orphan diseases are defined as diseases with fewer than 200,000 patients. In total, however, across the nearly 7,000 orphan diseases, 30 million people in the US, or about 10% of the population, are affected by an orphan disease. The pemphigus and pemphigoid (P/P) diseases are considered “ultra-orphan” diseases because they are extremely rare. It is estimated there are only about 50,000 new P/P cases each year worldwide, with only a few thousand of those being in the US.
Rare diseases tend to be more complex than common diseases, meaning that there are a number of factors that combine to cause disease. In the case of P/P, while there seem to be genetic risk factors, how these contribute, singularly or in combination, and to what extent the environment (like diet and other conditions that are present) also contributes is not well understood.
Somewhat fortuitously, complex diseases represent the next great frontier for drug developers. Having tapped into the ‘simpler’ diseases, making great strides in treatment of conditions like high cholesterol, these ‘low-hanging fruit’, as drug-makers like to call them, have been consumed. It is truly a time of paradigm-shifting mentality among drug makers.
That said, the costs of developing new medicines is extremely high, so companies must make their choices wisely. If we were to calculate the amount that pharmaceutical and biotechnology companies spend on research and development yearly and compare that to the number of drugs that are approved for clinical use by the FDA each year, the cost per successful drug is a staggering $1.2 billion. It’s not difficult to imagine, then, why companies aimed at developing new drugs are most interested in those that can recoup these huge costs — for instance, by developing drugs for very common conditions and risk factors such as diabetes and high cholesterol. As well, given the complex nature of rare diseases, they are not necessarily among the ‘low-hanging fruit’ that some diseases represent.
To incentivize companies to prioritize new drugs for rare conditions, they may apply for orphan drug status through the FDA, a result of passage of the Orphan Drug Act (ODA) of 1983. With this status, a drug receives seven years of market exclusivity. Market exclusivity is particularly appealing to companies developing drugs because the seven-year exclusivity period differs from laws applicable to other drugs in that it does not begin until the drug is approved by the FDA approval.
The ODA is considered a resounding success. Since its inception, there have been more than 400 medicines approved for a total of 447 orphan diseases. As well, there are hundreds of new medicines in development, including an impressive list available in the PhRMA 2013 report (phrma.org/sites/default/files/pdf/Rare_Diseases_2013.pdf).
While not all of the 452 orphan drugs in development will be approved for patient use, this is certainly a lot of activity. A search of the list included within the PhRMA report, as well as a search of clinicaltrials.gov (that lists all clinical trials in progress), shows a handful of drugs in testing for conditions related to or directed at P/P.
There are 18 new orphan drugs in phase I-III trials (there are three phases of clinical trials and drugs must pass all of them, indicating reasonable levels of safety and meaningful efficacy-effectiveness in treating the condition) that are indicated for autoimmune disorders.
New drugs are not the only source of treatment for disease. Another source is to use an existing drug, developed for another condition, for a different indication. Such is the case with Rituxan® (rituximab), which was originally developed for Non-Hodgkin’s lymphoma. In that disease, B cells of the immune system bearing a marker called CD20 (thus the name CD20+ B cells) have gone awry.
Since P/P shares this hallmark, Rituxan® has been successfully used ‘off-label’ for P/P. It is an antibody-based drug, which requires it to be injected into the patient. In general, any drug that acts as a suppressor of the immune system (immunosuppressant) is a potential candidate for treating a range of auto-immune conditions, including P/P. CellCept® (mycophenolate mofetil), another immune system suppressor that was developed for transplant patients to help prevent the body’s rejection of the ‘foreign’ organ, has recently been approved for use in P/P.
Besides the high cost of developing new drugs, companies that seek treatments for orphan diseases face difficulty in finding enough patients to participate. Indeed, patients tend to be dispersed geographically and may include small children. Physicians and patients who are interested in participating in trials or gaining more information should visit clinicaltrials.org.
Within the P/P community, the IPPF is also a great resource for learning about clinical trials. Members of our medical advisory board serve as investigators on trials and being in our patient database could lead to a company reaching out to you about participating in a trial.
For instance, among the new drugs aimed at treating P/P, drug-maker Novartis is studying VAY736, an antibody-based drug aimed at another B cell marker called BAFF-R. The study is in a very early stage and should be recruiting patients soon.
The time is ripe for development of new drugs for complex orphan diseases. The surge in new medicines in the first 30 years since the ODA should accelerate as less ‘low-hanging fruit’ exist for companies developing new drugs.