The Food and Drug Administration doesn't make a habit of giving drugs that once showed serious side effects another shot at approval, but it did so this past Monday. The case in point is not just one medication, but a class of drugs meant to manage the chronic pain of arthritis and other diseases.
After a hearing at which drug company representatives argued on behalf of their prospective treatments, an FDA drug advisory panel unanimously voted in favor of recommending that the drugs called anti-nerve growth factors be allowed to continue testing, despite problems encountered two years ago. This was a clear win for Pfizer
Pfizer's tanezumab seemed like a winner back in 2010, until researchers found that an inordinate number of subjects taking the drug suffered accelerated joint deterioration, sometimes to the point of needing joint replacement. That trial was immediately halted, and others being conducted on similar drugs by other pharmaceutical companies were stopped by the end of the year. AstraZeneca, seeing which way the wind was blowing, elected to stop testing its formulation, MEDI578, as well.
Why are big pharma companies going to bat for these drugs?
It is uncommon for drugs that have been cast aside due to safety concerns to be reactivated in hopes of gaining final FDA approval. But there are a few things at stake here, which may explain the drug manufacturers' persistence. One of those things is money, boatloads of it.
According to GlobalData, the pain management market is burgeoning, which should be extremely lucrative for those companies that can provide appropriate treatments. The value of the osteoarthritis therapy market alone was estimated at $4.4 billion in 2010, with expected growth to $5.9 billion in 2018. Although the focus for drugs like tanezumab and its ilk have been for the OA market, the drugs were actually being tested on several kinds of chronic pain, such as that from diabetic neuropathy, back conditions, and cancer. As a matter of fact, Johnson & Johnson has been using its entry, fulranumab, in research on pain in cancer patients. When you consider the entire spectrum of uses for anti-NGFs, the new market estimate climbs to around $11 billion per year.
Money is always a great motivator, but there's something else about these drugs, too. They work really, really well. As it turns out, perhaps too well.
Although there is no consensus on this issue, some experts believe the joint problems experienced by some participants in the 2010 study could have been caused by overuse. Some surmise that, because the patients taking the drug at higher doses could not feel the warning pangs of pain in their arthritic joints, they basically wore them out. This makes sense, for several reasons.
The first is the nature of the drugs themselves. These drugs block nerve growth factor, which is essential for feeling pain. Osteoarthritis, by its nature, involves the breakdown of cartilage between bones, which causes painful bone-to-bone scraping that can also cause joints to fail over time. This can happen more quickly if the patient can't feel the warning signals. In Pfizer's study, the drug was injected either locally or intravenously, and the effects could last up to eight weeks. The degeneration problems occurred more often in the high-dose groups.
Drug manufacturers make their case
The drug companies argued that the drugs merited reconsideration because of the dearth of pain management drugs available for those with osteoarthritis or other chronic pain. The types of drugs most commonly used are non-steroidal, anti-inflammatory medications or narcotic pain relievers, both of which have substantive side effects and risks of their own, which appeared to be influential on the panel's decision.
The argument that currently available drugs are inadequate was true enough, but the drugmakers had another bit of information that seemed relevant: Those patients who experienced bone degeneration were taking the anti-NGFs in conjunction with other drugs, usually NSAIDs. This fact was presented as causative of the joint problems, which the drug companies felt would not have occurred otherwise. While it is unclear why patients were allowed to use other drugs for pain during the study, the outcome could certainly be the enhanced masking of pain, with the resultant joint damage.
New trials, lower doses may bring success
Pfizer suggested that new trials of tanezumab should incorporate restrictions not present in the original studies, such as lower doses of the drug, disallowing other drugs to be used in tandem, and removing patients from the trial if they don't respond quickly.
If the new trials pan out, chances are very good that Pfizer will be the first to have its product approved and marketed, followed by Regeneron, whose drug was in phase 2 trials when trials were halted. If the dosage can be managed and patients monitored for any changes in joint function, these drugs could change the landscape of pain management for millions of people, as well as make billions for their manufacturers.
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