The preliminary findings suggest the compound, called squalamine, also suppresses the toxic products associated with the process, researchers at Cambridge University have found.
Academics stressed further research is needed, and that findings are based on cell cultures developed in the lab and testing in nematode worms.
But the compound has been used in clinical trials for cancer and eye conditions in America, and a trial in Parkinson's Disease patients is now being planned by one of the researchers involved in the study.
The study was led by academics from the Centre for Misfolding Diseases based at Cambridge University and Georgetown University and the National Institutes of Health in the United States.
It is not yet clear whether squalamine can reach the specific regions of the brain where the main molecular processes determining Parkinson's Disease take place, or what form any resulting drug might take.
Squalamine is a steroid which was discovered in the 1990s in dogfish sharks, although the form now used by scientists is a safer, synthetic analogue.
To date, it has been extensively investigated as a potential anti-infective and anti-cancer therapy.
In the new study, researchers found squalamine inhibits the early formation of toxic aggregates of the protein alpha-synuclein - a process thought to start a chain reaction of molecular events eventually leading to Parkinson's Disease - and can suppress the toxicity of these poisonous particles.
Co-author Michele Vendruscolo, of Cambridge University, said: "This is an encouraging step forward in our efforts to discover potential drugs against Parkinson's Disease."
Researchers said it would be interesting to investigate the efficacy of squalamine as a means to alleviate certain symptoms, including severe constipation and symptoms concerning the peripheral nervous system.
The findings are published in Proceedings Of The National Academy Of Sciences (PNAS).
