Thursday, March 13, 2008

Liposome Formulations

Liposomes were first discovered in the mid 1960's and the first liposomal pharmaceutical product received FDA approval in the mid-1990's. Currently there are at least 6 liposomal pharmaceutical products currently marketed with many more in various stages of clinical trials. The currently marketed products are all for intravenous dosing and used in cancer chemotherapies as well as advanced fungal infections. We have heard reports that there are liposomal pharmaceuticals which do not claim to be liposomes (probably to avoid patent infringement issues) so the exact number of liposomal products that have been approved by the FDA is unclear.

While many companies are still pursuing liposomal anti-cancer agents to be used intravenously, a few companies are pursuing liposome delivery by inhalation. The indications include lung cancer chemotherapies which have the advantage of focusing the toxic chemotherapeutic drug in the lung at the site of the tumor. This helps avoid the systemic or whole body toxicity which is usually the reason that the chemotherapy must be halted before the cancer is fully eradicated. There is also an inhaled liposomal lung cancer vaccine and inhaled liposomal antibiotics all of which are showing great promise in clinical trials. Inhalation therapy device (or nebulizer) companies have played a key role in the development of the inhaled liposome drugs by designing devices which function with the appropriate parameters for a liposome product. The fact that these older, well-established companies have devoted some of their significant development resources toward devices which are liposome-friendly suggests that the field of inhalation medicine takes the liposomal delivery of drugs via inhalation very seriously for the future.

Remember that we are now talking about liposomal drugs which have been or are being extensively tested for efficacy as well as safety according to the strictest FDA guidelines. A few years ago the FDA actually put a new department in place to evaluate liposomes and other particulate drug delivery systems which means that they also take the future of liposomal drugs very seriously. Note that liposomes are the only particulate delivery system that have successfully made it to the market to date. Gold, carbon, carbohydrate and protein nanoparticles among others are constantly being reported as promising delivery systems, but have yet to become commercially available as pharmaceuticals unlike liposomes.

In future posts we will expound on the numerous liposome products available over the counter. For now, make sure that the liposomal information that you see on the internet, TV, etc. is backed up by scientific data in peer-reviewed journals or by experienced liposome scientists.