disease from developing.

Holt and Sly are lead authors on a recent Nature Immunology paper outlining the arguments in favour of using specific anti-inflammatory drugs to halt the development of asthma in children.

"There are a range of drugs which have a very strong likelihood of being able to halt progression from early-stage to late-stage disease," Holt said.

At the heart of the effort is a substantial body of research performed by Holt, Sly and their colleagues both in Australia and overseas looking at the pathogenesis of the disease -- the events that occur in babies and young children to trigger inflammation of the airways and subsequent permanent changes to the airways causing the chronic hyper-responsiveness characteristic of chronic persistent asthma -- in children.

They and others have found that a combination of lower respiratory infections in early childhood, plus sensitisation to inhalant allergens substantially increase the risk of developing persistent asthma. Timing is also an issue, and researchers suspect that inflammation during the critical period of lung and airway development in early childhood plays a major role, causing permanent structural changes that lead to persistent wheezing.

While a number of drugs have been developed that target specific allergy-associated inflammatory processes, in particular the T helper Type 2 (Th2) mediated inflammatory mechanisms, very few of them have shown widespread success in the clinic. Holt believes this is because the trials of these drugs have been restricted to adults with established asthma, and Th2-associated inflammation, which is responsible for the initiation of asthma, no longer plays the dominant role in adults in maintaining chronic asthma. Most symptoms in these subjects are due to chronic airway hyper-responsiveness, which has developed as a result of a long history of Th2-mediated damage to airway tissues -- this makes the airways susceptible to an ever-widening range of triggers which spreads well beyond environmental allergens.

But because big pharma follows the established drug testing paradigm of conducting clinical trials in adults first, and then in progressively younger patient groups once efficacy in the older population is clear, many of the drugs which have shown limited efficacy in adults are destined to be shelved, and not tested at all in children, despite recent moves by the US FDA to encourage more thorough testing of drugs in different age groups of patients.

"There is a queue of paediatricians around the world anxious to take part in clinical trials with the new generation Th2 antagonists," Holt said. "If these drugs prove to have efficacy in halting disease progression in early asthma they are potential blockbusters -- there is a lot in it for drug companies if we can get them to understand the full potential of some of the drugs they already have."

Blockbusters indeed. Asthma costs countries like Australia a tremendous amount of money, and the number of children developing the disease has been increasing over recent decades. Around 15 per cent of Australian children have persistent asthma by age 12, according to Holt.

"If we could halt even 20 per cent of children at risk from developing asthma, we could save the Australian economy somewhere in the order of $100 million per year," he said.

Holt says he knows of at least three, probably more, drugs which target the Th2-mediated inflammation cascade, which would be good candidates for early intervention efforts in children. He and Sly, along with a group of leading paediatric asthma researchers in the US and Europe, are currently in discussions with a major pharmaceutical company about testing an experimental drug for early intervention in children at risk of developing asthma. Another international trial in the works will involve prevention of allergy in young children as a strategy to prevent asthma from taking hold.

"There are a whole range of possibilities out there that are not being explored at the moment -- it's a potential goldmine for industry and presents a major opportunity for novel research in academia," Holt said.

But there are also a number of hurdles to get over. For a start, no one knows how big the window for intervention actually is, although Holt believes that there is probably a decreasing window of opportunity as children progress from infancy through childhood and beyond. Eventually, however, it is likely that researchers and clinicians will be able to accurately identify the early stages of the disease and associated biomarkers, which should allow intervention in children at the greatest risk. A similar approach has been pioneered by diabetes researchers, including WEHI's Len Harrison, in identifying children at risk of developing type 1 diabetes.

In any case, Holt believes that the big pharma companies will come around to his way of thinking eventually. "We have so much support for this from the opinion leaders in the field," he said.