21 September 2017

Osteoarthritis ‘breakthrough’ overblown: expert

Drugs Rheumatology

Despite being hailed as a “breakthrough”, experts are cautioning the public not to get too excited about early findings on a new osteoarthritis drug.

Australian researchers recently touted the benefits of the 60-year-old drug pentosane polysulfate sodium as potentially being able to reverse some symptoms of advanced osteoarthritis. They pointed to the case of an older woman whose pain rating went from an eight out of 10 down to a four out of 10 after just two weeks of the therapy.

Before the twice weekly injections, the 70-year-old was scheduled for a knee replacement and had bone marrow oedema lesions on MRI. But after two weeks of injections, there was no evidence of the lesions, and both joint swelling and knee movement had improved, according to the biotech company Paradigm Biopharma.

She has since been taken off the knee replacement waiting list.

The researchers said, this case study, published in BMC Musculoskeletal Disorders, was supported by trials on another 30 patients who had experienced similar benefits.

Among the other participants, 70% had a significant reduction in pain and another 15% had initial relief, Paradigm Biopharma Chief Executive Paul Rennie told The Medical Republic.

The company was now recruiting patients for their 18-month, phase-two, randomised controlled trials across several Australian states, and if successful, it would apply for TGA approval and negotiate with the government for PBS approval for this indication, Mr Rennie said.

“A ballpark figure the government or health Insurers will pay will be in thousands of dollars for a course of the drug which will involve 12 injections over six weeks,” he said. However, osteoarthritis leads to around 19,000 hip replacements and 25,000 knee replacements in Australia each year, which each cost the healthcare system around half a billion dollars.

Adelaide rheumatologist Associate Professor Susanna Proudman said the drug showed some promise and had reasonable science behind it, but the excitement in the media was premature.

“Osteoarthritis is one of the major causes of disability, certainly musculoskeletal disability in our community, and it’s certainly one that we’re less able to treat effectively,” Professor Proudman said. “So the concept of a disease-modifying anti-osteoarthritis therapy is the holy grail.”

However, the Royal Adelaide Hospital rheumatologist said it was difficult to draw conclusions from such small, pilot studies which were not powered to demonstrate efficacy.

“We know that the placebo effect in the treatment of osteoarthritis is very large,” she said, explaining that patients in studies sometimes had “dramatic responses” to paracetamol, despite the overall analysis finding it was ineffective across the group.

While reductions in pain of eight out of 10 to zero out of 10 is greater than the placebo effect, which can be as much as four out of 10, “a few cases of excellent response amounts to little more than anecdote”, she said.

BMC Musculoskelet Disord; online 12 Sept