With threats of Y2K-provoked technology meltdowns and mass terrorist attacks behind us, it's time to focus on the more positive aspects of the new millennium. Medicine in the 21st century sounds fabulous. The distant future brings promise of impeccably precise magic bullets, individually tailored gene therapies, and other breakthrough treatments that will zero in on diseased tissue, correct DNA gone wrong, and, finally, cure the incurable. But what's in store in the near future?
Speaking at a recent Monument Medical Sciences Fund telephone briefing, industry analyst Alexander Cheung predicted the arrival of novel cardiovascular drugs that target stenosis in patients whose arteries have reclogged following angioplasty. In the cancer arena, angiogenesis inhibitors—known to cut off blood supply to tumors—remain in the limelight of investigation, noted Cheung, a senior v.p. and senior portfolio manager at Monument Advisors, Ltd. He also indicated that pharmaceutical development will focus more on age-related conditions such as Parkinson's and Alzheimer's disease, which are expected to rise dramatically because of the aging baby boomers.
Cheung disclosed that 200 agents are now in phase III trials and another 200 drugs are awaiting final Food & Drug Administration review. While only time will tell which of these products will show up on pharmacy shelves first, several appear quite close to approval and might even make their market entrance this year. These drug candidates are intended to treat a variety of conditions, including depression, irritable bowel syndrome, Alzheimer's disease, colorectal cancer, and migraine headaches.
One of these products has risen from the extensive research done on the decade's most talked about neurotransmitter—serotonin. From depression to nausea, this chemical—or the lack of it—has been implicated in just about every ailment imaginable. Now researchers have started tinkering with it when treating patients with irritable bowel syndrome (IBS). Several manufacturers are developing compounds that tar-get and modulate certain serotonin receptor subtypes, which are known to be present throughout the gastrointestinal tract and are believed to play a role in GI motility and pain perception.
Lotronex (alosetron HCl), one promising agent from Glaxo Wellcome, was recently approved by the FDA for the treatment of IBS in women. A selective 5-HT3 antagonist, alosetron has been shown in phase III trials to provide relief from IBS-related pain and discomfort, decrease urgency, and reduce stool frequency in nonconstipated females with IBS. The improvements in bowel function were observed after one week of treatment and continued throughout the 12-week treatment period. Therapeutic effects of alosetron rapidly dissipated one week after its discontinuation. Most commonly reported side effects were constipation, headache, nausea, and GI pain and discomfort. Perhaps alosetron will offer the 20 million Americans who suffer from IBS an option besides the currently used anticholinergics and antispasmodics.
In the area of depression, norepinephrine (NE) appears to be back in the hot seat. For a while, researchers seemed to focus almost exclusively on selective serotonin reuptake inhibitors (SSRIs), which placed serotonin in the spotlight and left NE completely out of the picture. Now, research is suggesting that the role of NE in the treatment of depression is far more important than previously considered. NE depletion has been demonstrated to affect the most core symptoms of depression, including lack of energy and interest and loss of motivation. After all, the neurotransmitter was the original amine targeted by some of the first anti-depressants introduced. It actually held quite an esteemed position in the treatment of the melancholy condition before the advent of SSRIs caused it to dwindle in popularity.
In an effort to place more focus on NE, Pharmacia & Upjohn and Janssen Pharmaceutica have entered into an agreement to copromote Vestra (reboxetine mesylate), a selective NE reuptake inhibitor. Already marketed by Pharmacia & Upjohn outside the United States under the trade name Edronax, reboxetine has been deemed approvable by the FDA, according to a spokesman from Pharmacia & Upjohn. Data from clinical trials indicate that the agent is similar in efficacy and in tolerability to a currently available SSRI—but with one advantage.
Patients who received reboxetine were more likely to achieve a normal Social Adaptation Self-evaluation Scale (SASS) score than were those who were given the SSRI. Commonly reported side effects with reboxetine include dry mouth, insomnia, constipation, hypotension, impotence, and increased sweating.
Therapy for Alzheimer's
At the forefront of research into Alzheimer's disease (AD) are numerous novel investigational agents that are being developed to target the various pathological processes that lead to the degenerative neurologic disorder. One promising aspect of pharmaceutical intervention is inhibition of beta-amyloid protein—a major component of the toxic amyloid plaques, which are deposited into the brains of Alzheimer's patients. Cheung talked about the discovery of a gene that has been "highly implicated in the growth of beta-amyloid proteins." This certainly opens the door for possible AD gene therapy. A study published in Nature hypothesized that vaccination against amyloid plaques may be applicable.
The good news is that all this intense research might eventually lead to therapies that could halt the disease process. The bad news is that these treatments don't appear to be anywhere close to approval. What is coming down the pipeline are two acetylcholinesterase inhibitors that, like AD drugs currently on the market, inhibit the breakdown of the critical neurotransmitter acetylcholine.
Exelon (rivastigmine), one such agent under development by Novartis, has held an approvable status since May of 1999, according to one source. The noncompetitive acetylcholinesterase inhibitor has been shown in studies to improve the functional ability of patients with mild to moderately severe AD, as indicated by assessments in activities of daily living, cognitive function, and behavior. Rivastigmine appears to have greater central than peripheral activity, which may result in fewer peripheral adverse events, compared with current acetylcholinesterase inhibitors. Because the drug does not appear to be metabolized by cytochrome P-450 enzymes, it may have fewer relevant drug interactions. To date, the drug has been cleared for marketing in over 40 countries, including all member states of the European Union.
Reminyl (galantamine), the other acetylcholinesterase inhibitor under development by Janssen Pharmaceutica, appears to act on the brain's nicotinic receptors, in addition to exerting long-acting, reversible, and competitive inhibition of cholinesterase activity. Scientists at Janssen Research Foundation in Belgium believe that nicotinic modulation could lead to a release of more acetylcholine and may also be associated with the development of fewer amyloid plaques. Data from phase III trials indicate that galantamine can significantly improve scores on a widely used assessment scale that measures memory and learning ability in AD patients. Commonly reported adverse effects included nausea, vomiting, and other GI complications that are normally seen with cholinergic agents. A New Drug Application (NDA) for the product was filed in September 1999.
New for migraine headaches
In the treatment of migraine headaches, the serotonin-modulating triptans continue to be at the center of attention—with two possible new additions. Vanguard Medica Group and Elan Corp. submitted an NDA for their 5-HT1B/1D receptor agonist Miguard (frovatriptan 2.5-mg tablets) in January 1999 for the acute treatment of migraine. Summarized clinical trial data indicate that oral doses of 2.5 mg to 40 mg have produced response rates after two hours in 40% to 45% of treated patients. Headache recurrence at 24 hours is seen in about 12% of patients. Comparisons with other triptans are lacking.
Pfizer was recently granted an approvable letter from the FDA for its 5-HT1D receptor agonist Relpax (eletriptan) for the treatment of migraine. The agent carries the advantage of high lipophilicity, which may enable rapid absorption. Additionally, eletriptan does not appear to interact with propranolol—a downside of other triptans. Doses of 40 mg to 80 mg have resulted in headache relief at two hours in approximately two-thirds of treated patients. Eletriptan has been shown in some studies to be superior to placebo and oral sumatriptan in relieving other symptoms of migraine, including nausea, photophobia, and phonophobia.
Focus on colorectal cancer
In the oncology arena, colorectal cancer has been the recent focus of research and development. Bristol-Myers Squibb Co. recently completed its regulatory filing with the FDA for marketing approval of Orzel (UFT plus leucovorin calcium), the first oral therapy for metastatic colorectal cancer. UFT (tegafur) is considered to be a prodrug of 5-fluorouracil (5-FU), which, after being slowly metabolized by hepatic enzymes, results in slow and continuous release of the active moiety into systemic circulation. Unlike 5-FU—which is known to be erratically absorbed from the GI tract—UFT is rapidly and reliably absorbed after oral administration, thus, enabling it to be evaluated as an oral alternative to intravenous 5-FU. Leucovorin, the folinic acid component of Orzel, is used to diminish the toxicity of 5-FU.
An NDA for Eloxatine (oxaliplatin) for the first-line treatment of metastatic colorectal cancer in combination with 5-FU-based therapies was submitted and accepted by the FDA. The intravenously administered agent is a cisplatin analog that has been shown in trials to have relatively high response rates in untreated patients and in those previously treated with 5-fluorouracil for the aforementioned malignancy. Used as first-line therapy, a combination consisting of oxaliplatin and 5-FU plus leucovorin produced objective response rates of 49% to 62% in metastatic disease.
As second-line therapy in patients who were given previous 5-FU regimens, the combo resulted in response rates of 29% to 55%. Nausea, vomiting, and peripheral sensory neuropathy are among the commonly reported side effects. Eloxatine, already approved in the European Union, was developed by Sanofi-Synthelabo of France.