Weekly injection replaces frequent pills for Parkinson's disease

A new weekly injectable drug could revolutionise the lives of more than eight million people with Parkinson's disease, potentially replacing the need to take multiple pills every day.

Scientists at the University of South Australia (UniSA) have developed a sustained-release injectable formulation that delivers a steady supply of levodopa and carbidopa – two key drugs in the treatment of Parkinson’s – for a full week. The biodegradable formulation is injected under the skin or into muscle tissue, where it gradually releases the drugs over seven days.

The study, titled “Development of an in-situ forming implant system for levodopa and carbidopa for the treatment of Parkinson's disease,” is published in the journal Drug Delivery and Translational Research.

Frequent medication administration is a significant burden, especially for elderly patients or those with difficulty swallowing, resulting in fluctuations in blood drug levels, more side effects, and decreased treatment effectiveness.

Lead researcher Professor Sanjay Garg, from UniSA's Centre for Pharmaceutical Innovation, says the newly developed injectable drug could significantly improve treatment outcomes and patient adherence.

"Our goal was to create a formulation that simplifies treatment, improves compliance and provides a stable therapeutic level of the drug. This weekly injection could be a real breakthrough in the treatment of Parkinson's disease," says Professor Garg.

"Levodopa remains the gold standard therapy for Parkinson's, but its short half-life means it must be taken several times a day."

UniSA PhD student Deepa Nakmode adds that the in-situ implant is designed to release levodopa and carbidopa evenly over a period of one week, maintaining stable plasma drug levels and reducing the risks associated with fluctuations in concentration.

“After many years of dedicated research, it is incredibly rewarding to see our innovation in long-acting injections for Parkinson’s disease reach this stage. An Australian patent has already been applied for on our development,” says Nakmode.

The injectable gel combines FDA-approved biodegradable PLGA polymer with Eudragit L-100, a pH-sensitive polymer, to provide controlled and sustained drug release.

Extensive laboratory testing has confirmed the effectiveness and safety of the system:

• More than 90% of the levodopa dose and more than 81% of the carbidopa dose were released within seven days.

• The implant was more than 80% degraded within a week and showed no significant toxicity in cell viability tests.

• The formula can be injected using a fine 22G needle, minimizing discomfort and eliminating the need for surgical implant placement.

"The implications of this study are significant," says Professor Garg. "Reducing the frequency of drug administration from several times a day to one weekly injection is a major step forward in Parkinson's therapy. We are not just improving drug delivery, we are improving patients' lives."

Professor Garg notes that the technology could be adapted for other chronic diseases such as cancer, diabetes, neurodegenerative disorders, pain relief and chronic infections that require long-term drug administration.

The system can be configured to release drugs over several days or several weeks depending on therapeutic needs.

UniSA scientists hope to begin clinical trials in the near future and are considering commercialising the technology.

Parkinson's disease is the second most common neurological disorder, affecting more than 8.5 million people worldwide. There is currently no cure for the disease, and the symptoms - tremors, rigidity and slowness of movement - are controlled with oral medications taken several times a day.